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标题: Blood-forming Stem Cells Fail To Repair Heart Muscle [打印本页]

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作者: bobo    时间: 2008-12-31 09:04     标题: Blood-forming Stem Cells Fail To Repair Heart Muscle

日期: 2004-03-23 今日/总浏览: 1/493
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9 G4 E: b! {0 ]/ S/ UAnewstudyaddsatwisttotheongoingdebateoverusingblood-formingstemcellstorepairheartmuscle.IntheMarch21onlineissueofNature,researchersattheStanfordUniversitySchoolofMedicinereportthatthecellsareunabletoreplaceheartmuscleafteraheartattack,whichrefutesearlierfindings.
) y  U2 ?1 h3 F! B, rDuringthepastthreeyears,severalgroupshadreportedthatstemcellsfoundinbonemarrowcouldlodgeintheheartandrepairmuscledamagedbyaheartattack.Thesestemcellsnormallyresideinthebonemarrow,wheretheyconstantlyreplenishredbloodcellsandimmunecells.Iftheearlierfindingswerecorrectandtheblood-formingstemcellsswitchedtheirfates,thatcouldrevealanexcitingnewpathfortreatingheartattackpatients.
3 Y4 v8 v' B, E) w& D% g  DWestartedoutattemptingtovalidateandextendthosefindings,saidLeoraBalsam,MD,aresearchfellowworkingwithRobertRobbins,MD,associateprofessorofcardiothoracicsurgery.2 I4 h+ C, u, G7 [  t5 Q
Insteadofsupportingpreviousfindings,however,herexperimentscontradictedthem.Shefoundthatinmice,blood-formingstemcellslodgeindamagedheartsbutretaintheformofbloodcellsratherthantransformingintomusclecells.ApaperbyanotherresearchgroupinthesameissueofNaturesupportsBalsam’sfindingsusingslightlydifferentmethods.
) X+ B: ?! M1 o0 ^  s, y, b" mThequestionnowiswhysomestudieshavefoundthatblood-formingstemcellscanrepairtheheartwhileothersshowthatthoseadultstemcellsretaintheirblood-formingfate.Thequestionisparticularlytimelygiventhathumantrialsarealreadyunderwaybasedonthestrengthofearlierfindingsrefutedbythenewresearch.
( X( L' a! T$ @3 uIfwearedeliveringbonemarrowtopatientswiththeexpectationthatitwillregeneratetheheart,thatmaynotberealistic,Balsamsaid." D) y3 {$ n2 b% a, Z$ r
OnedifferencebetweenBalsam’sstudyandpreviousexperimentsisthetypeofbonemarrowcellssheused.AmyWagers,PhD,apostdoctoralscholarinthelabofIrvingWeissman,MD,theKarelandAviceBeekhuisProfessorofCancerBiology,tookwholebonemarrowfrommicethenisolatedseveralpurifiedgroupsofcells,includingahighlypurifiedsubsetofstemcellsthatcangoontoformallbloodcelltypes.Previousexperimentshadonlyusedlesspurifiedcells./ G4 ~; T# f- x. V/ p+ o% v
Balsaminjectedthosecellsdirectlyintotheheartmuscleof23miceinwhichshehadinducedaheartattack.Theinjectedcellsproducedagreenproteinthatiseasilyvisibleunderamicroscope.Shethenexaminedtheheartmusclesofthosemice10daysand30daysaftertheinjectiontosearchforsignsoftransplantedblood-formingstemcells.! |/ c' d5 H8 Y2 E( C
At10daysshesawclustersofgreencells,butnoneofthemmadeproteinstypicalofheartmuscle.However,thegreencellsdidproduceproteinscommonlymadebybloodcells.By30days,veryfewgreencellsremainedintheheart,andthosethatdidstillproducedbloodproteinsratherthanheartmuscleproteins.5 C) c7 X" B- [
Balsamfoundthat30daysafterinjectingtheblood-formingstemcells,themicediedatthesamerateasthoseinanothergroupthatreceivedonlywateraftertheirinducedheartattacks.Eventhoughthetransplantedstemcellsdidn’thelpthemicesurvive,thestemcell-injectedgroupdidhaveslightimprovementsinhowwelltheirheartspumpedblood.
' |5 B% ?7 _* e  f/ F+ WRobbins,whoisleadauthorofthestudy,saidevenwiththeseresults,adultstemcellsmayoffersomepotentialfortreatingdamagedhearts.Maybethesecellsdon’tneedtodifferentiate,hesaid.7 U; ]$ f* t. t& @) {
Robbinssaidthetransplantedblood-formingcellsmayrecruitnewbloodvesselstothedamagedtissues.Thesenewbloodvesselsmaykeepheartmusclecellsalivethatwouldotherwisehavedied,thusindirectlyrescuingtheheart.Bygeneticallyengineeringthosecellstomakeadditionalfactorstorecruitbloodvessels,theymaybecomepartofasuccessfultherapy,Robbinssaid.
7 s3 i4 x( j1 ]' cResearchersarealsoexaminingembryonicstemcellsandimmatureskeletalmusclecellsaspossiblecandidatesforrepairingheartmuscle.Robbinsandothermembersofhislabarelookingintothesealternativewaysofrepairingheartmuscle.: z7 z( p+ C$ ^
We’reallinterestedinfindingwaysofregeneratingtheheart,Balsamsaid.Ithinkwhatthisstudypointsoutisthatit’snoteasy.
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% [, |. |7 ?6 e, P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) ]8 a" I+ R5 V# g
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来源: Stanford University Medical Center
; x6 q7 C; a' l  R发布者: 亦云

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