Circulating miR-320b Contributes to CD4+ T-Cell Proliferation in Systemic Lupus Erythematosus via MAP3K1

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies and tissue inflammation. Mesenchymal stem cells (MSCs) have emerged as a promising candidate therapy for SLE owing to the immunomodulatory and regenerative properties. Circulating miRNAs are small, single-stranded noncoding RNAs in a variety of body fluids that regulate numerous immunologic and inflammatory pathways. Recent studies have revealed many differentially expressed circulating miRNAs in autoimmune diseases including SLE. However, the role of circulating miRNAs in SLE has not been extensively studied. Here, we performed small RNA sequencing analysis to compare the circulating miRNA profiles of SLE patients before and after MSC transplantation (MSCT), and identified a significant decrease of circulating miR-320b level during MSCT. Importantly, we found that the expression of circulating miR-320b and its target gene MAP3K1 was closely associated with SLE disease activity. The in vitro experiments showed that decreased MAP3K1 level in SLE peripheral blood mononuclear cells (PBMCs) was involved in CD4+ T-cell proliferation. In MRL/lpr mice, miR-320b overexpression aggravated symptoms of SLE, while miR-320b inhibition could promote disease remission. Besides, MSCs regulate miR-320b/MAP3K1 expression both in vitro and in vivo. Our results suggested that circulating miR-320b and MAP3K1 may be involved in CD4+ T-cell proliferation in SLE. This trial is registered with NCT01741857.