Serum-Free Aggregate Cultures of Rat CNS Glial Cells: Biochemical, Immunocytochemical and Morphological Characterization

Abstract

Aggregate cultures of mixed glial cells, as well as of enriched astrocytes and oligodendrocytes were prepared and maintained in serum-free medium for up to 25 days. Biochemical measurements of both neuron-specific and glia-specific enzyme activities showed that these 3 types of aggregate cultures were virtually devoid of neurons. Astrocyte-enriched cultures were > 95% pure, with oligodendrocytes as the only apparent contaminant, whereas oligodendrocyte-enriched cultures still contained a considerable proportion of astrocytes. In all these neuron-free aggregate cultures both astrocytes and oligodendrocytes attained a high degree of maturation. These findings were confirmed by morphological examinations, and by immunofluorescence studies. Ultrastructural as well as immunocytochemical investigations using antibodies to myelin basic protein revealed that all 3 types of glial cell aggregate cultures contained myelin membranes, indicating that the presence of axons is not a prerequisite for the formation of myelin.