Stem Cells Found In Adults May Repair Nerves

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日期: 2004-02-18 今日/总浏览: 1/3364 ?  z% x! X7 {2 L3 s
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Itusedtobeconsidereddogmathatanerve,onceinjured,couldneverberepaired.Now,researchershavelearnedthatsomenerves,evennervesinpartsofthebrain,canregenerateorbereplaced.Bystudyingthechemicalsignalsthatencourageorimpedetherepairofnerves,researchersattheUniversityofWashington,theSalkInstitute,andotherinstitutionsmaycontributetoeventualtreatmentsforinjuredspinesanddiseasedretinas,accordingtoapresentationattheannualmeetingoftheAmericanAssociationfortheAdvancementofScience(AAAS).$ r4 }4 X; P2 q+ h* v
Muchofthisresearchfocusesonstemcells,oneofseveraltypesofgeneralcellsthatcangiverisetospecializedcells,likeneurons.Itwasoncethoughtthathumanstemcellswereonlyfoundinembryos,andinbonemarrow,wheretheyproducebloodcells.Butstemcellsarealsobeingfoundinadults,includingthebrainandtheeye.Forexample,stemscellssteadilyreplacedeadneuronsintheolfactorybulb,whichtransmitsscentsignalstothebrain,andthehippocampaldentategyrus,anareathatorganizesshort-termmemory.: E* t) D. t( N% }% I9 ?
However,thepaceofstem-cellrepairsinhumansisslow.Andinsomecases,stemcellscanevenimpedehealing.Stemcellsinaninjuredspinalcordcancreateastickyscarthatblocksnerveregeneration,accordingtoDr.PhilipHorner,anassistantprofessorintheDepartmentofNeurosurgeryintheUWSchoolofMedicine.
- L4 t: L' e6 y% l2 UWe’vefoundthattheaxons,thepartsofthenervesthattransmitsignals,trytoregenerateafteraninjurybutgetcaughtinthescar.It’slikethey’restuckinthemud,Hornersaid.We’restudyingwaysthatthisprocessisregulatedtoseeifitcanbemanipulatedtopromotehealing.Inotherwords,we’relookingatwaystogettheaxonsoutofthemud.Onewayistomakethemudlessstickybymanipulatingstemcellsthatparticipateinscarformation.Anotheristostimulatetheaxonstopushthroughthescarbyprovidingthecutnerveswithmoleculesthatinduceelongation.We’reusingmolecularsignalscalledgrowthfactorstosimulatethegrowthofculturednervecellsinthelaboratory.
3 ^: e6 _+ x3 S4 f% v0 {+ {0 _9 cHornerandDr.ThomasReh,professorintheUWDepartmentofBiologicalStructure,willjoinDr.FredGagefromtheSalkInstitutefora12:30p.m.sessionFeb.16onNeuralStemCellsinHealthandDiseaseattheAAAS’sannualmeetinginSeattle.Gagewillpresentanoverviewofneuralstemcells,Hornerwilldiscussstemcellsandtherepairofthespinalcord,andRehwillfocusonstemcellsintheeye.; Q+ W4 n) I# w. Y6 P
Thesametypesofcellsthatcreatescartissueinthespinalcolumncancreatenewcellsintheretinaoftheeye,especiallyinyounganimalsofsomespecies,accordingtoReh.Theretinaisadelicatelight-sensitivemembranethattransmitslightsignalstothebrain.Manyeyesdiseasesthatcauseblindness,suchasglaucomaandasage-related-macular-regeneration,damagetheretina.4 I4 f- Q& p7 u6 x0 h
Salamandersdon’tgetglaucomabecausetheycanreadilyregenerateretinalcells.Thesameistrueofnewts,frogs,andsometypesoffish.We’retryingtounderstandtheremarkableregenerativepowersoftheselowervertebrates,andthroughthisunderstanding,developstrategiestostimulateregenerationinthehumanretina,Rehsaid.3 r! [8 {0 A4 M9 g+ D
Whilesalamanderscanregenerateretinalcellsthroughtheirlife,manyotherspecieslosethisabilityastheyage.Atsomepointineachspecieslifecycle,thestemcellsintheretinamakeatransitionfromaregenerativecelltoacellthatwillmakeascarinresponsetoinjury,likethecellsthatcausescarsinthespinalcord,Rehsaid.Chickensmakethetransitionafewweeksafterhatchinginmostoftheirretina,thoughtheyretainsomelimitedcapacitytoregenerateretinalcellsthroughoutlife.Inrats,it’sonlyamatterofafewdaysafterthecellsaregeneratedthattheylosetheirabilitytoregenerateotherretinalcells.  U. I$ t2 A# l5 j' P4 e, F/ @
Humanretinasseeminglycan’trepairthemselves,yetinrecentstudieshumanretinalcellshavegrownnewneuronswhenculturedinthelaboratory.Thehopeisthatmanyofthemolecularandcellularmechanismsnecessaryforregeneration,thatserveamphibianssowell,arestillinplaceinhumans,Rehsaid.Futurestudiesfromthenervoussystem,aswellasotherorgansystems,shouldenableustodefinetheroadblocksintheregenerativeprocess,anddevelopstrategiestogoaroundthem.: j  T% \6 x7 E

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9 l0 a: X) Y2 d& u- L; p% t" g作者: + {" M' x% B- u0 z$ P6 o! F# [
来源: University Of Washington
2 \$ k& z& C8 `& v) V( V发布者: 亦云