Involvement of soluble receptor activator of nuclear factor-κB ligand (sRANKL) in collagenase-induced murine osteoarthritis and human osteoarthritis

Joint destruction and excessive bone formation are associated with high expression of soluble receptor activator of nuclear factor-kappa B ligand (sRANKL). This study was undertaken to investigate the role of sRANKL in collagenase-induced osteoarthritis (CIOA) in mice and in patients with osteoarthritis (OA). The initial phase of CIOA was associated with severe proteoglycan depletion, decreased collagen density, and up-regulation of bone morphogenetic protein (BMP)-2. At the late stage of CIOA, bone remodeling was related with increased BMP2 and RANKL expression in the joints, high sRANKL, and decreased number of activated neutrophils in synovium. CIOA mice showed elevated plasma level of sRANKL but low RANKL expression on blood neutrophils. The percentage of RANKL-positive blood neutrophils was higher in patients with OA than in healthy individuals. Our data indicate that increased local and systemic levels of soluble RANKL might be indicative for OA disorders in mouse and human.