Roles of microRNA-539 and osteopontin in rheumatoid arthritis

The present study aimed to investigate the role and mechanism of microRNA-539 (miR-539) in rheumatoid arthritis (RA). A total of 68 RA patients and 46 osteoarthritis patients were enrolled into the current study. Peripheral blood and joint fluid were collected prior to treatment. Reverse transcription-quantitative polymerase chain reaction was performed to detect osteopontin (OPN) mRNA and miR-539 expression levels, while ELISA and western blot analysis were applied to detect OPN protein expression. In addition, bioinformatics analysis predicted that miR-539 directly targeted OPN, while dual-luciferase assay was used to validate this finding. Furthermore, agomiR-539 transfection and OPN knockdown by siRNA were conducted in MH7A cells, and MTT assay was used to detect MH7A cell proliferation. The results indicated that OPN was significantly increased in the blood and joint fluid of RA patients, while miR-539 expression was significantly decreased in the two types of specimens (P<0.05). Subsequent to silencing OPN by siRNA, the proliferation of MH7A cells was decreased (P<0.05). Following upregulation of miR-539, OPN expression was significantly decreased and cell proliferation was inhibited. Dual-luciferase assay revealed that miR-539 regulated OPN expression through complementary binding to 3'-untranslated region. OPN was also significantly increased in the blood and joint fluid of RA patients, which may be associated with the downregulation of miR-539. Thus, miR-539 may promote the development and progression of RA through regulating OPN.