烫伤早期脑水肿家兔脑组织水通道蛋白4表达与磁共振成像结果相关性研究

Correlation analysis between the expression of aquaporin 4 and magnetic resonance imaging of brain tissue in severely scalded rabbit with brain edema during early stage

目的观察水通道蛋白4（AQP4）在严重烫伤早期合并脑水肿家兔脑组织中的表达规律以故与磁共振成像（MRI）信号变化的联系，探讨严重烫伤早期脑水肿水的跨膜转运特征、方法将35只健康新西兰大白兔按照随机数字表法分为正常对照组（5只）及烫伤组（30只），其中烫伤组家兔均造成50％TBSAⅢ度烫伤（经病理切片证实存在脑水肿）。伤后1、2、3、4、5、6h，烫伤组家兔（每时相点5只）行MRI颅脑检查并动态检测表观弥散系数（ADC）值；烫伤组家兔取额叶、颞叶及顶叶皮质．基底节区及小脑组织，采用兔疫组织化学法及RT-PCR分别检测AQP4篮门和AQP4 mRNA的表达。正常对照组家兔同上进行检测，对数据进行单因素方差分析，时AQP4蛋白与ADC值进行一元线性相关分析和Pearson线性相关分析。结果与正常对照组比较，伤后6h内烫伤组家兔MRI图像（T1加权像、T2加权像、扩散加权成像）未见明显改变，伤后4～6h烫伤组家兔脑组织各部化中ADC值均明显降低（F值为0．492～2．271，P值均小于0．05）．烫伤组家兔伤后2～6h脑组织各部位中AQP4蛋白表达趋势大体一致，均明显高于正常对照组（0．164±0．022～0．247±0．018），其中伤后311或4h达高峰（0．237±0．042～0．306±0．026），F值为2．420～11．439，P值均小于0．05。AQP4蛋白在脑组织各部位的表达均与相应ADC值变化呈显著负相关，其r值为-0．489～-0．337，P〈0．05或P〈0．01，烫伤组家兔伤后各相点脑组织各部位中AQP4 mRNA表达均明显高于正常对照组（F值为39．992～238．584，P值均小于0．05），伤后2h达高峰，且在脑组织各部位表达趋势大体一致、结论家兔严重烫伤后早期脑水肿（伤后6h以内）以细胞毒性脑水肿为主，AQP4可能在其形成过程中发挥生要作用．ADC值对于反映AQP4变化，进而无创、便捷评估脑水肿发展状况可能具有重要参考价值。

Objective To observe expression pattern of aquaporin 4 （AQP4） in brain lissue of severely scalded rabbit during early stage, of brain edema and ils relalionship with signal changes in magnelic resonance imaging （MRI） , and to explore the feature of water transmembrane transportation in brain edema at early stage after severe scald. Methods Thirty-five heahhy New Zealand while ral）hits were divided into control group （C, n = 5 ） and scald group （S, n = 30） according to the random number table. Rabbits in S group were inflicted with 50% TBSA full-thickness scald with brain edema （ confirmed by histopathologic examination）. At post scald hour （PSH） 1. 2, 3. 4, 5. and 6, sigmd change in cerebral Ml＇ll, as well as dynamic change in apparent diffusion coefficient （ADC） were examined in rabbits of S group. Specimens were harvested from frontal corlex, parietal cortex, temporal lobe cortex, basal ganglia, and cerebellum in rabbits of S group for determination of protein and gene expressions of AQP4 with immunohistochemical method and RT-PCR. Above-mentioned indexes were also determined in C group. Data were processed with oneway anah.sis of variance and linear correlation analysis （between protein expression of AQP4 and ADC value）. Results There was no significant change in image signal of MRI al each time poinl in S group as compared with that in C group, including TIWI, T2WI, and DWI. Compared with those in C group, ADC in S group at PSH 4, 5, and 6 were significantly decreased （ with F values from 0. 492 to 2.271, P values all below 0.05 ）. The expression of AQP4 protein in each part of brain tissue in S group was obviously increased at PSH 2, 3,4, 5, and 6 as compared with those in C group （ from 0. 164 ± 0. 022 to 0. 247 ± 0. 018）, and it peaked at PSH 3 or 4 （ from 0. 237 ± 0. 042 to 0. 306± 0. 026）, with F values from 2. 420 to 11. 439, P values all below 0.05. The expressions of AQP4 protein were similar in brain tissue of all regions, and they were negatively correlated with corresponding ADC values （with r values from - 0. 489 to - 0. 337, P 〈 0. 05 or P 〈 0.01 ）. Compared with that in C group, the expression of AQP4 mRNA in each part of brain tissue in S group was obviously increased at each time point, and it reached the peak at PSH 2 （with F values from 39. 992 to 238. 584, P values all below 0.05 ）. The expressions of AQP4 mRNA were similar in all brain tissue regions. Conclusions Brain edema within 6 hours after severe scald was mainly characterized by cytotoxicity, in which AQP4 may play an important role. ADC value may have important reference value for non-invasive and convenient assessment of development of brain edema.