Bone formation using freeze-dried rhBMP-2 coated macroporous biphasic calcium phosphate blocks in rat calvarial defects

Abstract

The purpose of this study was to evaluate bone formation using macroporous biphasic calcium phosphate block (MBCP block) coated via either freeze-drying or adsorption with recombinant human bone morphogenetic protein-2 (rhBMP-2). Calvarial defects (8mm in diameter) were treated with the following experimental conditions: MBCP block (0.13 g) alone (control), MBCP block coated with rhBMP-2 via adsorption (0.1 mg/ml), and MBCP block coated with rhBMP-2 via a freeze-drying procedure (0.1 mg/ml). The healing period was either 2 or 8 weeks. After a 2-week healing period, the new bone formation differed significantly between those treated with an MBCP block with a freeze-dried coating of rhBMP-2 and the control group. With further healing (i.e., 8 weeks), the distribution of newly formed bone increased in both the freeze-dried coating group and the adsorption group. The new bone area and bone density of all groups differed significantly between the 2- and 8- week healing period.The findings of the present study suggest that freeze-drying is a reliable method of incorporating rhBMP-2 onto MBCP blocks, for use in stable bone formation.