Influence of meningeal cells on the proliferation and maturation of rat neuroblasts in culture.

Neuronal cells were obtained by dissociating cells from the cerebral hemispheres of rat embryos (10 to 17-day-old), either cleaned entirely or only partially of their meningeal membranes. These cells were seeded on poly-lysine-coated Petri dishes in serum-containing medium. The cultures most enriched in neuronal cells were obtained from brains of 13- to 15-day-old embryos and after 2 h, the culture medium was switched to Dulbecco's modified Eagle's medium, without serum, supplemented with the N1 supplements as described by Bottenstein et al. (1980). The proliferation of neuroblasts from 13-day-old embryos in the presence or absence of meningeal cells was studied by using a combination of tritiated thymidine autoradiography and immuno-staining against neurofilament proteins. The neuroblasts seem to proliferate during the first 3 days. The proliferative activity was further enhanced in the presence of meningeal cells. The glioblasts multiply only after a period of one week in culture conditions as observed here. The subsequent development of the neuroblasts was followed over a period of 4 weeks and the ultrastructural appearance of these cells was investigated at 2 and 3 weeks. In the presence of meningeal cells, many neurons, intensely stained for neurofilament proteins, survived for 21 days, while in control cultures they underwent massive degeneration after 2 weeks. Synapses with numerous clear vesicles were abundant in cultures grown under the influence of meningeal cells; they were rare and possessed few vesicles in control cultures. The data indicate that meningeal cells affect the proliferation and maturation of rat neuroblasts in culture.