An experimental study for the detection of autocrine growth activity in the osteogenic cells after mandibular distraction osteogenesis

ABSTRACT

BACKGROUND: Distraction osteogenesis (DO) is a useful method for treating cases demanding the generation of new bone. During DO, the angiogenic activity is crucial factor in the new bone formation. The aim of this study was to detect the autocrine growth activity in the cellular components of the distracted bone with observation of the co-expression of vascular endothelial growth factor (VEGF) and its receptors following the mandibular DO. MATERIALS AND METHODS: Unilateral mandibular distraction (0.5 mm twice per day for 10 days) was performed in six mongrel dogs. Two animals were killed at 7, 14, and 28 days after completion of distraction, respectively. Immediately after the animals were killed, the right mandibles were harvested en block. Immunohistochemical staining was processed for observation of the VEGF expression, and double immunofluorescent staining was also processed for detection of the co-expression of osteocalcin and VEGF's two distinct receptors (VEGFR-1 and VEGFR-2). RESULTS: At 7 and 14 days after distraction, the expressions of VEGF were significantly increased in the osteogenic cells of the distracted bone. Up to 28 days after distraction, VEGF was still expressed moderate in the osteoblastic cells of distracted bone. The co-expressions of osteocalcin / VEGFR-1 and osteocalcin / VEGFR-2 were observed in the distracted bone at 7 and 14 days after distraction. In the double immunofluorescent staining, the co-expression's level of osteocalcin / VEGFR-1 was more than that of osteocalcin / VEGFR-2. Conclusion: Taken together, this study suggested that VEGF plays an important role in the osteogenesis, and these osteoblastic cell-derived VEGF might act as autocrine growth factor during distraction osteogenesis. In the other word, the cellular components, such as osteoblasts and immature fibroblast-like cellsor mesenchymal cells in the distracted bone, might have autocrine growth activity during distraction osteogenesis.