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日期: 2004-03-23 今日/总浏览: 1/493$ U4 q2 C, `3 o4 V
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Anewstudyaddsatwisttotheongoingdebateoverusingblood-formingstemcellstorepairheartmuscle.IntheMarch21onlineissueofNature,researchersattheStanfordUniversitySchoolofMedicinereportthatthecellsareunabletoreplaceheartmuscleafteraheartattack,whichrefutesearlierfindings.* E: w' n' s/ L3 q/ S7 y
Duringthepastthreeyears,severalgroupshadreportedthatstemcellsfoundinbonemarrowcouldlodgeintheheartandrepairmuscledamagedbyaheartattack.Thesestemcellsnormallyresideinthebonemarrow,wheretheyconstantlyreplenishredbloodcellsandimmunecells.Iftheearlierfindingswerecorrectandtheblood-formingstemcellsswitchedtheirfates,thatcouldrevealanexcitingnewpathfortreatingheartattackpatients.
- r# H8 F6 b* @Westartedoutattemptingtovalidateandextendthosefindings,saidLeoraBalsam,MD,aresearchfellowworkingwithRobertRobbins,MD,associateprofessorofcardiothoracicsurgery./ u! x% A: |! A% H) ^. P; W
Insteadofsupportingpreviousfindings,however,herexperimentscontradictedthem.Shefoundthatinmice,blood-formingstemcellslodgeindamagedheartsbutretaintheformofbloodcellsratherthantransformingintomusclecells.ApaperbyanotherresearchgroupinthesameissueofNaturesupportsBalsam’sfindingsusingslightlydifferentmethods.# ]" L9 P# t7 ~$ c7 J
Thequestionnowiswhysomestudieshavefoundthatblood-formingstemcellscanrepairtheheartwhileothersshowthatthoseadultstemcellsretaintheirblood-formingfate.Thequestionisparticularlytimelygiventhathumantrialsarealreadyunderwaybasedonthestrengthofearlierfindingsrefutedbythenewresearch.
, P! q1 K9 Y) A; NIfwearedeliveringbonemarrowtopatientswiththeexpectationthatitwillregeneratetheheart,thatmaynotberealistic,Balsamsaid.
* B+ M+ F0 B, T9 F2 mOnedifferencebetweenBalsam’sstudyandpreviousexperimentsisthetypeofbonemarrowcellssheused.AmyWagers,PhD,apostdoctoralscholarinthelabofIrvingWeissman,MD,theKarelandAviceBeekhuisProfessorofCancerBiology,tookwholebonemarrowfrommicethenisolatedseveralpurifiedgroupsofcells,includingahighlypurifiedsubsetofstemcellsthatcangoontoformallbloodcelltypes.Previousexperimentshadonlyusedlesspurifiedcells. j& G1 b% T4 e' N
Balsaminjectedthosecellsdirectlyintotheheartmuscleof23miceinwhichshehadinducedaheartattack.Theinjectedcellsproducedagreenproteinthatiseasilyvisibleunderamicroscope.Shethenexaminedtheheartmusclesofthosemice10daysand30daysaftertheinjectiontosearchforsignsoftransplantedblood-formingstemcells.
z: F6 }4 u1 b4 @2 G# F9 Y! LAt10daysshesawclustersofgreencells,butnoneofthemmadeproteinstypicalofheartmuscle.However,thegreencellsdidproduceproteinscommonlymadebybloodcells.By30days,veryfewgreencellsremainedintheheart,andthosethatdidstillproducedbloodproteinsratherthanheartmuscleproteins.
' q$ K1 `6 N2 D. V6 wBalsamfoundthat30daysafterinjectingtheblood-formingstemcells,themicediedatthesamerateasthoseinanothergroupthatreceivedonlywateraftertheirinducedheartattacks.Eventhoughthetransplantedstemcellsdidn’thelpthemicesurvive,thestemcell-injectedgroupdidhaveslightimprovementsinhowwelltheirheartspumpedblood.3 h R: x& a: ^ _
Robbins,whoisleadauthorofthestudy,saidevenwiththeseresults,adultstemcellsmayoffersomepotentialfortreatingdamagedhearts.Maybethesecellsdon’tneedtodifferentiate,hesaid.
/ Y$ D& ^' k- T. ^! T& U& V4 O7 H" q5 ~ jRobbinssaidthetransplantedblood-formingcellsmayrecruitnewbloodvesselstothedamagedtissues.Thesenewbloodvesselsmaykeepheartmusclecellsalivethatwouldotherwisehavedied,thusindirectlyrescuingtheheart.Bygeneticallyengineeringthosecellstomakeadditionalfactorstorecruitbloodvessels,theymaybecomepartofasuccessfultherapy,Robbinssaid.
) ^0 `, T% J# L0 eResearchersarealsoexaminingembryonicstemcellsandimmatureskeletalmusclecellsaspossiblecandidatesforrepairingheartmuscle.Robbinsandothermembersofhislabarelookingintothesealternativewaysofrepairingheartmuscle.
8 `( V: C2 V' i% f4 f% w* nWe’reallinterestedinfindingwaysofregeneratingtheheart,Balsamsaid.Ithinkwhatthisstudypointsoutisthatit’snoteasy.* ~2 c8 L* E C: {6 g
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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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" B6 \$ y* Y6 o4 S作者: . n! k& }0 i! P4 s# n( `. q) D j
来源: Stanford University Medical Center
5 B* E8 y9 u3 N* g$ z$ U8 r0 X5 t发布者: 亦云 |
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发表于 2008-12-31 09:04
