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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: }1 a9 F: R" R, @! r' Z: r' WAnewstudyaddsatwisttotheongoingdebateoverusingblood-formingstemcellstorepairheartmuscle.IntheMarch21onlineissueofNature,researchersattheStanfordUniversitySchoolofMedicinereportthatthecellsareunabletoreplaceheartmuscleafteraheartattack,whichrefutesearlierfindings.
9 U% B5 X' r6 r+ _Duringthepastthreeyears,severalgroupshadreportedthatstemcellsfoundinbonemarrowcouldlodgeintheheartandrepairmuscledamagedbyaheartattack.Thesestemcellsnormallyresideinthebonemarrow,wheretheyconstantlyreplenishredbloodcellsandimmunecells.Iftheearlierfindingswerecorrectandtheblood-formingstemcellsswitchedtheirfates,thatcouldrevealanexcitingnewpathfortreatingheartattackpatients.) v/ v4 m3 h, H6 V
Westartedoutattemptingtovalidateandextendthosefindings,saidLeoraBalsam,MD,aresearchfellowworkingwithRobertRobbins,MD,associateprofessorofcardiothoracicsurgery.
2 R8 U4 W. x* Z+ A/ }Insteadofsupportingpreviousfindings,however,herexperimentscontradictedthem.Shefoundthatinmice,blood-formingstemcellslodgeindamagedheartsbutretaintheformofbloodcellsratherthantransformingintomusclecells.ApaperbyanotherresearchgroupinthesameissueofNaturesupportsBalsam’sfindingsusingslightlydifferentmethods.; U9 I; z6 K, g, c5 M' p
Thequestionnowiswhysomestudieshavefoundthatblood-formingstemcellscanrepairtheheartwhileothersshowthatthoseadultstemcellsretaintheirblood-formingfate.Thequestionisparticularlytimelygiventhathumantrialsarealreadyunderwaybasedonthestrengthofearlierfindingsrefutedbythenewresearch.2 N+ e4 v  y& a& o6 x! D% o
Ifwearedeliveringbonemarrowtopatientswiththeexpectationthatitwillregeneratetheheart,thatmaynotberealistic,Balsamsaid.
6 _+ f: J! H; BOnedifferencebetweenBalsam’sstudyandpreviousexperimentsisthetypeofbonemarrowcellssheused.AmyWagers,PhD,apostdoctoralscholarinthelabofIrvingWeissman,MD,theKarelandAviceBeekhuisProfessorofCancerBiology,tookwholebonemarrowfrommicethenisolatedseveralpurifiedgroupsofcells,includingahighlypurifiedsubsetofstemcellsthatcangoontoformallbloodcelltypes.Previousexperimentshadonlyusedlesspurifiedcells.; J# K; k/ J; \3 D' K. T% I
Balsaminjectedthosecellsdirectlyintotheheartmuscleof23miceinwhichshehadinducedaheartattack.Theinjectedcellsproducedagreenproteinthatiseasilyvisibleunderamicroscope.Shethenexaminedtheheartmusclesofthosemice10daysand30daysaftertheinjectiontosearchforsignsoftransplantedblood-formingstemcells.
, L; M. O& f% e9 {9 v8 s2 W$ ZAt10daysshesawclustersofgreencells,butnoneofthemmadeproteinstypicalofheartmuscle.However,thegreencellsdidproduceproteinscommonlymadebybloodcells.By30days,veryfewgreencellsremainedintheheart,andthosethatdidstillproducedbloodproteinsratherthanheartmuscleproteins.& R7 e# [8 {& A# k: q
Balsamfoundthat30daysafterinjectingtheblood-formingstemcells,themicediedatthesamerateasthoseinanothergroupthatreceivedonlywateraftertheirinducedheartattacks.Eventhoughthetransplantedstemcellsdidn’thelpthemicesurvive,thestemcell-injectedgroupdidhaveslightimprovementsinhowwelltheirheartspumpedblood.
, h4 c- E: f8 `2 }/ T  HRobbins,whoisleadauthorofthestudy,saidevenwiththeseresults,adultstemcellsmayoffersomepotentialfortreatingdamagedhearts.Maybethesecellsdon’tneedtodifferentiate,hesaid.
. m: v% U7 X: u" M% K/ DRobbinssaidthetransplantedblood-formingcellsmayrecruitnewbloodvesselstothedamagedtissues.Thesenewbloodvesselsmaykeepheartmusclecellsalivethatwouldotherwisehavedied,thusindirectlyrescuingtheheart.Bygeneticallyengineeringthosecellstomakeadditionalfactorstorecruitbloodvessels,theymaybecomepartofasuccessfultherapy,Robbinssaid." [, _# V( {- M: H  w
Researchersarealsoexaminingembryonicstemcellsandimmatureskeletalmusclecellsaspossiblecandidatesforrepairingheartmuscle.Robbinsandothermembersofhislabarelookingintothesealternativewaysofrepairingheartmuscle.0 I! Z; n' f" G
We’reallinterestedinfindingwaysofregeneratingtheheart,Balsamsaid.Ithinkwhatthisstudypointsoutisthatit’snoteasy.
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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( B9 H; i- ^% a5 t# Q. j
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作者: / e, L, h3 ]$ y) Z  t8 m: t& L
来源: Stanford University Medical Center
/ ~+ v" u5 @  E+ U$ {) B1 L发布者: 亦云