TNF-α Promotes Synovial Inflammation and Cartilage Bone Destruction in Rheumatoid Arthritis via NF-κB/YY1/miR-103a-3p Axis.

Tumor necrosis factor alpha (TNF-α) plays important roles in inflammation and bone destruction in rheumatoid arthritis (RA), but the detailed mechanism is still not fully elucidated. Here, we found that the levels of microRNA (miR)-103a-3p were decreased markedly in the inflamed synovial tissues of patients with RA compared with osteoarthritis (OA) or healthy control subjects. Further studies uncovered that miR-103a-3p was significantly downregulated by TNF-α/IL-1β in RA fibroblast-like synoviocytes (FLSs) through an NF-κB-dependent manner via the de novo produced transcription factor Yin Yang 1 (YY1). In addition, downregulation of miR-103a-3p in FLSs promoted NF-κB signaling pathway activation, inflammatory cytokines secretion, and bone marrow-derived monocytes (BMMs) cells differentiation into osteoclasts, whereas ectopic expression of miR-103a-3p had the opposite effects. Notably, miR-103a-3p was downregulated thousands of times in the sera of RA patients and CIA mice, while the blockade of TNF-α with infliximab greatly recovered its levels in RA patients in sustained remission. Consistently, rescue of miR-103a-3p expression by an agomiR potently ameliorated inflammatory responses and bone erosion in CIA mice. Mechanistically, mitogen-activated protein kinase kinase kinase 7 (MAP3K7) and Dickkopf-related protein 1 (DKK1) were identified as the direct targets of miR-103a-3p, by which it exerts the effects on synovial inflammation and cartilage bone destruction. Taken together, miR-103a-3p mediates TNF-triggered synovial inflammation and joint bone destruction via targeting MAP3K7 and DKK1; it thus serves as a candidate target for RA treatment.