Mitogenic response of adult rat olfactory ensheathing glia to four growth factors.

Olfactory ensheathing glia (EG) from adult rat proliferate slowly in vitro without added mitogens. The potential future use of EG in transplantation within the central nervous system to improve neural repair is dependent on identifying mitogens that will effectively expand EG without altering their phenotype. The mitogenic effects of heregulin (HRG), fibroblast growth factor 2 (FGF-2), platelet-derived growth factor BB (PDGF-BB), insulin-like growth factor 1 (IGF-1), and forskolin (FSK) on cultured adult-derived rat EG were monitored by tritiated-thymidine labeling and p75 immunostaining. In serum-containing medium, HRG, FGF-2, PDGF-BB, IGF-1, and FSK were capable of stimulating EG proliferation, and the stimulation by these growth factors was potentiated by FSK. The combinations of HRG + FGF-2, HRG + PDGF-BB, HRG + IGF-1, FGF-2 + PDGF-BB, and FGF-2 + IGF-1 all promoted EG proliferation in an additive manner. In serum-free medium, HRG and FGF-2 were mitogenic, but PDGF-BB, IGF-1 and FSK were not; however, FSK potentiated the stimulation by HRG and FGF-2, and the combination of HRG + FGF-2 promoted EG proliferation in an additive manner. This new information will be useful for the design of protocols to achieve sufficient numbers of adult-derived EG for clinical purposes. This study also further establishes similarities between EG and Schwann cells. Copyright 2001 Wiley-Liss, Inc.