Analysis of glial cell differentiation in peripheral nervous tissue: II. Neurons promote S100 synthesis by purified glial precursor cell populations

Isolated sensory neurons in vitro do not contain or synthesize S100, whereas glial cell precursor populations do. These precursor cells, when isolated from other cell types, produce low levels of S100 but never undergo the developmental transition to produce high levels of S100. When glial cell precursors are combined with isolated, live or paraformaldehyde-fixed sensory neurons, the precursor cells do undergo the second transition, and accumulate high levels of S100. Peroxidase-anti-peroxidase immunohistochemical staining for S100 confirms previous conclusions (B. Holton and J. A. Weston, 1982, Develop. Biol.89, 64–71) that only those glial cells which are closely apposed to neurons contain augmented levels of S100. This stimulation appears to be specific to neuronal/glial interactions since live or fixed fibroblasts, when cocultured with glial precursor cells, do not promote accumulation of S100 by the glial cells.