Use and Isolation of Urinary Exosomes as Biomarkers for Diabetic Nephropathy

Abstract

Diabetes represents a major threat to public health and the number of patients is increasing alarmingly in the global scale. Particularly, the diabetic kidney disease (nephropathy, DN) together with its cardiovascular complications cause immense human suffering, highly increased risk of premature deaths, and lead to huge societal costs. DN is first detected when protein appears in urine (microalbuminuria). As in other persisting proteinuric diseases (like vasculitis) it heralds irreversible damage of kidney functions up to non-functional (end-stage) kidney and ultimately calls for kidney replacement therapy (dialysis or kidney transplantation). While remarkable progress has been made in understanding the genetic and molecular factors associating with chronic kidney diseases, breakthroughs are still missing to provide comprehensive understanding of events and mechanisms associated. Non-invasive diagnostic tools for early diagnostics of kidney damage are badly needed. Exosomes – small vesicular structures present in urine are released by all cell types along kidney structures to present with distinct surface assembly. Furthermore, exosomes carry a load of special proteins and nucleic acids. This “cargo” faithfully reflects the physiological state of their respective cells of origin and appears to serve as a new pathway for downstream signaling to target cells. Accordingly, exosome vesicles are emerging as a valuable source for disease stage-specific information and as fingerprints of disease progression. Unfortunately, technical issues of exosome isolation are challenging and, thus, their full potential remains untapped. Here, we review the molecular basis of exosome secretion as well as their use to reveal events along the nephron. In addition to novel molecular information, the new methods provide the needed accurate, personalized, non-invasive, and inexpensive future diagnostics.

Extracellular Vesicles in Renal Diseases

“…41 Several studies have, therefore, looked at various methods to isolate and enrich uEVs, which include ultracentrifugation with and without size exclusion chromatography (at 100,000-200,0003g for at least 1 h), ultrafiltration, 42 precipitation, and immunoisolation. 39,43,44 These different techniques have varying recovery rates of EVs. 42,44 Lower recovery rates of EVs have been especially a challenge in patients with heavy or nephrotic-range proteinuria.…”

“…39,43,44 These different techniques have varying recovery rates of EVs. 42,44 Lower recovery rates of EVs have been especially a challenge in patients with heavy or nephrotic-range proteinuria. Changes of urinary concentration represent another challenge for accurate analysis of uEVs.…”

“…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.…”

Effective enrichment of urinary exosomes by polyethylene glycol for RNA detection

“…They are suitable for most laboratories and easy to be utility, however, they are costly, especially if a large number of biological samples need to be processed. Besides that, various techniques including filtration [20][21][22], microfluidic-based method [23,24], immuno-affinity and peptide-based isolation [25], size-exclusion chromatography [26][27][28], and so on, have also been proposed for enrichment of exosomes. They have advantages and disadvantages, can be selected according to the experimental command.…”

Exosomes as mediators of intercellular communication: clinical implications

“…45 Exosomes were also reported to play a dual, beneficial and adverse, role in various cardiovascular disorders. 46,47 The beneficial function of mesenchymal stem cell-derived exosomes in cardiovascular disorders has been recently reviewed.…”