Production of spinal cord growth inhibitor by nonneuronal cells

Abstract

Separation of chick embryo spinal cord cells into cell cultures of glial-enriched and neuronal-enriched elements by the method of selective adhesiveness indicated a greater production of growth inhibitor by the glial-enriched cultures. Glial-enriched cultures produced 177.2% more inhibitor per microgram cell protein than did unseparated spinal cord cell cultures, whereas neuronal-enriched cultures produced less. The glial-enriched cultures contained 28% of the choline acetyltransferase of neuronal-enriched cultures, few or no discernible neurons, and no cells binding dopamine or containing catecholamines by cytofluorescence. The predominant cell of the glial-enriched cultures was large, phase-light with ruffled borders, with parallel streak-like processes, and fibrillar cytoplasm. Cultures produced by serial passage of unseparated spinal cord cells also were found to be depleted in neurons and dopamine-binding cells, as well as in choline acetyltransferase activity, to 19% of control values. These serially passaged cultures, however, retained the ability to produce inhibitor as well as did primary cultures. Serially passaged cultures of spinal cord cells were composed of cells similar to those predominant in glial-enriched cultures. Nerve growth factor had no effect on inhibitor production. We suggest that the growth inhibitor of spinal cord cultures was not produced by neuronal cells but may be of glial origin.