Quantitative expression of bone-related cytokines induced by mechanical tension-stress during distraction osteogenesis in a rabbit mandible.

Abstract

The aim of the present study was to investigate the temporal and spatial gene expression of bone morphogenetic proteins (BMP)-2, -4, and -7, and transforming growth factor-β (TGF-β), during the distraction process of the rabbit mandible. Twenty rabbits each had an osteotomy on the left mandibular body, and distraction devices were fixed. After a delay of 3days, distraction was started at a rate of 0.5mm/12h for 10days, followed by a 3-week consolidation phase. Four rabbits were killed 5 and 10days of distraction, and 1, 2, and 3weeks after the completion of distraction. The clinical, histological, and radiographic appearances were evaluated and analyzed with the concomitant BMP expression pattern at each interval. After the distraction was started, the fibrous interzone developed between the osteotomy fragments, where intramembranous ossification was noted. The quantitative expression of BMP-2, -4, and -7, and TGF-β, were increased immediately after active distraction before a gradual decline to normal levels after the third week of consolidation. These results suggest that BMP and TGF-β play an important role in the induction of bone formation during distraction osteogenesis. The selective expression of each bone-related cytokine could provide useful insight into accelerated bone maturation and the treatment of poorly-healing fractures in clinical cases.