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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Anewstudyaddsatwisttotheongoingdebateoverusingblood-formingstemcellstorepairheartmuscle.IntheMarch21onlineissueofNature,researchersattheStanfordUniversitySchoolofMedicinereportthatthecellsareunabletoreplaceheartmuscleafteraheartattack,whichrefutesearlierfindings.
* z- [9 G. Q0 e# j# ^' u# H1 }3 _Duringthepastthreeyears,severalgroupshadreportedthatstemcellsfoundinbonemarrowcouldlodgeintheheartandrepairmuscledamagedbyaheartattack.Thesestemcellsnormallyresideinthebonemarrow,wheretheyconstantlyreplenishredbloodcellsandimmunecells.Iftheearlierfindingswerecorrectandtheblood-formingstemcellsswitchedtheirfates,thatcouldrevealanexcitingnewpathfortreatingheartattackpatients.
5 k1 j: e+ [/ z& L% L; zWestartedoutattemptingtovalidateandextendthosefindings,saidLeoraBalsam,MD,aresearchfellowworkingwithRobertRobbins,MD,associateprofessorofcardiothoracicsurgery.' m* u4 y6 D& C: ?+ V
Insteadofsupportingpreviousfindings,however,herexperimentscontradictedthem.Shefoundthatinmice,blood-formingstemcellslodgeindamagedheartsbutretaintheformofbloodcellsratherthantransformingintomusclecells.ApaperbyanotherresearchgroupinthesameissueofNaturesupportsBalsam’sfindingsusingslightlydifferentmethods.- x8 `" b1 {- g+ q. o' C) p
Thequestionnowiswhysomestudieshavefoundthatblood-formingstemcellscanrepairtheheartwhileothersshowthatthoseadultstemcellsretaintheirblood-formingfate.Thequestionisparticularlytimelygiventhathumantrialsarealreadyunderwaybasedonthestrengthofearlierfindingsrefutedbythenewresearch.% Z9 B" W3 Z" B! ]) a, z
Ifwearedeliveringbonemarrowtopatientswiththeexpectationthatitwillregeneratetheheart,thatmaynotberealistic,Balsamsaid.
0 c! r; q5 B5 y; [OnedifferencebetweenBalsam’sstudyandpreviousexperimentsisthetypeofbonemarrowcellssheused.AmyWagers,PhD,apostdoctoralscholarinthelabofIrvingWeissman,MD,theKarelandAviceBeekhuisProfessorofCancerBiology,tookwholebonemarrowfrommicethenisolatedseveralpurifiedgroupsofcells,includingahighlypurifiedsubsetofstemcellsthatcangoontoformallbloodcelltypes.Previousexperimentshadonlyusedlesspurifiedcells.: N9 ~0 S5 M7 }% Y$ L  T! s% x5 D
Balsaminjectedthosecellsdirectlyintotheheartmuscleof23miceinwhichshehadinducedaheartattack.Theinjectedcellsproducedagreenproteinthatiseasilyvisibleunderamicroscope.Shethenexaminedtheheartmusclesofthosemice10daysand30daysaftertheinjectiontosearchforsignsoftransplantedblood-formingstemcells.
' l. A8 {# x8 X' d( Y; nAt10daysshesawclustersofgreencells,butnoneofthemmadeproteinstypicalofheartmuscle.However,thegreencellsdidproduceproteinscommonlymadebybloodcells.By30days,veryfewgreencellsremainedintheheart,andthosethatdidstillproducedbloodproteinsratherthanheartmuscleproteins.6 {4 K, f$ c8 e* g6 a! k
Balsamfoundthat30daysafterinjectingtheblood-formingstemcells,themicediedatthesamerateasthoseinanothergroupthatreceivedonlywateraftertheirinducedheartattacks.Eventhoughthetransplantedstemcellsdidn’thelpthemicesurvive,thestemcell-injectedgroupdidhaveslightimprovementsinhowwelltheirheartspumpedblood.
! s- {& ~; k' N4 _/ q& URobbins,whoisleadauthorofthestudy,saidevenwiththeseresults,adultstemcellsmayoffersomepotentialfortreatingdamagedhearts.Maybethesecellsdon’tneedtodifferentiate,hesaid.
" X6 `5 ]5 m& gRobbinssaidthetransplantedblood-formingcellsmayrecruitnewbloodvesselstothedamagedtissues.Thesenewbloodvesselsmaykeepheartmusclecellsalivethatwouldotherwisehavedied,thusindirectlyrescuingtheheart.Bygeneticallyengineeringthosecellstomakeadditionalfactorstorecruitbloodvessels,theymaybecomepartofasuccessfultherapy,Robbinssaid.1 r: k6 B. \- L1 l8 J* p6 c; Y
Researchersarealsoexaminingembryonicstemcellsandimmatureskeletalmusclecellsaspossiblecandidatesforrepairingheartmuscle.Robbinsandothermembersofhislabarelookingintothesealternativewaysofrepairingheartmuscle.
, c% l! T  b; @, TWe’reallinterestedinfindingwaysofregeneratingtheheart,Balsamsaid.Ithinkwhatthisstudypointsoutisthatit’snoteasy.) u" j6 _- I0 M2 {
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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
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4 I2 V2 }3 Y1 p. y: O0 R% c作者:
# p. x  K1 t. i' D  V来源: Stanford University Medical Center
3 ^! K8 ^+ c9 \' E# i- |; Y  _发布者: 亦云