In Vitro Effects of Glia Maturation Factor on Bipotential Glial Progenitor Cells

Abstract

The application of conventional and monoclonal antibodies as cell type specific markers has facilitated the identification of the different types of neural cells in culture (Raff et al., 1979). Astrocytes are identified with antibody against glial fibrillary acidic protein (GFAP) and oligodendrocytes with antibody against galactocerebroside (GC), the major glycolipid of myelin. Recently Raff et al. (1983a) distinguished two kinds of GFAP-positive astrocytes (type 1 and type 2) in cultures of developing rat optic nerve on the basis of morphology, growth characteristics, and binding to gangliosides. Type-1 astrocytes are flat, fibroblast-like cells that proliferate in response to growth factors, but do not bind tetanus toxin or the monoclonal antibody A2B5. In contrast, type-2 astrocytes have round cell bodies with multipolar branched processes resembling neurons or oligodendrocytes that divide infrequently in response to growth factors and bind both tetanus toxin and A2B5 antibody. Similar to tetanus toxin, the monoclonal antibody A2B5 recognizes specific gangliosides and was originally used as a neuron-specific marker in central nervous system cultures (Eisenbarth et al., 1979). In vitro studies have further indicated that the two types of astrocytes develop from two distinct precursor cells (Raff et al., 1984b). Oligodendrocytes and type-2 astrocytes, but not type-1 astrocytes, develop from a common A2B5-positive progenitor cell that has been identified in neonatal rat optic nerve cultures (Raff et al., 1983b). This bipotential glial progenitor cell, which is A2B5+, GFAP−, GC−, rapidly differentiates into an oligodendrocyte if cultured in serum-free medium, or into a type-2 astrocyte if cultured in the presence of calf serum (Raff et al., 1983b and 1984a; Temple and Raff, 1985).