Blood-forming Stem Cells Fail To Repair Heart Muscle

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日期: 2004-03-23 今日/总浏览: 1/493
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; J9 F* L0 C' V9 L  Q9 xAnewstudyaddsatwisttotheongoingdebateoverusingblood-formingstemcellstorepairheartmuscle.IntheMarch21onlineissueofNature,researchersattheStanfordUniversitySchoolofMedicinereportthatthecellsareunabletoreplaceheartmuscleafteraheartattack,whichrefutesearlierfindings.6 T1 ~7 [* e+ \$ K6 Q$ U( [  m6 B( ?& M
Duringthepastthreeyears,severalgroupshadreportedthatstemcellsfoundinbonemarrowcouldlodgeintheheartandrepairmuscledamagedbyaheartattack.Thesestemcellsnormallyresideinthebonemarrow,wheretheyconstantlyreplenishredbloodcellsandimmunecells.Iftheearlierfindingswerecorrectandtheblood-formingstemcellsswitchedtheirfates,thatcouldrevealanexcitingnewpathfortreatingheartattackpatients.
4 {$ o0 y  h$ x+ a7 v/ K6 O% YWestartedoutattemptingtovalidateandextendthosefindings,saidLeoraBalsam,MD,aresearchfellowworkingwithRobertRobbins,MD,associateprofessorofcardiothoracicsurgery.+ x0 y1 X6 Y& d1 Y, b' y" B
Insteadofsupportingpreviousfindings,however,herexperimentscontradictedthem.Shefoundthatinmice,blood-formingstemcellslodgeindamagedheartsbutretaintheformofbloodcellsratherthantransformingintomusclecells.ApaperbyanotherresearchgroupinthesameissueofNaturesupportsBalsam’sfindingsusingslightlydifferentmethods.
  L. h4 u) n0 @1 bThequestionnowiswhysomestudieshavefoundthatblood-formingstemcellscanrepairtheheartwhileothersshowthatthoseadultstemcellsretaintheirblood-formingfate.Thequestionisparticularlytimelygiventhathumantrialsarealreadyunderwaybasedonthestrengthofearlierfindingsrefutedbythenewresearch.
3 V6 M: E* J( gIfwearedeliveringbonemarrowtopatientswiththeexpectationthatitwillregeneratetheheart,thatmaynotberealistic,Balsamsaid.
: B- H) y  w! e, C  c9 wOnedifferencebetweenBalsam’sstudyandpreviousexperimentsisthetypeofbonemarrowcellssheused.AmyWagers,PhD,apostdoctoralscholarinthelabofIrvingWeissman,MD,theKarelandAviceBeekhuisProfessorofCancerBiology,tookwholebonemarrowfrommicethenisolatedseveralpurifiedgroupsofcells,includingahighlypurifiedsubsetofstemcellsthatcangoontoformallbloodcelltypes.Previousexperimentshadonlyusedlesspurifiedcells.
/ {, T5 t$ c% j7 uBalsaminjectedthosecellsdirectlyintotheheartmuscleof23miceinwhichshehadinducedaheartattack.Theinjectedcellsproducedagreenproteinthatiseasilyvisibleunderamicroscope.Shethenexaminedtheheartmusclesofthosemice10daysand30daysaftertheinjectiontosearchforsignsoftransplantedblood-formingstemcells.7 }0 U( I0 @' k6 l
At10daysshesawclustersofgreencells,butnoneofthemmadeproteinstypicalofheartmuscle.However,thegreencellsdidproduceproteinscommonlymadebybloodcells.By30days,veryfewgreencellsremainedintheheart,andthosethatdidstillproducedbloodproteinsratherthanheartmuscleproteins.+ E) _/ B  c: y8 V; T
Balsamfoundthat30daysafterinjectingtheblood-formingstemcells,themicediedatthesamerateasthoseinanothergroupthatreceivedonlywateraftertheirinducedheartattacks.Eventhoughthetransplantedstemcellsdidn’thelpthemicesurvive,thestemcell-injectedgroupdidhaveslightimprovementsinhowwelltheirheartspumpedblood.
' v0 s. A' b7 A% G7 bRobbins,whoisleadauthorofthestudy,saidevenwiththeseresults,adultstemcellsmayoffersomepotentialfortreatingdamagedhearts.Maybethesecellsdon’tneedtodifferentiate,hesaid.
+ h, r- M6 t0 A, p1 \1 ^Robbinssaidthetransplantedblood-formingcellsmayrecruitnewbloodvesselstothedamagedtissues.Thesenewbloodvesselsmaykeepheartmusclecellsalivethatwouldotherwisehavedied,thusindirectlyrescuingtheheart.Bygeneticallyengineeringthosecellstomakeadditionalfactorstorecruitbloodvessels,theymaybecomepartofasuccessfultherapy,Robbinssaid.1 ~; \* R; y2 W; e" q8 a/ ^9 y" t
Researchersarealsoexaminingembryonicstemcellsandimmatureskeletalmusclecellsaspossiblecandidatesforrepairingheartmuscle.Robbinsandothermembersofhislabarelookingintothesealternativewaysofrepairingheartmuscle.
4 u0 P+ h: w' D) `% C' g8 BWe’reallinterestedinfindingwaysofregeneratingtheheart,Balsamsaid.Ithinkwhatthisstudypointsoutisthatit’snoteasy.$ ~4 n  v% y1 K% G  k

! Q; F) P3 q3 ^$ n0 ]* j& e6 i科学家研究发现干细胞可能无法修复受损心脏http://www.biotech.org.cn/news/news/show.php?id=13226& n  F' x% K( f- q, n
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" N& t. q* U) U/ c& H# a) u* k  H, Q来源: Stanford University Medical Center
. Q& d  P! H3 W: O+ J发布者: 亦云