The　biological　character　of　neuroepithelial　stem　cells (NESCs) was　assessed　ix　vitro　and　in　vivo　to　confirm the　feasibility　of　using　them　as　donor　cells for　intracerebral　grafting.　All　of　the　NESCs,　which　were　derived from　mesencephalic　neural　plates,　were　immunohislochemically　positive　for　both　nestin　and　fibroblast growth　factor〔FGF) receptor.　Isolation　and　proliferaUon　of　NESCs　was　attempted from　culture　under　various　conditions.　Neurospheres　fomed　in　medium　conしaining　FGF2,　and　NESCs　were　able　to　grow　at　a　maximum　proliferation　rate　of　approximately　7.3　fold　in　seven　days.　The　single　cells　derived　from　primary spheres　differentiated　into　neurons　that　extended　long　neurites　in　two　days　and　expressed　several neurochemical　markers,　suggesting　maturation　of　the　cells,　but hardly　any　filial　cells　were　observed.　The growth　potential　of　the　NESCs, however,　subsequently　diminished　even　in　the　medium　containing　FGF2, and　NESCs　derived　from　FGF2-responsive neurospheres　after　serial　weekly　passages　tended　to　differentiate into　glial　cells　more　than　into　eurons.　The NESCs　proliferated　in　seven days　with　FGF2,　which　was ransplanted　into　normal　rat　striata,　also　expressed　nestin　and　TuJ　I, but　GFAP　positive　cells　were　hardly seen.　These　experimental　results　indicated　that　the　neural　stem　cells　were　not　always　equal　in　their　differ entiation　paths　and　that　the　features　of　neural　stem　cells　could　be　changed　with　the　duration　of　culture.
NESCs　could　be　proliferated　with　the　addition　of　FGF2　with　having　preserved　vigorous　neuronal differennation　depending　on　the　required　amount　at　its　maximum　under　FGF2　at　the　7-day　time　point,　suggesting that　7-day-old　NESCs　proliferated　with　FGF2　may　be　favorable　donor　cells　for　inlracerebral　grafting　to
restore　damaged　neuronal　circuits　in　diseased　brain.

原著