A novel modified RANKL variant can prevent osteoporosis by acting as a vaccine and an inhibitor

BACKGROUND: The discovery of receptor activator of nuclear factor‐ĸB ligand (RANKL) as the final effector in the pathogenesis of osteoporosis has led to a better understanding of bone remodeling. When RANKL binds to its receptor (RANK), osteoclastic differentiation and activation are initiated. Herein, we propose a strategy using a novel RANKL variant as a competitive inhibitor for RANKL. The RANKL variant activates LGR4 signaling, which competitively regulates RANK and acts as an immunogen that induces anti‐RANKL antibody production. METHODS: We modified the RANK‐binding site on RANKL using minimal amino acid changes in the RANKL complex and its counterpart receptor RANK and tried to evaluate the inhibitory effects on osteoclastogenesis. RESULTS: The novel RANKL variant did not bind RANK in osteoclast progenitor cells, but activated LGR4 through the GSK3‐β signaling pathway, thereby suppressing activated T cell cytoplasmic nuclear factor calcineurin‐dependent 1 (NFATc1) expression and activity during osteoclastogenesis. Our RANKL variant generated high levels of RANKL‐specific antibodies, blocked osteoclastogenesis, and inhibited osteoporosis in ovariectomized mouse models. Generated anti‐RANKL antibodies showed a high inhibitory effect on osteoclastogenesis in vivo and in vitro. CONCLUSIONS: We observed that the novel RANKL indeed blocks RANKL via LGR4 signaling and generates anti‐RANKL antibodies, demonstrating an innovative strategy in the development of general immunotherapy.