Effect of alendronate on resorption of transplanted bone in mice

Alendronate, one of the bisphosphonates, is known to have an inhibitory effect on bone resorption. The purpose of study was to investigate the effects of alendronate on ectopic bone graft resorption and to determine the optimal dose in the mouse. In control group, segments of chopped tarsal bone were immersed in saline solution and auto-grafted. In experimental groups, the same bone segments were immersed in alendronate ranging in concentration from 10(-4) to 10(-6)M prior to transplantation. The grafted bone in the control group disappeared due to resorption by osteoclasts within 5 weeks. In the experimental groups, the area of bone tissue decreased by only 20-40% at 5 weeks post-operatively. The transplanted bone volume in alendronate-treated groups exhibited a tendency of dose-dependent increase, being highest in the 10(-4)M group. The number of osteoclasts was significantly less in the alendronate-treated groups than in the controls. These results suggested that the alendronate inhibits resorption of ectopic bone graft at a concentration of 10(-4) to 10(-6) M.