

<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<xsd:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.vcel.com/20170331" xmlns:astm="http://www.vcel.com/20170331" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric" xmlns:num="http://www.xbrl.org/dtr/type/numeric" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:import namespace="http://fasb.org/us-gaap/2016-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2016-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2016/elts/us-roles-2016-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-types/2016-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2016/elts/us-types-2016-01-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/arcrole/fact-explanatoryFact" schemaLocation="http://www.xbrl.org/lrr/arcrole/factExplanatory-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/net" schemaLocation="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/country/2016-01-31" schemaLocation="http://xbrl.sec.gov/country/2016/country-2016-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/currency/2016-01-31" schemaLocation="http://xbrl.sec.gov/currency/2016/currency-2016-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2014-01-31" schemaLocation="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/exch/2016-01-31" schemaLocation="http://xbrl.sec.gov/exch/2016/exch-2016-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/invest/2013-01-31" schemaLocation="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/naics/2011-01-31" schemaLocation="http://xbrl.sec.gov/naics/2011/naics-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/sic/2011-01-31" schemaLocation="http://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/stpr/2011-01-31" schemaLocation="http://xbrl.sec.gov/stpr/2011/stpr-2011-01-31.xsd" />
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="astm-20170331_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="astm-20170331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="astm-20170331_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="astm-20170331_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple" />
      <link:roleType id="BasisOfPresentation" roleURI="http://www.vcel.com/role/BasisOfPresentation">
        <link:definition>2102100 - Disclosure - BASIS OF PRESENTATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsAndContingencies" roleURI="http://www.vcel.com/role/CommitmentsAndContingencies">
        <link:definition>2115100 - Disclosure - COMMITMENTS AND CONTINGENCIES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsAndContingenciesDetails" roleURI="http://www.vcel.com/role/CommitmentsAndContingenciesDetails">
        <link:definition>2415402 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsAndContingenciesDetailsCalc2" roleURI="http://www.vcel.com/role/CommitmentsAndContingenciesDetailsCalc2">
        <link:definition>2415402 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsAndContingenciesTables" roleURI="http://www.vcel.com/role/CommitmentsAndContingenciesTables">
        <link:definition>2315301 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsUnaudited" roleURI="http://www.vcel.com/role/CondensedConsolidatedBalanceSheetsUnaudited">
        <link:definition>1001000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsUnauditedCalc2" roleURI="http://www.vcel.com/role/CondensedConsolidatedBalanceSheetsUnauditedCalc2">
        <link:definition>1001000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsUnauditedParenthetical" roleURI="http://www.vcel.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical">
        <link:definition>1001501 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsOfCashFlowsUnaudited" roleURI="http://www.vcel.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited">
        <link:definition>1004000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsOfOperationsUnaudited" roleURI="http://www.vcel.com/role/CondensedConsolidatedStatementsOfOperationsUnaudited">
        <link:definition>1002000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Debt" roleURI="http://www.vcel.com/role/Debt">
        <link:definition>2108100 - Disclosure - DEBT</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtDetails" roleURI="http://www.vcel.com/role/DebtDetails">
        <link:definition>2408401 - Disclosure - DEBT (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DocumentAndEntityInformation" roleURI="http://www.vcel.com/role/DocumentAndEntityInformation">
        <link:definition>0001000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurements" roleURI="http://www.vcel.com/role/FairValueMeasurements">
        <link:definition>2110100 - Disclosure - FAIR VALUE MEASUREMENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsRecurringBasisDetails" roleURI="http://www.vcel.com/role/FairValueMeasurementsRecurringBasisDetails">
        <link:definition>2410402 - Disclosure - FAIR VALUE MEASUREMENTS - RECURRING BASIS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsTables" roleURI="http://www.vcel.com/role/FairValueMeasurementsTables">
        <link:definition>2310301 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerCommonShare" roleURI="http://www.vcel.com/role/NetLossPerCommonShare">
        <link:definition>2113100 - Disclosure - NET LOSS PER COMMON SHARE</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerCommonShareDetails" roleURI="http://www.vcel.com/role/NetLossPerCommonShareDetails">
        <link:definition>2413402 - Disclosure - NET LOSS PER COMMON SHARE (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerCommonShareTables" roleURI="http://www.vcel.com/role/NetLossPerCommonShareTables">
        <link:definition>2313301 - Disclosure - NET LOSS PER COMMON SHARE (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Organization" roleURI="http://www.vcel.com/role/Organization">
        <link:definition>2101100 - Disclosure - ORGANIZATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationDetails" roleURI="http://www.vcel.com/role/OrganizationDetails">
        <link:definition>2401401 - Disclosure - ORGANIZATION (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PreferredStock" roleURI="http://www.vcel.com/role/PreferredStock">
        <link:definition>2112100 - Disclosure - PREFERRED STOCK</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PreferredStockDetails" roleURI="http://www.vcel.com/role/PreferredStockDetails">
        <link:definition>2412401 - Disclosure - PREFERRED STOCK (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RecentAccountingPronouncements" roleURI="http://www.vcel.com/role/RecentAccountingPronouncements">
        <link:definition>2103100 - Disclosure - RECENT ACCOUNTING PRONOUNCEMENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RecentAccountingPronouncementsPolicies" roleURI="http://www.vcel.com/role/RecentAccountingPronouncementsPolicies">
        <link:definition>2203201 - Disclosure - RECENT ACCOUNTING PRONOUNCEMENTS (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Revenue" roleURI="http://www.vcel.com/role/Revenue">
        <link:definition>2114100 - Disclosure - Revenue</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueDetails" roleURI="http://www.vcel.com/role/RevenueDetails">
        <link:definition>2414401 - Disclosure - Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SelectedBalanceSheetComponents" roleURI="http://www.vcel.com/role/SelectedBalanceSheetComponents">
        <link:definition>2105100 - Disclosure - SELECTED BALANCE SHEET COMPONENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SelectedBalanceSheetComponentsAccruedExpensesDetails" roleURI="http://www.vcel.com/role/SelectedBalanceSheetComponentsAccruedExpensesDetails">
        <link:definition>2405404 - Disclosure - SELECTED BALANCE SHEET COMPONENTS - ACCRUED EXPENSES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SelectedBalanceSheetComponentsInventoryDetails" roleURI="http://www.vcel.com/role/SelectedBalanceSheetComponentsInventoryDetails">
        <link:definition>2405402 - Disclosure - SELECTED BALANCE SHEET COMPONENTS - INVENTORY (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SelectedBalanceSheetComponentsPropertyPlantAndEquipmentDetails" roleURI="http://www.vcel.com/role/SelectedBalanceSheetComponentsPropertyPlantAndEquipmentDetails">
        <link:definition>2405403 - Disclosure - SELECTED BALANCE SHEET COMPONENTS - PROPERTY PLANT AND EQUIPMENT (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SelectedBalanceSheetComponentsTables" roleURI="http://www.vcel.com/role/SelectedBalanceSheetComponentsTables">
        <link:definition>2305301 - Disclosure - SELECTED BALANCE SHEET COMPONENTS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquity" roleURI="http://www.vcel.com/role/ShareholdersEquity">
        <link:definition>2111100 - Disclosure - SHAREHOLDERS' EQUITY</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ShareholdersEquityDetails" roleURI="http://www.vcel.com/role/ShareholdersEquityDetails">
        <link:definition>2411401 - Disclosure - SHAREHOLDERS' EQUITY (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensation" roleURI="http://www.vcel.com/role/StockBasedCompensation">
        <link:definition>2109100 - Disclosure - STOCK-BASED COMPENSATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationDetails" roleURI="http://www.vcel.com/role/StockBasedCompensationDetails">
        <link:definition>2409402 - Disclosure - STOCK-BASED COMPENSATION (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationTables" roleURI="http://www.vcel.com/role/StockBasedCompensationTables">
        <link:definition>2309301 - Disclosure - STOCK-BASED COMPENSATION (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockPurchaseWarrants" roleURI="http://www.vcel.com/role/StockPurchaseWarrants">
        <link:definition>2107100 - Disclosure - STOCK PURCHASE WARRANTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockPurchaseWarrantsDetails" roleURI="http://www.vcel.com/role/StockPurchaseWarrantsDetails">
        <link:definition>2407402 - Disclosure - STOCK PURCHASE WARRANTS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockPurchaseWarrantsTables" roleURI="http://www.vcel.com/role/StockPurchaseWarrantsTables">
        <link:definition>2307301 - Disclosure - STOCK PURCHASE WARRANTS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SubsequentEvents" roleURI="http://www.vcel.com/role/SubsequentEvents">
        <link:definition>2117100 - Disclosure - SUBSEQUENT EVENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SubsequentEventsDetails" roleURI="http://www.vcel.com/role/SubsequentEventsDetails">
        <link:definition>2417401 - Disclosure - SUBSEQUENT EVENTS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element id="astm_AccumulatedUndeclaredDividendsShares" name="AccumulatedUndeclaredDividendsShares" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="instant" />
  <xsd:element id="astm_AtTheMarketSalesAgreementMaximumAggregateProceeds" name="AtTheMarketSalesAgreementMaximumAggregateProceeds" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_AtTheMarketSalesAgreementProceedsFromIssuanceOfCommonStock" name="AtTheMarketSalesAgreementProceedsFromIssuanceOfCommonStock" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="astm_AttheMarketSalesAgreementSharesIssued" name="AttheMarketSalesAgreementSharesIssued" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_BASISOFPRESENTATION" name="BASISOFPRESENTATION" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_CellTherapyAndRegenerativeMedicineBusinessMember" name="CellTherapyAndRegenerativeMedicineBusinessMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ClassofWarrantorRightNumberofHolders" name="ClassofWarrantorRightNumberofHolders" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="astm_ClassofWarrantorRightWarrantsIssued" name="ClassofWarrantorRightWarrantsIssued" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_CommonStockRemainingCapacity" name="CommonStockRemainingCapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="astm_CovenantPeriodAxis" name="CovenantPeriodAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_CovenantPeriodDomain" name="CovenantPeriodDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_CowenandCompanyLLCMember" name="CowenandCompanyLLCMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_DebtFinancingAgreementMaximumBorrowingCapacity" name="DebtFinancingAgreementMaximumBorrowingCapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="astm_DebtFinancingAgreementMember" name="DebtFinancingAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_DebtInstrumentNumberofInstallments" name="DebtInstrumentNumberofInstallments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="astm_December312017Member" name="December312017Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_DepreciationDepletionandAmortizationExcludingIntangibleAssets" name="DepreciationDepletionandAmortizationExcludingIntangibleAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_InnovativeCellularTherapeuticsMember" name="InnovativeCellularTherapeuticsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_LicenseAgreementContingentConsiderationAsset" name="LicenseAgreementContingentConsiderationAsset" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="astm_LicenseAgreementContingentConsiderationLiability" name="LicenseAgreementContingentConsiderationLiability" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_LicenseAgreementDaysWithinEffectiveDateOfAgreementInitialPaymentDue" name="LicenseAgreementDaysWithinEffectiveDateOfAgreementInitialPaymentDue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_LicenseAgreementInitialPayment" name="LicenseAgreementInitialPayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="astm_LineofCreditFacilityMinimumRevenueCovenant" name="LineofCreditFacilityMinimumRevenueCovenant" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_LineofCreditandTermLoanCreditAgreementCurrentNetofDeferredCosts" name="LineofCreditandTermLoanCreditAgreementCurrentNetofDeferredCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_NumberOfPatentsAndPatentApplicationsAcquired" name="NumberOfPatentsAndPatentApplicationsAcquired" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="astm_OneThirdPartyCustomerInUSMember" name="OneThirdPartyCustomerInUSMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OperatingLeasesLeasedOfficeSpaceFutureMinimumPaymentsDueAbstract" name="OperatingLeasesLeasedOfficeSpaceFutureMinimumPaymentsDueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OperatingLeasesSalesForceLeasedAutoFleetFutureMinimumPaymentsDueAbstract" name="OperatingLeasesSalesForceLeasedAutoFleetFutureMinimumPaymentsDueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDue" name="OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueCurrent" name="OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueInFourYears" name="OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueInFourYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueInThreeYears" name="OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueInThreeYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueInTwoYears" name="OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueInTwoYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueThereafter" name="OperatingandCapitalLeasesandPurchaseCommitmentsFutureMinimumPaymentsDueThereafter" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="astm_OrganizationConsolidationAndPresentationOfFinancialStatementsLineItems" name="OrganizationConsolidationAndPresentationOfFinancialStatementsLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OrganizationConsolidationAndPresentationOfFinancialStatementsTable" name="OrganizationConsolidationAndPresentationOfFinancialStatementsTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_PercentageOfGrossProceedsPayableAsCommission" name="PercentageOfGrossProceedsPayableAsCommission" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_PreferredClassAAndClassBMember" name="PreferredClassAAndClassBMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ScheduleOfChangeInEstimatedFairValueOfWarrantLiabilitiesTableTextBlock" name="ScheduleOfChangeInEstimatedFairValueOfWarrantLiabilitiesTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ScheduleOfClassOfWarrantOrRightValuationAssumptionsTableTextBlock" name="ScheduleOfClassOfWarrantOrRightValuationAssumptionsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_SiliconValleyBankMember" name="SiliconValleyBankMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_TermLoanMember" name="TermLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ValuationAllowancesAndReservesPeriodAxis" name="ValuationAllowancesAndReservesPeriodAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ValuationAllowancesAndReservesPeriodDomain" name="ValuationAllowancesAndReservesPeriodDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ValuationAllowancesAndReservesPeriodRelatedTo2016Member" name="ValuationAllowancesAndReservesPeriodRelatedTo2016Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ValuationAllowancesAndReservesPeriodRelatedTo2017Member" name="ValuationAllowancesAndReservesPeriodRelatedTo2017Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_WarrantsAndRightsNoteDisclosureTextBlock" name="WarrantsAndRightsNoteDisclosureTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_WarrantsAndRightsRollForward" name="WarrantsAndRightsRollForward" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_WarrantsIssuedInAugust2013Member" name="WarrantsIssuedInAugust2013Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_WarrantsIssuedInSeptember2016Member" name="WarrantsIssuedInSeptember2016Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>