Implantation of octacalcium phosphate combined with transforming growth factor-β₁ enhances bone repair as well as resorption of the implant in rat skull defects

In our previous study, we reported that synthetic octacalcium phosphate (OCP) enhances bone repair if implanted in rat skull defects. We hypothesized that OCP can be used as an effective carrier for transforming growth factor-β₁ (TGF-β₁) to promote bone repair. We designed the present study to investigate histomorphometrically whether combination with recombinant human TGF-β₁ could promote bone repair caused by OCP per se (Control/OCP). A full-thickness standardized trephine defect was made in the rat parietal bone and OCP combined with recombinant human TGF-β₁ (TGF-β₁/OCP) or Control/OCP was implanted into the defect. Four rats from each group were fixed at 2, 4, and 8 weeks after implantation. Histomorphometrical analysis of the percentage of newly formed bone (n-Bone %) and remaining implants (r-Imp %) in the defect was performed. The statistical analysis showed the n-Bone % of TGF-β₁/OCP was significantly higher than that of the Control/OCP in week 4, whereas the r-Imp % of TGF-β₁/OCP was significantly lower than that of the Control/OCP. The present study demonstrated that OCP can be used as an effective carrier for TGF-β₁ and their combination enhances bone repair as well as resorption of the carrier OCP in the early stage of bone formation.