Octacalcium phosphate effects on the systemic and local factors that regulate bone-cell activity

Octacalcium phosphate (OCP) exhibits excellent bone regenerative properties due to the biological activity of OCP crystals that promote responses from cells surrounding bone. We have found that OCP can enhance differentiation of osteoblasts and osteocytes, as well as formation of osteoclasts. These cellular responses activate bone remodeling following the implantation of OCP crystals in animal models and contribute to the superior biodegradability and osteoconductivity of OCP. In addition, OCP promotes migration of macrophages and production of proinflammatory cytokines to induce bone formation. OCP can also stimulate chondrocytes and odontoblasts. Interestingly, these diverse cellular responses induced by OCP are affected by physicochemical changes that accompany the conversion of OCP to hydroxyapatite. A better understanding of the mechanisms by which OCP affects bone-cell activity would contribute to the development of improved bone-substitute materials.