磁敏感加权成像评估单侧输尿管梗阻兔模型致肾纤维化的可行性

Feasibility of susceptibility weighted imaging in the evaluation of renal fibrosis induced by unilateralureteral obstruction in white rabbits

目的评价磁敏感加权成像（SWI）能否反映单侧输尿管梗阻模型（UUO）致肾纤维化的发展过程。方法32只4～5月龄新西兰大白兔建立UUO模型（RF组），按梗阻时间的长短分RF-2W、RF-4W、RF-6W和RF-8W组4个亚组，另8只作为假手术组（Sham组）。分别于建模后2、4、6和8周行T2加权像（T2WI）和SWI扫描，扫描后处死动物获得标本，行苏木精-伊红（HE）、Masson染色观察兔肾肾小管损伤和间质纤维化等，分析SWI融合图的相对信噪比（rSNR）与肾纤维化程度的关系。利用单因素方差分析分别比较Sham组和RF四个亚组的皮质和内、外髓的rSNR的统计学差异。结果Sham组和RF-2W、4W、6W和8W组的内髓的rSNR逐渐降低，分别为2.29±0.18、1.73±0.30、1.67±0.08、1.42±0.28、1.12±0.15（F＝25.876，P〈0.01）；RF-2W组外髓、皮质的rSNR与Sham组相比升高，其后各组随时间逐渐降低（F＝5.230、7.621，均P〈0.05）。病理检查发现，Sham组肾小管形态正常，上皮细胞未见凋亡坏死；RF-2W组肾小管明显扩张，小管上皮细胞变性、坏死，炎性细胞散布，多发条带状蓝染，随着梗阻时间延长，肾小管塌陷，炎性细胞和成纤维细胞明显增多，蓝染面积显著增加。结论SWI成像可用来反映兔UUO模型肾纤维化的病理发展过程，是一种无创检测肾纤维化的影像手段。

ObjectiveTo evaluate the feasibility of susceptibility weighted imaging （SWI） to reflect the progression of renal fibrosis （RF） induced by unilateral ureteral obstruction （UUO） in rabbits.MethodsTotal of 32 New Zealand white rabbits （aged 4-5 months） were used to establish the UUO model （RF group） and were divided into 4 subgroups （including RF-2W group, RF-4W group , RF-6W group and RF-8W group） according to the duration of obstruction（2, 4, 6 and 8 weeks）. Another 8 rabbits, underwent sham operation, were used as the control group （Sham group）. T2 weighted imaging （T2WI） and SWI sequences were performed on the rabbits at 2, 4, 6 and 8 weeks after UUO, respectively. Rabbits were sacrificed and specimens were obtained after MR examination, then hematoxylin＆eosin staining and Masson staining were performed to explore the renal tubular injury and interstitial fibrosis. The relationship between the relative signal-to-noise ratio（rSNR）measured on the SWI fusion maps and the degree of renal fibrosis was analyzed. Analysis of variance was used to compare the difference of rSNRs among 5 groups.ResultsThe rSNRs of the inner medulla gradually decreased over time, the rSNRs of Sham group, RF-2W group, RF-4W group, RF-6W group and RF-8W group was 2.29±0.18, 1.73±0.30, 1.67±0.08, 1.42±0.28, 1.12±0.15, respectively （F=25.876, P〈0.01）. In RF-2W group, the rSNRs of the outer medulla and cortex increased when compared with those in the Sham group, then they decreased gradually over time in the other groups （F=5.230, 7.621, both P〈0.05）. The pathological results demonstrated that the morphology of renal tubules in Sham group was normal and no apoptosis or necrosis was seen in the tubular epithelial cells. In the RF-2W group, the main pathological manifestations included renal tubules dilatation, tubular epithelial cell degeneration or necrosis and the infiltration of inflammatory cell. In Masson staining, lots of blue areas were present in the interstitial. As the obstruction time prolonged, the renal tubular collapse, inflammatory cells and fibroblasts increased significantly. Meanwhile blue area also increased significantly in Masson staining.ConclusionSWI can be used as a noninvasive method to evaluate the pathological progression of fibrosis in the rabbit UUO model.