Growth and myelination of explant cultures in defined medium.

The purpose of this study was to compare the development of organotypic cultures in defined medium versus nutrient containing serum and embryo extract (EE). Explant cultures of cerebellum with or without locus ceruleus were grown in the Maximow system and monitored in the living state and with histological stains. Thinner explants, fibronectin and a more frequent feeding schedule were required to overcome the growth differences encountered using a defined medium. The final medium formulation was arrived at by evaluation of living cultures and consisted of a basal medium (Dulbecco's minimal essential medium), a number of hormones and other supplements, and a final glucose concentration of 750 mg%. Using a Golgi stain and histofluorescence, it was shown that the three major types of neurons - Purkinje, deep nuclear, and locus ceruleus - developed similarly in the defined medium and in serum-EE cultures. Myelination occurred in virtually all cerebellar cultures in defined medium and the onset was earlier than in serum-EE cultures. These results indicate that differentiation of oligodendroglia and maturation of neurons occur in a defined medium. Elimination of thyroid hormone delayed the maturation of the cultures, both neurons and myelin, by 3-4 days.