Effects of hyperbaric oxygen on the expression of osteoprotegerin and integrin β1 in rabbit＇s mandibular distraction gap

Objective To investigate the effect of hyperbaric-oxygen therapy on osteoprotegerin (OPG) and integrin β1 (Itgβ1) expression during mandibular distraction osteogenesis. Methods Forty New-Zealand rabbits were used. The animals were randomly divided into two groups (experimental group and control group) with 20 animals each; after accomplished osteotomy and implant distraction devices on mandible bilaterally for 3 days of latency period, the device was activated at the rate of 0.8 mm per day for 10 days. All animals in the experimental group were subjected to hyperbaric oxygen for 90 minutes once a day since the beginning of distraction, and lasted for four weeks. In control group, all the distractors were activated following the same distraction protocol as the experimental group, but without hyperbaric oxygen therapy. Five animals of each group were sacrificed at 10th day after distraction, 7th, 14th and 28th day of consolidation, respectively. The lengthened mandibles were harvested and processed for immunohistochemical examinations to detect OPG and Itgβ1 expression in the distraction gap. Semi-quantitative analysis was carried out by image analysis software. Results OPG staining was mainly located in the membrane and cytoplasm of osteoprogenitor cells and osteoblasts in the distraction zones. The expression of OPG increased after distraction accomplished and reached to the peak at 7th day of consolidation, and then decreased gradually. At every time point, the level of expression of OPG in the experimental group was remarkably higher than those in control group. There were significant differences between the experimental group and control group (P 0.05). Conclusions Hyperbaric oxygen therapy can up-regulate the expression of OPG and Itgβ1 in the distraction gap, which may promote osteoblast differentiation, proliferation, enhance osteoblast function, and new bone formation in distraction gap. Key words: Rabbits; Traction; Mandible; Integrin beta1; Osteoprotegerin; Hyperbaric-oxygen