Glial expression of fibroblast growth factor-9 in rat central nervous system

We examined the expression of fibroblast growth factor (FGF)-9 in the rat central nervous system (CNS) by immunohistochemistry and in situ hybridization studies. FGF-9 immunoreactivity was conspicuous in motor neurons of the spinal cord, Purkinje cells, and neurons in the hippocampus and cerebral cortex. In addition to the neuronal localization of FGF-9 immunoreactivity that we reported previously, the present double-label immunohistochemistry clearly demonstrated that the immunoreactivity was present in glial fibrillary acidic protein (GFAP)-positive astrocytes preferentially present in the white matter of spinal cord and brainstem of adult rats and in CNPase-positive oligodendrocytes that were arranged between the fasciculi of nerve fibers in cerebellar white matter and corpus callosum of both adult and young rats. There was a tendency for FGF-9 immunoreactivity in oligodendrocytes to be more pronounced in young rats than in adult rats. The variation of oligodendrocyte FGF-9 immunoreactivity in adult rats was also more pronounced than that in young rats. With in situ hybridization, FGF-9 mRNA was observed in astrocytes in the white matter of rat spinal cord and oligodendrocytes in the white matter of cerebellum and corpus callosum of adult and young rats. The expression of FGF-9 mRNA in glial cells was lower than in neurons, and not all glial cells expressed FGF-9. In the present study, we demonstrated that FGF-9 was expressed not only in neurons but also in glial cells in the CNS. FGF-9 was considered to have important functions in adult and developing CNS.