LAUSR

Our purpose is to study the roles of microRNA‐338‐5p (miR‐338‐5p) on the proliferation, invasion, and inflammatory response of fibroblast‐like synoviocytes (SFs) in rheumatoid arthritis patients by regulating SPRY1. The target relationship between miR‐338‐5p and SPRY1 was validated through luciferase reporter system. The expression of miR‐338‐5p and SPRY1 in synovial tissues and synovial cells were detected using RT‐PCR and western blot. The mimics and inhibitors of miR‐338‐5p were transfected into SFs. MTT, Transwell, and ELISA assays were used to analyze cell proliferation, invasiveness, and the secreted extracellular pro‐inflammatory cytokines (such as IL‐1a, IL‐6, COX2) levels of SFs. MiR‐338‐5p was highly expressed in rheumatoid arthritis tissues and cells, and directly down‐regulated the expression of SPRY1 in the SFs of rheumatoid arthritis patients. Cell proliferation, invasiveness and the expression level of pro‐inflammatory cytokines in synovial cells increased after the transfection of miR‐338‐5p mimics, while the proliferation, invasion and expression level of pro‐inflammatory cytokines decreased after the transfection of miR‐338‐5p inhibitors. In conclusion,miR‐338‐5p promoted the proliferation, invasion and inflammatory reaction in SFs of rheumatoid arthritis by directly down‐regulating SPRY1 expression. J. Cell. Biochem. 118: 2295–2301, 2017. © 2017 Wiley Periodicals, Inc.