Urinary exosomes as potential source for identification of biomarkers for kidney damage: Comparing methodologies

Abstract

Early detection of chronic kidney diseases such as diabetic nephropathy is an area of emerging research interest. To date, most efforts focused on either histological analysis of biopsied renal tissue or investigation of protein, mRNA, or microRNA levels in kidney or urine. Urine contains small microvesicles (40-100 nm in size), commonly called exosomes, that are released by cells lining the inner walls of nephron segments. It is becoming clear that exosomes released into the urine may provide valuable information for identifying biomarkers of kidney damage, particularly under conditions of renal dysfunction and injury. Several methods have been developed to isolate exosomes from urine, including ones based on ultracentrifugation, nanomembrane concentration and precipitation techniques. We have previously compared different methods for the extraction of urinary exosomes for downstream applications involving analysis of protein, mRNA, and miRNA. In this chapter, we outline the basic principles, as well as the strengths and weaknesses, of each method for the isolation of exosomes from human urine. The goal of this chapter is to provide a foundation upon which researchers may select the method of urinary exosome extraction most suitable for their specific downstream needs.