O-2A glial progenitors from mature brain respond to CNS neuronal cell line-derived growth factors

During development, myelin-forming oligodendrocytes and type 2 astrocytes are believed to arise from bipotential (O-2A) glial progenitors. Previously we found that conditioned medium (CM) from the B104 rat CNS neuronal cell line promotes growth of neonatal rat O-2A progenitors in serum-free culture conditions with subsequent increases in differentiated progeny. We now report that O-2A progenitors are present in mature rat brains and that this CM promotes the growth, motility, and bipolar morphology of these cells from 30- and 65-day-old rat brains, as shown by quantitative studies using double immunostaining and [3H]thymidine-autoradiography. In addition, the growth-promoting action of B104 CM is not neutralized by antibodies to platelet-derived growth factor, a proposed progenitor mitogen. Subsequent to the proliferation of these O-2A progenitors, increases in oligodendrocytes and type 2 astrocytes occur. These data suggest a novel therapeutic strategy for some demyelinating diseases, e.g., multiple sclerosis, where there is a deficit in oligodendrocytes. Although it has been proposed by others that mature brain O-2A progenitors are less proliferative and thereby incapable of adequately replenishing lost oligodendrocytes in these diseases, we present in vitro evidence for continued response of mature brain O-2A progenitors to this neuronal cell line-derived mitogen.