<XBRL>
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<!-- Compliance Xpressware Instance Document http://www.compliancexpressware.com/  -->
<!-- Version: 1.0.0 --><!-- Creation date:21:51:31 GMT-0800 -->
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<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" >
  <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2008-03-31.xsd#negated" roleURI="http://xbrl.us/us-gaap/role/label/negated"/>
  <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2008-03-31.xsd#negatedTotal" roleURI="http://xbrl.us/us-gaap/role/label/negatedTotal"/>
  <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2008-03-31.xsd#negatedPeriodStart" roleURI="http://xbrl.us/us-gaap/role/label/negatedPeriodStart"/>
  <link:roleRef xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/role/negated-2008-03-31.xsd#negatedPeriodEnd" roleURI="http://xbrl.us/us-gaap/role/label/negatedPeriodEnd"/>
  <link:labelLink xlink:type="extended" xlink:role="http://www.xbrl.org/2003/role/link">
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_DocumentandEntityInformationAbstract" xlink:label="DocumentandEntityInformationAbstract" xlink:title="DocumentandEntityInformationAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_DocumentandEntityInformationAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_DocumentandEntityInformationAbstract" xml:lang="en-US" id="label_vsta_DocumentandEntityInformationAbstract_en-US">Document, Entity Information</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DocumentandEntityInformationAbstract" xlink:to="label_vsta_DocumentandEntityInformationAbstract" xlink:title="label: DocumentandEntityInformationAbstract to label_vsta_DocumentandEntityInformationAbstract" use="optional" order="1"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntitiesTable" xlink:label="EntitiesTable" xlink:title="EntitiesTable"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntitiesTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntitiesTable" xml:lang="en-US" id="label_dei_EntitiesTable_en-US">Statement Entities [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntitiesTable" xlink:to="label_dei_EntitiesTable" xlink:title="label: EntitiesTable to label_dei_EntitiesTable" use="optional" order="2"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_LegalEntityAxis" xlink:label="LegalEntityAxis" xlink:title="LegalEntityAxis"/>
    <link:label xlink:type="resource" xlink:label="label_dei_LegalEntityAxis" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_LegalEntityAxis" xml:lang="en-US" id="label_dei_LegalEntityAxis_en-US">Legal Entity [Axis]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LegalEntityAxis" xlink:to="label_dei_LegalEntityAxis" xlink:title="label: LegalEntityAxis to label_dei_LegalEntityAxis" use="optional" order="3"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityDomain" xlink:label="EntityDomain" xlink:title="EntityDomain"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityDomain" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityDomain" xml:lang="en-US" id="label_dei_EntityDomain_en-US">Entity [Domain]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityDomain" xlink:to="label_dei_EntityDomain" xlink:title="label: EntityDomain to label_dei_EntityDomain" use="optional" order="4"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_DocumentInformationLineItems" xlink:label="DocumentInformationLineItems" xlink:title="DocumentInformationLineItems"/>
    <link:label xlink:type="resource" xlink:label="label_dei_DocumentInformationLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_DocumentInformationLineItems" xml:lang="en-US" id="label_dei_DocumentInformationLineItems_en-US">Document and Entity Information</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DocumentInformationLineItems" xlink:to="label_dei_DocumentInformationLineItems" xlink:title="label: DocumentInformationLineItems to label_dei_DocumentInformationLineItems" use="optional" order="6"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_DocumentType" xlink:label="DocumentType" xlink:title="DocumentType"/>
    <link:label xlink:type="resource" xlink:label="label_dei_DocumentType" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_DocumentType" xml:lang="en-US" id="label_dei_DocumentType_en-US">Document Type</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DocumentType" xlink:to="label_dei_DocumentType" xlink:title="label: DocumentType to label_dei_DocumentType" use="optional" order="7"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_AmendmentFlag" xlink:label="AmendmentFlag" xlink:title="AmendmentFlag"/>
    <link:label xlink:type="resource" xlink:label="label_dei_AmendmentFlag" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_AmendmentFlag" xml:lang="en-US" id="label_dei_AmendmentFlag_en-US">Amendment Flag</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AmendmentFlag" xlink:to="label_dei_AmendmentFlag" xlink:title="label: AmendmentFlag to label_dei_AmendmentFlag" use="optional" order="8"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_AmendmentDescription" xlink:label="AmendmentDescription" xlink:title="AmendmentDescription"/>
    <link:label xlink:type="resource" xlink:label="label_dei_AmendmentDescription" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_AmendmentDescription" xml:lang="en-US" id="label_dei_AmendmentDescription_en-US">Amendment Description</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AmendmentDescription" xlink:to="label_dei_AmendmentDescription" xlink:title="label: AmendmentDescription to label_dei_AmendmentDescription" use="optional" order="9"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="DocumentPeriodEndDate" xlink:title="DocumentPeriodEndDate"/>
    <link:label xlink:type="resource" xlink:label="label_dei_DocumentPeriodEndDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_DocumentPeriodEndDate" xml:lang="en-US" id="label_dei_DocumentPeriodEndDate_en-US">Document Period End Date</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DocumentPeriodEndDate" xlink:to="label_dei_DocumentPeriodEndDate" xlink:title="label: DocumentPeriodEndDate to label_dei_DocumentPeriodEndDate" use="optional" order="10"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_TradingSymbol" xlink:label="TradingSymbol" xlink:title="TradingSymbol"/>
    <link:label xlink:type="resource" xlink:label="label_dei_TradingSymbol" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_TradingSymbol" xml:lang="en-US" id="label_dei_TradingSymbol_en-US">Trading Symbol</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="TradingSymbol" xlink:to="label_dei_TradingSymbol" xlink:title="label: TradingSymbol to label_dei_TradingSymbol" use="optional" order="11"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityRegistrantName" xlink:label="EntityRegistrantName" xlink:title="EntityRegistrantName"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityRegistrantName" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityRegistrantName" xml:lang="en-US" id="label_dei_EntityRegistrantName_en-US">Entity Registrant Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityRegistrantName" xlink:to="label_dei_EntityRegistrantName" xlink:title="label: EntityRegistrantName to label_dei_EntityRegistrantName" use="optional" order="12"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="EntityCentralIndexKey" xlink:title="EntityCentralIndexKey"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityCentralIndexKey" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityCentralIndexKey" xml:lang="en-US" id="label_dei_EntityCentralIndexKey_en-US">Entity Central Index Key</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityCentralIndexKey" xlink:to="label_dei_EntityCentralIndexKey" xlink:title="label: EntityCentralIndexKey to label_dei_EntityCentralIndexKey" use="optional" order="13"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="CurrentFiscalYearEndDate" xlink:title="CurrentFiscalYearEndDate"/>
    <link:label xlink:type="resource" xlink:label="label_dei_CurrentFiscalYearEndDate" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_CurrentFiscalYearEndDate" xml:lang="en-US" id="label_dei_CurrentFiscalYearEndDate_en-US">Current Fiscal Year End Date</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CurrentFiscalYearEndDate" xlink:to="label_dei_CurrentFiscalYearEndDate" xlink:title="label: CurrentFiscalYearEndDate to label_dei_CurrentFiscalYearEndDate" use="optional" order="14"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityFilerCategory" xlink:label="EntityFilerCategory" xlink:title="EntityFilerCategory"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityFilerCategory" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityFilerCategory" xml:lang="en-US" id="label_dei_EntityFilerCategory_en-US">Entity Filer Category</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityFilerCategory" xlink:to="label_dei_EntityFilerCategory" xlink:title="label: EntityFilerCategory to label_dei_EntityFilerCategory" use="optional" order="15"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="EntityCommonStockSharesOutstanding" xlink:title="EntityCommonStockSharesOutstanding"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityCommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityCommonStockSharesOutstanding" xml:lang="en-US" id="label_dei_EntityCommonStockSharesOutstanding_en-US">Entity Common Stock, Shares Outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityCommonStockSharesOutstanding" xlink:to="label_dei_EntityCommonStockSharesOutstanding" xlink:title="label: EntityCommonStockSharesOutstanding to label_dei_EntityCommonStockSharesOutstanding" use="optional" order="16"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityCurrentReportingStatus" xlink:label="EntityCurrentReportingStatus" xlink:title="EntityCurrentReportingStatus"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityCurrentReportingStatus" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityCurrentReportingStatus" xml:lang="en-US" id="label_dei_EntityCurrentReportingStatus_en-US">Entity Current Reporting Status</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityCurrentReportingStatus" xlink:to="label_dei_EntityCurrentReportingStatus" xlink:title="label: EntityCurrentReportingStatus to label_dei_EntityCurrentReportingStatus" use="optional" order="17"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityVoluntaryFilers" xlink:label="EntityVoluntaryFilers" xlink:title="EntityVoluntaryFilers"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityVoluntaryFilers" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityVoluntaryFilers" xml:lang="en-US" id="label_dei_EntityVoluntaryFilers_en-US">Entity Voluntary Filers</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityVoluntaryFilers" xlink:to="label_dei_EntityVoluntaryFilers" xlink:title="label: EntityVoluntaryFilers to label_dei_EntityVoluntaryFilers" use="optional" order="18"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityWellKnownSeasonedIssuer" xlink:label="EntityWellKnownSeasonedIssuer" xlink:title="EntityWellKnownSeasonedIssuer"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityWellKnownSeasonedIssuer" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityWellKnownSeasonedIssuer" xml:lang="en-US" id="label_dei_EntityWellKnownSeasonedIssuer_en-US">Entity Well Known Seasoned Issuer</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityWellKnownSeasonedIssuer" xlink:to="label_dei_EntityWellKnownSeasonedIssuer" xlink:title="label: EntityWellKnownSeasonedIssuer to label_dei_EntityWellKnownSeasonedIssuer" use="optional" order="19"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_EntityPublicFloat" xlink:label="EntityPublicFloat" xlink:title="EntityPublicFloat"/>
    <link:label xlink:type="resource" xlink:label="label_dei_EntityPublicFloat" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_EntityPublicFloat" xml:lang="en-US" id="label_dei_EntityPublicFloat_en-US">Entity Public Float</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EntityPublicFloat" xlink:to="label_dei_EntityPublicFloat" xlink:title="label: EntityPublicFloat to label_dei_EntityPublicFloat" use="optional" order="20"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="DocumentFiscalYearFocus" xlink:title="DocumentFiscalYearFocus"/>
    <link:label xlink:type="resource" xlink:label="label_dei_DocumentFiscalYearFocus" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_DocumentFiscalYearFocus" xml:lang="en-US" id="label_dei_DocumentFiscalYearFocus_en-US">Document Fiscal Year Focus</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DocumentFiscalYearFocus" xlink:to="label_dei_DocumentFiscalYearFocus" xlink:title="label: DocumentFiscalYearFocus to label_dei_DocumentFiscalYearFocus" use="optional" order="21"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="DocumentFiscalPeriodFocus" xlink:title="DocumentFiscalPeriodFocus"/>
    <link:label xlink:type="resource" xlink:label="label_dei_DocumentFiscalPeriodFocus" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_dei_DocumentFiscalPeriodFocus" xml:lang="en-US" id="label_dei_DocumentFiscalPeriodFocus_en-US">Document Fiscal Period Focus</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DocumentFiscalPeriodFocus" xlink:to="label_dei_DocumentFiscalPeriodFocus" xlink:title="label: DocumentFiscalPeriodFocus to label_dei_DocumentFiscalPeriodFocus" use="optional" order="22"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="StatementOfFinancialPositionAbstract" xlink:title="StatementOfFinancialPositionAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StatementOfFinancialPositionAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_StatementOfFinancialPositionAbstract" xml:lang="en-US" id="label_us-gaap_StatementOfFinancialPositionAbstract_en-US">Statement of Financial Position</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="StatementOfFinancialPositionAbstract" xlink:to="label_us-gaap_StatementOfFinancialPositionAbstract" xlink:title="label: StatementOfFinancialPositionAbstract to label_us-gaap_StatementOfFinancialPositionAbstract" use="optional" order="1"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_StatementTable" xlink:label="StatementTable" xlink:title="StatementTable"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StatementTable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_StatementTable" xml:lang="en-US" id="label_us-gaap_StatementTable_en-US">Statement [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="StatementTable" xlink:to="label_us-gaap_StatementTable" xlink:title="label: StatementTable to label_us-gaap_StatementTable" use="optional" order="2"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_StatementLineItems" xlink:label="StatementLineItems" xlink:title="StatementLineItems"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StatementLineItems" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_StatementLineItems" xml:lang="en-US" id="label_us-gaap_StatementLineItems_en-US">Statement [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="StatementLineItems" xlink:to="label_us-gaap_StatementLineItems" xlink:title="label: StatementLineItems to label_us-gaap_StatementLineItems" use="optional" order="5"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="AssetsAbstract" xlink:title="AssetsAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AssetsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AssetsAbstract" xml:lang="en-US" id="label_us-gaap_AssetsAbstract_en-US">ASSETS</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AssetsAbstract" xlink:to="label_us-gaap_AssetsAbstract" xlink:title="label: AssetsAbstract to label_us-gaap_AssetsAbstract" use="optional" order="1"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="AssetsCurrentAbstract" xlink:title="AssetsCurrentAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AssetsCurrentAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AssetsCurrentAbstract" xml:lang="en-US" id="label_us-gaap_AssetsCurrentAbstract_en-US">Current assets:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AssetsCurrentAbstract" xlink:to="label_us-gaap_AssetsCurrentAbstract" xlink:title="label: AssetsCurrentAbstract to label_us-gaap_AssetsCurrentAbstract" use="optional" order="2"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="CashAndCashEquivalentsAtCarryingValue" xlink:title="CashAndCashEquivalentsAtCarryingValue"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:title="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xml:lang="en-US" id="verboseLabel_us-gaap_CashAndCashEquivalentsAtCarryingValue_en-US">Cash and cash equivalents</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CashAndCashEquivalentsAtCarryingValue" xlink:to="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:title="label: CashAndCashEquivalentsAtCarryingValue to label_us-gaap_CashAndCashEquivalentsAtCarryingValue" use="optional" order="3"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xml:lang="en-US" id="label_us-gaap_CashAndCashEquivalentsAtCarryingValue_en-US">Cash</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ReceivablesNetCurrent" xlink:label="ReceivablesNetCurrent" xlink:title="ReceivablesNetCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ReceivablesNetCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ReceivablesNetCurrent" xml:lang="en-US" id="label_us-gaap_ReceivablesNetCurrent_en-US">Unbilled contract payments receivable</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ReceivablesNetCurrent" xlink:to="label_us-gaap_ReceivablesNetCurrent" xlink:title="label: ReceivablesNetCurrent to label_us-gaap_ReceivablesNetCurrent" use="optional" order="4"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_DeferredCostsCurrent" xlink:label="DeferredCostsCurrent" xlink:title="DeferredCostsCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_DeferredCostsCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_DeferredCostsCurrent" xml:lang="en-US" id="label_us-gaap_DeferredCostsCurrent_en-US">Deferred financing costs</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DeferredCostsCurrent" xlink:to="label_us-gaap_DeferredCostsCurrent" xlink:title="label: DeferredCostsCurrent to label_us-gaap_DeferredCostsCurrent" use="optional" order="5"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PrepaidExpenseCurrent" xlink:label="PrepaidExpenseCurrent" xlink:title="PrepaidExpenseCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PrepaidExpenseCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PrepaidExpenseCurrent" xml:lang="en-US" id="label_us-gaap_PrepaidExpenseCurrent_en-US">Prepaid expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PrepaidExpenseCurrent" xlink:to="label_us-gaap_PrepaidExpenseCurrent" xlink:title="label: PrepaidExpenseCurrent to label_us-gaap_PrepaidExpenseCurrent" use="optional" order="6"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="AssetsCurrent" xlink:title="AssetsCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AssetsCurrent" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_AssetsCurrent" xml:lang="en-US" id="totalLabel_us-gaap_AssetsCurrent_en-US">Total current assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AssetsCurrent" xlink:to="label_us-gaap_AssetsCurrent" xlink:title="label: AssetsCurrent to label_us-gaap_AssetsCurrent" use="optional" order="7"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AssetsCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AssetsCurrent" xml:lang="en-US" id="label_us-gaap_AssetsCurrent_en-US">Total current assets</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="PropertyPlantAndEquipmentNet" xlink:title="PropertyPlantAndEquipmentNet"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PropertyPlantAndEquipmentNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PropertyPlantAndEquipmentNet" xml:lang="en-US" id="label_us-gaap_PropertyPlantAndEquipmentNet_en-US">Property and equipment, net</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PropertyPlantAndEquipmentNet" xlink:to="label_us-gaap_PropertyPlantAndEquipmentNet" xlink:title="label: PropertyPlantAndEquipmentNet to label_us-gaap_PropertyPlantAndEquipmentNet" use="optional" order="8"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="OtherAssetsNoncurrent" xlink:title="OtherAssetsNoncurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OtherAssetsNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OtherAssetsNoncurrent" xml:lang="en-US" id="label_us-gaap_OtherAssetsNoncurrent_en-US">Security deposits and other assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OtherAssetsNoncurrent" xlink:to="label_us-gaap_OtherAssetsNoncurrent" xlink:title="label: OtherAssetsNoncurrent to label_us-gaap_OtherAssetsNoncurrent" use="optional" order="9"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_Assets" xlink:label="Assets" xlink:title="Assets"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_Assets" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_Assets" xml:lang="en-US" id="totalLabel_us-gaap_Assets_en-US">Total assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="Assets" xlink:to="label_us-gaap_Assets" xlink:title="label: Assets to label_us-gaap_Assets" use="optional" order="10"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_Assets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_Assets" xml:lang="en-US" id="label_us-gaap_Assets_en-US">Total assets</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="LiabilitiesAndStockholdersEquityAbstract" xlink:title="LiabilitiesAndStockholdersEquityAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_LiabilitiesAndStockholdersEquityAbstract" xml:lang="en-US" id="label_us-gaap_LiabilitiesAndStockholdersEquityAbstract_en-US">LIABILITIES, PREFERRED STOCK AND STOCKHOLDERS' DEFICIT</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LiabilitiesAndStockholdersEquityAbstract" xlink:to="label_us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:title="label: LiabilitiesAndStockholdersEquityAbstract to label_us-gaap_LiabilitiesAndStockholdersEquityAbstract" use="optional" order="11"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="LiabilitiesCurrentAbstract" xlink:title="LiabilitiesCurrentAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesCurrentAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_LiabilitiesCurrentAbstract" xml:lang="en-US" id="label_us-gaap_LiabilitiesCurrentAbstract_en-US">Current liabilities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LiabilitiesCurrentAbstract" xlink:to="label_us-gaap_LiabilitiesCurrentAbstract" xlink:title="label: LiabilitiesCurrentAbstract to label_us-gaap_LiabilitiesCurrentAbstract" use="optional" order="12"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="AccountsPayableCurrent" xlink:title="AccountsPayableCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AccountsPayableCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AccountsPayableCurrent" xml:lang="en-US" id="label_us-gaap_AccountsPayableCurrent_en-US">Accounts payable</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AccountsPayableCurrent" xlink:to="label_us-gaap_AccountsPayableCurrent" xlink:title="label: AccountsPayableCurrent to label_us-gaap_AccountsPayableCurrent" use="optional" order="13"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="AccruedLiabilitiesCurrent" xlink:title="AccruedLiabilitiesCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AccruedLiabilitiesCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AccruedLiabilitiesCurrent" xml:lang="en-US" id="label_us-gaap_AccruedLiabilitiesCurrent_en-US">Accrued expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AccruedLiabilitiesCurrent" xlink:to="label_us-gaap_AccruedLiabilitiesCurrent" xlink:title="label: AccruedLiabilitiesCurrent to label_us-gaap_AccruedLiabilitiesCurrent" use="optional" order="14"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NotesAndLoansPayableCurrent" xlink:label="NotesAndLoansPayableCurrent" xlink:title="NotesAndLoansPayableCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NotesAndLoansPayableCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NotesAndLoansPayableCurrent" xml:lang="en-US" id="label_us-gaap_NotesAndLoansPayableCurrent_en-US">Notes payable and accrued interest</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesAndLoansPayableCurrent" xlink:to="label_us-gaap_NotesAndLoansPayableCurrent" xlink:title="label: NotesAndLoansPayableCurrent to label_us-gaap_NotesAndLoansPayableCurrent" use="optional" order="15"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NotesPayableAndAccruedInterestToRelatedParties" xlink:label="NotesPayableAndAccruedInterestToRelatedParties" xlink:title="NotesPayableAndAccruedInterestToRelatedParties"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesPayableAndAccruedInterestToRelatedParties" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NotesPayableAndAccruedInterestToRelatedParties" xml:lang="en-US" id="label_vsta_NotesPayableAndAccruedInterestToRelatedParties_en-US">Notes payable and accrued interest to related parties</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesPayableAndAccruedInterestToRelatedParties" xlink:to="label_vsta_NotesPayableAndAccruedInterestToRelatedParties" xlink:title="label: NotesPayableAndAccruedInterestToRelatedParties to label_vsta_NotesPayableAndAccruedInterestToRelatedParties" use="optional" order="16"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesPayableAndAccruedInterestToRelatedParties" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NotesPayableAndAccruedInterestToRelatedParties" xml:lang="en-US" id="documentation_vsta_NotesPayableAndAccruedInterestToRelatedParties_en-US">Notes payable and accrued interest to related parties</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_PutOptionAndNoteTermExtensionOptionLiabilities" xlink:label="PutOptionAndNoteTermExtensionOptionLiabilities" xlink:title="PutOptionAndNoteTermExtensionOptionLiabilities"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities" xml:lang="en-US" id="label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities_en-US">Put option and note term extension option liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PutOptionAndNoteTermExtensionOptionLiabilities" xlink:to="label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities" xlink:title="label: PutOptionAndNoteTermExtensionOptionLiabilities to label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities" use="optional" order="17"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_PutOptionAndNoteTermExtensionOptionLiabilities" xml:lang="en-US" id="documentation_vsta_PutOptionAndNoteTermExtensionOptionLiabilities_en-US">Put option and note term extension option liabilities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CapitalLeaseObligationsCurrent" xlink:label="CapitalLeaseObligationsCurrent" xlink:title="CapitalLeaseObligationsCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CapitalLeaseObligationsCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CapitalLeaseObligationsCurrent" xml:lang="en-US" id="label_us-gaap_CapitalLeaseObligationsCurrent_en-US">Capital lease obligations</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CapitalLeaseObligationsCurrent" xlink:to="label_us-gaap_CapitalLeaseObligationsCurrent" xlink:title="label: CapitalLeaseObligationsCurrent to label_us-gaap_CapitalLeaseObligationsCurrent" use="optional" order="18"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NoninterestBearingPromissoryNotes" xlink:label="NoninterestBearingPromissoryNotes" xlink:title="NoninterestBearingPromissoryNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NoninterestBearingPromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NoninterestBearingPromissoryNotes" xml:lang="en-US" id="label_vsta_NoninterestBearingPromissoryNotes_en-US">Non-interest bearing promissory notes, net, including $525,000 to related parties</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NoninterestBearingPromissoryNotes" xlink:to="label_vsta_NoninterestBearingPromissoryNotes" xlink:title="label: NoninterestBearingPromissoryNotes to label_vsta_NoninterestBearingPromissoryNotes" use="optional" order="19"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NoninterestBearingPromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NoninterestBearingPromissoryNotes" xml:lang="en-US" id="documentation_vsta_NoninterestBearingPromissoryNotes_en-US">Non-interest bearing promissory notes, net, including $525,000 to related parties</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_DeferredRevenues" xlink:label="DeferredRevenues" xlink:title="DeferredRevenues"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_DeferredRevenues" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_DeferredRevenues" xml:lang="en-US" id="label_vsta_DeferredRevenues_en-US">Deferred revenues</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DeferredRevenues" xlink:to="label_vsta_DeferredRevenues" xlink:title="label: DeferredRevenues to label_vsta_DeferredRevenues" use="optional" order="20"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_DeferredRevenues" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_DeferredRevenues" xml:lang="en-US" id="documentation_vsta_DeferredRevenues_en-US">Deferred revenues</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ConvertibleNotesPayable" xlink:label="ConvertibleNotesPayable" xlink:title="ConvertibleNotesPayable"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ConvertibleNotesPayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ConvertibleNotesPayable" xml:lang="en-US" id="label_us-gaap_ConvertibleNotesPayable_en-US">Convertible promissory notes, including $947,368 to related parties at March 31, 2011 - current portion</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ConvertibleNotesPayable" xlink:to="label_us-gaap_ConvertibleNotesPayable" xlink:title="label: ConvertibleNotesPayable to label_us-gaap_ConvertibleNotesPayable" use="optional" order="21"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AccruedInterestOnPromissoryNotes" xlink:label="AccruedInterestOnPromissoryNotes" xlink:title="AccruedInterestOnPromissoryNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccruedInterestOnPromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AccruedInterestOnPromissoryNotes" xml:lang="en-US" id="label_vsta_AccruedInterestOnPromissoryNotes_en-US">Accrued interest on convertible promissory notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AccruedInterestOnPromissoryNotes" xlink:to="label_vsta_AccruedInterestOnPromissoryNotes" xlink:title="label: AccruedInterestOnPromissoryNotes to label_vsta_AccruedInterestOnPromissoryNotes" use="optional" order="22"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccruedInterestOnPromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_AccruedInterestOnPromissoryNotes" xml:lang="en-US" id="documentation_vsta_AccruedInterestOnPromissoryNotes_en-US">Accrued interest on convertible promissory notes</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="LiabilitiesCurrent" xlink:title="LiabilitiesCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesCurrent" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_LiabilitiesCurrent" xml:lang="en-US" id="totalLabel_us-gaap_LiabilitiesCurrent_en-US">Total current liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LiabilitiesCurrent" xlink:to="label_us-gaap_LiabilitiesCurrent" xlink:title="label: LiabilitiesCurrent to label_us-gaap_LiabilitiesCurrent" use="optional" order="23"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_LiabilitiesCurrent" xml:lang="en-US" id="label_us-gaap_LiabilitiesCurrent_en-US">Total current liabilities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_LiabilitiesNoncurrentAbstract" xlink:label="LiabilitiesNoncurrentAbstract" xlink:title="LiabilitiesNoncurrentAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesNoncurrentAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_LiabilitiesNoncurrentAbstract" xml:lang="en-US" id="label_us-gaap_LiabilitiesNoncurrentAbstract_en-US">Non-current liabilities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LiabilitiesNoncurrentAbstract" xlink:to="label_us-gaap_LiabilitiesNoncurrentAbstract" xlink:title="label: LiabilitiesNoncurrentAbstract to label_us-gaap_LiabilitiesNoncurrentAbstract" use="optional" order="24"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NotesPayableAndAccruedInterest" xlink:label="NotesPayableAndAccruedInterest" xlink:title="NotesPayableAndAccruedInterest"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesPayableAndAccruedInterest" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NotesPayableAndAccruedInterest" xml:lang="en-US" id="label_vsta_NotesPayableAndAccruedInterest_en-US">Notes payable and accrued interest.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesPayableAndAccruedInterest" xlink:to="label_vsta_NotesPayableAndAccruedInterest" xlink:title="label: NotesPayableAndAccruedInterest to label_vsta_NotesPayableAndAccruedInterest" use="optional" order="25"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesPayableAndAccruedInterest" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NotesPayableAndAccruedInterest" xml:lang="en-US" id="documentation_vsta_NotesPayableAndAccruedInterest_en-US">Notes payable and accrued interest, Non-current</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xlink:label="NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xlink:title="NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xml:lang="en-US" id="label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent_en-US">Notes payable and accrued interest to related parties.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xlink:to="label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xlink:title="label: NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent to label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" use="optional" order="26"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent" xml:lang="en-US" id="documentation_vsta_NotesPayableAndAccruedInterestToRelatedPartiesNonCurrent_en-US">Notes payable and accrued interest to related parties, Non-current</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" xlink:label="ConvertiblePromissoryNotesNetOfCurrentPortion" xlink:title="ConvertiblePromissoryNotesNetOfCurrentPortion"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" xml:lang="en-US" id="label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion_en-US">Convertible promissory notes, net of current portion</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ConvertiblePromissoryNotesNetOfCurrentPortion" xlink:to="label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" xlink:title="label: ConvertiblePromissoryNotesNetOfCurrentPortion to label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" use="optional" order="27"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion" xml:lang="en-US" id="documentation_vsta_ConvertiblePromissoryNotesNetOfCurrentPortion_en-US">Convertible promissory notes, net of current portion</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AccruedInterestOnPromissoryNotesNonCurrent" xlink:label="AccruedInterestOnPromissoryNotesNonCurrent" xlink:title="AccruedInterestOnPromissoryNotesNonCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccruedInterestOnPromissoryNotesNonCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AccruedInterestOnPromissoryNotesNonCurrent" xml:lang="en-US" id="label_vsta_AccruedInterestOnPromissoryNotesNonCurrent_en-US">Accrued interest on convertible promissory notes.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AccruedInterestOnPromissoryNotesNonCurrent" xlink:to="label_vsta_AccruedInterestOnPromissoryNotesNonCurrent" xlink:title="label: AccruedInterestOnPromissoryNotesNonCurrent to label_vsta_AccruedInterestOnPromissoryNotesNonCurrent" use="optional" order="28"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccruedInterestOnPromissoryNotesNonCurrent" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_AccruedInterestOnPromissoryNotesNonCurrent" xml:lang="en-US" id="documentation_vsta_AccruedInterestOnPromissoryNotesNonCurrent_en-US">Accrued interest on convertible promissory notes, Non-current</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AccruedOfficersCompensation" xlink:label="AccruedOfficersCompensation" xlink:title="AccruedOfficersCompensation"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccruedOfficersCompensation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AccruedOfficersCompensation" xml:lang="en-US" id="label_vsta_AccruedOfficersCompensation_en-US">Accrued officers' compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AccruedOfficersCompensation" xlink:to="label_vsta_AccruedOfficersCompensation" xlink:title="label: AccruedOfficersCompensation to label_vsta_AccruedOfficersCompensation" use="optional" order="29"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccruedOfficersCompensation" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_AccruedOfficersCompensation" xml:lang="en-US" id="documentation_vsta_AccruedOfficersCompensation_en-US">Accrued officers' compensation</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CapitalLeaseObligationsNoncurrent" xlink:label="CapitalLeaseObligationsNoncurrent" xlink:title="CapitalLeaseObligationsNoncurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CapitalLeaseObligationsNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CapitalLeaseObligationsNoncurrent" xml:lang="en-US" id="label_us-gaap_CapitalLeaseObligationsNoncurrent_en-US">Capital lease obligations.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CapitalLeaseObligationsNoncurrent" xlink:to="label_us-gaap_CapitalLeaseObligationsNoncurrent" xlink:title="label: CapitalLeaseObligationsNoncurrent to label_us-gaap_CapitalLeaseObligationsNoncurrent" use="optional" order="30"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AccountsPayableNonCurrent" xlink:label="AccountsPayableNonCurrent" xlink:title="AccountsPayableNonCurrent"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccountsPayableNonCurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AccountsPayableNonCurrent" xml:lang="en-US" id="label_vsta_AccountsPayableNonCurrent_en-US">Accounts payable.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AccountsPayableNonCurrent" xlink:to="label_vsta_AccountsPayableNonCurrent" xlink:title="label: AccountsPayableNonCurrent to label_vsta_AccountsPayableNonCurrent" use="optional" order="31"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AccountsPayableNonCurrent" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_AccountsPayableNonCurrent" xml:lang="en-US" id="documentation_vsta_AccountsPayableNonCurrent_en-US">Accounts payable, Non-current</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="OtherLiabilitiesNoncurrent" xlink:title="OtherLiabilitiesNoncurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OtherLiabilitiesNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OtherLiabilitiesNoncurrent" xml:lang="en-US" id="label_us-gaap_OtherLiabilitiesNoncurrent_en-US">Warrant liability</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OtherLiabilitiesNoncurrent" xlink:to="label_us-gaap_OtherLiabilitiesNoncurrent" xlink:title="label: OtherLiabilitiesNoncurrent to label_us-gaap_OtherLiabilitiesNoncurrent" use="optional" order="32"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_LiabilitiesNoncurrent" xlink:label="LiabilitiesNoncurrent" xlink:title="LiabilitiesNoncurrent"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesNoncurrent" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_LiabilitiesNoncurrent" xml:lang="en-US" id="totalLabel_us-gaap_LiabilitiesNoncurrent_en-US">Total non-current liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LiabilitiesNoncurrent" xlink:to="label_us-gaap_LiabilitiesNoncurrent" xlink:title="label: LiabilitiesNoncurrent to label_us-gaap_LiabilitiesNoncurrent" use="optional" order="33"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesNoncurrent" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_LiabilitiesNoncurrent" xml:lang="en-US" id="label_us-gaap_LiabilitiesNoncurrent_en-US">Total non-current liabilities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_Liabilities" xlink:label="Liabilities" xlink:title="Liabilities"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_Liabilities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_Liabilities" xml:lang="en-US" id="totalLabel_us-gaap_Liabilities_en-US">Total liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="Liabilities" xlink:to="label_us-gaap_Liabilities" xlink:title="label: Liabilities to label_us-gaap_Liabilities" use="optional" order="34"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_Liabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_Liabilities" xml:lang="en-US" id="label_us-gaap_Liabilities_en-US">Total liabilities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="CommitmentsAndContingencies" xlink:title="CommitmentsAndContingencies"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CommitmentsAndContingencies" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CommitmentsAndContingencies" xml:lang="en-US" id="label_us-gaap_CommitmentsAndContingencies_en-US">Commitments and contingencies</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CommitmentsAndContingencies" xlink:to="label_us-gaap_CommitmentsAndContingencies" xlink:title="label: CommitmentsAndContingencies to label_us-gaap_CommitmentsAndContingencies" use="optional" order="35"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="PreferredStockValue" xlink:title="PreferredStockValue"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PreferredStockValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PreferredStockValue" xml:lang="en-US" id="label_us-gaap_PreferredStockValue_en-US">Preferred stock, no par value; no shares authorized at September 30, 2011; 20,000,000 shares authorized at March 31, 2011; no shares issued and outstanding at September 30, 2011; 2,884,655 shares issued and outstanding at March 31, 2011</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PreferredStockValue" xlink:to="label_us-gaap_PreferredStockValue" xlink:title="label: PreferredStockValue to label_us-gaap_PreferredStockValue" use="optional" order="36"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="StockholdersEquityAbstract" xlink:title="StockholdersEquityAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StockholdersEquityAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_StockholdersEquityAbstract" xml:lang="en-US" id="label_us-gaap_StockholdersEquityAbstract_en-US">Stockholders' deficit:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="StockholdersEquityAbstract" xlink:to="label_us-gaap_StockholdersEquityAbstract" xlink:title="label: StockholdersEquityAbstract to label_us-gaap_StockholdersEquityAbstract" use="optional" order="37"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CommonStockValue" xlink:label="CommonStockValue" xlink:title="CommonStockValue"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CommonStockValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CommonStockValue" xml:lang="en-US" id="label_us-gaap_CommonStockValue_en-US">Common stock, $0.001 par value; 400,000,000 shares authorized; 15,241,904 and 5,241,110 shares outstanding at September 30, 2011 and March 31, 2011, respectively</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CommonStockValue" xlink:to="label_us-gaap_CommonStockValue" xlink:title="label: CommonStockValue to label_us-gaap_CommonStockValue" use="optional" order="38"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="AdditionalPaidInCapital" xlink:title="AdditionalPaidInCapital"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AdditionalPaidInCapital" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AdditionalPaidInCapital" xml:lang="en-US" id="label_us-gaap_AdditionalPaidInCapital_en-US">Additional paid-in capital</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AdditionalPaidInCapital" xlink:to="label_us-gaap_AdditionalPaidInCapital" xlink:title="label: AdditionalPaidInCapital to label_us-gaap_AdditionalPaidInCapital" use="optional" order="39"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NotesReceivableFromSaleOfCommonStockToOthers" xlink:label="NotesReceivableFromSaleOfCommonStockToOthers" xlink:title="NotesReceivableFromSaleOfCommonStockToOthers"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesReceivableFromSaleOfCommonStockToOthers" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NotesReceivableFromSaleOfCommonStockToOthers" xml:lang="en-US" id="label_vsta_NotesReceivableFromSaleOfCommonStockToOthers_en-US">Notes receivable from sale of common stock to others at September 30, 2011 and to related parties upon exercise of options and warrants at March, 31, 2011</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesReceivableFromSaleOfCommonStockToOthers" xlink:to="label_vsta_NotesReceivableFromSaleOfCommonStockToOthers" xlink:title="label: NotesReceivableFromSaleOfCommonStockToOthers to label_vsta_NotesReceivableFromSaleOfCommonStockToOthers" use="optional" order="40"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesReceivableFromSaleOfCommonStockToOthers" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NotesReceivableFromSaleOfCommonStockToOthers" xml:lang="en-US" id="documentation_vsta_NotesReceivableFromSaleOfCommonStockToOthers_en-US">Notes receivable from sale of common stock to others at June 30, 2011 and to related parties upon exercise of options and warrants at March, 31, 2011</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="RetainedEarningsAccumulatedDeficit" xlink:title="RetainedEarningsAccumulatedDeficit"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_RetainedEarningsAccumulatedDeficit" xml:lang="en-US" id="label_us-gaap_RetainedEarningsAccumulatedDeficit_en-US">Deficit accumulated during development stage</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="RetainedEarningsAccumulatedDeficit" xlink:to="label_us-gaap_RetainedEarningsAccumulatedDeficit" xlink:title="label: RetainedEarningsAccumulatedDeficit to label_us-gaap_RetainedEarningsAccumulatedDeficit" use="optional" order="41"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="StockholdersEquity" xlink:title="StockholdersEquity"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_StockholdersEquity" xml:lang="en-US" id="totalLabel_us-gaap_StockholdersEquity_en-US">Total stockholders' deficit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="StockholdersEquity" xlink:to="label_us-gaap_StockholdersEquity" xlink:title="label: StockholdersEquity to label_us-gaap_StockholdersEquity" use="optional" order="42"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_StockholdersEquity" xml:lang="en-US" id="label_us-gaap_StockholdersEquity_en-US">Total stockholders' deficit</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="LiabilitiesAndStockholdersEquity" xlink:title="LiabilitiesAndStockholdersEquity"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesAndStockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_LiabilitiesAndStockholdersEquity" xml:lang="en-US" id="totalLabel_us-gaap_LiabilitiesAndStockholdersEquity_en-US">Total liabilities, preferred stock and stockholders' deficit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LiabilitiesAndStockholdersEquity" xlink:to="label_us-gaap_LiabilitiesAndStockholdersEquity" xlink:title="label: LiabilitiesAndStockholdersEquity to label_us-gaap_LiabilitiesAndStockholdersEquity" use="optional" order="43"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_LiabilitiesAndStockholdersEquity" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_LiabilitiesAndStockholdersEquity" xml:lang="en-US" id="label_us-gaap_LiabilitiesAndStockholdersEquity_en-US">Total liabilities, preferred stock and stockholders' deficit</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ConvertiblePromissoryNotes" xlink:label="ConvertiblePromissoryNotes" xlink:title="ConvertiblePromissoryNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConvertiblePromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ConvertiblePromissoryNotes" xml:lang="en-US" id="label_vsta_ConvertiblePromissoryNotes_en-US">Convertible promissory notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ConvertiblePromissoryNotes" xlink:to="label_vsta_ConvertiblePromissoryNotes" xlink:title="label: ConvertiblePromissoryNotes to label_vsta_ConvertiblePromissoryNotes" use="optional" order="1"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConvertiblePromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ConvertiblePromissoryNotes" xml:lang="en-US" id="documentation_vsta_ConvertiblePromissoryNotes_en-US">Convertible promissory notes</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PreferredStockNoParValue" xlink:label="PreferredStockNoParValue" xlink:title="PreferredStockNoParValue"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PreferredStockNoParValue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PreferredStockNoParValue" xml:lang="en-US" id="label_us-gaap_PreferredStockNoParValue_en-US">Preferred Stock, No Par Value</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PreferredStockNoParValue" xlink:to="label_us-gaap_PreferredStockNoParValue" xlink:title="label: PreferredStockNoParValue to label_us-gaap_PreferredStockNoParValue" use="optional" order="2"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="PreferredStockSharesAuthorized" xlink:title="PreferredStockSharesAuthorized"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PreferredStockSharesAuthorized" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PreferredStockSharesAuthorized" xml:lang="en-US" id="label_us-gaap_PreferredStockSharesAuthorized_en-US">Preferred Stock, Shares Authorized</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PreferredStockSharesAuthorized" xlink:to="label_us-gaap_PreferredStockSharesAuthorized" xlink:title="label: PreferredStockSharesAuthorized to label_us-gaap_PreferredStockSharesAuthorized" use="optional" order="3"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="PreferredStockSharesIssued" xlink:title="PreferredStockSharesIssued"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PreferredStockSharesIssued" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PreferredStockSharesIssued" xml:lang="en-US" id="label_us-gaap_PreferredStockSharesIssued_en-US">Preferred Stock, Shares Issued</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PreferredStockSharesIssued" xlink:to="label_us-gaap_PreferredStockSharesIssued" xlink:title="label: PreferredStockSharesIssued to label_us-gaap_PreferredStockSharesIssued" use="optional" order="4"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="PreferredStockSharesOutstanding" xlink:title="PreferredStockSharesOutstanding"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PreferredStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PreferredStockSharesOutstanding" xml:lang="en-US" id="label_us-gaap_PreferredStockSharesOutstanding_en-US">Preferred Stock, Shares Outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PreferredStockSharesOutstanding" xlink:to="label_us-gaap_PreferredStockSharesOutstanding" xlink:title="label: PreferredStockSharesOutstanding to label_us-gaap_PreferredStockSharesOutstanding" use="optional" order="5"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="CommonStockParOrStatedValuePerShare" xlink:title="CommonStockParOrStatedValuePerShare"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CommonStockParOrStatedValuePerShare" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CommonStockParOrStatedValuePerShare" xml:lang="en-US" id="label_us-gaap_CommonStockParOrStatedValuePerShare_en-US">Common Stock, Par Value Per Share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CommonStockParOrStatedValuePerShare" xlink:to="label_us-gaap_CommonStockParOrStatedValuePerShare" xlink:title="label: CommonStockParOrStatedValuePerShare to label_us-gaap_CommonStockParOrStatedValuePerShare" use="optional" order="6"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="CommonStockSharesAuthorized" xlink:title="CommonStockSharesAuthorized"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CommonStockSharesAuthorized" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CommonStockSharesAuthorized" xml:lang="en-US" id="label_us-gaap_CommonStockSharesAuthorized_en-US">Common Stock, Shares Authorized</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CommonStockSharesAuthorized" xlink:to="label_us-gaap_CommonStockSharesAuthorized" xlink:title="label: CommonStockSharesAuthorized to label_us-gaap_CommonStockSharesAuthorized" use="optional" order="7"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="CommonStockSharesOutstanding" xlink:title="CommonStockSharesOutstanding"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CommonStockSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_CommonStockSharesOutstanding" xml:lang="en-US" id="label_us-gaap_CommonStockSharesOutstanding_en-US">Common Stock, Shares, Outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CommonStockSharesOutstanding" xlink:to="label_us-gaap_CommonStockSharesOutstanding" xlink:title="label: CommonStockSharesOutstanding to label_us-gaap_CommonStockSharesOutstanding" use="optional" order="8"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NotesReceivableFromSaleOfCommonStock" xlink:label="NotesReceivableFromSaleOfCommonStock" xlink:title="NotesReceivableFromSaleOfCommonStock"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesReceivableFromSaleOfCommonStock" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:title="label_vsta_NotesReceivableFromSaleOfCommonStock" xml:lang="en-US" id="verboseLabel_vsta_NotesReceivableFromSaleOfCommonStock_en-US">Notes receivable from sale of common stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesReceivableFromSaleOfCommonStock" xlink:to="label_vsta_NotesReceivableFromSaleOfCommonStock" xlink:title="label: NotesReceivableFromSaleOfCommonStock to label_vsta_NotesReceivableFromSaleOfCommonStock" use="optional" order="9"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesReceivableFromSaleOfCommonStock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NotesReceivableFromSaleOfCommonStock" xml:lang="en-US" id="label_vsta_NotesReceivableFromSaleOfCommonStock_en-US">Notes receivable from sale of common stock</link:label>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesReceivableFromSaleOfCommonStock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NotesReceivableFromSaleOfCommonStock" xml:lang="en-US" id="documentation_vsta_NotesReceivableFromSaleOfCommonStock_en-US">Notes receivable from sale of common stock</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:label="IncomeStatementAbstract" xlink:title="IncomeStatementAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncomeStatementAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncomeStatementAbstract" xml:lang="en-US" id="label_us-gaap_IncomeStatementAbstract_en-US">Income Statement</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncomeStatementAbstract" xlink:to="label_us-gaap_IncomeStatementAbstract" xlink:title="label: IncomeStatementAbstract to label_us-gaap_IncomeStatementAbstract" use="optional" order="1"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_RevenuesAbstract" xlink:label="RevenuesAbstract" xlink:title="RevenuesAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_RevenuesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_RevenuesAbstract" xml:lang="en-US" id="label_us-gaap_RevenuesAbstract_en-US">Revenues:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="RevenuesAbstract" xlink:to="label_us-gaap_RevenuesAbstract" xlink:title="label: RevenuesAbstract to label_us-gaap_RevenuesAbstract" use="optional" order="1"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_RevenueFromGrants" xlink:label="RevenueFromGrants" xlink:title="RevenueFromGrants"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_RevenueFromGrants" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_RevenueFromGrants" xml:lang="en-US" id="label_us-gaap_RevenueFromGrants_en-US">Grant revenue</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="RevenueFromGrants" xlink:to="label_us-gaap_RevenueFromGrants" xlink:title="label: RevenueFromGrants to label_us-gaap_RevenueFromGrants" use="optional" order="2"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_RevenueFromExternalCustomers" xlink:label="RevenueFromExternalCustomers" xlink:title="RevenueFromExternalCustomers"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_RevenueFromExternalCustomers" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_RevenueFromExternalCustomers" xml:lang="en-US" id="label_vsta_RevenueFromExternalCustomers_en-US">Collaboration revenue</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="RevenueFromExternalCustomers" xlink:to="label_vsta_RevenueFromExternalCustomers" xlink:title="label: RevenueFromExternalCustomers to label_vsta_RevenueFromExternalCustomers" use="optional" order="3"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_RevenueFromExternalCustomers" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_RevenueFromExternalCustomers" xml:lang="en-US" id="documentation_vsta_RevenueFromExternalCustomers_en-US">Collaboration revenue</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OtherSalesRevenueNet" xlink:label="OtherSalesRevenueNet" xlink:title="OtherSalesRevenueNet"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OtherSalesRevenueNet" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OtherSalesRevenueNet" xml:lang="en-US" id="label_us-gaap_OtherSalesRevenueNet_en-US">Other</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OtherSalesRevenueNet" xlink:to="label_us-gaap_OtherSalesRevenueNet" xlink:title="label: OtherSalesRevenueNet to label_us-gaap_OtherSalesRevenueNet" use="optional" order="4"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_Revenues" xlink:label="Revenues" xlink:title="Revenues"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_Revenues" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_Revenues" xml:lang="en-US" id="totalLabel_us-gaap_Revenues_en-US">Total revenues</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="Revenues" xlink:to="label_us-gaap_Revenues" xlink:title="label: Revenues to label_us-gaap_Revenues" use="optional" order="5"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_Revenues" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_Revenues" xml:lang="en-US" id="label_us-gaap_Revenues_en-US">Total revenues</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="OperatingExpensesAbstract" xlink:title="OperatingExpensesAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OperatingExpensesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OperatingExpensesAbstract" xml:lang="en-US" id="label_us-gaap_OperatingExpensesAbstract_en-US">Operating expenses:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OperatingExpensesAbstract" xlink:to="label_us-gaap_OperatingExpensesAbstract" xlink:title="label: OperatingExpensesAbstract to label_us-gaap_OperatingExpensesAbstract" use="optional" order="6"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="ResearchAndDevelopmentExpense" xlink:title="ResearchAndDevelopmentExpense"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ResearchAndDevelopmentExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ResearchAndDevelopmentExpense" xml:lang="en-US" id="label_us-gaap_ResearchAndDevelopmentExpense_en-US">Research and development</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ResearchAndDevelopmentExpense" xlink:to="label_us-gaap_ResearchAndDevelopmentExpense" xlink:title="label: ResearchAndDevelopmentExpense to label_us-gaap_ResearchAndDevelopmentExpense" use="optional" order="7"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AcquiredInProcessResearchAndDevelopment" xlink:label="AcquiredInProcessResearchAndDevelopment" xlink:title="AcquiredInProcessResearchAndDevelopment"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AcquiredInProcessResearchAndDevelopment" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AcquiredInProcessResearchAndDevelopment" xml:lang="en-US" id="label_vsta_AcquiredInProcessResearchAndDevelopment_en-US">Acquired in-process research and development</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AcquiredInProcessResearchAndDevelopment" xlink:to="label_vsta_AcquiredInProcessResearchAndDevelopment" xlink:title="label: AcquiredInProcessResearchAndDevelopment to label_vsta_AcquiredInProcessResearchAndDevelopment" use="optional" order="8"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AcquiredInProcessResearchAndDevelopment" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_AcquiredInProcessResearchAndDevelopment" xml:lang="en-US" id="documentation_vsta_AcquiredInProcessResearchAndDevelopment_en-US">Acquired in-process research and development</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:label="GeneralAndAdministrativeExpense" xlink:title="GeneralAndAdministrativeExpense"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_GeneralAndAdministrativeExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_GeneralAndAdministrativeExpense" xml:lang="en-US" id="label_us-gaap_GeneralAndAdministrativeExpense_en-US">General and administrative</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="GeneralAndAdministrativeExpense" xlink:to="label_us-gaap_GeneralAndAdministrativeExpense" xlink:title="label: GeneralAndAdministrativeExpense to label_us-gaap_GeneralAndAdministrativeExpense" use="optional" order="9"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="OperatingExpenses" xlink:title="OperatingExpenses"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OperatingExpenses" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_OperatingExpenses" xml:lang="en-US" id="totalLabel_us-gaap_OperatingExpenses_en-US">Total operating expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OperatingExpenses" xlink:to="label_us-gaap_OperatingExpenses" xlink:title="label: OperatingExpenses to label_us-gaap_OperatingExpenses" use="optional" order="10"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OperatingExpenses" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OperatingExpenses" xml:lang="en-US" id="label_us-gaap_OperatingExpenses_en-US">Total operating expenses</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="OperatingIncomeLoss" xlink:title="OperatingIncomeLoss"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OperatingIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_OperatingIncomeLoss" xml:lang="en-US" id="totalLabel_us-gaap_OperatingIncomeLoss_en-US">Loss from operations</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OperatingIncomeLoss" xlink:to="label_us-gaap_OperatingIncomeLoss" xlink:title="label: OperatingIncomeLoss to label_us-gaap_OperatingIncomeLoss" use="optional" order="11"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OperatingIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OperatingIncomeLoss" xml:lang="en-US" id="label_us-gaap_OperatingIncomeLoss_en-US">Loss from operations</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="NonoperatingIncomeExpenseAbstract" xlink:title="NonoperatingIncomeExpenseAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NonoperatingIncomeExpenseAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NonoperatingIncomeExpenseAbstract" xml:lang="en-US" id="label_us-gaap_NonoperatingIncomeExpenseAbstract_en-US">Other expenses, net:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NonoperatingIncomeExpenseAbstract" xlink:to="label_us-gaap_NonoperatingIncomeExpenseAbstract" xlink:title="label: NonoperatingIncomeExpenseAbstract to label_us-gaap_NonoperatingIncomeExpenseAbstract" use="optional" order="12"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_InterestExpense" xlink:label="InterestExpense" xlink:title="InterestExpense"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_InterestExpense" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_InterestExpense" xml:lang="en-US" id="negated_us-gaap_InterestExpense_en-US">Interest expense, net</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="InterestExpense" xlink:to="label_us-gaap_InterestExpense" xlink:title="label: InterestExpense to label_us-gaap_InterestExpense" use="optional" order="13"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_InterestExpense" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_InterestExpense" xml:lang="en-US" id="label_us-gaap_InterestExpense_en-US">Interest expense, net</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:label="ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:title="ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xml:lang="en-US" id="negated_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities_en-US">Change in put and note extension option and warrant liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:to="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:title="label: ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities to label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" use="optional" order="14"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xml:lang="en-US" id="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities_en-US">Change in put and note extension option and warrant liabilities</link:label>
    <link:label xlink:type="resource" xlink:label="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities" xml:lang="en-US" id="documentation_vsta_ChangeInPutAndNoteExtensionOptionAndWarrantLiabilities_en-US">Change in put and note extension option and warrant liabilities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_OtherIncome" xlink:label="OtherIncome" xlink:title="OtherIncome"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_OtherIncome" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_OtherIncome" xml:lang="en-US" id="label_us-gaap_OtherIncome_en-US">Other income</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="OtherIncome" xlink:to="label_us-gaap_OtherIncome" xlink:title="label: OtherIncome to label_us-gaap_OtherIncome" use="optional" order="15"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:title="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments"/>
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    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:to="label_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:title="label: IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments to label_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" use="optional" order="16"/>
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    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_NetIncomeLoss" xml:lang="en-US" id="totalLabel_us-gaap_NetIncomeLoss_en-US">Net loss</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetIncomeLoss" xlink:to="label_us-gaap_NetIncomeLoss" xlink:title="label: NetIncomeLoss to label_us-gaap_NetIncomeLoss" use="optional" order="18"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetIncomeLoss" xml:lang="en-US" id="label_us-gaap_NetIncomeLoss_en-US">Net loss</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="EarningsPerShareDiluted" xlink:title="EarningsPerShareDiluted"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_EarningsPerShareDiluted" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_EarningsPerShareDiluted" xml:lang="en-US" id="label_us-gaap_EarningsPerShareDiluted_en-US">Basic and diluted net loss per common share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="EarningsPerShareDiluted" xlink:to="label_us-gaap_EarningsPerShareDiluted" xlink:title="label: EarningsPerShareDiluted to label_us-gaap_EarningsPerShareDiluted" use="optional" order="19"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="WeightedAverageNumberOfDilutedSharesOutstanding" xlink:title="WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xml:lang="en-US" id="label_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_en-US">Weighted average shares used in computing basic and diluted net loss per common share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="label_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:title="label: WeightedAverageNumberOfDilutedSharesOutstanding to label_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" use="optional" order="20"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="StatementOfCashFlowsAbstract" xlink:title="StatementOfCashFlowsAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_StatementOfCashFlowsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_StatementOfCashFlowsAbstract" xml:lang="en-US" id="label_us-gaap_StatementOfCashFlowsAbstract_en-US">Statement of Cash Flows</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="StatementOfCashFlowsAbstract" xlink:to="label_us-gaap_StatementOfCashFlowsAbstract" xlink:title="label: StatementOfCashFlowsAbstract to label_us-gaap_StatementOfCashFlowsAbstract" use="optional" order="1"/>
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    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xml:lang="en-US" id="label_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_en-US">Cash flows from operating activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="label_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:title="label: NetCashProvidedByUsedInOperatingActivitiesAbstract to label_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" use="optional" order="1"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetIncomeLoss" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:title="label_us-gaap_NetIncomeLoss" xml:lang="en-US" id="terseLabel_us-gaap_NetIncomeLoss_en-US">Net loss</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:title="AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xml:lang="en-US" id="label_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_en-US">Adjustments to reconcile net loss to net cash used in operating activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="label_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:title="label: AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract to label_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" use="optional" order="3"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_DepreciationAndAmortization" xlink:label="DepreciationAndAmortization" xlink:title="DepreciationAndAmortization"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_DepreciationAndAmortization" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_DepreciationAndAmortization" xml:lang="en-US" id="label_us-gaap_DepreciationAndAmortization_en-US">Depreciation and amortization</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="DepreciationAndAmortization" xlink:to="label_us-gaap_DepreciationAndAmortization" xlink:title="label: DepreciationAndAmortization to label_us-gaap_DepreciationAndAmortization" use="optional" order="4"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AcquiredInProcessResearchAndDevelopment" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:title="label_vsta_AcquiredInProcessResearchAndDevelopment" xml:lang="en-US" id="terseLabel_vsta_AcquiredInProcessResearchAndDevelopment_en-US">Acquired in-process research and development</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AmortizationOfImputedDiscountOnNonInterestBearingNotes" xlink:label="AmortizationOfImputedDiscountOnNonInterestBearingNotes" xlink:title="AmortizationOfImputedDiscountOnNonInterestBearingNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AmortizationOfImputedDiscountOnNonInterestBearingNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AmortizationOfImputedDiscountOnNonInterestBearingNotes" xml:lang="en-US" id="label_vsta_AmortizationOfImputedDiscountOnNonInterestBearingNotes_en-US">Amortization of imputed discount on non-interest bearing notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AmortizationOfImputedDiscountOnNonInterestBearingNotes" xlink:to="label_vsta_AmortizationOfImputedDiscountOnNonInterestBearingNotes" xlink:title="label: AmortizationOfImputedDiscountOnNonInterestBearingNotes to label_vsta_AmortizationOfImputedDiscountOnNonInterestBearingNotes" use="optional" order="6"/>
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    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AmortizationOfDiscountsOn775And10ConvertibleNotes" xlink:label="AmortizationOfDiscountsOn775And10ConvertibleNotes" xlink:title="AmortizationOfDiscountsOn775And10ConvertibleNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AmortizationOfDiscountsOn775And10ConvertibleNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AmortizationOfDiscountsOn775And10ConvertibleNotes" xml:lang="en-US" id="label_vsta_AmortizationOfDiscountsOn775And10ConvertibleNotes_en-US">Amortization of discounts on 7%, 7.5% and 10% notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AmortizationOfDiscountsOn775And10ConvertibleNotes" xlink:to="label_vsta_AmortizationOfDiscountsOn775And10ConvertibleNotes" xlink:title="label: AmortizationOfDiscountsOn775And10ConvertibleNotes to label_vsta_AmortizationOfDiscountsOn775And10ConvertibleNotes" use="optional" order="7"/>
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    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AmortizationOfDiscountsOnPlatinumNotes" xlink:label="AmortizationOfDiscountsOnPlatinumNotes" xlink:title="AmortizationOfDiscountsOnPlatinumNotes"/>
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    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" xlink:label="AmortizationOfDiscountsOnAugust2010ShortTermNotes" xlink:title="AmortizationOfDiscountsOnAugust2010ShortTermNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" xml:lang="en-US" id="label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes_en-US">Amortization of discounts on August 2010 Short-Term Notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AmortizationOfDiscountsOnAugust2010ShortTermNotes" xlink:to="label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" xlink:title="label: AmortizationOfDiscountsOnAugust2010ShortTermNotes to label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" use="optional" order="9"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes" xml:lang="en-US" id="documentation_vsta_AmortizationOfDiscountsOnAugust2010ShortTermNotes_en-US">Amortization of discounts on August 2010 Short-Term Notes</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities" xlink:label="ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities" xlink:title="ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities" xml:lang="en-US" id="label_vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities_en-US">Change in put and note term extension option and warrant liabilities</link:label>
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    <link:label xlink:type="resource" xlink:label="label_vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities" xml:lang="en-US" id="documentation_vsta_ChangeInPutAndNoteTermExtensionOptionAndWarrantLiabilities_en-US">Change in put and note term extension option and warrant liabilities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="ShareBasedCompensation" xlink:title="ShareBasedCompensation"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ShareBasedCompensation" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ShareBasedCompensation" xml:lang="en-US" id="label_us-gaap_ShareBasedCompensation_en-US">Stock-based compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ShareBasedCompensation" xlink:to="label_us-gaap_ShareBasedCompensation" xlink:title="label: ShareBasedCompensation to label_us-gaap_ShareBasedCompensation" use="optional" order="11"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims" xlink:label="IssuanceOfStockAndWarrantsForServicesOrClaims" xlink:title="IssuanceOfStockAndWarrantsForServicesOrClaims"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims" xml:lang="en-US" id="label_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims_en-US">Fair value of Series C preferred stock, common stock, and warrants granted for services</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IssuanceOfStockAndWarrantsForServicesOrClaims" xlink:to="label_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims" xlink:title="label: IssuanceOfStockAndWarrantsForServicesOrClaims to label_us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims" use="optional" order="12"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xlink:label="ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xlink:title="ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xml:lang="en-US" id="label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes_en-US">Consulting services by related parties settled by issuing promissory notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xlink:to="label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xlink:title="label: ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes to label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" use="optional" order="13"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes" xml:lang="en-US" id="documentation_vsta_ConsultingServicesByRelatedPartiesSettledByIssuingPromissoryNotes_en-US">Consulting services by related parties settled by issuing promissory notes</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:label="GainLossOnSaleOfPropertyPlantEquipment" xlink:title="GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xml:lang="en-US" id="negated_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_en-US">Gain on sale of assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="GainLossOnSaleOfPropertyPlantEquipment" xlink:to="label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:title="label: GainLossOnSaleOfPropertyPlantEquipment to label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment" use="optional" order="14"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xml:lang="en-US" id="label_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_en-US">Gain on sale of assets</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="IncreaseDecreaseInOperatingCapitalAbstract" xlink:title="IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xml:lang="en-US" id="label_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_en-US">Changes in operating assets and liabilities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="label_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:title="label: IncreaseDecreaseInOperatingCapitalAbstract to label_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" use="optional" order="15"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="IncreaseDecreaseInAccountsReceivable" xlink:title="IncreaseDecreaseInAccountsReceivable"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_IncreaseDecreaseInAccountsReceivable" xml:lang="en-US" id="negated_us-gaap_IncreaseDecreaseInAccountsReceivable_en-US">Unbilled contract payments receivable</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncreaseDecreaseInAccountsReceivable" xlink:to="label_us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:title="label: IncreaseDecreaseInAccountsReceivable to label_us-gaap_IncreaseDecreaseInAccountsReceivable" use="optional" order="16"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncreaseDecreaseInAccountsReceivable" xml:lang="en-US" id="label_us-gaap_IncreaseDecreaseInAccountsReceivable_en-US">Unbilled contract payments receivable (IncreaseDecreaseInAccountsReceivable)</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:title="IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xml:lang="en-US" id="negated_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_en-US">Prepaid expenses and other current assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:to="label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:title="label: IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets to label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" use="optional" order="17"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xml:lang="en-US" id="label_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_en-US">Prepaid expenses and other current assets</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncreaseDecreaseInDepositOtherAssets" xlink:label="IncreaseDecreaseInDepositOtherAssets" xlink:title="IncreaseDecreaseInDepositOtherAssets"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInDepositOtherAssets" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_IncreaseDecreaseInDepositOtherAssets" xml:lang="en-US" id="negated_us-gaap_IncreaseDecreaseInDepositOtherAssets_en-US">Security deposits and other assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncreaseDecreaseInDepositOtherAssets" xlink:to="label_us-gaap_IncreaseDecreaseInDepositOtherAssets" xlink:title="label: IncreaseDecreaseInDepositOtherAssets to label_us-gaap_IncreaseDecreaseInDepositOtherAssets" use="optional" order="18"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInDepositOtherAssets" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncreaseDecreaseInDepositOtherAssets" xml:lang="en-US" id="label_us-gaap_IncreaseDecreaseInDepositOtherAssets_en-US">Security deposits and other assets (IncreaseDecreaseInDepositOtherAssets)</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:label="IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:title="IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xml:lang="en-US" id="label_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_en-US">Accounts payable and accrued expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:to="label_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:title="label: IncreaseDecreaseInAccountsPayableAndAccruedLiabilities to label_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" use="optional" order="19"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:label="IncreaseDecreaseInDeferredRevenue" xlink:title="IncreaseDecreaseInDeferredRevenue"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_IncreaseDecreaseInDeferredRevenue" xml:lang="en-US" id="label_us-gaap_IncreaseDecreaseInDeferredRevenue_en-US">Deferred revenues.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="IncreaseDecreaseInDeferredRevenue" xlink:to="label_us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:title="label: IncreaseDecreaseInDeferredRevenue to label_us-gaap_IncreaseDecreaseInDeferredRevenue" use="optional" order="20"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="NetCashProvidedByUsedInOperatingActivities" xlink:title="NetCashProvidedByUsedInOperatingActivities"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_NetCashProvidedByUsedInOperatingActivities" xml:lang="en-US" id="totalLabel_us-gaap_NetCashProvidedByUsedInOperatingActivities_en-US">Net cash used in operating activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetCashProvidedByUsedInOperatingActivities" xlink:to="label_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:title="label: NetCashProvidedByUsedInOperatingActivities to label_us-gaap_NetCashProvidedByUsedInOperatingActivities" use="optional" order="21"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetCashProvidedByUsedInOperatingActivities" xml:lang="en-US" id="label_us-gaap_NetCashProvidedByUsedInOperatingActivities_en-US">Net cash used in operating activities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:title="NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xml:lang="en-US" id="label_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_en-US">Cash flows from investing activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="label_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:title="label: NetCashProvidedByUsedInInvestingActivitiesAbstract to label_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" use="optional" order="22"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:label="PaymentsToAcquireMachineryAndEquipment" xlink:title="PaymentsToAcquireMachineryAndEquipment"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_PaymentsToAcquireMachineryAndEquipment" xml:lang="en-US" id="negated_us-gaap_PaymentsToAcquireMachineryAndEquipment_en-US">Purchases of equipment, net</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="PaymentsToAcquireMachineryAndEquipment" xlink:to="label_us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:title="label: PaymentsToAcquireMachineryAndEquipment to label_us-gaap_PaymentsToAcquireMachineryAndEquipment" use="optional" order="23"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_PaymentsToAcquireMachineryAndEquipment" xml:lang="en-US" id="label_us-gaap_PaymentsToAcquireMachineryAndEquipment_en-US">Purchases of equipment, net</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="NetCashProvidedByUsedInInvestingActivities" xlink:title="NetCashProvidedByUsedInInvestingActivities"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_NetCashProvidedByUsedInInvestingActivities" xml:lang="en-US" id="totalLabel_us-gaap_NetCashProvidedByUsedInInvestingActivities_en-US">Net cash used in investing activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetCashProvidedByUsedInInvestingActivities" xlink:to="label_us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:title="label: NetCashProvidedByUsedInInvestingActivities to label_us-gaap_NetCashProvidedByUsedInInvestingActivities" use="optional" order="24"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetCashProvidedByUsedInInvestingActivities" xml:lang="en-US" id="label_us-gaap_NetCashProvidedByUsedInInvestingActivities_en-US">Net cash used in investing activities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:title="NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xml:lang="en-US" id="label_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_en-US">Cash flows from financing activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="label_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:title="label: NetCashProvidedByUsedInFinancingActivitiesAbstract to label_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" use="optional" order="25"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="ProceedsFromIssuanceOfCommonStock" xlink:title="ProceedsFromIssuanceOfCommonStock"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ProceedsFromIssuanceOfCommonStock" xml:lang="en-US" id="label_us-gaap_ProceedsFromIssuanceOfCommonStock_en-US">Net proceeds from issuance of common stock and warrants, including units</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ProceedsFromIssuanceOfCommonStock" xlink:to="label_us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:title="label: ProceedsFromIssuanceOfCommonStock to label_us-gaap_ProceedsFromIssuanceOfCommonStock" use="optional" order="26"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" xlink:label="ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" xlink:title="ProceedsFromIssuanceOfPreferredStockAndPreferenceStock"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" xml:lang="en-US" id="label_us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock_en-US">Net proceeds from issuance of preferred stock and warrants</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" xlink:to="label_us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" xlink:title="label: ProceedsFromIssuanceOfPreferredStockAndPreferenceStock to label_us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock" use="optional" order="27"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_ProceedsFromUnsecuredLinesOfCredit" xlink:label="ProceedsFromUnsecuredLinesOfCredit" xlink:title="ProceedsFromUnsecuredLinesOfCredit"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_ProceedsFromUnsecuredLinesOfCredit" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_ProceedsFromUnsecuredLinesOfCredit" xml:lang="en-US" id="label_us-gaap_ProceedsFromUnsecuredLinesOfCredit_en-US">Proceeds from issuance of notes under line of credit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ProceedsFromUnsecuredLinesOfCredit" xlink:to="label_us-gaap_ProceedsFromUnsecuredLinesOfCredit" xlink:title="label: ProceedsFromUnsecuredLinesOfCredit to label_us-gaap_ProceedsFromUnsecuredLinesOfCredit" use="optional" order="28"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xlink:label="ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xlink:title="ProceedsFromIssuanceOf7NotePayableToFoundingStockholder"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xml:lang="en-US" id="label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder_en-US">Proceeds from issuance of 7% note payable to Founding stockholder</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xlink:to="label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xlink:title="label: ProceedsFromIssuanceOf7NotePayableToFoundingStockholder to label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" use="optional" order="29"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder" xml:lang="en-US" id="documentation_vsta_ProceedsFromIssuanceOf7NotePayableToFoundingStockholder_en-US">Proceeds from issuance of 7% note payable to Founding stockholder</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" xlink:label="NetProceedsFromIssuanceOf7ConvertibleNotes" xlink:title="NetProceedsFromIssuanceOf7ConvertibleNotes"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" xml:lang="en-US" id="label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes_en-US">Net proceeds from issuance of 7% convertible notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetProceedsFromIssuanceOf7ConvertibleNotes" xlink:to="label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" xlink:title="label: NetProceedsFromIssuanceOf7ConvertibleNotes to label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" use="optional" order="30"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes" xml:lang="en-US" id="documentation_vsta_NetProceedsFromIssuanceOf7ConvertibleNotes_en-US">Net proceeds from issuance of 7% convertible notes</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xlink:label="NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xlink:title="NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xml:lang="en-US" id="label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants_en-US">Net proceeds from issuance of 10% convertible notes and warrants</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xlink:to="label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xlink:title="label: NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants to label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" use="optional" order="31"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants" xml:lang="en-US" id="documentation_vsta_NetProceedsFromIssuanceOf10ConvertibleNotesAndWarrants_en-US">Net proceeds from issuance of 10% convertible notes and warrants</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xlink:label="NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xlink:title="NetProceedsFromIssuanceOfPlatinumNotesAndWarrants"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xml:lang="en-US" id="label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants_en-US">Net proceeds from issuance of Platinum Notes and warrants</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xlink:to="label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xlink:title="label: NetProceedsFromIssuanceOfPlatinumNotesAndWarrants to label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" use="optional" order="32"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants" xml:lang="en-US" id="documentation_vsta_NetProceedsFromIssuanceOfPlatinumNotesAndWarrants_en-US">Net proceeds from issuance of Platinum Notes and warrants</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants" xlink:label="NetProceedsFromIssuanceOf20082010NotesAndWarrants" xlink:title="NetProceedsFromIssuanceOf20082010NotesAndWarrants"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants" xml:lang="en-US" id="label_vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants_en-US">Net proceeds from issuance of 2008/2010 Notes and warrants</link:label>
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    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants" xml:lang="en-US" id="documentation_vsta_NetProceedsFromIssuanceOf20082010NotesAndWarrants_en-US">Net proceeds from issuance of 2008/2010 Notes and warrants</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants" xlink:label="NetProceedsFromIssuanceOf20062007NotesAndWarrants" xlink:title="NetProceedsFromIssuanceOf20062007NotesAndWarrants"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants" xml:lang="en-US" id="label_vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants_en-US">Net proceeds from issuance of 2006/2007 Notes and warrants</link:label>
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    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants" xml:lang="en-US" id="documentation_vsta_NetProceedsFromIssuanceOf20062007NotesAndWarrants_en-US">Net proceeds from issuance of 2006/2007 Notes and warrants</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ProceedsFromIssuanceOf7NotesPayable" xlink:label="ProceedsFromIssuanceOf7NotesPayable" xlink:title="ProceedsFromIssuanceOf7NotesPayable"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ProceedsFromIssuanceOf7NotesPayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ProceedsFromIssuanceOf7NotesPayable" xml:lang="en-US" id="label_vsta_ProceedsFromIssuanceOf7NotesPayable_en-US">Proceeds from issuance of 7% notes payable</link:label>
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    <link:label xlink:type="resource" xlink:label="label_vsta_ProceedsFromIssuanceOf7NotesPayable" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ProceedsFromIssuanceOf7NotesPayable" xml:lang="en-US" id="documentation_vsta_ProceedsFromIssuanceOf7NotesPayable_en-US">Proceeds from issuance of 7% notes payable</link:label>
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    <link:label xlink:type="resource" xlink:label="label_vsta_NetProceedsFromIssuanceOfAugust2010ShortTermNotesAndWarrants" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_NetProceedsFromIssuanceOfAugust2010ShortTermNotesAndWarrants" xml:lang="en-US" id="documentation_vsta_NetProceedsFromIssuanceOfAugust2010ShortTermNotesAndWarrants_en-US">Net proceeds from issuance of August 2010 Short- Term Notes and warrants</link:label>
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    <link:label xlink:type="resource" xlink:label="label_us-gaap_RepaymentsOfNotesPayable" xlink:role="http://xbrl.us/us-gaap/role/label/negated" xlink:title="label_us-gaap_RepaymentsOfNotesPayable" xml:lang="en-US" id="negated_us-gaap_RepaymentsOfNotesPayable_en-US">Repayment of notes</link:label>
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    <link:label xlink:type="resource" xlink:label="label_us-gaap_RepaymentsOfNotesPayable" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_RepaymentsOfNotesPayable" xml:lang="en-US" id="label_us-gaap_RepaymentsOfNotesPayable_en-US">Repayment of notes</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="NetCashProvidedByUsedInFinancingActivities" xlink:title="NetCashProvidedByUsedInFinancingActivities"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_NetCashProvidedByUsedInFinancingActivities" xml:lang="en-US" id="totalLabel_us-gaap_NetCashProvidedByUsedInFinancingActivities_en-US">Net cash provided by financing activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NetCashProvidedByUsedInFinancingActivities" xlink:to="label_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:title="label: NetCashProvidedByUsedInFinancingActivities to label_us-gaap_NetCashProvidedByUsedInFinancingActivities" use="optional" order="39"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_NetCashProvidedByUsedInFinancingActivities" xml:lang="en-US" id="label_us-gaap_NetCashProvidedByUsedInFinancingActivities_en-US">Net cash provided by financing activities</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:label="CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:title="CashAndCashEquivalentsPeriodIncreaseDecrease"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:title="label_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xml:lang="en-US" id="totalLabel_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease_en-US">Net increase (decrease) in cash and cash equivalents</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:to="label_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:title="label: CashAndCashEquivalentsPeriodIncreaseDecrease to label_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" use="optional" order="40"/>
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    <link:label xlink:type="resource" xlink:label="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:title="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xml:lang="en-US" id="periodStartLabel_us-gaap_CashAndCashEquivalentsAtCarryingValue_en-US">Cash and cash equivalents at beginning of period</link:label>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:title="label_us-gaap_CashAndCashEquivalentsAtCarryingValue" xml:lang="en-US" id="periodEndLabel_us-gaap_CashAndCashEquivalentsAtCarryingValue_en-US">Cash and cash equivalents at end of period</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_NotesToTheFinancialStatementsAbstract" xlink:label="NotesToTheFinancialStatementsAbstract" xlink:title="NotesToTheFinancialStatementsAbstract"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_NotesToTheFinancialStatementsAbstract" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_NotesToTheFinancialStatementsAbstract" xml:lang="en-US" id="label_vsta_NotesToTheFinancialStatementsAbstract_en-US">Notes to the Financial Statements</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NotesToTheFinancialStatementsAbstract" xlink:to="label_vsta_NotesToTheFinancialStatementsAbstract" xlink:title="label: NotesToTheFinancialStatementsAbstract to label_vsta_NotesToTheFinancialStatementsAbstract" use="optional" order="1"/>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_HistoryAndOrganizationTextBlock" xlink:label="HistoryAndOrganizationTextBlock" xlink:title="HistoryAndOrganizationTextBlock"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_HistoryAndOrganizationTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_HistoryAndOrganizationTextBlock" xml:lang="en-US" id="label_vsta_HistoryAndOrganizationTextBlock_en-US">History and Organization [Text Block]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="HistoryAndOrganizationTextBlock" xlink:to="label_vsta_HistoryAndOrganizationTextBlock" xlink:title="label: HistoryAndOrganizationTextBlock to label_vsta_HistoryAndOrganizationTextBlock" use="optional" order="1"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_HistoryAndOrganizationTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_HistoryAndOrganizationTextBlock" xml:lang="en-US" id="documentation_vsta_HistoryAndOrganizationTextBlock_en-US">History and Organization [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:label="BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:title="BusinessDescriptionAndBasisOfPresentationTextBlock"/>
    <link:label xlink:type="resource" xlink:label="label_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xml:lang="en-US" id="label_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock_en-US">Basis of Presentation and Going Concern [Text Block]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:to="label_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:title="label: BusinessDescriptionAndBasisOfPresentationTextBlock to label_us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" use="optional" order="2"/>
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_SignificantAccountingPoliciesTextBlock" xlink:label="SignificantAccountingPoliciesTextBlock" xlink:title="SignificantAccountingPoliciesTextBlock"/>
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    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd#us-gaap_FairValueMeasurementInputsDisclosureTextBlock" xlink:label="FairValueMeasurementInputsDisclosureTextBlock" xlink:title="FairValueMeasurementInputsDisclosureTextBlock"/>
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    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xlink:label="ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xlink:title="ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xml:lang="en-US" id="label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock_en-US">Convertible Promissory Notes And Other Notes Payable [Text Block]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xlink:to="label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xlink:title="label: ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock to label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" use="optional" order="5"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock" xml:lang="en-US" id="documentation_vsta_ConvertiblePromissoryNotesAndOtherNotesPayableTextBlock_en-US">Convertible Promissory Notes And Other Notes Payable [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_LicensingAndCollaborativeAgreementsTextBlock" xlink:label="LicensingAndCollaborativeAgreementsTextBlock" xlink:title="LicensingAndCollaborativeAgreementsTextBlock"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_LicensingAndCollaborativeAgreementsTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_vsta_LicensingAndCollaborativeAgreementsTextBlock" xml:lang="en-US" id="label_vsta_LicensingAndCollaborativeAgreementsTextBlock_en-US">Licensing And Collaborative Agreements [Text Block]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="LicensingAndCollaborativeAgreementsTextBlock" xlink:to="label_vsta_LicensingAndCollaborativeAgreementsTextBlock" xlink:title="label: LicensingAndCollaborativeAgreementsTextBlock to label_vsta_LicensingAndCollaborativeAgreementsTextBlock" use="optional" order="6"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_LicensingAndCollaborativeAgreementsTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_LicensingAndCollaborativeAgreementsTextBlock" xml:lang="en-US" id="documentation_vsta_LicensingAndCollaborativeAgreementsTextBlock_en-US">Licensing And Collaborative Agreements [Text Block]</link:label>
    <link:loc xlink:type="locator" xlink:href="vsta-20110930.xsd#vsta_CommonStockTextBlock" xlink:label="CommonStockTextBlock" xlink:title="CommonStockTextBlock"/>
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    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CommonStockTextBlock" xlink:to="label_vsta_CommonStockTextBlock" xlink:title="label: CommonStockTextBlock to label_vsta_CommonStockTextBlock" use="optional" order="7"/>
    <link:label xlink:type="resource" xlink:label="label_vsta_CommonStockTextBlock" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:title="label_vsta_CommonStockTextBlock" xml:lang="en-US" id="documentation_vsta_CommonStockTextBlock_en-US">Common Stock [Text Block]</link:label>
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    <link:label xlink:type="resource" xlink:label="label_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:role="http://www.xbrl.org/2003/role/label" xlink:title="label_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xml:lang="en-US" id="label_us-gaap_RelatedPartyTransactionsDisclosureTextBlock_en-US">Related Party Transactions [Text Block]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="RelatedPartyTransactionsDisclosureTextBlock" xlink:to="label_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:title="label: RelatedPartyTransactionsDisclosureTextBlock to label_us-gaap_RelatedPartyTransactionsDisclosureTextBlock" use="optional" order="8"/>
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