Correlation of changes in the mandible and retina/choroid vasculature of a rat model of BRONJ.

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) causes bones of the mandible and maxilla to become necrotic and protrude into the oral cavity. Compromised blood supply to bone is also a feature of BRONJ. The design of this study was first to use our established technique of molar extraction and IV bisphosphonate injection to produce features of BRONJ in rats that mimic the human disease; second to confirm vascular changes in the mandible and eye using micro-CT of vascular casts, and image analysis of retina/choroid images; and third to show parallel bisphosphonate-induced changes in the structure and markers of the vasculature of the bone and eye. The results of this study show structural changes in the eye and mandible as well as biochemical changes including the up-regulation of VEGF in response to the bisphosphonate-associated ischemia. These changes are not associated with angiogenesis in either the eye or mandible as determined by reduced vascular complexity. These results suggest that observations of direct changes to the vasculature in the retina/choroid structures of the eye in patients taking bisphosphonates could serve as a window to the progression of debilitating changes occurring as a result of bisphosphonate therapy.