Exogenous FGF-1 Differently Regulates Oligodendrocyte Replenishment in an SCI Repair Model and Cultured Cells

We studied the phenotypes in an oligodendrocyte genesis site at the acute stage of spinal cord injury, when we observed regenerated ascending neurites. Pan-oligodendrocyte marker OLIG2+ cells were more in fibroblast growth factor (FGF)-1-treated rats (F group) than in non-treated (T group) in this site, while the number of NG2+OX42- oligodendrocyte progenitor cell (OPC), CNPase+ OPC, Nkx2.2+ OPC, and APC+ remyelinating oligodendrocytes was less in the F group. Paradoxically, when we label the rats with pulsed bromodeoxyuridine (BrdU), we found that the mitotic NKX2.2+ OPC cells are more in the F group than in the T group. We tested the embryonic spinal cord mixed culture. FGF treatment resulted in more NG2(+) CNPase (+) than non-FGF-1-treated culture, while the more mature NG2(-) CNPase(+) cell numbers were reduced. When we block the FGF receptor in the injured rat model, the NG2+OX42- cell numbers were increased to be comparable to non-FGF-1 rats, while this failed to bring back the APC+ mature oligodendrocyte cell numbers. As migration of OPC toward injury is a major factor that was absent from the cell culture, we tested 8 mm away from the injury center, and found there were more NG2+ cells with FGF-1 treatment. We proposed that it was possibly a combination of migration and proliferation that resulted in a reduction in the NG2+ OPC population at the oligodendrocyte genesis site when FGF-1 was added to the spinal cord injury in vivo.