- 积分
- 97
- 威望
- 97
- 包包
- 3142
|
日期: 2004-02-18 今日/总浏览: 1/336# k( v* J( }* E; u& t- y
6 @$ j+ ]5 z/ E' w0 g5 C. L; ]1 X. H9 C S. b0 O" c, y
+ i9 v" I F' ?3 V
: X* d% V+ W1 N, PItusedtobeconsidereddogmathatanerve,onceinjured,couldneverberepaired.Now,researchershavelearnedthatsomenerves,evennervesinpartsofthebrain,canregenerateorbereplaced.Bystudyingthechemicalsignalsthatencourageorimpedetherepairofnerves,researchersattheUniversityofWashington,theSalkInstitute,andotherinstitutionsmaycontributetoeventualtreatmentsforinjuredspinesanddiseasedretinas,accordingtoapresentationattheannualmeetingoftheAmericanAssociationfortheAdvancementofScience(AAAS).
/ v# K |6 J( o5 s$ IMuchofthisresearchfocusesonstemcells,oneofseveraltypesofgeneralcellsthatcangiverisetospecializedcells,likeneurons.Itwasoncethoughtthathumanstemcellswereonlyfoundinembryos,andinbonemarrow,wheretheyproducebloodcells.Butstemcellsarealsobeingfoundinadults,includingthebrainandtheeye.Forexample,stemscellssteadilyreplacedeadneuronsintheolfactorybulb,whichtransmitsscentsignalstothebrain,andthehippocampaldentategyrus,anareathatorganizesshort-termmemory." U$ S. c( t- j3 U8 e$ Z, f( S
However,thepaceofstem-cellrepairsinhumansisslow.Andinsomecases,stemcellscanevenimpedehealing.Stemcellsinaninjuredspinalcordcancreateastickyscarthatblocksnerveregeneration,accordingtoDr.PhilipHorner,anassistantprofessorintheDepartmentofNeurosurgeryintheUWSchoolofMedicine.
% U; s" |/ \) g: N. ` d$ NWe’vefoundthattheaxons,thepartsofthenervesthattransmitsignals,trytoregenerateafteraninjurybutgetcaughtinthescar.It’slikethey’restuckinthemud,Hornersaid.We’restudyingwaysthatthisprocessisregulatedtoseeifitcanbemanipulatedtopromotehealing.Inotherwords,we’relookingatwaystogettheaxonsoutofthemud.Onewayistomakethemudlessstickybymanipulatingstemcellsthatparticipateinscarformation.Anotheristostimulatetheaxonstopushthroughthescarbyprovidingthecutnerveswithmoleculesthatinduceelongation.We’reusingmolecularsignalscalledgrowthfactorstosimulatethegrowthofculturednervecellsinthelaboratory.5 F; \" s# Y* t" \, M% A
HornerandDr.ThomasReh,professorintheUWDepartmentofBiologicalStructure,willjoinDr.FredGagefromtheSalkInstitutefora12:30p.m.sessionFeb.16onNeuralStemCellsinHealthandDiseaseattheAAAS’sannualmeetinginSeattle.Gagewillpresentanoverviewofneuralstemcells,Hornerwilldiscussstemcellsandtherepairofthespinalcord,andRehwillfocusonstemcellsintheeye.: B/ |; t6 h Y) V& C: \, ~
Thesametypesofcellsthatcreatescartissueinthespinalcolumncancreatenewcellsintheretinaoftheeye,especiallyinyounganimalsofsomespecies,accordingtoReh.Theretinaisadelicatelight-sensitivemembranethattransmitslightsignalstothebrain.Manyeyesdiseasesthatcauseblindness,suchasglaucomaandasage-related-macular-regeneration,damagetheretina.! v g' n1 c' a& s) p1 e6 y
Salamandersdon’tgetglaucomabecausetheycanreadilyregenerateretinalcells.Thesameistrueofnewts,frogs,andsometypesoffish.We’retryingtounderstandtheremarkableregenerativepowersoftheselowervertebrates,andthroughthisunderstanding,developstrategiestostimulateregenerationinthehumanretina,Rehsaid. ^) v. M+ V- ^1 a
Whilesalamanderscanregenerateretinalcellsthroughtheirlife,manyotherspecieslosethisabilityastheyage.Atsomepointineachspecieslifecycle,thestemcellsintheretinamakeatransitionfromaregenerativecelltoacellthatwillmakeascarinresponsetoinjury,likethecellsthatcausescarsinthespinalcord,Rehsaid.Chickensmakethetransitionafewweeksafterhatchinginmostoftheirretina,thoughtheyretainsomelimitedcapacitytoregenerateretinalcellsthroughoutlife.Inrats,it’sonlyamatterofafewdaysafterthecellsaregeneratedthattheylosetheirabilitytoregenerateotherretinalcells.2 z5 m) c: n7 ?4 A: H* \. s
Humanretinasseeminglycan’trepairthemselves,yetinrecentstudieshumanretinalcellshavegrownnewneuronswhenculturedinthelaboratory.Thehopeisthatmanyofthemolecularandcellularmechanismsnecessaryforregeneration,thatserveamphibianssowell,arestillinplaceinhumans,Rehsaid.Futurestudiesfromthenervoussystem,aswellasotherorgansystems,shouldenableustodefinetheroadblocksintheregenerativeprocess,anddevelopstrategiestogoaroundthem.
% x0 ?& A& }' Z5 x/ N; a
" u# m1 i1 b8 ]! s; Q( X$ |$ s5 ]! s. `, S. i
( }. T' y5 i, {4 R4 j: j
1 X6 c" c4 b& Q8 Z0 q, b5 D
4 T5 q% c l# b2 x% ~作者: 3 e6 i! x) @1 u, M- C' c/ h
来源: University Of Washington# u3 C5 N5 A: c- f' R( a' Q
发布者: 亦云 |
|