Assessment of angiogenesis and osteogenesis in continuous distraction osteogenesis

Abstract

BACKGROUND AND OBJECTIVES: To evaluate the effect of distraction frequency on angiogenesis and osteogenesis using a rabbit model of mandibular lengthening. METHODS: 80 adult New Zealand white rabbits were randomly assigned to the continuous distraction group and intermittent distraction group. Unilaterally straight osteotomy was performed on all the animals. The custom-designed manual-driven or auto-driven distractor was adapted on the mandible. For the intermittent distraction group, distraction was performed once per day; in the continuous distraction group, distraction was achieved at a high frequency of 8 steps per second. 10 rabbits in each group were sacrificed at day 3, day 7, day 11 (end of active distraction) and day 18 (week 1 of consolidation) respectively. Bone healing were assessed by histological examination; angiogenesis was evaluated by the immunohistochemical staining of collagen IV; mRNA expression of vascular epithelial growth factor, basic fibroblast growth factor, bone morphogenetic growth factors, transforming growth factor-beta were examined by real time polymerase chain reaction (PCR). RESULTS: All rabbits completed the experimental process uneventfully. Real time PCR examination demonstrated a significant upregulation of all the angiogenic and osteogenic growth factors in the continuous distraction group. Neo-vessel density and bone formation in distraction regenerate was significantly increased by the high frequency traction. CONCLUSION: High frequency mechanical traction creates a superior biological environment for bone regeneration by upregulating angiogenic and osteogenic factors.