Evaluation of Different Combinations of Biphasic Calcium Phosphate and Growth Factors for Bone Formation in Calvarial Defects in a Rabbit Model

The aim of the present preclinical study was to investigate the capability of a new formulation of biphasic calcium phosphate (BCP) in achieving new bone formation either by itself or in combination with different concentrations of growth factors. Twentyfour 3-month-old male New Zealand white rabbits (weight range, 2.5 to 3.0 kg) that had been bred exclusively for biomedical research purposes and obtained from a licensed vendor were used. Four calvarial defects were created in each animal, for a total of 96 defects. Each defect received alloplastic BCP (Osteon III, Genoss) that was composed of 60% hydroxyapatite and 40% β-tricalcium phosphate) (porosity, ~80%; macropore size, 200 to 400 μm; crystallinity, 95%) combined with different concentrations of recombinant human platelet-derived growth factor BB (rhPDGF-BB), human recombinant basic fibroblast growth factor-2 (rhFGF-2), or recombinant human bone morphogenetic protein-2 (rhBMP-2). A custom-made polycarbonate tube was fixed to each defect site by applying slight pressure, and a mixture of bone graft and growth factor was implanted into the tubes. Data were collected 2, 4, and 8 weeks after creation of the defects to assess early and late healing. Various amounts of newly formed bone and remnant BCP particles formed inside of the tube throughout the study period. The BCP + 0.5 mg/mL rhBMP-2 group exhibited the most bone formation. At 8 weeks, more new bone formation was noted in the Osteon III + rhBMP-2 combined group than in other groups. The present study results indicate that BCP can be combined with different concentrations of rhBMP-2, rhFGF-2, and rhPDGF-BB to produce new bone formation within a polycarbonate tube in calvarial defects in a rabbit model.