GROWTH-FACTOR MODULATION OF INJURY-REACTIVE EPENDYMAL CELL-PROLIFERATION AND MIGRATION

Injury-reactive ependymal cells from regenerating axolotl spinal cord can be maintained in their mesenchymal outgrowth phase in culture (O'H ara et al., 1992). To address the ability of specific growth factors i n stimulating or maintaining migration and proliferation, mesenchymal ependymal cell cultures derived from injured axolotl spinal cord at 2 weeks post-lesioning were used to determine the potential effects of e pidermal growth factor, platelet-derived growth factor and transformin g growth factor-beta 1. In our cultures, medium containing epidermal g rowth factor alone or in combination with the other growth factors per mitted significant migration and proliferation from ependymal explants . Platelet-derived growth factor alone was shown to have a small posit ive effect on ependymal cell migration and no effect on proliferation. Transforming growth factor-beta 1 alone did not support cell migratio n and was found to be inhibitory towards cellular proliferation. Lastl y, medium containing platelet-derived growth factor and transforming g rowth factor-beta 1, but not epidermal growth factor, caused ependymal cell explants to break apart and migrate on the dish as cords. Migrat ion and proliferation of injury-reactive ependymal cells was shown to be dependent on epidermal growth factor in vitro. These results sugges t that epidermal growth factor may be a critical component in vivo dur ing the initiation of ependymal migration and proliferation following transection of the axolotl spinal cord. The reorganization of cultured ependymal cells in response to the combination of platelet-derived gr owth factor and transforming growth factor-beta shows that ependymal o rganization can be modulated by growth factors. This suggests that the progressive changes observed during regeneration may be under the con trol of growth factors.