A preliminary report on the effect of dimeric rhGDF-5 and its monomeric form rhGDF-5C465A on bone healing of rat cranial defects

Introduction: The purpose of the study was to compare the efficacy on rat skull defects of two bone growth factors derived from the GDF-5 family. Material and methods: The study was conducted on 17 adult Wistar rats. On each animal, two symmetrical 6-mm wide, full-thickness, skull defects were carried out in the parietal regions. In 15 out of 17 animals, both experimental defects were filled by the implants. In the group I (n = 2), both defects were left empty for control. The 15 other rats were divided into 3 groups: In group 11 (n = 5), a collagen sponge was implanted. In group III (n = 5), a collagen sponge impregnated with rhGDF-5 (the genuine dimeric form) was implanted. In group IV (n = 5), a collagen sponge impregnated with rhGDF-5C465A (a monomeric form of GDF-5) was implanted. All animals were sacridiced at 8 weeks. The harvested specimens were processed for contact radiography and standard histological examination. The quantitative results were assessed with a semi-quantitative histological scoring system. Results: One animal in the group H was excluded because it died of unknown reasons. In group 1, no bone healing was observed in the defects. In group 11, no bone healing was observed in 4 out of 10 defects, and partial bone healing was observed in 5 out of 10 defects. In group 111, partial bone healing was also observed in 3 out of 8 defects and complete bone healing in 4 out of 8 defects. In group IV, partial bone healing was observed in 8 out of 10 defects and complete bone healing in 2 out of 10 defects. Conclusion: Bone healing was improved in all treated groups. Further studies are necessary to determine the optimal formulation of these composite implants. (C) 2008 European Association for Cranio-Maxillofacial Surgery