Effect of mitogens in various organs and cell culture conditioned media on rat oligodendrocytes

Extracts prepared from embryonic, neonatal and adult rat brain were examined for the presence of oligodendroglial mitogens. Brain-derived mitogenic activities were found in all developmental stages with specific activity increasing during neonatal development. Extracts from postnatal day 7 contained the highest specific activity. Upon fractionation by molecular weight, each developmental stage expressed a peak of mitogenic activity corresponding to 67,000 daltons. This fraction was able to induce proliferation in cultures grown in serum, serumless chemically defined medium or serum-free medium alone. Neonatal and adult brain extracts had an additional peak of activity at 14,000 daltons. This latter activity was expressed only under serum-supplemented culture conditions. Mitogenic activity was also found in conditioned media from the clonal glioma cell line C6 and primary astrocytes and in extracts derived from neonatal rat liver. These data indicate that a limited range of brain-derived mitogens for oligodendrocytes exist during development and adulthood.