Department II of Internal Medicine and the Center for Molecular Medicine Cologne, University of Cologne, 50937 Cologne, Germany.
Am J Pathol. 2013 Feb;182(2):332-8. doi: 10.1016/j.ajpath.2012.11.002. Epub 2012 Dec 13.
Podocytes, the visceral epithelial cells of the kidney glomerulus, elaborate primary and interdigitating secondary extensions to enwrap the glomerular capillaries. A hallmark of podocyte injury is the loss of unique ultrastructure and simplification of the cell shape, called foot process effacement, which is a classic feature of proteinuric kidney disease. Although several key pathways have been identified that control cytoskeletal regulation, actin dynamics, and polarity signaling, studies into the dynamic regulation of the podocyte structure have been hampered by the fact that ultrastructural analyses require electron microscopic imaging of fixed tissue. We developed a new technique that allows for visualization of podocyte foot processes using confocal laser scanning microscopy. The combination of inducible and mosaic expression of membrane-tagged fluorescent proteins in a small subset of podocytes enabled us to acquire light microscopic images of podocyte foot processes in unprecedented detail, even in living podocytes of freshly isolated glomeruli. Moreover, this technique visualized oscillatory glomerular contractions and confirmed the morphometric evaluations obtained in static electron microscopic images of podocyte processes. These data suggest that the new technique will provide an extremely powerful tool for studying the dynamics of podocyte ultrastructure.
足细胞是肾脏肾小球的内脏上皮细胞，它们伸出初级和交错的次级突起，包裹肾小球毛细血管。足细胞损伤的一个标志是失去独特的超微结构和细胞形状的简化，称为足突融合，这是蛋白尿性肾脏疾病的一个典型特征。尽管已经确定了几个控制细胞骨架调节、肌动蛋白动力学和极性信号的关键途径，但由于超微结构分析需要对固定组织进行电子显微镜成像，因此对足细胞结构的动态调节的研究受到了阻碍。我们开发了一种新的技术，允许使用共焦激光扫描显微镜观察足细胞的足突。在一小部分足细胞中诱导和镶嵌表达膜标记的荧光蛋白的组合，使我们能够以前所未有的细节获取足细胞足突的光镜图像，甚至在新鲜分离的肾小球的活足细胞中也是如此。此外，该技术还可视化了肾小球的振荡收缩，并证实了在足细胞突起的静态电子显微镜图像中获得的形态计量评估。这些数据表明，该新技术将为研究足细胞超微结构的动力学提供一个极其强大的工具。
