Extracellular Vesicles in Renal Diseases: More than Novel Biomarkers?

Prognostic significance of circulating microparticles in IgA nephropathy

PURPOSE

Endothelial injury, involved in the pathogenesis of renal fibrosis, can generate microparticles (MPs). These are 0.1-1 µm membrane-bound vesicles shed from the damaged or activated cell surfaces. We analyzed the presence of circulating MPs and EnMPs in IgAN and correlated with markers of endothelial injury and disease activity.

METHODS

The study included 30 IgAN (mean age 31.5 ± 9 years), 25 healthy controls and Lupus nephritis (n = 10) as disease controls. Circulating MPs were quantitated by Flow cytometry and EnMPs were analyzed using anti-CD31-FITC and anti-CD146-PE antibodies. Their levels were correlated with serum von Willebrand Factor, histological Oxford MEST-C score and renal outcome. A prospective validation group of 20 patients of biopsy-proven IgA nephropathy was also included.

RESULTS

IgAN had significantly higher levels of MPs, EnMPs and vWF compared to controls. On multivariate analysis, plasma levels of total MPs, EnMPs and serum vWF correlated significantly with the presence of hypertension and E1 on histology. E1 and high MPs (> 130 counts/µl) were associated with shorter time to doubling of serum creatinine. MPs cutoff level of 130 counts/µl had a sensitivity of 75%, specificity of 93.3% and diagnostic accuracy of 89.5% for E1 in the validation cohort.

CONCLUSION

Circulating MPs and EnMPs in IgAN correlate with E1 on histology and have a potential as non-invasive biomarkers to predict disease activity and renal outcome.

Understanding exosomes: Part 2-Emerging leaders in regenerative medicine

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with the ability to communicate with other tissues and cell types over long distances. Their use in regenerative medicine has gained tremendous momentum recently due to their ability to be utilized as therapeutic options for a wide array of diseases/conditions. Over 5000 publications are currently being published yearly on this topic, and this number is only expected to dramatically increase as novel therapeutic strategies continue to be developed. Today exosomes have been applied in numerous contexts including neurodegenerative disorders (Alzheimer's disease, central nervous system, depression, multiple sclerosis, Parkinson's disease, post-traumatic stress disorders, traumatic brain injury, peripheral nerve injury), damaged organs (heart, kidney, liver, stroke, myocardial infarctions, myocardial infarctions, ovaries), degenerative processes (atherosclerosis, diabetes, hematology disorders, musculoskeletal degeneration, osteoradionecrosis, respiratory disease), infectious diseases (COVID-19, hepatitis), regenerative procedures (antiaging, bone regeneration, cartilage/joint regeneration, osteoarthritis, cutaneous wounds, dental regeneration, dermatology/skin regeneration, erectile dysfunction, hair regrowth, intervertebral disc repair, spinal cord injury, vascular regeneration), and cancer therapy (breast, colorectal, gastric cancer and osteosarcomas), immune function (allergy, autoimmune disorders, immune regulation, inflammatory diseases, lupus, rheumatoid arthritis). This scoping review is a first of its kind aimed at summarizing the extensive regenerative potential of exosomes over a broad range of diseases and disorders.

Exosomes and microvesicles in kidney transplantation: the long road from trash to gold

Kidney transplantation significantly enhances the survival rate and quality of life of patients with end-stage kidney disease. The ability to predict post-transplantation rejection events in their early phases can reduce subsequent allograft loss. Therefore, it is critical to identify biomarkers of rejection processes that can be acquired on routine analysis of samples collected by non-invasive or minimally invasive procedures. It is also important to develop new therapeutic strategies that facilitate optimisation of the dose of immunotherapeutic drugs and the induction of allograft immunotolerance. This review explores the challenges and opportunities offered by extracellular vesicles (EVs) present in biofluids in the discovery of biomarkers of rejection processes, as drug carriers and in the induction of immunotolerance. Since EVs are highly complex structures and their composition is affected by the parent cell's metabolic status, the importance of defining standardised methods for isolating and characterising EVs is also discussed. Understanding the major bottlenecks associated with all these areas will promote the further investigation of EVs and their translation into a clinical setting.

Expression of urinary exosomal miRNA-615-3p and miRNA-3147 in diabetic kidney disease and their association with inflammation and fibrosis

BACKGROUND

Diabetic kidney disease (DKD) is one of the most common chronic complications of type 2 diabetes mellitus (T2DM), and it is particularly important to identify a high-quality method for evaluating disease progression. Urinary exosomes contain microRNA that might promise early diagnostic and monitoring markers of DKD. The present study aimed to identify novel exosome-related markers associated with inflammation and fibrosis to assess the progression of DKD.

METHOD

Exosomes were extracted from the urine of 83 participants to determine the expression levels of miRNA-615-3p and miRNA-3147 in 20 healthy people, 21 patients with T2DM and 42 patients with DKD, as determined by RT-qPCR. The circulating expression level of TGF-β1 was detected by ELISA. Serum Cystatin C was measured by a latex-enhanced immunoturbidimetric method. The correlation analyses were performed for all clinical and laboratory parameters.

RESULT

The expression level of urinary exosomal miRNA-615-3p in DKD patients was significantly higher than that in the control group and the T2DM group by RT-qPCR. The expression of miRNA-3147 showed an upward trend in the three groups of subjects, but it was not statistically significant. The urinary exosomal miRNA-615-3p was positively correlated with serum Cystatin C, plasma TGF-β1, creatinine, BUN, PCR and 24-h urine protein, and negatively correlated with eGFR and albumin. The diagnostic efficacy of urinary exosomal miRNA-615-3p combined with the ACR was higher than that of ACR alone.

CONCLUSIONS

Urinary exosomal miRNA-615-3p may be used as a novel biomarker for evaluating the progression of DKD, and may be involved in the process of inflammation and fibrosis in DKD. The combined diagnosis of urinary exosomal miRNA-615-3p and ACR may be used as more stable and sensitive diagnostic criteria for DKD.

In-depth urinary and exosome proteome profiling analysis identifies novel biomarkers for diabetic kidney disease

Diabetic kidney disease (DKD) is a major microvascular complication of type 2 diabetes mellitus (T2DM). Monitoring the early diagnostic period and disease progression plays a crucial role in treating DKD. In this study, to comprehensively elucidate the molecular characteristics of urinary proteins and urinary exosome proteins in type 2 DKD, we performed large-scale urinary proteomics (n=144) and urinary exosome proteomics (n=44) analyses on T2DM patients with albuminuria in varying degrees. The dynamics analysis of the urinary and exosome proteomes in our study provides a valuable resource for discovering potential urinary biomarkers in patients with DKD. A series of potential biomarkers, such as SERPINA1 and transferrin (TF), were detected and validated to be used for DKD diagnosis or disease monitoring. The results of our study comprehensively elucidated the changes in the urinary proteome and revealed several potential biomarkers reflecting the progression of DKD, which provide a reference for DKD biomarker screening.

Regulation of NLRP3 Inflammasome Activation and Inflammatory Exosome Release in Podocytes by Acid Sphingomyelinase During Obesity

The activation of nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome has been reported to importantly contribute to glomerular inflammation and injury under different pathological conditions such as obesity. However, the mechanism mediating NLRP3 inflammasome activation in podocytes and subsequent glomerular injury remains poorly understood. Given that the ceramide signaling pathway has been reported to be implicated in obesity-related glomerulopathy (ORG), the present study was designed to test whether the ceramide-producing enzyme, acid sphingomyelinase (ASM), determines NLRP3 inflammasome activation and inflammatory exosome release in podocytes leading to glomerular inflammation and injury during ORG. In Smpd1trg/Podocre mice, podocyte-specific overexpression of Smpd1 gene which encodes ASM significantly exaggerated high-fat diet (HFD)-induced NLRP3 inflammasome activation in podocytes and immune cell infiltration in glomeruli compared to WT/WT mice. Smpd1 gene deletion, however, blocked these pathological changes induced by HFD in Smpd1-/- mice. Accompanied with NLRP3 inflammasome activation and glomerular inflammation, urinary excretion of exosomes containing podocyte marker and NLRP3 inflammasome products (IL-1β and IL-18) in Smpd1trg/Podocre mice on the HFD was much higher than that in WT/WT mice. In contrast, Smpd1-/- mice on the HDF had significantly lower urinary exosome excretion than WT/WT mice. Correspondingly, HFD-induced podocyte injury, glomerular sclerosis, and proteinuria were more severe in Smpd1trg/Podocre mice, but milder in Smpd1-/- mice compared to WT/WT mice. Using podocytes isolated from these mice, we demonstrated that visfatin, a prototype pro-inflammatory adipokine, induced NLRP3 inflammasome activation and enrichment of multivesicular bodies (MVBs) containing IL-1β in podocytes, which was much stronger in podocytes from Smpd1trg/Podocre mice, but weaker in those from Smpd1-/- mice than WT/WT podocytes. By quantitative analysis of exosomes, it was found that upon visfatin stimulation, podocytes from Smpd1trg/Podocre mice released much more exosomes containing NLRP3 inflammasome products, but podocytes from Smpd1-/- mice released much less exosomes compared to WT/WT podocytes. Super-resolution microscopy demonstrated that visfatin inhibited lysosome-MVB interaction in podocytes, indicating impaired MVB degradation by lysosome. The inhibition of lysosome-MVB interaction by visfatin was amplified by Smpd1 gene overexpression but attenuated by Smpd1 gene deletion. Taken together, our results suggest that ASM in podocytes is a crucial regulator of NLRP3 inflammasome activation and inflammatory exosome release that instigate glomerular inflammation and injury during obesity.

Role of extracellular vesicles in pathogenesis and therapy of renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (RIRI) is a complex disorder characterized by both intrinsic damage to renal tubular epithelial cells and extrinsic inflammation mediated by cytokines and immune cells. Unfortunately, there is no cure for this devastating condition. Extracellular vesicles (EVs) are nanosized membrane-bound vesicles secreted by various cell types that can transfer bioactive molecules to target cells and modulate their function. EVs have emerged as promising candidates for cell-free therapy of RIRI, owing to their ability to cross biological barriers and deliver protective signals to injured renal cells. In this review, we provide an overview of EVs, focusing on their functional role in RIRI and the signaling messengers responsible for EV-mediated crosstalk between various cell types in renal tissue. We also discuss the renoprotective role of EVs and their use as therapeutic agents for RIRI, highlighting the advantages and challenges encountered in the therapeutic application of EVs in renal disease.

Glomerular proteomic profiling reveals early differences between preexisting and de novo type 2 diabetes in human renal allografts

BACKGROUND

Diabetes mellitus (DM), either preexisting or developing after transplantation, remains a crucial clinical problem in kidney transplantation. To obtain insights into the molecular mechanisms underlying PTDM development and early glomerular damage before the development of histologically visible diabetic kidney disease, we comparatively analysed the proteome of histologically normal glomeruli from patients with PTDM and normoglycaemic (NG) transplant recipients. Moreover, to assess specificities inherent in PTDM, we also comparatively evaluated glomerular proteomes from transplant recipients with preexisting type 2 DM (T2DM).

METHODS

Protocol biopsies were obtained from adult NG, PTDM and T2DM patients one year after kidney transplantation. Biopsies were formalin-fixed and embedded in paraffin, and glomerular cross-sections were microdissected. A total of 4 NG, 7 PTDM and 6 T2DM kidney biopsies were used for the analysis. The proteome was determined by liquid chromatography-tandem mass spectrometry. Relative differences in protein abundance and significantly dysregulated pathways were analysed.

RESULTS

Proteins involved in cell adhesion, immune response, leukocyte transendothelial filtration, and cell localization and organization were less abundant in glomeruli from PTDM patients than in those from NG patients, and proteins associated with supramolecular fibre organization and protein-containing complex binding were more abundant in PTDM patients. Overall, proteins related to adherens and tight junctions and those related to the immune system, including leukocyte transendothelial migration, were more abundant in NG patients than in transplanted patients with DM, irrespective of the timing of its development. However, proteins included in cell‒cell junctions and adhesion, insulin resistance, and vesicle-mediated transport were all less abundant in PTDM patients than in T2DM patients.

CONCLUSIONS

The glomerular proteome profile differentiates PTDM from NG and T2DM, suggesting specific pathogenetic mechanisms. Further studies are warranted to validate these results, potentially leading to an improved understanding of PTDM kidney transplant pathophysiology and to the identification of novel biomarkers.

The role of pneumococcal extracellular vesicles on the pathophysiology of the kidney disease hemolytic uremic syndrome

Streptococcus pneumoniae-induced hemolytic uremic syndrome (Sp-HUS) is a kidney disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. This disease is frequently underdiagnosed and its pathophysiology is poorly understood. In this work, we compared clinical strains, isolated from infant Sp-HUS patients, with a reference pathogenic strain D39, for host cytotoxicity and further explored the role of Sp-derived extracellular vesicles (EVs) in the pathogenesis of an HUS infection. In comparison with the wild-type strain, pneumococcal HUS strains caused significant lysis of human erythrocytes and increased the release of hydrogen peroxide. Isolated Sp-HUS EVs were characterized by performing dynamic light-scattering microscopy and proteomic analysis. Sp-HUS strain released EVs at a constant concentration during growth, yet the size of the EVs varied and several subpopulations emerged at later time points. The cargo of the Sp-HUS EVs included several virulence factors at high abundance, i.e., the ribosomal subunit assembly factor BipA, the pneumococcal surface protein A, the lytic enzyme LytC, several sugar utilization, and fatty acid synthesis proteins. Sp-HUS EVs strongly downregulated the expression of the endothelial surface marker platelet endothelial cell adhesion molecule-1 and were internalized by human endothelial cells. Sp-HUS EVs elicited the release of pro-inflammatory cytokines (interleukin [IL]-1β, IL-6) and chemokines (CCL2, CCL3, CXCL1) by human monocytes. These findings shed new light on the overall function of Sp-EVs, in the scope of infection-mediated HUS, and suggest new avenues of research for exploring the usefulness of Sp-EVs as therapeutic and diagnostic targets. IMPORTANCE Streptococcus pneumoniae-associated hemolytic uremic syndrome (Sp-HUS) is a serious and underdiagnosed deadly complication of invasive pneumococcal disease. Despite the introduction of the pneumococcal vaccine, cases of Sp-HUS continue to emerge, especially in children under the age of 2. While a lot has been studied regarding pneumococcal proteins and their role on Sp-HUS pathophysiology, little is known about the role of extracellular vesicles (EVs). In our work, we isolate and initially characterize EVs from a reference pathogenic strain (D39) and a strain isolated from a 2-year-old patient suffering from Sp-HUS. We demonstrate that despite lacking cytotoxicity toward human cells, Sp-HUS EVs are highly internalized by endothelial cells and can trigger cytokine and chemokine production in monocytes. In addition, this work specifically highlights the distinct morphological characteristics of Sp-HUS EVs and their unique cargo. Overall, this work sheds new light into potentially relevant players contained in EVs that might elucidate about pneumococcal EVs biogenesis or pose as interesting candidates for vaccine design.

Phosphoproteome Profiling of uEVs Reveals p-AQP2 and p-GSK3β as Potential Markers for Diabetic Nephropathy

Diabetic nephropathy (DN) contributes to increased morbidity and mortality among patients with diabetes and presents a considerable global health challenge. However, reliable biomarkers of DN have not yet been established. Phosphorylated proteins are crucial for disease progression. However, their diagnostic potential remains unexplored. In this study, we used ultra-high-sensitivity quantitative phosphoproteomics to identify phosphoproteins in urinary extracellular vesicles (uEVs) as potential biomarkers of DN. We detected 233 phosphopeptides within the uEVs, with 47 phosphoproteins exhibiting significant alterations in patients with DN compared to those in patients with diabetes. From these phosphoproteins, we selected phosphorylated aquaporin-2 (p-AQP2[S256]) and phosphorylated glycogen synthase kinase-3β (p-GSK3β[Y216]) for validation, as they were significantly overrepresented in pathway analyses and previously implicated in DN pathogenesis. Both phosphoproteins were successfully confirmed through Phos-tag western blotting in uEVs and immunohistochemistry staining in kidney sections, suggesting that phosphoprotein alterations in uEVs reflect corresponding changes within the kidney and their potential as candidate biomarkers for DN. Our research proposes the utilization of phosphoproteins in uEVs as a liquid biopsy, presenting a highly feasible diagnostic tool for kidney disease.

Capturing the Kidney Transcriptome by Urinary Extracellular Vesicles-From Pre-Analytical Obstacles to Biomarker Research

Urinary extracellular vesicles (uEV) hold non-invasive RNA biomarkers for genitourinary tract diseases. However, missing knowledge about reference genes and effects of preanalytical choices hinder biomarker studies. We aimed to assess how preanalytical variables (urine storage temperature, isolation workflow) affect diabetic kidney disease (DKD)-linked miRNAs or kidney-linked miRNAs and mRNAs (kidney-RNAs) in uEV isolates and to discover stable reference mRNAs across diverse uEV datasets. We studied nine raw and normalized sequencing datasets including healthy controls and individuals with prostate cancer or type 1 diabetes with or without albuminuria. We focused on kidney-RNAs reviewing literature for DKD-linked miRNAs from kidney tissue, cell culture and uEV/urine experiments. RNAs were analyzed by expression heatmaps, hierarchical clustering and selecting stable mRNAs with normalized counts (>200) and minimal coefficient of variation. Kidney-RNAs were decreased after urine storage at -20 °C vs. -80 °C. Isolation workflows captured kidney-RNAs with different efficiencies. Ultracentrifugation captured DKD -linked miRNAs that separated healthy and diabetic macroalbuminuria groups. Eleven mRNAs were stably expressed across the datasets. Hence, pre-analytical choices had variable effects on kidney-RNAs-analyzing kidney-RNAs complemented global correlation, which could fade differences in some relevant RNAs. Replicating prior DKD-marker results and discovery of candidate reference mRNAs encourages further uEV biomarker studies.

Extracellular Vesicle MicroRNA in the Kidney

Most cells in our body release membrane-bound, nano-sized particles into the extracellular milieu through cellular metabolic processes. Various types of macromolecules, reflecting the physiological and pathological status of the producing cells, are packaged into such so-called extracellular vesicles (EVs), which can travel over a distance to target cells, thereby transmitting donor cell information. The short, noncoding ribonucleic acid (RNA) called microRNA (miRNA) takes a crucial part in EV-resident macromolecules. Notably, EVs transferring miRNAs can induce alterations in the gene expression profiles of the recipient cells, through genetically instructed, base-pairing interaction between the miRNAs and their target cell messenger RNAs (mRNAs), resulting in either nucleolytic decay or translational halt of the engaged mRNAs. As in other body fluids, EVs released in urine, termed urinary EVs (uEVs), carry specific sets of miRNA molecules, which indicate either normal or diseased states of the kidney, the principal source of uEVs. Studies have therefore been directed to elucidate the contents and biological roles of miRNAs in uEVs and moreover to utilize the gene regulatory properties of miRNA cargos in ameliorating kidney diseases through their delivery via engineered EVs. We here review the fundamental principles of the biology of EVs and miRNA as well as our current understanding of the biological roles and applications of EV-loaded miRNAs in the kidney. We further discuss the limitations of contemporary research approaches, suggesting future directions to overcome the difficulties to advance both the basic biological understanding of miRNAs in EVs and their clinical applications in treating kidney diseases. © 2023 American Physiological Society. Compr Physiol 13:4833-4850, 2023.

Development and validation of urinary exosomal microRNA biomarkers for the diagnosis of acute rejection in kidney transplant recipients

Introduction

Acute rejection (AR) continues to be a significant obstacle for short- and long-term graft survival in kidney transplant recipients. Herein, we aimed to examine urinary exosomal microRNAs with the objective of identifying novel biomarkers of AR.

Materials and methods

Candidate microRNAs were selected using NanoString-based urinary exosomal microRNA profiling, meta-analysis of web-based, public microRNA database, and literature review. The expression levels of these selected microRNAs were measured in the urinary exosomes of 108 recipients of the discovery cohort using quantitative real-time polymerase chain reaction (qPCR). Based on the differential microRNA expressions, AR signatures were generated, and their diagnostic powers were determined by assessing the urinary exosomes of 260 recipients in an independent validation cohort.

Results

We identified 29 urinary exosomal microRNAs as candidate biomarkers of AR, of which 7 microRNAs were differentially expressed in recipients with AR, as confirmed by qPCR analysis. A three-microRNA AR signature, composed of hsa-miR-21-5p, hsa-miR-31-5p, and hsa-miR-4532, could discriminate recipients with AR from those maintaining stable graft function (area under the curve [AUC] = 0.85). This signature exhibited a fair discriminative power in the identification of AR in the validation cohort (AUC = 0.77).

Conclusion

We have successfully demonstrated that urinary exosomal microRNA signatures may form potential biomarkers for the diagnosis of AR in kidney transplantation recipients.

Proteomic analysis of urinary extracellular vesicles highlights specific signatures for patients with primary aldosteronism

Background

Urinary extracellular vesicles (uEVs) can be released by different cell types facing the urogenital tract and are involved in cellular trafficking, differentiation and survival. UEVs can be easily detected in urine and provide pathophysiological information "in vivo" without the need of a biopsy. Based on these premises, we hypothesized that uEVs proteomic profile may serve as a valuable tool in the differential characterization between Essential Hypertension (EH) and primary aldosteronism (PA).

Methods

Patients with essential hypertension (EH) and PA were enrolled in the study (EH= 12, PA=24: 11 Bilateral Primary Aldosteronism subtype (BPA) and 13 Aldosterone Producing Adenoma (APA)). Clinical and biochemical parameters were available for all the subjects. UEVs were isolated from urine by ultracentrifugation and analysed by Transmission Electron Microscopy (TEM) and nanotrack particle analysis (NTA). UEVs protein content was investigated through an untargeted MS-based approach. Statistical and network analysis was performed to identify potential candidates for the identification and classification of PA.

Results

MS analysis provided more than 300 protein identifications. Exosomal markers CD9 and CD63 were detected in all samples. Several molecules characterizing EH vs PA patients as well as BPA and APA subtypes were identified after statistical elaboration and filtering of the results. In particular, some key proteins involved in water reabsorption mechanisms, such as AQP1 and AQP2, were among the best candidates for discriminating EH vs PA, as well as A1AG1 (AGP1).

Conclusion

Through this proteomic approach, we identified uEVs molecular indicators that can improve PA characterization and help in the gain of insights of the pathophysiological features of this disease. In particular, PA was characterized by a reduction of AQP1 and AQP2 expression as compared with EH.

Epsin1-mediated exosomal sorting of Dll4 modulates the tubular-macrophage crosstalk in diabetic nephropathy

Tubular epithelial cells (TECs) play critical roles in the development of diabetic nephropathy (DN), and can activate macrophages through the secretion of exosomes. However, the mechanism(s) of TEC-exosomes in macrophage activation under DN remains unknown. By mass spectrometry, 1,644 differentially expressed proteins, especially Dll4, were detected in the urine exosomes of DN patients compared with controls, which was confirmed by western blot assay. Elevated Epsin1 and Dll4/N1ICD expression was observed in kidney tissues in both DN patients and db/db mice and was positively associated with tubulointerstitial damage. Exosomes from high glucose (HG)-treated tubular cells (HK-2) with Epsin1 knockdown (KD) ameliorated macrophage activation, TNF-α, and IL-6 expression, and tubulointerstitial damage in C57BL/6 mice in vivo. In an in vitro study, enriched Dll4 was confirmed in HK-2 cells stimulated with HG, which was captured by THP-1 cells and promoted M1 macrophage activation. In addition, Epsin1 modulated the content of Dll4 in TEC-exosomes stimulated with HG. TEC-exosomes with Epsin1-KD significantly inhibited N1ICD activation and iNOS expression in THP-1 cells compared with incubation with HG alone. These findings suggested that Epsin1 could modulate tubular-macrophage crosstalk in DN by mediating exosomal sorting of Dll4 and Notch1 activation.

An in vitro approach to understand contribution of kidney cells to human urinary extracellular vesicles

Extracellular vesicles (EV) are membranous particles secreted by all cells and found in body fluids. Established EV contents include a variety of RNA species, proteins, lipids and metabolites that are considered to reflect the physiological status of their parental cells. However, to date, little is known about cell-type enriched EV cargo in complex EV mixtures, especially in urine. To test whether EV secretion from distinct human kidney cells in culture differ and can recapitulate findings in normal urine, we comprehensively analysed EV components, (particularly miRNAs, long RNAs and protein) from conditionally immortalised human kidney cell lines (podocyte, glomerular endothelial, mesangial and proximal tubular cells) and compared to EV secreted in human urine. EV from cell culture media derived from immortalised kidney cells were isolated by hydrostatic filtration dialysis (HFD) and characterised by electron microscopy (EM), nanoparticle tracking analysis (NTA) and Western blotting (WB). RNA was isolated from EV and subjected to miRNA and RNA sequencing and proteins were profiled by tandem mass tag proteomics. Representative sets of EV miRNAs, RNAs and proteins were detected in each cell type and compared to human urinary EV isolates (uEV), EV cargo database, kidney biopsy bulk RNA sequencing and proteomics, and single-cell transcriptomics. This revealed that a high proportion of the in vitro EV signatures were also found in in vivo datasets. Thus, highlighting the robustness of our in vitro model and showing that this approach enables the dissection of cell type specific EV cargo in biofluids and the potential identification of cell-type specific EV biomarkers of kidney disease.

Proximal tubule-derived exosomes contribute to mesangial cell injury in diabetic nephropathy via miR-92a-1-5p transfer

BACKGROUND

Diabetic nephropathy (DN) is an increasing threat to human health and regarded to be the leading cause of end-stage renal disease worldwide. Exosomes delivery may play a key role in cross-talk among kidney cells and the progression of DN. However, the mechanisms underlying exosomes in DN remain unclear.

METHODS

The cross-disciplinary study, including in vivo, in vitro, and human studies was conducted to explore the cross-talk between proximal tubular epithelial cells (PTECs) and mesangial cells (MCs) in DN. We purified exosome from PTECs treated with high glucose and db/db mice and assessed their influences in the pathologic change of MCs and downstream signal pathway. Healthy individuals and type 2 diabetic patients were enrolled to examine the role of exosomes in clinical applications.

RESULTS

High glucose stimulated PTECs to secrete exosomal miR-92a-1-5p, which was taken-up by glomerular MCs, inducing myofibroblast transdifferentiation (MFT) in vitro and in vivo. PTEC-released exosomal 92a-1-5p decreased reticulocalbin-3 expression, leading to endoplasmic reticulum (ER) stress by downregulating genes essential for ER homeostasis including calreticulin and mesencephalic astrocyte-derived neurotrophic factor. Treatment with miR-92a-1-5p inhibitor ameliorated kidney damage in db/db mice with DN. Urinary miR-92a-1-5p could predict kidney injury in type 2 diabetic patients.

CONCLUSIONS

PTEC-derived exosomal miR-92a-1-5p modulated the kidney microenvironment in vivo and in vitro models, which altered ER stress and MFT in MCs resulting in DN progression. Further blocking miR-92a-1-5p epigenetic regulatory network could be a potential therapeutic strategy to prevent the progression of DN. Video Abstract.

Molecular profiling of urinary extracellular vesicles in chronic kidney disease and renal fibrosis

Chronic kidney disease (CKD) is a long-term kidney damage caused by gradual loss of essential kidney functions. A global health issue, CKD affects up to 16% of the population worldwide. Symptoms are often not apparent in the early stages, and if left untreated, CKD can progress to end-stage kidney disease (ESKD), also known as kidney failure, when the only possible treatments are dialysis and kidney transplantation. The end point of nearly all forms of CKD is kidney fibrosis, a process of unsuccessful wound-healing of kidney tissue. Detection of kidney fibrosis, therefore, often means detection of CKD. Renal biopsy remains the best test for renal scarring, despite being intrinsically limited by its invasiveness and sampling bias. Urine is a desirable source of fibrosis biomarkers as it can be easily obtained in a non-invasive way and in large volumes. Besides, urine contains biomolecules filtered through the glomeruli, mirroring the pathological state. There is, however, a problem of highly abundant urinary proteins that can mask rare disease biomarkers. Urinary extracellular vesicles (uEVs), which originate from renal cells and carry proteins, nucleic acids, and lipids, are an attractive source of potential rare CKD biomarkers. Their cargo consists of low-abundant proteins but highly concentrated in a nanosize-volume, as well as molecules too large to be filtered from plasma. Combining molecular profiling data (protein and miRNAs) of uEVs, isolated from patients affected by various forms of CKD, this review considers the possible diagnostic and prognostic value of uEVs biomarkers and their potential application in the translation of new experimental antifibrotic therapeutics.

Bibliometric analysis of scientific papers on extracellular vesicles in kidney disease published between 1999 and 2022

Background: In recent years, there has been an increasing interest in using extracellular vesicles (EVs) as potential therapeutic agents or natural drug delivery systems in kidney-related diseases. However, a detailed and targeted report on the current condition of extracellular vesicle research in kidney-related diseases is lacking. Therefore, this prospective study was designed to investigate the use of bibliometric analysis to comprehensively overview the current state of research and frontier trends on extracellular vesicle research in kidney-related diseases using visualization tools. Methods: The Web of Science Core Collection (WoSCC) database was searched to identify publications related to extracellular vesicle research in kidney-related diseases since 1999. Citespace, Microsoft Excel 2019, VOSviewer software, the R Bibliometrix Package, and an online platform were used to analyze related research trends to stratify the publication data and collaborations. Results: From 1 January 1999 to 26 June 2022, a total of 1,122 EV-related articles and reviews were published, and 6,486 authors from 1,432 institutions in 63 countries or regions investigated the role of extracellular vesicles in kidney-related diseases. We found that the number of articles on extracellular vesicles in kidney-related diseases increased every year. Dozens of publications were from China and the United States. China had the most number of related publications, in which the Southeast University (China) was the most active institution in all EV-related fields. Liu Bi-cheng published the most papers on extracellular vesicles, while Clotilde Théry had the most number of co-citations. Most papers were published by The International Journal of Molecular Sciences, while Kidney International was the most co-cited journal for extracellular vesicles. We found that exosome-related keywords included exosome, exosm, expression, extracellular vesicle, microRNA, microvesicle, and liquid biopsy, while disease- and pathological-related keywords included biomarker, microRNA, apoptosis, mechanism, systemic lupus erythematosus, EGFR, acute kidney injury, and chronic kidney disease. Acute kidney disease (AKI), CKD, SLE, exosome, liquid biopsy, and extracellular vesicle were the hotspot in extracellular vesicle and kidney-related diseases research. Conclusion: The field of extracellular vesicles in kidney-related disease research is rapidly growing, and its domain is likely to expand in the next decade. The findings from this comprehensive analysis of extracellular vesicles in kidney-related disease research could help investigators to set new diagnostic, therapeutic, and prognostic ideas or methods in kidney-related diseases.

Urinary extracellular vesicles signature for diagnosis of kidney disease

Congenital disorders characterized by the quantitative and qualitative reduction in the number of functional nephrons are the primary cause of chronic kidney disease (CKD) in children. We aimed to describe the alteration of urinary extracellular vesicles (uEVs) associated with decreased renal function during childhood. By nanoparticle tracking analysis and quantitative proteomics, we identified differentially expressed proteins in uEVs in bilateral renal hypoplasia, which is characterized by a congenitally reduced number of nephrons. This expression signature of uEVs reflected decreased renal function in CKD patients by congenital anomalies of the kidney and urinary tract or ciliopathy. As a proof-of-concept, we constructed a prototype ELISA system that enabled the isolation of uEVs and quantitation of expression of molecules representing the signature. The system identified decreased renal function even in its early stage. The uEVs signature could pave the way for non-invasive methods that can complement existing testing methods for diagnosing kidney diseases.

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Urinary extracellular vesicles (uEVs) are altered in chronic kidney disease (CKD)

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Characteristic expression signatures associated with childhood CKD are identified

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An ELISA utilizing the signature detected decreased renal function

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uEVs signature has potential in diagnosing kidney diseases

Exploring Urinary Extracellular Vesicles and Immune Mediators as Biomarkers of Kidney Injury in COVID-19 Hospitalized Patients

Kidney injury is an important outcome associated with COVID-19 severity. In this regard, alterations in urinary extracellular vesicles (uEVs) could be detected in the early phases of renal injury and may be reflective of the inflammatory process. This is an observational study performed with a case series of COVID-19 hospitalized patients presenting mild-to-critical disease. Total and podocyte-derived uEVs were identified by nanoscale flow cytometry, and urinary immune mediators were assessed by a multiplex assay. We studied 36 patients, where 24 (66.7%) were considered as mild/moderate and 12 (33.3%) as severe/critical. Increased levels of total uEVs were observed (p = 0.0001). Importantly, total uEVs were significantly higher in severe/critical patients who underwent hemodialysis (p = 0.03) and were able to predict this clinical outcome (AUC 0.93, p = 0.02). Severe/critical patients also presented elevated urinary levels (p < 0.05) of IL-1β, IL-4, IL-6, IL-7, IL-16, IL-17A, LIF, CCL-2, CCL-3, CCL-11, CXCL-10, FGFb, M-CSF, and CTAcK. Lastly, we observed that total uEVs were associated with urinary immune mediators. In conclusion, our results show that early alterations in urinary EVs could identify patients at higher risk of developing renal dysfunction in COVID-19. This could also be relevant in different scenarios of systemic and/or infectious disease.

Emerging role of extracellular vesicles in kidney diseases

Many types of renal disease eventually progress to end-stage renal disease, which can only be maintained by renal replacement therapy. Therefore, kidney diseases now contribute significantly to the health care burden in many countries. Many new advances and strategies have been found in the research involving kidney diseases; however, there is still no efficient treatment. Extracellular vesicles (EVs) are cell-derived membrane structures, which contains proteins, lipids, and nucleic acids. After internalization by downstream cells, these components can still maintain functional activity and regulate the phenotype of downstream cells. EVs drive the information exchange between cells and tissues. Majority of the cells can produce EVs; however, its production, contents, and transportation may be affected by various factors. EVs have been proved to play an important role in the occurrence, development, and treatment of renal diseases. However, the mechanism and potential applications of EVs in kidney diseases remain unclear. This review summarizes the latest research of EVs in renal diseases, and provides new therapeutic targets and strategies for renal diseases.

Urinary interleukin-9 in youth with type 1 diabetes mellitus

AIMS

Interleukin-9 (IL-9) attenuates podocyte injury in experimental kidney disease, but its role in diabetic nephropathy is unknown. We sought to relate urinary IL-9 levels to the release of podocyte-derived extracellular vesicles (EVs) in youth with type 1 diabetes. We related urinary IL-9 levels to clinical variables and studied interactions between urinary IL-9, vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) on urinary albumin/creatinine ratio (ACR) a functional measure of podocyte injury.

METHODS

We performed an analysis of urine samples and clinical data from a cohort of youth with type 1 diabetes (n = 53). Cytokines were measured using a Luminex platform (Eve Technologies), and nanoscale flow cytometry was employed to quantify urinary podocyte-derived EVs. All urinary measures were normalized to urinary creatinine.

RESULTS

Mean age was 14.7 ± 1.6 years, and the mean time from diagnosis was 6.7 ± 2.9 years. Mean HbA1c was 70.3 ± 13.9 mmol/mol, mean ACR was 1.3 ± 1.9 mg/mmol, and mean eGFR was 140.3 ± 32.6 ml/min/1.73 m². IL-9 was inversely related to podocyte EVs (r = - 0.56, p = 0.003). IL-9 was also inversely related to blood glucose, HbA1C and eGFR (r = - 0.44, p = 0.002; r = - 0.41, p = 0.003; r = - 0.49, p < 0.001, respectively) and positively correlated with systolic BP (r = 0.30, p = 0.04). There was a significant interaction between IL-9, EVs and ACR (p = 0.0143), and the relationship between IL-9 and ACR depended on VEGF (p = 0.0083), TNFα (p = 0.0231) and IL-6 levels (p = 0.0178).

CONCLUSIONS

IL-9 is associated with podocyte injury in early type 1 diabetes, and there are complex interactions between urinary IL-9, inflammatory cytokines and ACR.

The Pathophysiology of Sepsis-Associated AKI

Sepsis-associated AKI is a life-threatening complication that is associated with high morbidity and mortality in patients who are critically ill. Although it is clear early supportive interventions in sepsis reduce mortality, it is less clear that they prevent or ameliorate sepsis-associated AKI. This is likely because specific mechanisms underlying AKI attributable to sepsis are not fully understood. Understanding these mechanisms will form the foundation for the development of strategies for early diagnosis and treatment of sepsis-associated AKI. Here, we summarize recent laboratory and clinical studies, focusing on critical factors in the pathophysiology of sepsis-associated AKI: microcirculatory dysfunction, inflammation, NOD-like receptor protein 3 inflammasome, microRNAs, extracellular vesicles, autophagy and efferocytosis, inflammatory reflex pathway, vitamin D, and metabolic reprogramming. Lastly, identifying these molecular targets and defining clinical subphenotypes will permit precision approaches in the prevention and treatment of sepsis-associated AKI.

Extracellular vesicles in kidney disease

Extracellular vesicles are released by the majority of cell types and circulate in body fluids. They function as a long-distance cell-to-cell communication mechanism that modulates the gene expression profile and fate of target cells. Increasing evidence has established a central role of extracellular vesicles in kidney physiology and pathology. Urinary extracellular vesicles mediate crosstalk between glomerular and tubular cells and between different segments of the tubule, whereas circulating extracellular vesicles mediate organ crosstalk and are involved in the amplification of kidney damage and inflammation. The molecular profile of extracellular vesicles reflects the type and pathophysiological status of the originating cell so could potentially be exploited for diagnostic and prognostic purposes. In addition, robust preclinical data suggest that administration of exogenous extracellular vesicles could promote kidney regeneration and reduce inflammation and fibrosis in acute and chronic kidney diseases. Stem cells are thought to be the most promising source of extracellular vesicles with regenerative activity. Extracellular vesicles are also attractive candidates for drug delivery and various engineering strategies are being investigated to alter their cargo and increase their efficacy. However, rigorous standardization and scalable production strategies will be necessary to enable the clinical application of extracellular vesicles as potential therapeutics.

In this Review, the authors discuss the roles of extracellular vesicles in kidney physiology and disease as well as the beneficial effects of stem cell-derived extracellular vesicles in preclinical models of acute kidney injury and chronic kidney disease. They also highlight current and future clinical applications of extracellular vesicles in kidney diseases.

Urinary extracellular vesicles have roles in intra-glomerular, glomerulo-tubular and intra-tubular crosstalk, whereas circulating extracellular vesicles might mediate organ crosstalk; these mechanisms could amplify kidney damage and contribute to disease progression.

Urinary extracellular vesicles could potentially be analysed using multiplex diagnostic platforms to identify pathological processes and the originating cell types; technological advances including single extracellular vesicle analysis might increase the specificity of bulk analysis of extracellular vesicle preparations.

Robust standardization and validation in large patient cohorts are required to enable clinical application of extracellular vesicle-based biomarkers.

Stem cell-derived extracellular vesicles have been shown to improve renal recovery, limit progression of injury and reduce fibrosis in animal models of acute kidney injury and chronic kidney disease.

Various engineering approaches can be used to load extracellular vesicles with therapeutic molecules and increase their delivery to the kidney.

A small clinical trial that tested the efficacy of mesenchymal stem cell extracellular vesicle administration in patients with chronic kidney disease reported promising results; however, therapeutic application of extracellular vesicles is limited by a lack of scalable manufacturing protocols and clear criteria for standardization.

Extracellular Vesicles as an Index for Endothelial Injury and Cardiac Dysfunction in a Rodent Model of GDM

Gestational diabetes mellitus (GDM) increases risk of adverse pregnancy outcomes and maternal cardiovascular complications. It is widely believed that maternal endothelial dysfunction is a critical determinant of these risks, however, connections to maternal cardiac dysfunction and mechanisms of pathogenesis are unclear. Circulating extracellular vesicles (EVs) are emerging biomarkers that may provide insights into the pathogenesis of GDM. We examined the impact of GDM on maternal cardiac and vascular health in a rat model of diet-induced obesity-associated GDM. We observed a >3-fold increase in circulating levels of endothelial EVs (p < 0.01) and von Willebrand factor (p < 0.001) in GDM rats. A significant increase in mitochondrial DNA (mtDNA) within circulating extracellular vesicles was also observed suggesting possible mitochondrial dysfunction in the vasculature. This was supported by nicotinamide adenine dinucleotide deficiency in aortas of GDM mice. GDM was also associated with cardiac remodeling (increased LV mass) and a marked impairment in maternal diastolic function (increased isovolumetric relaxation time [IVRT], p < 0.01). Finally, we observed a strong positive correlation between endothelial EV levels and IVRT (r = 0.57, p < 0.05). In summary, we observed maternal vascular and cardiac dysfunction in rodent GDM accompanied by increased circulating endothelial EVs and EV-associated mitochondrial DNA. Our study highlights a novel method for assessment of vascular injury in GDM and highlights vascular mitochondrial injury as a possible therapeutic target.

Migrasomes: From Biogenesis, Release, Uptake, Rupture to Homeostasis and Diseases

Migrasomes are migration-dependent membrane-bound vesicular structures that contain cellular contents and small vesicles. Migrasomes grow on the tips or intersections of the retraction fibers after cells migrate away. The process of releasing migrasomes into the extracellular space is named as “migracytosis”. After releasing, they can be taken up by the surrounding cells, or rupture and further release their contents into the extracellular environment. Physiologically, migrasomes provide regional cues for organ morphogenesis during zebrafish gastrulation and discard the damaged mitochondria in response to mild mitochondrial stresses. Pathologically, migrasomes are released from podocyte during early podocyte stress and/or damage, from platelets after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), from microglia/macrophages of the ischemic brain, and from tumor necrosis factor α (TNFα)-activated endothelial cells (ECs); thus, this newly discovered extracellular vesicle is involved in all these pathological processes. Moreover, migrasomes can modulate the proliferation of cancer cell via lateral transferring mRNA and protein. In this review, we will summarize the biogenesis, release, uptake, and rupture of migrasomes and discuss its biological roles in development, redox signalling, innate immunity and COVID-19, cardio-cerebrovascular diseases, renal diseases, and cancer biology, all of these highlight the importance of migrasomes in modulating body homeostasis and diseases.

Tackling the effects of extracellular vesicles in fibrosis

Fibrosis is a physiological process of tissue repair that turns into pathological when becomes chronic, damaging the functional structure of the tissue. In this review we outline the current status of extracellular vesicles as modulators of the fibrotic process at different levels. In adipose tissue, extracellular vesicles mediate the intercellular communication not only between adipocytes, but also between adipocytes and other cells of the stromal vascular fraction. Thus, they could be altering essential processes for the functionality of adipose tissue, such as adipocyte hypertrophy/hyperplasia, tissue plasticity, adipogenesis and/or inflammation, and ultimately trigger fibrosis. This process is particularly important in obesity, and may eventually, influence the development of obesity-associated alterations. In this regard, obesity is now recognized as an independent risk factor for the development of chronic kidney disease, although the role of extracellular vesicles in this connection has not been explored so far. Nonetheless, the role of extracellular vesicles in the onset and progression of renal fibrosis has been highlighted due to the critical role of fibrosis as a common feature of kidney diseases. In fact, the content of extracellular vesicles disturbs cellular signaling cascades involved in fibrosis in virtually all types of renal cells. What is certain is that the study of extracellular vesicles is complex, as their isolation and manipulation is still difficult to reproduce, which complicates the overview of their physiopathological effects. Nevertheless, new strategies have been developed to exploit the potential of extracellular vesicles and their cargo, both as biomarkers and as therapeutic tools to prevent the progression of fibrosis towards an irreversible event.

Protein and miRNA profile of circulating extracellular vesicles in patients with primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an idiopathic and heterogenous cholestatic liver disease characterized by chronic inflammation and fibrosis of the biliary tree. Currently, no effective therapies are available for this condition, whose incidence is rising. At present, specificity and sensitivity of current serum markers used to diagnose PSC are limited and often unreliable. In this study, we characterize circulating extracellular vesicles and provide supporting data on their potential use as novel surrogate biomarkers for PSC. EVs are membrane surrounded structures, 100–1000 nm in size, released by cells under various conditions and which carry a variety of bioactive molecules, including small non-coding RNAs, lipids and proteins. In recent years, a large body of evidence has pointed to diagnostic implications of EVs and relative cargo in various human diseases. We isolated EVs from serum of well-characterized patients with PSC or control subjects by differential centrifugation and size-exclusion chromatography. A complete characterization identified elevated levels of circulating EVs in PSC patients compared to healthy control subjects (2000 vs. 500 Calcein-FITC + EVs/μL). Tissue and cell specificity of circulating EVs was assessed by identification of liver-specific markers and cholangiocyte marker CK-19. Further molecular characterization identified 282 proteins that were differentially regulated in PSC-derived compared to healthy control-EVs. Among those, IL-13Ra1 was the most significantly and differentially expressed protein in PSC-derived EVs and correlated with the degree of liver fibrosis. In addition to protein profiling, we performed a miRNA-sequencing analysis which identified 11 among established, liver-specific (e.g., miR-122 and miR-192) and novel miRNAs. One of the newly identified miRNAs, miR-4645-3p, was significantly up-regulated fourfold in PSC-derived EVs compared to circulating EVs isolated from healthy controls. This study provides supporting evidence of the potential role of circulating EVs and associated protein and miRNA cargo as surrogate noninvasive and reliable biomarker for PSC.

Benchmarking a Microfluidic-Based Filtration for Isolating Biological Particles

Isolating particles from complex fluids is a crucial approach in multiple fields including biomedicine. In particular, biological matrices contain a myriad of distinct particles with different sizes and structures. Extracellular vesicles (EVs), for instance, are nanosized particles carrying vital information from donor to recipient cells, and they have garnered significant impact on disease diagnostics, drug delivery, and theranostics applications. Among all the EV types, exosome particles are one of the smallest entities, sizing from 30 to 100 nm. Separating such small substances from a complex media such as tissue culture and serum is still one of the most challenging steps in this field. Membrane filtration is one of the convenient approaches for these operations; yet clogging, low-recovery, and high fouling are still major obstacles. In this study, we design a two-filter-integrated microfluidic device focusing on dead-end and cross-flow processes at the same time, thereby minimizing any interfering factors on the recovery. The design of this platform is also numerically assessed to understand pressure-drop and flow rate effects over the procedure. As a model, we isolate exosome particles from human embryonic kidney cells cultured in different conditions, which also mimic complex fluids such as serum. Moreover, by altering the flow direction, we refresh the membranes for minimizing clogging issues and benchmark the platform performance for multitime use. By comprehensively analyzing the design and operation parameters of this platform, we address the aforementioned existing barriers in the recovery, clogging, and fouling factors, thereby achieving the use of a microfluidic device multiple times for bio-nanoparticle isolation without any notable issues.

Altered DNA methylation in kidney disease: useful markers and therapeutic targets

Recent studies have demonstrated the association of altered epigenomes with lifestyle-related diseases. Epigenetic regulation promotes biological plasticity in response to environmental changes, and such plasticity may cause a ‘memory effect’, a sustained effect of transient treatment or an insult in the course of lifestyle-related diseases. We investigated the significance of epigenetic changes in several genes required for renal integrity, including the nephrin gene in podocytes, and the sustained anti-proteinuric effect, focusing on the transcription factor Krüppel-like factor 4 (KLF4). We further reported the role of the DNA repair factor lysine-acetyl transferase 5 (KAT5), which acts coordinately with KLF4, in podocyte injury caused by a hyperglycemic state through the acceleration of DNA damage and epigenetic alteration. In contrast, KAT5 in proximal tubular cells prevents acute kidney injury via glomerular filtration regulation by an epigenetic mechanism as well as promotion of DNA repair, indicating the cell type-specific action and roles of DNA repair factors. This review summarizes epigenetic alterations in kidney diseases, especially DNA methylation, and their utility as markers and potential therapeutic targets. Focusing on transcription factors or DNA damage repair factors associated with epigenetic changes may be meaningful due to their cell-specific expression or action. We believe that a better understanding of epigenetic alterations in the kidney will lead to the development of a novel strategy for chronic kidney disease (CKD) treatment.

Exosome Biogenesis and Lysosome Function Determine Podocyte Exosome Release and Glomerular Inflammatory Response during Hyperhomocysteinemia

Nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation in podocytes is reportedly associated with enhanced release of exosomes containing NLRP3 inflammasome products from these cells during hyperhomocysteinemia (hHcy). This study examined the possible role of increased exosome secretion during podocyte NLRP3 inflammasome activation in the glomerular inflammatory response. Whether exosome biogenesis and lysosome function are involved in the regulation of exosome release from podocytes during hHcy in mice and upon stimulation of homocysteine (Hcy) in podocytes was tested. By nanoparticle tracking analysis, treatments of mice with amitriptyline (acid sphingomyelinase inhibitor), GW4869 (exosome biogenesis inhibitor), and rapamycin (lysosome function enhancer) were found to inhibit elevated urinary exosomes during hHcy. By examining NLRP3 inflammasome activation in glomeruli during hHcy, amitriptyline (but not GW4869 and rapamycin) was shown to have an inhibitory effect. However, all treatments attenuated glomerular inflammation and injury during hHcy. In cell studies, Hcy treatment stimulated exosome release from podocytes, which was prevented by amitriptyline, GW4869, and rapamycin. Structured illumination microscopy revealed that Hcy inhibited lysosome-multivesicular body interactions in podocytes, which was prevented by amitriptyline or rapamycin but not GW4869. Thus, the data from this study shows that activation of exosome biogenesis and dysregulated lysosome function are critically implicated in the enhancement of exosome release from podocytes leading to glomerular inflammation and injury during hHcy.

Isolation and Characterization of Urinary Extracellular Vesicles for MicroRNA Biomarker Signature Development with Reference to MISEV Compliance

Urine bears high potential for serving as biomarker repository for renal and urinary tract associated disorders. Besides various metabolites and salts, urine carries extracellular vesicles (EVs)-a heterogeneous group of cell-derived mediators comprising proteins, lipids, and nucleic acids such as microRNAs (miRNAs). Particularly, EV-derived miRNA biomarkers have already been identified for numerous disorders such as sepsis, various blood and solid cancer entities, respiratory and renal diseases. However, study results are often incomparable due to poorly reported EV separation and miRNA isolation protocols and emphasize the need for standardization and reproducibility. To ensure valid EV-derived miRNA biomarker findings from urine, a step-by-step protocol compliant with the "Minimal Information for Studies of Extracellular Vesicles" (MISEV) is outlined in the following paragraphs. Actually, an immunoaffinity-based EV separation method followed by EV characterization, quantification, and normalization, as well as consecutive miRNA isolation and miRNA profiling by small RNA sequencing, are described.

Autocrine Exosomal Fibulin-1 as a Target of MiR-1269b Induces Epithelial–Mesenchymal Transition in Proximal Tubule in Diabetic Nephropathy

Background: Diabetic nephropathy (DN) is an increasing threat to human health and is regarded to be the leading cause of end-stage renal disease worldwide. Exosomes deliver biomolecule massages and may play a key role in cell communication and the progression of DN.

Methods: A cross-disciplinary study, including in vivo, in vitro, and human studies, was conducted to explore the cross-talk within proximal tubular epithelial cells (PTECs) in DN. Exosomal protein from PTECs treated with high glucose (HG) was purified and examined using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Next-generation sequencing (NGS) was utilized to analyze RNAs extracted from PTECs from a type 2 diabetic patient and a normal individual. HK-2 cells were used to assess exosomal protein and its modulation and biofunction in DN. Normal individuals and type 2 diabetic patients were enrolled, and nondiabetic db/m mice and diabetic db/db mice were used to validate the molecular mechanism of exosomes in DN.

Results: HG stimulated PTECs to increase Fibulin-1 (FBLN1) expression, and PTECs secreted FBLN1 through exosome delivery, thereby inducing epithelial–mesenchymal transition (EMT) in PTECs. Transcriptome analysis found that FBLN1 expression was modulated by miR-1269b, which was downregulated by HG in HK-2 cells. While transfection of miR-1269b reversed FBLN1-mediated EMT in PTECs, miR-1269b inhibitor modulated the phenotype of PTECs toward mesenchymal type under normal glucose (NG) condition. Most importantly, urinary FBLN1 and exosomal miR-1269b levels were correlated with the severity of kidney injury in type 2 diabetic patients.

Conclusion: This study demonstrated the communication within PTECs through exosome transmission in an autocrine pattern. MiR-1269b–FBLN1 epigenetic regulatory network could be a potential therapeutic strategy to prevent the progression of DN.

Promising diagnostic biomarkers of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis: From clinical proteomics to microbiome

Fatty liver has been present in the lives of patients and physicians for almost two centuries. Vast knowledge has been generated regarding its etiology and consequences, although a long path seeking novel and innovative diagnostic biomarkers for nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) is still envisioned. On the one hand, proteomics and lipidomics have emerged as potential noninvasive resources for NAFLD diagnosis. In contrast, metabolomics has been able to distinguish between NAFLD and NASH, even detecting degrees of fibrosis. On the other hand, genetic and epigenetic markers have been useful in monitoring disease progression, eventually functioning as target therapies. Other markers involved in immune dysregulation, oxidative stress, and inflammation are involved in the instauration and evolution of the disease. Finally, the fascinating gut microbiome is significantly involved in NAFLD and NASH. This review presents state-of-the-art biomarkers related to NAFLD and NASH and new promises that could eventually be positioned as diagnostic resources for this disease. As is evident, despite great advances in studying these biomarkers, there is still a long path before they translate into clinical benefits.

Promising diagnostic biomarkers of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis: From clinical proteomics to microbiome

Fatty liver has been present in the lives of patients and physicians for almost two centuries. Vast knowledge has been generated regarding its etiology and consequences, although a long path seeking novel and innovative diagnostic biomarkers for nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) is still envisioned. On the one hand, proteomics and lipidomics have emerged as potential noninvasive resources for NAFLD diagnosis. In contrast, metabolomics has been able to distinguish between NAFLD and NASH, even detecting degrees of fibrosis. On the other hand, genetic and epigenetic markers have been useful in monitoring disease progression, eventually functioning as target therapies. Other markers involved in immune dysregulation, oxidative stress, and inflammation are involved in the instauration and evolution of the disease. Finally, the fascinating gut microbiome is significantly involved in NAFLD and NASH. This review presents state-of-the-art biomarkers related to NAFLD and NASH and new promises that could eventually be positioned as diagnostic resources for this disease. As is evident, despite great advances in studying these biomarkers, there is still a long path before they translate into clinical benefits.

Single Extracellular Vesicle Analysis Performed by Imaging Flow Cytometry and Nanoparticle Tracking Analysis Evaluate the Accuracy of Urinary Extracellular Vesicle Preparation Techniques Differently

Small extracellular vesicles isolated from urine (uEVs) are increasingly recognized as potential biomarkers. Meanwhile, different uEV preparation strategies exist. Conventionally, the performance of EV preparation methods is evaluated by single particle quantification, Western blot, and electron microscopy. Recently, we introduced imaging flow cytometry (IFCM) as a next-generation single EV analysis technology. Here, we analyzed uEV samples obtained with different preparation procedures using nanoparticle tracking analysis (NTA), semiquantitative Western blot, and IFCM. IFCM analyses demonstrated that urine contains a predominant CD9⁺ sEV population, which exceeds CD63⁺ and CD81⁺ sEV populations. Furthermore, we demonstrated that the storage temperature of urine samples negatively affects the recovery of CD9⁺ sEVs. Although overall reduced, the highest CD9⁺ sEV recovery was obtained from urine samples stored at −80 °C and the lowest from those stored at −20 °C. Upon comparing the yield of the different uEV preparations, incongruencies between NTA and IFCM data became apparent. Results obtained by both NTA and IFCM were consistent with Western blot analyses for EV marker proteins; however, NTA results correlated with the amount of the impurity marker uromodulin. Despite demonstrating that the combination of ultrafiltration and size exclusion chromatography appears as a reliable uEV preparation technique, our data challenge the soundness of traditional NTA for the evaluation of different EV preparation methods.

The Past, the Present, and the Future of the Size Exclusion Chromatography in Extracellular Vesicles Separation

Extracellular vesicles (EVs) are cell-derived membranous particles secreted by all cell types (including virus infected and uninfected cells) into the extracellular milieu. EVs carry, protect, and transport a wide array of bioactive cargoes to recipient/target cells. EVs regulate physiological and pathophysiological processes in recipient cells and are important in therapeutics/drug delivery. Despite these great attributes of EVs, an efficient protocol for EV separation from biofluids is lacking. Numerous techniques have been adapted for the separation of EVs with size exclusion chromatography (SEC)-based methods being the most promising. Here, we review the SEC protocols used for EV separation, and discuss opportunities for significant improvements, such as the development of novel particle purification liquid chromatography (PPLC) system capable of tandem purification and characterization of biological and synthetic particles with near-single vesicle resolution. Finally, we identify future perspectives and current issues to make PPLC a tool capable of providing a unified, automated, adaptable, yet simple and affordable particle separation resource.

Nanoparticle-Enabled Multiplexed Electrochemical Immunoassay for Detection of Surface Proteins on Extracellular Vesicles

Extracellular vesicles (EVs) are lipid bilayer particles secreted from various cells. EVs carry molecular information of parent cells and hold considerable promise for early disease diagnostics. This paper describes a general strategy for multiplexed immunosensing of EV surface proteins, focusing on surface markers CD63, CD81, nephrin, and podocin to prove the concept. This sensing strategy entailed functionalizing gold nanoparticles (AuNPs) with two types of antibodies and then tagging with metal ions, either Pb2+ or Cu2+. The metal ions served as redox reporters, generating unique redox peaks at -0.23 and 0.28 V (vs Ag/AgCl) during electrochemical oxidation of Pb2+ and Cu2+, respectively. Capture of EVs on the working electrode, followed by labeling with immunoprobes and square wave voltammetry, produced redox currents proportional to concentrations of EVs and levels of expression of EV surface markers. Importantly, metal-ion tagging of immunoprobes enabled detection of two EV surface markers simultaneously from the same electrode. We demonstrated dual detection of either CD63/CD81 or podocin/nephrin surface markers from urinary EVs. The NP-enabled immunoassay had a sensitivity of 2.46 × 105 particles/mL (or 40.3 pg/mL) for CD63- and 5.80 × 105 particles/mL (or 47.7 pg/mL) for CD81-expressing EVs and a linear range of four orders of magnitude. The limit of detection for podocin and nephrin was 3.1 and 3.8 pg/mL, respectively. In the future, the capacity for multiplexing may be increased by extending the repertoire of metal ions used for redox tagging of AuNPs.

Extracellular Vesicles and Their Relationship with the Heart-Kidney Axis, Uremia and Peritoneal Dialysis

Cardiorenal syndrome (CRS) is described as primary dysfunction in the heart culminating in renal injury or vice versa. CRS can be classified into five groups, and uremic toxin (UT) accumulation is observed in all types of CRS. Protein-bound uremic toxin (PBUT) accumulation is responsible for permanent damage to the renal tissue, and mainly occurs in CRS types 3 and 4, thus compromising renal function directly leading to a reduction in the glomerular filtration rate (GFR) and/or subsequent proteinuria. With this decrease in GFR, patients may need renal replacement therapy (RRT), such as peritoneal dialysis (PD). PD is a high-quality and home-based dialysis therapy for patients with end-stage renal disease (ESRD) and is based on the semi-permeable characteristics of the peritoneum. These patients are exposed to factors which may cause several modifications on the peritoneal membrane. The presence of UT may harm the peritoneum membrane, which in turn can lead to the formation of extracellular vesicles (EVs). EVs are released by almost all cell types and contain lipids, nucleic acids, metabolites, membrane proteins, and cytosolic components from their cell origin. Our research group previously demonstrated that the EVs can be related to endothelial dysfunction and are formed when UTs are in contact with the endothelial monolayer. In this scenario, this review explores the mechanisms of EV formation in CRS, uremia, the peritoneum, and as potential biomarkers in peritoneal dialysis.

Higher Urine Exosomal miR-193a Is Associated With a Higher Probability of Primary Focal Segmental Glomerulosclerosis and an Increased Risk of Poor Prognosis Among Children With Nephrotic Syndrome

Background: In children, focal segmental glomerulosclerosis (FSGS) is one of the most common primary glomerular diseases leading to end-stage renal disease. Exosomes facilitate communication between cells by transporting proteins and microRNAs. We aimed to investigate the utility of urine exosomal miR-193a for diagnosis and prognosis estimation among patients with primary FSGS, and preliminarily explore the regulation mechanism of exosome secretion from podocytes.

Methods: Specimens of urine were obtained from patients with primary FSGS, minimal change nephropathy (MCN) and IgA nephropathy (IgAN), followed by exosome isolation. We quantified urine exosomal miR-193a based on quantitative reverse transcription-polymerase chain reaction, and evaluated its applicability using area-under-receiver-operating-characteristics curves (AUROCs). The semiquantitative glomerulosclerosis index (GSI) was used to evaluate the degree of glomerulosclerosis according to the method of Raij et al. We further used FAM-labeled miR-193a-5p to examine exosome shuttling using confocal microscopy for visualization, and explored the regulation mechanism of exosomes release from podocytes using Fluo-3AM dye.

Results: Urine exosomal miR-193a levels were significantly higher in patients with primary FSGS than those with MCN and IgAN. The AUROCs for discriminating between primary FSGS and MCN or IgAN were 0.85 and 0.821, respectively. Urine exosomal miR-193a levels positively correlated with GSI in patients with primary FSGS. We further found that kidney tissues from these patients had increased CD63 expression involving podocytes in non-sclerotic tufts. Exosomes from cultured podocytes could transport miR-193a-5p to recipient cells, potentially through a calcium-dependent release mechanism.

Conclusion: Urine exosomal miR-193a might be harnessed as a non-invasive marker for diagnosis and outcome assessment among patients with primary FSGS. Exosomes were potential vehicles for miRNAs shuttling between podocytes, and released from podocytes in a calcium-dependent manner.

Urinary extracellular vesicles: Assessment of pre-analytical variables and development of a quality control with focus on transcriptomic biomarker research

Urinary extracellular vesicles (uEV) are a topical source of non-invasive biomarkers for health and diseases of the urogenital system. However, several challenges have become evident in the standardization of uEV pipelines from collection of urine to biomarker analysis. Here, we studied the effect of pre-analytical variables and developed means of quality control for uEV isolates to be used in transcriptomic biomarker research. We included urine samples from healthy controls and individuals with type 1 or type 2 diabetes and normo-, micro- or macroalbuminuria and isolated uEV by ultracentrifugation. We studied the effect of storage temperature (-20°C vs. -80°C), time (up to 4 years) and storage format (urine or isolated uEV) on quality of uEV by nanoparticle tracking analysis, electron microscopy, Western blotting and qPCR. Urinary EV RNA was compared in terms of quantity, quality, and by mRNA or miRNA sequencing. To study the stability of miRNA levels in samples isolated by different methods, we created and tested a list of miRNAs commonly enriched in uEV isolates. uEV and their transcriptome were preserved in urine or as isolated uEV even after long-term storage at -80°C. However, storage at -20°C degraded particularly the GC-rich part of the transcriptome and EV protein markers. Transcriptome was preserved in RNA samples extracted with and without DNAse, but read distributions still showed some differences in e.g. intergenic and intronic reads. MiRNAs commonly enriched in uEV isolates were stable and concordant between different EV isolation methods. Analysis of never frozen uEV helped to identify surface characteristics of particles by EM. In addition to uEV, qPCR assays demonstrated that uEV isolates commonly contained polyoma viruses. Based on our results, we present recommendations how to store and handle uEV isolates for transcriptomics studies that may help to expedite standardization of the EV biomarker field.

Targeting the microRNAs in exosome: A potential therapeutic strategy for alleviation of diabetes-related cardiovascular complication

Diabetes-related cardiovascular disease (CVD) is a global health issue that causes thousands of people's death around the world annually. Diabetes-related CVD is still prevailing despite the progression being made in its diagnosis and treatment. Therefore it is urgent to find therapeutic strategies.to prevent it. MicroRNA (miRNA) is a single-stranded non-coding RNA involved in the process of post-transcriptional control of gene expression in eukaryotes. A large number of literatures reveal that miRNAs are implicated in diabetes-related CVD. The increase of miRNAs in exosomes may promote the occurrence and development of diabetes-related cardiovascular complication. However, some other studies identify that miRNAs in exosomes are supposed to be involved in cardiac regeneration and confer cardiac protection effect. Therefore, targeting the miRNA in exosome is regarded as a potent therapeutic measure to alleviate diabetes-related CVD. In this article, we review current knowledge about the role of exosomal miRNAs in diabetes-related cardiovascular complication, such as coronary heart disease, Peripheral artery disease, stroke, diabetic cardiomyopathy, diabetic nephropathy and diabetic retinopathy. Exosomal miRNAs are considered to be central regulators of diabetes-Related CVD and provide a therapeutic tool for diagnosis and treatment of diabetes-related cardiovascular complication.

Large-Scale Proteomic Assessment of Urinary Extracellular Vesicles Highlights Their Reliability in Reflecting Protein Changes in the Kidney

BACKGROUND

Urinary extracellular vesicles (uEVs) are secreted into urine by cells from the kidneys and urinary tract. Although changes in uEV proteins are used for quantitative assessment of protein levels in the kidney or biomarker discovery, whether they faithfully reflect (patho)physiologic changes in the kidney is a matter of debate.

METHODS

Mass spectrometry was used to compare in an unbiased manner the correlations between protein levels in uEVs and kidney tissue from the same animal. Studies were performed on rats fed a normal or high K⁺ diet.

RESULTS

Absolute quantification determined a positive correlation (Pearson R=0.46 or 0.45, control or high K⁺ respectively, P<0.0001) between the approximately 1000 proteins identified in uEVs and corresponding kidney tissue. Transmembrane proteins had greater positive correlations relative to cytoplasmic proteins. Proteins with high correlations (R>0.9), included exosome markers Tsg101 and Alix. Relative quantification highlighted a monotonic relationship between altered transporter/channel abundances in uEVs and the kidney after dietary K⁺ manipulation. Analysis of genetic mouse models also revealed correlations between uEVs and kidney.

CONCLUSION

This large-scale unbiased analysis identifies uEV proteins that track the abundance of the parent proteins in the kidney. The data form a novel resource for the kidney community and support the reliability of using uEV protein changes to monitor specific physiologic responses and disease mechanisms.

Podocyte Sphingolipid Signaling in Nephrotic Syndrome

Podocytes play a vital role in the pathogenesis of nephrotic syndrome (NS), which is clinically characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and peripheral edema. The pathogenesis of NS has evolved through several hypotheses ranging from immune dysregulation theory and increased glomerular permeability theory to the current concept of podocytopathy. Podocytopathy is characterized by dysfunction or depletion of podocytes, which may be caused by unknown permeability factor, genetic disorders, drugs, infections, systemic disorders, and hyperfiltration. Over the last two decades, numerous studies have been done to explore the molecular mechanisms of podocyte injuries or NS and to develop the novel therapeutic strategies targeting podocytopathy for treatment of NS. Recent studies have shown that normal sphingolipid metabolism is essential for structural and functional integrity of podocytes. As a basic component of the plasma membrane, sphingolipids not only support the assembly of signaling molecules and interaction of receptors and effectors, but also mediate various cellular activities, such as apoptosis, proliferation, stress responses, necrosis, inflammation, autophagy, senescence, and differentiation. This review briefly summarizes current evidence demonstrating the regulation of sphingolipid metabolism in podocytes and the canonical or noncanonical roles of podocyte sphingolipid signaling in the pathogenesis of NS and associated therapeutic strategies.

Extracellular Vesicles in Acute Kidney Injury and Clinical Applications

Acute kidney injury (AKI)––the sudden loss of kidney function due to tissue damage and subsequent progression to chronic kidney disease––has high morbidity and mortality rates and is a serious worldwide clinical problem. Current AKI diagnosis, which relies on measuring serum creatinine levels and urine output, cannot sensitively and promptly report on the state of damage. To address the shortcomings of these traditional diagnosis tools, several molecular biomarkers have been developed to facilitate the identification and ensuing monitoring of AKI. Nanosized membrane-bound extracellular vesicles (EVs) in body fluids have emerged as excellent sources for discovering such biomarkers. Besides this diagnostic purpose, EVs are also being extensively exploited to deliver therapeutic macromolecules to damaged kidney cells to ameliorate AKI. Consequently, many successful AKI biomarker findings and therapeutic applications based on EVs have been made. Here, we review our understanding of how EVs can help with the early identification and accurate monitoring of AKI and be used therapeutically. We will further discuss where current EV-based AKI diagnosis and therapeutic applications fall short and where future innovations could lead us.

Apoptotic microparticles mediate the association between bisphenol A and subclinical atherosclerosis in a young population: A population-based study

Bisphenol A (BPA) exposure is associated with atherosclerotic cardiovascular diseases. The interactions between BPA, extracellular microparticles (MPs), and atherosclerosis are unknown. A total of 103,756 young students participated in the mass urine-screening program in Taiwan between 1992 and 2000 were analyzed. After exclusion, 886 subjects were recruited to test the relationships between serum level of BPA, endothelial and platelet MPs as well as subclinical atherosclerosis represented by carotid artery intima-media thickness (CIMT). We found that an increment of one unit of log-BPA could lead to significant association between thicker CIMT and concentrations of endothelial microparticles and platelet microparticles in the cohort (odds ratio (OR) 1.23, P < 0.001). CD31 + /CD42a- (> 50%, OR 1.229, P = 0.001) and CD31 + /CD42a+ (≦ 50%, OR 1.262, P = 0.017 and > 50%, OR 1.212, P = 0.006) were significantly associated with thicker CIMT in the presence of elevated BPA. When considering the interactions between CD31 + /CD42a- and CD31 + /CD42a+ , we observed increased OR as CD31 + /CD42a- was greater than 50% (CD31 +/CD42a- > 50% and CD31 +/CD42a+ ≦ 50%, OR 1.356, P = 0.029; CD31 +/CD42a- > 50% and CD31 +/CD42a+ > 50%, OR 1.204, P = 0.014). Our study identified a higher risk of thicker CIMT associated with altered MPs in the presence of elevated BPA levels. BPA exposure is associated with endothelial dysfunction and subclinical atherosclerosis in a young population.

Urinary small extracellular vesicles derived CCL21 mRNA as biomarker linked with pathogenesis for diabetic nephropathy

Background

Diabetic nephropathy (DN) is a leading cause of renal failure, whereas the effective and early diagnostic biomarkers are still lacking.

Methods

Fourteen cytokines and chemokines mRNA were detected in urinary extracellular vesicles (EVs) from the screening cohort including 4 healthy controls (HC), 4 diabetes mellitus (DM) and 4 biopsy-proven DN patients, and was validated in another 16 HC and 15 DM and 28 DN patients. Correlation analysis was performed between the candidate biomarkers and clinic parameters as well as kidney histological changes. The findings were also confirmed in DN rat model with single injection of STZ.

Results

The number of small EVs secreted in urine was increased in DN patients compared to DM patients and healthy controls, with expression of AQP1 (a marker of proximal tubules) and AQP2 (a marker of distal/collecting tubules). Small EVs derived CCL21 mRNA increased significantly in DN patients and correlated with level of proteinuria and eGFR. Interestingly, elevated CCL21 mRNA from urine small EVs was observed in DN patients with normal renal function and could discriminate early DN patients from DM more efficiently compared to eGFR and proteinuria. CCL21 also showed an accurate diagnostic ability in distinguishing incipient from overt DN. Histologically, CCL21 mRNA expression increased progressively with the deterioration of tubulointerstitial inflammation and showed the highest level in nodular sclerosis group (class III) in DN patients. Remarkable infiltration of CD3 positive T cells including both CD4 and CD8 positive T cell population were observed in DN patients with high-CCL21 expression. Besides, accumulation of CD3 positive T cells correlated with level of urinary small EVs derived CCL21 and co-localized with CCL21 in the tubulointerstitium in DN patients. Finally, the correlation of CCL21 expression in renal cortex and urinary small EVs was confirmed in STZ-induced DN rat model.

Conclusions

Urinary small EVs derived CCL21 mRNA may serve as early biomarker for identifying DN linked with pathogenesis. CCL21 mRNA mediated T cell infiltration may constitute the key mechanism of chronic inflammation in DN.

Urinary exosomal microRNA profiling in type 2 diabetes patients taking dipeptidyl peptidase-4 inhibitor compared with sulfonylurea

Background

Dipeptidyl peptidase-4 (DPP-4) inhibitor has been reported to have kidney-protective benefits. To elucidate how antidiabetic agents prevent diabetic kidney disease progression, it is important to investigate their effect on the kidney environment in type 2 diabetes mellitus (DM) patients. Herein, we investigated the expression pattern of urinary exosome-derived microRNA (miRNA) in patients taking a combination of DPP-4 inhibitor and metformin (DPP-4 inhibitor group) and compared them with patients taking a combination of sulfonylurea and metformin (sulfonylurea group).

Methods

This was a prospective study involving 57 patients with type 2 DM (DPP-4 inhibitor group, n = 34; sulfonylurea group, n = 23) and healthy volunteers (n = 7). We measured urinary exosomal miRNA using the NanoString nCounter miRNA array (NanoString Technologies) across the three groups (n = 4 per each group) and validated findings using real-time polymerase chain reaction.

Results

Twenty-one differentially expressed candidate miRNAs were identified, and six (let-7c-5p, miR-23a-3p, miR-26a-3p, miR-30d, miR-205, and miR-200a) were selected for validation. Validation showed no significant difference in miRNA expression between the DPP-4 inhibitor and sulfonylurea groups. Only miR-23a-3p was significantly overexpressed in the diabetes group compared with the control group (DPP-4 inhibitor vs. control, p = 0.01; sulfonylurea vs. control, p = 0.007). This trend was consistent even after adjusting for age, sex, and body mass index.

Conclusion

There was no significant difference in urine exosome miRNA expression between diabetic participants taking DPP-4 inhibitor and those taking sulfonylurea. The miR-23a levels were higher in diabetic participants than in nondiabetic controls.

Podocyte-derived microparticles in IgA nephropathy

Microparticles are a general term for different types of cell plasma membrane-originated vesicles that are released into the extracellular environment. The paracrine action of these nano-sized vesicles is crucial for intercellular communications through the transfer of diverse lipids, cytosolic proteins, RNA as well as microRNAs. The progression of different diseases influences the composition, occurrence, and functions of these cell-derived particles. Podocyte injury has been shown to have an important role in the pathophysiology of many glomerular diseases including IgA nephropathy (IgAN). This review would focus on the possible potential of podocyte-derived microparticles detected in urine to be used as a diagnostic tool in IgAN.