Mesenchymal Stem Cells Inhibited Dendritic Cells Via the Regulation of STAT1 and STAT6 Phosphorylation in Experimental Autoimmune Uveitis

Purpose: We have previously reported that MSCs inhibited experimental autoimmune uveitis (EAU) in rodent models induced by either uveitogenic antigens or antigen-specific T cells. In this study, we explored the inhibitory mechanisms of MSCs on dendritic cells (DCs) in EAU. Methods: We collected the DCs from the lymph nodes of MSC treated or untreated EAU rats, as well as bone marrow derived DCs cultured in vitro with or without MSC treatment. The levels of costimulatory molecules of CD80, CD86, CD40, OX40L and suppressors of cytokine signaling (SOCS1, SOCS2, and SOCS3) on these DCs were analyzed by flow Cytometry. The expression of CCR-7 and MMP-9 was examined by real time PCR and western blots. Total proteins of STAT1 and STAT6 signaling molecules and their phosphorylation were examined by western blots. ShRNA of STAT1 and STAT6 were respectively employed to explore the influence of STAT1 and STAT6 knockdown on DCs. Results: MSC treatment down-regulated the expression of CD80, CD86, CD40, and OX40L, as well as CCR-7 and MMP-9, but increased the levels of SOCS1, SOCS 2, and SOCS3 on DCs. STAT1 phosphorylation was reduced while STAT6 phosphorylation was enhanced in MSC treated DCs. Moreover, MSC treatment and STAT1 shRNA equally reduced CCR-7 and MMP-9 levels in DCs, and inhibited the proliferation of R16-specific T cells. In contrast, knockdown of STAT6 in DCs by STAT6 shRNA increased the expression of CD80 and CD86 and accelerated the proliferation of R16-specific T cells. Conclusion: MSCs inhibit DC maturation by regulating Stat1 and Stat6 phosphorylation in EAU.