Icariin enhances remyelination process after acute demyelination induced by cuprizone exposure

Pathology are still progressive and cumulative in the remission course of relapsing-remitting MS (RRMS), thus drug treatment during the remission period may play a great role for the regeneration of the myelin sheath. C57BL/6 mice were fed with cuprizone (CPZ, 0.2% w/w) for 5 weeks to induce acute demyelination and oligodendrocytes degeneration, after which CPZ was withdrawn to allow recovery. Icariin (ICA, 6.25, 12.5 and 25mg/kg/day), vehicle (0.5% sodium carboxymethyl cellulose solution) or water was administrated orally to mice for 1 week after CPZ withdrawal. Luxol-fast blue (LFB), immunohistochemical or immunofluorescence staining was used to detect morphological and biological changes in the brains. CPZ administration for 5 weeks resulted in completely demyelination and remyelination occurred when CPZ was withdrawn. ICA treatment during the recovery period for 1 week significantly improved myelin restoration, enhanced NF200-positive axons repair, increased the number of APC⁺/Olig2⁺ mature oligodendrocytes and prevented neuron-derived neurotrophic factor such as nerve growth factor (NGF) loss. Our results demonstrated that ICA treatment during the recovery period promotes remyelination and axon rewrapped, at least, in part, by promoting oligodendrogenesis and neurotrophic factor production.