MiR-300 promotes the proliferation, migration and invasion of fibroblast-like synoviocytes in rheumatoid arthritis by targeting IL-37

Abstract Background Fibroblast-like synoviocytes (FLS) are crucial regulators in the pathogenesis of rheumatoid arthritis (RA). Reportedly, microRNA (miR) participates in regulating the pathogenesis of RA. In this study, we explored the regulatory effects of miR-300 on the proliferation, migration and invasion of FLS, which were obtained from RA patients. Methods qPCR was utilized to detect miR-300 expression and interleukin-37 (IL-37) mRNA expression in the synovial tissue of RA patients and healthy controls. Cell counting kit-8 (CCK-8) assay and Transwell assay were performed to investigate the regulatory function of miR-300 on the proliferation, migration and invasion of FLS. ELISA was employed to detect TNF-α, IL-6 and IL-8 levels, to evaluate the inflammatory response. Bioinformatics analysis and luciferase reporter assay were applied to validate the targeting relationship between miR-300 and IL-37. Western blot assay was executed to detect IL-37 protein expression in FLS. Results MiR-300 was revealed to be markedly down-modulated in the synovial tissue and FLS of RA patients; meanwhile, IL-37 expression was up-modulated. The transfection of miR-300 mimics enhanced RA-FLS growth, migration, invasion and inflammatory response; transfection of miR-300 inhibitors repressed the growth, migration, invasion and inflammatory response of RA-FLS. IL-37 was identified as a downstream target of miR-300, and IL-37 partially counteracted the enhanced growth, migration, invasion and inflammatory response of RA-FLS induced by miR-300. Conclusion MiR-300 facilitates growth, migration, invasion and inflammatory response of FLS by targeting IL-37, suggesting it was a crucial regulator in the pathogenesis of RA.