MicroRNA-34a-3p inhibits proliferation of rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease characterized by synovial inflammation. Fibroblast-like synoviocytes (FLS) serve a vital role in the initiation and perpetuation of the immune response in patients with RA. The present study aimed to investigate the potential role of microRNA (miR)-34a-3p in the pathogenesis of RA. FLS were collected from patients with RA and osteoarthritis (OA). The miR-34a-3p mimics and inhibitor vectors were constructed and transfected into RAFLS using Lipofectamine(®) 2000. Cell proliferation was determined by Cell Counting kit-8 assay and cell cycle progression was analyzed by flow cytometry. In addition, the expression levels of cell cycle control genes, matrix metalloproteinase (MMP)-1 and MMP-9, and pro-inflammatory cytokines were detected by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The potential targets of miR-34a-3p were predicted by TargetScan and MiRWalk; the target genes were further verified using a luciferase reporter assay. The expression levels of miR-34a-3p were generally lower in RAFLS compared with in OAFLS. miR-34a-3p overexpression significantly inhibited the proliferation of FLS (P<0.01) by suppressing the expression levels of cyclin-dependent kinase 2, cell division cycle 25A and cyclin D1 (P<0.01), and arresting FLS cell cycle progression at the G(1) phase. Furthermore, the expression levels of MMP-1 and 9 were markedly decreased, as were the mRNA and protein expression levels of pro-inflammatory cytokines (tumor necrosis factor α and interleukin 6; P<0.01). Murine double minute 4 (MDM4) was predicted and verified as a potential target gene of miR-34a-3p; the 547–554 nt position of the MDM4 3′-untranslated region harbored one potential binding site for miR-204-3p. The results of the present study indicated that miR-34a-3p may be considered a promising therapeutic target for RA through inhibiting FLS proliferation and suppressing the production of pro-inflammatory cytokines and MMPs.