Octacalcium phosphate combined with collagen orthotopically enhances bone regeneration

Octacalcium phosphate (OCP) is resorbable bone regenerative material, but its brittleness makes it difficult to maintain its shape without restraint. We have engineered a scaffold constructed of synthetic OCP and porcine collagen sponge (OCP/Collagen) and investigated whether OCP/Collagen composite could improve bone regeneration. To examine this hypothesis, bone regeneration by the implantation of OCP/Collagen was compared with those by OCP and collagen. Radiographic and histological examination was performed and the percentage of newly formed bone (n-Bone%) in the defect was determined by a histomorphometrical analysis. OCP/Collagen, OCP, or collagen was implanted into the critical-sized defects in rat crania and fixed at 2, 4, or 8 weeks after implantation. OCP/Collagen improved the handling performance than the granules of OCP, and synergistically enhanced the bone regeneration beyond expectation, which were composed of bone nucleation by OCP and cell infiltration by collagen. Histomorphometrical analysis showed that n-Bone% +/- standard error treated with OCP/Collagen (48.4 +/- 5.14) was significantly higher than those with OCP (27.6 +/- 4.04) or collagen (27.4 +/- 5.69) in week 8. The present study suggests that the combination OCP with collagen elicited the synergistic effect for bone regeneration.