Urinary exosomes: a novel means to non-invasively assess changes in renal gene and protein expression

Control of interface functions in solid-state biosensors for stable detection of molecular recognition

Significant progress has been achieved in the field of solid-state biosensors over the past 50 years. Various sensing devices with high-density integration and flexible configuration, as well as new applications for clinical diagnosis and healthcare, have been developed using blood, serum, and other body fluids such as sweat, tears, and saliva. A high-density array of ion-sensitive field effect transistors was developed by exploiting the advantages of advanced semiconductor technologies and commercialized in combination with an enzymatic primer extension reaction as a DNA sequencer in 2011. Different types of materials such as inorganic materials, metals, polymers, and biomolecules are mixed together on the surface of the gate while maintaining their own functions; therefore, compatibility among different materials has to be optimized so that the best detection performance of solid-state biosensors, including stability and reliability, is achieved as designed. Solid-state biosensors are suitable for the rapid, cost-effective, and noninvasive identification of biomarkers at various timepoints over the course of a disease.

Unraveling the Multifaceted Roles of Extracellular Vesicles: Insights into Biology, Pharmacology, and Pharmaceutical Applications for Drug Delivery

Extracellular vesicles (EVs) are nanoparticles released from various cell types that have emerged as powerful new therapeutic option for a variety of diseases. EVs are involved in the transmission of biological signals between cells and in the regulation of a variety of biological processes, highlighting them as potential novel targets/platforms for therapeutics intervention and/or delivery. Therefore, it is necessary to investigate new aspects of EVs' biogenesis, biodistribution, metabolism, and excretion as well as safety/compatibility of both unmodified and engineered EVs upon administration in different pharmaceutical dosage forms and delivery systems. In this review, we summarize the current knowledge of essential physiological and pathological roles of EVs in different organs and organ systems. We provide an overview regarding application of EVs as therapeutic targets, therapeutics, and drug delivery platforms. We also explore various approaches implemented over the years to improve the dosage of specific EV products for different administration routes.

Heat shock protein A2 is a novel extracellular vesicle-associated protein

70-kDa Heat Shock Proteins (HSPA/HSP70) are chaperones playing a central role in the proteostasis control mechanisms. Their basal expression can be highly elevated as an adaptive response to environmental and pathophysiological stress conditions. HSPA2, one of poorly characterised chaperones of the HSPA/HSP70 family, has recently emerged as epithelial cells differentiation-related factor. It is also commonly expressed in cancer cells, where its functional significance remains unclear. Previously, we have found that proteotoxic stress provokes a decrease in HSPA2 levels in cancer cells. In the present study we found that proteasome inhibition-related loss of HSPA2 from cancer cells neither is related to a block in the gene transcription nor does it relate to increased autophagy-mediated disposals of the protein. Proteotoxic stress stimulated extracellular release of HSPA2 in extracellular vesicles (EVs). Interestingly, EVs containing HSPA2 are also released by non-stressed cancer and normal cells. In human urinary EVs levels of HSPA2 were correlated with the levels of TSG101, one of the main EVs markers. We conclude that HSPA2 may constitute basic components of EVs. Nevertheless, its specific role in EVs and cell-to-cell communication requires further investigation.

Exosomes: A potential tool for immunotherapy of ovarian cancer

Ovarian cancer is a malignant tumor of the female reproductive system, with a very poor prognosis and high mortality rates. Chemotherapy and radiotherapy are the most common treatments for ovarian cancer, with unsatisfactory results. Exosomes are a subpopulation of extracellular vesicles, which have a diameter of approximately 30-100 nm and are secreted by many different types of cells in various body fluids. Exosomes are highly stable and are effective carriers of immunotherapeutic drugs. Recent studies have shown that exosomes are involved in various cellular responses in the tumor microenvironment, influencing the development and therapeutic efficacy of ovarian cancer, and exhibiting dual roles in inhibiting and promoting tumor development. Exosomes also contain a variety of genes related to ovarian cancer immunotherapy that could be potential biomarkers for ovarian cancer diagnosis and prognosis. Undoubtedly, exosomes have great therapeutic potential in the field of ovarian cancer immunotherapy. However, translation of this idea to the clinic has not occurred. Therefore, it is important to understand how exosomes could be used in ovarian cancer immunotherapy to regulate tumor progression. In this review, we summarize the biomarkers of exosomes in different body fluids related to immunotherapy in ovarian cancer and the potential mechanisms by which exosomes influence immunotherapeutic response. We also discuss the prospects for clinical application of exosome-based immunotherapy in ovarian cancer.

Impaired autophagic flux and dedifferentiation in podocytes lacking Asah1 gene: Role of lysosomal TRPML1 channel

Podocytopathy and associated nephrotic syndrome have been reported in a mouse strain (Asah1fl/fl/Podocre) with a podocyte-specific deletion of α subunit (the main catalytic subunit) of acid ceramidase (Ac). However, the pathogenesis of podocytopathy in these mice remains unclear. The present study tested whether Ac deficiency impairs autophagic flux in podocytes through blockade of transient receptor potential mucolipin 1 (TRPML1) channel as a potential pathogenic mechanism of podocytopathy in Asah1fl/fl/Podocre mice. We first demonstrated that impairment of autophagic flux occurred in podocytes lacking Asah1 gene, which was evidenced by autophagosome accumulation and reduced lysosome-autophagosome interaction. TRPML1 channel agonists recovered lysosome-autophagosome interaction and attenuated autophagosome accumulation in podocytes from Asah1fl/fl/Podocre mice, while TRPML1 channel inhibitors impaired autophagic flux in WT/WT podocytes and worsened autophagic deficiency in podocytes lacking Asah1 gene. The effects of TRPML1 channel agonist were blocked by dynein inhibitors, indicating a critical role of dynein activity in the control of lysosome movement due to TRPML1 channel-mediated Ca2+ release. It was also found that there is an enhanced phenotypic transition to dedifferentiation status in podocytes lacking Asah1 gene in vitro and in vivo. Such podocyte phenotypic transition was inhibited by TRPML1 channel agonists but enhanced by TRPML1 channel inhibitors. Moreover, we found that TRPML1 gene silencing induced autophagosome accumulation and dedifferentiation in podocytes. Based on these results, we conclude that Ac activity is essential for autophagic flux and maintenance of differentiated status of podocytes. Dysfunction or deficiency of Ac may impair autophagic flux and induce podocyte dedifferentiation, which may be an important pathogenic mechanism of podocytopathy and associated nephrotic syndrome.

Urinary Exosomal Cystatin C and Lipopolysaccharide Binding Protein as Biomarkers for Antibody−Mediated Rejection after Kidney Transplantation

We aimed to discover and validate urinary exosomal proteins as biomarkers for antibody−mediated rejection (ABMR) after kidney transplantation. Urine and for-cause biopsy samples from kidney transplant recipients were collected and categorized into the discovery cohort (n = 36) and a validation cohort (n = 65). Exosomes were isolated by stepwise ultra-centrifugation for proteomic analysis to discover biomarker candidates for ABMR (n = 12). Of 1820 exosomal proteins in the discovery cohort, four proteins were specifically associated with ABMR: cystatin C (CST3), serum paraoxonase/arylesterase 1, retinol-binding protein 4, and lipopolysaccharide−binding protein (LBP). In the validation cohort, the level of urinary exosomal LBP was significantly higher in the ABMR group (n = 25) compared with the T-cell-mediated rejection (TCMR) group and the no major abnormality (NOMOA) group. Urinary exosomal CST3 level was significantly higher in the ABMR group compared with the control and NOMOA groups. Immunohistochemical staining showed that LBP and CST3 in the glomerulus were more abundant in the ABMR group compared with other groups. The combined prediction probability of urinary exosomal LBP and CST3 was significantly correlated with summed LBP and CST3 intensity scores in the glomerulus and peritubular capillary as well as Banff g + ptc scores. Urinary exosomal CST3 and LBP could be potent biomarkers for ABMR after kidney transplantation.

Detection of Epidermal Growth Factor Receptor Expression in Breast Cancer Cell Lines Using an Ion-Sensitive Field-Effect Transistor in Combination with Enzymatic Chemical Signal Amplification

A novel strategy for epidermal growth factor receptor (EGFR) detection using a cell-based field-effect transistor (FET) with enzymatic chemical signal amplification is proposed. Four human breast cancer cell lines [BT474, MDA-MB-231 (MM231), MDA-MB-468 (MM468), and MDA-MB-453 (MM453)] were used to compare the expression levels of EGFR. The cells were non-specifically captured on the surface of the gate of the FET, irrespective of their surface antigens. With this configuration, the heterogeneity of the cells would be analyzed using secondary antibodies conjugated to different kinds of enzymes. Four breast cancer cell lines with different levels of EGFR expression were captured on the respective surfaces of the extracellular matrix (ECM) gel-coated gates of the FETs. Glucose oxidase (GOx) was conjugated to the secondary antibody, and the output signals of the cell-based FETs changed depending on the expression levels of EGFR upon addition of glucose. The order of the expression levels of EGFR among the four cell lines, determined with the cell-based FETs, was consistent with the results of fluorescence detection determined by fluorescence-activated cell sorting (FACS). The cell-based FETs are advantageous for miniaturization and in massive parallel analyses of target molecules expressed on the membranes of cells and EVs, and their small size and cost effectiveness for cancer testing could enable their realization in a future liquid biopsy.

Urinary extracellular vesicle mRNA analysis of sodium chloride cotransporter in hypertensive patients under different conditions

Urinary extracellular vesicles (UEV) mainly derive from cells of the urogenital tract and their cargo (proteins, nucleic acids, lipids, etc.) reflects their cells of origin. Na chloride cotransporter (NCC) is expressed at the kidney level in the distal convoluted tubule, is involved in salt reabsorption, and is the target of the diuretic thiazides. NCC protein has been recognized and quantified in UEV in previous studies; however, UEV NCC mRNA has never been studied. This study aimed to identify and analyze NCC mRNA levels in primary aldosteronism (PA). The rationale for this investigation stems from previous observations regarding NCC (protein) as a possible biomarker for the diagnosis of PA. To evaluate modulations in the expression of NCC, we analyzed NCC mRNA levels in UEV in PA and essential hypertensive (EH) patients under different conditions, that is, before and after saline infusion, anti-aldosterone pharmacological treatment, and adrenal surgery. NCC mRNA was measured by RT-qPCR in all the samples and was regulated by volume expansion. Its response to mineralocorticoid receptor antagonist was correlated with renin, and it was increased in PA patients after adrenalectomy. NCC mRNA is evaluable in UEV and it can provide insights into the pathophysiology of distal convolute tubule in different clinical conditions including PA.

Urinary exosomes: Emerging therapy delivery tools and biomarkers for urinary system diseases

Urinary exosomes (UE) are small circular membranous vesicles with a lipid bilayer with a diameter of 40-160 nm secreted by epithelial cells of the kidney and genitourinary system, which can reflect the physiological and functional status of secretory cells. Protein and RNA in exosomes can be used as markers for diseases diagnosis. Urine specimens are available and non-invasive. The protein and RNA in UE are more stable than the soluble protein and RNA in urine, which have broad application prospects in the diagnosis of urinary system diseases. This article reviews the recent advances in the application of protein or RNA in UE as markers to the diagnosis of urinary system diseases.

Acute Intravenous NaCl and Volume Expansion Reduces Sodium-Chloride Cotransporter Abundance and Phosphorylation in Urinary Extracellular Vesicles

Background

Sodium chloride (NaCl) loading and volume expansion suppress the renin-angiotensin-aldosterone system to reduce renal tubular reabsorption of NaCl and water, but effects on the sodium-chloride cotransporter (NCC) and relevant renal transmembrane proteins that are responsible for this modulation in humans are less well investigated.

Methods

We used urinary extracellular vesicles (uEVs) as an indirect readout to assess renal transmembrane proteins involved in NaCl and water homeostasis in 44 patients with hypertension who had repeatedly raised aldosterone/renin ratios undergoing infusion of 2 L of 0.9% saline over 4 hours.

Results

When measured by mass spectrometry in 13 patients, significant decreases were observed in NCC (median fold change [FC]=0.70); pendrin (FC=0.84); AQP2 (FC=0.62); and uEV markers, including ALIX (FC=0.65) and TSG101 (FC=0.66). Immunoblotting reproduced the reduction in NCC (FC=0.54), AQP2 (FC=0.42), ALIX (FC=0.52), and TSG101 (FC=0.55) in the remaining 31 patients, and demonstrated a significant decrease in phosphorylated NCC (pNCC; FC=0.49). However, after correction for ALIX, the reductions in NCC (FC=0.90) and pNCC (FC=1.00) were no longer apparent, whereas the significant decrease in AQP2 persisted (FC=0.62).

Conclusion

We conclude that (1) decreases in NCC and pNCC, induced by acute NaCl loading and volume expansion, may be due to diluted post-test urines; (2) the lack of change of NCC and pNCC when corrected for ALIX, despite a fall in plasma aldosterone, may be due to the lack of change in plasma K⁺; and (3) the decrease in AQP2 may be due to a decrease in vasopressin in response to volume expansion.

Guanosine protects against glycerol-induced acute kidney injury via up-regulation of the klotho gene

Objectives

Acute Kidney Injury (AKI) is characterized by a rapid and reversible decline in renal function with a rapid decrease in Glomerular Filtration Rate (GFR), which is associated with high mortality. Rhabdomyolysis accounts for 10-40% of AKI, to which the therapeutic approach is limited. Klotho is a protein that modulates sodium-phosphate co-transporters, ion channels that have been reported to have a renal protective effect. Guanosine, a purine nucleoside, has already been reported to have a renal protective effect; however, the mechanism of such protection and its relation to Klotho modification has not been evaluated yet. This study aims to evaluate the mechanism of the protective effect of guanosine against rhabdomyolysis-induced AKI and its relation to the expression of the Klotho gene.

Materials and Methods

In the current study, rats were divided into three groups: control, glycerol-induced AKI, and guanosine-treated. Serum urea and creatinine levels, renal tissue Total Antioxidant Capacity (TAC), and Klotho and Cystatin C genes expression were evaluated. Furthermore, caspase-3 immunostaining and histopathological evaluations were done.

Results

Results showed that guanosine treatment resulted in a significant reduction in serum urea and creatinine, Cystatin C genes expression, and caspase-3 immunoexpression, and an increase in TAC and Klotho genes expression. Results also revealed an improvement of renal histopathology when compared with the glycerol-induced AKI group.

Conclusion

Guanosine may be a promising agent in the treatment of rhabdomyolysis-induced AKI. The proposed mechanism for guanosine may be through its ability to enhance Klotho gene expression in renal tissue, with subsequent antioxidant and anti-apoptotic activity.

Potential Application of Exosomes in Vaccine Development and Delivery

Exosomes are cell-derived components composed of proteins, lipid, genetic information, cytokines, and growth factors. They play a vital role in immune modulation, cell-cell communication, and response to inflammation. Immune modulation has downstream effects on the regeneration of damaged tissue, promoting survival and repair of damaged resident cells, and promoting the tumor microenvironment via growth factors, antigens, and signaling molecules. On top of carrying biological messengers like mRNAs, miRNAs, fragmented DNA, disease antigens, and proteins, exosomes modulate internal cell environments that promote downstream cell signaling pathways to facilitate different disease progression and induce anti-tumoral effects. In this review, we have summarized how vaccines modulate our immune response in the context of cancer and infectious diseases and the potential of exosomes as vaccine delivery vehicles. Both pre-clinical and clinical studies show that exosomes play a decisive role in processes like angiogenesis, prognosis, tumor growth metastasis, stromal cell activation, intercellular communication, maintaining cellular and systematic homeostasis, and antigen-specific T- and B cell responses. This critical review summarizes the advancement of exosome based vaccine development and delivery, and this comprehensive review can be used as a valuable reference for the broader delivery science community.

Using human urinary extracellular vesicles to study physiological and pathophysiological states and regulation of the sodium chloride cotransporter

The thiazide-sensitive sodium chloride cotransporter (NCC), expressed in the renal distal convoluted tubule, plays a major role in Na⁺, Cl^- and K⁺ homeostasis and blood pressure as exemplified by the symptoms of patients with non-functional NCC and Gitelman syndrome. NCC activity is modulated by a variety of hormones, but is also influenced by the extracellular K⁺ concentration. The putative "renal-K⁺ switch" mechanism is a relatively cohesive model that links dietary K⁺ intake to NCC activity, and may offer new targets for blood pressure control. However, a remaining hurdle for full acceptance of this model is the lack of human data to confirm molecular findings from animal models. Extracellular vesicles (EVs) have attracted attention from the scientific community due to their potential roles in intercellular communication, disease pathogenesis, drug delivery and as possible reservoirs of biomarkers. Urinary EVs (uEVs) are an excellent sample source for the study of physiology and pathology of renal, urothelial and prostate tissues, but the diverse origins of uEVs and their dynamic molecular composition present both methodological and data interpretation challenges. This review provides a brief overview of the state-of-the-art, challenges and knowledge gaps in current uEV-based analyses, with a focus on the application of uEVs to study the "renal-K⁺ switch" and NCC regulation. We also provide recommendations regarding biospecimen handling, processing and reporting requirements to improve experimental reproducibility and interoperability towards the realisation of the potential of uEV-derived biomarkers in hypertension and clinical practice.

Migrasomes and exosomes; different types of messaging vesicles in podocytes

Podocytes, highly specified kidney epithelial cells, live under several pathological stimuli and stresses during which they adapt themselves to keep homeostasis. Nevertheless, under extreme stress, a complex scenario of podocyte damage and its consequences occur. Podocyte damage causes foot process effacement and their detachment from the glomerular basement membrane, leading to proteinuria. Podocyte-derived extracellular vesicles (pEVs), mainly microparticles and exosomes are considered as signaling mediators of intercellular communication. Recently, it has been shown that throughout the injury-related migration procedure, podocytes are capable of releasing the injury-related migrasomes. Evidence indicates that at the early stages of glomerular disorders, increased levels of pEVs are observed in urine. At the early stage of nephropathy, pEVs especially migrasomes seem to be more sensitive and reliable indicators of podocyte stress and/or damage than proteinuria. This review highlights the current knowledge of pEVs and their values for the diagnosis of different kidney diseases.

Isolation and analysis methods of extracellular vesicles (EVs)

Extracellular vesicles (EVs) have been recognized as an evolving biomarker within the liquid biopsy family. While carrying both host cell proteins and different types of RNAs, EVs are also present in sufficient quantities in biological samples to be tested using many molecular analysis platforms to interrogate their content. However, because EVs in biological samples are comprised of both disease and non-disease related EVs, enrichment is often required to remove potential interferences from the downstream molecular assay. Most benchtop isolation/enrichment methods require > milliliter levels of sample and can cause varying degrees of damage to the EVs. In addition, some of the common EV benchtop isolation methods do not sort the diseased from the non-diseased related EVs. Simultaneously, the detection of the overall concentration and size distribution of the EVs is highly dependent on techniques such as electron microscopy and Nanoparticle Tracking Analysis, which can include unexpected variations and biases as well as complexity in the analysis. This review discusses the importance of EVs as a biomarker secured from a liquid biopsy and covers some of the traditional and non-traditional, including microfluidics and resistive pulse sensing, technologies for EV isolation and detection, respectively.

Analytical Technologies for Liquid Biopsy of Subcellular Materials

Liquid biopsy markers, which can be secured from a simple blood draw or other biological samples, are used to manage a variety of diseases and even monitor for bacterial or viral infections. Although there are several different types of liquid biopsy markers, the subcellular ones, including cell-free DNA, microRNA, extracellular vesicles, and viral particles, are evolving in terms of their utility. A challenge with liquid biopsy markers is that they must be enriched from the biological sample prior to analysis because they are a vast minority in a mixed population, and potential interferences may be present in the sample matrix that can inhibit profiling the molecular cargo from the subcellular marker. In this article, we discuss existing and developing analytical enrichment platforms used to isolate subcellular liquid biopsy markers, and discuss their figures of merit such as recovery, throughput, and purity.

Presence of Urinary Exosomes for Liquid Biopsy of Clear Cell Renal Cell Carcinoma: Protocol for a Pilot Feasibility Study

Background

Approximately 70%-80% of kidney cancers are clear cell renal cell carcinomas (CCRCCs). Patient management is based on imaging (abdominal ultrasound and computerized tomography), surgical excision of the tumor, and pathological analysis. A tissue biopsy is therefore necessary to confirm the diagnosis and avoid unnecessary nephrectomy. For metastatic cancers, a tissue biopsy is essential for establishing the targeted therapy. This biopsy of tumor material is invasive and painful. Other techniques such as liquid biopsy would help reduce the need for tissue biopsy. The development of a simple biological test for diagnosis is essential. CA9 is a powerful marker for the diagnosis of CCRCC. Exosomes have become a major source of liquid biopsy because they carry tumor proteins, RNA, and lipids. Urine is the most convenient biological liquid for exosome sampling.

Objective

The aim of this study (PEP-C study) is mainly to determine whether it is possible to detect urinary exosomal CA9 for the molecular diagnosis of CCRCC.

Methods

This study will include 60 patients with CCRCC and 40 noncancer patients. Exosomes will be isolated from urine samples and exosomal CA9 will be detected by transmission electron microscopy, flow cytometry, and reverse transcription-quantitative polymerase chain reaction.

Results

This study is currently underway with funding support from the CHU Saint-Etienne of France.

Conclusions

We expect to demonstrate that urinary tumor exosomes could be a novel liquid biopsy to diagnose CCRCC and to guide clinicians in treatment decision-making.

Trial Registration

ClinicalTrials.gov NCT04053855; https://clinicaltrials.gov/ct2/show/NCT04053855

International Registered Report Identifier (IRRID)

DERR1-10.2196/24423

mRNAs in urinary nano-extracellular vesicles as potential biomarkers for non-invasive kidney biopsy

Urinary nano-extracellular vesicles (NVs), including exosomes and microvesicles, are considered potential biomarkers for kidney diseases using liquid biopsies. However, clinical application of urinary NVs has not yet been validated. In the present study, the levels of mRNAs in urinary NVs in animal models of kidney disease were assessed. Urine samples were collected from the animal models and urinary NVs were isolated by ultracentrifugation. Gene expression levels of kidney injury markers in urinary NVs and renal tissue were quantified by reverse transcription-quantitative PCR. The mRNA levels of desmin, a podocyte injury marker, in urinary NVs was markedly increased in the puromycin aminonucleoside (PAN) nephritis model, in parallel with enhanced desmin expression in kidney tissues. The expression of regulator of calcineurin 1 and the podocin to nephrin ratio (PNR) were also increased in the PAN nephritis model. Treatment with prednisolone mitigated these changes in gene expression as well as proteinuria. PNR, which is considered a predictive marker of glomerular dysfunction, in urinary NVs was highly correlated with urinary protein excretion (P<0.01). Furthermore, PNR in urinary NVs of Zucker diabetic fatty rats, a diabetic kidney disease model, was correlated with urinary albumin excretion (P<0.01). These results suggest that changes in mRNA levels of urinary NVs reflect the disease status of kidney tissues and their functional alterations. Collectively, mRNA analysis of urinary NVs may be used as a liquid biopsy tool for improved classification and performance of risk prediction to determine the severity of kidney diseases.

Progress of Mesenchymal Stem Cell-Derived Exosomes in Tissue Repair

Mesenchymal stem cells (MSCs) are a kind of adult stem cells with self-replication and multidirectional differentiation, which can differentiate into tissue-specific cells under physiological conditions, maintaining tissue self-renewal and physiological functions. They play a role in the pathological condition by lateral differentiation into tissue-specific cells, replacing damaged tissue cells by playing the role of a regenerative medicine , or repairing damaged tissues through angiogenesis, thereby, regulating immune responses, inflammatory responses, and inhibiting apoptosis. It has become an important seed cell for tissue repair and organ reconstruction, and cell therapy based on MSCs has been widely used clinically. The study found that the probability of stem cells migrating to the damaged area after transplantation or differentiating into damaged cells is very low, so the researchers believe the leading role of stem cell transplantation for tissue repair is paracrine secretion, secreting growth factors, cytokines or other components. Exosomes are biologically active small vesicles secreted by MSCs. Recent studies have shown that they can transfer functional proteins, RNA, microRNAs, and lncRNAs between cells, and greatly reduce the immune response. Under the premise of promoting proliferation and inhibition of apoptosis, they play a repair role in tissue damage, which is caused by a variety of diseases. In this paper, the biological characteristics of exosomes (MSCs-exosomes) derived from mesenchymal stem cells, intercellular transport mechanisms, and their research progress in the field of stem cell therapy are reviewed.

miR-451 Loaded Exosomes Are Released by the Renal Cells in Response to Injury and Associated With Reduced Kidney Function in Human

Micro-RNAs (miRs) encapsulated inside urinary exosomes (uEs) have the potential as early biomarkers. Previously, we reported that a rise in uE miR-451 predicted albuminuria in diabetic rats; however, whether the rise was protective or detrimental, and occurred in response to injury or general hyperglycemia, was unknown. To address this, we studied both human and rat models of renal disease. In humans, uE miR-451 was approximately twofold higher in subjects with early-stage chronic kidney disease (CKD; serum creatinine < 2.0 mg/dl; n = 28), as compared to age-matched healthy controls (n = 23), and had a significant negative correlation with estimated glomerular filtration rate (eGFR) (r² = −0.10, p = 0.01). Subgroup analysis of CKD subjects showed that those without diabetes had slightly (∼30%) but significantly higher uE miR-451 as compared to those with diabetes, with no differences in albumin excretion, eGFR, serum sodium, and potassium. Using human proximal tubule (hPT) cells, we found that locked nucleic acid (LNA) inhibition of miR-451 resulted in a significant increase in the messenger RNA (mRNA) expression of kidney-injury-associated miR-451 targets, e.g., CAB39, TBX1, and YWHAZ, as compared to treatment with a control LNA. Moreover, hPT cells and their secreted exosomes showed an increase in miR-451 in response to mechanical injury but not high glucose (20 versus 5 mM). For further proof of concept, in diabetic rats, we showed that atorvastatin (AT), a treatment proven to attenuate renal injury without affecting systemic glucose levels, reduced uE miR-451 with the concomitant restoration of renal miR-451. These data elucidate the stimuli for renal miR-451 expression and exosomal release and support its role as a therapeutic target and early biomarker for renal injury in humans.

The potential of exosomes as theragnostics in various clinical situations

Exosomes are membrane-bound cargo measuring 30–140 nm comprised of a lipid bilayer containing various proteins, RNAs, DNAs, and bioactive lipids that can be transferred between cells. They have been shown to be produced and released by many different types of healthy and diseased cells. Exosomes are secreted by all types of cells in culture, and are also found in various body fluids including blood, saliva, urine, and breast milk. Exosomes are essential for healthy physiological as well as pathological processes. In addition to their normal function, exosomes are involved in the development and progression of various diseases, potentiating cellular stress and damage. Pathogens take advantage of exosome release from infected host cells by manipulating host-derived exosomes to evade the immune system responses. Exosomes are involved in other pathological conditions such as neurodegenerative diseases, liver diseases, heart failure, cancer, diabetes, kidney diseases, osteoporosis and atherosclerotic cardiovascular disease. Hence, we can exploit exosomes as biomarkers and vaccines and modify them rationally for therapeutic interventions including tissue engineering. Further studies on exosomes will explore their potential and provide new methodology for effective clinical diagnostics and therapeutic strategies: such uses can be called exosome theragnostics. This chapter reviews the potential theragnostic (diagnostic and therapeutic) application of exosomes in major organ systems in clinical fields.

Determination of variability due to biological and technical variation in urinary extracellular vesicles as a crucial step in biomarker discovery studies

Urinary extracellular vesicles (EVs) are an attractive source of biomarkers for urological diseases. A crucial step in biomarker discovery studies is the determination of the variation parameters to perform a sample size calculation. In this way, a biomarker discovery study with sufficient statistical power can be performed to obtain biologically significant biomarkers. Here, a variation study was performed on both the protein and lipid content of urinary EVs of healthy individuals, aged between 52 and 69 years. Ultrafiltration (UF) in combination with size exclusion chromatography (SEC) was used to isolate the EVs from urine. Different experimental variation set-ups were used in this variation study. The calculated standard deviations (SDs) of the 90% least variable peptides and lipids did not exceed 2 and 1.2, respectively. These parameters can be used in a sample size calculation for a well-designed biomarker discovery study at the cargo of EVs.

Human Urinary mRNA as a Biomarker of Cardiovascular Disease

Supplemental Digital Content is available in the text.

Background

mRNA in urine supernatant (US-mRNA) might encode information about renal and cardiorenal pathophysiology, including hypertension. H, whether the US-mRNA transcriptome reflects that of renal tissues and whether changes in renal physiology are detectable using US-mRNA is unknown.

Methods

We compared transcriptomes of human urinary extracellular vesicles and human renal cortex. To avoid similarities attributable to ubiquitously expressed genes, we separately analyzed ubiquitously expressed and highly kidney-enriched genes. To determine whether US-mRNA reflects changes in renal gene expression, we assayed cell-depleted urine for transcription factor activity of mineralocorticoid receptors (MR) using probe-based quantitative polymerase chain reaction. The urine was collected from prehypertensive individuals (n=18) after 4 days on low-sodium diet to stimulate MR activity and again after suppression of MR activity via sodium infusion.

Results

In comparing this US-mRNA and human kidney cortex, expression of 55 highly kidney-enriched genes correlated strongly (r_s=0.82) while 8457 ubiquitously expressed genes correlated moderately (r_s=0.63). Standard renin-angiotensin-aldosterone system phenotyping confirmed the expected response to sodium loading. Cycle threshold values for MR-regulated targets (SCNN1A, SCNN1G, TSC22D3) changed after sodium loading, and MR-regulated targets (SCNN1A, SCNN1G, SGK1, and TSC22D3) correlated significantly with serum aldosterone and inversely with urinary sodium excretion.

Conclusions

RNA-sequencing of urinary extracellular vesicles shows concordance with human kidney. Perturbation in human endocrine signaling (MR activation) was accompanied by changes in mRNA in urine supernatant. Our findings could be useful for individualizing pharmacological therapy in patients with disorders of mineralocorticoid signaling, such as resistant hypertension. More generally, these insights could be used to noninvasively identify putative biomarkers of disordered renal and cardiorenal physiology.

Increased expression and phosphorylation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoforms in urinary exosomes in pre-eclampsia

Background

Glycolysis is altered in various kidney diseases, but little is known about glycolysis in pre-eclampsia, a multi-system disorder with major pathological effects on the kidney. Urinary exosomes provide a non-invasive alternative for studying changes in kidney metabolism. This study aims to characterise the expression and phosphorylation of isozymes of the key glycolytic regulatory protein, 6-phosphofructokinase-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2), in urinary exosomes of subjects with pre-eclampsia (PE), compared to normotensive non-pregnant (NC) and normotensive pregnant (NP) controls.

Methods

A cross-sectional study of NC (n = 19), NP (n = 23) and PE (n = 29) subjects was performed. Exosomes were isolated from urine samples by differential ultracentrifugation, and then analyzed by Western blot and densitometry for expression of PFK-2/FBPase-2 isozymes (PFKFB2, PFKFB3 and PFKFB4) and phosphorylation of PFKFB2 at residues Ser483 and Ser466 and PFKFB3 at Ser461.

Results

PFKFB2 expression was increased 4.7-fold in PE compared to NP (p < 0.001). PFKFB2 phosphorylation at Ser483 was increased 2.6-fold in PE compared to NP (p = 0.002). Expression of phosphorylated PFKFB2/PFKFB3 at Ser466/Ser461 was increased in PE, being present in 77.4% (95% CI 59.9–88.9%) of PE and 8.3% (95% CI 1.2–27.0%) of NP samples (p < 0.001). PFKFB3 was more commonly expressed in PE, detected in 90.3% (95% CI 74.3–97.4%) of PE and 8.3% (95% CI 1.2–27.0%) of NP samples (p < 0.001). PFKFB4 had a 7.2-fold increase in expression in PE compared to NP (p < 0.001). No significant differences between NP and NC groups were observed.

Conclusion

Regulatory proteins that increase glycolysis are increased in the urinary exosomes of subjects with pre-eclampsia, suggesting that renal glycolysis may be increased in this condition.

Exosomes populate the cerebrospinal fluid of preterm infants with post-haemorrhagic hydrocephalus

BACKGROUND

Preterm infants are at risk of germinal matrix haemorrhage-intraventricular haemorrhage (GMH-IVH) which leads to post-haemorrhagic hydrocephalus (PHH) in 30% of infants; this is associated with moderate-severe neurodevelopmental impairment and confers significant risk of cerebral palsy. There are however no predictive indicators of the severity or long-term outcome after GMH-IVH. In recent years, endosome-derived extracellular vesicles (EVs) or exosomes have been isolated from biofluids and shown to mediate intercellular communication via selective enrichment in proteins and micro-RNAs.

METHODS

This study aimed to isolate and characterise EVs from the cerebrospinal fluid (CSF) of 3 preterm infants with PHH using nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM) with immunogold protein labelling, and micro-RNA analysis.

RESULTS

NTA of unaltered CSF revealed a heterogeneous and dynamic population of EVs. Exosomal-sized EVs were isolated by differential ultracentrifugation and TEM confirmed the presence of CD63⁺ and CD81⁺ exosomes. The micro-RNAs miR-9, miR-17, miR-26a, miR-124 and miR-1911 were detected within the exosome-enriched fraction and profiled over time.

CONCLUSION

This is the first reported characterisation of exosomes from the CSF of preterm infants with post-haemorrhagic hydrocephalus.

Exosomes: Therapy delivery tools and biomarkers of diseases

Virtually all cells in the organism secrete extracellular vesicles (EVs), a heterogeneous population of lipid bilayer membrane-enclosed vesicles that transport and deliver payloads of proteins and nucleic acids to recipient cells, thus playing central roles in cell-cell communications. Exosomes, nanosized EVs of endosomal origin, regulate many pathophysiological processes including immune responses and inflammation, tumour growth, and infection. Healthy subjects and patients with different diseases release exosomes with different RNA and protein contents into the circulation, which can be measured as biomarkers. The discovery of exosomes as natural carriers of functional small RNA and proteins has raised great interest in the drug delivery field, as it may be possible to harness these vesicles for therapeutic delivery of miRNA, siRNA, mRNA, lncRNA, peptides, and synthetic drugs. However, systemically delivered exosomes accumulate in liver, kidney, and spleen. Targeted exosomes can be obtained by displaying targeting molecules, such as peptides or antibody fragments recognizing target antigens, on the outer surface of exosomes. Display of glycosylphosphatidylinositol (GPI)-anchored nanobodies on EVs is a novel technique that enables EV display of a variety of proteins including antibodies, reporter proteins, and signaling molecules. However, naturally secreted exosomes show limited pharmaceutical acceptability. Engineered exosome mimetics that incorporate desirable components of natural exosomes into synthetic liposomes or nanoparticles, and are assembled using controllable procedures may be more acceptable pharmaceutically. In this communication, we review the current understanding of physiological and pathophysiological roles of exosomes, their potential applications as diagnostic markers, and current efforts to develop improved exosome-based drug delivery systems.

Urinary Exosomes and Their Cargo: Potential Biomarkers for Mineralocorticoid Arterial Hypertension?

Arterial hypertension (AHT) currently affects approximately 40% of adults worldwide, and its pathological mechanisms are mainly related to renal, vascular, and endocrine systems. Steroid hormones as aldosterone and cortisol are highly relevant to human endocrine physiology, and also to endocrine hypertension. Pathophysiological conditions, such as primary aldosteronism, affect approximately 10% of patients diagnosed with AHT and are secondary to a high production of aldosterone, increasing the risk also for cardiovascular damage and heart diseases. Excess of aldosterone or cortisol increases the activity of the mineralocorticoid receptor (MR) in epithelial and non-epithelial cells. Current research in this field highlights the potential regulatory mechanisms of the MR pathway, including pre-receptor regulation of the MR (action of 11BHSD2), MR activating proteins, and the downstream genes/proteins sensitive to MR (e.g., epithelial sodium channel, NCC, NKCC2). Mineralocorticoid AHT is present in 15-20% of hypertensive subjects, but the mechanisms associated to this condition have been poorly described, due mainly to the absence of reliable biomarkers. In this way, steroids, peptides, and lately urinary exosomes are thought to be potential reporters of biological processes. This review highlight exosomes and their cargo as potential biomarkers of metabolic changes associated to mineralocorticoid AHT. Recent reports have shown the presence of RNA, microRNAs, and proteins in urinary exosomes, which could be used as biomarkers in physiological and pathophysiological conditions. However, more studies are needed in order to benefit from exosomes and the exosomal cargo as a diagnostic tool in mineralocorticoid AHT.

Quantification of Small Extracellular Vesicles by Size Exclusion Chromatography with Fluorescence Detection

Chemical analysis of small extracellular vesicles (sEVs) circulating in body fluids holds potentials in noninvasive diagnosis of diseases and evaluation of therapeutic treatments. However, quantification of sEVs remains a challenge due to lacking of cost-effective analytical protocols. Herein we report a facile method based on size exclusion chromatography with fluorescence detection (SEC-FD) for sEVs quantification. After removal of cells and cell debris, a 0.50 mL sample (e.g., cell culture medium) is incubated with CM-Dil dye to fluorescently label sEVs. The incubation solution is then separated on a SEC column packed with Sepharose CL-4B. The eluent is monitored fluorescently at Ex553 nm/Em570 nm by using a fluorometer equipped with a 50-μL flow through cuvette. Separation efficiency of the proposed SEC-FD method was evaluated by analyzing 100 nm liposomes and albumin-FITC conjugate. Liposomes were eluted out in less than 6 min, about 10 min before albumin-FITC. A separation repeatability (RSD in retention time) of 1.4% (n = 5) was obtained for liposomes. In analysis of cell culture media, linear calibration curves based on SEC-FD peak height versus sEVs concentration were obtained with r2 value of 0.996. Intraday quantification repeatability (RSD in peak height) was 3.2% (n = 5). The detection limit was estimated to be 2.9 × 107 exosome particles/mL. The proposed assay was applied to the first study of sEVs secretion from TK6 cells cultured in serum-free medium for a culturing period from 1 to 48 h.

New molecular insights in diabetic nephropathy

Diabetes mellitus represents one of the major causes of functional kidney impairment. The review highlights the most significant steps made over the last decades in understanding the molecular basis of diabetic nephropathy (DN), which may provide reliable biomarkers for early diagnosis and prognosis, along with new molecular targets for personalized medicine. There is an increased interest in developing new therapeutic strategies to slow DN progression for improving patients' quality of life and reducing all-cause morbidity and disease-associated mortality. It is highly important to have a science-based medical attitude when facing diabetic patients with associated comorbidities and risk of rapid evolution toward end-stage renal disease. The data discussed herein were mainly from MEDLINE and PubMed articles published in English from 1990 to 2015 and from up-to-date. The search term was "diabetic nephropathy and oxidative stress".

Evaluation of cystatin C as an early biomarker of cadmium nephrotoxicity in the rat

Cadmium (Cd) is a nephrotoxic environmental pollutant that causes insidious injury to the proximal tubule that results in severe polyuria and proteinuria. Cystatin C is a low molecular weight protein that is being evaluated as a serum and urinary biomarker for various types of ischemic and nephrotoxic renal injury. The objective of the present study was to determine if cystatin C might be a useful early biomarker of Cd nephrotoxicity. Male Sprague-Dawley rats were given daily injections of Cd for up to 12 weeks. At 3, 6, 9 and 12 weeks, urine samples were analyzed for cystatin C, protein, creatinine, β2 microglobulin and kidney injury molecule-1. The results showed that Cd caused a significant increase in the urinary excretion of cystatin C that occurred 3-4 weeks before the onset of polyuria and proteinuria. Serum levels of cystatin C were not altered by Cd. Immunolabeling studies showed that Cd caused the relocalization of cystatin C from the cytoplasm to the apical surface of the epithelial cells of the proximal tubule. The Cd-induced changes in cystatin C labelling paralleled those of the brush border transport protein, megalin, which has been implicated as a mediator of cystatin C uptake in the proximal tubule. These results indicate that Cd increases the urinary excretion of cystatin C, and they suggest that this effect may involve disruption of megalin-mediated uptake of cystatin C by epithelial cells of the proximal tubule.

Extracellular Vesicles as Biomarkers of Systemic Lupus Erythematosus

Systemic lupus erythematosus is an autoimmune disease that predominantly affects women and typically manifests in multiple organs. The damage caused by this disorder is characterized by a chronic inflammatory state. Extracellular vesicles (EVs), including microvesicles (also known as microparticles), apoptotic bodies, and exosomes, are recognized vehicles of intercellular communication, carrying autoantigens, cytokines, and surface receptors. Therefore, the evidence of EVs and their cargo as biomarkers of autoimmune disease is rapidly expanding. This review will focus on biogenesis of extracellular vesicles, their pathophysiological roles, and their potential as biomarkers and therapeutics in inflammatory disease, especially in systemic lupus erythematosus.