rh-BMP2-induced ectopic bone for grafting critical size defects: a preliminary histological evaluation in rat calvariae

The aim of this study was to evaluate histologically the biological usefulness of recombinant human BMP2 (rh-BMP2)-induced ectopically-formed bone as graft material to repair a bone defect model, compared with autogenous bone and frozen allogeneic bone. Forty-five male Wistar rats were used, which were divided into three graft groups. Each of the three graft groups was divided into three observation period groups (3, 6 and 9 weeks after graft). All rats underwent craniotomy to create a bone defect, and then received a bone graft. In the rh-BMP2-induced ectopic bone graft group, marked bone formation was seen from 3 weeks after graft. In the autogenous bone graft group, marked bone formation was seen from 6 weeks after graft. In the group that received a frozen allogeneic bone graft, marked bone formation was seen from 9 weeks after graft. At 3.6 and 9 weeks after graft, newly formed bone area was significantly greater in the tissue engineered bone (TEB) group than in the auto or frozen allogeneic bone (FAB) group. rh-BMP2-induced ectopically-formed bone graft exhibited better osteoconductivity than autogenous bone graft and frozen allogeneic bone graft. These histological findings indicate that rh-BMP2-induced ectopically-formed bone is suitable as bone graft material.