Transfer of microRNA-486-5p from human endothelial colony forming cell–derived exosomes reduces ischemic kidney injury

Immunomodulatory and Regenerative Effects of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Renal Diseases

Mesenchymal stem cells (MSCs) have immunomodulatory and regenerative effects in many organs, including the kidney. Emerging evidence has shown that the trophic effects from MSCs are mainly mediated by the paracrine mechanism rather than the direct differentiation of MSCs into injured tissues. These secretomes from MSCs include cytokines, growth factors, chemokines and extracellular vesicles (EVs) containing microRNAs, mRNAs, and proteins. Many research studies have revealed that secretomes from MSCs have potential to ameliorate renal injury in renal disease models, including acute kidney injury and chronic kidney disease through a variety of mechanisms. These trophic mechanisms include immunomodulatory and regenerative effects. In addition, accumulating evidence has uncovered the specific factors and therapeutic mechanisms in MSC-derived EVs. In this article, we summarize the recent advances of immunomodulatory and regenerative effects of EVs from MSCs, especially focusing on the microRNAs.

Extracellular vesicles for acute kidney injury in preclinical rodent models: a meta-analysis

Introduction

Extracellular vesicles (EVs), especially stem cell-derived EVs, have emerged as a potential novel therapy for acute kidney injury (AKI). However, their effects remain incompletely understood. Therefore, we performed this meta-analysis to systematically review the efficacy of EVs on AKI in preclinical rodent models.

Methods

We searched PubMed, EMBASE, and the Web of Science up to March 2019 to identify studies that reported the treatment effects of EVs in a rodent AKI model. The primary outcome was serum creatinine (Scr) levels. The secondary outcomes were the blood urea nitrogen (BUN) levels, renal injury score, percentage of apoptotic cells, and interleukin (IL)-10 and tumour necrosis factor (TNF)-α levels. Two authors independently screened articles based on the inclusion and exclusion criteria. The meta-analysis was conducted using RevMan 5.3 and R software.

Results

Thirty-one studies (n = 552) satisfied the inclusion criteria. Pooled analyses demonstrated that the levels of Scr (SMD = − 3.71; 95% CI = − 4.32, − 3.10; P < 0.01), BUN (SMD = − 3.68; 95% CI = − 4.42, − 2.94; P < 0.01), and TNF-α (SMD = − 2.65; 95% CI = − 4.98, − 0.32; P < 0.01); the percentage of apoptotic cells (SMD = − 6.25; 95% CI = − 8.10, − 4.39; P < 0.01); and the injury score (SMD = − 3.90; 95% CI = − 5.26, − 2.53; P < 0.01) were significantly decreased in the EV group, and the level of IL-10 (SMD = 2.10; 95% CI = 1.18, 3.02; P < 0.01) was significantly increased. Meanwhile, no significant difference was found between stem cell-derived EVs and stem cells.

Conclusion

The present meta-analysis confirmed that EV therapy could improve renal function and the inflammatory response status and reduce cell apoptosis in a preclinical rodent AKI model. This provides important clues for human clinical trials on EVs.

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.

Exogenous miR-26a suppresses muscle wasting and renal fibrosis in obstructive kidney disease

Kidney fibrosis occurs in almost every type of chronic kidney disease. We found that microRNA (miR)-26a was decreased in the kidney, muscle, and exosomes of unilateral ureteral obstruction (UUO) mice. We hypothesized that exogenous miR-26 could suppresses renal fibrosis and muscle wasting in obstructive kidney disease. For this purpose, we generated exosomes that encapsulated miR-26, then injected these into skeletal muscle of UUO mice. The expression of miR-26a was elevated in serum exosomes from UUO mice following exosome-miR-26a injection. In these mice, muscle wasting has been ameliorated as evidenced by increased muscle weights. In addition, a muscle atrophy marker, myostatin, is increased in UUO muscle; provision of miR-26a abolished this increase. We detected a remote effect of exosomes containing miR-26a in UUO-induced renal fibrosis. The intervention of miR-26a attenuated UUO-induced renal fibrosis as determined by immunohistological assessment of α-smooth muscle actin and Masson's trichrome staining. Furthermore, exogenous miR-26a decreased the protein levels of 2 profibrosis proteins, connective tissue growth factor (CTGF) and TGF-β1, in UUO kidney. Our data showed that exosomes containing miR-26a prevented muscle atrophy by inhibiting the transcription factor forkhead box O1. Likewise, the exosome-carried miR-26a limited renal fibrosis by directly suppressing CTGF. Our findings provide an experimental basis for exosome-mediated therapy of muscle atrophy and renal fibrosis.-Zhang, A., Wang, H., Wang, B., Yuan, Y., Klein, J. D., Wang, X. H. Exogenous miR-26a suppresses muscle wasting and renal fibrosis in obstructive kidney disease.

Several critical genes and microRNAs associated with the development of polycystic ovary syndrome

BACKGROUND

We aimed to identify key genes and microRNAs (miRNAs) associated with the development of polycystic ovary syndrome (PCOS).

METHODS

GSE84376 mRNA microarray data (15 PCOS granulosa cells and 13 control granulosa cells) and GSE34526 mRNA microarray data (7 PCOS granulosa cells and 3 control granulosa cells) were downloaded from the Gene Expression Omnibus (GEO) database. First, differentially expressed gene (DEG) analysis, gene set enrichment analysis (GSEA) for differentially expressed mRNAs, and protein-protein interaction (PPI) network analysis were conducted. Next, miRNA-target genes were analyzed and functions predicted, and a competing endogenous RNA (ceRNA) network was constructed. Finally, the relationship between miR-486-5p and PRELID2 was experimentally validated.

RESULTS

Spleen tyrosine kinase (SYK), major histocompatibility complex, class II, DR alpha (HLA-DRA), and interleukin 10 (IL-10) were important nodes in the PPI network. Interestingly, HLA-DRA was significantly enriched in phagosomes mediated by Staphylococcus aureus infection, and in IL-10 enriched during S. aureus infection. One miRNA (miR-486-5p) and a single target gene (PRELID2) were obtained from the ceRNA network. Further experiments showed that miR-486-5p is upregulated and PRELID2 is downregulated in PCOS patient granulosa cells, and that miR-486-5p targets the PRELID2 3'UTR. Topological property analysis showed that hsa-miR-4687-5p downregulation and hsa-miR-4651 upregulation determined the levels of most mRNAs. Levels of the hsa-miR-4651 target gene were significantly enriched in the leukocyte transendothelial migration pathway.

CONCLUSIONS

Our results suggest that HLA-DRA and IL-10 may contribute to PCOS progression via phagosome enriched by S. aureus infection, while miR-486-5p may be implicated in follicular development in PCOS by targeting PRELID2. Besides, miR-4651 may be involved in inflammation via leukocyte transendothelial migration, by regulating its target gene. These findings may indicate new directions and constitute a breakthrough in studying the pathophysiology of PCOS.

The exosome-mediated autocrine and paracrine actions of plasma gelsolin in ovarian cancer chemoresistance

Ovarian cancer (OVCA) is the most lethal gynecological cancer, due predominantly to late presentation, high recurrence rate and common chemoresistance development. The expression of the actin-associated protein cytosolic gelsolin (GSN) regulates the gynecological cancer cell fate resulting in dysregulation in chemosensitivity. In this study, we report that elevated expression of plasma gelsolin (pGSN), a secreted isoform of GSN and expressed from the same GSN gene, correlates with poorer overall survival and relapse-free survival in patients with OVCA. In addition, it is highly expressed and secreted in chemoresistant OVCA cells than its chemosensitive counterparts. pGSN, secreted and transported via exosomes (Ex-pGSN), upregulates HIF1α–mediated pGSN expression in chemoresistant OVCA cells in an autocrine manner as well as confers cisplatin resistance in otherwise chemosensitive OVCA cells. These findings support our hypothesis that exosomal pGSN promotes OVCA cell survival through both autocrine and paracrine mechanisms that transform chemosensitive cells to resistant counterparts. Specifically, pGSN transported via exosomes is a determinant of chemoresistance in OVCA.

Biomechanical Forces and Oxidative Stress: Implications for Pulmonary Vascular Disease

Significance: Oxidative stress in the cell is characterized by excessive generation of reactive oxygen species (ROS). Superoxide (O₂^-) and hydrogen peroxide (H₂O₂) are the main ROS involved in the regulation of cellular metabolism. As our fundamental understanding of the underlying causes of lung disease has increased it has become evident that oxidative stress plays a critical role. Recent Advances: A number of cells in the lung both produce, and respond to, ROS. These include vascular endothelial and smooth muscle cells, fibroblasts, and epithelial cells as well as the cells involved in the inflammatory response, including macrophages, neutrophils, eosinophils. The redox system is involved in multiple aspects of cell metabolism and cell homeostasis. Critical Issues: Dysregulation of the cellular redox system has consequential effects on cell signaling pathways that are intimately involved in disease progression. The lung is exposed to biomechanical forces (fluid shear stress, cyclic stretch, and pressure) due to the passage of blood through the pulmonary vessels and the distension of the lungs during the breathing cycle. Cells within the lung respond to these forces by activating signal transduction pathways that alter their redox state with both physiologic and pathologic consequences. Future Directions: Here, we will discuss the intimate relationship between biomechanical forces and redox signaling and its role in the development of pulmonary disease. An understanding of the molecular mechanisms induced by biomechanical forces in the pulmonary vasculature is necessary for the development of new therapeutic strategies.

The therapeutic effects of microRNAs in preclinical studies of acute kidney injury: a systematic review protocol

BACKGROUND

Acute kidney injury (AKI) causes significant morbidity and mortality in humans, and there are currently no effective treatments to enhance renal recovery. MicroRNAs (miRNAs) are short chain nucleotides that regulate protein expression and have been implicated in the pathogenesis of AKI. Recently, preclinical studies in vivo have uncovered a therapeutic role for administration of specific miRNAs in AKI. However, the overall benefits of this strategy in preclinical studies have not been systematically reviewed, and the potential for translation to human studies is unclear.

AIM

The primary aim is to conduct a systematic review of the therapeutic properties of miRNAs in preclinical studies of AKI. The secondary aim is to determine potential adverse effects of miRNA administration in these studies.

METHODS

A comprehensive search strategy will identify relevant studies in AKI in vivo models, using the MEDLINE, EMBASE, OVID, PUBMED, and Web of Science databases. The search strategy will include terms for mammalian (non-human) AKI models, including injury related to ischemia/reperfusion, nephrotoxicity, sepsis, contrast agents, cardio-pulmonary bypass, and hemorrhagic shock. Interventions will be defined as direct administration of exogenous miRNAs or antagonists of miRNAs, as well as maneuvers that alter expression of miRNAs that are mechanistically linked to AKI outcomes. The primary outcomes will be indices of kidney function and structure, and there will be no restriction on comparator interventions. Two independent investigators will initially screen abstracts, and selected articles that meet eligibility criteria will be reviewed for data abstraction and analysis. The SYRCLE RoB tool for animal studies will determine risk of bias, and meta-analysis will be performed as appropriate. The GRADE methodology will assess the quality of evidence.

DISCUSSION

The administration of selective miRNA mimics or antagonists exerts beneficial effects in mammalian models of AKI, although multiple obstacles must be addressed prior to translation to human clinical trials. The proposed systematic review will document key miRNA candidates, and determine effect size estimates and sources of outcome bias. The review will also identify gaps in knowledge and guide future directions in AKI research.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019128854.

Injectable Supramolecular Ureidopyrimidinone Hydrogels Provide Sustained Release of Extracellular Vesicle Therapeutics

Extracellular vesicles (EVs) are small vesicles secreted by cells and have gained increasing interest as both drug delivery vehicles or as cell-free therapeutics for regenerative medicine. To achieve optimal therapeutic effects, strategies are being developed to prolong EV exposure to target organs. One promising approach to achieve this is through EV-loaded injectable hydrogels. In this study, the use of a hydrogel based on ureido-pyrimidinone (UPy) units coupled to poly(ethylene glycol) chains (UPy-hydrogel) is examined as potential delivery platform for EVs. The UPy-hydrogel undergoes a solution-to-gel transition upon switching from a high to neutral pH, allowing immediate gelation upon administration into physiological systems. Here, sustained EV release from the UPy-hydrogel measured over a period of 4 d is shown. Importantly, EVs retain their functional capacity after release. Upon local administration of fluorescently labeled EVs incorporated in a UPy-hydrogel in vivo, EVs are still detected in the UPy-hydrogel after 3 d, whereas in the absence of a hydrogel, EVs are internalized by fat and skin tissue near the injection site. Together, these data demonstrate that UPy-hydrogels provide sustained EV release over time and enhance local EV retention in vivo, which could contribute to improved therapeutic efficacy upon local delivery and translation toward new applications.

miRNAs in stem cell-derived extracellular vesicles for acute kidney injury treatment: comprehensive review of preclinical studies

Stem cell therapy has been applied in many fields. Basic and clinical studies on stem cell therapy for acute kidney injury (AKI) have been conducted. Stem cells have been found to exert renal protection through a variety of mechanisms, such as regulating the immune system and secreting growth factors, cytokines, and extracellular vesicles (EVs). Among them, EVs are considered to be important mediators for stem cell protection because they contain various biological components, including microRNAs (miRNAs). miRNAs are a class of small RNAs that function in posttranscriptional gene regulation. A number of studies have confirmed that miRNAs in stem cell-derived EVs can protect from AKI. miRNAs can enter the injured renal tissue through EVs released from stem cells, thereby exerting anti-inflammatory, anti-apoptotic, anti-fibrotic, and pro-angiogenesis effects on AKI. However, the stem cell sources and AKI models used in these studies have differed. This article will summarize the miRNAs that play a role in kidney protection in stem cell EVs and clarifies the treatment characteristics and mechanisms of different miRNAs. This may provide a reference for clinical practice for acute and chronic kidney diseases.

Noncoding RNAs in acute kidney injury

Acute kidney injury (AKI) is an important health issue concerning ∼50% of patients treated in intensive care units. AKI mainly occurs after sepsis, acute ischemia, nephrotoxicity, or hypoxia and leads to severe damage of the kidney and to an increased risk of mortality. The diagnosis of AKI is currently based on creatinine urea levels and diuresis. Yet, novel markers may improve the accuracy of this diagnosis at an early stage of the disease, thereby allowing early prevention and therapy, ultimately leading to a reduction in the need for renal replacement therapy and decreased mortality. Non-protein-coding RNAs or noncoding RNAs are central players in development and disease. They are important regulatory molecules that allow a fine-tuning of gene expression and protein synthesis. This regulation is necessary to maintain homeostasis, and its dysregulation is often associated with disease development. Noncoding RNAs are present in the kidney and in body fluids and their expression is modulated during AKI. This review article assembles the current knowledge of the role of noncoding RNAs, including microRNAs, long noncoding RNAs and circular RNAs, in the pathogenesis of AKI. Their potential as biomarkers and therapeutic targets as well as the challenges to translate research findings to clinical application are discussed. Although microRNAs have entered clinical testing, preclinical and clinical trials are needed before long noncoding RNAs and circular RNAs may be considered as useful biomarkers or therapeutic targets of AKI.

Three new circulating microRNAs may be associated with wet age-related macular degeneration

This study investigates the circulating microRNA (miRNA) expression profiles in patients with age-related macular degeneration (AMD) and the role of miRNA in wet AMD and its pathways. Exosomes were extracted from serum samples of AMD patients (n = 70) and a control group (n = 50). After isolating miRNA from the exosomes, miRNAs were transformed into cDNA. In the control and AMD samples, the expression was compared with a panel including 175 genes using the PCR array method. Target genes and pathways of miRNAs were detected by KEGG and Biocarta signaling pathway enrichments. Comparing the serum samples between groups revealed that the expression levels of 15 microRNAs within 175 genes had significantly changed. In the validation studies, miR-129-3p and miR-132-3p had no significant expression in AMD group compared to the controls. miR-486-5p and miR-626 had higher expression in AMD patients compared to the control group, while miR-885-5p showed significantly lower expression. Pathway analysis revealed that these miRNAs may have critical roles in the apoptosis and neovascularization pathways. The data suggest that some miRNAs within the serum may have a role in the pathogenesis of wet AMD. Further studies are needed to examine the use of these miRNAs as biomarkers.

Exosomes from human-bone-marrow-derived mesenchymal stem cells protect against renal ischemia/reperfusion injury via transferring miR-199a-3p

Renal ischemia/reperfusion (I/R) injury is the main reason for acute kidney injury (AKI) and is closely related to high morbidity and mortality. In this study, we found that exosomes from human-bone-marrow-derived mesenchymal stem cells (hBMSC-Exos) play a protective role in hypoxia/reoxygenation (H/R) injury. hBMSC-Exos were enriched in miR-199a-3p, and hBMSC-Exo treatment increased the expression level of miR-199a-3p in renal cells. We further explored the function of miR-199a-3p on H/R injury. miR-199a-3p was knocked down in hBMSCs with a miR-199a-3p inhibitor. HK-2 cells cocultured with miR-199a-3p-knockdown hBMSCs were more susceptible to H/R injury and showed more apoptosis than those cocultured with hBMSCs or miR-199a-3p-overexpressing hBMSCs. Meanwhile, we found that HK-2 cells exposed to H/R treatment incubated with hBMSC-Exos decreased semaphorin 3A (Sema3A) and activated the protein kinase B (AKT) and extracellular-signal-regulated kinase (ERK) pathways. However, HK-2 cells cocultured with miR-199a-3p-knockdown hBMSCs restored Sema3A expression and blocked the activation of the AKT and ERK pathways. Moreover, knocking down Sema3A could reactivate the AKT and ERK pathways suppressed by a miR-199a-3p inhibitor. In vivo, we injected hBMSC-Exos into mice suffering from I/R injury; this treatment induced functional recovery and histologic protection and reduced cleaved caspase-3 and Sema3A expression levels, as shown by immunohistochemistry. On the whole, this study demonstrated an antiapoptotic effect of hBMSC-Exos, which protected against I/R injury, via delivering miR-199a-3p to renal cells, downregulating Sema3A expression and thereby activating the AKT and ERK pathways. These findings reveal a novel mechanism of AKI treated with hBMSC-Exos and provide a therapeutic method for kidney diseases.

Exosomal miRNA-19b-3p of tubular epithelial cells promotes M1 macrophage activation in kidney injury

Tubulointerstitial inflammation is a common characteristic of acute and chronic kidney injury. However, the mechanism by which the initial injury of tubular epithelial cells (TECs) drives interstitial inflammation remains unclear. This paper aims to explore the role of exosomal miRNAs derived from TECs in the development of tubulointerstitial inflammation. Global microRNA(miRNA) expression profiling of renal exosomes was examined in a LPS induced acute kidney injury (AKI) mouse model and miR-19b-3p was identified as the miRNA that was most notably increased in TEC-derived exosomes compared to controls. Similar results were also found in an adriamycin (ADR) induced chronic proteinuric kidney disease model in which exosomal miR-19b-3p was markedly released. Interestingly, once released, TEC-derived exosomal miR-19b-3p was internalized by macrophages, leading to M1 phenotype polarization through targeting NF-κB/SOCS-1. A dual-luciferase reporter assay confirmed that SOCS-1 was the direct target of miR-19b-3p. Importantly, the pathogenic role of exosomal miR-19b-3p in initiating renal inflammation was revealed by the ability of adoptively transferred of purified TEC-derived exosomes to cause tubulointerstitial inflammation in mice, which was reversed by inhibition of miR-19b-3p. Clinically, high levels of miR-19b-3p were found in urinary exosomes and were correlated with the severity of tubulointerstitial inflammation in patients with diabetic nephropathy. Thus, our studies demonstrated that exosomal miR-19b-3p mediated the communication between injured TECs and macrophages, leading to M1 macrophage activation. The exosome/miR-19b-3p/SOCS1 axis played a critical pathologic role in tubulointerstitial inflammation, representing a new therapeutic target for kidney disease.

Renal Regenerative Potential of Extracellular Vesicles Derived from miRNA-Engineered Mesenchymal Stromal Cells

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) possess pro-regenerative potential in different animal models with renal injury. EVs contain different molecules, including proteins, lipids and nucleic acids. Among the shuttled molecules, miRNAs have a relevant role in the pro-regenerative effects of EVs and are a promising target for therapeutic interventions. The aim of this study was to increase the content of specific miRNAs in EVs that are known to be involved in the pro-regenerative effect of EVs, and to assess the capacity of modified EVs to contribute to renal regeneration in in vivo models with acute kidney injuries. To this purpose, MSCs were transiently transfected with specific miRNA mimics by electroporation. Molecular analyses showed that, after transfection, MSCs and derived EVs were efficiently enriched in the selected miRNAs. In vitro and in vivo experiments indicated that EVs engineered with miRNAs maintained their pro-regenerative effects. Of relevance, engineered EVs were more effective than EVs derived from naïve MSCs when used at suboptimal doses. This suggests the potential use of a low amount of EVs (82.5 × 10⁶) to obtain the renal regenerative effect.

MicroRNA‑486‑5p inhibits the growth of human hypertrophic scar fibroblasts by regulating Smad2 expression

The aim of the current study was to investigate the expression and role of microRNA-486-5p (miR-486-5p) in hypertrophic scar (HS) formation, and to examine the associated mechanisms. First, miR-486-5p expression was detected in HS tissues and human hypertrophic scar fibroblasts (hHSFs) by reverse transcription-quantitative polymerase chain reaction. Target genes of miR-486-5p were predicted using TargetScan and verified by dual-luciferase reporter assays. To investigate the role of miR-486-5p in HS formation, miR-486-5p was overexpressed in hHSFs through transfection with miR-486-5p mimics. MTT, cell apoptosis and cell cycle assays were preformed to investigate the proliferation, cell apoptosis and cell cycle distribution of hHSFs, respectively. Additionally, protein expression was measured by western blot analysis. The results demonstrated that miR-486-5p expression was significantly decreased in HS tissues and cells. Mothers against decapentaplegic homolog (Smad)2 was a target gene of miR-486-5p, and it was negatively regulated by miR-486-5p. It was also found that Smad2 expression was significantly increased in HS tissues and cells. Further analysis indicated that miR-486-5p mimic transfection inhibited the proliferation, induced cell apoptosis and increased G1/S phase arrest in hHSFs. Furthermore, the expression of cyclin-dependent kinase (CDK)2, CDK4 and apoptosis regulator Bcl-2 was repressed, while apoptosis regulator BAX expression was enhanced by miR-486-5p mimic transfection. Notably, the effects of miR-486-5p mimic on hHSFs were significantly eliminated by Smad2 plasmid transfection. Taken together, these results demonstrated that miR-486-5p inhibited the proliferation, induced apoptosis and increased G1/S phase arrest of hHSFs by targeting Smad2. miR-486-5p may be a promising therapeutic target for HS management.

Genetic communication by extracellular vesicles is an important mechanism underlying stem cell-based therapy-mediated protection against acute kidney injury

Stem cell-based therapy appears to be a promising new candidate for acute kidney injury (AKI) management. Traditionally, it has been accepted that the mechanism underlying the regenerative effect of stem cells is based on their paracrine/endocrine activity, including release of bioactive factors that act on injured renal cells and presentation of proangiogenic, antiapoptotic, antioxidative, and immunomodulatory effects. Recently, multiple studies have confirmed that extracellular vesicles (EVs) are a kind of vesicle rich in a broad variety of biologically active molecules, including lipids, proteins, and, in particular, nucleic acids. EVs are able to transfer genetic information to target cells, alter target gene regulatory networks, and exert biological effects. Stem cell-derived EVs (SC-EVs) are emerging as potent genetic information sources that deliver mRNAs and miRNAs to injured renal cells and exert renoprotective effects during AKI. On the other hand, EVs originating from injured renal cells also contain genetic information that is believed to be able to influence phenotypic and functional changes in stem cells, favoring renal recovery. In this review, we summarize studies providing evidence of genetic communication during the application of stem cells in preclinical AKI models, aiming to clarify the mechanism and describe the therapeutic effects of stem cell-based therapy in AKI patients.

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.

MicroRNAs in extracellular vesicles protect kidney from ischemic injury: from endothelial to tubular epithelial

Extracellular vesicles from stem cells or progenitor cells are novel therapeutic systems for acute kidney injury. With exosomes (the smallest class of extracellular vesicles), Viñas et al. successfully rescued ischemic injured kidney. MicroRNA-486-5p, the crucial factor specifically delivered by exosomes to kidney, ameliorates the injury by targeting phosphatase and tensin homolog and inhibiting endothelial cell apoptosis. In this commentary, we discuss the potential underlying mechanism and the pivotal impact of their study on extracellular vesicle therapy.

Exosomes: The next generation of endogenous nanomaterials for advanced drug delivery and therapy

Development of functional nanomaterials is of great importance and significance for advanced drug delivery and therapy. Nevertheless, exogenous nanomaterials have a great ability to induce undesired immune responses and nano-protein interactions, which may result in toxicity and failure of therapy. Exosomes, a kind of endogenous extracellular vesicle (40-100 nm in diameter), are considered as a new generation of a natural nanoscale delivery system. Exosomes secreted by different types of cells carry different signal molecules (such as RNAs and proteins) and thus have a great potential for targeted drug delivery and therapy. Herein, we provide comprehensive understanding of the properties and applications of exosomes, including their biogenesis, biofunctions, isolation, purification, and drug loading, and typical examples in drug delivery and therapy. Furthermore, their advantages compared to other nanoparticles and potential in tumor immunotherapy are also discussed. STATEMENT OF SIGNIFICANCE: Exosomes, a kind of endogenous extracellular vesicle, have emerged as a novel and attractive endogenous nanomaterial for advanced drug delivery and targeted therapy. Exosomes are secreted by many types of cells and carry some unique signals obtained from their parental cells. Furthermore, the liposome-like structure allows exosomes to load various drugs. Hence, the potential of exosomes in drug delivery, tumor targeted therapy, and immunotherapy has been investigated in recent years. On the basis of their endogenous features and multifunctional properties, exosomes are of great significance and interest for the development of future medicine and pharmaceuticals.

Exosomes of bone-marrow stromal cells inhibit cardiomyocyte apoptosis under ischemic and hypoxic conditions via miR-486-5p targeting the PTEN/PI3K/AKT signaling pathway

BACKGROUND

Myocardial ischemia-reperfusion injury (MIRI) is a major obstacle in the treatment of ischemic heart disease. Recent studies have shown that exosomes-small membrane vesicles secreted by most cell types-could have a protective effect on the ischemic myocardium. In this study we explored the effect of exosomes derived from bone-marrow stromal cells (BMSC-exo) on cardiomyocyte apoptosis and MIRI.

METHODS

Exosomes were purified from culture media using the ExoQuick kit and observed using transmission electron microscopy. Cell viability was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Cell apoptosis was analyzed by flow cytometry using the Annexin-V/PI stain. The expression levels of microRNA (miRNA), messenger RNA (mRNA) and PTEN/PI3K/AKT-pathway-related proteins were detected by qRT-PCR and western blot, respectively. Myocardial ischemia was simulated by incubating H9C2 cells in a hypoxia/reoxygenation (H/R) conditioned rat MIRI model.

RESULTS

BMSC-exo induced the proliferation of H9C2 cells and rescued H9C2 cells from apoptosis in the H/R model, indicating that BMSC-exo has a protective effect on cardiomyocyte injury caused by H/R. Using transgenic H9C2 cells, we found that miR-486-5p in BMSC-exo suppressed the H/R-triggered apoptosis of H9C2 cells. In addition, BMSC-exo repressed the expression of PTEN in H9C2 cells via miR-486-5p, and subsequently activated the PI3K/AKT pathway in vitro. Moreover, the myocardial injury caused by ischemia/reperfusion was repaired by BMSC-exo which activates the PI3K/AKT pathway via miR-486-5p in vivo.

CONCLUSION

Our results suggested that exosomes from BMSCs have a protective effect on myocardium ischemic injury. MiR-486-5p carried by BMSC-exo plays a pivotal role in the regulatory process by suppressing PTEN expression, activating the PI3K/AKT signaling pathway, and subsequently inhibiting the apoptosis of injured cardiomyocytes.

Endothelial progenitor cells attenuate the lung ischemia/reperfusion injury following lung transplantation via the endothelial nitric oxide synthase pathway

OBJECTIVE

Endothelial progenitor cells (EPCs) can improve endothelial integrity. This study aimed to examine the effects and the mechanism of EPCs on lung ischemia-reperfusion injury (LIRI).

METHODS

Wistar rats were randomized into the sham or the left lung transplantation group. The recipients were randomized and treated with vehicle as the LIRI group, with EPC as the EPC group, or with N5-(1-iminoethyl)-l-ornithine-pretreated EPC as the EPC/L group (n = 8 per group). The ratios of arterial oxygen partial pressure to fractional inspiratory oxygen were measured. The lung wet-to-dry weight ratios, protein levels, and injury, as well as the levels of plasma cytokines, were examined. The levels of endothelin (ET)-1, endothelial nitric oxide synthase (eNOS), phosphorylated eNOS, inducible NOS, phosphorylated myosin light chain, nuclear factor-κBp65, Bax, Bcl-2, cleaved caspase-3, and myeloperoxidase in the graft lungs were detected.

RESULTS

Compared with the LIRI group, EPC treatment significantly increased the ratios of arterial oxygen partial pressure to fractional inspiratory oxygen and decreased the lung wet-to-dry weight ratios and protein levels in the grafts, accompanied by increasing eNOS expression and phosphorylation, but decreasing endothelin-1, inducible NOS, phosphorylated nuclear factor-kBp65, phosphorylated myosin light chain expression, and myeloperoxidase activity. EPCs reduced lung tissue damage and apoptosis associated with decreased levels of Bax and cleaved caspase-3 expression, but increased Bcl-2 expression. EPC treatment significantly reduced the levels of serum proinflammatory factors, but elevated levels of interleukin-10. In contrast, the protective effect of EPCs were mitigated and abrogated by N5-(1-iminoethyl)-l-ornithine pretreatment.

CONCLUSIONS

Data indicated that EPC ameliorated LIRI by increasing eNOS expression.

Application potential of stem/progenitor cell-derived extracellular vesicles in renal diseases

Extracellular vesicles (EVs) are nanometer-sized and membrane-bound vesicles, including exosomes and microvesicles. EVs can deliver bioactive macromolecules such as proteins, lipids, and nucleic acids, allowing intercellular communication in multicellular organisms. EVs are secreted by all cell types including stem/progenitor cells. Stem/progenitor cell-derived EVs have been identified to exert immunomodulatory effects on target cells through transferring protein molecules as well as regulatory effects on the phenotype of target cells through fusion with the target cells membrane and/or through direct endocytosis by target cells to transfer nucleic acid substances (such as mRNA, miRNA) to the target cells. In both human and animal models, the use of stem/progenitor cells (such as bone marrow mesenchymal stromal cells) has been shown to promote the recovery of kidney diseases such as acute kidney injury and chronic kidney disease. Stem/progenitor cell-derived extracellular vesicles are an important mechanism by which stem/progenitor cells might repair kidney injury. Here, this review will discuss the latest advances concerning the application potential of stem/progenitor cell-derived extracellular vesicles in renal diseases, including the aspects as follows: anti-inflammatory, proliferation-promoting and anti-apoptotic, proangiogenic, antifibrotic and renal cancer progression-promoting. Therefore, stem/progenitor cell-derived extracellular vesicles may be a promising treatment tool for renal diseases.

Extracellular micro/nanovesicles rescue kidney from ischemia-reperfusion injury

Acute renal failure (ARF) is a clinical challenge that is highly resistant to treatment, and its high rate of mortality is alarming. Ischemia-reperfusion injury (IRI) is the most common cause of ARF. Especially IRI is implicated in kidney transplantation and can determine graft survival. Although the exact pathophysiology of renal IRI is unknown, the role of inflammatory responses has been elucidated. Because mesenchymal stromal cells (MSCs) have strong immunomodulatory properties, they are under extensive investigation as a therapeutic modality for renal IRI. Extracellular vesicles (EVs) play an integral role in cell-to-cell communication. Because the regenerative potential of the MSCs can be recapitulated by their EVs, the therapeutic appeal of MSC-derived EVs has dramatically increased in the past decade. Higher safety profile and ease of preservation without losing function are other advantages of EVs compared with their producing cells. In the current review, the preliminary results and potential of MSC-derived EVs to alleviate kidney IRI are summarized. We might be heading toward a cell-free approach to treat renal IRI.

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

Extracellular vesicles (EVs) are small lipid-based membrane-bound vesicles secreted by most cells under both physiological and pathological conditions. A key function of EVs is to mediate cell-cell communication via transferring mRNAs, miRNAs and proteins from parent cells to recipient cells. These unique features of EVs have spurred a renewed interest in their utility for therapeutics. Given the growing evidence for EV-mediated renal diseases, strategies that could block the release or uptake of pathogenic EVs will be discussed in this review. Then, the therapeutic potential of EVs predominantly from stem cells in renal diseases will be outlined. 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.

Vasculogenic Stem and Progenitor Cells in Human: Future Cell Therapy Product or Liquid Biopsy for Vascular Disease

New blood vessel formation in adults was considered to result exclusively from sprouting of preexisting endothelial cells, a process referred to angiogenesis. Vasculogenesis, the formation of new blood vessels from endothelial progenitor cells, was thought to occur only during embryonic life. Discovery of adult endothelial progenitor cells (EPCs) in 1997 opened the door for cell therapy in vascular disease. Endothelial progenitor cells contribute to vascular repair and are now well established as postnatal vasculogenic cells in humans. It is now admitted that endothelial colony-forming cells (ECFCs) are the vasculogenic subtype. ECFCs could be used as a cell therapy product and also as a liquid biopsy in several vascular diseases or as vector for gene therapy. However, despite a huge interest in these cells, their tissue and molecular origin is still unclear. We recently proposed that endothelial progenitor could come from very small embryonic-like stem cells (VSELs) isolated in human from CD133 positive cells. VSELs are small dormant stem cells related to migratory primordial germ cells. They have been described in bone marrow and other organs. This chapter discusses the reported findings from in vitro data and also preclinical studies that aimed to explore stem cells at the origin of vasculogenesis in human and then explore the potential use of ECFCs to promote newly formed vessels or serve as liquid biopsy to understand vascular pathophysiology and in particular pulmonary disease and haemostasis disorders.

MicroRNA-668 represses MTP18 to preserve mitochondrial dynamics in ischemic acute kidney injury

The pathogenesis of ischemic diseases remains unclear. Here we demonstrate the induction of microRNA-668 (miR-668) in ischemic acute kidney injury (AKI) in human patients, mice, and renal tubular cells. The induction was HIF-1 dependent, as HIF-1 deficiency in cells and kidney proximal tubules attenuated miR-668 expression. We further identified a functional HIF-1 binding site in the miR-668 gene promoter. Anti-miR-668 increased apoptosis in renal tubular cells and enhanced ischemic AKI in mice, whereas miR-668 mimic was protective. Mechanistically, anti-miR-668 induced mitochondrial fragmentation, whereas miR-668 blocked mitochondrial fragmentation during hypoxia. We analyzed miR-668 target genes through immunoprecipitation of microRNA-induced silencing complexes followed by RNA deep sequencing and identified 124 protein-coding genes as likely targets of miR-668. Among these genes, only mitochondrial protein 18 kDa (MTP18) has been implicated in mitochondrial dynamics. In renal cells and mouse kidneys, miR-668 mimic suppressed MTP18, whereas anti-miR-668 increased MTP18 expression. Luciferase microRNA target reporter assay further verified MTP18 as a direct target of miR-668. In renal tubular cells, knockdown of MTP18 suppressed mitochondrial fragmentation and apoptosis. Together, the results suggest that miR-668 is induced via HIF-1 in ischemic AKI and that, upon induction, miR-668 represses MTP18 to preserve mitochondrial dynamics for renal tubular cell survival and kidney protection.

Receptor-Ligand Interaction Mediates Targeting of Endothelial Colony Forming Cell-derived Exosomes to the Kidney after Ischemic Injury

Endothelial colony forming cell (ECFC)-derived exosomes protect mice against ischemic kidney injury, via transfer of microRNA-(miR)-486-5p. Mechanisms mediating exosome recruitment to tissues are unclear. We hypothesized that ECFC exosomes target ischemic kidneys, involving interaction between exosomal CXC chemokine receptor type 4 (CXCR4) and stromal cell-derived factor (SDF)-1α. Ischemia-reperfusion was induced in mice by bilateral renal vascular clamp, with intravenous infusion of exosomes at reperfusion. Optical imaging determined exosome biodistribution, and miR-486-5p was measured by real-time PCR. Human umbilical vein endothelial cells (HUVECs) were cultured to study the CXCR4/SDF-1α interaction. Targeting of administered exosomes to ischemic kidneys was detected 30 min and 4 hrs after reperfusion. Exosomes increased miR-486-5p levels only in kidneys, within proximal tubules, glomeruli, and endothelial cells. Uptake of fluorescently-labeled exosomes into HUVECs, and exosomal transfer of miR-486-5p were enhanced by hypoxia, effects blocked by neutralizing antibody to SDF-1α or by the CXCR4 inhibitor plerixafor. Infusion of ECFC exosomes prevented ischemic kidney injury in vivo, an effect that was not observed when exosomes were pre-incubated with plerixafor. These data indicate that ECFC exosomes selectively target the kidneys after ischemic injury, with rapid cellular transfer of miR486-5p. Targeting of exosomes may involve interaction of CXCR4 with endothelial cell SDF-1α.

Recent Advances in Endothelial Colony Forming Cells Toward Their Use in Clinical Translation

The term “Endothelial progenitor cell” (EPC) has been used to describe multiple cell populations that express endothelial surface makers and promote vascularisation. However, the only population that has all the characteristics of a real “EPC” is the Endothelial Colony Forming Cells (ECFC). ECFC possess clonal proliferative potential, display endothelial and not myeloid cell surface markers, and exhibit pronounced postnatal vascularisation ability in vivo. ECFC have been used to investigate endothelial molecular dysfunction in several diseases, as they give access to endothelial cells from patients in a non-invasive way. ECFC also represent a promising tool for revascularization of damaged tissue. Here we review the translational applications of ECFC research. We discuss studies which have used ECFC to investigate molecular endothelial abnormalities in several diseases and review the evidence supporting the use of ECFC for autologous cell therapy, gene therapy and tissue regeneration. Finally, we discuss ways to improve the therapeutic efficacy of ECFC in clinical applications, as well as the challenges that must be overcome to use ECFC in clinical trials for regenerative approaches.

The Vasoreparative Potential of Endothelial Colony Forming Cells: A Journey Through Pre-clinical Studies

For over a decade various cell populations have been investigated for their vasoreparative potential. Cells with the capacity to promote blood vessel regeneration are commonly known as endothelial progenitor cells (EPCs); although such a definition is currently considered too simple for the complexity of cell populations involved in the reparative angiogenic process. A subset of EPCs called endothelial colony forming cells (ECFCs) have emerged as a suitable candidate for cytotherapy, primarily due to their clonogenic progenitor characteristics, unequivocal endothelial phenotype, and inherent ability to promote vasculogenesis. ECFCs can be readily isolated from human peripheral and cord blood, expanded ex vivo and used to revascularize ischemic tissues. These cells have demonstrated efficacy in several in vivo preclinical models such as the ischemic heart, retina, brain, limb, lung and kidney. This review will summarize the current pre-clinical evidence for ECFC cytotherapy and discuss their potential for clinical application.

Distinct Anti-Fibrotic Effects of Exosomes Derived from Endothelial Colony-Forming Cells Cultured Under Normoxia and Hypoxia

Background

The therapeutic potential of endothelial colony-forming cells (ECFCs) may be impaired in an ischemic environment. Direct injection of ECFCs is not an effective method of rescuing the ischemic heart, but exosomes derived from these cells may be a promising therapeutic tool. However, exosomes produced under normoxia and hypoxia may not be identical. Therefore, the purpose of this study was to investigate alterations in the anti-fibrotic effects of hypoxia-treated ECFC-derived exosomes and the underlying mechanism involved.

Material/Methods

ECFCs were isolated from peripheral blood and exosomes were collected from ECFCs treated with normoxia (nor-exo) or hypoxia (hyp-exo). Effects of exosomes on cardiac fibroblast activation were evaluated in vitro. MicroRNAs (miRNAs) inside the exosomes were extracted and compared using next-generation RNA sequencing. Predicted target mRNAs of miR-10b-5p were validated using a dual-luciferase reporter gene assay method.

Results

Nor-exo significantly ameliorated cardiac fibroblast activation in vitro. These effects were attenuated in the hyp-exo-treated group. miR-10b-5p was enriched in nor-exo but not in hyp-exo. Dual-luciferase reporter gene assay found that both SMAD-specific E3 ubiquitin protein ligase 1 (Smurf1) and histone deacetylase 4 (HDAC4) mRNAs were inhibited by miR-10b-5p. The expression of neutral sphingomyelinase 2 (N-SMase2) was decreased in hypoxia ECFCs, and this result was consistent with the changes in miR-10b-5p in hyp-exo.

Conclusions

Due to a reduction of miR-10b-5p, which targets the fibrotic genes Smurf1 and HDAC4, the anti-fibrotic effects of hyp-exo were abolished.

miR-214 ameliorates acute kidney injury via targeting DKK3 and activating of Wnt/β-catenin signaling pathway

Background

miR-214 was demonstrated to be upregulated in models of renal disease and promoted fibrosis in renal injury independent of TGF-β signaling in vivo. However, the detailed role of miR-214 in acute kidney injury (AKI) and its underlying mechanism are still largely unknown.

Methods

In this study, an I/R-induced rat AKI model and a hypoxia-induced NRK-52E cell model were used to study AKI. The concentrations of kidney injury markers serum creatinine, blood urea nitrogen, and kidney injury molecule-1 were measured. The expressions of miR-214, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, were detected by RT-qPCR. The protein levels of Bcl-2, Bax, Dickkopf-related protein 3, β-catenin, c-myc, and cyclinD1 were determined by western blot. Cell apoptosis and caspase 3 activity were evaluated by flow cytometry analysis and caspase 3 activity assay, respectively. Luciferase reporter assay was used to confirm the interaction between miR-214 and Dkk3.

Results

miR-214 expression was induced in ischemia–reperfusion (I/R)-induced AKI rat and hypoxic incubation of NRK-52E cells. Overexpression of miR-214 alleviated hypoxia-induced NRK-52E cell apoptosis while inhibition of miR-214 expression exerted the opposite effect. Dkk3 was identified as a target of miR-214. Anti-miR-214 abolished the inhibitory effects of DKK3 knockdown on hypoxia-induced NRK-52E cell apoptosis by inactivation of Wnt/β-catenin signaling. Moreover, miR-214 ameliorated AKI in vivo by inhibiting apoptosis and fibrosis through targeting Dkk3 and activating Wnt/β-catenin pathway.

Conclusion

miR-214 ameliorates AKI by inhibiting apoptosis through targeting Dkk3 and activating Wnt/β-catenin signaling pathway, offering the possibility of miR-214 in the therapy of ischemic AKI.

Electronic supplementary material

The online version of this article (10.1186/s40659-018-0179-2) contains supplementary material, which is available to authorized users.

An Observational Cohort Feasibility Study to Identify Microvesicle and Micro-RNA Biomarkers of Acute Kidney Injury Following Pediatric Cardiac Surgery

OBJECTIVES

Micro-RNA, small noncoding RNA fragments involved in gene regulation, and microvesicles, membrane-bound particles less than 1 μm known to regulate cellular processes including responses to injury, may serve as disease-specific biomarkers of acute kidney injury. We evaluated the feasibility of measuring these signals as well as other known acute kidney injury biomarkers in a mixed pediatric cardiac surgery population.

DESIGN

Single center prospective cohort feasibility study.

SETTING

PICU.

PATIENTS

Twenty-four children (≤ 17 yr) undergoing cardiac surgery with cardiopulmonary bypass without preexisting inflammatory state, acute kidney injury, or extracorporeal life support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Acute kidney injury was defined according to modified Kidney Diseases Improving Global Outcomes criteria. Blood and urine samples were collected preoperatively and at 6-12 and 24 hours. Microvesicles derivation was assessed using flow cytometry and NanoSight analysis. Micro-RNAs were isolated from plasma and analyzed by microarray and quantitative real-time polymerase chain reaction. Data completeness for the primary outcomes was 100%. Patients with acute kidney injury (n = 14/24) were younger, underwent longer cardiopulmonary bypass, and required greater inotrope support. Acute kidney injury subjects had different fractional content of platelets and endothelial-derived microvesicles before surgery. Platelets and endothelial microvesicles levels were higher in acute kidney injury patients. A number of micro-RNA species were differentially expressed in acute kidney injury patients. Pathway analysis of candidate target genes in the kidney suggested that the most often affected pathways were phosphatase and tensin homolog and signal transducer and activator of transcription 3 signaling.

CONCLUSIONS

Microvesicles and micro-RNAs expression patterns in pediatric cardiac surgery patients can be measured in children and potentially serve as tools for stratification of patients at risk of acute kidney injury.

Stem/Stromal Cells for Treatment of Kidney Injuries With Focus on Preclinical Models

Within the last years, the use of stem cells (embryonic, induced pluripotent stem cells, or hematopoietic stem cells), Progenitor cells (e.g., endothelial progenitor cells), and most intensely mesenchymal stromal cells (MSC) has emerged as a promising cell-based therapy for several diseases including nephropathy. For patients with end-stage renal disease (ESRD), dialysis or finally organ transplantation are the only therapeutic modalities available. Since ESRD is associated with a high healthcare expenditure, MSC therapy represents an innovative approach. In a variety of preclinical and clinical studies, MSC have shown to exert renoprotective properties, mediated mainly by paracrine effects, immunomodulation, regulation of inflammation, secretion of several trophic factors, and possibly differentiation to renal precursors. However, studies are highly diverse; thus, knowledge is still limited regarding the exact mode of action, source of MSC in comparison to other stem cell types, administration route and dose, tracking of cells and documentation of therapeutic efficacy by new imaging techniques and tissue visualization. The aim of this review is to provide a summary of published studies of stem cell therapy in acute and chronic kidney injury, diabetic nephropathy, polycystic kidney disease, and kidney transplantation. Preclinical studies with allogeneic or xenogeneic cell therapy were first addressed, followed by a summary of clinical trials carried out with autologous or allogeneic hMSC. Studies were analyzed with respect to source of cell type, mechanism of action etc.

Endothelial colony-forming cell-derived exosomes restore blood-brain barrier continuity in mice subjected to traumatic brain injury

Traumatic brain injury (TBI) tends to cause disruption of the blood-brain barrier (BBB). Previous studies have shown that intravenously or intracerebroventricularly infused human umbilical cord blood-derived endothelial colony-forming cells (ECFCs) can home to injury sites and improve outcomes in mice subjected to experimental TBI. Several reports have demonstrated that these cells did not incorporate directly into newly formed vasculature but instead stimulated the proliferation and migration of tissue-resident endothelial cells (ECs) via paracrine mechanisms. In the present study, exosomes, which range from 30 to 150 nm in diameter, were isolated from ECFC-conditioned medium. The exosomes were labeled with PKH67 ex vivo, and we observed that they were taken up by ECs with high efficiency after 12 h of incubation. Pretreatment with ECFC-derived exosomes promoted the migration of ECs subjected to scratch injury, and incubating ECs exposed to hypoxia with ECFC-derived exosomes decreased PTEN expression, stimulated AKT phosphorylation and increased tight junction (TJ) protein expression in the cells. Furthermore, in vivo delivery of ECFC-derived exosomes into TBI mice also inhibited PTEN expression and increased AKT expression, changes accompanied by reductions in Evans blue (EB) dye extravasation, brain edema and TJ degradation. These data demonstrated that ECFC-derived exosomes have beneficial effects on BBB integrity in mice with TBI.

Exosomes and regenerative medicine: state of the art and perspectives

Exosomes have attracted the attention of the scientific community in recent years due to their widespread distribution, their possible functions as biomarkers of disease, and their great potential to be applied as therapeutic agents. Exosomes carry proteins and nucleic acids that can facilitate their uptake by distant target cells through endocytosis, such that exosomes could be targeted to a specific cell or cells to enhance or interfere with specific biological processes. This review will mainly focus on their roles in tissue repair and regenerative processes. Exosomal engineering and their potential applications in tissue regeneration are also reviewed here as an outlook for future research.

miR-486 inhibits PM2.5-induced apoptosis and oxidative stress in human lung alveolar epithelial A549 cells

Background

Environmental exposure to particulate matter 2.5 (PM2.5) threatens public health, which has caused worldwide concerns. MicroRNAs (miRNAs, miRs) participate in multiple biological regulation. Among them, miR-486 has been reported to be a beneficial molecule for cell survival in various cell types. However, the potential function of miR-486 in PM2.5-induced cytotoxic is still uncertain.

Methods

The expression of miR-486 was detected by quantitative real-time polymerase chain reaction (qRT-PCR) after A549 cells incubated with PM2.5. Then TUNEL staining and DCFH-DA fluorescence were used to test the apoptosis and ROS generation of A549 cells after exposed to PM2.5 with miR-486 mimic. Western blot was performed to determine the expression of Bax/Bcl2 ratio. In addition, western blot and rescue experiments were conducted to determine the target gene of miR-486.

Results

After treated with PM2.5, the expression of miR-486 was decreased. And miR-486 mimic treatment reduced cell apoptosis and reactive oxygen species (ROS) generation induced by PM2.5 exposure. Further studies showed that miR-486 negatively regulated the protein levels of PTEN and FOXO1. Rescue experiments demonstrated that PTEN and FOXO1 mediated the protective effects of miR-486 in PM2.5-treated human lung alveolar epithelial A549 cells.

Conclusions

Collectively, our findings identify that miR-486 relieves PM2.5-induced cell injury by targeting PTEN and FOXO1 in human lung alveolar epithelial A549 cells.

Endothelial Progenitor Cells and Kidney Diseases

Endothelial progenitor cells (EPC) are bone marrow derived or tissue-resident cells that play major roles in the maintenance of vascular integrity and repair of endothelial damage. Although EPCs may be capable of directly engrafting and regenerating the endothelium, the most important effects of EPCs seem to be depended on paracrine effects. In recent studies, specific microvesicles and mRNAs have been found to mediate the pro-angiogenic and regenerative effects of EPCs on endothelium. EPC counts have important prognostic implications in cardiovascular diseases (CVD). Uremia and inflammation are associated with lower EPC counts which probably contribute to increased CVD risks in patients with chronic kidney disease. Beneficial effects of the EPC therapies have been shown in studies performed on different models of CVD and kidney diseases such as acute and chronic kidney diseases and glomerulonephritis. However, lack of a clear definition and specific marker of EPCs is the most important problem causing difficulties in interpretation of the results of the studies investigating EPCs.

Advances in Hypoxia-Inducible Factor Biology

Hypoxia-inducible factor (HIF), a central regulator for detecting and adapting to cellular oxygen levels, transcriptionally activates genes modulating oxygen homeostasis and metabolic activation. Beyond this, HIF influences many other processes. Hypoxia, in part through HIF-dependent mechanisms, influences epigenetic factors, including DNA methylation and histone acetylation, which modulate hypoxia-responsive gene expression in cells. Hypoxia profoundly affects expression of many noncoding RNAs classes that have clinicopathological implications in cancer. HIF can regulate noncoding RNAs production, while, conversely, noncoding RNAs can modulate HIF expression. There is recent evidence for crosstalk between circadian rhythms and hypoxia-induced signaling, suggesting involvement of molecular clocks in adaptation to fluxes in nutrient and oxygen sensing. HIF induces increased production of cellular vesicles facilitating intercellular communication at a distance-for example, promoting angiogenesis in hypoxic tumors. Understanding the complex networks underlying cellular and genomic regulation in response to hypoxia via HIF may identify novel and specific therapeutic targets.

Podocyte-derived microparticles promote proximal tubule fibrotic signaling via p38 MAPK and CD36

Tubulointerstitial fibrosis is a hallmark of advanced diabetic kidney disease that is linked to a decline in renal function, however the pathogenic mechanisms are poorly understood. Microparticles (MPs) are 100–1000 nm vesicles shed from injured cells that are implicated in intercellular signalling. Our lab recently observed the formation of MPs from podocytes and their release into urine of animal models of type 1 and 2 diabetes and in humans with type 1 diabetes. The purpose of the present study was to examine the role of podocyte MPs in tubular epithelial cell fibrotic responses. MPs were isolated from the media of differentiated, untreated human podocytes (hPODs) and administered to cultured human proximal tubule epithelial cells (PTECs). Treatment with podocyte MPs increased p38 and Smad3 phosphorylation and expression of the extracellular matrix (ECM) proteins fibronectin and collagen type IV. MP-induced responses were attenuated by co-treatment with the p38 inhibitor SB202190. A transforming growth factor beta (TGF-β) receptor inhibitor (LY2109761) blocked MP-induced Smad3 phosphorylation and ECM protein expression but not p38 phosphorylation suggesting that these responses occurred downstream of p38. Finally, blockade of the class B scavenger receptor CD36 completely abrogated MP-mediated p38 phosphorylation, downstream Smad3 activation and fibronectin/collagen type IV induction. Taken together our results suggest that podocyte MPs interact with proximal tubule cells and induce pro-fibrotic responses. Such interactions may contribute to the development of tubular fibrosis in glomerular disease.

Endothelial colony-forming cells and pro-angiogenic cells: clarifying definitions and their potential role in mitigating acute kidney injury

Acute kidney injury (AKI) represents a significant clinical concern that is associated with high mortality rates and also represents a significant risk factor for the development of chronic kidney disease (CKD). This article will consider alterations in renal endothelial function in the setting of AKI that may underlie impairment in renal perfusion and how inefficient vascular repair may manifest post-AKI and contribute to the potential transition to CKD. We provide updated terminology for cells previously classified as 'endothelial progenitor' that may mediate vascular repair such as pro-angiogenic cells and endothelial colony-forming cells. We consider how endothelial repair may be mediated by these different cell types following vascular injury, particularly in models of AKI. We further summarize the potential ability of these different cells to mitigate the severity of AKI, improve perfusion and maintain vascular structure in pre-clinical studies.

Tissue regeneration using endothelial colony-forming cells: promising cells for vascular repair

Repairing and rebuilding damaged tissue in diseased human subjects remains a daunting challenge for clinical medicine. Proper vascular formation that serves to deliver blood-borne nutrients and adequate levels of oxygen and to remove wastes is critical for successful tissue regeneration. Endothelial colony-forming cells (ECFC) represent a promising cell source for revascularization of damaged tissue. ECFCs are identified by displaying a hierarchy of clonal proliferative potential and by pronounced postnatal vascularization ability in vivo. In this review, we provide a brief overview of human ECFC isolation and characterization, a survey of a number of animal models of human disease in which ECFCs have been shown to have prominent roles in tissue repair, and a summary of current challenges that must be overcome before moving ECFC into human subjects as a cell therapy.

Extracellular Vesicle MicroRNA Transfer in Lung Diseases

MicroRNAs (miRNAs) are single-stranded, small non-coding RNAs that ate involved in the transcriptional and post-transcriptional regulation of gene expression. Recently, miRNAs were demonstrated to be effectively delivered to a target cell or tissue from a host cell via extracellular vesicles (EVs). These EVs can be detected in blood, urine, exhaled breath condensates, bronchoalveolar lavage fluid (BALF), and other fluids. miRNAs are generated by donor cells and then packaged into EVs and delivered with intact functionality. After being delivered to the target cells, they regulate the translation of their target genes and the function of the target cells. Thus, EV transported miRNAs have become a new method for intercellular communication. EV miRNA transfer is well-documented in various pulmonary diseases, such as chronic obstructive pulmonary disease (COPD), asthma, pulmonary hypertension, and acute lung injury (ALI). In this review, we summarize the novel findings of EV miRNA transfer, focusing on the roles of miR-210, miR-200, miR-17, miR-146a, miR-155, and other miRNAs that are transported from primary human bronchial epithelial cells (HBECs), BALF, mesenchymal stem cells, and dendritic cells.

Genome-wide Profiling of Urinary Extracellular Vesicle microRNAs Associated With Diabetic Nephropathy in Type 1 Diabetes

Introduction

Diabetic nephropathy (DN) is a form of progressive kidney disease that often leads to end-stage renal disease (ESRD). It is initiated by microvascular complications due to diabetes. Although microalbuminuria (MA) is the earliest clinical indication of DN among patients with type 1 diabetes (T1D), it lacks the sensitivity and specificity to detect the early onset of DN. Recently, microRNAs (miRNAs) have emerged as critical regulators in diabetes as well as various forms of kidney disease, including renal fibrosis, acute kidney injury, and progressive kidney disease. Additionally, circulating extracellular miRNAs, especially miRNAs packaged in extracellular vesicles (EVs), have garnered significant attention as potential noninvasive biomarkers for various diseases and health conditions.

Methods

As part of the University of Pittsburgh Epidemiology of Diabetes Complications (EDC) study, urine was collected from individuals with T1D with various grades of DN or MA (normal, overt, intermittent, and persistent) over a decade at prespecified intervals. We isolated EVs from urine and analyzed the small-RNA using NextGen sequencing.

Results

We identified a set of miRNAs that are enriched in urinary EVs compared with EV-depleted samples, and identified a number of miRNAs showing concentration changes associated with DN occurrence, MA status, and other variables, such as hemoglobin A1c levels.

Conclusion

Many of the miRNAs associated with DN occurrence or MA status directly target pathways associated with renal fibrosis (including transforming growth factor-β and phosphatase and tensin homolog), which is one of the major contributors to the pathology of DN. These miRNAs are potential biomarkers for DN and MA.

Stem cell extracellular vesicles and kidney injury

Extracellular vesicles (EVs) appear as a new promising cell-free therapy for acute and chronic renal diseases. EVs retain characteristics of the cell of origin and those derived from stem cells may mimic their regenerative properties per se. In fact, EVs contain many active molecules such as proteins and RNA species that act on target cells through different mechanisms, stimulating proliferation and angiogenesis and reducing apoptosis and inflammation. There are several reports that demonstrate a general regenerative potential of EVs derived from mesenchymal stromal cells (MSCs) of different sources in kidney injury models. In addition, a promising new approach is the use of EVs in the graft perfusion solution for kidney conditioning before transplant. Here we summarize the application of EVs released by stem cells in preclinical models of acute and chronic renal damage, comparing animal models, use of EVs of different cell origin and of their sub-fractions, doses, route of administration and efficacy of treatment.