In situ expression of fibroblast growth factor receptors by oligodendrocyte progenitors and oligodendrocytes in adult mouse central nervous system

Basic fibroblast growth factor (bFGF) induces proliferation and alters differentiation of cultured oligodendrocyte lineage cells. In situ, bFGF is present in normal adult central nervous system (CNS) and upregulated during an early stage of various pathological conditions. We examined the expression of receptors for bFGF (FGFRs) by oligodendrocyte progenitors and oligodendrocytes in situ in normal adult mouse CNS to further understand the potential in situ response to bFGF. We found FGFR immunoreactivity in oligodendrocyte progenitors, identified by expression of NG2 or platelet-derived growth factor alpha receptor (PDGFalphaR), and in oligodendrocytes expressing 2',3'-cyclic nucleotide 3' phosphodiesterase. Particularly interesting is the demonstration that oligodendrocyte progenitors simultaneously expressing receptors for both bFGF and PDGF-AA are present in normal adult CNS. Since in vitro bFGF and PDGF-AA in combination induce oligodendrocyte progenitors from normal adult CNS to undergo rapid proliferation and migration, the in situ coexpression of FGFRs and PDGFalphaR supports the hypothesis that oligodendrocyte progenitors can respond to bFGF and PDGF-AA in situ, and that both growth factors may be critical for repopulation of demyelinated lesions during remyelination.