Mitogens for glial cells: a comparison of the response of cultured astrocytes, oligodendrocytes and Schwann cells.

We have identified two growth factors for cultured rat astrocytes: fibroblast growth factor, a peptide derived from either whole bovine brain, or pituitaries, and a growth factor in extracts of bovine pituitary which was previously identified as a Schwann cell mitogen. Oligodendrocytes in primary cultures derived from neonatal rat central nervous system divide only rarely if at all. These growth factors did not stimulate primary oligodendrocytes to divide. Occasionally cells found in suspension in long-term cultures of the central nervous system were enriched for cells which were identified as oligodendrocytes by the presence of galactocerebroside on their surface and myelin basic protein in their cytoplasm. When provided with a monolayer of irradiated 3T3 cells, these oligodendrocytes were able to spread out and extend elaborate branched processes typical of oligodendrocytes in the primary cultures. Unlike their counterparts in the primary cultures, these suspension-derived oligodendrocytes are capable of cell division as demonstrated by the uptake of [3H]thymidine and autoradiography.