巢蛋白在足突广泛融合的肾小球中表达下调及与蛋白尿程度的相关性

Down-regulation of nestin expression in the glomeruli with foot process effacement and its correlation with the degree of proteinuria

目的观察中间丝蛋白类的巢蛋白（nestin）在足突广泛融合的肾小球中的表达及其与足突病变动态过程和蛋白尿产生的关系。方法免疫组化法检测nestin在人正常肾组织及微小病变肾组织中的表达。构建氨基核苷嘌呤霉素肾病大鼠模型，应用免疫组化、荧光实时定量PCR、Western印迹法检测注射嘌呤霉素后第1、4、10、20天大鼠肾小球中nestin的分布与表达；电镜观察肾脏足细胞改变，测定尿蛋白量（24h）。分析nestin的变化与蛋白尿的相关性。结果免疫组化显示nestin在人类微小病变肾小球中的表达较正常组织显著下调（0．93±0．08比1．65±0．12，P〈0．05）。在嘌呤霉素损伤足细胞早期，肾小球nestin的表达曾有一过性增加（mRNA和蛋白水平分别为对照组的1．23倍和1．48倍，P〈0．05），随后持续下降。nestin的mRNA水平在嘌呤霉素注射后第4天时降至对照组的35．8％；第10天时为对照组的12．1％（均P〈0．01）；病变好转后开始上升，恢复为对照组的65．8％（P〈0．05）。Western印迹检测nestin蛋白改变也有类似的趋势，嘌呤霉素注射后第4天，nestin蛋白水平有所下降，为对照组的77．0％（P〈0．05）；至大量蛋白尿的第10天，nestin蛋白水平仅为对照组的58．0％（P〈0．05）；而随着病变的恢复，嘌呤霉素注射后第20天时nestin蛋白量恢复为对照的83．4％。Pearson相关分析结果显示，注射嘌呤霉素后nestinmRNA（r=-0．667，P〈0．05）及蛋白（r=-0．621，P〈0．05）表达与尿蛋白量（24h）均呈负相关。结论在以足突广泛融合为特征的肾脏病变中，肾小球中间丝蛋白nestin表达显著减少，并与蛋白尿程度呈负相关，提示nestin可能参与了足细胞形态和功能的维持。

Objective To investigate the expression of nestin, a type Ⅵ intermediate filament protein in the glomeruli with foot process effacement and the potential relationship between nestin expression in the kidney and the degree of proteinuria. Method Immunohistochemistry was used to determine the localization of nestin in the kidney samples obtained from needle biopsies of normal human and patients with minimal change disease （MCD）. Puromycin aminonucleoside （PAN） nephrosis rat models were established by a single intraperitoneal injection of PAN. Both real time quatitative reverse PCR and Western blot methods were applied to evaluate the levels of nestin expression at day 1, 4, 10 and 20 after PAN injection. Results Immunohistochemistry showed that the expression of nestin in glomeruli of MCD patients was significantly reduced compared with normal samples （0.93±0.08 vs 1.65 ±0.12, P〈0.05） . The mRNA and protein expressions of nestin in the rat kidney were transitorily increased by 1.23 folds and 1.48 folds of control group （NC） after Ⅰ day of PAN injection （P〈0.05）, then decreased quickly in the following days. The mRNA levels of nestin in the kidney were 35.8% and 12.1% of NC after 4 days and 10 days of PAN injection, respectively, （P〈0.01） as determined by real time PCR. After 20 days of PAN injury, nestin mRNA expression partly recovered to 65.8% of NC （P〈 0.05 ）. The protein levels of nestin detected by Western blot presented the similar trend, which were 77.0%, 58.0% and 83.4% of NC after 4 days, 10 days and 20 days of PAN injection, respectively （P〈0.05）. The degree of proteinuria in puromycin aminonucleoside nephrosis rats was negatively correlated with both mRNA and protein levels of nestin in the kidney（r=-0.667 ,P〈0.05 and r =-0.621, P 〈0.05, respectively ）. Conclusions The expression of intermediate filament protein nestin is down-regulated in the kidney characterized with foot process effacement and negatively correlated with the degree of proteinuria in puromycin aminonucleoside nephrosis rats. Nestin may play a potential role in modulating the structure and function of podocyte.