Proximal tubule cells in blood and urine have potential as biomarkers for kidney disease biopsies

Early diagnosis and treatment is pivotal to the management of kidney disease, whereas the pathological mechanisms and minimally invasive diagnostic method still need to be investigated. In the present study, single-cell RNA sequencing (scRNA-seq) was used to evaluate the heterogeneity of kidney diseases in single cell level. Cellular gene expression profiles of cells of renal tissue, peripheral blood mononuclear cells (PBMCs) and urine from four nephritis patients were performed. Our analysis revealed 12 subsets of renal cells and leukocytes, including fibroblast cells, mesangial cells, epithelial cells, proximal tubule cells (PTCs), and 6 types of immune cells, CD8+ T cell, macrophages (MC), nature killer cells (NK), dendritic cells (DC), B cell and neutrophils. PTCs were detected in both PBMC and urine, while PTC was negative in healthy blood sample. Multiple populations of fibroblast cells, mesangial cells and PTCs demonstrated pro-inflammatory or pro-apoptotic responses. Gene expression analysis suggested that chemotactic and activating effect of inflammatory PTCs and fibroblasts on neutropils were critical for the development and progress of nephritis, which was supported by the widely overexpressed pro-inflammatory genes in these cells. Gene expression profiles of inflammatory PTCs in PBMC, urine and kidney are highly correlated, indicating the high possibility of urine and PBMC PTCs in serving as a surrogate for kidney biopsies. Overall design: In the present study, we aim to find out novel biomarkers from blood or urine by analysis cells from blood and urine using scRNA-seq, which may provide alternative minimally or noninvasive diagnostic method for kidney diseases.