miR-21通过PTEN介导肾小管上皮细胞转分化

Most chronic kidney injuries inevitably progress to irreversible renal fibrosis. Tubular epithelial-to-mesenchymal transition (EMT) is recognized to play pivotal roles in the process of renal fibrosis. However, a comprehensive understanding of the pathogenesis of renal scar formation and progression remains an urgent task for nephrologists. The endogenously produced microRNAs (miRNAs), proved to play important roles in gene regulation, probably regulate most genes involved in EMT. In our preliminary studies, we applied microarray analysis to investigate the expression profiles of miRNA in murine interstitial fibrotic kidneys induced by unilateral ureteral obstruction (UUO). It was found that, the expression of miR-21 was significantly upregulated in obstructed renal tissues. And modulating the expression of miR-21 could affect TGFβ1-induced EMT in cultured kidney epithelial cells , suggesting miR-21 may involved in the molecular mechanisms of renal tubular EMT. Further experements showed that miR-21 mimics down-regulated PTEN's (phosphatase and tensin homolog) protein level. In next study, we plan to use in situ hybridization to localize miR-21's expression in kidney tissues. The luciferase reporter gene technology will be used to identify if PTEN is the target of miR-21.To change the expression of miR-21 in vivo, we can use the tail vein injection of chemically modified miR-21 mimics and repressor, then investigate the expression level of of PTEN and EMT-related indicators in the renal tissues.

肾间质纤维化是慢性肾脏病预后的决定因素。肾小管上皮细胞转分化（EMT）是肾间质纤维化的重要致病机理。近来miRNAs在EMT中的作用备受国内外关注。前期研究中，我们通过miRNAs芯片筛选发现，UUO大鼠肾组织中miR-21表达显著上调，且改变miR-21表达能影响大鼠肾上皮细胞中TGFβ-1诱导的EMT，提示其可能与肾小管EMT的分子机制有关；进一步试验显示miR-21的模拟物能降低PTEN的蛋白质水平。本研究拟在此基础上，在体内和体外试验中运用miRNA原位杂交、荧光素酶报告基因等技术确立miR-21与PTEN的表达水平和EMT相关指标的相关性；通过尾静脉注射化学修饰的miR-21模拟物和阻遏物，观察肾组织PTEN和EMT相关指标的表达水平，进一步在体内实验中确立miR-21和EMT以及PTEN的表达关系。

肾间质纤维化是慢性肾脏病预后的决定因素。肾小管上皮细胞转分化（EMT）是肾间质纤维化的重要致病机理。近来miRNAs在EMT中的作用备受国内外关注。前期研究中，我们通过miRNAs芯片筛选发现，单侧输尿管梗阻 (UUO)大鼠肾组织中miR-21表达显著上调，且改变miR-21表达能影响大鼠肾上皮细胞中TGFβ-1诱导的EMT，提示其可能与肾小管EMT的分子机制有关；进一步试验显示miR-21的模拟物能降低PTEN的蛋白质水平。本研究在此基础上，在体内试验中运用miRNA原位杂交技术确认UUO肾组织中表达上调的miR-21定位于肾小管上皮细胞中；在培养的肾小管上皮细胞中升高或者降低miR-21的表达能影响PTEN的蛋白质水平；miR-21抑制剂能阻断TGF-β1诱导的Akt信号激活；而且PI3K/Akt抑制剂能阻断miR-21 模拟物诱导的EMT。综上所述，miR-21在肾小管上皮－间充质转分化的体内和体外模型中表达均显著升高，升高的miR-21能通过下调其靶目标——PTEN水平来激活PKB/Akt信号途径，从而导致EMT的发生。