BONE INDUCTIVE POTENTIAL AND DOSE-DEPENDENT RESPONSE OF BOVINE BONE MORPHOGENETIC PROTEIN COMBINED WITH TYPE-IV COLLAGEN CARRIER

Using type IV collagen as carrier, the expression of bovine bone morph ogenetic protein (bBMP) activity and the relation of ectopic bone form ation to BMP dosage in the reconstitution were investigated in BALB mi ce. Visible heterotopic bone was induced by GuHCl-extracted bovine BMP at a minimal dose of 0.5 mg within 21 days after the BMP was covalent ly bound to type IV collagen of weight 5.6 mg. The dose-dependent oste ogenetic response of BMP was retained in the BMP/type IV collagen comp osite. As the BMP dose increased in the reconstitution, the integrated intensity and area of bone and cartilage formation, as quantified by a computerized scanner, were enhanced. Degradation of the collagenous carrier was improved by BMP, and neovascularization of the implant sit e initiated by type IV collagen was also observed. The covalent bindin g of BMP to type IV collagen postponed the time-sequence of ectopic bo ne development induced by BMP alone. The conclusion was that the exagg erated and extended effects of type IV collagen on BMP are mainly due to chemotaxis to progenitor cells, immunogenetically inert, vascular i nitiation and biodegradability in type IV collagen.