Anti–IL-20 monoclonal antibody inhibits the differentiation of osteoclasts and protects against osteoporotic bone loss

IL-20 is a proinflammatory cytokine of the IL-10 family that is involved in psoriasis, rheumatoid arthritis, atherosclerosis, and stroke. However, little is known about the role of IL-20 in bone destruction. We explored the function of IL-20 in osteoclastogenesis and the therapeutic potential of anti–IL-20 monoclonal antibody 7E for treating osteoporosis. Higher serum IL-20 levels were detected in patients with osteopenia and osteoporosis and in ovariectomized (OVX) mice. IL-20 mediates osteoclastogenesis by up-regulating the receptor activator of NF-κB (RANK) expression in osteoclast precursor cells and RANK ligand (RANKL) in osteoblasts. 7E treatment completely inhibited osteoclast differentiation induced by macrophage colony-stimulating factor (M-CSF) and RANKL in vitro and protected mice from OVX-induced bone loss in vivo. Furthermore, IL-20R1–deficient mice had significantly higher bone mineral density (BMD) than did wild-type controls. IL-20R1 deficiency also abolished IL-20–induced osteoclastogenesis and increased BMD in OVX mice. We have identified a pivotal role of IL-20 in osteoclast differentiation, and we conclude that anti–IL-20 monoclonal antibody is a potential therapeutic for protecting against osteoporotic bone loss.