Demineralized bone matrix supplied by bone banks for a carrier of recombinant human bone morphogenetic protein (rhBMP-2): a substitute for autogeneic bone grafts

Four commercially available preparations of demineralized freeze-dried human bone powders (DFDB) were investigated for endogenous bone morphogenetic protein (BMP) as observed by osteoinductive activity. Composites of DFDB without and with 1 microgram or 10 micrograms of recombinant human bone morphogenetic protein-2 (rhBMP-2) were implanted into the hindquarter muscles of Swiss-Webster mice. The four batches of DFDB without rhBMP-2 were placed also in hindquarter muscles of athymic mice. Three weeks after implantation, the area of induced bone and cartilage formation was measured by radiographic and histomorphometric methods. In normal mice, without rhBMP-2, DFDB implants induced development of dense fibrous connective tissue with minimal, if any, new bone. In athymic mice, DFDB induced development of small patches of appositional new bone. In contrast, in normal mice, composites of DFDB and rhBMP-2 induced development of large areas of heterotopic bone and bone marrow formation. The bone morphogenetic response occurred with a statistically significant difference (p < 0.0001) between implants of 1 microgram and the 10-microgram rhBMP-2 composites. Thus, DFDB from all four bone banks demonstrated comparable capacity to serve as a carrier for rhBMP-2.