In vitro analysis of the oligodendrocyte lineage in mice during demyelination and remyelination

Whether the growth factors mentioned above have an effect on O-2A lineage cells derived from adult CNS tissue is not yet clear. Human oligodendrocytes isolated from normal adult brain do not proliferate in response to treatment with several growth factors, including PDGF, FGF, epidermal growth factor, and interleukin 2 (Yong et al., 1988) . Similarly, in the present study we found that PDGF, bFGF, or IGF-I did not induce mitosis of O-2A lineage cells cultured from adult mice, as assayed by [3H]thymidine incorporation. However, a factor secreted by B104 neuroblastoma cells is mitogenic for O-2A progenitors and oligodendrocytes cultured from adult rat brain (Hunter et al., 1988) . Thus, normal adult O-2A lineage cells are capable of proliferating when exposed to an adequate stimulus. Such a stimulus could be a factor (or factors) released in the CNS during demyelination since O-2A lineage cells in the spinal cord of MHV-A59 infected mice showed increased proliferation both in vivo (Godfraind et al., 1989) and in vitro (the present data). Interestingly, some growth factors can influence the antigenic phenotypes of O-2A lineage cells in our cultures of demyelinating/remyelinating CNS. Basic FGF decreased the percentage of O-2A lineage cells expressing GC, whereas IGF-I increased the proportion of oligodendrocytes relative to type 2 astrocytes. Thus bFGF and IGF-I might modulate phenotype expression in CNS development and remyelination.