Mesenchymal Stem Cell-Derived Extracellular Vesicles Induce Regulatory T Cells to Ameliorate Chronic Kidney Injury

Extracellular vesicles and their effect on vascular haemodynamics: a systematic review

Extracellular vesicles (EVs) are released from all cell types studied to date and act as intercellular communicators containing proteins, nucleic acids and lipid cargos. They have been shown to be involved in maintaining homoeostasis as well as playing a role in the development of pathology including hypertension and cardiovascular disease. It is estimated that there is 109-1010 circulating EVs/mL in the plasma of healthy individuals derived from various sources. While the effect of EVs on vascular haemodynamic parameters will be dependent on the details of the model studied, we systematically searched and summarized current literature to find patterns in how exogenously injected EVs affected vascular haemodynamics. Under homoeostatic conditions, evidence from wire and pressure myography data demonstrate that injecting isolated EVs derived from cell types found in blood and blood vessels resulted in the impairment of vasodilation in blood vessels ex vivo. Impaired vasodilation was also observed in rodents receiving intravenous injections of human plasma EVs from cardiovascular diseases including valvular heart disease, acute coronary syndrome, myocardial infarction and end stage renal disease. When EVs were derived from models of metabolic syndromes, such as diabetes, these EVs enhanced vasoconstriction responses in blood vessels ex vivo. There were fewer publications that assessed the effect of EVs in anaesthetised or conscious animals to confirm whether effects on the vasculature observed in ex vivo studies translated into alterations in vascular haemodynamics in vivo. In the available conscious animal studies, the in vivo data did not always align with the ex vivo data. This highlights the importance of in vivo work to determine the effects of EVs on the integrative vascular haemodynamics.

Engineered Extracellular Vesicles in Chronic Kidney Diseases: A Comprehensive Review

Chronic kidney diseases (CKD) present a formidable global health challenge, characterized by a deficiency of effective treatment options. Extracellular vesicles (EVs), recognized as multifunctional drug delivery systems in biomedicine, have gained accumulative interest. Specifically, engineered EVs have emerged as a promising therapeutic approach for targeted drug delivery, potentially addressing the complexities of CKD management. In this review, we systematically dissect EVs, elucidating their classification, biogenesis, composition, and cargo molecules. Furthermore, we explore techniques for EV engineering and strategies for their precise renal delivery, focusing on cargo loading and transportation, providing a comprehensive perspective. Moreover, this review also discusses and summarizes the diverse therapeutic applications of engineered EVs in CKD, emphasizing their anti-inflammatory, immunomodulatory, renoprotective, and tissue-regenerating effects. It critically evaluates the challenges and limitations in translating EV therapies from laboratory settings to clinical applications, while outlining future prospects and emerging trends.

Therapeutic Effects of Mesenchymal/Stromal Stem Cells and Their Derived Extracellular Vesicles in Rheumatoid Arthritis

Currently available therapies for rheumatoid arthritis (RA) are inadequate to alleviate the inflammation and reduce joint damage. While the immune-regulatory effect of human mesenchymal/stromal stem cells (MSCs) extracellular vesicles (EVs) has been tested in many inflammation-related diseases, little is known regarding their effect on patients with RA. Thus, we assessed the effect of human MSCs and MSC-EVs (from naïve or IFN-β-primed MSCs) on CD4+ T cells from patients with RA. Moreover, we investigated the effect of MSC-EVs on RA patients-derived synovial fibroblasts (FLS). MSC-EVs were prepared using a PEG precipitation followed by ultracentrifugation-based protocol. Applied to RA CD4+ T cells, EVs from IFN-β-primed MSCs, suppressed the expression of more key RA-associated cytokines (IL-4, GM-CSF IFN-γ, IL-2, TNF-α), and decreased CD4+ T-cell polyfunctionality than MSCs or EVs from naïve MSCs. MSCs mediated a slight decrease in the frequency of T-regulatory cells, while MSC-EVs rescued the frequency of T-regulatory cells. MSCs significantly inhibited CD4+ T-cell proliferation (P < .05), while no inhibition was observed in response to EV preparations. EVs from IFN-β-primed MSCs inhibited (P < .01) RA FLS migration and downregulated (P < .05) RA FLS surface markers CD34 and HLA-DR. Collectively, we demonstrated the immune-modulatory function of MSCs and their derived EVs in RA CD4+ T cells, which could be further enhanced by priming MSCs with IFN-β. Moreover, EVs from IFN-β-primed MSCs more efficiently inhibit RA FLS migration, and expression of RA FLS-related surface markers, suggesting these EVs as a potent therapy for RA.

Mesenchymal stromal cells and their small extracellular vesicles in allergic diseases: From immunomodulation to therapy

Mesenchymal stromal cells (MSCs) have long been considered a potential tool for treatment of allergic inflammatory diseases, owing to their immunomodulatory characteristics. In recent decades, the medical utility of MSCs has been evaluated both in vitro and in vivo, providing a foundation for therapeutic applications. However, the existing limitations of MSC therapy indicate the necessity for novel therapies. Notably, small extracellular vesicles (sEV) derived from MSCs have emerged rapidly as candidates instead of their parental cells. The acquisition of abundant and scalable MSC-sEV is an obstacle for clinical applications. The potential application of MSC-sEV in allergic diseases has attracted increasing attention from researchers. By carrying biological microRNAs or active proteins, MSC-sEV can modulate the function of various innate and adaptive immune cells. In this review, we summarise the recent advances in the immunomodulatory properties of MSCs in allergic diseases, the cellular sources of MSC-sEV, and the methods for obtaining high-quality human MSC-sEV. In addition, we discuss the immunoregulatory capacity of MSCs and MSC-sEV for the treatment of asthma, atopic dermatitis, and allergic rhinitis, with a special emphasis on their immunoregulatory effects and the underlying mechanisms of immune cell modulation.

Sinomenine improves renal fibrosis by regulating mesenchymal stem cell-derived exosomes and affecting autophagy levels

BACKGROUND

This study attempts to investigate the therapeutic effect of sinomenine on renal fibrosis and its mechanism.

METHODS

The 8-week-old C57BL/6 male mice were randomly divided into sham group, UUO model group, UUO sinomenine group (UUO + Sino 50), UUO + sinomenine group (UUO + Sino 100), UUO + exosome group (exo), and UUO + exo-inhibitor. The pathological changes of kidney were observed by H&E staining, the degree of renal interstitial fibrosis was detected by MASSON and Sirius red staining, and the expressions of fibrosis and autophagy markers were detected by real-time fluorescence quantitative PCR and WB. NTA and electron microscopy were used to analyze exo secretion after sinomenine treatment.

RESULTS

Sinomenine could improve the progression of renal fibrosis without causing tissue damage including heart, lungs and liver. Sinomenine could promote autophagosome formation. It could promote the secretion of exosomes from bone marrow mesenchymal stem cells (BMSCs). Sinomine regulates the PI3K-AKT pathway through BMSC-exo carrying miR-204-5p, affecting autophagy level and alleviating the process of renal fibrosis.

CONCLUSION

Our study suggests that sinomine could improve the progression of renal fibrosis by influencing the expression of miR-204-5p in BMSC-exo and regulating the PI3K-AKT pathway.

Obesity Blunts the Effect of Mesenchymal Stem Cell-Derived Extracellular Vesicles

Introduction

Mesenchymal stem/stromal cell-derived extracellular vesicles (MSC-EVs) are paracrine vectors with therapeutic functions comparable to their parent cells. However, it remains unclear if donor obesity affects their therapeutic functions. We tested the hypothesis that the curative effect of human adipose tissue-derived MSC-EVs (A-MSC-EVs) is blunted by obesity.

Methods

MSC-EVs were isolated by ultracentrifugation from mesenchymal stem/stromal cells (MSCs) collected from abdominal subcutaneous fat of obese and lean human subjects (obese and lean-MSC-EVs, respectively) and injected into the aorta of mice 2 weeks after renal artery stenosis (RAS) induction. Magnetic resonance imaging studies were conducted 2 weeks after MSC-EVs delivery to determine renal function. The effect of MSC-EVs on tissue injury was assessed by histology and gene expression of inflammatory factors, including interleukin (IL)-1β, IL-6, monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-α). Oxidative damage, macrophage infiltration, plasma renin, and hypoxia inducible factor-1α (HIF-1α) were also assessed.

Results

Tracking showed that MSC-EVs localized in the kidney tissue, including glomeruli and tubules. All MSC-EVs decreased systolic blood pressure (SBP) and plasma renin and improved the poststenotic kidney (STK) volume, but obese-MSC-EVs were less effective than lean-MSC-EVs in improving medullary hypoxia, fibrosis, and tubular injury. Lean-MSC-EVs decreased inflammation, whereas obesity attenuated this effect. Only lean-MSC-EVs decreased STK cortical HIF-1α expression.

Conclusion

Obesity attenuates the antihypoxia, antifibrosis, antiinflammation, and tubular repair functions of human MSC-EVs in chronic ischemic kidney disease. These observations may have implications for the self-repair potency of obese subjects and for the use of autologous MSC-EVs in regenerative medicine.

Serum Nutritional Biomarkers and All-Cause and Cause-Specific Mortality in U.S. Adults with Metabolic Syndrome: The Results from National Health and Nutrition Examination Survey 2001-2006

BACKGROUND

There is limited research on the associations between serum nutritional biomarkers and mortality risk in patients with metabolic syndrome (MetS). Existing studies merely investigated the single-biomarker effect. Thus, this study aimed to investigate the combined effect of nutritional biomarker mixtures and mortality risk using the Bayesian kernel machine regression (BKMR) model in patients with MetS.

METHODS

We included the MetS patients, defined according to the 2018 Guideline on the Management of Blood Cholesterol from the National Health and Nutrition Examination Survey (NHANES) 2001-2006. A total of 20 serum nutritional biomarkers were measured and evaluated in this study. The Cox proportional hazard model and restricted cubic spline models were used to evaluate the individual linear and non-linear association of 20 nutritional biomarkers with mortality risk. Bayesian kernel machine regression (BKMR) was used to assess the associations between mixture of nutritional biomarkers and mortality risk.

RESULTS

A total of 1455 MetS patients had a median age of 50 years (range: 20-85). During a median of 17.1-year follow-up, 453 (24.72%) died: 146 (7.20%) caused by CVD and 87 (5.26%) by cancer. Non-linear and linear analyses indicated that, in total, eight individual biomarkers (α-carotene, β-carotene, bicarbonate, lutein/zeaxanthin, lycopene, potassium, protein, and vitamin A) were significantly associated with all-cause mortality (all p-values < 0.05). Results from BKMR showed an association between the low levels of the mixture of nutritional biomarkers and high risk of all-cause mortality with the estimated effects ranging from 0.04 to 0.14 (referent: medians). α-Carotene (PIP = 0.971) and potassium (PIP = 0.796) were the primary contributors to the combined effect of the biomarker mixture. The nutritional mixture levels were found to be negatively associated with the risk of cardiovascular disease (CVD) mortality and positively associated with the risk of cancer mortality. After it was stratified by nutrients, the mixture of vitamins showed a negative association with all-cause and CVD mortality, whereas the mixture of mineral-related biomarkers was positively associated with all-cause and cancer mortality.

CONCLUSION

Our findings support the evidence that nutritional status was associated with long-term health outcomes in MetS patients. It is necessary for MetS patients to be concerned with certain nutritional status (i.e., vitamins and mineral elements).

Intrapericardial Exosome Therapy Dampens Cardiac Injury via Activating Foxo3

BACKGROUND

Mesenchymal stem cell (MSC)-derived exosomes are well recognized immunomodulating agents for cardiac repair, while the detailed mechanisms remain elusive. The Pericardial drainage pathway provides the heart with immunosurveillance and establishes a simplified model for studying the mechanisms underlying the immunomodulating effects of therapeutic exosomes.

METHODS

Myocardial infarction (MI) models with and without pericardiectomy (corresponding to Tomy MI and NonTomy MI) were established to study the functions of pericardial drainage pathway in immune activation of cardiac-draining mediastinal lymph node (MLN). Using the NonTomy MI model, MSC exosomes or vehicle PBS was intrapericardially injected for MI treatment. Via cell sorting and RNA-seq (RNA-sequencing) analysis, the differentially expressed genes were acquired for integrated pathway analysis to identify responsible mechanisms. Further, through functional knockdown/inhibition studies, application of cytokines and neutralizing antibodies, western blot, flow cytometry, and cytokine array, the molecular mechanisms were studied. In addition, the therapeutic efficacy of intrapericardially injected exosomes for MI treatment was evaluated through functional and histological analyses.

RESULTS

We show that the pericardial draining pathway promoted immune activation in the MLN following MI. Intrapericardially injected exosomes accumulated in the MLN and induced regulatory T cell differentiation to promote cardiac repair. Mechanistically, uptake of exosomes by major histocompatibility complex (MHC)-II+ antigen-presenting cells (APCs) induced Foxo3 activation via the protein phosphatase (PP)-2A/p-Akt/forkhead box O3 (Foxo3) pathway. Foxo3 dominated APC cytokines (IL-10, IL-33, and IL-34) expression and built up a regulatory T cell (Treg)-inducing niche in the MLN. The differentiation of Tregs as well as their cardiac deployment were elevated, which contributed to cardiac inflammation resolution and cardiac repair.

CONCLUSIONS

This study reveals a novel mechanism underlying the immunomodulation effects of MSC exosomes and provides a promising candidate (PP2A/p-Akt/Foxo3 signaling pathway) with a favorable delivery route (intrapericardial injection) for cardiac repair.

Extracellular vesicles as advanced therapeutics for the resolution of organ fibrosis: Current progress and future perspectives

Organ fibrosis is a serious health challenge worldwide, and its global incidence and medical burden are increasing dramatically each year. Fibrosis can occur in nearly all major organs and ultimately lead to organ dysfunction. However, current clinical treatments cannot slow or reverse the progression of fibrosis to end-stage organ failure, and thus advanced anti-fibrotic therapeutics are urgently needed. As a type of naturally derived nanovesicle, native extracellular vesicles (EVs) from multiple cell types (e.g., stem cells, immune cells, and tissue cells) have been shown to alleviate organ fibrosis in many preclinical models through multiple effective mechanisms, such as anti-inflammation, pro-angiogenesis, inactivation of myofibroblasts, and fibrinolysis of ECM components. Moreover, the therapeutic potency of native EVs can be further enhanced by multiple engineering strategies, such as genetic modifications, preconditionings, therapeutic reagent-loadings, and combination with functional biomaterials. In this review, we briefly introduce the pathology and current clinical treatments of organ fibrosis, discuss EV biology and production strategies, and particularly focus on important studies using native or engineered EVs as interventions to attenuate tissue fibrosis. This review provides insights into the development and translation of EV-based nanotherapies into clinical applications in the future.

Liver mesenchymal stem cells are superior inhibitors of NK cell functions through differences in their secretome compared to other mesenchymal stem cells

Liver-resident mesenchymal stem cells (L-MSCs) are superior inhibitors of alloreactive T cell responses compared to their counterparts from bone marrow (BM-MSCs) or adipose tissue (A-MSCs), suggesting a role in liver’s overall tolerogenic microenvironment. Whether L-MSCs also impact NK cell functions differently than other MSCs is not known. We generated and characterized L-MSCs, A-MSCs and BM-MSCs from human tissues. The mass spectrometry analysis demonstrated that L-MSC secretome is uniquely different than that of A-MSC/BM-MSC, with enriched protein sets involved in IFNγ responses and signaling. When co-cultured with primary human NK cells, L-MSCs but not other MSCs, decreased surface expression of activating receptors NKp44 and NKG2D. L-MSCs also decreased IFNγ secretion by IL-2-stimulated NK cells more effectively than other MSCs. Cytolytic function of NK cells were reduced significantly when co-cultured with L-MSCs, whereas A-MSCs or BM-MSCs did not have a major impact. Mechanistic studies showed that the L-MSC-mediated reduction in NK cell cytotoxicity is not through changes in secretion of the cytotoxic proteins Perforin, Granzyme A or B, but through increased production of HLA-C1 found in L-MSC secretome that inhibits NK cells by stimulating their inhibitory receptor KIRDL2/3. L-MSCs are more potent inhibitors of NK cell functions than A-MSC or BM-MSC. Combined with their T cell inhibitory features, these results suggest L-MSCs contribute to the tolerogenic liver microenvironment and liver-induced systemic tolerance often observed after liver transplantation.

Extracellular Vesicles as Theranostic Tools in Kidney Disease

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

Recent advances of the mammalian target of rapamycin signaling in mesenchymal stem cells

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase involved in a variety of cellular functions, such as cell proliferation, metabolism, autophagy, survival and cytoskeletal organization. Furthermore, mTOR is made up of three multisubunit complexes, mTOR complex 1, mTOR complex 2, and putative mTOR complex 3. In recent years, increasing evidence has suggested that mTOR plays important roles in the differentiation and immune responses of mesenchymal stem cells (MSCs). In addition, mTOR is a vital regulator of pivotal cellular and physiological functions, such as cell metabolism, survival and ageing, where it has emerged as a novel therapeutic target for ageing-related diseases. Therefore, the mTOR signaling may develop a large impact on the treatment of ageing-related diseases with MSCs. In this review, we discuss prospects for future research in this field.

Case report: effect of umbilical cord mesenchymal stem cells on immunoglobulin A nephropathy after acute renal failure

Immunoglobulin A nephropathy is an inflammatory, autoimmune condition that may lead to renal impairment in its most aggressive forms. In this case report, a 50-year-old male with acute renal failure was diagnosed with IgA nephropathy, having elevated creatinine levels (3.0 mg/dL) and hypertension. He received intravenous infusions of a total of 120 million umbilical cord-derived mesenchymal stem cells (UC-MSCs) and was followed-up for 6 months. No adverse events were reported during or after administration or any of the follow-up visits. Creatinine levels decreased to and remained normal (1.0 mg/dL) in the 6 months following treatment. Anti-hypertensive medications were no longer needed. UC-MSC administration was safe, well-tolerated, and beneficial for this patient with IgA nephropathy.

Extracellular vesicles for renal therapeutics: State of the art and future perspective

With the ever-increasing burden of kidney disease, the need for developing new therapeutics to manage this disease has never been greater. Extracellular vesicles (EVs) are natural membranous nanoparticles present in virtually all organisms. Given their excellent delivery capacity in the body, EVs have emerged as a frontier technology for drug delivery and have the potential to usher in a new era of nanomedicine for kidney disease. This review is focused on why EVs are such compelling drug carriers and how to release their fullest potentiality in renal therapeutics. We discuss the unique features of EVs compared to artificial nanoparticles and outline the engineering technologies and steps in developing EV-based therapeutics, with an emphasis on the emerging approaches to target renal cells and prolong kidney retention. We also explore the applications of EVs as natural therapeutics or as drug carriers in the treatment of renal disorders and present our views on the critical challenges in manufacturing EVs as next-generation renal therapeutics.

Extracellular vesicles in kidney disease

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

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

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

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

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

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

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

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

Effects of obesity on reparative function of human adipose tissue-derived mesenchymal stem cells on ischemic murine kidneys

Introduction:

Obesity is a health burden that impairs cellular processes. Mesenchymal stem/stromal cells (MSCs) are endowed with reparative properties and can ameliorate renal injury. Obesity impairs human MSC function in-vitro, but its effect on their in-vivo reparative potency remains unknown.

Subjects and Methods:

Abdominal adipose tissue-derived MSC were harvested from patients without (‘lean’) or with obesity (‘obese’) (body mass index<30 or ≥30kg/m², respectively) during kidney donation or bariatric surgery, respectively. MSC (5x10⁵/200μL) or vehicle were then injected into 129S1 mice 2 weeks after renal artery stenosis (RAS) or sham surgery (n=8/group). Two weeks later, mice underwent magnetic resonance imaging to assess renal perfusion and oxygenation in-vivo, and kidneys then harvested for ex-vivo studies.

Results:

Similar numbers of lean and obese-MSCs engrafted in stenotic mouse kidneys. Vehicle-treated RAS mice had reduced stenotic-kidney cortical and medullary perfusion and oxygenation. Lean (but not obese) MSC normalized ischemic kidney cortical perfusion, whereas both effectively mitigated renal hypoxia. Serum creatinine and blood pressure were elevated in RAS mice and lowered only by lean-MSC. Both types of MSCs alleviated stenotic-kidney fibrosis, but lean-MSC more effectively than obese-MSC. MSC senescence-associated beta-gal activity, and gene expression of p16, p21, and vascular endothelial growth factor correlated with recipient kidney perfusion and tissue injury, linking MSC characteristics with their in-vivo reparative capacity.

Discussion:

Human obesity impairs the reparative properties of adipose-tissue-derived MSCs, possibly by inducing cellular senescence. Dysfunction and senescence of the endogenous MSC repair system in patients with obesity may warrant targeting interventions to restore MSC vitality.

Mesenchymal Stem Cell-Derived Extracellular Vesicles in Liver Immunity and Therapy

Mesenchymal stem cells (MSCs), as the most common cell source for stem cell therapy, play an important role in the modulation of innate and adaptive immune responses and have been widely used in clinical trials to treat autoimmune and inflammatory diseases. Recent experimental and clinical studies have shown that MSC-derived extracellular vesicles (MSC-EVs) can inhibit the activation and proliferation of a variety of proinflammatory cells, such as Th1, Th17 and M1 macrophages, reducing the secretion of proinflammatory cytokines, while promoting the proliferation of anti-inflammatory cells, such as M2 macrophages and Tregs, and increasing the secretion of anti-inflammatory cytokines, thus playing a role in immune regulation and exhibiting immunomodulatory functions. Besides MSC-EVs are more convenient and less immunogenic than MSCs. There is growing interest in the role of MSC-EVs in liver diseases owing to the intrinsic liver tropism of MSC-EVs. In this review, we focus on the immunomodulatory effects of MSC-EVs and summarize the pivotal roles of MSC-EVs as a cell-free therapy in liver diseases, including NAFLD, AIH, acute liver failure, liver fibrosis and hepatic ischemia–reperfusion injury. Moreover, we provide a concise overview of the potential use and limits of MSC-EVs in clinical application.

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments.

Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis.

Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

Mesenchymal Stem/Stromal Cell-Derived Extracellular Vesicles for Chronic Kidney Disease: Are We There Yet?

Mesenchymal stem/stromal cells (MSCs) are the most utilized cell type for cellular therapy, partly due to their important proliferative potential and ability to differentiate into various cell types. MSCs produce large amounts of extracellular vesicles (EVs), which carry genetic and protein cargo to mediate MSC paracrine function. Recently, MSC-derived EVs have been successfully used in several preclinical models of chronic kidney disease. However, uncertainty remains regarding EV fate, safety, and long-term effects, which might impose important limitations on their path to clinical translation. This review discusses the therapeutic application of MSC-derived EV therapy for renal disease, with particular emphasis on potential mechanisms of kidney repair and major translational barriers. Emerging evidence indicates that the cargo of MSC-derived EVs is capable of modulating several pathways responsible for renal injury, including inflammation, oxidative stress, apoptosis, fibrosis, and microvascular remodeling. EV-induced modulation of these pathways has been associated with important renoprotective effects in experimental studies. However, scarce clinical data are available, and several challenges need to be addressed as we move toward clinical translation, including standardization of methods for EV isolation and characterization, EV fate, duration of EV effects, and effects of cardiovascular risk factors. MSC-derived EVs have the potential to preserve renal structure and function, but further experimental and clinical evidence is needed to confirm their protective effects in patients with chronic kidney disease.

Extracellular Vesicles in Organ Fibrosis: Mechanisms, Therapies, and Diagnostics

Fibrosis is the unrelenting deposition of excessively large amounts of insoluble interstitial collagen due to profound matrigenic activities of wound-associated myofibroblasts during chronic injury in diverse tissues and organs. It is a highly debilitating pathology that affects millions of people globally and leads to decreased function of vital organs and increased risk of cancer and end-stage organ disease. Extracellular vesicles (EVs) produced within the chronic wound environment have emerged as important vehicles for conveying pro-fibrotic signals between many of the cell types involved in driving the fibrotic response. On the other hand, EVs from sources such as stem cells, uninjured parenchymal cells, and circulation have in vitro and in vivo anti-fibrotic activities that have provided novel and much-needed therapeutic options. Finally, EVs in body fluids of fibrotic individuals contain cargo components that may have utility as fibrosis biomarkers, which could circumvent current obstacles to fibrosis measurement in the clinic, allowing fibrosis stage, progression, or regression to be determined in a manner that is accurate, safe, minimally-invasive, and conducive to repetitive testing. This review highlights the rapid and recent progress in our understanding of EV-mediated fibrotic pathogenesis, anti-fibrotic therapy, and fibrosis staging in the lung, kidney, heart, liver, pancreas, and skin.

Mesenchymal Stem Cell-Derived Extracellular Vesicles to the Rescue of Renal Injury

Acute kidney injury (AKI) and chronic kidney disease (CKD) are rising in global prevalence and cause significant morbidity for patients. Current treatments are limited to slowing instead of stabilising or reversing disease progression. In this review, we describe mesenchymal stem cells (MSCs) and their constituents, extracellular vesicles (EVs) as being a novel therapeutic for CKD. MSC-derived EVs (MSC-EVs) are membrane-enclosed particles, including exosomes, which carry genetic information that mimics the phenotype of their cell of origin. MSC-EVs deliver their cargo of mRNA, miRNA, cytokines, and growth factors to target cells as a form of paracrine communication. This genetically reprograms pathophysiological pathways, which are upregulated in renal failure. Since the method of exosome preparation significantly affects the quality and function of MSC-exosomes, this review compares the methodologies for isolating exosomes from MSCs and their role in tissue regeneration. More specifically, it summarises the therapeutic efficacy of MSC-EVs in 60 preclinical animal models of AKI and CKD and the cargo of biomolecules they deliver. MSC-EVs promote tubular proliferation and angiogenesis, and inhibit apoptosis, oxidative stress, inflammation, the epithelial-to-mesenchymal transition, and fibrosis, to alleviate AKI and CKD. By reprogramming these pathophysiological pathways, MSC-EVs can slow or even reverse the progression of AKI to CKD, and therefore offer potential to transform clinical practice.

The Nephroprotective Properties of Extracellular Vesicles in Experimental Models of Chronic Kidney Disease: a Systematic Review

Extracellular vesicle (EV)-based therapy was hypothesized as a promising regenerative approach which has led to intensive research of EVs in various pathologies. In this study, we performed a comprehensive systematic review of the current experimental evidence regarding the protective properties of EVs in chronic kidney disease (CKD). We evaluated the EV-based experiments, EV characteristics, and effector molecules with their involvement in CKD pathways. Including all animal records with available creatinine or urea data, we performed a stratified univariable meta-analysis to assess the determinants of EV-based therapy effectiveness. We identified 35 interventional studies that assessed nephroprotective role of EVs and catalogued them according to their involvement in CKD mechanism. Systematic assessment of these studies suggested that EVs had consistently improved glomerulosclerosis, interstitial fibrosis, and cell damage, among different CKD models. Moreover, EV-based therapy reduced the progression of renal decline in CKD. The stratified analyses showed that the disease model, administered dose, and time of therapeutic intervention were potential predictors of therapeutic efficacy. Together, EV therapy is a promising approach for CKD progression in experimental studies. Further standardisation of EV-methods, continuous improvement of the study quality, and better understanding of the determinants of EV effectiveness will facilitate preclinical research, and may help development of clinical trials in people with CKD.

Mesenchymal Stem Cell Protects Injured Renal Tubular Epithelial Cells by Regulating mTOR-Mediated Th17/Treg Axis

The increase in T helper 17 cell (Th17)-mediated pro-inflammatory response and decrease in regulatory T cell (Treg)-mediated anti-inflammatory effect aggravate renal tubular epithelial cell (RTEC) injury. However, increasing evidence indicated that mesenchymal stem cell (MSC) possessed the ability to control the imbalance between Th17 and Treg. Given that Th17 and Treg are derived from a common CD4⁺ T cell precursor, we summarize the current knowledge of MSC-mediated inhibition of the mammalian target of rapamycin (mTOR), which is a master regulator of CD4⁺ T cell polarization. During CD4⁺ T cell differentiation, mTOR signaling mediates Th17 and Treg differentiation via hypoxia-inducible factor-1α (HIF-1α)-dependent metabolic regulation and signaling pathway, as well as mTOR-mediated phosphorylation of signal transducer and activator of transcription (STAT) 3 and 5. Through interfering with mTOR signaling, MSC restrains CD4⁺ T cell differentiation into Th17, but in turn promotes Treg generation. Thus, this review indicates that MSC-mediated Th17-to-Treg polarization is expected to act as new immunotherapy for kidney injury.

Extracellular Vesicles as a Therapeutic Tool for Kidney Disease: Current Advances and Perspectives

Extracellular vesicles (EVs) have been described as important mediators of cell communication, regulating several physiological processes, including tissue recovery and regeneration. In the kidneys, EVs derived from stem cells have been shown to support tissue recovery in diverse disease models and have been considered an interesting alternative to cell therapy. For this purpose, however, several challenges remain to be overcome, such as the requirement of a high number of EVs for human therapy and the need for optimization of techniques for their isolation and characterization. Moreover, the kidney’s complexity and the pathological process to be treated require that EVs present a heterogeneous group of molecules to be delivered. In this review, we discuss the recent advances in the use of EVs as a therapeutic tool for kidney diseases. Moreover, we give an overview of the new technologies applied to improve EVs’ efficacy, such as novel methods of EV production and isolation by means of bioreactors and microfluidics, bioengineering the EV content and the use of alternative cell sources, including kidney organoids, to support their transfer to clinical applications.

The Micro-RNA Cargo of Extracellular Vesicles Released by Human Adipose Tissue-Derived Mesenchymal Stem Cells Is Modified by Obesity

Obesity is a chronic disease that interferes with normal repair processes, including adipose mesenchymal stem/stromal cells (ASCs) function. ASCs produce extracellular vesicles (EVs) that activate a repair program in recipient cells partly via their micro-RNA (miRNA) cargo. We hypothesized that obesity alters the miRNA expression profile of human ASC-derived EVs, limiting their capacity to repair injured cells. Human ASCs were harvested from obese and age- and gender-matched non-obese (lean) subjects during bariatric or cosmetic surgeries, respectively (n = 5 each), and their EVs isolated. Following high-throughput sequencing analysis, differentially expressed miRNAs were identified and their gene targets classified based on cellular component, molecular function, and biological process. The capacity of human lean- and obese-EVs to modulate inflammation, apoptosis, as well as mitogen-activated protein kinase (MAPK) and Wnt signaling in injured human proximal tubular epithelial (HK2) cells was evaluated in vitro. The number of EVs released from lean- and obese-ASCs was similar, but obese-EVs were smaller compared to lean-EVs. Differential expression analysis revealed 8 miRNAs upregulated (fold change > 1.4, p < 0.05) and 75 downregulated (fold change < 0.7, p < 0.05) in obese-EVs vs. lean-EVs. miRNAs upregulated in obese-EVs participate in regulation of NFk-B and MAPK signaling, cytoskeleton organization, and apoptosis, whereas those downregulated in obese-EVs are implicated in cell cycle, angiogenesis, and Wnt and MAPK signaling. Treatment of injured HK2 cells with obese-EVs failed to decrease inflammation, and they decreased apoptosis and MAPK signaling significantly less effectively than their lean counterparts. Obesity alters the size and miRNA cargo of human ASC-derived EVs, as well as their ability to modulate important injury pathways in recipient cells. These observations may guide development of novel strategies to improve healing and repair in obese individuals.

Porcine models of acute kidney injury

Pigs represent a potentially attractive model for medical research. Similar body size and physiological patterns of kidney injury that more closely mimic those described in humans make larger animals attractive for experimentation. Using larger animals, including pigs, to investigate the pathogenesis of acute kidney injury (AKI) also serves as an experimental bridge, narrowing the gap between clinical disease and preclinical discoveries. This article compares the advantages and disadvantages of large versus small AKI animal models and provides a comprehensive overview of the development and application of porcine models of AKI induced by clinically relevant insults, including ischemia-reperfusion, sepsis, and nephrotoxin exposure. The primary focus of this review is to evaluate the use of pigs for AKI studies by current investigators, including areas where more information is needed.

Urinary exosomal CD26 is associated with recovery from acute kidney injury in intensive care units: a prospective cohort study

OBJECTIVES

Currently there is no validated method to predict renal reversal and recovery after acute kidney injury (AKI). As exosomes have the potential for AKI prognosis and CD26 is involved in the mechanisms in AKI, this study aims to investigate whether urinary exosomal CD26 is associated with renal-related outcomes and explore its prospect as a novel prognosis biomarker.

METHODS

This was a single-center, prospective cohort study. A total of 133 AKI patients and 68 non-AKI patients admitted to ICU in Qilu Hospital Shandong University from January 2017 to January 2018. Urine samples were collected at enrollment and the relative expression of CD26 (CD26 percentage) in urinary exosomes was examined, that was then categorized into a low-CD26 level and a high-CD26 level.

RESULTS

CD26 percentage was significantly lower in the AKI cohort than in the control cohort. Within the AKI cohort, a high-CD26 level was associated with lower incidence of major adverse kidney events within 90 days, but higher incidence of reversal within 28 days. In AKI survivors, a high-CD26 level had a 4.67-, 3.50- and 4.66-fold higher odds than a low-CD26 level for early reversal, recovery and reversal, respectively, after adjustment for clinical factors. Prediction performance was moderate for AKI survivors but improved for non-septic AKI survivors.

CONCLUSIONS

Urinary exosomal CD26 is associated with renal reversal and recovery from AKI and is thus a promising prognosis biomarker.

Mesenchymal stem cells and extracellular vesicles in therapy against kidney diseases

Kidney diseases pose a threat to human health due to their rising incidence and fatality rate. In preclinical and clinical studies, it has been acknowledged that mesenchymal stem cells (MSCs) are effective and safe when used to treat kidney diseases. MSCs play their role mainly by secreting trophic factors and delivering extracellular vesicles (EVs). The genetic materials and proteins contained in the MSC-derived EVs (MSC-EVs), as an important means of cellular communication, have become a research focus for targeted therapy of kidney diseases. At present, MSC-EVs have shown evident therapeutic effects on acute kidney injury (AKI), chronic kidney disease (CKD), diabetic nephropathy (DN), and atherosclerotic renovascular disease (ARVD); however, their roles in the transplanted kidney remain controversial. This review summarises the mechanisms by which MSC-EVs treat these diseases in animal models and proposes certain problems, expecting to facilitate corresponding future clinical practice.

Genetic Background and Kinetics Define Wound Bed Extracellular Vesicles in a Mouse Model of Cutaneous Injury

Extracellular vesicles (EVs) have an important role in mediating intercellular signaling in inflammation and affect the kinetics of wound healing, however, an understanding of the mechanisms regulating these responses remains limited. Therefore, we have focused on the use of cutaneous injury models in which to study the biology of EVs on the inflammatory phase of wound healing. For this, the foreign body response using sterile subcutaneous polyvinylalcohol (PVA) sponges is ideally suited for the parallel analysis of immune cells and EVs without the need for tissue dissociation, which would introduce additional variables. We have previously used this model to identify mediators of EV biogenesis, establishing that control of how EVs are made affects their payload and biological activity. These studies in normal mice led us to consider how conditions such as immunodeficiency and obsesity affect the profile of immune cells and EVs in this model using genetically defined mutant mice. Since EVs are intrinsically heterogenous in biological fluids, we have focused our studies on a novel technology, vesicle flow cytometry (vFC) to quantify changes in EVs in mouse models. Here, we show that myeloid-derived immune cells and EVs express proteins relevant in antigen presentation in PVA sponge implants that have distinct profiles in wildtype, immune-deficient (NOD scid) vs. diabetic (Leprdb) mice. Together, these results establish a foundation for the parallel analysis of both immune cells and EVs with technologies that begin to address the heterogeneity of intercellular communication in the wound bed.

Mesenchymal stromal cell-mediated immune regulation: A promising remedy in the therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a major threat to global public health, with increasing prevalence as well as high morbidity and mortality, to which immune dysfunction has been recognized as a crucial contributor. Mesenchymal stromal cells (MSCs), obtained from various sources and possessing potent immunomodulatory abilities, have displayed great therapeutic potential for T2DM. Interestingly, the immunomodulatory capabilities of MSCs are endowed and plastic. Among the multiple mechanisms involved in MSC-mediated immune regulation, the paracrine effects of MSCs have attracted much attention. Of note, extracellular vesicles (EVs), an important component of MSC secretome, have emerged as pivotal mediators of their immunoregulatory effects. Particularly, the necrobiology of MSCs, especially apoptosis, has recently been revealed to affect their immunomodulatory functions in vivo. In specific, a variety of preclinical studies have demonstrated the beneficial effects of MSCs on improving islet function and ameliorating insulin resistance. More importantly, clinical trials have further uncovered the therapeutic potential of MSCs for T2DM. In this review, we outline current knowledge regarding the plasticity and underlying mechanisms of MSC-mediated immune modulation, focusing on the paracrine effects. We also summarize the applications of MSC-based therapies for T2DM in both preclinical studies and clinical trials, with particular emphasis on the modulation of immune system.

Mesenchymal stem cells protect renal tubular cells via TSG-6 regulating macrophage function and phenotype switching

Tumor necrosis factor (TNF)-α-induced gene/protein (TSG)-6 regulates the immunomodulatory properties of mesenchymal stem cells (MSCs), but its ability to protect the ischemic kidney is unknown. In a swine model of renal artery stenosis (RAS) and metabolic syndrome (MetS), we assessed the contribution of TSG-6 produced by MSCs to their immunomodulatory properties. Pigs were studied after 16 wk of diet-induced MetS and unilateral RAS and were either untreated or treated 4 wk earlier with intrarenal autologous adipose tissue-derived MSCs (n = 6 each). Lean, MetS, and RAS sham animals served as controls. We studied renal function in vivo (using computed tomography) and kidney histopathology and macrophage phenotype ex vivo. In vitro, TSG-6 levels were also measured in conditioned media of human MSCs incubated with TNF-α and levels of the tubular injury marker lactate dehydrogenase in conditioned media after coculturing macrophages with injured human kidney 2 (HK-2) cells with or without TSG-6. The effects of TSG-6 on macrophage phenotype (M1/M2), adhesion, and migration were also determined. MetS + RAS showed increased M1 macrophages and renal vein TNF-α levels. After MSC delivery, renal vein TSG-6 increased and TNF-α decreased, the M1-to-M2 ratio decreased, renal function improved, and fibrosis was alleviated. In vitro, TNF-α increased TSG-6 secretion by human MSCs. TSG-6 decreased lactate dehydrogenase release from injured HK-2 cells, increased expression of macrophage M2 markers, and reduced M1 macrophage adhesion and migration. Therefore, TSG-6 released from MSCs may decrease renal tubular cell injury, which is associated with regulating macrophage function and phenotype. These observations suggest that TSG-6 is endowed with renoprotective properties.NEW & NOTEWORTHY Tumor necrosis factor-α-induced gene/protein (TSG)-6 regulates the immunomodulatory properties of MSCs, but its ability to protect the ischemic kidney is unknown. In pigs with renal artery stenosis, we show that MSC delivery increased renal vein TSG-6, decreased kidney inflammatory macrophages, and improved renal function. In vitro, TSG-6 decreased inflammatory macrophages and tubular cell injury. Therefore, TSG-6 released from MSCs may decrease renal tubular cell injury, which is associated with regulating macrophage function and phenotype.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Potential Therapeutic Strategy for Acute Kidney Injury

Acute kidney injury (AKI) is a common and potential life-threatening disease in patients admitted to hospital, affecting 10%-15% of all hospitalizations and around 50% of patients in the intensive care unit. Severe, recurrent, and uncontrolled AKI may progress to chronic kidney disease or end-stage renal disease. AKI thus requires more efficient, specific therapies, rather than just supportive therapy. Mesenchymal stem cells (MSCs) are considered to be promising cells for cellular therapy because of their ease of harvesting, low immunogenicity, and ability to expand in vitro. Recent research indicated that the main therapeutic effects of MSCs were mediated by MSC-derived extracellular vesicles (MSC-EVs). Furthermore, compared with MSCs, MSC-EVs have lower immunogenicity, easier storage, no tumorigenesis, and the potential to be artificially modified. We reviewed the therapeutic mechanism of MSCs and MSC-EVs in AKI, and considered recent research on how to improve the efficacy of MSC-EVs in AKI. We also summarized and analyzed the potential and limitations of EVs for the treatment of AKI to provide ideas for future clinical trials and the clinical application of MSC-EVs in AKI.

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.

Metabolic Syndrome Alters the Cargo of Mitochondria-Related microRNAs in Swine Mesenchymal Stem Cell-Derived Extracellular Vesicles, Impairing Their Capacity to Repair the Stenotic Kidney

Background

Coexisting metabolic syndrome (MetS) and renal artery stenosis (RAS) are linked to poor renal outcomes. Mesenchymal stem/stromal cell- (MSC-) derived extracellular vesicles (EVs) from lean animals show superior ability to repair the experimental MetS+RAS kidney compared to EVs from MetS pig MSCs. We hypothesized that MetS leads to selective packaging in porcine EVs of microRNAs capable of targeting mitochondrial genes, interfering with their capacity to repair the MetS+RAS kidney.

Methods

Five groups of pigs (n = 7 each) were studied after 16 weeks of diet-induced MetS and RAS (MetS+RAS) and MetS+RAS 4 weeks after a single intrarenal delivery of EVs harvested from allogeneic adipose tissue-derived MSCs isolated from Lean or MetS pigs, and Lean or MetS sham controls. Single-kidney blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector CT, whereas EV microRNA cargo, renal tubular mitochondrial structure and bioenergetics, and renal injury pathways were assessed ex vivo.

Results

microRNA sequencing revealed 19 dysregulated microRNAs capable of targeting several mitochondrial genes in MetS-EVs versus Lean-EVs. Lean- and MetS-EVs were detected in the stenotic kidney 4 weeks after administration. However, only MetS-EVs failed to improve renal mitochondrial density, structure, and function or attenuate oxidative stress, tubular injury, and fibrosis. Furthermore, Lean-EVs but not MetS-EVs restored RBF and GFR in MetS+RAS.

Conclusion

MetS alters the cargo of mitochondria-related microRNAs in swine MSC-derived EVs, which might impair their capacity to repair the poststenotic kidney in MetS+RAS. These observations may contribute to develop approaches to improve the efficacy of MSC-EVs for patients with MetS.

Extracellular Vesicle-Dependent Communication Between Mesenchymal Stromal Cells and Immune Effector Cells

Mesenchymal stem/stromal cells (MSCs) are multipotent cells residing in the stromal tissues of the body and capable of promoting tissue repair and attenuating inflammatory processes through their immunomodulatory properties. Preclinical and clinical observations revealed that not only direct intercellular communication mediates MSC properties; in fact, a pivotal role is also played by the release of soluble and bioactive factors, such as cytokines, growth factor and extracellular vesicles (EVs). EVs are membrane-coated vesicles containing a large variety of bioactive molecules, including lipids, proteins, and nucleic acids, such as RNA. EVs release their contents into target cells, thus influencing cell fate through the control of intracellular processes. In addition, MSC-derived EVs can mediate modulatory effects toward different effector cells belonging to both innate and adaptive immunity. In this review, we will discuss the literature data concerning MSC-derived EVs, including the current standardized methods for their isolation and characterization, the mechanisms supporting their immunoregulatory properties, and their potential clinical application as alternative to MSC-based therapy for inflammatory reactions, such as graft-versus-host disease (GvHD).

Mesenchymal stem cell-derived extracellular vesicles alter disease outcomes via endorsement of macrophage polarization

Mesenchymal stem cells (MSCs) are adult stromal cells that reside in virtually all postnatal tissues. Due to their regenerative and immunomodulatory capacities, MSCs have attracted growing attention during the past two decades. MSC-derived extracellular vesicles (MSC-EVs) are able to duplicate the effects of their parental cells by transferring functional proteins and genetic materials to recipient cells without cell-to-cell contact. MSC-EVs also target macrophages, which play an essential role in innate immunity, adaptive immunity, and homeostasis. Recent studies have demonstrated that MSC-EVs reduce M1 polarization and/or promote M2 polarization in a variety of settings. In this review, we discuss the mechanisms of macrophage polarization and roles of MSC-EV-induced macrophage polarization in the outcomes of cardiovascular, pulmonary, digestive, renal, and central nervous system diseases. In conclusion, MSC-EVs may become a viable alternative to MSCs for the treatment of diseases in which inflammation and immunity play a critical role.