Bone regeneration in defects compromised by radiotherapy

Because bone reconstruction in irradiated sites is less than ideal, we applied a regenerative gene therapy method in which a cell-signaling virus was localized to biomaterial scaffolds to regenerate wounds compromised by radiation therapy. Critical-sized defects were created in rat calvariae previously treated with radiation. Gelatin scaffolds containing lyophilized adenovirus encoding BMP-2 (AdBMP-2) or freely suspended AdBMP-2 were transplanted. Lyophilized AdBMP-2 significantly improved bone quality and quantity over free AdBMP-2. Bone mineral density was reduced after radiotherapy. Histological analyses demonstrated that radiation damage led to less bone regeneration. The woven bone and immature marrow formed in the radiated defects indicated that irradiation retarded normal bone development. Finally, we stored the scaffolds with lyophilized AdBMP-2 at -80°C to determine adenovirus stability. Micro-CT quantification demonstrated no significant differences between bone regeneration treated with lyophilized AdBMP-2 before and after storage, suggesting that virus-loaded scaffolds may be convenient for application as pre-made constructs.