Teriflunomide Attenuates Demyelination and Enhances Remyelination in Organotypic Brain Slice Cultures Through Modulation of Glial Cell Dynamics

OBJECTIVES: Teriflunomide has been proven to be effective in the therapy of relapsing-remitting multiple sclerosis (RMS). In an approach to better elucidate the mode of action of teriflunomide in the central nervous system (CNS), we aimed here to clarify the role of teriflunomide on glial cells using an ex vivo demyelination model. METHODS: Organotypic cerebellar slice cultures (OSC) were cultivated from 10-day-old mice and left to fully myelinate for another 7 days. Demyelination was induced by lysolecithin (LPC) and was studied by immunohistochemistry against myelin proteins and electron microscopy. Glial cell responses were investigated by immunohistochemistry. Intra-glia interactions were studied using primary rodent glial cell cultures. RESULTS: Teriflunomide treatment did not affect developmental myelination but attenuated myelin degradation induced by LPC, as assessed by myelin basic protein and myelin oligodendrocyte glycoprotein immunoreactivity. During demyelination, teriflunomide treatment was associated with reduced microglial cell density and proliferation. Partial depletion of microglia using the CSF-1R inhibitor BLZ945 resulted in a similar preservation of myelin, supporting a functional association between microglial abundance and the extent of myelin loss in this model. Quantitative ultrastructural analysis further supported preserved myelin structures in teriflunomide-treated slices. Spontaneous remyelination was improved and enhanced numbers of oligodendrocytes were detected following teriflunomide treatment in OSC. However, direct cytoprotective/pro-proliferative effects of teriflunomide on oligodendroglia were not observed in primary glial cultures. There were also no indirect effects of teriflunomide-treated microglia on oligodendrocyte progenitor cells in vitro. CONCLUSIONS: Teriflunomide exerts beneficial effects on myelin preservation and remyelination in an ex vivo demyelination model, potentially through modulation of glial cell dynamics rather than direct effects on oligodendroglial cells.