miR-125a-5p regulates Treg function by targeting Foxp3 in experimental autoimmune myasthenia gravis mice

MicroRNAs are a class of endogenous noncoding small RNAs. miR-125a-5p is involved in immunoregulatory mechanisms in autoimmune diseases. Myasthenia gravis (MG) is an autoimmune disease in which regulatory T cells (Tregs) exhibit reduced numbers and functional defects, with decreased expression of the Treg cell-specific transcription factor Foxp3. Our previous study identified an abnormally high expression of miR-125a-5p in thymoma-associated myasthenia gravis, however, the involvement of miR-125a-5p in the pathogenesis of myasthenia gravis in vivo is unclear. In this study, we explored the role of thymic miR-125a-5p abnormalities in the pathogenesis of myasthenia gravis by establishing an experimental autoimmune myasthenia gravis model. Muscle strength score, low-frequency repetitive nerve stimulation, and serum acetylcholine receptor antibody were performed. The relative expression of miR-125a-5p and Foxp3 in the thymus and spleen was quantified, and the percentage of Treg cells, the levels of the inhibitory cytokines IL-10 and TGF-β1, and the proliferative capacity of splenic T lymphocytes were detected. Our findings revealed significant upregulation of miR-125a-5p expression in myasthenia gravis models. Reducing miR-125a-5p levels alleviated muscle weakness symptoms, elevated Foxp3 expression, enhanced the number of Treg cells, elevated the levels of the Treg-associated inhibitory cytokines IL-10 and TGF-β1, and inhibited the proliferative function of splenic T lymphocytes. The opposite result was obtained when miR-125a-5p was overexpressed. These results suggest that miR-125a-5p can inhibit Foxp3 expression, leading to a decrease in the number and abnormal function of Treg cells. Thus, our findings suggest that miR-125a-5p participates in the pathogenesis of myasthenia gravis by targeting Foxp3 to regulate the function of Treg cells, providing new insights to explore the immunoregulatory mechanisms of miR-125a-5p in myasthenia gravis.