Inhibition of BMP3 increases the inflammatory response of fibroblast-like synoviocytes in rheumatoid arthritis

Rheumatoid arthritis (RA) is a persistent autoimmune disease. Fibroblast-like synoviocytes (FLS) are a key component of invasive pannus and a pathogenetic mechanism in RA. Expression of bone morphogenetic protein 3 (BMP3) mRNA is reportedly decreased in the arthritic synovium. We previously showed that BMP3 expression is significantly downregulated in the synovial tissues of RA patients and models of adjuvant-induced arthritis (AIA). In the present study, we explored the association between BMP3 and FLS migration and secretion of proinflammatory factors in RA. We found that inhibition of BMP3 expression using BMP3 siRNA increased the proinflammatory chemokines and migration of FLS stimulated with TNF-α. Inhibition of BMP3 expression also increased expression of IL-6, IL-1β, IL-17A, CCL-2, CCL-3, VCAM-1, MMP-3, and MMP-9, but not TIMP-1, in AIA and RA FLS. Correspondingly, induction of BMP3 overexpression through intra-articular injection of ad-BMP3 diminished arthritis severity in AIA rats. We also found that BMP3 may inhibit activation of TGF-β1/Smad signaling. These data indicate that BMP3 may suppress the proliferation and migration of FLS via the TGF-β1/Smad signaling pathway.