Stem Cells Found In Adults May Repair Nerves

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日期: 2004-02-18 今日/总浏览: 1/336  h2 _" @& P- t* {/ C" K6 z

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Itusedtobeconsidereddogmathatanerve,onceinjured,couldneverberepaired.Now,researchershavelearnedthatsomenerves,evennervesinpartsofthebrain,canregenerateorbereplaced.Bystudyingthechemicalsignalsthatencourageorimpedetherepairofnerves,researchersattheUniversityofWashington,theSalkInstitute,andotherinstitutionsmaycontributetoeventualtreatmentsforinjuredspinesanddiseasedretinas,accordingtoapresentationattheannualmeetingoftheAmericanAssociationfortheAdvancementofScience(AAAS).
) v; o) w# n8 A5 {  b2 S. AMuchofthisresearchfocusesonstemcells,oneofseveraltypesofgeneralcellsthatcangiverisetospecializedcells,likeneurons.Itwasoncethoughtthathumanstemcellswereonlyfoundinembryos,andinbonemarrow,wheretheyproducebloodcells.Butstemcellsarealsobeingfoundinadults,includingthebrainandtheeye.Forexample,stemscellssteadilyreplacedeadneuronsintheolfactorybulb,whichtransmitsscentsignalstothebrain,andthehippocampaldentategyrus,anareathatorganizesshort-termmemory.  p8 o& Z  n& D( y
However,thepaceofstem-cellrepairsinhumansisslow.Andinsomecases,stemcellscanevenimpedehealing.Stemcellsinaninjuredspinalcordcancreateastickyscarthatblocksnerveregeneration,accordingtoDr.PhilipHorner,anassistantprofessorintheDepartmentofNeurosurgeryintheUWSchoolofMedicine.5 J% `  u7 d+ Q# z
We’vefoundthattheaxons,thepartsofthenervesthattransmitsignals,trytoregenerateafteraninjurybutgetcaughtinthescar.It’slikethey’restuckinthemud,Hornersaid.We’restudyingwaysthatthisprocessisregulatedtoseeifitcanbemanipulatedtopromotehealing.Inotherwords,we’relookingatwaystogettheaxonsoutofthemud.Onewayistomakethemudlessstickybymanipulatingstemcellsthatparticipateinscarformation.Anotheristostimulatetheaxonstopushthroughthescarbyprovidingthecutnerveswithmoleculesthatinduceelongation.We’reusingmolecularsignalscalledgrowthfactorstosimulatethegrowthofculturednervecellsinthelaboratory.
9 L+ q; g  V  G- [6 q1 d& }  ^HornerandDr.ThomasReh,professorintheUWDepartmentofBiologicalStructure,willjoinDr.FredGagefromtheSalkInstitutefora12:30p.m.sessionFeb.16onNeuralStemCellsinHealthandDiseaseattheAAAS’sannualmeetinginSeattle.Gagewillpresentanoverviewofneuralstemcells,Hornerwilldiscussstemcellsandtherepairofthespinalcord,andRehwillfocusonstemcellsintheeye.
& e2 x- [3 [- B. y4 y' E7 ZThesametypesofcellsthatcreatescartissueinthespinalcolumncancreatenewcellsintheretinaoftheeye,especiallyinyounganimalsofsomespecies,accordingtoReh.Theretinaisadelicatelight-sensitivemembranethattransmitslightsignalstothebrain.Manyeyesdiseasesthatcauseblindness,suchasglaucomaandasage-related-macular-regeneration,damagetheretina.
# `; u2 S5 ?. I. wSalamandersdon’tgetglaucomabecausetheycanreadilyregenerateretinalcells.Thesameistrueofnewts,frogs,andsometypesoffish.We’retryingtounderstandtheremarkableregenerativepowersoftheselowervertebrates,andthroughthisunderstanding,developstrategiestostimulateregenerationinthehumanretina,Rehsaid.
5 j: H+ x$ k9 q% [7 v% Z) q; \Whilesalamanderscanregenerateretinalcellsthroughtheirlife,manyotherspecieslosethisabilityastheyage.Atsomepointineachspecieslifecycle,thestemcellsintheretinamakeatransitionfromaregenerativecelltoacellthatwillmakeascarinresponsetoinjury,likethecellsthatcausescarsinthespinalcord,Rehsaid.Chickensmakethetransitionafewweeksafterhatchinginmostoftheirretina,thoughtheyretainsomelimitedcapacitytoregenerateretinalcellsthroughoutlife.Inrats,it’sonlyamatterofafewdaysafterthecellsaregeneratedthattheylosetheirabilitytoregenerateotherretinalcells./ G% B! u: V. a- Z5 f
Humanretinasseeminglycan’trepairthemselves,yetinrecentstudieshumanretinalcellshavegrownnewneuronswhenculturedinthelaboratory.Thehopeisthatmanyofthemolecularandcellularmechanismsnecessaryforregeneration,thatserveamphibianssowell,arestillinplaceinhumans,Rehsaid.Futurestudiesfromthenervoussystem,aswellasotherorgansystems,shouldenableustodefinetheroadblocksintheregenerativeprocess,anddevelopstrategiestogoaroundthem.
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" O0 @$ m; M5 N7 e( _8 A* o# D: w来源: University Of Washington
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