Overexpression of miR-146a-5p and miR-221-3p in Human Synovial MSC-like Cells Favoured the Expression of Pro-Inflammatory Mediators in an In Vitro Model of Rheumatoid Arthritis.

In rheumatoid arthritis (RA), activated synovial tissue-derived mesenchymal stem cells (MSC) acquire a pathogenic phenotype and produce pro-inflammatory cytokines, chemokines, metalloproteinases, pro-osteoclastic and pro-angiogenic factors. The acquisition of this aggressive phenotype might be due to modified expression of micro-RNAs. We aimed to clarify the role of specific micro-RNAs (miR-146a-5p, miR-221-3p, miR-34a-3p, miR-150, miR-203a-3p and miR-155-3p) in an in vitro model of RA. Methods: Micro-RNA expression was determined in RA patient plasma and in commercial human synovial tissue-derived MSC-like cells stimulated with a panel of pro-inflammatory mediators (poly I:C, TNF-α, IL-1β, IFN-γ) to mimic the rheumatoid arthritis pathogenic setting. Next, unstimulated cells or TNF-α stimulated cells were transfected with miR-146a-5p mimic or miR-221-3p mimic. Protein and/or mRNA expressions of chemokines, cytokines, VEGF, MMPs and RANKL were determined by ELISA or qRT-PCR. MiR-34a-3p, miR-146a-5p, miR-150, miR-221-3p and miR-203a-5p were upregulated in RA patient plasma versus healthy controls. Moreover, synovial tissue-derived MSC-like cells expressed miR-146a-5p and miR-221-3p in response to pro-inflammatory mediators. Overexpression of miR-146a-5p increased CCL2 and CXCL8 expression and miR-221-3p increased IL-1β and IL-6 expression in synovial tissue-derived MSC-like cells stimulated with TNF-α. Conclusion: Overexpression of miR-146a-5p and miR-221-3p might favour inflammation and participate in rheumatoid arthritis pathogenesis.