Combining miR-23b exposure with mesenchymal stem cell transplantation enhances therapeutic effects on EAE

•Treatment of mice with BMSCs over-expressing miR-23b provided better synergistic and longer-term therapeutic effects than treatment with traditional BMSCs.•Over-expression of miR-23b enhanced the ability of BMSCs to inhibit differentiation of Th17 cells and reduced IL-17 secretion.•Compared to traditional BMSCs, the miR-23b over-expressing BMSCs exhibited enhanced secretion of TGF-β1, a cytokine that promotes the differentiation of Treg cells.•Pathologically, miR23b-BMSC transplantation delayed EAE by reducing the Th17/Treg cell ratio and inhibiting inflammatory cell infiltration, thus slowing spinal cord demyelination. Bone marrow mesenchymal stem cells (BMSCs) have the immuno-modulatory capacity to ameliorate autoimmune diseases, such as multiple schlerosis (MS), systemic lupus erythematosus and rheumatoid arthritis. However, BMSC-mediated immunosuppression can be challenging to achieve. The efficacy of BMSC transplantation may be augmented by an adjuvant therapy. Here, we demonstrated that treatment of mice with experimental autoimmune encephalomyelitis (EAE), a model of MS, with BMSCs over-expressing microRNA (miR)-23b provided better synergistic and longer-term therapeutic effects than treatment with traditional BMSCs. Over-expression of miR-23b enhanced the ability of BMSCs to inhibit differentiation of Th17 cells and reduced IL-17 secretion. Compared to traditional BMSCs, the miR-23b over-expressing BMSCs (miR23b-BMSCs) exhibited enhanced secretion of tumor growth factor beta 1 (TGF-β1), a cytokine that promotes the differentiation of regulatory T (Treg) cells. Pathologically, miR23b-BMSC transplantation delayed EAE progression, apparently by reducing the Th17/Treg cell ratio and inhibiting inflammatory cell infiltration across the blood-brain barrier, and thus slowing spinal cord demyelination. These results may lead to better utility of BMSCs as a treatment for autoimmune diseases.