Comparison of ectopic osteoinduction in vivo by recombinant human BMP-2 and recombinant Xenopus BMP-4/7 heterodimer

Two micrograms recombinant human bone morphogenetic protein-2 (rhBMP-2) and 2 microg recombinant Xenopus bone morphogenetic protein-4/7 heterodimer (rxBMP-4/7ht) were implanted into a calf muscle pouch in rats using atelopeptide type I collagen (CL) solution as the carrier. Three weeks later induced bone in the rhBMP-2 + CL group (group A; n=5) and the rxBMP-4/7ht + CL group (group B; n=5) was investigated radiologically and histologically. Bone trabeculum and marrow were induced in all cases of both groups. In group A the area of radioopaque oval shadows was 5.78 mm2, wider than 4.64 mm2 in group B. The radoopacity in group A was 74.6, higher than 57.6 in group B. Histometry of the microscopic views showed that the trabecular area was 0.92 mm2 in group A and 0.22 mm2 in group B, while the trabecular percentage occupied in the overall lump area was 18.07% in group A and 5.51% in group B. The trabecular form in group A was more massively coral than in group B. This study indicated that rhBMP-2 has a higher ectopic osteoinduction ability in vivo than rxBMP-4/7ht.