MORPHOLOGICAL-DIFFERENTIATION OF ASTROGLIAL PROGENITOR CELLS FROM EGF-RESPONSIVE NEUROSPHERES IN RESPONSE TO FETAL CALF SERUM, BASIC FIBROBLAST GROWTH-FACTOR, AND RETINOL

Procurement of multipotential neuroglial stem cells is possible with t he addition of epidermal growth factor (EGF). Stem cells will differen tiate into neurons and glia upon the removal of EGF from the culture m edium. We have previously characterized the neuronal differentiation o f stem cells derived from long-term cultured nonpassage neurospheres. In the current study, we (1) characterize the morphological differenti ation of the astroglial progenitor cell from 3-mo-old neurospheres, (2 ) examine whether the astroglial progenitor cells from neurospheres of different brain areas exhibit different differentiation responses to the same exogenous signals, and (3) test the effects of basic fibrobla st growth factor (bFGF) and retinol on differentiation. Cerebral corte x, striatum, and mesencephalon cells were obtained from Embryonic Day 14 (E-14) rat fetuses and were dissociated for the procurement of neur ospheres in chemically defined medium supplemented with EGF. After 3 m o in culture, the neurospheres, derived from each of the three brain a reas, were subcultured into three groups on chamber slides: (1) basal medium, (2) the basal medium plus 20 ng/mL bFGF, and (3) the basal med ium plus 10 mu M retinol. Phenotypic expression of astroglial cells wa s examined after 14 days subculture. Our findings indicate that the 3- mo-old cultured nonpassage neurospheres contained numerous multipotent ial stem cells that stained positive with nestin, and that environment al factors played an important role in influencing the differentiation of astroglial progenitor cells. As detected by glial fibrillary acid protein (GFAP), astroglial progenitor cells turned into protoplasmic a strocytes in the FCS-containing basal medium, fibrous astrocytes in th e presence of bFGF, and spindle-shaped astrocytes in the presence of r etinol. There were no noticeable differences in differentiation among astroglial progenitor cells of the various brain region-derived neuros pheres in any of the three medium conditions. Peculiar varicosity- and growth cone-like structures on the long slender GFAP-positive process es suggest that neuroblasts and glioblast may share common morphologie s, features, or common progenitor cells during initial differentiation in vitro.