Background
Receptor activator of nuclear factor-κB ligand (RANKL), a member of tumor necrosis factor (TNF)-α, is produced by osteoblasts (Obs) and stimulates its receptor RANK on osteoclast (Oc) progenitors to differentiate them to osteoclasts. WP9QY peptide designed to mimics TNF receptor's contact site to TNF-α was known to abrogate osteoclastogenesis in vitro by blocking RANKL-RANK signaling. WP9QY ameliorated collagen-induced arthritis and osteoporosis in mouse models. Here we report that the peptide surprisingly exhibited bone anabolic effect in vitro and in vivo.