OP0224 Adamts-12 protects against inflammatory arthritis through interacting with proinflammatory ctgf

Background It has been reported that a disintegrin and metalloproteinase with thrombospondin motifs-12 (ADAMTS-12) is a susceptibility gene for rheumatoid arthritis (RA) development, and its level was significantly increased in RA patients. In addition, ADAMTS-12 was also reported to be required for normal inflammation. Objectives This study aims to determine the role of ADAMTS-12 and the underlying mechanisms in the pathogenesis of inflammatory arthritis. Methods Collagen-induced arthritis (CIA) was established in ADAMTS-12-/- mice and their control littermates to determine the role of ADAMTS-12 in vivo. Connective tissue growth factor (CTGF) deficient Raw264.7 were used to determine their functional interplays. Protein-protein interaction assays were performed to detect the interactions of ADAMTS-12 with CTGF Results ADAMTS-12-/- mice are more susceptible to collagen-induced arthritis. Accelerated disease onset, significant increase in the arthritis score and arthritis incidence, were observed in ADAMTS-12-/- mice (figure 1a). Histological analysis of whole ankle joints demonstrated a significant increase in synovitis, destruction of bone and cartilage loss in ADAMTS-12-/- mice. ELISA results indicated that ADAMTS-12-/- CIA mice exhibited enhanced release of pro-inflammatory and reduced secretion of anti-inflammatory cytokine. Collectively, these data demonstrate that ADAMTS-12-/- renders mice highly susceptible to CIA. ADAMTS-12 interacts with and cleaves CTGF, and ADAMTS-12-mediated signalling depends on CTGF during inflammation. It is known that CTGF plays a pro-inflammatory role in the pathogenesis of inflammatory arthritis. We co-transfected CTGF and ADAMTS-12 into 293 T cells and found ADAMTS-12 bound to (figure 1b) and digested CTGF (figure 1c). In vivo studies also demonstrated that CTGF was accumulated in the synovium of ADAMTS-12-/- CIA mice. To further determine whether CTGF is a critical regulator of ADAMTS-12 mediated signalling, we generated CTGF deficient Raw264.7. Overexpression of ADAMTS-12 and CTGF deficiency could decrease the activation of inflammatory signalling markers such as NFkb, p38 and JNK in response to IL-1β at a comparable level. More importantly, overexpression of ADAMTS-12 in CTGF deficient Raw264.7 failed to further inhibit the activation of these signal molecules as compared to CTGF deficient Raw264.7 (figure 1f). Taken together, these results suggest that CTGF is a critical regulator of ADAMTS-12 mediated signalling during inflammation. Blocking CTGF attenuates inflammatory arthritis in ADAMTS12-deficient CIA mice model. To determine whether the accelerated inflammation in ADAMTS-12-/- mice resulted from the accumulated CTGF, we administered CTGF antibody to ADAMTS-12-/- CIA model after disease onset. The arthritis score in ADAMTS-12 deficient mice was significantly reduced in presence of CTGF antibody (figure 1d). Moreover, histological analysis indicated CTGF abrogated further tissue destruction and inflammation (figure 1e). Conclusions ADAMTS-12-mediated regulation of inflammatory arthritis is probably through, at least in part, its interplay with CTGF and blockage of CTGF has been shown to be effective in treating inflammatory arthritis. Disclosure of Interest None declared