Regulatory Effect of Bisphosphonates on Bidirectional Signaling Transduction of Bone Remodeling

Bisphosphonates are a group of agents used to treat malignant bone metastases and post-menopausal osteoporosis. The clinical efficacy of these agents in treating skeletal complications has been prevailingly used in medicine. However, growing number of cases have been reported with osteonecrosis of the jaws, emerging as a catastrophic complication in certain patients receiving bisphosphonates. Current studies concerning their pharmacokinetics are still limited. Future focus of research should concern the drug effects on bone homeostasis. In our first year project, we intend to use MC3T3-E1 mouse pre-osteoblasts to explore the regulatory effect of alendronate on the differentiation and proliferation of pre-osteoblasts. We will analyze the transcription factors of pre-osteoblasts differentiation, including Cbfa-1/Runx-2, osterix and osteocalcin. In addition, the technique of siRNA will also be used to determine the relation between Runx-2 and EphB4. In the second year, varied concentration of alendronate will be added to our osteoblast-osteoclast co-culture model. Rho-A, c-Fos and NFATc1 will be monitored as the biomarkers to establish the bidirectional ephrinB2-EphB4 signaling control. The paracrine alteration of OPG/RANKL will be measured in order to estimate the influence of alendronate on bone coupling effect. In the third year, we will inject the well-established post-menopausal model with alendronate intra-venously and observe its effect on calvarial bone healing. Bone marrow cells derived from the mice will be harvested and cultured to verify the postulated effect of bisphosphonate on bone coupling mechanism. We expect alendronate may regulate either side of bone remodeling, which includes depression of bone formation and bone resorption, at in vivo and in vitro levels. By further understanding of the underlying mechanism, we are able to find valuable strategy to prevent or treat the patients with post-menapausal osteoporosis or cancer suffering from BRONJ.