[Animal models for bone and joint disease. RANKL-injected bone loss model]

Discovery of the osteoclast differentiation factor RANKL (receptor activator of NF-κB ligand) has opened a new era in the understanding of mechanisms in osteoclast differentiation over the last decade. The discovery results in the development of a fully human anti-RANKL neutralizing monoclonal antibody (called denosumab) and denosumab has been approved for the treatment of osteoporosis in Europe and the US. Here I review a novel rapid bone loss model with GST (glutathione-S-transferase) -RANKL. Pharmacologic studies of candidates for the treatment of osteoporosis with this model can be done in short periods such as 3 days and a couple of weeks although it took several months in the conventional methods with ovariectomized (OVX) -rats. This model also is useful for the rapid analyses in the functions of osteoclasts in vivo . I am expecting the RANKL-induced bone loss model to be the gold standard in the animal osteoporosis model as well as OVX-rats in the near future.