Oligodendrocyte-specific deletion of FGFR2 ameliorates MOG35-55 -induced EAE through ERK and Akt signalling

Abstract

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in demyelinating pathologies including multiple sclerosis (MS). In our recent study, oligodendrocyte-specific deletion of FGFR1 resulted in a milder disease course, less inflammation, reduced myelin and axon damage in EAE. The objective of this study was to elucidate the role of oligodendroglial FGFR2 in MOG_35-55 -induced EAE. Oligodendrocyte-specific knockout of FGFR2 (Fgfr2^ind-/- ) was achieved by application of tamoxifen; EAE was induced using the MOG_35-55 peptide. EAE symptoms were monitored over 62 days. Spinal cord tissue was analysed by histology, immunohistochemistry and western blot. Fgfr2^ind-/- mice revealed a milder disease course, less myelin damage and enhanced axonal density. The number of oligodendrocytes was not affected in demyelinated areas. However, protein expression of FGFR2, FGF2 and FGF9 was downregulated in Fgfr2^ind-/- mice. FGF/FGFR dependent signalling proteins were differentially regulated; pAkt was upregulated and pERK was downregulated in Fgfr2^ind-/- mice. The number of CD3(+) T cells, Mac3(+) cells and B220(+) B cells was less in demyelinated lesions of Fgfr2^ind-/- mice. Furthermore, expression of IL-1β, TNF-α and CD200 was less in Fgfr2^ind-/- mice than controls. Fgfr2^ind-/- mice showed an upregulation of PLP and downregulation of the remyelination inhibitors SEMA3A and TGF-β expression. These data suggest that cell-specific deletion of FGFR2 in oligodendrocytes has anti-inflammatory and neuroprotective effects accompanied by changes in FGF/FGFR dependent signalling, inflammatory cytokines and expression of remyelination inhibitors. Thus, FGFRs in oligodendrocytes may represent potential targets for the treatment of inflammatory and demyelinating diseases including MS.

Keywords: FGF/FGFR signalling; experimental autoimmune encephalomyelitis; multiple sclerosis; oligodendrocytes.