| Objective Internal rigid fixation (IRF) with dynamic compression plate (DCP) has been shown to be able to promote jaw fracture healing. To investigate the molecular mechanism, we established rabbit mandibular fracture surgery models and examined the effect of compression internal fixation on the expression of VEGF, TGF-β1 and BMP-2 during the rabbit mandibular fracture healing process.Methods We established the rabbit models of mandibular fractures and did fixation using ordinary micro-plate, that is control group, and dynamic compression plate (DCP), that is experimental group. We killed three rabbits in control group and experimental group at 3d,7d,14d,18d,21 d and 28d after operation, respectively and detected VEGF, TGF-β1 and BMP-2 expression by quantitative real-time RT-PCR in callus tissue; We killed two rabbits in control group and experimental group at 14d and 28d after operation, respectively and observed the situation of fracture healing by visual study and HE staining.Results 1. Rabbit mandibular gross observation:In day 14, bone surface slightly hunched and continued, fracture line were visible in the control group and experimental group. Compared with experimental group, the mandibular body fracture can be seen mobility under external forces. Fracture healed well and had no malposition and no mobility between two body fracture in the control group and experimental group on 28d. In 28d after operation, callus proliferated and covered the fracture line, the fracture place were surrounded by thick fibrous tissue. But no callus proliferated and fibrous tissue surrounded in the experimental group.2. Histological (HE staining) results:14d after the operation, the experimental group emerged a large number of cartilage cells and bone cells,most fibroblast cells were circular, larger osteoblasts, extracellular matrix formation are more closely arranged in trabecular bone; control group, collagen fibers are more cartilage cells and a relatively small number of osteoblasts, bone trabeculae arranged sparsely.28d after the operation, the experimental group shows mature lamellar bone and bone cells, bone cells are more visible outside osteoclasts;Control group, fewer bone cells, osteoblasts more.3. Real-time RT-PCR results3.1 VEGF expression:Amount of VEGF expression were basic propter in the experimental group and control group on 3d after operation (p> 0.05). Amount of VEGF expression in experimental group was 1.56 times than what in the control group (p> 0.05) on 7d, VEGF expression reached the peak in the control group and experimental group and expression amount in experimental group was 1.68 times than what in the control group (p<0.05) on 14d. Amount of VEGF expression which were basic propter in the experimental group and control group decreased after 14d (p> 0.05).3.2 TGF-β1 expression:Amount of TGF-β1 expression was basic quite in the experi-mental group and control group on 3d after operation (p> 0.05). TGF-β1 expression increased in the two groups after 3d and reached peak on 14d. TGF-β1 expression decreased after 14d and was no significant difference between the two groups (p> 0.05) at the first 21d and 28d. Amount of TGF-β1 expression in experimental group was 1.57 times (p<0.05) on 7d and was 1.68 times than that in the control group (p<0.05) on 14d.3.3 BMP-2 expression:Amount of BMP-2 expression in experimental group were slightly higher than that in the control group at 3d (p> 0.05). BMP-2 expression increased in the two groups after 3d and reached peak at 14d. At 14d, expression of BMP-2 in the experimental group was 2.20 times then what in the control group. (p<0.05) BMP-2 expression decreased after 14d and were no significant difference between the two groups at 21d (p> 0.05)and 28d (p> 0.05).Conclusion The IRF with DCP could be an ideal internal fixation to fracture healing. VEGF, TGF-β1 and BMP-2 expression of callus tissue in fracture place increased during early fracture healing may be one of molecular mechanism of promoting fracture healing. |
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