Local Application of Alendronate on β-Tricalcium Phosphate Accelerated Induction of Osteogenesis with Formation of Giant Osteoclast-Like Cell

Intrinsic osteoinductivity—the ability to induce bone formation in ectopic sites without addition of osteogenic factorshas been reported in various porous materials. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells are thought to play an important role in material-induced osteoinduction. To investigate the influence of osteoclastic activity on intrinsic osteoinduction, we loaded alendronate (10, 10, and 10 M) onto porous β-tricalcium phosphate (β-TCP) blocks to inhibit osteoclastic activity, and evaluated osteoinductivity by implantation of the blocks into the dorsal muscles of adult beagle dogs. Alendronate-loaded porous β-TCP blocks increased both speed and amount of osteoinduction, as measured 4 weeks after implantation, with the 10 M alendronate-loaded β-TCP being especially active. This finding indicates that β-TCP loaded with 10 M alendronate might prove crucial in providing the desirable balance between the degradation rate of bone scaffolds and their osteoinductive replacement. Thus, material-induced osteoinduction may be controlled by local application of alendronate, establishing alendronate loading as a promising therapeutic approach.