Exosomal CCL2 from Tubular Epithelial Cells Is Critical for Albumin-Induced Tubulointerstitial Inflammation

Emerging Potential of Exosomes on Adipogenic Differentiation of Mesenchymal Stem Cells

The mesenchymal stem cells have multidirectional differentiation potential and can differentiate into adipocytes, osteoblasts, cartilage tissue, muscle cells and so on. The adipogenic differentiation of mesenchymal stem cells is of great significance for the construction of tissue-engineered fat and the treatment of soft tissue defects. Exosomes are nanoscale vesicles secreted by cells and widely exist in body fluids. They are mainly involved in cell communication processes and transferring cargo contents to recipient cells. In addition, exosomes can also promote tissue and organ regeneration. Recent studies have shown that various exosomes can influence the adipogenic differentiation of stem cells. In this review, the effects of exosomes on stem cell differentiation, especially on adipogenic differentiation, will be discussed, and the mechanisms and conclusions will be drawn. The main purpose of studying the role of these exosomes is to understand more comprehensively the influencing factors existing in the process of stem cell differentiation into adipocytes and provide a new idea in adipose tissue engineering research.

Extracellular vesicle activities regulating macrophage- and tissue-mediated injury and repair responses

Macrophages are typically identified as classically activated (M1) macrophages and alternatively activated (M2) macrophages, which respectively exhibit pro- and anti-inflammatory phenotypes, and the balance between these two subtypes plays a critical role in the regulation of tissue inflammation, injury, and repair processes. Recent studies indicate that tissue cells and macrophages interact via the release of small extracellular vesicles (EVs) in processes where EVs released by stressed tissue cells can promote the activation and polarization of adjacent macrophages which can in turn release EVs and factors that can promote cell stress and tissue inflammation and injury, and vice versa. This review discusses the roles of such EVs in regulating such interactions to influence tissue inflammation and injury in a number of acute and chronic inflammatory disease conditions, and the potential applications, advantage and concerns for using EV-based therapeutic approaches to treat such conditions, including their potential role of drug carriers for the treatment of infectious diseases.

Macrophage Heterogeneity in Kidney Injury and Fibrosis

Kidney macrophages are central in kidney disease pathogenesis and have therapeutic potential in preventing tissue injury and fibrosis. Recent studies highlighted that kidney macrophages are notably heterogeneous immune cells that fulfill opposing functions such as clearing deposited pathogens, maintaining immune tolerance, initiating and regulating inflammatory responses, promoting kidney fibrosis, and degrading the extracellular matrix. Macrophage origins can partially explain macrophage heterogeneity in the kidneys. Circulating Ly6C⁺ monocytes are recruited to inflammatory sites by chemokines, while self-renewed kidney resident macrophages contribute to kidney repair and fibrosis. The proliferation of resident macrophages or infiltrating monocytes provides an alternative explanation of macrophage accumulation after kidney injury. In addition, dynamic Ly6C expression on infiltrating monocytes accompanies functional changes in handling kidney inflammation and fibrosis. Mechanisms underlying kidney macrophage heterogeneity, either by recruiting monocyte subpopulations, regulating macrophage polarization, or impacting distinctive macrophage functions, may help develop macrophage-targeted therapies for kidney diseases.

Small extracellular vesicles deliver TGF-β1 and promote adriamycin resistance in breast cancer cells

Chemotherapeutic resistance is a major obstacle in the control of advanced breast cancer (BCa). We have previously shown that small extracellular vesicles (sEVs) can transmit adriamycin resistance between BCa cells. Here, we describe that sEV-mediated TGF-β1 intercellular transfer is involved in the drug-resistant transmission. sEVs were isolated and characterized from both sensitive and resistant cells. sEVs derived from the resistant cells were incubated with the sensitive cells and resulted in transmitting the resistant phenotype to the recipient cells. Cytokine antibody microarray revealed that most metastasis-associated cytokines present at the high levels in sEVs from the resistant cells compared with their levels in sEVs from the sensitive cells, particularly TGF-β1 is enriched in sEVs from the resistant cells. The sEV-mediated TGF-β1 intercellular transfer led to increasing Smad2 phosphorylation and improving cell survival by suppressing apoptosis and enhancing cell mobility. Furthermore, sEV-mediated drug-resistant transmission by delivering TGF-β1 was validated using a zebrafish xenograft tumor model. These results elaborated that sEV-mediated TGF-β1 intercellular transfer contributes to adriamycin resistance in BCa.

Extracellular vesicles in kidneys and their clinical potential in renal diseases

Extracellular vesicles (EVs), such as exosomes and microvesicles, are cell-derived lipid bilayer membrane particles, which deliver information from host cells to recipient cells. EVs are involved in various biological processes including the modulation of the immune response, cell-to-cell communications, thrombosis, and tissue regeneration. Different types of kidney cells are known to release EVs under physiologic as well as pathologic conditions, and recent studies have found that EVs have a pathophysiologic role in different renal diseases. Given the recent advancement in EV isolation and analysis techniques, many studies have shown the diagnostic and therapeutic potential of EVs in various renal diseases, such as acute kidney injury, polycystic kidney disease, chronic kidney disease, kidney transplantation, and renal cell carcinoma. This review updates recent clinical and experimental findings on the role of EVs in renal diseases and highlights the potential clinical applicability of EVs as novel diagnostics and therapeutics.

Extracellular Vesicles and Renal Fibrosis: An Odyssey toward a New Therapeutic Approach

Renal fibrosis is a complex disorder characterized by the destruction of kidney parenchyma. There is currently no cure for this devastating condition. Extracellular vesicles (EVs) are membranous vesicles released from cells in both physiological and diseased states. Given their fundamental role in transferring biomolecules to recipient cells and their ability to cross biological barriers, EVs have been widely investigated as potential cell-free therapeutic agents. In this review, we provide an overview of EVs, focusing on their functional role in renal fibrosis and signaling messengers responsible for EV-mediated crosstalk between various renal compartments. We explore recent findings regarding the renoprotective effect of EVs and their use as therapeutic agents in renal fibrosis. We also highlight advantages and future perspectives of the therapeutic applications of EVs in renal diseases.

Potential role of extracellular vesicles in the pathophysiology of glomerular diseases

Extracellular vesicles (EVs) are membrane-bound vesicles released by most cells and are found in diverse biological fluids. The release of EVs provides a new mechanism for intercellular communication, allowing cells to transfer their functional cargoes to target cells. Glomerular diseases account for a large proportion of end-stage renal disease (ESRD) worldwide. In recent years, an increasing number of research groups have focused their effort on identifying the functional role of EVs in renal diseases. However, the involvement of EVs in the pathophysiology of glomerular diseases has not been comprehensively described and discussed. In this review, we first briefly introduce the characteristics of EVs. Then, we describe the involvement of EVs in the mechanisms underlying glomerular diseases, including immunological and fibrotic processes. We also discuss what functions EVs derived from different kidney cells have in glomerular diseases and how EVs exert their effects through different signaling pathways. Furthermore, we summarize recent advances in the knowledge of EV involvement in the pathogenesis of various glomerular diseases. Finally, we propose future research directions for identifying better management strategies for glomerular diseases.

Role of serum CXCL9 and CXCL13 in predicting infection after kidney transplant: A STROBE study

Chemokines are majorly involved in inflammatory and immune responses. The interferon-γ-inducible chemokines C-X-C motif chemokines 9 and 10 (CXCL9 and CXCL10) are considerably associated with Th1 cells and monocytes, and their expression levels rapidly increase during the early episodes of renal allograft rejection and various infectious diseases. CXCL13 is one of the most potent B-cell and T follicular helper-cell chemoattractants. The expression of CXCL13 in the presence of infection indicates an important chemotactic activity in multiple infectious diseases. C-C motif chemokine ligand 2 (CCL2) can attract monocytes and macrophages during inflammatory responses. However, there are no studies on the role of these chemokines in posttransplant infection in kidney transplant recipients.In this study, CXCL9, CXCL10, CXCL13, and CCL2 were analyzed using the Bio-Plex suspension array system before transplant and 30 days after transplant.The serum levels of CXCL9 and CXCL13 30 days after kidney transplant were associated with infection within 1 year after transplant (P = .021 and P = .002, respectively). The serum levels of CXCL9 and CXCL13 before surgery and those of CCL2 and CXCL10 before and after surgery were not associated with infection within 1 year after transplant (P > .05). The combination of postoperative day (POD) 30 CXCL9 and postoperative day 30 CXCL13 provided the best results with an area under the curve of 0.721 (95% confidence interval, 0.591-0.852), with a sensitivity of 71.4% and specificity of 68.5% at the optimal cutoff value of 52.72 pg/mL.As important chemokines, CXCL9 and CXCL13 could be used to predict the occurrence of infection after kidney transplant.

Determining the influence of high glucose on exosomal lncRNAs, mRNAs, circRNAs and miRNAs derived from human renal tubular epithelial cells

Diabetic nephropathy is a lethal disease that can lead to chronic kidney disease and end-stage kidney disease. Exosomes, which are nanosized extracellular vesicles, are closely involved in intercellular communication. Most importantly, exosomes play critical roles in disease occurrence and development. However, the function of exosomes in diabetic nephropathy progression has not been fully elucidated. In the present study, we determined the expression profiles and differences of lncRNAs, mRNAs, circRNAs and miRNAs in exosomes derived from human renal tubular epithelial cells with or without high glucose (HG) treatment. A total of 169 lncRNAs, 885 mRNAs, 3 circRNAs and 152 miRNAs were differentially expressed in exosomes secreted by HG-challenged HK-2 cells (HG group) compared with controls (NC group). The functions of differentially expressed mRNAs, mRNAs colocalized or coexpressed with differentially expressed lncRNAs (DElncRNAs), potential target genes of miRNAs and source genes of circRNAs were investigated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis.

According to these differentially expressed RNAs, we established an integrated circRNA-lncRNA-miRNA-mRNA regulatory network. In conclusion, our study suggested that exosomal lncRNAs, mRNAs, circRNAs and miRNAs participate in the progression of diabetic nephropathy and may be possible biomarkers and therapeutic targets in diabetic nephropathy.

Macrophage interactions with collecting duct epithelial cells are capable of driving tubulointerstitial inflammation and fibrosis in immunoglobulin A nephropathy

BACKGROUND

Tubulointerstitial fibrosis is a powerful predictor of future progression inimmunoglobulin A (IgA) nephropathy (IgAN). Proximal tubular epithelial cells (PTECs), in concert with infiltrating macrophages, are regarded as the agents provocateurs for driving this fibrotic process. However, evidence is now emerging for a contributory role of the distal nephron. The aim of this study was to examine the potential influence of macrophages on collecting duct epithelial cells (CDECs) and their combined role in the progression of IgAN.

METHODS

CDECs were cultured with macrophage-conditioned media (MCM) generated from human monocyte cell lines U937 and THP-1 stimulated with or without 100 μg/mL galactose-deficient IgA1. CDECs were analysed for evidence of inflammation and fibrosis.

RESULTS

Staining of IgAN biopsies for CD68+ macrophages revealed the presence of macrophages juxtaposed to collecting ducts and within their lumina. CDEC exposed to MCM from IgA1-stimulated THP-1 cells (THP-1-IgA-MCM) exhibited markedly increased expression of neutrophil-associated gelatinase (NGAL) and proinflammatory cytokinesinterleukin (IL)-1β, tumour necrosis factor-α, IL-6 and IL-8 compared with MCM from non-IgA-stimulated THP-1 cells (THP-1-MCM). U937-IgA-MCM increased fibronectin levels and reduced E-cadherinmRNA expression. THP-1-IgA-MCM-derived exosomes induced similar increases in NGAL and cytokine expression while in cross-over experiments exosomes extracted from IL-1β-exposed CDEC induced IL-1β and IL-6 mRNA expression in both sets of macrophages. MiRnome analysis revealed that microRNA (miR)-146a, -155 and -200b exhibited a >2-fold increase in expression in CDEC treated with THP-1-IgA-MCM compared with THP-1-MCM. Enforced miR-146a suppression further enhanced NGAL expression, while ectopic miR-146a over-expression downregulated it. NGAL mRNA and miR-146a were upregulated in the biopsies of patients with progressive IgAN compared with non-progressive IgAN.

CONCLUSIONS

Taken together, these data suggest that CDEC-macrophage interactions potentially contribute to the tubulointerstitial fibrosis characteristic of progressive IgAN.

Molecular and functional profiling of apical versus basolateral small extracellular vesicles derived from primary human proximal tubular epithelial cells under inflammatory conditions

Proximal tubular epithelial cells (PTEC) are central players in inflammatory kidney diseases. However, the complex signalling mechanism/s via which polarized PTEC mediate disease progression are poorly understood. Small extracellular vesicles (sEV), including exosomes, are recognized as fundamental components of cellular communication and signalling courtesy of their molecular cargo (lipids, microRNA, proteins). In this study, we examined the molecular content and function of sEV secreted from the apical versus basolateral surfaces of polarized human primary PTEC under inflammatory diseased conditions. PTEC were cultured under normal and inflammatory conditions on Transwell inserts to enable separate collection and isolation of apical/basolateral sEV. Significantly increased numbers of apical and basolateral sEV were secreted under inflammatory conditions compared with equivalent normal conditions. Multi‐omics analysis revealed distinct molecular profiles (lipids, microRNA, proteins) between inflammatory and normal conditions for both apical and basolateral sEV. Biological pathway analyses of significantly differentially expressed molecules associated apical inflammatory sEV with processes of cell survival and immunological disease, while basolateral inflammatory sEV were linked to pathways of immune cell trafficking and cell‐to‐cell signalling. In line with this mechanistic concept, functional assays demonstrated significantly increased production of chemokines (monocyte chemoattractant protein‐1, interleukin‐8) and immuno‐regulatory cytokine interleukin‐10 by peripheral blood mononuclear cells activated with basolateral sEV derived from inflammatory PTEC. We propose that the distinct molecular composition of sEV released from the apical versus basolateral membranes of human inflammatory PTEC may reflect specialized functional roles, with basolateral‐derived sEV pivotal in modulating tubulointerstitial inflammatory responses observed in many immune‐mediated kidney diseases. These findings provide a rationale to further evaluate these sEV‐mediated inflammatory pathways as targets for biomarker and therapeutic development.

Quercetin alleviates acute kidney injury by inhibiting ferroptosis

INTRODUCTION

Ferroptosis is an iron-dependent regulated necrosis and has been proven to contribute to the progress of acute kidney injury (AKI). Quercetin (QCT), a natural flavonoid which is commonly found in numerous fruits and vegetables, has extensive pharmacological effects, such as anti-oxidant, anti-inflammatory and anti-senescence effects.

OBJECTIVES

This study aims to explain whether ferroptosis is a therapeutic strategy to AKI, and to explore the effect of QCT on AKI ferroptosis.

METHODS

NRK-52E cells and HK-2 cells were used for in vitro ferroptosis studies. Morphology of cells was detected by transmission electron microscopy. Lipid ROS was assayed using flow cytometry. In vivo, AKI was induced by ischemia-reperfusion (I/R) or folic acid (FA). To explore the molecular mechanisms, RNA-sequence analysis was performed. Transwell was used to detect macrophage migration.

RESULTS

We discovered that quercetin (QCT), a natural flavonoid, inhibited ferroptosis in renal proximal tubular epithelial cells. QCT blocked the typical morphologic changes of ferroptotic cells by reducing the levels of malondialdehyde (MDA) and lipid ROS and increasing the levels of glutathione (GSH). Moreover, QCT ameliorated AKI induced by I/R or FA. RNA-sequence analysis highlighted activation transcription factor 3 (ATF3), as it was the dominant one among all the 299 down-regulated genes by QCT. Knockdown of ATF3 could significantly increase the levels of SLC7A11, GPX4 and increased the cell viability. In addition, ferroptotic cells were found to be extremely pro-inflammatory by recruiting macrophages through CCL2, while QCT inhibited the chemotaxis of macrophages induced by ferroptosis in AKI.

CONCLUSIONS

Collectively, these results identify QCT as a ferroptosis inhibitor and provide new therapeutic strategies for diseases related to ferroptosis.

Epigenetic modifications and the development of kidney graft fibrosis

PURPOSE OF REVIEW

To outline recent discoveries in epigenetic regulatory mechanisms that have potential implications in the development of renal fibrosis following kidney transplantation.

RECENT FINDINGS

The characterization of renal fibrosis following kidney transplantation has shown TGFβ/Smad signaling to play a major role in the progression to chronic allograft dysfunction. The onset of unregulated proinflammatory pathways are only exacerbated by the decline in regulatory mechanisms lost with progressive patient age and comorbidities such as hypertension and diabetes. However, significant developments in the recognition of epigenetic regulatory markers upstream of aberrant TGFβ-signaling has significant clinical potential to provide therapeutic targets for the treatment of renal fibrosis. In addition, discoveries in extracellular vesicles and the characterization of their cargo has laid new framework for the potential to evaluate patient outcomes independent of invasive biopsies.

SUMMARY

The current review summarizes the main findings in epigenetic machinery specific to the development of renal fibrosis and highlights therapeutic options that have significant potential to translate into clinical practice.

Mesenchymal Stem Cell-Derived Extracellular Vesicles Attenuate Mitochondrial Damage and Inflammation by Stabilizing Mitochondrial DNA

Mitochondrial dysfunction is a key feature of injury to numerous tissues and stem cell aging. Although the tissue regenerative role of mesenchymal stem cell (MSC)-derived extracellular vesicles (MSC-EVs) is well known, their specific role in regulating mitochondrial function in target cells remains elusive. Here, we report that MSC-EVs attenuated mtDNA damage and inflammation after acute kidney injury (AKI) and that this effect was at least partially dependent on the mitochondrial transcription factor A (TFAM) pathway. In detail, TFAM and mtDNA were depleted by oxidative stress in MSCs from aged or diabetic donors. Higher levels of TFAM mRNA and mtDNA were detected in normal control (NC) MSC-EVs than in TFAM-knockdown (TFAM-KD) and aged EVs. EV-mediated TFAM mRNA transfer in recipient cells was unaffected by transcriptional inhibition. Accordingly, the application of MSC-EVs restored TFAM protein and TFAM-mtDNA complex (nucleoid) stability, thereby reversing mtDNA deletion and mitochondrial oxidative phosphorylation (OXPHOS) defects in injured renal tubular cells. Loss of TFAM also led to downregulation of multiple anti-inflammatory miRNAs and proteins in MSC-EVs. In vivo, intravenously injected EVs primarily accumulated in the liver, kidney, spleen, and lung. MSC-EVs attenuated renal lesion formation, mitochondrial damage, and inflammation in mice with AKI, whereas EVs from TFAM-KD or aged MSCs resulted in poor therapeutic outcomes. Moreover, TFAM overexpression (TFAM-OE) improved the rescue effect of MSC-EVs on mitochondrial damage and inflammation to some extent. This study suggests that MSC-EVs are promising nanotherapeutics for diseases characterized by mitochondrial damage, and TFAM signaling is essential for maintaining their regenerative capacity.

Dual and Opposite Costimulatory Targeting with a Novel Human Fusion Recombinant Protein Effectively Prevents Renal Warm Ischemia Reperfusion Injury and Allograft Rejection in Murine Models

Many studies have shown both the CD28-D80/86 costimulatory pathway and the PD-1-PD-L1/L2 coinhibitory pathway to be important signals in modulating or decreasing the inflammatory profile in ischemia-reperfusion injury (IRI) or in a solid organ transplant setting. The importance of these two opposing pathways and their potential synergistic effect led our group to design a human fusion recombinant protein with CTLA4 and PD-L2 domains named HYBRI. The objective of our study was to determine the HYBRI binding to the postulated ligands of CTLA4 (CD80) and PD-L2 (PD-1) using the Surface Plasmon Resonance technique and to evaluate the in vivo HYBRI effects on two representative kidney inflammatory models-rat renal IRI and allogeneic kidney transplant. The Surface Plasmon Resonance assay demonstrated the avidity and binding of HYBRI to its targets. HYBRI treatment in the models exerted a high functional and morphological improvement. HYBRI produced a significant amelioration of renal function on day one and two after bilateral warm ischemia and on days seven and nine after transplant, clearly prolonging the animal survival in a life-sustaining renal allograft model. In both models, a significant reduction in histological damage and CD3 and CD68 infiltrating cells was observed. HYBRI decreased the circulating inflammatory cytokines and enriched the FoxP3 peripheral circulating, apart from reducing renal inflammation. In conclusion, the dual and opposite costimulatory targeting with that novel protein offers a good microenvironment profile to protect the ischemic process in the kidney and to prevent the kidney rejection, increasing the animal's chances of survival. HYBRI largely prevents the progression of inflammation in these rat models.

Effects of Chronic Kidney Disease and Uremic Toxins on Extracellular Vesicle Biology

Vascular calcification (VC) is a cardiovascular complication associated with a high mortality rate, especially in patients with diabetes, atherosclerosis or chronic kidney disease (CKD). In CKD patients, VC is associated with the accumulation of uremic toxins, such as indoxyl sulphate or inorganic phosphate, which can have a major impact in vascular remodeling. During VC, vascular smooth muscle cells (VSMCs) undergo an osteogenic switch and secrete extracellular vesicles (EVs) that are heterogeneous in terms of their origin and composition. Under physiological conditions, EVs are involved in cell-cell communication and the maintenance of cellular homeostasis. They contain high levels of calcification inhibitors, such as fetuin-A and matrix Gla protein. Under pathological conditions (and particularly in the presence of uremic toxins), the secreted EVs acquire a pro-calcifying profile and thereby act as nucleating foci for the crystallization of hydroxyapatite and the propagation of calcification. Here, we review the most recent findings on the EVs’ pathophysiological role in VC, the impact of uremic toxins on EV biogenesis and functions, the use of EVs as diagnostic biomarkers and the EVs’ therapeutic potential in CKD.

Exosomal MicroRNA-374b-5p From Tubular Epithelial Cells Promoted M1 Macrophages Activation and Worsened Renal Ischemia/Reperfusion Injury

Tubular epithelial cells (TECs) represent the primary site of renal ischemia/reperfusion injury (RIRI). However, whether the damage of TECs could drive the initiation of inflammation was unclear. Here we investigated the role of the TECs and macrophages during RIRI. Increased expression of inflammation response and activated M1 macrophage were determined in the mice model of RIRI. Moreover, we demonstrated global miRNA expression profiling of renal exosomes, and miR-374b-5p was most upregulated in these exosomes in vivo. Inhibition of miR-374b-5p in the mice upon RIR operation would alleviate the kidney injury via decreasing the production of proinflammatory cytokines and suppressing the macrophage activation. Similar results were also identified in the hypoxia-induced cell model where exosomal miR-374b-5p was dramatically upregulated. Uptake of exosomes derived from the hypoxic TECs by macrophages would trigger M1 polarization via transferring miR-374b-5p. Besides, we confirmed that miR-374b-5p could directly bind to Socs1 using a dual-luciferase reporter assay. Notably, when we injected the miR-374b-5p-enriched exosomes into mice, a high-level inflammatory response and M1 macrophage activation were performed. Our studies demonstrated that exosomal miR-374b-5p played an essential role in the communication between injured TECs and macrophages, resulting in the M1 macrophage activation during RIRI. The blockage of the release of such exosomes may serve as a new therapeutic strategy for RIRI.

Therapeutic Potential of Extracellular Vesicles in Hypertension-Associated Kidney Disease

Hypertension-mediated organ damage frequently includes renal function decline in which several mechanisms are involved. The present review outlines the state of the art on extracellular vesicles in hypertension and hypertension-related renal damage. Emerging evidence indicates that extracellular vesicles, small vesicles secreted by most cell types and body fluids, are involved in cell-to-cell communication and are key players mediating biological processes such as inflammation, endothelial dysfunction or fibrosis, mechanisms present the onset and progression of hypertension-associated kidney disease. We address the potential use of extracellular vesicles as markers of hypertension-mediated kidney damage severity and their application as therapeutic agents in hypertension-associated renal damage. The capacity of exosomes to deliver a wide variety of cargos to the target cell efficiently makes them a potential drug delivery system for treatment of renal diseases.

Fe3O4 magnetic nanoparticles ameliorate albumin-induced tubulointerstitial fibrosis by autophagy related to Rab7

Albuminuria is a primary feature in patients with CKD and an important contributor to tubulointerstitial fibrosis (TIF) development. Autophagy has been considered to be involved in renal tubular injury caused by albuminuria. Fe₃O₄ magnetic nanoparticles are related to many cellular activities, such as autophagy and inflammation. Rab7, a molecule involved in both endocytosis and autophagy, has been identified to protect renal tubular epithelial cells from albumin by regulating autophagy and MMP-2 activity in the early stage of albumin stimulation, but its role in the advanced stage is still unclear. Therefore, to investigate the effect of Fe₃O₄ magnetic nanoparticles on chronic renal tubular injury induced by excess albumin and to further determine the specific role of Rab7, we established a mouse model of TIF by intravenous injection of cationic bovine serum albumin (C-BSA) in Rab7-overexpressing transgenic mice. Our data revealed the decreased autophagy level, weakened MMP-2 activity and exacerbated renal tubular injury in these BSA-overloaded mice; furthermore, the degree of injury was more serious in Rab7-overexpressing transgenic mice. However, the application of Fe₃O₄ magnetic albumin nanoparticles (Fe₃O₄@BSA) enhanced MMP-2 activity and alleviated renal tubular injury, and these changes were mediated by an autophagy-dependent mechanism. Taken together, our results indicated that long-term albumin stimulation combined with overexpression of Rab7 could further decrease MMP-2 activity, exacerbate renal tubular injury and accelerate the development of TIF. Fe₃O₄@BSA could be a promising targeted tool for the management of CKD patients.

Analysis on the expression and value of CCL2 and CCL3 in patients with osteoarthritis

In this study, we investigated the clinical value of CC chemokine ligand 2 (CCL2) and CC chemokine ligand 3 (CCL3) in osteoarthritis (OA). A prospective analysis was performed on 126 patients with rheumatoid arthritis of the knee (observation group (OG)) who admitted to Qilu hospital from August 2016 to August 2018 and 135 healthy controls (control group (CG)) who underwent physical examinations during the same period. The concentrations of CCL2 and CCL3 in peripheral blood were compared between the two groups, and the predictive value of the two on the occurrence, efficacy and prognosis of recurrence of OA were analyzed. In addition, an OA rat model was established to detect the relative protein levels of CCL2 and CCL3 in rat knee joint tissues. There were no statistically significant differences between the two groups in baseline data such as age, body mass index (BMI), gender, smoking, drinking, educational level, family medical history and living environment (P > 0.05). CCL2 and CCL3 increased in peripheral blood of patients in the OG (P < 0.05), both of which were positively correlated with rheumatoid factor (RF) (P < 0.001). CCL2 and CCL3 were of good predictive value for the occurrence, efficacy and prognosis of recurrence of OA (P < 0.001). The relative protein levels of CCL2 and CCL3 in bone and joint tissues of OA rats were significantly higher than those of normal rats (P < 0.001). CCL2 and CCL3 are elevated in peripheral blood of OA patients, which have good predictive value for the occurrence, efficacy and prognosis of recurrence of OA, indicating their potential roles as excellent markers for diagnosis and treatment of OA in the future.

Personal exposure to fine particulate matter and renal function in children: A panel study

There is a lack of evidence regarding the association of short-term exposure to fine particulate matter (PM_2.5) with renal function in children and its underlying mechanism. We included 105 children aged 4-13 years from a panel study conducted in Wuhan, China with up to 3 repeated visits across 3 seasons from October 9, 2017 to June 1, 2018. We measured personal real-time PM_2.5 exposure concentration continuously for 72 h preceding each round of health examinations that included serum creatinine and cytokines. Linear mixed-effects models were performed to estimate the effects of PM_2.5 on estimated glomerular filtration rate (eGFR) over various lag times, and a mediation analysis was applied for the role of cytokines in association between PM_2.5 and eGFR. Results showed that personal exposure to PM_2.5 was dose-responsive related to decreased eGFR within lag 2 days. The effect was the strongest at lag 0 day with estimation of -1.69% [95% confidence interval (CI): -2.27%, -1.10%] in eGFR by a 10-μg/m³ increase in PM_2.5, and reached peak at lag 3 h, then declined over time. Such inverse relationships were more evident among children aged 4-6 years, or boys or those who lived proximity to major roadways <300 m. Notably, eGFR still held on to decrease even when PM_2.5 was below Class II Chinese ambient air quality standard at lag 0 day. Moreover, the effect of PM_2.5 on eGFR was significantly reduced in children with high and medium levels of serum chemokine ligand 27 (CCL27), but not in those with low CCL27. Furthermore, CCL27 was positively relevant to PM_2.5, and mediated proportion of CCL27 ranged from 3.75% to 6.61% in relations between PM_2.5 and decreased eGFR over various lag times. In summary, short-term PM_2.5 exposure might be dose-responsive associated with reduced eGFR whereby a mechanism partly involving CCL27 among healthy children.

Diagnostic roles of urinary kidney microvesicles in diabetic nephropathy

Background

The pathology of diabetic nephropathy (DN) broadly involves the injury of glomeruli, tubulointerstitium and endothelium. Cells from these compartments can release increased numbers of microvesicles (MVs) into urine when stressed or damaged. Currently whether urinary MVs from these three parts can help diagnose DN and reflect pathological features remain unclear.

Methods

Forty-nine patients with histologically proven DN and 29 proteinuric controls with membranous nephropathy or minimal change disease were enrolled. Urinary podocyte, proximal tubular and endothelial cell-derived MVs were quantified by flow cytometry. Renal glomerular, tubulointerstitial and vascular lesions were semi-quantitatively scored and their relevance to urinary MVs were analyzed.

Results

DN patients had greater numbers of urinary MVs from podocytes, proximal tubular and endothelial cells compared with proteinuric controls. The combination of podocyte nephrin+ MVs and diabetic retinopathy optimally diagnose DN with 89.7% specificity and 88.9% sensitivity. Moreover, positive correlations were observed between urinary levels of proximal tubular MVs and the severity of tubular injury and between urinary levels of endothelial MVs and the degree of vascular injury. Using urinary proximal tubular MVs as the indicators for tubular injury, the differences between DN patients and proteinuric controls diminished after matching the degree of renal vascular injury or when proteinuria >8 g/24 h.

Conclusions

Urinary kidney-specific cell-derived MVs might serve as noninvasive biomarkers for the diagnosis of DN in diabetic proteinuric patients. Their elevated levels could reflect corresponding renal pathological lesions, helping physicians look into the heterogeneity of DN.

Molecular and Functional Diversity of Distinct Subpopulations of the Stressed Insulin-Secreting Cell's Vesiculome

Beta cell failure and apoptosis following islet inflammation have been associated with autoimmune type 1 diabetes pathogenesis. As conveyors of biological active material, extracellular vesicles (EV) act as mediators in communication with immune effectors fostering the idea that EV from inflamed beta cells may contribute to autoimmunity. Evidence accumulates that beta exosomes promote diabetogenic responses, but relative contributions of larger vesicles as well as variations in the composition of the beta cell's vesiculome due to environmental changes have not been explored yet. Here, we made side-by-side comparisons of the phenotype and function of apoptotic bodies (AB), microvesicles (MV) and small EV (sEV) isolated from an equal amount of MIN6 beta cells exposed to inflammatory, hypoxic or genotoxic stressors. Under normal conditions, large vesicles represent 93% of the volume, but only 2% of the number of the vesicles. Our data reveal a consistently higher release of AB and sEV and to a lesser extent of MV, exclusively under inflammatory conditions commensurate with a 4-fold increase in the total volume of the vesiculome and enhanced export of immune-stimulatory material including the autoantigen insulin, microRNA, and cytokines. Whilst inflammation does not change the concentration of insulin inside the EV, specific Toll-like receptor-binding microRNA sequences preferentially partition into sEV. Exposure to inflammatory stress engenders drastic increases in the expression of monocyte chemoattractant protein 1 in all EV and of interleukin-27 solely in AB suggesting selective sorting toward EV subspecies. Functional in vitro assays in mouse dendritic cells and macrophages reveal further differences in the aptitude of EV to modulate expression of cytokines and maturation markers. These findings highlight the different quantitative and qualitative imprints of environmental changes in subpopulations of beta EV that may contribute to the spread of inflammation and sustained immune cell recruitment at the inception of the (auto-) immune response.

The Monocyte-Derived Exosomal CLMAT3 Activates the CtBP2-p300-NF-κB Transcriptional Complex to Induce Proinflammatory Cytokines in ALI

Monocytes and macrophages are the two major cell types involved in innate immunity. Exosomes act as signaling molecules to regulate cell-to-cell communication by releasing proteins, mRNAs, microRNAs (miRNAs), and long noncoding RNAs (lncRNAs). However, it is still unclear whether monocyte-derived exosomes are involved in the communication between monocytes and macrophages. In this study, we analyzed the differentially expressed lncRNA profiles in monocytes isolated from blood samples of healthy controls and acute lung injury (ALI) patients. We focused our study on investigating the signaling downstream of CLMAT3 (colorectal liver metastasis-associated transcript 3), a lncRNA that regulated proinflammatory cytokine genes. We revealed that CLMAT3 specifically targeted CtBP2 (C-terminal binding protein 2) and repressed its expression. Elevated CtBP2 acted as a coactivator to assemble a transcriptional complex with histone acetyltransferase p300 and NF-κB (nuclear factor κB) subunits. In vitro coculture and in vivo injection of ALI monocyte-derived exosomes increased the production of proinflammatory cytokines. Importantly, the administration of two CtBP2 inhibitors, NSC95397 and MTOB, could significantly reverse CtBP2-mediated transactivation. Collectively, our results support a model in which monocyte-derived exosomal CLMAT3 activates the CtBP2-p300-NF-κB complex to induce proinflammatory cytokines, thus contributing to the pathogenesis of ALI.

Decreased secretion and profibrotic activity of tubular exosomes in diabetic kidney disease

Tubular changes contribute to the development of renal pathologies in diabetic kidney disease (DKD), including interstitial fibrosis. It is unclear how tubular cells relay signals to interstitial fibroblasts. Recently, exosomes have been recognized as crucial mediators of intercellular communication. We hypothesized that exosomes secreted from tubular cells may stimulate fibroblasts for interstitial fibrosis in DKD. In this study, we isolated and purified exosomes from the renal cortex of DKD mice and high glucose-treated mouse proximal tubular cells. Compared with nondiabetic mice, exosome secretion in kidney tissues decreased in DKD mice. Likewise, high glucose incubation reduced exosome secretion in mouse kidney proximal tubular BUMPT cells. To study the effect of tubular cell exosomes on fibroblasts, exosomes from BUMPT cells were added to renal fibroblast NRK-49F cell cultures. Notably, exosomes from high glucose conditioned BUMPT cells induced higher proliferation, significant morphological change, and substantial production of fibronectin, α-smooth muscle actin, and collagen type Ι in NRK-49F fibroblasts. Proteomics analysis was further performed to profile the proteins within tubular cell exosomes. Interestingly, 22 proteins were found to be differentially expressed between tubular exosomes derived from high glucose conditioned cells and those from normal glucose conditioned cells. Cytoscape analysis suggested the existence of two protein-protein interaction networks in these exosomal differentially expressed proteins. While one of the protein-protein interaction networks comprised enolase 1 (Eno1), heat shock protein family A member 8 (Hspa8), thioredoxin 1 (Txn1), peptidylprolyl isomerase A (Ppia), phosphoglycerate kinase 1 (Pgk1), DNA topoisomerase II-β (Top2b), and β-actin (Actb), the other had the family proteins of human leucocyte antigen F (Ywhag), a component of the ND10 nuclear body (Ywhae), interferon regulatory factor-8 (Ywhaq), and human leucocyte antigen A (Ywhaz). Gene expression analysis via Nephroseq showed a correlation of Eno1 expression with DKD clinical manifestation. In conclusion, DKD is associated with a decrease in exosome secretion in renal tubular cells. Exosomes from high glucose conditioned tubular cells may regulate the proliferation and activation of fibroblasts, contributing to the paracrine signaling mechanism responsible for the pathological onset of renal interstitial fibrosis in DKD.

Identification of Key Genes of Human Advanced Diabetic Nephropathy Independent of Proteinuria by Transcriptome Analysis

Background

Diabetic nephropathy (DN) is the leading cause of ESRD. Emerging evidence indicated that proteinuria may not be the determinant of renal survival in DN. The aim of the current study was to provide molecular signatures apart from proteinuria in DN by an integrative bioinformatics approach.

Method

Affymetrix microarray datasets from microdissected glomerular and tubulointerstitial compartments of DN, healthy controls, and proteinuric disease controls including minimal change disease and membranous nephropathy were extracted from open-access database. Differentially expressed genes (DEGs) in DN versus both healthy and proteinuric controls were identified by limma package, and further defined by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Hub genes were checked by protein-protein interaction networks.

Results

A total of 566 glomerular and 581 tubulointerstitial DEGs were identified in DN, which were commonly differentially expressed compared to normal controls and proteinuric disease controls. The upregulated DEGs in both compartments were significantly enriched in GO biological process associated with fibrosis, inflammation, and platelet dysfunction, and largely located in extracellular space, including matrix and extracellular vesicles. Pathway analysis highlighted immune system regulation. Hub genes of the upregulated DEGs negatively correlated with estimated glomerular filtration rate (eGFR). While the downregulated DEGs and their hub genes in tubulointerstitium were enriched in pathways associated with lipid metabolism and oxidation, which positively correlated with eGFR.

Conclusions

Our study identified pathways including fibrosis, inflammation, lipid metabolism, and oxidative stress contributing to the progression of DN independent of proteinuria. These genes may serve as biomarkers and therapeutic targets.

Extracellular vesicle-based Nanotherapeutics: Emerging frontiers in anti-inflammatory therapy

Dysregulated inflammation is a complicated pathological process involved in various diseases, and the treatment of inflammation-linked disorders currently represents an enormous global burden. Extracellular vesicles (EVs) are nanosized, lipid membrane-enclosed vesicles secreted by virtually all types of cells, which act as an important intercellular communicative medium. Considering their capacity to transfer bioactive substances, both unmodified and engineered EVs are increasingly being explored as potential therapeutic agents or therapeutic vehicles. Moreover, as the nature's own delivery tool, EVs possess many desirable advantages, such as stability, biocompatibility, low immunogenicity, low toxicity, and biological barrier permeability. The application of EV-based therapy to combat inflammation, though still in an early stage of development, has profound transformative potential. In this review, we highlight the recent progress in EV engineering for inflammation targeting and modulation, summarize their preclinical applications in the treatment of inflammatory disorders, and present our views on the anti-inflammatory applications of EV-based nanotherapeutics.

miR-196b-5p-enriched extracellular vesicles from tubular epithelial cells mediated aldosterone-induced renal fibrosis in mice with diabetes

INTRODUCTION

Aldosterone is a mediator of progressive renal disease, but the mechanisms for aldosterone-mediated renal impairment in mice with diabetes are not fully defined.

METHODS

Aldosterone and/or mineralocorticoid receptor antagonist eplerenone were used to treat the db/db mice with diabetes. Proximal tubule epithelial cells (PTECs) and fibroblasts were cultured. Blood and kidney samples from patients with diabetes with or without diabetic kidney disease (DKD) were used to verify the findings from animals and cultured cells.

RESULTS

We found that aldosterone promoted proteinuria and tubulointerstitial extracellular matrix (ECM) accumulation in db/db mice with diabetes while eplerenone mitigated the adverse effect of aldosterone. However, coculture of PTECs and fibroblasts found that when PTECs-derived extracellular vesicles (EVs) were taken up by fibroblasts, ECM production increased remarkably. Moreover, C57BL/6 mice injected with EVs from renal cortex of aldosterone-treated db/db mice showed increased ECM accumulation. Function of the ingredients of PTECs-derived EVs were analyzed, and RNAs were identified to be responsible for the EVs-induced fibroblast dysfunction. Furthermore, microRNA (miRNA) array analysis revealed that miR-196b-5p was the most remarkably increased miRNA in PTECs-derived EVs with aldosterone stimulation. Overexpression of miR-196b-5p in fibroblasts increased ECM production, accompanied by inhibition of the SOCS2 expression and enhanced STAT3 phosphorylation. In addition, plasma levels of miR-196b-5p was higher in patients with DKD as compared with patients without DKD and miR-196b-5p levels positively correlated with the albuminuria concentration. In kidney specimens from patients with diabetes, expression of miR-196b-5p, located mainly in PTECs, increased in patients with DKD as compared with the non-DKD.

CONCLUSION

This study demonstrates the involvement of miR-196b-5p-EVs pathway as a novel mechanism in aldosterone-induced renal fibrosis in diabetes. EVs rich in miR-196b-5p mediate the crosstalk between PTECs and fibroblast during the development of renal fibrosis, which might be associated with STAT3/SOCO2 signaling pathway.

Exosomes: Carriers of Pro-Fibrotic Signals and Therapeutic Targets in Fibrosis

Exosomes are nano-sized extracellular vesicles that are released by a variety of cells. Exosomes contain cargo from cells they derived, including lipids, proteins and nucleic acids. The bilayer lipid membrane structure of exosomes protects these contents from degradation, allowing them for intercellular communication. The role of exosomes in fibrotic diseases is increasingly being valued. Exosomes, as carriers of profibrotic signals, are involved in the development of fibrotic diseases, and also regulate fibrosis by transmitting signals that inhibit fibrosis or inflammation. Exosomes mobilize and activate a range of effector cells by targeted delivery of bioactive information. Exosomes can also reflect the condition of cells, tissues and organisms, and thus become potential biomarkers of fibrotic diseases. Exosomes from bone marrow stem cells support biological signaling that regulates and inhibits fibrosis and thus initially used in the treatment of fibrotic diseases. This article briefly summarizes the role of exosomes in the pathogenesis and treatment of fibrotic diseases and raises some issues that remain to be resolved.

Three-dimensional culture of MSCs produces exosomes with improved yield and enhanced therapeutic efficacy for cisplatin-induced acute kidney injury

Background

Exosomes derived from mesenchymal stem cells (MSC-exos) have been demonstrated with great potential in the treatment of multiple human diseases including acute kidney injury (AKI) by virtue of their intrinsic cargoes. However, there are major challenges of low yield and the lack of an established biomanufacturing platform to efficiently produce MSC-exos, thereby limiting their therapeutic application. Here, we aimed to establish a novel strategy to produce MSC-exos with a hollow fiber bioreactor-based three-dimensional (3D) culture system and evaluate the therapeutic efficacy of 3D-exosomes (3D-exos) on AKI.

Methods

Mesenchymal stem cells (MSCs) were isolated from fresh human umbilical cord and cultured in two-dimensional (2D) flasks. 2 × 10⁸ MSCs were inoculated into the hollow fiber bioreactor for 3D culture. The culture supernatants were collected every 1 or 2 days for isolating exosomes. Exosomes from 2D (2D-exos) and 3D cultures were characterized by transmission electron microscopy, nanoparticle tracking analysis, and western blotting analysis of exosome markers. The yield of exosomes from 2 × 10⁸ MSCs seeded in 2D and 3D culture system was compared, based on protein quantification. The therapeutic efficacy of 2D-exos and 3D-exos was investigated in a murine model of cisplatin-induced AKI in vivo and in vitro.

Results

3D culture did not significantly change the surface markers of MSCs, as well as the morphology, size, and exosomal markers of 3D-exos when compared to those of 2D-exos. Compared with conventional 2D culture, the 3D culture system increased total exosome production up to 19.4-fold. 3D-exos were more concentrated in the harvested supernatants (15.5-fold) than 2D-exos, which led to a higher exosome collection efficiency of 3D culture system. In vivo, both 2D-exos and 3D-exos significantly alleviated cisplatin-induced murine AKI evidenced by improved renal function, attenuated pathological changes of renal tubules, reduced inflammatory factors, and repressed T cell and macrophage infiltration. Impressively, 3D-exos were more effective than 2D-exos. Moreover, 3D-exos were taken up by tubular epithelial cells (TECs) with improved efficiency, thereby exhibiting superior anti-inflammatory effect and improved viability of TECs in vitro.

Conclusions

In summary, our findings demonstrate that the hollow fiber 3D culture system provides an efficient strategy for the continuous production of MSC-exos which has enhanced therapeutic potential for cisplatin-induced AKI.

Risk factors of acute kidney injury induced by multiple wasp stings

In Asia, acute kidney injury (AKI) induced by wasp stings is common; however, the pathophysiological mechanisms involved remain unclear. To evaluate the mechanisms associated with AKI induced by wasp stings, we conducted a retrospective cohort study that assessed blood and urinary samples from 112 patients with hospital admissions resulting from wasp stings. These samples were divided into those with AKI and without AKI as described in the Kidney Disease Improving Global Outcomes (KDIGO) database. Of the patients, 48.2% presented with an elevated number of leukocytes (median 19.9 vs. 15.8 × 10⁹/L), serum creatinine (median 122.0 vs. 66.0 μmol/L), alanine aminotransferase (ALT) (median 176 vs. 32 U/L), aspartate aminotransferase (AST) (median 402 vs. 37 U/L), lactate dehydrogenase (LDH) (median 3076.0 vs. 300.0 U/L), creatine kinase (CK) (median 9990.0 vs. 261.0 U/L), creatine kinase myocardial band (CK-mb) (median 200.0 vs. 29.5 U/L), activated partial thromboplastin time (APTT) (median 70.0 vs. 42.5s), prothrombin time (PT) (median 15.0 vs. 12.5s), myoglobin (median 2200.0 vs. 78.0 ng/mL), proteinuria (51.9% vs. 17.2% ≥ 1+), and urinary monocyte chemotactic protein-1 (MCP-1) (median 432.0 vs. 177.0 pg/mL), and subsequently developed AKI. As determined by multivariate logistic regression analysis, elevated leukocytes (>10 × 10⁹/L) [OR 1.12 (95% CI 1.02-1.23)], high myoglobin (>1200 ng/mL) [OR 18.51 (95% CI 1.51-132.27)], and high urinary MCP-1 (>200 pg/mL) [OR 5.42 (95% CI 1.27-30.39)] on admission were independent risk factors for AKI. At admission, baseline values for ALT, aspartate aminotransferase (AST), LDH, CK-mb, APTT, PT, and proteinuria were higher for those who later died as well as for those who developed end-stage renal disease (ESRD). No patients without AKI died or developed ESRD. The present study explored the pathophysiology of AKI induced by wasp stings based on the findings of risk factors as well as factors related to outcomes. An understanding of AKI induced by wasp stings allows better treatment options and clinical management for wasp stings patients.

Novel Aspects of Extracellular Vesicles in the Regulation of Renal Physiological and Pathophysiological Processes

Extracellular vesicles (EV) are nanosized particles released by a large variety of cells. They carry molecules such as proteins, RNA and lipids. While urinary EVs have been longer studied as a source of biomarkers for renal and non-renal disorders, research on EVs as regulatory players of renal physiological and pathological processes has experienced an outbreak recently in the past decade. In general, the microenvironment and (patho)physiological state of the donor cells affect the cargo of the EVs released, which then determines the effect of these EVs once they reach a target cell. For instance, EVs released by renal epithelial cells modulate the expression and function of water and solute transporting proteins in other cells. Also, EVs have been demonstrated to regulate renal organogenesis and blood flow. Furthermore, a dual role of EVs promoting, but also counteracting, disease has also been reported. EVs released by renal tubular cells can reach fibroblasts, monocytes, macrophages, T cells and natural killer cells, thus influencing the pathogenesis and progression of renal disorders like acute kidney injury and fibrosis, nephrolithiasis, renal transplant rejection and renal cancer, among others. On the contrary, EVs may also exert a cytoprotective role upon renal damage and promote recovery of renal function. In the current review, a systematic summary of the key studies from the past 5 years addressing the role of EVs in the modulation of renal physiological and pathophysiological processes is provided, highlighting open questions and discussing the potential of future research.

Extraction and identification of synovial tissue-derived exosomes by different separation techniques

OBJECTIVE

The aim of this study is to compare the efficiency of different separation techniques for extracting synovial tissue-derived exosomes.

METHODS

The synovial tissue discarded during knee arthroscopy or total knee arthroplasty surgery was collected from the Third Affiliated Hospital of Beijing University of Chinese Medicine. Ultracentrifugation (UC), filtration combined with size exclusion chromatography (SECF), and 8% polyethylene glycol (PEG) were used to extract synovial tissue-derived exosomes. Transmission electron microscopy (TEM), nanoparticle tracer analysis (NTA), and Western Blot (WB) were used to detect the morphology, particle size, and biomarker proteins (CD9, CD63, Flotillin-1, and calnexin) of exosomes.

RESULTS

The extracts of enriched round and discoid vesicles were successfully extracted with UC, SECF, and PEG. The results of TEM have shown that all three extraction methods can extract circular or elliptical vesicles with disc- and cup-shaped structures from the synovial tissue, with the diameter is about 30-150 nm. NTA suggested the main peaks of three groups of exosomes are around 100-120 nm, and the concentration of the three groups of exosomes was greater than 1 × 10¹⁰/ml. The results of WB showed that three positive protein markers (CD9, CD63, and Flotillin-1) were highly expressed in the suspension extracted by the three methods and low in the synovial tissue. However, the negative protein (calnexin) was highly expressed in synovial tissues and PEG group, while low in UC and SECF group.

CONCLUSION

Morphology, particle size, and labeled protein marker detection confirmed that UC, SECF, and PEG can extract exosomes derived from synovial tissue; UC and SECF are more recommended for the extraction of synovial tissue-derived exosomes, which provides a methodological basis for studying the function and mechanism of synovial tissue exosomes in the future.

Brain-kidney interaction: Renal dysfunction following ischemic stroke

Stroke is a leading cause of mortality and morbidity, with long-term debilitating effects. Accumulating evidence from experimental studies as well as observational studies in patients suggests a cross talk between the brain and kidney after stroke. Stroke may lead to kidney dysfunction which can adversely impact patient outcome. In this review article, we discuss the epidemiology and mechanisms of brain–kidney interaction following ischemic stroke. Specifically, we discuss the role of the central autonomic network, autoregulation, inflammatory and immune responses, the role of extracellular vesicles and their cargo microRNA, in mediating brain–kidney interaction following stroke. Understanding the bidirectional nature of interaction between the brain and kidney after cerebral injury would have clinical implications for the treatment of stroke and overall patient outcome.

Macrophage-Derived Exosomal Mir-155 Regulating Cardiomyocyte Pyroptosis and Hypertrophy in Uremic Cardiomyopathy

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miR-155 was synthesized and loaded into exosomes in increased infiltration of macrophages in a uremic heart.

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The released exosomal fusion with the plasma membrane leads to the release of miR-155 into the cytosol and translational repression of forkhead transcription factors of the O class in cardiomyocytes.

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Macrophage-derived miR-155–containing exosomes promoted cardiomyocyte pyroptosis and uremic cardiomyopathy changes (cardiac hypertrophy and fibrosis) by directly targeting FoxO3a in uremic mice. Inhibiting secretion from macrophage-derived miR-155–containing exosomes represents a novel therapeutic strategy for the management of uremic cardiomyopathy.

miR-155 was synthesized and loaded into exosomes in increased infiltration of macrophages in a uremic heart. The released exosomal fusion with the plasma membrane leads to the release of miR-155 into the cytosol and translational repression of forkhead transcription factors of the O class (FoxO3a) in cardiomyocytes. Finally, macrophage-derived miR-155–containing exosomes promoted cardiomyocyte pyroptosis and uremic cardiomyopathy changes (cardiac hypertrophy and fibrosis) by directly targeting FoxO3a in uremic mice.

Extracellular Vesicles as Mediators of Cellular Crosstalk Between Immune System and Kidney Graft

Extracellular vesicles (EVs) are known immune-modulators exerting a critical role in kidney transplantation (KT). EV bioactive cargo includes graft antigens, costimulatory/inhibitory molecules, cytokines, growth factors, and functional microRNAs (miRNAs) that may modulate expression of recipient cell genes. As paracrine factors, neutrophil- and macrophage-derived EVs exert immunosuppressive and immune-stimulating effects on dendritic cells, respectively. Dendritic cell-derived EVs mediate alloantigen spreading and modulate antigen presentation to T lymphocytes. At systemic level, EVs exert pleiotropic effects on complement and coagulation. Depending on their biogenesis, they can amplify complement activation or shed complement inhibitors and prevent cell lysis. Likewise, endothelial- and platelet-derived EVs can exert procoagulant/prothrombotic effects and also promote endothelial survival and angiogenesis after ischemic injury. Kidney endothelial- and tubular-derived EVs play a key role in ischemia-reperfusion injury (IRI) and during the healing process; additionally, they can trigger rejection by inducing both alloimmune and autoimmune responses. Endothelial EVs have procoagulant/pro-inflammatory effects and can release sequestered self-antigens, generating a tissue-specific autoimmunity. Renal tubule-derived EVs shuttle pro-fibrotic mediators (TGF-β and miR-21) to interstitial fibroblasts and modulate neutrophil and T-lymphocyte influx. These processes can lead to peritubular capillary rarefaction and interstitial fibrosis-tubular atrophy. Different EVs, including those from mesenchymal stromal cells (MSCs), have been employed as a therapeutic tool in experimental models of rejection and IRI. These particles protect tubular and endothelial cells (by inhibition of apoptosis and inflammation-fibrogenesis or by inducing autophagy) and stimulate tissue regeneration (by triggering angiogenesis, cell proliferation, and migration). Finally, urinary and serum EVs represent potential biomarkers for delayed graft function (DGF) and acute rejection. In conclusion, EVs sustain an intricate crosstalk between graft tissue and innate/adaptive immune systems. EVs play a major role in allorecognition, IRI, autoimmunity, and alloimmunity and are promising as biomarkers and therapeutic tools in KT.

Immunocapture-based ELISA to characterize and quantify exosomes in both cell culture supernatants and body fluids

The immunocapture-based ELISA for extracellular vesicles (EVs)/exosomes, originally described in 2009 by Logozzi and colleagues, allows to capture, detect, characterize and quantify extracellular vesicles in both human body fluids and cell culture supernatants. It is based on the use of two antibodies directed one against a typical exosomal housekeeping protein and the second against either another exosomal housekeeping protein or a potential disease marker: the first antibody is used for the capture of exosomes, the second for the quantification and characterization of the captured vesicles. In fact, with this method it is possible both to characterize and count exosomes and to detect the presence of disease, including tumor, biomarkers. This needs of course to preliminary obtain an EVs purification from the clinical sample; the most agreed method to get to an EVs purification is the repeated rounds of ultracentrifugation, that, while far to be perfect, is the methodological approach allowing to not exclude EVs subpopulation from the separation procedure and to analyze a full range of EVs from both qualitative and quantitative point of view. The immunocapture-based approach has proven to be highly useful in screening, diagnosis and prognosis of tumors, in plasma samples. One amazing information provided by this method is that cancer patients have always significantly higher levels of EVs, in particular of exosomes, independently from the histological nature of the tumor. One microenvironmental factor that is fully involved in the increased exosome release by tumors is the extracellular acidity. However, few pre-clinical data suggest that plasmatic levels of exosomes may correlate with the tumor mass. Some recent clinical reports suggest also that circulating exosomes represent the real delivery system for some known tumor markers that are presently on trial (e.g., PSA). Here we review the pros and cons of the immunocapture-based technique in quantitative and qualitative evaluation of EVs in both health and disease.

Urinary extracellular vesicles: Origin, role as intercellular messengers and biomarkers; efficient sorting and potential treatment options

Urinary extracellular vesicles (uEVs) are a heterogenous group of vesicles consisting mainly of microvesicles and exosomes that originate predominantly (99.96%) from kidney, the urinary tract epithelium and the male reproductive tract. Secreted EVs contain molecular cargo from parental cells and provide an attractive source for biomarkers, a potential readout of physiological and pathophysiological mechanisms, and events associated with the urinary system. uEVs are readily enriched and isolated from urine samples and we review 6 standard methods that allow for downstream analysis of the uEV cargo. Although the use of uEVs as a surrogate readout for physiological changes in tissue protein levels is widespread, the protein abundance in uEVs is affected significantly by mechanisms that regulate protein sorting and secretion in uEVs. Data suggest that baseline kidney tissue and uEV levels of apical membrane-associated electrolyte transport proteins are not directly related in human patients. Recent evidence indicates that EVs may contribute to physiological and pathophysiological intercellular signalling and EVs confer protection against renal ischemia-reperfusion injury. The therapeutic use of EVs as information carriers has mainly been explored in vitro and a major hurdle lies in the translation of the in vitro findings into an in vivo setting. Thus, the EV research field is moving from a technical focus to a more physiological focus, allowing for a deeper understanding of human physiology, development of diagnostic tools and potential treatment strategies for precision medicine.

Tubule-derived exosomes play a central role in fibroblast activation and kidney fibrosis

Extracellular vesicles such as exosomes are involved in mediating cell-cell communication by shuttling an assortment of proteins and genetic information. Here, we tested whether renal tubule-derived exosomes play a central role in mediating kidney fibrosis. The production of exosomes was found to be increased in the early stage of unilateral ureteral obstruction, ischemia reperfusion injury or 5/6 nephrectomy models of kidney disease. Exosome production occurred primarily in renal proximal tubular epithelium and was accompanied by induction of sonic hedgehog (Shh). In vitro, upon stimulation with transforming growth factor-β1, kidney proximal tubular cells (HKC-8) increased exosome production. Purified exosomes from these cells were able to induce renal interstitial fibroblast (NRK-49F) activation. Conversely, pharmacologic inhibition of exosome secretion with dimethyl amiloride, depletion of exosome from the conditioned media or knockdown of Shh expression abolished the ability of transforming growth factor-β1-treated HKC-8 cells to induce NRK-49F activation. In vivo, injections of tubular cell-derived exosomes aggravated kidney injury and fibrosis, which was negated by an Shh signaling inhibitor. Blockade of exosome secretion in vivo ameliorated renal fibrosis after either ischemic or obstructive injury. Furthermore, knockdown of Rab27a, a protein that is essential for exosome formation, also preserved kidney function and attenuated renal fibrotic lesions in mice. Thus, our results suggest that tubule-derived exosomes play an essential role in renal fibrogenesis through shuttling Shh ligand. Hence, strategies targeting exosomes could be a new avenue in developing therapeutics against renal fibrosis.

Human mesenchymal stromal cells broadly modulate high glucose-induced inflammatory responses of renal proximal tubular cell monolayers

BACKGROUND

Renal proximal tubular epithelial cells (RPTEC) are dysfunctional in diabetic kidney disease (DKD). Mesenchymal stromal cells (MSC) may modulate DKD pathogenesis through anti-inflammatory mediators. This study aimed to investigate the pro-inflammatory effect of extended exposure to high glucose (HG) concentration on stable RPTEC monolayers and the influence of MSC on this response.

METHODS

Morphologically stable human RPTEC/TERT1 cell monolayers were exposed to 5 mM and 30 mM (HG) D-glucose or to 5 mM D-glucose + 25 mM D-mannitol (MAN) for 5 days with sequential immunoassays of supernatants and end-point transcriptomic analysis by RNA sequencing. Under the same conditions, MSC-conditioned media (MSC-CM) or MSC-containing transwells were added for days 4-5. Effects of CM from HG- and MAN-exposed RPTEC/MSC co-cultures on cytokine secretion by monocyte-derived macrophages were determined.

RESULTS

After 72-80 h, HG resulted in increased RPTEC/TERT1 release of interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1 and neutrophil gelatinase-associated lipocalin (NGAL). The HG pro-inflammatory effect was attenuated by concentrated (10×) MSC-CM and, to a greater extent, by MSC transwell co-culture. Bioinformatics analysis of RNA sequencing data confirmed a predominant effect of HG on inflammation-related mediators and biological processes/KEGG pathways in RPTEC/TERT1 stable monolayers as well as the non-contact-dependent anti-inflammatory effect of MSC. Finally, CM from HG-exposed RPTEC/MSC transwell co-cultures was associated with attenuated secretion of inflammatory mediators by macrophages compared to CM from HG-stimulated RPTEC alone.

CONCLUSIONS

Stable RPTEC monolayers demonstrate delayed pro-inflammatory response to HG that is attenuated by close proximity to human MSC. In DKD, this MSC effect has potential to modulate hyperglycemia-associated RPTEC/macrophage cross-talk.

Saturated fatty acid stimulates production of extracellular vesicles by renal tubular epithelial cells

Lipotoxicity, an accumulation of intracellular lipid metabolites, has been proposed as an important pathogenic mechanism contributing to kidney dysfunction in the context of metabolic disease. Palmitic acid, a predominant lipid derivative, can cause lipoapoptosis and the release of inflammatory extracellular vesicles (EVs) in hepatocytes, but the effect of lipids on EV production in chronic kidney disease remains vaguely explored. This study was aimed to investigate whether palmitic acid would stimulate EV release from renal proximal tubular epithelial cells. Human and rat proximal tubular epithelial cells, HK-2 and NRK-52E, were incubated with 1% bovine serum albumin (BSA), BSA-conjugated palmitic acid (PA), and BSA-conjugated oleic acid (OA) for 24-48 h. The EVs released into conditioned media were isolated by ultracentrifugation and quantified by nanoparticle-tracking analysis (NTA). According to NTA, the size distribution of EVs was 30-150 nm with similar mode sizes in all experimental groups. Moreover, BSA-induced EV release was significantly enhanced in the presence of PA, whereas EV release was not altered by the addition of OA. In NRK-52E cells, PA-enhanced EV release was associated with an induction of cell apoptosis reflected by an increase in cleaved caspase-3 protein by Western blot and Annexin V positive cells analyzed by flow cytometry. Additionally, confocal microscopy confirmed the uptake of lipid-induced EVs by recipient renal proximal tubular cells. Collectively, our results indicate that PA stimulates EV release from cultured proximal tubular epithelial cells. Thus, extended characterization of lipid-induced EVs may constitute new signaling paradigms contributing to chronic kidney disease pathology.

Employing Macrophage-Derived Microvesicle for Kidney-Targeted Delivery of Dexamethasone: An Efficient Therapeutic Strategy against Renal Inflammation and Fibrosis

Although glucocorticoids are the mainstays in the treatment of renal diseases for decades, the dose dependent side effects have largely restricted their clinical use. Microvesicles (MVs) are small lipid-based membrane-bound particles generated by virtually all cells. Here we show that RAW 264.7 macrophage cell-derived MVs can be used as vectors to deliver dexamethasone (named as MV-DEX) targeting the inflamed kidney efficiently. Methods: RAW macrophages were incubated with dexamethasone and then MV-DEX was isolated from the supernatants by centrifugation method. Nanoparticle tracking analysis, transmission electron microscopy, western blot and high-performance liquid chromatography were used to analyze the properties of MV-DEX. The LC-MS/MS was applied to investigate the protein compositions of MV-DEX. Based on the murine models of LPS- or Adriamycin (ADR)-induced nephropathy or in-vitro culture of glomerular endothelial cells, the inflammation-targeting characteristics and the therapeutic efficacy of MV-DEX was examined. Finally, we assessed the side effects of chronic glucocorticoid therapy in MV-DEX-treated mice. Results: Proteomic analysis revealed distinct integrin expression patterns on the MV-DEX surface, in which the integrin α_Lβ₂ (LFA-1) and α₄β₁ (VAL-4) enabled them to adhere to the inflamed kidney. Compared to free DEX treatment, equimolar doses of MV-DEX significantly attenuated renal injury with an enhanced therapeutic efficacy against renal inflammation and fibrosis in murine models of LPS- or ADR-induced nephropathy. In vitro, MV-DEX with about one-fifth of the doses of free DEX achieved significant anti-inflammatory efficacy by inhibiting NF-κB activity. Mechanistically, MV-DEX could package and deliver glucocorticoid receptors to renal cells, thereby, increasing cellular levels of the receptor and improving cell sensitivity to glucocorticoids. Notably, delivering DEX in MVs significantly reduced the side effects of chronic glucocorticoid therapy (e.g., hyperglycemia, suppression of HPA axis). Conclusion: In summary, macrophage-derived MVs efficiently deliver DEX into the inflamed kidney and exhibit a superior capacity to suppress renal inflammation and fibrosis without apparent glucocorticoid adverse effects. Our findings demonstrate the effectiveness and security of a novel drug delivery strategy with promising clinical applications.

Extracellular Vesicles from Albumin-Induced Tubular Epithelial Cells Promote the M1 Macrophage Phenotype by Targeting Klotho

Albumin absorbed by renal tubular epithelial cells induces inflammation and plays a key role in promoting diabetic kidney disease (DKD) progression. Macrophages are prominent inflammatory cells in the kidney, and their role there is dependent on their phenotypes. However, whether albuminuria influences macrophage phenotypes and underlying mechanisms during the development of DKD is still unclear. We found that M1 macrophage-related markers were increased in diabetes mellitus (DM) mouse renal tissues with the development of DKD, and coculture of extracellular vesicles (EVs) from human serum albumin (HSA)-induced HK-2 cells with macrophages induced macrophage M1 polarization in the presence of lipopolysaccharide (LPS). Through a bioinformatic analysis, miR-199a-5p was selected and found to be increased in EVs from HSA-induced HK-2 cells and in urinary EVs from DM patients with macroalbuminuria. Tail-vein injection of DM mice with EVs from HSA-induced HK-2 cells induced kidney macrophage M1 polarization and accelerated the progression of DKD through miR-199a-5p. miR-199a-5p exerted its effect by targeting Klotho, and Klotho induced macrophage M2 polarization through the Toll-like receptor 4 (TLR4) pathway both in vivo and in vitro. In summary, miR-199a-5p from HSA-stimulated HK-2 cell-derived EVs induces M1 polarization by targeting the Klotho/TLR4 pathway and further accelerates the progression of DKD.

The role of extracellular vesicles in renal fibrosis

As a particularly important mediator of intercellular communication, extracellular vesicles (EVs) have been proved to be extensively involved in various system diseases over the past two decades, including in renal diseases. As is well-known, renal fibrosis is the common pathological process of any ongoing renal disease or adaptive repair of kidney injury based on current knowledge. Although much work has been performed focusing on EVs in various renal diseases, the role of EVs in renal fibrosis has not been described in detail and summarized. In this review, we provide a brief overview of the definition, classification and biological process of EVs. Then, the potential mechanisms of EVs in renal fibrosis are illustrated. Lastly, recent advances in EVs and the implications of EVs for diagnosis and therapy in renal fibrosis disease are introduced. We look forward to a more comprehensive understanding of EVs in renal fibrosis, which could be a boon to patients with renal fibrosis disease.

A bell-shaped pattern of urinary aquaporin-2-bearing extracellular vesicle release in an experimental model of nephronophthisis

The DBA/2-FG pcy (pcy) mouse is a model of human nephronophthisis, a recessive cystic kidney disease. Renal expression of aquaporin-2 (AQP2), a water channel protein, has been shown to be altered in pcy mice. However, the relationship between the renal expression and its release in urinary extracellular vesicles (uEV-AQP2), which account for most urinary AQP2, in pcy mice has remained largely unknown. In this study, we examined age-related alterations of this relationship in pcy mice. In comparison with control mice, pcy mice after the age of 14 weeks showed defective urinary concentration ability with an increase in urinary volume. Interestingly, the release of uEV-AQP2 increased progressively up to the age of 16 weeks, but at 21 weeks the release did not significantly differ from that in control mice (i.e., a bell-shaped pattern was evident). Similar results were obtained for uEV marker proteins, including tumor susceptibility gene 101 (TSG101) protein and apoptosis-linked gene 2-interacting protein X (Alix). Immunoblot analysis revealed that renal AQP2 expression increased progressively from 11 weeks, and immunohistochemistry showed that this increase was possibly due to an increase in the number of AQP2-positive cells. Analysis of mRNAs for seven types of AQP expressed in the kidney supported this notion. These data suggest that the level of uEV-AQP2 does not simply mirror the renal expression of AQP2 and that the altered release of uEV-AQP2 in pcy mice depends on the numbers of both renal AQP2-positive cells and EVs released into the urine.

Review of the Isolation, Characterization, Biological Function, and Multifarious Therapeutic Approaches of Exosomes

Exosomes are extracellular vesicles that contain a specific composition of proteins, lipids, RNA, and DNA. They are derived from endocytic membranes and can transfer signals to recipient cells, thus mediating a novel mechanism of cell-to-cell communication. They are also thought to be involved in cellular waste disposal. Exosomes play significant roles in various biological functions, including the transfer of biomolecules such as RNA, proteins, enzymes, and lipids and the regulation of numerous physiological and pathological processes in various diseases. Because of these properties, they are considered to be promising biomarkers for the diagnosis and prognosis of various diseases and may contribute to the development of minimally invasive diagnostics and next generation therapies. The biocompatible nature of exosomes could enhance the stability and efficacy of imaging probes and therapeutics. Due to their potential use in clinical applications, exosomes have attracted much research attention on their roles in health and disease. To explore the use of exosomes in the biomedical arena, it is essential that the basic molecular mechanisms behind the transport and function of these vesicles are well-understood. Herein, we discuss the history, biogenesis, release, isolation, characterization, and biological functions of exosomes, as well as the factors influencing their biogenesis and their technical and biological challenges. We conclude this review with a discussion on the future perspectives of exosomes.

Extracellular Vesicles: Opportunities and Challenges for the Treatment of Renal Diseases

Extracellular vesicles (EVs) are lipid-based membrane-bound particles secreted by virtually all types of cells under both physiological and pathological conditions. Given their unique biological and pharmacological properties, EVs have spurred a renewed interest in their utility for therapeutics. Herein, efforts are made to give a comprehensive overview on the recent advances of EV-based therapy in renal diseases. The fact that EVs are implicated in various renal diseases provides us with new therapeutic modalities by eliminating these pathogenic entities. Strategies that target EVs to inhibit their production, release, and uptake will be discussed. Further, EVs-derived predominantly from stem cells can stimulate tissue repair and ameliorate renal injury via transferring proteins and nucleic acids to injured cells. Such EVs can be exploited as agents in renal regenerative medicine. Finally, we will focus on the specific application of EVs as a novel drug delivery system and highlight the challenges of EVs-based therapies for renal diseases.

Hypoxia and Renal Tubulointerstitial Fibrosis

Hypoxia, one of the most common causes of kidney injury, is a key pathological condition in various kidney diseases. Renal fibrosis is the terminal pathway involved in the continuous progression of chronic kidney disease (CKD), characterized by glomerulosclerosis and tubulointerstitial fibrosis (TIF). Recent studies have shown that hypoxia is a key factor promoting the progression of TIF. Loss of microvasculature, reduced oxygen dispersion, and metabolic abnormality of cells in the kidney are the main causes of the hypoxic state. Hypoxia can, in turn, profoundly affect the tubular epithelial cells, endothelial cells, pericytes, fibroblasts, inflammatory cells, and progenitor cells. In this chapter, we reviewed the critical roles of hypoxia in the pathophysiology of TIF and discussed the potential of anti-hypoxia as its promising therapeutic target.

New insight into the role of extracellular vesicles in kidney disease

Extracellular vesicles (EVs) are released to maintain cellular homeostasis as well as to mediate cell communication by spreading protective or injury signals to neighbour or remote cells. In kidney, increasing evidence support that EVs are signalling vesicles for different segments of tubules, intra‐glomerular, glomerular‐tubule and tubule‐interstitial communication. EVs released by kidney resident and infiltrating cells can be isolated from urine and were found to be promising biomarkers for kidney disease, reflecting deterioration of renal function and histological change. We have here summarized the recent progress about the functional role of EVs in kidney disease as well as challenges and future directions involved.