Porous Carbonate Apatites as Growth Factor Carrier for Bone Graft

“Objectives:” Carbonate apatite (CAP) is osteoclastic resorbable bone substitute for tissue engineering. Recentry, we have developed the porous form CAP for the scaffold for growth factor and stem cells. In this study, porous CAP with interpore connections was developed a growths factor carrier and animal study was performed to ascertain whether the bone augmentation of bone defects could be accelerated by an application of basic fibroblast growth factor (bFGF) with porous CAP.

“Methods:” Femur bone defects (4.3mm in diameter) were made surgically in wistar rats and porous CAP containing 0, 5, or 50ng of bFGF was placed in the defect. Bone augmentation was evaluated radiographically using m-CT and histologically with HE staining at 2 and 12 weeks after the operation.

“Results:” From m-CT images of CAP samples before animal experiment, it was found that porosity of porous CAP material was 52.1% and macro pore size was in the range of 350~500mm, which was adequate for bone to ingrowth in the pores. At 2 weeks postoperatively, new bone was evident in the defect sites with CAP containing either 5ng or 50ng bFGF. The area of regenerated bone, however, was significantly higher with CAP containing 5ng than with CAP containing 50ng. At 12 weeks after implantation, no difference was found between CAPs containing 5ng and 50ng in new bone formation. CAPs containing bFGF, however, remarkably increased the amount of bone newly formed as compared with CAP without bFGF. Regardless of the implantation periods, TRAP-positive cells were visible around material, indicating that osteoclast-like cells were resorbing CAP. In accordance with the evidence, bioresorption of the material increased with time, 6.3-7.8% at 2 weeks to 9.1-11.5% at 12 weeks.

“Conclusion:” These results demonstrate that porous CAP can be useful scaffold for growth factors and stem cells for bone augmentation.