Senescent Kidney Cells in Hypertensive Patients Release Urinary Extracellular Vesicles

Cellular senescence promotes macrophage-to-myofibroblast transition in chronic ischemic renal disease

Cellular senescence participates in the pathophysiology of post-stenotic kidney damage, but how it regulates tissue remodeling is incompletely understood. Macrophage-myofibroblast transition (MMT) contributes to the development of tissue fibrosis. We hypothesized that cellular senescence contributes to MMT and renal fibrosis in mice with renal artery stenosis (RAS). INK-ATTAC mice expressing p16INK-4a and green fluorescent protein in senescent cells were assigned to control or unilateral RAS, untreated or treated with AP20187 (an apoptosis inducer in p16INK-4a-expressing cells) for 4 weeks. Renal perfusion was studied in vivo using micro-MRI, and kidney morphology, senescence, and MMT ex vivo. Cellular senescence was induced in human renal proximal tubular epithelial cells (HRPTEpiC) in vitro, and interferon-induced transmembrane protein-3 (IFITM3), a cellular senescence vector, was silenced (siRNA) or over-expressed (plasmid). HRPTEpiC were then co-incubated with macrophages with silenced integrin-3 (ITGB3), a regulator of mesenchymal transitions. CD68/p16INK-4a/α-SMA co-expression and senescence markers were studied. Murine RAS kidneys showed increased expression of p16INK-4a and MMT markers (F4/80, α-SMA) vs. controls, which decreased after AP20187, as did renal fibrosis and plasma creatinine, whereas renal perfusion increased. IFITM3 and ITGB3 expression were upregulated in senescent HRPTEpiC or co-cultured macrophages, respectively. MMT markers and TGF-β/Smad3 expression also rose in these macrophages and decreased after IFITM3 or ITGB3 silencing. p16INK-4a-expressing macrophages may regulate interstitial fibrosis in RAS via MMT. This process is associated with elevated expression of ITGB3 and TGF-β/Smad3 pathway activation through neighboring senescent cell-derived IFITM3. These findings may implicate MMT as a therapeutic target in ischemic kidneys.

Prominosomes - a particular class of extracellular vesicles containing prominin-1/CD133?

Extracellular membrane vesicles (EVs) offer promising values in various medical fields, e.g., as biomarkers in liquid biopsies or as native (or bioengineered) biological nanocarriers in tissue engineering, regenerative medicine and cancer therapy. Based on their cellular origin EVs can vary considerably in composition and diameter. Cell biological studies on mammalian prominin-1, a cholesterol-binding membrane glycoprotein, have helped to reveal new donor membranes as sources of EVs. For instance, small EVs can originate from microvilli and primary cilia, while large EVs might be produced by transient structures such as retracting cellular extremities of cancer cells during the mitotic rounding process, and the midbody at the end of cytokinesis. Here, we will highlight the various subcellular origins of prominin-1+ EVs, also called prominosomes, and the potential mechanism(s) regulating their formation. We will further discuss the molecular and cellular characteristics of prominin-1, notably those that have a direct effect on the release of prominin-1+ EVs, a process that might be directly implicated in donor cell reprogramming of stem and cancer stem cells. Prominin-1+ EVs also mediate intercellular communication during embryonic development and adult homeostasis in healthy individuals, while disseminating biological information during diseases.

Podocyte senescence: from molecular mechanisms to therapeutics

As an important component of the glomerular filtration membrane, the state of the podocytes is closely related to kidney function, they are also key cells involved in aging and play a central role in the damage caused by renal aging. Therefore, understanding the aging process of podocytes will allow us to understand their susceptibility to injury and identify targeted protective mechanisms. In fact, the process of physiological aging itself can induce podocyte senescence. Pathological stresses, such as oxidative stress, mitochondrial damage, secretion of senescence-associated secretory phenotype, reduced autophagy, oncogene activation, altered transcription factors, DNA damage response, and other factors, play a crucial role in inducing premature senescence and accelerating aging. Senescence-associated-β-galactosidase (SA-β-gal) is a marker of aging, and β-hydroxybutyric acid treatment can reduce SA-β-gal activity to alleviate cellular senescence and damage. In addition, CCAAT/enhancer-binding protein-α, transforming growth factor-β signaling, glycogen synthase kinase-3β, cycle-dependent kinase, programmed cell death protein 1, and plasminogen activator inhibitor-1 are closely related to aging. The absence or elevation of these factors can affect aging through different mechanisms. Podocyte injury is not an independent process, and injured podocytes interact with the surrounding epithelial cells or other kidney cells to mediate the injury or loss of podocytes. In this review, we discuss the manifestations, molecular mechanisms, biomarkers, and therapeutic drugs for podocyte senescence. We included elamipretide, lithium, calorie restriction, rapamycin; and emerging treatment strategies, such as gene and immune therapies. More importantly, we summarize how podocyte interact with other kidney cells.

Renovascular Disease and Mitochondrial Dysfunction in Human Mesenchymal Stem Cells

Key Points

Renovascular disease impairs the capacity of human adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic murine kidneys. miR-378h modulated the capacity of renovascular disease adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic kidneys in vivo .

Background

Renovascular disease leads to renal ischemia, hypertension, and eventual kidney failure. Autologous transplantation of adipose tissue–derived mesenchymal stem/stromal cells (MSCs) improves perfusion and oxygenation in stenotic human kidneys, but associated atherosclerosis and hypertension might blunt their effectiveness. We hypothesized that renovascular disease alters the human MSC transcriptome and impairs their reparative potency.

Methods

MSCs were harvested from subcutaneous abdominal fat of patients with renovascular disease and healthy volunteers (n =3 each), characterized and subsequently injected (5×105/200 μ l) into mice 2 weeks after renal artery stenosis or sham surgery (n =6/group). Two weeks later, mice underwent imaging and tissue studies. MSCs from healthy volunteers and in those with renovascular disease were also characterized by mRNA/microRNA (miRNA) sequencing. Based on these, MSC proliferation and mitochondrial damage were assessed in vitro before and after miRNA modulation and in vivo in additional renal artery stenosis mice administered with MSCs from renovascular disease pretreated with miR-378h mimic (n =5) or inhibitor (n =4).

Results

MSCs engrafted in stenotic mouse kidneys. Healthy volunteer MSCs (but not renovascular disease MSCs) decreased BP, improved serum creatinine levels and stenotic-kidney cortical perfusion and oxygenation, and attenuated peritubular capillary loss, tubular injury, and fibrosis. Genes upregulated in renovascular disease MSCs versus healthy volunteer MSCs were mostly implicated in transcription and cell proliferation, whereas those downregulated encoded mainly mitochondrial proteins. Upregulated miRNAs, including miR-378h, primarily target nuclear-encoded mitochondrial genes, whereas downregulated miRNAs mainly target genes implicated in transcription and cell proliferation. MSC proliferation was similar, but their mitochondrial structure and reparative function both in vivo and in vitro improved after miR-378h inhibition.

Conclusions

Renovascular disease impaired the reparative capacity of human MSCs, possibly by dysregulating miR-378h that targets mitochondrial genes.

Podcast

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Urinary podocyte markers of disease activity, therapeutic efficacy, and long-term outcomes in acute and chronic kidney diseases

A critical degree of podocyte depletion causes glomerulosclerosis, and persistent podocyte loss in glomerular diseases drives the progression to end-stage kidney disease. The extent of podocyte injury at a point in time can be histologically assessed by measuring podocyte number, size, and density ("Biopsy podometrics"). However, repeated invasive renal biopsies are associated with increased risk and cost. A noninvasive method for assessing podocyte injury and depletion is required. Albuminuria and proteinuria do not always correlate with disease activity. Podocytes are located on the urinary space side of the glomerular basement membrane, and as they undergo stress or detach, their products can be identified in urine. This raises the possibility that urinary podocyte products can serve as clinically useful markers for monitoring glomerular disease activity and progression ("Urinary podometrics"). We previously reported that urinary sediment podocyte mRNA reflects disease activity in both animal models and human glomerular diseases. This includes diabetes and hypertension which together account for 60% of new-onset dialysis induction patients. Improving approaches to preventing progression is an urgent priority for the renal community. Sufficient evidence now exists to indicate that monitoring urinary podocyte markers could serve as a useful adjunctive strategy for determining the level of current disease activity and response to therapy in progressive glomerular diseases.

PROM2 overexpression induces metastatic potential through epithelial-to-mesenchymal transition and ferroptosis resistance in human cancers

INTRODUCTION

Despite considerable therapeutic advances in the last 20 years, metastatic cancers remain a major cause of death. We previously identified prominin-2 (PROM2) as a biomarker predictive of distant metastases and decreased survival, thus providing a promising bio-target. In this translational study, we set out to decipher the biological roles of PROM2 during the metastatic process and resistance to cell death, in particular for metastatic melanoma.

METHODS AND RESULTS

Methods and results: We demonstrated that PROM2 overexpression was closely linked to an increased metastatic potential through the increase of epithelial-to-mesenchymal transition (EMT) marker expression and ferroptosis resistance. This was also found in renal cell carcinoma and triple negative breast cancer patient-derived xenograft models. Using an oligonucleotide anti-sense anti-PROM2, we efficaciously decreased PROM2 expression and prevented metastases in melanoma xenografts. We also demonstrated that PROM2 was implicated in an aggravation loop, contributing to increase the metastatic burden both in murine metastatic models and in patients with metastatic melanoma. The metastatic burden is closely linked to PROM2 expression through the expression of EMT markers and ferroptosis cell death resistance in a deterioration loop.

CONCLUSION

Our results open the way for further studies using PROM2 as a bio-target in resort situations in human metastatic melanoma and also in other cancer types.

Kidney Intrinsic Mechanisms as Novel Targets in Renovascular Hypertension

Almost a hundred years have passed since obstruction of the renal artery has been recognized to raise blood pressure. By now chronic renovascular disease (RVD) due to renal artery stenosis is recognized as a major source of renovascular hypertension and renal disease. In some patients, RVD unaccompanied by noteworthy renal dysfunction or blood pressure elevation may be incidentally identified during peripheral angiography. Nevertheless, in others, RVD might present as a progressive disease associated with diffuse atherosclerosis, leading to loss of renal function, renovascular hypertension, hemodynamic compromise, and a magnified risk for cardiovascular morbidity and mortality. Atherosclerotic RVD leads to renal atrophy, inflammation, and hypoxia but represents a potentially treatable cause of chronic renal failure because until severe fibrosis sets in the ischemic kidney, it retains a robust potential for vascular and tubular regeneration. This remarkable recovery capacity of the kidney begs for early diagnosis and treatment. However, accumulating evidence from both animal studies and randomized clinical trials has convincingly established the inadequate efficacy of renal artery revascularization to fully restore renal function or blood pressure control and has illuminated the potential of therapies targeted to the ischemic renal parenchyma to instigate renal regeneration. Some of the injurious mechanisms identified as potential therapeutic targets included oxidative stress, microvascular disease, inflammation, mitochondrial injury, and cellular senescence. This review recapitulates the intrinsic mechanisms that orchestrate renal damage and recovery in RVD and can be harnessed to introduce remedial opportunities.

Cellular senescence and kidney aging

Life expectancy is increasing worldwide, and by 2050 the proportion of the world's population over 65 years of age is estimated to surpass 1.5 billion. Kidney aging is associated with molecular and physiological changes that cause a loss of renal function and of regenerative potential. As the aging population grows, it is crucial to understand the mechanisms underlying these changes, as they increase the susceptibility to developing acute kidney injury (AKI) and chronic kidney disease (CKD). Various cellular processes and molecular pathways take part in the complex process of kidney aging. In this review, we will focus on the phenomenon of cellular senescence as one of the involved mechanisms at the crossroad of kidney aging, age-related disease, and CKD. We will highlight experimental and clinical findings about the role of cellular senescence in kidney aging and CKD. In addition, we will review challenges in senescence research and emerging therapeutic aspects. We will highlight the great potential of senolytic strategies for the elimination of harmful senescent cells to promote healthy kidney aging and to avoid age-related disease and CKD. This review aims to give insight into recent discoveries and future developments, providing a comprehensive overview of current knowledge on cellular senescence and anti-senescent therapies in the kidney field.

Impact of Aging and Cellular Senescence in the Pathophysiology of Preeclampsia

The incidence of hypertensive disorders of pregnancy is increasing, which may be due to several factors, including an increased age at pregnancy and more comorbid health conditions during reproductive years. Preeclampsia, the most severe hypertensive disorder of pregnancy, has been associated with an increased risk of future disease, including cardiovascular and kidney diseases. Cellular senescence, the process of cell cycle arrest in response to many physiologic and maladaptive stimuli, may play an important role in the pathogenesis of preeclampsia and provide a mechanistic link to future disease. In this article, we will discuss the pathophysiology of preeclampsia, the many mechanisms of cellular senescence, evidence for the involvement of senescence in the development of preeclampsia, as well as evidence that cellular senescence may link preeclampsia to the risk of future disease. Lastly, we will explore how a better understanding of the role of cellular senescence in preeclampsia may lead to therapeutic trials. © 2023 American Physiological Society. Compr Physiol 13:5077-5114, 2023.

Sex- and age-related differences in renal and cardiac injury and senescence in stroke-prone spontaneously hypertensive rats

BACKGROUND

Sex differences play a critical role in the incidence and severity of cardiovascular diseases, whereby men are at a higher risk of developing cardiovascular disease compared to age-matched premenopausal women. Marked sex differences at the cellular and tissue level may contribute to susceptibility to cardiovascular disease and end-organ damage. In this study, we have performed an in-depth histological analysis of sex differences in hypertensive cardiac and renal injury in middle-aged stroke-prone spontaneously hypertensive rats (SHRSPs) to determine the interaction between age, sex and cell senescence.

METHODS

Kidneys, hearts and urine samples were collected from 6.5- and 8-month-old (Mo) male and female SHRSPs. Urine samples were assayed for albumin and creatinine content. Kidneys and hearts were screened for a suite of cellular senescence markers (senescence-associated β-galactosidase, p16^INK4a, p21, γH2AX). Renal and cardiac fibrosis was quantified using Masson's trichrome staining, and glomerular hypertrophy and sclerosis were quantified using Periodic acid-Schiff staining.

RESULTS

Marked renal and cardiac fibrosis, concomitant with albuminuria, were evident in all SHRSPs. These sequelae were differentially affected by age, sex and organ. That is, the level of fibrosis was greater in the kidney than the heart, males had greater levels of fibrosis than females in both the heart and kidney, and even a 6-week increase in age resulted in greater levels of kidney fibrosis in males. The differences in kidney fibrosis were reflected by elevated levels of cellular senescence in the kidney in males but not females. Senescent cell burden was significantly less in cardiac tissue compared to renal tissue and was not affected by age or sex.

CONCLUSIONS

Our study demonstrates a clear sex pattern in age-related progression of renal and cardiac fibrosis and cellular senescence in SHRSP rats. A 6-week time frame was associated with increased indices of cardiac and renal fibrosis and cellular senescence in male SHRSPs. Female SHRSP rats were protected from renal and cardiac damage compared to age-matched males. Thus, the SHRSP is an ideal model to investigate the effects of sex and aging on organ injury over a short timeframe.

Hypertension and cellular senescence

Essential or primary hypertension is a wordwide health problem. Elevated blood pressure (BP) is closely associated not only with increased chronological aging but also with biological aging. There are various common pathways that play a role in cellular aging and BP regulation. These include but not limited to inflammation, oxidative stress, mitochondrial dysfunction, air pollution, decreased klotho activity increased renin angiotensin system activation, gut dysbiosis etc. It has already been shown that some anti-hypertensive drugs have anti-senescent actions and some senolytic drugs have BP lowering effects. In this review, we have summarized the common mechanisms underlying cellular senescence and HT and their relationships. We further reviewed the effect of various antihypertensive medications on cellular senescence and suggest further issues to be studied.

Cellular senescence: the good, the bad and the unknown

Cellular senescence is a ubiquitous process with roles in tissue remodelling, including wound repair and embryogenesis. However, prolonged senescence can be maladaptive, leading to cancer development and age-related diseases. Cellular senescence involves cell-cycle arrest and the release of inflammatory cytokines with autocrine, paracrine and endocrine activities. Senescent cells also exhibit morphological alterations, including flattened cell bodies, vacuolization and granularity in the cytoplasm and abnormal organelles. Several biomarkers of cellular senescence have been identified, including SA-βgal, p16 and p21; however, few markers have high sensitivity and specificity. In addition to driving ageing, senescence of immune and parenchymal cells contributes to the development of a variety of diseases and metabolic disorders. In the kidney, senescence might have beneficial roles during development and recovery from injury, but can also contribute to the progression of acute kidney injury and chronic kidney disease. Therapies that target senescence, including senolytic and senomorphic drugs, stem cell therapies and other interventions, have been shown to extend lifespan and reduce tissue injury in various animal models. Early clinical trials confirm that senotherapeutic approaches could be beneficial in human disease. However, larger clinical trials are needed to translate these approaches to patient care.

Extracellular Vesicles as Theranostic Tools in Kidney Disease

Extracellular vesicles are important vectors for cell-cell communication and show potential value for diagnosis and treatment of kidney diseases. The pathologic diagnosis of kidney diseases relies on kidney biopsy, whereas collection of extracellular vesicles from urine or circulating blood may constitute a less invasive diagnostic tool. In particular, urinary extracellular vesicles released mainly from resident kidney cells might provide an alternative tool for detection of kidney injury. Because extracellular vesicles mirror many features of their parent cells, cargoes of several populations of urinary extracellular vesicles are promising biomarkers for disease processes, like diabetic kidney disease, kidney transplant, and lupus nephritis. Contrarily, extracellular vesicles derived from reparative cells, such as mesenchymal stem cells, tubular epithelial progenitor cells, and human umbilical cord blood represent promising regenerative tools for treatment of kidney diseases. Furthermore, induced pluripotent stem cells-derived and engineered extracellular vesicles are being developed for specific applications for the kidney. Nevertheless, some assumptions regarding the specificity and immunogenicity of extracellular vesicles remain to be established. This review focuses on the utility of extracellular vesicles as therapeutic and diagnostic (theranostic) tools in kidney diseases and future directions for studies.

Diagnostic and Therapeutic Roles of Extracellular Vesicles in Aging-Related Diseases

Aging shows a decline in overall physical function, and cellular senescence is the powerful catalyst leading to aging. Considering that aging will be accompanied with the emergence of various aging-related diseases, research on new antiaging drugs is still valuable. Extracellular vesicles (EVs), as tools for intercellular communication, are important components of the senescence-associated secretory phenotype (SASP), and they can play pathological roles in the process of cellular senescence. In addition, EVs are similar to their original cells in functions. Therefore, EVs derived from pathological tissues or body fluids may be closely related to the progression of diseases and become potential biomarkers, while those from healthy cells may have therapeutic effects. Moreover, EVs are satisfactory drug carriers. At present, numerous studies have supported the idea that engineered EVs could improve drug targeting ability and utilization efficiency. Here, we summarize the characteristics of EVs and cellular senescence and focus on the diagnostic and therapeutic potential of EVs in various aging-related diseases, including Alzheimer disease, osteoporosis, cardiovascular disease, diabetes mellitus and its complications, and skin aging.

Exfoliated Kidney Cells from Urine for Early Diagnosis and Prognostication of CKD: The Way of the Future?

Chronic kidney disease (CKD) is a global health issue, affecting more than 10% of the worldwide population. The current approach for formal diagnosis and prognostication of CKD typically relies on non-invasive serum and urine biomarkers such as serum creatinine and albuminuria. However, histological evidence of tubulointerstitial fibrosis is the 'gold standard' marker of the likelihood of disease progression. The development of novel biomedical technologies to evaluate exfoliated kidney cells from urine for non-invasive diagnosis and prognostication of CKD presents opportunities to avoid kidney biopsy for the purpose of prognostication. Efforts to apply these technologies more widely in clinical practice are encouraged, given their potential as a cost-effective approach, and no risk of post-biopsy complications such as bleeding, pain and hospitalization. The identification of biomarkers in exfoliated kidney cells from urine via western blotting, enzyme-linked immunosorbent assay (ELISA), immunofluorescence techniques, measurement of cell and protein-specific messenger ribonucleic acid (mRNA)/micro-RNA and other techniques have been reported. Recent innovations such as multispectral autofluorescence imaging and single-cell RNA sequencing (scRNA-seq) have brought additional dimensions to the clinical application of exfoliated kidney cells from urine. In this review, we discuss the current evidence regarding the utility of exfoliated proximal tubule cells (PTC), podocytes, mesangial cells, extracellular vesicles and stem/progenitor cells as surrogate markers for the early diagnosis and prognostication of CKD. Future directions for development within this research area are also identified.

Selective kidney targeting increases the efficacy of mesenchymal stromal/stem cells for alleviation of murine stenotic-kidney senescence and damage

Chronic ischemia triggers senescence in renal tubules and at least partly mediates kidney dysfunction and damage through a p16Ink4a -related mechanism. We previously showed that mesenchymal stromal/stem cells (MSCs) delivered systemically do not effectively decrease cellular senescence in stenotic murine kidneys. We hypothesized that selective MSC targeting to injured kidneys using an anti-KIM1 antibody (KIM-MSC) coating would enhance their ability to abrogate cellular senescence in murine renal artery stenosis (RAS). KIM-MSC were injected into transgenic INK-ATTAC mice, which are amenable for selective eradication of p16Ink4a+ cells, 4 weeks after induction of unilateral RAS. To determine whether KIM-MSC abolish p16Ink4a -dependent cellular senescence, selective clearance of p16Ink4a+ cells was induced in a subgroup of RAS mice using AP20187 over 3 weeks prior to KIM-MSC injection. Two weeks after KIM-MSC aortic injection, renal senescence, function, and tissue damage were assessed. KIM-MSC delivery decreased gene expression of senescence and senescence-associated secretory phenotype factors, and improved micro-MRI-derived stenotic-kidney glomerular filtration rate and perfusion. Renal fibrosis and tubular injury also improved after KIM-MSC treatment. Yet, their efficacy was slightly augmented by prior elimination of p16Ink4a+ senescent cells. Therefore, selective targeting of MSC to the injured kidney markedly improves their senolytic potency in murine RAS, despite incomplete eradication of p16+ cells. KIM-MSC may constitute a useful therapeutic strategy in chronic renal ischemic injury.

Emergent players in renovascular disease

Renovascular disease (RVD) remains a common etiology of secondary hypertension. Recent clinical trials revealed unsatisfactory therapeutic outcomes of renal revascularization, leading to extensive investigation to unravel key pathophysiological mechanisms underlying irreversible functional loss and structural damage in the chronically ischemic kidney. Research studies identified complex interactions among various players, including inflammation, fibrosis, mitochondrial injury, cellular senescence, and microvascular remodeling. This interplay resulted in a shift of our understanding of RVD from a mere hemodynamic disorder to a pro-inflammatory and pro-fibrotic pathology strongly influenced by systemic diseases like metabolic syndrome (MetS), hypertension, diabetes mellitus, and hyperlipidemia. Novel diagnostic approaches have been tested for early detection and follow-up of RVD progression, using new imaging techniques and biochemical markers of renal injury and dysfunction. Therapies targeting some of the pathological pathways governing the development of RVD have shown promising results in animal models, and a few have moved from bench to clinical research. This review summarizes evolving understanding in chronic ischemic kidney injury.

Differential and targeted vesiculation: pathologic cellular responses to elevated arterial pressure

Extracellular vesicles are small membrane-enclosed particles released during cell activation or injury. They have been investigated for several decades and found to be secreted in various diseases. Their pathogenic role is further supported by the presence of several important molecules among their cargo, including proteins, lipids, and nucleic acids. Many studies have reported enhanced and targeted extracellular vesicle biogenesis in diseases that involve chronic or transient elevation of arterial pressure resulting in endothelial dysfunction, within either the general circulatory system or specific local vascular beds. In addition, several associated pathologic processes have been studied and reported. However, the role of elevated pressure as a common pathogenic trigger across vascular domains and disease chronicity has not been previously described. This review will therefore summarize our current knowledge of the differential and targeted biogenesis of extracellular vesicles in major diseases that are characterized by elevated arterial pressure leading to endothelial dysfunction and propose a unified theory of pressure-induced extracellular vesicle-mediated pathogenesis.

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.

Roles of extracellular vesicles in the aging microenvironment and age-related diseases

Cellular senescence is a persistently hypoproliferative state with diverse stressors in a specific aging microenvironment. Senescent cells have a double-edged sword effect: they can be physiologically beneficial for tissue repair, organ growth, and body homeostasis, and they can be pathologically harmful in age-related diseases. Among the hallmarks of senescence, the SASP, especially SASP-related extracellular vesicle (EV) signalling, plays the leading role in aging transmission via paracrine and endocrine mechanisms. EVs are successful in intercellular and interorgan communication in the aging microenvironment and age-related diseases. They have detrimental effects on downstream targets at the levels of immunity, inflammation, gene expression, and metabolism. Furthermore, EVs obtained from different donors are also promising materials and tools for antiaging treatments and are used for regeneration and rejuvenation in cell-free systems. Here, we describe the characteristics of cellular senescence and the aging microenvironment, concentrating on the production and function of EVs in age-related diseases, and provide new ideas for antiaging therapy with EVs.

Higher senescence associated secretory phenotype and lower defense mediator in urinary extracellular vesicles of elders with and without Parkinson disease

Youth fountain and aging culprits are usually sought and identified in blood but not urine. Extracellular vesicles (EVs) possess parental cell properties, circulate in blood, CSF and urine, and provide paracrine and remote cell–cell communication messengers. This study investigated whether senescence‐associated secretory phenotype (SASP) and immune defense factors in EVs of urine could serve as biomarkers in elderly individuals with and without a comorbidity. Urine samples from young adults and elderly individuals with and without Parkinson disease (PD) were collected and stored at − 80 °C until studies. Urine EVs were separated from a drop-through solution and confirmed by verifying CD9, CD63, CD81 and syntenin expression. The EVs and drop-through solution were subjected to measurement of SASP cytokines and defense factors by Milliplex array assays. Many SASP cytokines and defense factors could be detected in urinary EVs but not urinary solutions. Elderly individuals (age > 60) had significantly higher levels of the SASP-associated factors IL-8, IP-10, GRO, and MCP-1 in EVs (p < 0.05). In contrast, some defense factors, IL-4, MDC and IFNα2 in EVs had significantly lower levels in elderly adults than in young adults (age < 30). Patients with and without PD exhibited a similar SASP profile in EVs but significantly lower levels of IL-10 in the EVs from patients with PD. This study used a simple device to separate urinary EVs from solution for comparisons of SASP and defense mediators between young adults and elders with and without PD. Results from this study indicate that aging signature is present in EVs circulating to urine and the signatures include higher inflammatory mediators and lower defense factors in urinary EVs but not solutions, suggesting a simple method to separate urinary EVs from solutions for searching aging mechanistic biomarkers may make prediction of aging and monitoring of anti-senolytic interventions possible.

Progressive Cellular Senescence Mediates Renal Dysfunction in Ischemic Nephropathy

BACKGROUND

Peripheral vascular diseases may induce chronic ischemia and cellular injury distal to the arterial obstruction. Cellular senescence involves proliferation arrest in response to stress, which can damage neighboring cells. Renal artery stenosis (RAS) induces stenotic-kidney dysfunction and injury, but whether these arise from cellular senescenceand their temporal pattern remain unknown.

METHODS

Chronic renal ischemia was induced in transgenic INK-ATTAC and wild type C57BL/6 mice by unilateral RAS, and kidney function (in vivo micro-MRI) and tissue damage were assessed. Mouse healthy and stenotic kidneys were analyzed using unbiased single-cell RNA-sequencing. To demonstrate translational relevance, cellular senescence was studied in human stenotic kidneys.

RESULTS

Using intraperitoneal AP20187 injections starting 1, 2, or 4 weeks after RAS, selective clearance of cells highly expressing p16^Ink4a attenuated cellular senescence and improved stenotic-kidney function; however, starting treatment immediately after RAS induction was unsuccessful. Broader clearance of senescent cells, using the oral senolytic combination dasatinib and quercetin, in C57BL/6 RAS mice was more effective in clearing cells positive for p21 (Cdkn1a) and alleviating renal dysfunction and damage. Unbiased, single-cell RNA sequencing in freshly dissociated cells from healthy and stenotic mouse kidneys identified stenotic-kidney epithelial cells undergoing both mesenchymal transition and senescence. As in mice, injured human stenotic kidneys exhibited cellular senescence, suggesting this process is conserved.

CONCLUSIONS

Maladaptive tubular cell senescence, involving upregulated p16 (Cdkn2a), p19 (Cdkn2d), and p21 (Cdkn1a) expression, is associated with renal dysfunction and injury in chronic ischemia. These findings support development of senolytic strategies to delay chronic ischemic renal injury.

Circulating Extracellular Vesicles As Biomarkers and Drug Delivery Vehicles in Cardiovascular Diseases

Extracellular vesicles (EVs) are composed of a lipid bilayer containing transmembrane and soluble proteins. Subtypes of EVs include ectosomes (microparticles/microvesicles), exosomes, and apoptotic bodies that can be released by various tissues into biological fluids. EV cargo can modulate physiological and pathological processes in recipient cells through near- and long-distance intercellular communication. Recent studies have shown that origin, amount, and internal cargos (nucleic acids, proteins, and lipids) of EVs are variable under different pathological conditions, including cardiovascular diseases (CVD). The early detection and management of CVD reduce premature morbidity and mortality. Circulating EVs have attracted great interest as a potential biomarker for diagnostics and follow-up of CVD. This review highlights the role of circulating EVs as biomarkers for diagnosis, prognosis, and therapeutic follow-up of CVD, and also for drug delivery. Despite the great potential of EVs as a tool to study the pathophysiology of CVD, further studies are needed to increase the spectrum of EV-associated applications.

microRNA-155 Is Decreased During Atherosclerosis Regression and Is Increased in Urinary Extracellular Vesicles During Atherosclerosis Progression

Background

Atherosclerosis is a chronic inflammatory disease driven by macrophage accumulation in medium and large sized arteries. Macrophage polarization and inflammation are governed by microRNAs (miR) that regulate the expression of inflammatory proteins and cholesterol trafficking. Previous transcriptomic analysis led us to hypothesize that miR-155-5p (miR-155) is regulated by conjugated linoleic acid (CLA), a pro-resolving mediator which induces regression of atherosclerosis in vivo. In parallel, as extracellular vesicles (EVs) and their miR content have potential as biomarkers, we investigated alterations in urinary-derived EVs (uEVs) during the progression of human coronary artery disease (CAD).

Methods

miR-155 expression was quantified in aortae from ApoE^−/− mice fed a 1% cholesterol diet supplemented with CLA blend (80:20, cis-9,trans-11:trans-10,cis-12 respectively) which had been previously been shown to induce atherosclerosis regression. In parallel, human polarized THP-1 macrophages were used to investigate the effects of CLA blend on miR-155 expression. A miR-155 mimic was used to investigate its inflammatory effects on macrophages and on ex vivo human carotid endarterectomy (CEA) plaque specimens (n = 5). Surface marker expression and miR content were analyzed in urinary extracellular vesicles (uEVs) obtained from patients diagnosed with unstable (n = 12) and stable (n = 12) CAD.

Results

Here, we report that the 1% cholesterol diet increased miR-155 expression while CLA blend supplementation decreased miR-155 expression in the aorta during atherosclerosis regression in vivo. CLA blend also decreased miR-155 expression in vitro in human THP-1 polarized macrophages. Furthermore, in THP-1 macrophages, miR-155 mimic decreased the anti-inflammatory signaling proteins, BCL-6 and phosphorylated-STAT-3. In addition, miR-155 mimic downregulated BCL-6 in CEA plaque specimens. uEVs from patients with unstable CAD had increased expression of miR-155 in comparison to patients with stable CAD. While the overall concentration of uEVs was decreased in patients with unstable CAD, levels of CD45+ uEVs were increased. Additionally, patients with unstable CAD had increased CD11b+ uEVs and decreased CD16+ uEVs.

Conclusion

miR-155 suppresses anti-inflammatory signaling in macrophages, is decreased during regression of atherosclerosis in vivo and is increased in uEVs from patients with unstable CAD suggesting miR-155 has potential as a prognostic indicator and a therapeutic target.

Podocyte-Released Migrasomes in Urine Serve as an Indicator for Early Podocyte Injury

Background

Levels of urinary microvesicles, which are increased during various kidney injuries, have diagnostic potential for renal diseases. However, the significance of urinary microvesicles as a renal disease indicator is dampened by the difficulty to ascertain their cell source.

Objectives

The aim of this study was to demonstrate that podocytes can release migrasomes, a unique class of microvesicle with size ranging between 400 and 2,000 nm, and the urine level of migrasomes may serve as novel non-invasive biomarker for early podocyte injury.

Method

In this study, immunofluorescence labeling, electronic microscopy, nanosite, and sequential centrifugation were used to purify and analyze migrasomes.

Results

Migrasomes released by podocytes differ from exosomes as they have different content and mechanism of release. Compared to podocytes, renal tubular cells secrete markedly less migrasomes. Moreover, secretion of migrasomes by human or murine podocytes was strongly augmented during podocyte injuries induced by LPS, puromycin amino nucleoside (PAN), or a high concentration of glucose (HG). LPS, PAN, or HG-induced podocyte migrasome release, however, was blocked by Rac-1 inhibitor. Strikingly, a higher level of podocyte migrasomes in urine was detected in mice with PAN-nephropathy than in control mice. In fact, increased urinary migrasome number was detected earlier than elevated proteinuria during PAN-nephropathy, suggesting that urinary migrasomes are a more sensitive podocyte injury indicator than proteinuria. Increased urinary migrasome number was also detected in diabetic nephropathy patients with proteinuria level <5.5 g/day.

Conclusions

Our findings reveal that podocytes release the "injury-related" migrasomes during migration and provide urinary podocyte migrasome as a potential diagnostic marker for early podocyte injury.

Extracellular vesicles: a novel window into kidney function and disease

PURPOSE OF REVIEW

There has been an increasing interest in extracellular vesicles as potential diagnostic, prognostic or therapeutic biomarkers for various kidney diseases, as extracellular vesicles mediate cell-cell or intercellular communication. This review explores the current state of knowledge regarding extracellular vesicles as a tool for examining kidney physiology and disease.

RECENT FINDINGS

Urinary extracellular vesicles may be useful as biomarkers to detect abnormal function in renal endothelial and tubular cells as well as podocytes. Recent studies suggest that urinary extracellular vesicles may facilitate early diagnosis and/or monitoring in acute kidney injury, glomerular disease, autosomal dominanat polycyst kidney disease and urinary tract malignancies. Circulating extracellular vesicles may serve as biomarkers to assess cardiovascular disease.

SUMMARY

Urinary and circulating extracellular vesicles have gained significant interest as potential biomarkers of renal diseases. Analysis of extracellular vesicles may serve as a logical diagnostic approach for nephrologists as well as provide information about disease pathophysiology.

Extracellular Vesicles in Essential Hypertension: Hidden Messengers

PURPOSE OF REVIEW

Hypertension affects about half of all Americans, yet in the vast majority of cases, the factors causing the hypertension cannot be clearly delineated. Developing a more precise understanding of the molecular pathogenesis of HTN and its various phenotypes is therefore a pressing priority. Circulating and urinary extracellular vesicles (EVs) are potential novel candidates as biomarkers and bioactivators in HTN. EVs are a heterogeneous population of small membrane fragments shed from various cell types into various body fluids. As EVs carry protein, RNA, and lipids, they also play a role as effectors and novel cell-to-cell communicators. In this review, we discuss the diagnostic, functional, and regenerative role of EVs in essential HTN and focus on EV protein and RNA cargo as the most extensively studied EV cargo.

RECENT FINDINGS

The field of EVs in HTN is still a young one and earlier studies have not used the novel EV detection tools currently available. More rigor and transparency in EV research are needed. Current data suggest that EVs represent potential novel biomarkers in HTN. EVs correlate with HTN severity and possibly end-organ damage. However, it has yet to be discerned which specific subtype(s) of EV reflects best HTN pathophysiology. Evolving studies are also showing that EVs might be novel regulators in vascular and renal tubular function and also be therapeutic. RNA in EVs has been studied in the context of hypertension, largely in the form of studies of miRNA, which are reviewed herein. Beyond miRNAs, mRNA in urinary EVs changed in response to sodium loading in humans. EVs represent promising novel biomarkers and bioactivators in essential HTN. Novel tools are being developed to apply more rigor in EV research including more in vivo models and translation to humans.

Cellular Senescence: A New Player in Kidney Injury

Kidney diseases secondary to several pathogeneses affect millions of people worldwide and have become increasingly recognized as a global public health problem. Recent evidence suggests that cellular senescence plays an important role in the pathogenesis of different forms of renal damage, including acute and chronic kidney disease, and renal transplantation. Renal senescence involves cell cycle arrest and affects several cellular pathways, manifesting in downregulation of klotho, elevated expression of cyclin-dependent kinase inhibitors, cellular telomere shortening, and oxidative stress. Furthermore, senescent cells might induce kidney injury by paracrine release of inflammatory factors. Yet, cellular senescence may be renoprotective during development and in some models of renal diseases, reflecting the yin/yang duality of cellular senescence. This review provides an overview of the role of this emerging player in renal injury, with emphasis on new findings of cellular senescence.

Increased cellular senescence in the murine and human stenotic kidney: Effect of mesenchymal stem cells

Cell stress may give rise to insuperable growth arrest, which is defined as cellular senescence. Stenotic kidney (STK) ischemia and injury induced by renal artery stenosis (RAS) may be associated with cellular senescence. Mesenchymal stem cells (MSCs) decrease some forms of STK injury, but their ability to reverse senescence in RAS remains unknown. We hypothesized that RAS evokes STK senescence, which would be ameliorated by MSCs. Mice were studied after 4 weeks of RAS, RAS treated with adipose tissue-derived MSCs 2 weeks earlier, or sham. STK senescence-associated β-galactosidase (SA-β-Gal) activity was measured. Protein and gene expression was used to assess senescence and the senescence-associated secretory phenotype (SASP), and staining for renal fibrosis, inflammation, and capillary density. In addition, senescence was assessed as p16+ and p21+ urinary exosomes in patients with renovascular hypertension (RVH) without or 3 months after autologous adipose tissue-derived MSC delivery, and in healthy volunteers (HV). In RAS mice, STK SA-β-Gal activity increased, and senescence and SASP marker expression was markedly elevated. MSCs improved renal function, fibrosis, inflammation, and capillary density, and attenuated SA-β-Gal activity, but most senescence and SASP levels remained unchanged. Congruently, in human RVH, p21+ urinary exosomes were elevated compared to HV, and only slightly improved by MSC, whereas p16+ exosomes remained unchanged. Therefore, RAS triggers renal senescence in both mice and human subjects. MSCs decrease renal injury, but only partly mitigate renal senescence. These observations support exploration of targeted senolytic therapy in RAS.

Peristenotic Collateral Circulation in Atherosclerotic Renovascular Disease: Association With Kidney Function and Response to Treatment

The significance of peristenotic collateral circulation (PCC) development around a stenotic renal artery is unknown. We tested the hypothesis that PCC is linked to loss of kidney function and recovery potential in patients with atherosclerotic renovascular disease (ARVD). Thirty-four patients with ARVD were assigned to medical-therapy with or without revascularization based on clinical indications. The PCC was visualized using multidetector computed tomography and defined relative to segmental arteries in patients with essential hypertension. PCC number before and 3 months after treatment was correlated with various renal parameters. Thirty-four stenotic kidneys from 30 patients were analyzed. PCC number correlated inversely with kidney volume. ARVD-stenotic kidneys with baseline PCC (collateral ARVD [C-ARVD], n=13) associated with elevated 24-hour urine protein and stenotic kidney vein level of tumor necrosis factor-α, lower single-kidney volume and blood flow, and greater hypoxia than in stenotic kidneys with no PCC (no collateral ARVD [NC-ARVD], n=17). Revascularization (but not medical-therapy alone) improved stenotic kidney function and reduced inflammation in both NC-ARVD and C-ARVD. In C-ARVD, revascularization also increased stenotic kidney volume, blood flow, and oxygenation to levels comparable to NC-ARVD, and induced PCC regression. However, revascularization improved systolic blood pressure, plasma renin activity, and filtration fraction only in NC-ARVD. Therefore, patients with C-ARVD have greater kidney dysfunction, atrophy, hypoxia, and inflammation compared with patients with NC-ARVD, suggesting that PCC does not effectively protect the stenotic kidney in ARVD. Renal artery revascularization improved in C-ARVD stenotic kidney function, but not hypertension or renin-angiotensin system activation. These observations may help direct management of patients with ARVD.

Urinary Extracellular Vesicles as Biomarkers of Kidney Disease: From Diagnostics to Therapeutics

Cell-derived extracellular vesicles (EVs) can be isolated from various body fluids, including urine. Urinary EVs have gained important recognition as potential diagnostic biomarkers in renal disease since their cargo includes nucleic acids, proteins, and other cellular components, which likely mirror the physiological and possibly pathophysiological state of cells along the nephron. Accumulating evidence highlights the feasibility of using EVs as biomarkers for diagnostic, prognostic, and therapeutic purposes in several forms of renal disease, such as acute kidney injury, glomerulonephritis, and renal transplantation. Additionally, exogenous delivery of EVs released in vitro by cells in culture may have salutary benefits for renal diseases. In this review, we introduce recent studies that attempt to identify urinary EVs as candidate biomarkers for human kidney diseases and consider their potential implication as a therapeutic option in key kidney diseases.

A Method to Analyze Urinary Extracellular Vesicles

Extracellular vesicles (EVs) play an important role in cell-to-cell communication by carrying molecular messages that reflect physiological and pathological conditions of the parent cells. EVs have been identified in all body fluids; and among them, urine stands out as a sample that is easy and inexpensive to obtain and can be collected over time to monitor changes. Various protocols have been established to study urinary extracellular vesicles (UEVs) and they have shown great potential as a biomarker source for clinical applications, not only for urological, but also non-urological diseases. Due to the high variability and low reproducibility of pre-analytical and analytical methods for UEVs, establishing a standardized protocol remains a challenge in the field of diagnosis. Here, we review UEV studies and present the techniques that are most commonly used, those that have been applied as new developments, and those that have the most potential for future applications. The workflow procedures from the sampling step to the qualitative and quantitative analysis steps are summarized along with advantages and disadvantages of the methodologies, in order to give consideration for choosing the most promising and suitable method to analyze human UEVs.

Using Imaging Flow Cytometry to Characterize Extracellular Vesicles Isolated from Cell Culture Media, Plasma or Urine

The ability to non-invasively detect specific damage to the kidney has been limited. Identification of extracellular vesicles released by cells, especially when under duress, might allow for monitoring and identification of specific cell types within the kidney that are stressed. We have adapted a previously published traditional flow cytometry method for use with an imaging flow cytometer (Amnis FlowSight) for identifying EV released by specific cell types and excreted into the urine or blood using markers characteristic of particular cells in the kidney. Here we present a protocol utilizing the Amnis FlowSight Imaging Flow Cytometer to identify and quantify EV from the urine of patients with essential hypertension and renovascular disease. Notably, EV isolated from cell culture media and plasma can also be analyzed similarly.