兔脑缺血再灌注磁共振弥散加权成像与水通道蛋白-4表达的相关性

Correlation between MR-DWI and the expression of aquaporin-4 after acute cerebral ischemia and reperfusion in rabbits

目的分析兔脑急性缺血组织磁共振弥散成像(DWI)的影像学表现及其与水通道蛋白-4(AQP-4)表达的关系,探讨DWI成像的病理生理基础。方法 58只新西兰大白兔随机分为永久缺血组(A组)和再灌注组(B组),线栓法制作大脑中动脉缺血和缺血1h后再灌注模型。其中A组(A1～A6)分为缺血1h、3h、6h、12h、24h、48h组;B组(B1～B6)又分为再灌注0h、2h、5h、11h、23h和47h组。每组分别于各自时间点进行MRI弥散成像,分别测量表观弥散系数(ADC),并计算相对表观弥散系数(rADC)值。显微镜下观察并记录双侧大脑皮层和纹状体区AQP-4阳性细胞数。结果缺血1h时DWI高信号区内平均ADC值95%可信区间上限为58.75×10-5mm2/s。缺血组DWI高信号区面积随时间延长逐渐增大,rADC值呈先下降后上升的趋势。再灌注组rADC值于再灌注2h趋于正常化,DWI高信号区面积减小;5h rADC值最低;以后rADC值逐渐升高,DWI高信号区面积逐渐扩大。缺血组AQP-4阳性细胞数6h内呈下降趋势,6h后缓慢上升,与rADC值的变化关系密切(r=0.943,P=0.005);再灌注5h内AQP-4变化平稳,之后也出现上升趋势。结论 AQP-4表达水平的高低受缺血程度和持续时间的影响,永久缺血组rADC值的变化趋势与AQP-4表达水平的高低有明显的相关性。

Objective To disclose the relationship between aquaporin-4（AQP-4）and apparent diffuse coefficient （ADC） by analyzing the magnetic resonance diffusion weighted imaging （MRI-DWI） of acute cerebral ischemia and reperfusion in rabbits. Methods Fifty-eight New Zealand white rabbits were divided into permanent ischemia group （A group, n = 30）which were subdivided into 1 hour, 3 hours, 6 hours, 12 hours, 24 hours, 48 hours groups, and reperfusion group after 1 hour cerebral ischemia （ B group, n = 28） which were subdivided into 0 hour, 2 hours, 5 hours, 11 hours, 23 hours, 47 hours groups. All rabbit brains were cut out to make histologic section immediately after each time point MRI examination. AQP-4 detection was carried out in bilateral cortical and corpus striatum region respectively under microscope. ADC and rADC value and positive cells of AQP-4 were calculated and recorded.. Results The hyperintensity area in MRI-DWI tended to enlarge gradually in permanent ischemia groups. The relative apparent diffusion coefficient （rADC） value decreased at first and then increased gradually. In repel＇fusion groups, the rADC value increased at the 2nd hour point with shrinkage of hyperintensity area on DWI. After 5 hours of reperfusion, the rADC value increased again with enlargement of DWI hyperintensity area. AQP-4 positive cells decreased within 6 hours, and then went up in permanent ischemia groups. There was a close relationship between rADC value and AQP--4 positive cells（r = 0. 943, P = 0. 005）. The same things happened in reperfusion groups within 5 hours, but the scope of change was smaller. Conclusion In permanent ischemia groups, there is a close relationship between rADC value and the expression of AQP-4.