microRNA-21 deletion impairs regulatory T cell function

Background: It has been found that miR-21 is increased in colonic tissues and decreased in peripheral blood regulatory T cells (Tregs) of patients with ulcerative colitis (UC). We aimed to investigate the influence of miR-21 on Tregs function in intestinal inflammation. Methods: Various CD4+ T cell populations were flow-cytometry sorted from miR-21-/- mice and littermates (WT) utilization in T-cell transfer colitis model and suppression of T cell activation and proliferation by Tregs. Gene expression was microarray-profiled and validated by qPCR, ELISA and immunofluorescence. miR-21 mimic and inhibitor studies and a 3’-untranslated region of SOCS5 luciferase report assay were used to validate the effect of miR-21. Results: As compared to their littermates, miR-21-/- mice have less Tregs in lymph nodes. miR-21-/- Tregs produced higher amount of SOCS5 and IFNγ, and lower amount of Jak3, Stat3, Stat5a, Foxp3, TGFβ1 and IL10. miR-21-/- Tregs reduced suppressive function in vitro and in vivo. Functional assays indicated that miR-21 could directly suppress SOCS5 expression. Conclusions: Expression and function of miR-21 are cell-type- and context- dependent. miR-21 deficiency result in impaired SOCS-JAK-STAT pathway activity in Tregs. miR-21 play a positive role in Tregs differentiation and suppressive function. Various CD4+ T cell populations were isolated by flow-cytometry sorting from mesenteric lymph nodes of Mir-21-/- mice (KO) and littermates (WT). Total RNAs were purified from these T cells for gene expression analysis. Gene expression profiles of the T cells were compared between Mir21-/- and WT to identify differentially expressed genes. Quantitative real-time qPT-PCR was used to validate the differential expression of genes.