[脑损伤对骨折愈合过程中骨形态发生蛋白2表达的影响]

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.

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

目的

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。

方法

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。

结果

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）。