糖尿病大鼠脊髓损伤后血小板衍化生长因子的表达研究

目的观察糖尿病大鼠脊髓机械性损伤后损伤处脊髓血小板衍化生长因-7-（PDGF）在星型胶质细胞中的表达量，以探讨脊髓损伤过程中PDGF的作用。方法将36只大鼠随机分为假手术对照组、脊髓损伤组和糖尿病脊髓损伤组并制作相关模型，观察脊髓损伤24h和7d后大鼠运动功能的改变、损伤脊髓的病理变化及PDGF在星型胶质细胞中的表达情况。采用UTHSCSA Image Tools 3．0图像分析处理系统进行分析，统计各张切片单位面积（mm^2）内PDGF阳性细胞的数量和光密度：BIO-RAD软件Quantityone测定并用相对灰度值表示PDGF蛋白的表达量：然后对所得数据进行分析。结果脊髓损伤24h后，两组大鼠均出现严重运动功能障碍，BBB功能评分分别为（0.7±0．4）、（0．7±0.5）分：损伤7d后，脊髓损伤组大鼠恢复为（6．7±1.2）分，而糖尿病脊髓损伤组仅恢复为（3．9±0.7）分，两组差异有统计学意义（P〈0．01）：而假手术对照组大鼠运动自如，术后24h和7d评分均为（21．0±0．0）分，与另两组比较差异均有统计学意义（均P〈0．01）。术后24h脊髓损伤组和糖尿病脊髓损伤组脊髓损伤部位白质中可见肿胀的轴突和大量空泡。灰质中存在极少量的神经元和胶质细胞;7d后损伤范围确定，损伤段变细，脊髓内有空洞形成，其中糖尿病脊髓损伤组的空洞大于脊髓损伤组，并且周围有炎性细胞浸润。PDGF阳性表达部位为星形胶质细胞，术后24h、7d假手术对照组PDGF表达少，没有太大的变化：24h后脊髓损伤组和糖尿病脊髓损伤组损伤部位的PDGF表达增多，且脊髓损伤组明显多于糖尿病脊髓损伤组（P〈0．01）：7d后脊髓损伤组PDGF持续高表达，仍明显多于糖尿病脊髓损伤组（P〈0．01）。在Western blot检测中，假手术对照组在两个时段均仅有少量PDGF蛋白表达，24h后脊髓损伤组PDGF表达明显多于糖尿病脊髓损伤组（P〈0．01），损伤7d后脊髓损伤组PDGF持续高表达，仍明显高于糖尿病脊髓损伤组（P〈0．01）。结论糖尿病脊髓损伤大鼠脊髓损伤后BBB评分明显低于脊髓损伤组大鼠，PDGF表达量亦明显减少，可能与高血糖状态加重脊髓的损伤以及抑制其损伤后恢复有关。

Expression of platelet derived growth factor after acute spinal cord injury in diabetic rats

Objective To investigate the expression of platelet-derived growth factor （PDGF） in astrocytes after acute contusive spinal cord injury （SCI） in diabetic rats. Methods Twenty four hours and 7 days after SCI, the motor function of rats was evaluated by BBB score, pathological changes of spinal cord was observed by light microscopy, PDGF expression in astrocytes was examined by immunohistochemistry and Western Blot. The number and optical density of the PDGF-positive cells were determined by UTHSCSA Image Tools 3.0. The expression levels of PDGF were measured by BIO-RAD software Quantity. Results The rats of SCI suffered from paraplegia, severe motor dysfunction 24h after injury. There was no significant difference in BBB function scores between the spinal cord injury group and diabetic spinal cord injury group （P 〈0.01）. The rats in spinal cord injury group restored 7-8 points, whereas diabetic spinal cord injury group were slowly recovered, BBB function score was ranged from 3-4 point （P 〈0.01）, sham surgical control group moved freely without any dysfunction, postoperative 24h and 7d score were 21 points （P 〈0.01）. The structure of neurons and astrocytes was clear and integrity in the normal rats＇ gray matter. After 24h injury, many swollen axons and a large number of vacuoles existed in the white matter of spinal cord injury group and diabetic spinal cord injury group, and there was also very small amount of neurons and astrocytes presenting in the gray matter. The scope of injury had been determined and the cavity had formatted in the spinal cord by 7d post-injury, which was in diabetic spinal cord group bigger than in spinal cord group, and the region of injury was surrounded by inflammatory. PDGF expressed little in normal group＇astrocytes after operation. The expression of PDGF was increased in spinal cord injury group and diabetic spinal cord injury group at 24h after SCI, but compared with diabetic spinal cord injury group, the expression level of PDGF was higher（P 〈0.01）.After 7d, PDGF was sustained expressing in spinal cord injury group, and there was significantly difference compared diabetic spinal cord injury group （P 〈0.01）. To confirm this observation, we also detected PDGF expressing in the three groups. Compared with diabetic spinal cord injury group, the expression of PDGF was significantly higher in spinal cord injury group at 24h and 7d post-injury, respectively（P 〈0.01）. These results were consistent with the result of immunohistochemistry. Conclusion 1. BBB score was significantly lower in diabetic spinal cord injury group than that of spinal cord injury group in rats at 7d post-injury.2. The expression of PDGF was also significantly reduced in diabetic spinal cord injury group compared with spinal cord injury group, it may be related to inhibit of resumption of SCI at the hyperglycaemia condition.