Quantitative Imaging of Podocyte Foot Processes in the Kidney Using Confocal and STED Microscopy

Abstract

Morphological alterations to the kidney filter, particularly to podocyte foot processes, are seen in most types of glomerular diseases. Due to the nanoscale dimensions of the filter, visualization of such alterations has historically relied on electron microscopy. However, with recent technical development, it is now possible to also visualize podocyte foot processes, as well as other parts of the kidney filtration barrier, with light microscopy. With developments both in sample preparation, imaging, and image analysis, these new tools are becoming increasingly applied in kidney research, due to their demonstrated quantitative potential. We here present an overview of these protocols that can be applied to samples that have been fixed and stored using most standard procedures used today (i.e., PFA fixed, fresh frozen, formalin-fixed and paraffin-embedded (FFPE)). We additionally introduce tools for quantitative image analysis of foot process morphology and foot process effacement.

Keywords: Image analysis; Kidney; Optical clearing; Podocytes; Sample preparation; Super-resolution microscopy.