Bone inductive properties of rhBMP-2 loaded porous calcium phosphate cement implants inserted at an ectopic site in rabbits

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is known for its osteoinductive potential in bone tissue engineering. Calcium phosphate (Ca-P) cements are injectable, osteoconductive ceramic materials in which a macroporous structure can be induced during the setting reaction. In this study, the osteoinductive capability of rhBMP-2 loaded porous Ca-P cement was evaluated. Porous Ca-P cement discs were made and loaded with rhBMP-2 in vitro and implanted subcutaneously in the back of New Zealand white rabbits. The implantation period was either 2 or 10 weeks. Histological analysis of retrieved specimens revealed evident bone formation in the rhBMP-2 loaded Ca-P cement discs (pore fill: 18±6%) after 10 weeks of implantation. Bone formation occurred only in rhBMP-2 loaded porous Ca-P cement discs. Degradation of the Ca-P cement could not be confirmed after 10 weeks of implantation. The scaffold maintained its shape and stability during this time period. We conclude that porous Ca-P cement is a suitable carrier material for ectopic bone engineering.