MicroRNA-181c promotes Th17 cell differentiation and mediates experimental autoimmune encephalomyelitis

Among T helper (Th) cell subsets differentiated from naive CD4⁺ T cells, IL-17-producing Th17 cells are closely associated with the pathogenesis of autoimmune diseases, including multiple sclerosis (MS) and the MS animal model, experimental autoimmune encephalomyelitis (EAE). The modulation of Th17 differentiation offers a potential avenue for treatment. Although a series of microRNAs (miRNAs) that modulate autoimmune disease development have been reported, further studies on miRNA roles in Th17 differentiation and MS pathogenesis are still warranted. Here, we demonstrated that mice with miR-181c knockdown presented with delayed EAE and slowed disease progression, along with a decreased Th17 cell population. We also found that miR-181c was a Th17 cell-associated miRNA and that Smad7, a negative regulator of TGF-β signaling, was a potential target of miR-181c. miR-181c knockdown rendered T cells less sensitive to TGF-β-induced Smad2/3, enhancing the expression of IL-2 which has been reported to inhibit Th17 cell differentiation. Moreover, through the analysis of published miRNA expression profiles from the Gene Expression Omnibus database, increased miR-181c levels were found in peripheral blood from MS patients. Our results identified a novel miRNA that promotes Th17 cell differentiation and autoimmunity, thus miR-181c may serve as a potential treatment target in patients with MS.