Intramuscular osteoinduction and bone marrow formation by the implantation of rhBMP-2 with atelopeptide type I collagen.

The study examines the osteoinductive potential of recombinant human morphogenetic protein 2 (rhBMP-2) radiologically and histologically in rat calf muscle. Ten male Wistar rats were used. rhBMP-2 50 microg was implanted with atelopeptide type I collagen as carrier in a pouch in rat calf muscle (n = 5), and atelopeptide type I collagen alone was implanted in a further five as control. Induction of osteogenesis at 4 weeks was investigated. In all rats in which rhBMP-2 had been implanted there was a radio-opaque shadow in the muscle in the soft tissue radiograph. No such shadows were noted in the control group. Histological examination showed bony trabeculum, osteoblasts, and vigorous bone marrow including fatty marrow and angioid tissue both at the margins and in the center of the excised lumps in the rhBMP-2 group. There were no such signs in the control group. rhBMP-2 may be capable not only of inducing the formation of bone, but also of inducing a 'self-supporting bone organ' in the muscle.