Inhibition of muscle cell development in culture by cells from spinal cord due to production of low molecular weight factor.

Relatively small numbers of cells cultured from chick embryo spinal cord had the property of inhibiting muscle cell growth and differentiation, as measured by protein synthesis, myoglobin synthesis, and myotube formation, when they had been in culture 4 days before the addition of dispersed muscles cells. Inhibition of pectoral white muscle and thigh red muscle development in culture was similar. Inhibition of this sort was not brought about by similar cocultivation with cells from liver, gizzard, intestine, lung, or skin, although skin cultures were slightly inhibitory. Simultaneous cocultivation of muscle and cord cells failed to result in inhibition of myogenesis. The inhibitory property was present in the medium, and inhibition was reduced by removal of conditioned medium and replenishment with fresh medium before introduction of myoblasts. Medium obtained from other tissues, similarly cultured, did not possess inhibitory properties. The inhibitiory properties of “cord-conditioned” medium were related to a factor or factors able to be concentrated by lyophilization and of relatively low molecular weight, as measured by membrane ultrafiltration and gel filtration chromatography. The nature of the cell type in spinal cord, e.g., neuronal glial, responsible for the production of this factor is not known.