合并脑外伤的骨折愈合过程中PDGF的作用

EFFECT OF BRAIN INJURY ON EXPRESSION OF PDGF IN FRACTURE HEALING PROCESS IN RATS

目的通过研究大鼠股骨干骨折合并脑外伤时骨痂组织内PDGF表达水平的变化,探讨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64只,体重(356±25)g,随机分成8组,每组8只。A1、B1、C1、D1组分别为骨折合并脑外伤1、2、3、4周组,制作脑外伤和股骨干骨折模型;A2、B2、C2、D2组分别为单纯骨折1、2、3、4周组,制作单纯股骨干骨折模型作对照。各组摄CR片后截取骨痂,行HE染色观察骨痂生长情况及其组织形态,免疫组织化学染色测定PDGF表达,原位杂交检测PDGFmRNA表达。结果CR片示在同一时间点A1、B1、C1、D1组较A2、B2、C2、D2组骨折端骨痂形成早,骨痂多,骨折愈合快。HE染色示A1组可见较多早期软骨细胞、成纤维细胞,A2组骨折间隙可见成纤维细胞,仅夹杂有少量的早期软骨细胞;B1组骨折端有新生骨小梁长入,B2组未见骨小梁形成;C1组骨折端有大量编织骨形成且骨小梁间有少量成熟软骨细胞,C2组少量骨小梁向骨折端长入;D1组编织骨向板层骨转化,D2组骨折端为不成熟骨小梁。免疫组织化学染色和原位杂交实验均可见成纤维细胞、间充质细胞、血管内皮细胞、早期软骨细胞、成骨细胞、破骨细胞胞浆出现广泛的强阳性反应,A1、B1、C1、D1组PDGF和PDGFmRNA阳性细胞百分数均高于同一时间点A2、B2、C2、D2组,差异有统计学意义(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。

Objective To investigate the changes in the expression level of PDGF in the bone callus of rats with femoral fracture and brain injury to explore the effect of brain injury on the fracture healing and the related mechanism. Methods Sixty-four 12-week-old SD rats weighing （356 ± 25） g were randomly divided into 8 groups with 8 rats in each. The rats in groups A1, B1, C1 and D1 had a femoral fracture and a brain injury for 1, 2, 3 and 4 weeks, respectively; the rats in groups A2, B2, C2 and D2 had a mere fracture without a brain injury for 1, 2, 3 and 4 weeks, respectively. After the CR films were taken, the bone callus was obtained 1, 2, 3 and 4 weeks after operation, respectively. Then, the bone callus and its histology were examined by HE staining, the expressions and changes in the level of PDGF were examined by the immunohistochemical staining, and the level of PDGF mRNA was measured by in situ hybridization. Results The CR films showed that the callus formation in the A1-D1 groups was earlier and greater than that in the A2-D2 groups at the same time point. The HE staining indicated that more fibroblasts and early-stage chondrocytes were found in group A1; some fibroblasts in the fracture interspace and few early-stage chondrocytes were found in group A2; some newly-formed trabecular bones were found at the end of the fracture in group B1; but no trabecular bone formation was found in group B2; woven bone formation and a few chondrocytes between trabecular bones in the fracture interspace were found in group C1; only a few trabecular bones in the fracture interspace were found in group C2; woven bones turned to lamellar bones in group DI： and more immature trabecular bones in the fracture interspace were found in group D2. The positive expression of PDGF and PDGF mRNA was strong in the cytoplasms of fibroblasts, mesenchymal cells, vascular endothelial cells, early-stage chondrocytes, osteoblasts and osteoclasts. The percentage of the positive cells for PDGF and PDGF mRNA in the callus was significantly higher in groups A1-D1 than in groups A2-D2 at the same time point （P 〈 0.05）. Conclusion Brain injury can promote the fracture healing process, which is probably related to an increase in the expression level of PDGF after the brain injury.