MYELINATION IN-VITRO OF RODENT DORSAL-ROOT GANGLIA BY GLIAL PROGENITOR CELLS

Oligodendrocytes synthesize myelin in the mammalian central nervous sy stem; they develop from glial progenitors which, at least in vitro, ar e bipotential and also differentiate into astrocytes. Maturation of th ese 0-2A progenitors is known to be influenced by growth factors and b y extracellular matrix molecules. We investigated the effect of neuron s on glial development by co-culturing highly purified rodent embryoni c dorsal root ganglia with neonatal 0-2A progenitors. Neurons produce signals, including platelet-derived growth factor BE and basic fibrobl ast growth factor, which stimulate progenitor cells to synthesize DNA; axonal contact is associated with down-regulation in the expression o f complex ganglioside surface molecules on 0-2A progenitors; with matu ration, many of these cells develop into oligodendrocytes allowing the normal process of myelination to take place, but neurons also promote the differentiation of type 2 astrocytes. This orchestration of proli feration and differentiation in 0-2A progenitor cells favours the deve lopment of glial-neuronal interactions needed for saltatory conduction of the nerve impulse.