Urinary exosomes: A reservoir for biomarker discovery and potential mediators of intrarenal signalling

Abstract

Over the last decade, there has been increasing research interest in urinary exosomes and their relationship with kidney physiology and disease. Protocols for isolating urinary exosomes have been refined and the exosomal proteome has been extensively catalogued and reported to contain proteins from the kidney's glomerulus and all sections of the nephron. In animal and human biomarker discovery studies, this proteome changes to reflect the underlying pathophysiology of certain kidney diseases. In addition to proteins, exosomes from urine have been demonstrated to contain RNA species, another new reservoir for biomarker discovery. Exosomes have the capacity to shuttle their cargo between kidney cells and change the recipient cell's proteome and function, and may represent a mechanism for cell-to-cell signalling along the nephron. Significant challenges remain; methods for urinary exosome collection need optimisation if "real-life" clinical utility is to be achieved, consensus is needed regarding normalisation of changes in exosomal protein and RNA, larger scale exosome biomarker validation studies remain to be performed, and whether exosomes signal between cells in vivo remains an intriguing, but untested, hypothesis.

Differential protein profiling of renal cell carcinoma urinary exosomes

“…27 In order to validate the exosome purification protocol, we performed western blot analysis on the ultracentrifugation pellets, in comparison with starting urine samples and the ultracentrifugation supernatants (after suitable protein concentration), using antibodies against three commonly used urinary exosomal markers, CD9, TSG101 and Flotillin-1. 28 Results show that urinary exosome-associated protein signals were predominant in the vesicle fraction, and nearly undetectable in total urine or the supernatant (Fig. 1A).…”

Extracellular Vesicles in Renal Diseases

“…41 More detailed discussion of these challenges can be found in other review papers. 3,44 Currently, there is no single detection technique that can measure the entire size range of EVs (from 30 to 1000 nm). Exosomes are analyzed using a variety of detection techniques.…”

“…3,4 Exosomes are formed by intraluminal budding of endosomal compartments, which create MVBs (Figure 1). 10 Exosomes can, therefore, incorporate cargo, such as soluble proteins, mRNAs, microRNAs (miRNAs), noncoding RNA, mitochondrial DNA, transcription factors, and other cytosolic components and molecules.…”

“…3,4 EVs were initially thought as artifacts or cell dust, 5 but there is accumulating evidence for their important role as messengers for cell signaling and communication in normal and disease states. 1,2,6,7 They may function in the transfer of proteins, lipids, and nucleic acids and represent a novel type of biomarker.…”

Diagnosis of prostate cancer via nanotechnological approach

“…Many reports have demonstrated that urine contains a variety of biomarkers that could indicate diseases. [122][123][124][125][126] Urine contains both urinary and systemic information since urine is in direct contact with urogenital organs and gets filtered from serum via glomerular filtration. Considering genitourinary organs are in direct contact with the body fluid, it is appealing to use urine for prostate cancer diagnoses in a noninvasive manner.…”