PTEN调控足细胞骨架重排介导糖尿病肾病发病机制的研究

Diabetic kidney disease (DKD) is one of the major causes of end-stage renal disease (ESRD). Podocyte dysfunction is a critical factor to cause proteinuria and DKD, however the underneath mechanism is largely unknown. PTEN is one of the most important phosphatases to mediate cells cell growth, metabolism and cytoskeletal rearrangement and its expression is significantly decreased in glomeruli of patients with DKD. Our preliminary studies show that PTEN involves in the pathogenesis of proteinuria and DKD by regulating podocyte cytoskeletal rearrangement. This project intends to investigate the pathological mechanisms by which PTEN causes podocyte dysfunction and proteinuria in mouse with podocyte-specific PTEN knockout. We will use the Cre/loxP technique, transfection, glomerular isolation and other molecular methods to examine how PTEN influences the structure and functions changes in podocyte. We propose a novel mechanism that down-regulation of PTEN in podocyte activates RAC1 signaling pathway resulting in podocyte skeletal rearrangement and foot processes enfacement, ultimately leading to proteinuria and DKD. The proposal is expected to discover a new mechanism involving in the pathogenesis of DKD and might provide new therapeutical strategy to prevent proteinuria and diabetic kidney disease.

糖尿病肾病（DKD）是导致终末期肾病的主要病因之一。肾小球中足细胞功能紊乱是糖尿病产生蛋白尿和肾小球硬化的重要起因，其发病机制目前尚不明确。PTEN是体内最重要的磷酸酶之一，主要功能为调节细胞生长、代谢和细胞骨架重排, 而它的表达在DKD病人肾小球中显著下降。我们的前期研究表明PTEN调控足细胞骨架重排并参与DKD发病。本课题拟对特异性足细胞敲除PTEN后，研究小鼠足细胞功能紊乱导致蛋白尿和DKD的发生、发展病理机制。采用组织特异性Cre/loxP基因敲除技术、细胞转染、肾小球分离等方法，分析PTEN如何调控足细胞结构和功能，进而提出糖尿病抑制足细胞中PTEN表达, 从而激活RAC1信号通路，引起足细胞骨架重排和足突融合与脱落，最终导致蛋白尿产生和糖尿病肾病这一新的机制。本研究有望提出并验证DKD发病的新机制，并给未来防治DKD提供新思路。

动物实验及体外培养足细胞证实糖尿病肾病肾小球足细胞PTEN表达下降，体外实验中用siRNA 敲抑PTEN及PTEN的抑制剂证实PTEN活性下降促进细胞骨架重排，增加白蛋白的滤过。使用病毒过表达足细胞PTEN，在一定程度上可改善足细胞细胞骨架重排、减少白蛋白漏出。特异性敲除足细胞PTEN可促进高脂饮食小鼠蛋白尿的明显增加，电镜显示足突融合明显和毛细血管袢闭塞，进一步促进糖尿病肾病的发展；PTEN增强剂反应停可改善小鼠蛋白尿，延缓糖尿病肾病的发展。本研究证实糖尿病时抑制了足细胞中 PTEN 表达,从而激活 RAC1 信号通路，引起足细胞骨架重排和足突融合与脱落，最终导致蛋白尿产生和糖尿病肾病这一新的机制。