大鼠股骨骨折合并脑外伤时早期骨愈合过程中PDGF的表达

目的探讨大鼠股骨干骨折合并脑外伤时骨痂组织内血小板衍生生长因子（platelet-derived growth factor,PDGF）表达水平的变化和脑外伤对骨折愈合的影响及作用机制。方法取12周雄性SD大鼠32只,随机分为4组,每组8只：A组为骨折合并脑外伤1周组,A1组为单纯骨折1周组,B组为骨折合并脑外伤2周组,B1组为单纯骨折2周组。A、B组制作脑外伤和股骨干骨折模型,A1、B1组制作单纯股骨干骨折模型。4组摄X线片后截取骨痂,HE染色观察骨痂生长情况及组织形态,免疫组化染色测定PDGF表达,原位杂交检测PDGFmRNA表达。结果X线片示同一时间点骨折合并脑外伤组较单纯骨折组骨折端骨痂形成早、骨痂大、骨折愈合加快。免疫组织化学染色可见成纤维细胞、间充质细胞、血管内皮细胞、早期软骨细胞、成骨细胞、破骨细胞胞浆在不同时间点分别出现广泛的强阳性反应。A、B组平均阳性细胞百分数分别高于同一时间点A1、B1组（P〈0.05）。原位杂交分析显示：成纤维细胞、间充质细胞、血管内皮细胞、早期软骨细胞、成骨细胞、破骨细胞胞浆在不同时间点分别出现广泛的PDGFmRNA表达,骨痂PDGFmRNA阳性细胞百分数,A、B组骨痂PDGFmRNA阳性细胞百分数均显著高于同一时间点A1、B1组（P〈0.05）。结论脑外伤对骨折愈合有促进作用,可能与脑外伤后PDGF表达水平升高有关。

Expression of PDGF in early fracture healing process in rats with femoral fracture after brain injury

Objective To investigate the changes of the expression levels of platelet-derived growth factor（PDGF） in the bone callus of rats with femoral fracture and brain injury in order to explore the effect of the brain injury on the fracture healing and to explore the related mechanism.Methods Thirty-two SD rats（age：12 weeks） were randomly divided into 4 groups,8 rats in each group.The rats in group A and group B had a femoral fracture and a brain injury for 1,2 weeks respectively,and the rats in group A1,B1 had a fracture,without brain injury for 1,2 weeks respectively.Thus,the rats in group A and group B were the femoral fracture and brain injury models,while the rats in groups A1 and group B1 were the pure femoral fracture models as control.After the X-ray films were taken,the bone callus was obtained 1,2 weeks after operation respectively.Then,the bone callus and its histological changes were examined by HE staining,the expression and changes in the levels of PDGF were detected by immunohistochemical staining,and the levels of PDGF mRNA were measured by in situ hybridization.Results The X-ray films showed that the callus formation in the femoral fracture and brain injury groups were earlier and greater than that in the pure femoral fracture groups at the same time point.The immunohistochemical staining indicated that the positive expression of PDGF was strong in the cytoplasms of the fibroblasts,the mesenchymal cells,the vascular endothelial cells,the early-stage chondrocytes,osteoblasts and osteoclasts.The percentages of the positive cells of PDGF in the callus were significantly higher in groups A,B than those in group A1,B1 at the same time point（P 0.05）.The in situ hybridization analysis showed that the positive expression of PDGFmRNA in the cyt-oplasms of the fibroblasts,the mesenchymal cells,the vascular endothelial cells,the early-stage chondrocytes,the osteoblasts and the osteoclasts.The percentages of the positive cells for PDGFmRNA in the callus were significantly higher in group A,B than those in group A1,B1 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 levels of PDGF after the brain injury.