Stem Cells Found In Adults May Repair Nerves

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日期: 2004-02-18 今日/总浏览: 1/3367 f& H# ~% @2 ?' w  V
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7 E( S3 X0 m/ j$ I/ h- cItusedtobeconsidereddogmathatanerve,onceinjured,couldneverberepaired.Now,researchershavelearnedthatsomenerves,evennervesinpartsofthebrain,canregenerateorbereplaced.Bystudyingthechemicalsignalsthatencourageorimpedetherepairofnerves,researchersattheUniversityofWashington,theSalkInstitute,andotherinstitutionsmaycontributetoeventualtreatmentsforinjuredspinesanddiseasedretinas,accordingtoapresentationattheannualmeetingoftheAmericanAssociationfortheAdvancementofScience(AAAS)., [6 m/ N8 `! A: K! M
Muchofthisresearchfocusesonstemcells,oneofseveraltypesofgeneralcellsthatcangiverisetospecializedcells,likeneurons.Itwasoncethoughtthathumanstemcellswereonlyfoundinembryos,andinbonemarrow,wheretheyproducebloodcells.Butstemcellsarealsobeingfoundinadults,includingthebrainandtheeye.Forexample,stemscellssteadilyreplacedeadneuronsintheolfactorybulb,whichtransmitsscentsignalstothebrain,andthehippocampaldentategyrus,anareathatorganizesshort-termmemory.3 Z; c1 v: O# }* ]) o
However,thepaceofstem-cellrepairsinhumansisslow.Andinsomecases,stemcellscanevenimpedehealing.Stemcellsinaninjuredspinalcordcancreateastickyscarthatblocksnerveregeneration,accordingtoDr.PhilipHorner,anassistantprofessorintheDepartmentofNeurosurgeryintheUWSchoolofMedicine.
! X2 b0 n- O' ?We’vefoundthattheaxons,thepartsofthenervesthattransmitsignals,trytoregenerateafteraninjurybutgetcaughtinthescar.It’slikethey’restuckinthemud,Hornersaid.We’restudyingwaysthatthisprocessisregulatedtoseeifitcanbemanipulatedtopromotehealing.Inotherwords,we’relookingatwaystogettheaxonsoutofthemud.Onewayistomakethemudlessstickybymanipulatingstemcellsthatparticipateinscarformation.Anotheristostimulatetheaxonstopushthroughthescarbyprovidingthecutnerveswithmoleculesthatinduceelongation.We’reusingmolecularsignalscalledgrowthfactorstosimulatethegrowthofculturednervecellsinthelaboratory.: ^& D6 J& K/ t( I5 L0 d
HornerandDr.ThomasReh,professorintheUWDepartmentofBiologicalStructure,willjoinDr.FredGagefromtheSalkInstitutefora12:30p.m.sessionFeb.16onNeuralStemCellsinHealthandDiseaseattheAAAS’sannualmeetinginSeattle.Gagewillpresentanoverviewofneuralstemcells,Hornerwilldiscussstemcellsandtherepairofthespinalcord,andRehwillfocusonstemcellsintheeye.# P9 G! \* Y& W' ?4 b3 M
Thesametypesofcellsthatcreatescartissueinthespinalcolumncancreatenewcellsintheretinaoftheeye,especiallyinyounganimalsofsomespecies,accordingtoReh.Theretinaisadelicatelight-sensitivemembranethattransmitslightsignalstothebrain.Manyeyesdiseasesthatcauseblindness,suchasglaucomaandasage-related-macular-regeneration,damagetheretina.
: \/ Z" |# m  i1 f5 S  {Salamandersdon’tgetglaucomabecausetheycanreadilyregenerateretinalcells.Thesameistrueofnewts,frogs,andsometypesoffish.We’retryingtounderstandtheremarkableregenerativepowersoftheselowervertebrates,andthroughthisunderstanding,developstrategiestostimulateregenerationinthehumanretina,Rehsaid.7 @% `$ c4 T* Z  V" p4 W# l' R
Whilesalamanderscanregenerateretinalcellsthroughtheirlife,manyotherspecieslosethisabilityastheyage.Atsomepointineachspecieslifecycle,thestemcellsintheretinamakeatransitionfromaregenerativecelltoacellthatwillmakeascarinresponsetoinjury,likethecellsthatcausescarsinthespinalcord,Rehsaid.Chickensmakethetransitionafewweeksafterhatchinginmostoftheirretina,thoughtheyretainsomelimitedcapacitytoregenerateretinalcellsthroughoutlife.Inrats,it’sonlyamatterofafewdaysafterthecellsaregeneratedthattheylosetheirabilitytoregenerateotherretinalcells.
$ H" {0 l! e+ c1 T. j. tHumanretinasseeminglycan’trepairthemselves,yetinrecentstudieshumanretinalcellshavegrownnewneuronswhenculturedinthelaboratory.Thehopeisthatmanyofthemolecularandcellularmechanismsnecessaryforregeneration,thatserveamphibianssowell,arestillinplaceinhumans,Rehsaid.Futurestudiesfromthenervoussystem,aswellasotherorgansystems,shouldenableustodefinetheroadblocksintheregenerativeprocess,anddevelopstrategiestogoaroundthem.
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1 i3 L( W: \9 m" J' m来源: University Of Washington. Z3 H4 g: _1 ~2 R* _7 |2 y$ T
发布者: 亦云