Quantification of molecular heterogeneity in kidney tissue by targeted proteomics.

Renal diseases are driven by alterations in the entity of proteins within the kidney, at the level of single cells, nephron subunits (such as glomerulus and tubule), tissues and body fluids. Histologically, kidney diseases are extremely heterogeneous. Mass-spectrometry based proteomics provides a unique opportunity to interrogate heterogeneity and dynamics of various proteome layers within the kidney to better understand physiology and pathophysiology, and to translate signaling networks into therapies. Yet, the success of this endeavor will largely depend on improving proteomic data acquisition methods toward increased reproducibility. Here, we provide an overview of targeted proteomics studies in renal tissue and their insights into major renal diseases such as diabetic nephropathy, acute kidney injury and chronic kidney disease. The technical approaches currently include antibody-based and mass spectrometry based approaches, range from single-cells to single-nephrons to bulk tissue proteomic acquisitions, and are applied to physiological studies and translational approaches in biomarker discovery. Within this context, we identify key challenges in proteomics of kidney biopsies. We also suggest that novel models of translational nephrology have increased need for targeted acquisition of proteomics data with focus on primary urinary cells, organoids and induced renal epithelial cells (IRECs). In conclusion, targeted proteomics will be very beneficial to identify heterogenic disease mechanisms that drive renal disease and further emerge as an important tool in translational kidney research. SIGNIFICANCE: Improved targeted proteomics technologies will be an important cornerstone of renal systems medicine in order to identify and tackle the heterogenic disease mechanisms driving renal disease.