不同程度创伤性脑损伤大鼠降钙素基因相关肽表达变化及其意义

Expression of calcitonin gene-related peptide in rats with different degrees of traumatic brain injury and its significances

目的建立液压创伤性脑损伤(TBI)模型,探讨创伤性脑损伤大鼠降钙素基因相关肽(CGRP)表达变化及其意义。方法健康雄性Wistar大鼠168只,体质量250～300g,随机分为损伤轻度、中度、重度及对照组各42只。各组分别再随机分为0.5、2、6、12、24、48、72h各7个亚组每组6只。采用液压颅脑损伤仪,对轻度、中度、重度组分别给予0.5～1.0atm(1atm=101.3kPa)、1.5～2.0atm、2.5～3.0atm液压冲击力,制成轻、中、重3型液压颅脑损伤模型。分别于致伤后相应时间点对各组大鼠断头取脑。采用苏木素-伊红(HE)染色观察TBI中组织病理改变,免疫组织化学检测创伤区大脑皮层CGRP表达。结果①光镜观察显示:创伤后12～48h时脑组织损伤最严重。②不同程度TBI中创伤区大脑皮层CGRP神经元表达的阳性单位呈现规律性变化,损伤程度越重,CGRP表达的阳性单位变化幅度越大。不同程度TBI组及对照组之间创伤区大脑皮层中CGRP神经元表达的阳性单位不同,差异有统计学意义;重度组明显低于轻度、中度及对照组,差异有统计学意义;轻度、中度及对照组之间,差异无统计学意义。TBI中损伤程度和时间对于创伤区大脑皮层中CGRP神经元表达的阳性单位有交互效应,中度2h时最高,重度24h时最低。结论不同程度TBI中创伤区大脑皮层CGRP神经元表达的阳性单位量与损伤程度及损伤后时间有关。

Objective To investigate the expression of calcitonin gene-related peptide （CGRP） in rat models with different degrees of traumatic brain injury （TBI） caused by fluid-percussion. Methods One hunred sixty-eight healthy male Wistar rats （250-300 g in weight） were randomized into the injury （n=126） and control groups （n=42）. The injury group was further divided randomly into 3 secondary groups based on severity of injury （mild, moderate and severe, n=42 each）. These injury-graded groups and control group were again stratified into 7 sub-groups according to time from TBI （0.5, 2, 6, 12, 24, 48 and 72h）, such that every sub-group had 6 rats. To create TBI models, the rats assigned to injury group received different powers of fluid percussion （0.5-1.0 arm, 1,5-2.0 arm or 2.5-3.0 arm depending on pre-specified severity of injury） delivered by a hydraulic brain hammer. Immediately after the injury and at specific time spots, brain tissues of every rat were collected according to corresponding observation time after trauma, and studied for TBI-related pathology with HE staining. The expression of CGRP in the injured cortex was detected by immunohistochemistry. Results ①Light microscope showed that the TBI was most severe at 12-24 hours; ②In cortex with traumatic brain injury, CGRP-expressing neurons as measured in masc units changed regularly to different degrees of injury, with greater change linked to severer injury. There was a significant difference in total masc units of CGRP-expressing neurons of the injured cortex between injury groups and the control group （P〈0.01）, which appeared significantly lower in the severe injury group （P〈0.01） but comparable across the other three groups （mild, moderate, control）. Severity-time interaction was shown to have an effect on the masc unit of CGRP-expressing neurons of the injured cortex. The peak and trough masc units were recorded in 2 h-moderate and 24 h-severe sub-groups, respectively. Conclusion In traumatic brain injury, masc unit of CGRP-expressing neurons may change regularly to the degree of injury and post-traumatic time.