Radiation-induced impairment of bone healing can be overcome by recombinant human bone morphogenetic protein-2

Radiotherapy of head and neck tumors very often results in impaired healing of craniomaxillofacial bones in the vicinity. Management of radionecrosis of bones after radiotherapy is an important clinical challenge. Bone morphogenetic proteins (BMPs) induce new bone differentiation. The aim of this study is to investigate the potential of BMPs in ameliorating radiation-induced impaired bone repair. Two 3-mm diameter defects were created in the calvaria of rats. The defects were treated with different doses of recombinant human (rh) BMP-2 using collagen type I as a carrier. Irradiation with a single dose of 1200 rad was performed 2 or 7 days preoperatively. Unirradiated animals served as controls. New bone formation was assessed by quantitation of radiographs of the calvaria and histology on day 21 after surgery. Untreated, unirradiated defects showed a spontaneous osseous regeneration of 90 ± 7% of the defect area within 21 days. Irradiation of the site (1200 rad 2 days preoperatively) resulted in a profound decrease in the bone fill of the untreated defect (5 ± 2%). Recombinant human BMP-2 in soluble collagen type I carrier delivered to the defect resulted in a significant increase of new bone formation (34 ± 14%, P < 0.01 for 25 μg rhBMP-2; 77 ± 19% for 35 μg rhBMP-2, P < 0.01). Type I collagen carrier alone resulted in only 7 ± 2% healing. In conclusion, radiation-induced impairment of calvarial repair can be overcome by rhBMP-2. Thus, the concept of BMP-2-induced regeneration has potential applications in reconstructive craniomaxillofacial surgery after irradiation.