miR-155 promotes fibroblast-like synoviocyte proliferation and inflammatory cytokine secretion in rheumatoid arthritis by targeting FOXO3a

The present study aimed to explore the expression and effects of microRNA (miR)-155 in synovial fibroblasts of patients with rheumatoid arthritis (RA). A total of 89 synovial tissues from RA patients and 49 control synovial tissues were collected, and the levels of miR-155 were measured by reverse transcription quantitative-PCR and western blotting. Fibroblast-like synoviocytes (FLS) were isolated from synovial tissues from the control group and were used to evaluate the roles of miR-155 and forkhead box protein O3a (FOXO3a). MTT assay was used to measure the proliferation of FLS. The expression of miR-155 in RA synovial tissues was significantly higher than that in the control group, but the expression of FOXO3a was significantly lower. In RA synovial tissues, miR-155 expression was negatively correlated with FOXO3a expression, but was positively correlated with the release of inflammatory cytokines interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α). A dual-luciferase reporter system showed that miR-155 inhibited the expression of FOXO3a in FLS cells. miR-155 also promoted secretion of the inflammatory cytokines IL-1β, IL-6 and TNF-α by FLS and proliferation of these cells by targeting FOXO3a.