人肾微血管内皮细胞转分化在移植肾间质纤维化形成中的作用

The role of renal microvascular endothelial-mesenchymal transition in transplant renal interstitial fibrosis formation

目的：探讨人肾微血管内皮细胞-间充质细胞转分化（endothelial-mesenchymal transition,EndMT）在移植肾间质纤维化形成中的意义及相关机制。方法：通过对南京医科大学第一附属医院25例慢性移植肾失功能（chronic allograft dysfunction,CAD）患者和25例正常人血生化指标进行分析,对移植肾组织标本和正常肾组织标本进行糖原（PAS）和马松三色（Masson）染色检查分析,观察两组肾功能、肾小管萎缩、肾小球塌陷及肾间质纤维化程度的差异。用免疫组织化学和间接免疫荧光双重染色方法检测两组肾组织标本中血管内皮细胞标志物CD34和肌成纤维细胞标志物α-平滑肌细胞肌动蛋白（α-smooth muscle actin,α-SMA）以及转化生长因子-β1（transforming growth factor-β1,TGF-β1）的表达和分布特点。进一步以原代人脐静脉内皮细胞（human umbilical vein endothelial cells,HUVECs）为体外研究对象,以TGF-β1（5 ng/ml）作用0~72 h,采用免疫印迹方法观察细胞中CD34和α-SMA的表达变化。结果：与正常人相比,CAD患者血清肌酐水平明显升高,PAS和Masson三色染色结果显示CAD患者移植肾组织中出现明显肾小管萎缩、肾小球塌陷及肾间质纤维化改变;半定量统计分析结果表明两者间存在统计学差异（P〈0.01）。免疫组织化学及间接免疫荧光染色结果表明,与正常组相比,CAD组中CD34阳性表达率降低而α-SMA及TGF-β1阳性表达率显著升高,CAD组中部分肾小球和间质微血管内皮细胞呈CD34和α-SMA双重染色阳性。体外研究显示,TGF-β1作用于HUVECs细胞后,随着时间延长,CD34表达逐渐降低而α-SMA表达逐渐增多,与对照组相比,具有统计学差异（P〈0.01）。结论：人肾微血管内皮细胞可能在TGF-β1介导下通过发生EndMT现象进而在移植肾间质纤维化形成中起重要作用。

Objective： To explore the role and mechanism of human renal microvascular endothelial-mesenchymal transition （EndMT） in transplant renal interstitial fibrosis formation. Methods：Based on serum and renal allograft tissue samples from 25 eases of chronic renal allograft dysfunction （CAD） patients and 25 normal renal tissue samples and serum, we observed the changes of renal function and the degree of renal tubular atrophy, renal glomerular collapse and interstitial fibrosis by blood biochemical, periodic acid-schiff staining （PAS） and Mason trichromatic staining assays. Using immunohistochemical and indirect immunofluorescence double staining assays, we also detected the expression and distributions of vascular endothelial cell marker CD34 and myofibroblast marker a-Smooth muscle actin （α-SMA）,and transforming growth factor-β1 （TGF-β1） in renal tissue samples of the two groups. Human umbilical vein endothelial cells（HUVECs） set as the object of study and stimulated by TGF-β1（5 ng/ml） respectively for 0- 72 h in vitro. Western blotting was used to observe the expression of CD34 and α-SMA. Results：Compared with the normal group, serum creatinine levels in the CAD group increased significantly. The results of PAS and Masson staining showed that renal tubular atrophy,glomerular collapse and interstitial fibrosis were more apparent in transplanted kidneys of the CAD group. Indirect immunofluorescence staining and immunohistochemical results showed that the positive stains of CD34 reduced,while the positive expression of α-SMA and TGF-β1 increased significantly in the CAD group compared with the normal group. Indirect immunofluoreseence double staining showed that the double positive stains of CD34 and α-SMA could be found in the parts of glomerular and interstitial microvascular endothelial cells in the CAD group. The results of Western blotting demonstrated that after treatment with TGF-β1 ,the expression of CD34 reduced and α-SMA expression increased in an time-dependent mean in HUVECs as compared with the normal group （P 〈 0.01 ）. Conclusion：Human renal microvaseular EndMT may be mediated by TGF-β1 and plays an important role in transplant renal interstitial fibrosis formation.