Stimulation of non-neuronal cell proliferation in vitro by mitogenic factors present in highly purified sympathetic neurons.

Sympathetic neurons have been demonstrated to contain one or more mitogens which are active on highly purified non-neuronal cells cultured in medium containing an optimal concentration of fetal calf serum. Neurons and homologous non-neuronal cells were separated by a method recently developed in this laboratory. The highly purified neurons were either sonicated or homogenized prior to addition to nonneuronal cultures. The presence of neuronal sonicate (1) greatly stimulated [3H]thymidine incorporation into acid-precipitable macromolecules without altering the soluble [3H]thymidine pool, (2) increased both the fraction of non-neuronal cells which took up [3H]thymidine and the density of labeling as observed by autoradiography, and (3) increased the number of cells present in treated cultures after 40 h. The enhancement of [3H]thymidine incorporation was dose-dependent and did not involve cyclic AMP. Addition of neuronal sonicate also caused marked non-neuronal cell elongation which resulted in the elaboration of very long cell processes. The active factor(s) in the neuronal sonicate were partially heat-labile. Norepinephrine was ruled out as a possible mitogenic factor.