Interleukin-1B IS essential for blood-induced cartilage damage in vitro

Abstract

Purpose: Exposure of joint cartilage to blood can occur after joint trauma, during or after major joint surgery, or due to hemophilia. This ultimately leads to joint damage, both by direct effects of blood on cartilage and via synovial inflammation. Cartilage destruction is considered to result from both cartilage matrix-degrading proteases as well as cartilage-destructive pro-inflammatory cytokines such as IL1β. To unravel the role of IL1β in the pathogenesis of blood-induced cartilage damage, we investigated whether direct blocking of IL1β specifically prevents blood-induced cartilage damage in vitro. Methods: Full thickness healthy human articular cartilage explants, obtained post-mortem, were cultured for 4 days in presence or absence of 50% v/v whole blood. A recombinant human IL1β monoclonal antibody (IL1β mAb) was only added during blood exposure in a concentration of 0, 1, 2, 10, 30, or 100 ng/mL. Cartilage matrix proteoglycan turnover was determined 12 days later to analyse long-term effects. Moreover, to investigate the direct effects of IL1β mAb on cartilage, explants were cultured for 4 days in the presence of 10 ng/mL IL1β mAb in the absence of blood. Results: Exposure to blood decreased the proteoglycan-synthesis rate (-62%) and proteoglycan content (-19%), and increased the proteoglycan release (+191%, all p < 0.05). Adding IL1βmAb resulted in a dose-dependent increase of the proteoglycan synthesis rate leading to normalisation at higher concentrations (see figure A). Moreover, proteoglycan release was statistically significantly decreased from a concentration of 3ng/mL and above (see figure B). Similar, the proteoglycan content increased statistically significantly upon addition of the IL1βmAb (3 ng/mL and above; all p < 0.05). In the absence of blood, IL1βmAb did not have direct effects on cartilage proteoglycan turnover (p = 0.51). Conclusions: This study demonstrates that IL1β is a crucial factor in the development of blood-induced cartilage damage in vitro. Blocking this pro-inflammatory cytokine with a monoclonal antibody protects cartilage from the damaging effects of blood exposure. Further research is warranted to investigate the in vivo capacity of IL1β mAb in prevention and its position as a treatment of hemophilic arthropathy.