Disruption of the oligodendroglial miR-126a-3p– Pex5 axis inhibits remyelination in chronic demyelinating lesions

Insufficient maturation of oligodendrocyte progenitor cells (OPCs) contributes to the failure of endogenous remyelination in multiple sclerosis (MS). It remains unclear whether dysregulated oligodendroglial microRNAs (miRNAs) impede remyelination in chronic MS lesions. In this study, we demonstrated that miR-126a-3p was enriched in oligodendroglia from chronic inactive MS plaques and chronic lesions in mice with experimental autoimmune encephalomyelitis (EAE). Functional analyses revealed that miR-126a-3p inhibited OPC differentiation in vitro and that the specific deletion of miR-126a-3p in oligodendroglia accelerated the remyelination process in the EAE and lysolecithin-induced demyelination models. Mechanistically, miR-126a-3p exerted an inhibitory effect on OPC differentiation and remyelination by directly targeting peroxin-5 (Pex5) transcripts. A screening of a US Food and Drug Administration-approved drug library based on Pex5 levels led to the identification of ganciclovir, an antiviral agent, as a potent proremyelinating agent after in vivo demyelinating events. These results identify the aberrant miR-126a-3p-Pex5 axis in oligodendroglia as a potential therapeutic target to facilitate remyelination in chronic MS lesions.