Differentiation of astrocytes and oligodendrocytes from germinal matrix cells in primary culture

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Abstract
Primary cultures derived from neonatal rat forebrain grow almost entirely as glial cultures, with a large astrocytic preponderance and smaller numbers of oligodendrocytic cells. Although both astrocytic and oligodendrocytic characteristics are acquired in vitro, the origins of both types of glia in primary cultures have not been determined. We tested the hypothesis that glia differentiate in vitro from immature neuroectodermal cells by following the fate of germinal zone cells in primary cultures. A monoclonal antibody that binds GD3 ganglioside was used as a marker for cells of the subventricular zone (SVZ), since antibody binding in newborn rat forebrain could be detected by immunofluorescence only in the SVZ of newborn rats (Goldman et al., 1984). We followed the expression of glial fibrillary acidic protein (GFAP), an astrocytic marker; galactocerebroside (GC), an oligodendrocytic marker; and GD3 during the first several weeks of culture. Both GFAP and GC expression were first detected in cells that bound the GD3 antibody. Astrocytes developed during the first week in vitro; eventually, they lost the ability to bind the GD3 antibody and most became GD3-/GFAP+ cells. In high-density cultures, a population of small cells that resided on top of the astrocytic monolayer retained GD3 expression. GC-antibody binding was first observed in these cells of the upper layer, although it was not readily apparent until the second week of culture. Few GC+ cells were seen in cultures grown at low density, however.(ABSTRACT TRUNCATED AT 250 WORDS)