Guo Qi, Zhang Liu
Department of Orthopedics, North China Coal Medical College, Affiliated Hospital, Tangshan Hebei 063000, PR China.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2007 Oct;21(10):1040-4.
To investigate the changes in the expression level of bone morphogenetic protein 2 (BMP-2) in the bone callus of rats with femoral fracture and brain injury to explore the effect of the brain injury on the fracture healing and to explore the related mechanism.
Thirty-two 12-week-old SD rats weighing 368 +/- 25 g were randomly divided into 4 groups of 8 rats in each. The rats in Group A had a femoral fracture and a brain injury for 1 week; the rats in Group B had a femoral fracture but without brain injury for 1 week; the rats in Group C had a fracture and a brain injury for 2 weeks; and the rats in Group D had a fracture but without brain injury for 2 weeks. Thus, Groups A and C were used as the femoral fracture and brain injury models, and Groups B and D as the pure femoral fracture models for the controlled study. After the X-ray films were taken, the bone callus was obtained 1 week and 2 weeks after operation, respectively. Then, the bone callus growth and its histology were examined with the HE staining, the expression and changes in the level of BMP-2 were examined with the immunohistochemical staining, and the level of BMP-2 mRNA was measured with the RT-PCR.
The X-ray films showed that less bone callus formation was found in Group A, and the fracture line in Group B was clearer than that in Group A. There was a greater amount of callus in Group C, and the fracture line was blurred. Only a little bone callus formation was found in Group D. The HE staining indicated that more fibroblasts and early-stage chondrocytes were found in Group A; some fibroblasts in the fracture interspace and fewer early-stage chondrocytes in Group B; some newly-formed trabecular bone at the end of the fracture in Group C; but no trabecular bone formation in Group D. The immunohistochemical staining indicated that the positive expression of BMP-2 was strong in the cytoplasms of the fibroblasts, the mesenchymal cells, the vascular endothelial cells, the early-stage chondrocytes, and the osteoblasts. The number of the positive cells was greater in Group A than in Group B, with a higher color intensity. The number of the positive cells was greater in Group C than in Group D, with a higher color intensity. The percentages of the cells positive for BMP-2 in the callus were greater in Groups A and C (0.762% +/- 0.052%, 0.756% +/- 0.079%) than in Groups B and D (0.702% +/- 0.052%, 0.672% +/- 0.044%) at the same time point, with a statistically significant difference (P < 0.05). The RT-PCR analysis showed that the expression of BMP-2 mRNA in the callus in Groups A-D was decreased in sequence. There was a significantly higher level of the expression in Groups A and C (1.07 +/- 0.13, 0.78 +/- 0.11) than in Groups B and D (0.91 +/- 0.12, 0.61 +/- 0.08) at the same time point (P < 0.05).
The brain injury can promote the fracture healing process, which is probably related to an increase in the expression level of BMP-2 after the brain injury.
研究股骨骨折合并脑损伤大鼠骨痂中骨形态发生蛋白2（BMP-2）表达水平的变化，探讨脑损伤对骨折愈合的影响及其相关机制。
将32只12周龄、体重368±25 g的SD大鼠随机分为4组，每组8只。A组大鼠股骨骨折合并脑损伤1周；B组大鼠单纯股骨骨折，无脑损伤，为期1周；C组大鼠股骨骨折合并脑损伤2周；D组大鼠单纯股骨骨折，无脑损伤，为期2周。因此，将A组和C组作为股骨骨折合并脑损伤模型，B组和D组作为单纯股骨骨折模型进行对照研究。拍摄X线片后，分别于术后1周和2周获取骨痂。然后，通过HE染色观察骨痂生长及组织学情况，采用免疫组织化学染色检测BMP-2表达水平及变化，运用RT-PCR检测BMP-2 mRNA水平。
X线片显示，A组骨痂形成较少，B组骨折线比A组清晰。C组骨痂量较多，骨折线模糊。D组仅有少量骨痂形成。HE染色表明，A组有成纤维细胞和早期软骨细胞较多；B组骨折间隙有一些成纤维细胞，早期软骨细胞较少；C组骨折端有一些新形成的小梁骨；D组无小梁骨形成。免疫组织化学染色显示，BMP-2在成纤维细胞、间充质细胞、血管内皮细胞、早期软骨细胞和成骨细胞的细胞质中呈强阳性表达。A组阳性细胞数量多于B组，着色强度更高。C组阳性细胞数量多于D组，着色强度更高。同一时间点，A组和C组骨痂中BMP-2阳性细胞百分比（0.762%±0.052%，0.756%±0.079%）高于B组和D组（0.702%±0.052%，0.672%±0.044%），差异有统计学意义（P<0.05）。RT-PCR分析显示，A~D组骨痂中BMP-2 mRNA表达依次降低。同一时间点，A组和C组表达水平（1.07±0.13，0.78±0.11）显著高于B组和D组（0.91±0.12，0.61±0.08）（P<0.05）。
脑损伤可促进骨折愈合过程，这可能与脑损伤后BMP-2表达水平升高有关。
