Maresin 1 improves the Treg/Th17 imbalance in rheumatoid arthritis through miR-21

Objective Treg/Th17 imbalance plays an important role in rheumatoid arthritis (RA). Maresin 1 (MaR1) prompts inflammation resolution and regulates immune responses. We explored the effect of MaR1 on RA progression and investigated the correlation between MaR1 and Treg/Th17 balance. Methods Both patients with RA and healthy controls were recruited into the study. Collagen-induced arthritis (CIA) model was constructed to detect the clinical score, histopathological changes and Treg/Th17 ratio. Purified naive CD4+ T-cells were used to study the effect of MaR1 on its differentiation process and microRNA microarray studies were performed to investigate MaR1 downstream microRNAs in this process. MicroRNA transfection experiments were conducted by lentivirus to verify the mechanism of MaR1 on Treg/Th17 balance. Results Compared with controls, the MaR1 concentration was higher in the patients with inactive RA and lower in the patients with active RA. Expression of the Treg transcription factor FoxP3 was the highest in inactive RA and the lowest in active RA, while the Th17 transcription factor RORc showed a reverse trend. An inverse correlation was observed between the FoxP3/RORc ratio and Disease Activity Score 28. Intervention of MaR1 in the CIA model reduced joint inflammation and damage, and improved the imbalanced Treg/Th17 ratio. MaR1 increased Treg cells proportion while reduced Th17 cells proportion under specific differentiation conditions. Furthermore, miR-21 was verified as MaR1 downstream microRNA, which was upregulated by MaR1, modulating the Treg/Th17 balance and thus ameliorating the RA progression. Conclusions MaR1 is a therapeutic target for RA, likely operating through effects on the imbalanced Treg/Th17 ratio found in the disease.