The effects of chronic zoledronate usage on the jaw and long bones evaluated using RANKL and osteoprotegerin levels in an animal model

The discovery of the receptor activator of nuclear factor kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) system (RANK/RANKL/OPG system) has been one of the most important advances in bone biology in the last decade. We investigated how the chronic application of bisphosphonate affects the RANKL and OPG levels in an animal model and whether this effect may be related to bisphosphonate-related osteonecrosis of the jaws (BRONJ). Thirty female Sprague–Dawley rats were used in this study. The rats were randomly divided into three groups (10 in each): Z, the zolendronate group, injected with zolendronate for 10 weeks; S, a control group, injected with saline solution for 10 weeks; and C, a control group, in which no injection was given. RANKL values in the tibia were increased in the Z group when compared with the two controls; however, the RANKL values in the mandible were decreased when compared with the controls. Although the differences did not reach statistical significance, the mandibular OPG values were increased in the Z group when compared with the C and S groups. The mechanism of RANKL negation and absence in osteoclastic activation could be a predisposing factor for the development of BRONJ.