Quantitative Three-Dimensional Tissue Cytometry to Study Kidney Tissue and Resident Immune Cells.

Analysis of the immune system in the kidney relies predominantly on flow cytometry. Although powerful, the process of tissue homogenization necessary for flow cytometry analysis introduces bias and results in the loss of morphologic landmarks needed to determine the spatial distribution of immune cells. An ideal approach would support three-dimensional (3D) tissue cytometry: an automated quantitation of immune cells and associated spatial parameters in 3D image volumes collected from intact kidney tissue. However, widespread application of this approach is limited by the lack of accessible software tools for digital analysis of large 3D microscopy data. Here, we describe Volumetric Tissue Exploration and Analysis (VTEA) image analysis software designed for efficient exploration and quantitative analysis of large, complex 3D microscopy datasets. In analyses of images collected from fixed kidney tissue, VTEA replicated the results of flow cytometry while providing detailed analysis of the spatial distribution of immune cells in different regions of the kidney and in relation to specific renal structures. Unbiased exploration with VTEA enabled us to discover a population of tubular epithelial cells that expresses CD11C, a marker typically expressed on dendritic cells. Finally, we show the use of VTEA for large-scale quantitation of immune cells in entire human kidney biopsies. In summary, we show that VTEA is a simple and effective tool that supports unique digital interrogation and analysis of kidney tissue from animal models or biobanked human kidney biopsies. We have made VTEA freely available to interested investigators via electronic download.