Human umbilical cord mesenchymal stem cell-derived extracellular vesicles: A novel therapeutic paradigm

Mesenchymal stem cells (MSCs) have been revealed to hold great potential for the development of new treatment approaches for various diseases. However, the clinical use of these cells is limited due to their tumorigenic effects. The therapeutic benefits of MSCs are largely dependent on paracrine factors including extracellular vesicles (EVs). EVs are nano-sized bilayer membrane structures containing lipids, microRNAs and proteins which play key roles in cell-to-cell communications. Because of their lower immunogenicity, tumorigenicity, and easier management, EVs have emerged as a new promising alternative to whole-cell therapy. Therefore, this paper reviews current preclinical studies on the use of EVs derived from human umbilical cord MSCs (hucMSCs) as a therapeutic approach in treatment of several diseases including neurological, cardiovascular, liver, kidney, and bone diseases as well as the cutaneous wound, inflammatory bowel disease, cancers, infertility, and other disorders.     

Enhanced bioprocess control to advance the manufacture of mesenchymal stromal cell-derived extracellular vesicles in stirred-tank bioreactors

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) act as signaling mediators of cellular responses. However, despite representing a promising alternative to cell-based therapies, clinical translation of EVs is currently limited by their lack of scalability and standardized bioprocessing. Herein, we integrated scalable downstream processing protocols with standardized expansion of large numbers of viable cells in stirred-tank bioreactors to improve EV production. Higher EV yields were linked to EV isolation by tangential flow filtration followed by size exclusion chromatography, rendering 5 times higher number of EVs comparatively to density gradient ultracentrifugation protocols. Additionally, when compared to static culture, EV manufacture in bioreactors resulted in 2.2 higher yields. Highlighting the role of operating under optimal cell culture conditions to maximize the number of EVs secreted per cell, MSCs cultured at lower glucose concentration favored EV secretion. While offline measurements of metabolites concentration can be performed, in this work, Raman spectroscopy was also applied to continuously track glucose levels in stirred-tank bioreactors, contributing to streamline the selection of optimal EV collection timepoints. Importantly, MSC-derived EVs retained their quality attributes and were able to stimulate angiogenesis in vitro, therefore highlighting their promising therapeutic potential.     

Generation of mesenchymal stem-like cells for producing extracellular vesicles

Mesenchymal stem cells (MSCs) are multipotent progenitor cells with therapeutic potential against autoimmune diseases, inflammation, ischemia, and metabolic disorders. Contrary to the previous conceptions, recent studies have revealed that the tissue repair and immunomodulatory functions of MSCs are largely attributed to their secretome, rather than their potential to differentiate into desired cell types. The composition of MSC secretome encompasses cytokines and growth factors, in addition to the cell-derived structures known as extracellular vesicles (EVs). EVs are membrane-enclosed nanoparticles that are capable of delivering biomolecules, and it is now believed that MSC-derived EVs are the major players that induce biological changes in the target tissues. Based on these EVs’ characteristics, the potential of EVs derived from MSC (MSC-EV) in terms of tissue regeneration and immune modulation has grown during the last decade. However, the use of MSCs for producing sufficient amount of EVs has not been satisfactory due to limitations in the cell growth and large variations among the donor cell types. In this regard, pluripotent stem cells (PSCs)-derived MSC-like cells, which can be robustly induced and expanded in vitro, have emerged as more accessible cell source that can overcome current limitations of using MSCs for EV production. In this review, we have highlighted the methods of generating MSC-like cells from PSCs and their therapeutic outcome in preclinical studies. Finally, we have also discussed future requirements for making this cell-free therapy clinically feasible.     

Bone marrow mesenchymal stem cells reduce ureteral stricture formation in a rat model via the paracrine effect of extracellular vesicles

With no effective therapy to prevent or treat ureteral stricture (US), a multifactorial fibrotic disease after iatrogenic injury of the ureter, the need for new therapies is urgent. Mesenchymal stem cells (MSCs) have been widely studied for treating tissue defects and excessive fibrosis, and recent studies established that one of the main therapeutic vectors of MSCs is comprised in their secretome and represented by extracellular vesicles (EVs). Thus, we have determined to explore the specific role of MSCs‐derived EVs (MSC‐EVs) treatment in a pre‐clinical model of US. The results firstly showed that either a bolus dose of MSCs or a bolus dose of MSC‐EVs (administration via renal‐arterial) significantly ameliorated ureteral fibrosis and recuperated ureter morphological development in a US rat model. We confirmed our observations through MSCs or MSC‐EVs treatment alleviated hydronephrosis, less renal dysfunction and blunted transforming growth factor‐β1 induced fibration. Due to MSC‐EVs are the equivalent dose of MSCs, and similar curative effects of transplantation of MSCs and MSC‐EVs were observed, we speculated the curative effect of MSCs in treating US might on account of the release of EVs through paracrine mechanisms. Our study demonstrated an innovative strategy to counteract ureteral stricture formation in a rat model of US.     

Therapeutic application of extracellular vesicles for various kidney diseases: a brief review

Extracellular vesicles (EVs) released from different types of kidney cells under physiologic conditions contribute to homeostasis maintenance, immune-modulation, and cell-to-cell communications. EVs can also negatively affect the progression of renal diseases through their pro-inflammatory, pro-fibrotic, and tumori-genic potential. Inhibiting EVs by blocking their production, release, and uptake has been suggested as a potential therapeutic mechanism based on the significant implication of exosomes in various renal diseases. On the other hand, stem cell-derived EVs can ameliorate tissue injury and mediate tissue repair by ameliorating apoptosis, inflammation, and fibrosis while promoting angiogenesis and tubular cell proliferation. Recent advancement in biomedical engineering technique has made it feasible to modulate the composition of exosomes with diverse biologic functions, making EV one of the most popular drug delivery tools. The objective of this review was to provide updates of recent clinical and experimental findings on the therapeutic potential of EVs in renal diseases and discuss the clinical applicability of EVs in various renal diseases.     

Therapeutic application of extracellular vesicles in kidney disease: promises and challenges

Extracellular vesicles (EVs) are nanosized, membrane‐bound vesicles released from different cells. Recent studies have revealed that EVs may participate in renal tissue damage and regeneration through mediating inter‐nephron communication. Thus, the potential use of EVs as therapeutic vector has gained considerable interest. In this review, we will discuss the basic characteristics of EVs and its role in nephron cellular communication. Then, the application of EVs as therapeutic vector based on its natural content or as carriers of drug, in acute and chronic kidney injury, was discussed. Finally, perspectives and challenges of EVs in therapy of kidney disease were described.     

Mesenchymal stem cell-derived extracellular vesicles as a new therapeutic strategy for ocular diseases

Mesenchymal stem cells (MSCs) have attracted considerable attention for their activity in the treatment of refractory visual disorders. Since MSCs were found to possess the beneficial effects by secreting paracrine factors rather than direct differentiation, MSC-derived extracellular vesicles (EVs) were widely studied in various disease models. MSCs generate abundant EVs, which act as important mediators by exchanging protein and genetic information between MSCs and target cells. It has been confirmed that MSC-derived EVs possess unique anti-inflammatory, anti-apoptotic, tissue repairing, neuroprotective, and immunomodulatory properties, similar to their parent cells. Upon intravitreal injection, MSC-derived EVs rapidly diffuse through the retina to alleviate retinal injury or inflammation. Due to possible risks associated with MSC transplantation, such as vitreous opacity and pathological proliferation, EVs appear to be a better choice for intravitreal injection. Small size EVs can pass through biological barriers easily and their contents can be modified genetically for optimal therapeutic effect. Hence, currently, they are also explored for the possibility of serving as drug delivery vehicles. In the current review, we describe the characteristics of MSC-derived EVs briefly, comprehensively summarize their biological functions in ocular diseases, and discuss their potential applications in clinical settings.     

Mesenchymal stromal cell‐derived extracellular vesicles as cell‐free biologics for the ex vivo expansion of hematopoietic stem cells

Hematopoietic stem cell transplantation (HSCT) is the ultimate choice of treatment for patients with hematological diseases and cancer. The success of HSCT is critically dependent on the number and engraftment efficiency of the transplanted donor hematopoietic stem cells (HSCs). Various studies show that bone marrow‐derived mesenchymal stromal cells (MSCs) support hematopoiesis and also promote ex vivo expansion of HSCs. MSCs exert their therapeutic effect through paracrine activity, partially mediated through extracellular vesicles (EVs). Although the physiological function of EVs is not fully understood, inspiring findings indicate that MSC‐derived EVs can reiterate the hematopoiesis, supporting the ability of MSCs by transferring their cargo containing proteins, lipids, and nucleic acids to the HSCs. The activation state of the MSCs or the signaling mechanism that prevails in them also defines the composition of their EVs, thereby influencing the fate of HSCs. Modulating or preconditioning MSCs to achieve a specific composition of the EV cargo for the ex vivo expansion of HSCs is, therefore, a promising strategy that can overcome several challenges associated with the use of naïve/unprimed MSCs. This review aims to speculate upon the potential role of preconditioned/primed MSC‐derived EVs as “cell‐free biologics,” as a novel strategy for expanding HSCs in vitro.     

The role of extracellular vesicles in podocyte autophagy in kidney disease

Podocytes are the key cells involved in protein filtration in the glomerulus. Once proteins appear in the urine when podocytes fail, patients will end with renal failure due to the progression of glomerular damage if no proper treatment is applied. The injury and loss of podocytes can be attributed to diverse factors, such as genetic, immunologic, toxic, or metabolic disorders. Recently, autophagy has emerged as a key mechanism to eliminate the unwanted cytoplasmic materials and to prolong the lifespan of podocytes by alleviating cell damage and stress. Typically, the fundamental function of extracellular vesicles (EVs) is to mediate the intercellular communication. Recent studies have suggested that, EVs, especially exosomes, play a certain role in information transfer by communicating proteins, mRNAs, and microRNAs with recipient cells. Under physiological and pathological conditions, EVs assist in the bioinformation interchange between kidneys and other organs. It is suggested that EVs are related to the pathogenesis of acute kidney injury and chronic kidney disease, including glomerular disease, diabetic nephropathy, renal fibrosis and end-stage renal disease. However, the role of EVs in podocyte autophagy remains unclear so far. Here, this study integrated the existing information about the relevancy, diagnostic value and therapeutic potential of EVs in a variety of podocytes-related diseases. The accumulating evidence highlighted that autophagy played a critical role in the homeostasis of podocytes in glomerular disease.     

Proteomic Signature of Mesenchymal Stromal Cell‐Derived Small Extracellular Vesicles

Small extracellular vesicles (EVs) are 50–200 nm vesicles secreted by most cells. They are considered as mediators of intercellular communication, and EVs from specific cell types, in particular mesenchymal stem/stromal cells (MSCs), offer powerful therapeutic potential, and can provide a novel therapeutic strategy. They appear promising and safe (as EVs are non‐self‐replicating), and eventually MSC‐derived EVs (MSC‐EVs) may be developed to standardized, off‐the‐shelf allogeneic regenerative and immunomodulatory therapeutics. Promising pre‐clinical data have been achieved using MSCs from different sources as EV‐producing cells. Similarly, a variety EV isolation and characterization methods have been applied. Interestingly, MSC‐EVs obtained from different sources and prepared with different methods show in vitro and in vivo therapeutic effects, indicating that isolated EVs share a common potential. Here, well‐characterized and controlled, publicly available proteome profiles of MSC‐EVs are compared to identify a common MSC‐EV protein signature that might be coupled to the MSC‐EVs’ common therapeutic potential. This protein signature may be helpful in developing MSC‐EV quality control platforms required to confirm the identity and test for the purity of potential therapeutic MSC‐EVs.     

骨髓间充质干细胞对移植肾缺血再灌注损伤保护作用的实验研究

目的 观察骨髓间充质干细胞（MSCs）对移植肾缺血再灌注损伤（IRI）模型修复的保护作用,及其作用机制的思路。方法 （1）采用密度梯度离心法结合贴壁分离法分离培养纯化SD大鼠骨髓MSCs,观察其形态,流式细胞仪检测细胞表面标记,检测骨髓MSCs向成骨和成脂细胞分化的潜能;（2）成年雌性SD大鼠28只,随机分组：正常对照组（control group,n=6）,假手术对照组（sham-operated group,n=6）,移植肾IRI组（vehicle-treated I/R group,n=8）,经尾静脉输注间充质干细胞（MSCs）移植肾IRI组（MSCs-treated via tail vein I/R group,n=8）。检测肾功能指标血尿素氮（BUN）和肌酐（Cr）水平变化,评定肾小管的凋亡指数和增殖指数,测定肾组织起氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）活性及微量丙二醛（MDA）水平,以及对肾脏病理学变化进行观察。结果 （1）分离培养的骨髓MSCs纯度高、生物学特征稳定;（2）移植肾IRI组肾功能指标（BUN36.9±4.8,Scr279.9±22.6）、氧化应激指标明显升高,组织形态学出现肾间质水肿明显,肾小管上皮细胞空泡样变性,近曲小管管壁肿胀,管腔变小。而经尾静脉输注MSCs移植肾IRI组大鼠肾功能指标（BUN22.6±7.8,Scr223.6±26.7）和氧化应激指标得到明显改善（P〈0.05）,组织形态学肾小管上皮细胞细胞核固缩、碎裂和溶解等细胞坏死和变性征象明显减轻,肾小管上皮细胞增殖指数（PI）高于IRI组,肾小管上皮细胞凋亡指数（AI）低于IRI组,两组间差异有统计学意义（P〈0.05）。结论 骨髓MSCs输注能促进肾脏IRI损伤后肾脏细胞增殖,抑制肾脏细胞凋亡,降低血清Creatinine和BUN,在一定程度上促进IRI后肾功能的恢复,通过抑制氧自由基的生成减轻肾组织的损伤程度,改善肾功能。     

Irisin is induced in renal ischemia-reperfusion to protect against tubular cell injury via suppressing p53

Renal ischemia-reperfusion is a major cause of acute kidney injury, a disease currently without effective treatments. Irisin was initially identified as an important factor produced by muscles to mediate the health benefits of exercise, and recent work has further suggested its protective effect against lung and liver injury. However, the role of Irisin in kidney diseases, including renal ischemia-reperfusion injury (IRI), remains unknown. In the present study, we found that the Irisin precursor, fibronectin type III domain-containing protein 5 (Fndc5), was induced in renal tubules in a mouse model of renal IRI and in cultured mouse renal proximal tubular cells subjected ATP depletion injury. Functionally, silencing Fndc5 in cultured proximal tubular cells increased the sensitivity to ATP depletion-induced apoptosis, whereas both Fndc5 overexpression and supplementation of recombinant Irisin alleviated ATP depletion-induced apoptosis. In vivo, administration of recombinant Irisin dramatically attenuated kidney dysfunction, tissue damage, tubular cell apoptosis, and inflammation during renal IRI in mice. Mechanistically, Irisin suppressed the activation of p53 in renal IRI, a critical factor in tubular cell death. Together, these results indicate that Irisin is induced in renal IRI as a protective mechanism for renal tubular cells, suggesting the therapeutic potential of recombinant Irisin in renal IRI and related kidney diseases.     

Transforming growth factor-β1-overexpressing mesenchymal stromal cells induced local tolerance in rat renal ischemia/reperfusion injury

BackgroundRegulatory T cells (Tregs) suppress excessive immune responses and play a crucial protective role in acute kidney injury (AKI). The aim of this study was to examine the therapeutic potential of transforming growth factor (TGF)-β1-overexpressing mesenchymal stromal cells (MSCs) in inducing local generation of Tregs in the kidney after ischemia/reperfusion (I/R) injury.MethodsMSCs were transduced with a lentiviral vector expressing the TGF-β1 gene; TGF-β1-overexpressing MSCs (designated TGF-β1/MSCs) were then transfused into the I/R-injured kidney via the renal artery.ResultsMSCs genetically modified with TGF-β1 achieved overexpression of TGF-β1. Compared with green fluorescent protein (GFP)/MSCs, TGF-β1/MSCs markedly improved renal function after I/R injury and reduced epithelial apoptosis and subsequent inflammation. The enhanced immunosuppressive and therapeutic abilities of TGF-β1/MSCs were associated with increased generation of induced Tregs and improved intrarenal migration of the injected cells. Futhermore, the mechanism of TGF-β1/MSCs in attenuating renal I/R injury was not through a direct canonical TGF-β1/Smad pathway.ConclusionTGF-β1/MSCs can induce a local immunosuppressive effect in the I/R-injured kidney. The immunomodulatory activity of TGF-β1–modified MSCs appears to be a gateway to new therapeutic approaches to prevent renal I/R injury.     

Bone marrow–derived mesenchymal stem cells attenuate tubulointerstitial injury through multiple mechanisms in UUO model

Current evidence supports the use of bone marrow–derived mesenchymal stem cells (MSCs) for a diverse range of clinical applications, and many studies have shown that MSCs have renal-protective effects, but the mechanism is not well understood. Therefore, in this study, we aim to further identify whether MSCs can attenuate renal fibrosis by decreasing tubulointerstitial injury in a unilateral ureteral obstruction (UUO) model. In this study, we cultured MSCs and then transplanted them into a UUO model through the tail vein. Histology, cell proliferation, peritubular capillary (PTC) loss and myofibroblast markers were examined on days 3, 7 and 14 after surgery. We demonstrated that renal interstitial fibrosis in the MSC group was significantly attenuated compared with the UUO and DMEM groups. Moreover, MSC treatment inhibited the loss of PTCs and increased parenchymal cell proliferation. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by MSC infusion. Furthermore, MSCs attenuated tubulointerstitial infiltration of macrophages in UUO mice. Tubulointerstitial damage plays a very important role in the progression of chronic kidney disease (CKD). PTC loss, macrophage recruitment, and myofibroblast activation are directly correlated with the development of renal tubulointerstitial fibrosis. Our results suggest that MSC infusion in the UUO model is a promising therapeutic strategy for promoting kidney repair.     

Mesenchymal stem cell–derived extracellular vesicles: a new impetus of promoting angiogenesis in tissue regeneration

Over the past few decades, extracellular vesicles (EVs) have emerged as crucial mediators of intercellular communication. EVs encapsulate and convey information to surrounding cells or distant cells, where they mediate cellular biological responses. Among their multifaceted roles in the modulation of biological responses, the involvement of EVs in vascular development, growth and maturation has been widely documented and their potential therapeutic application in regenerative medicine or in the treatment of angiogenesis-related diseases is drawing increasing interest. In this review, we have summarized the details about the current knowledge on biogenesis of EVs and conventional isolation methods. Evidence supporting the use of EVs derived from mesenchymal stromal cells (MSCs) to enhance angiogenesis in the development of insufficient angiogenesis, such as chronic wounds, stroke and myocardial infarction, will also be discussed critically. Finally, the main challenges and prerequisites for their therapeutic applications will be evaluated.     

Fetal Kidney Cells Can Ameliorate Ischemic Acute Renal Failure in Rats through Their Anti-Inflammatory,Anti-Apoptotic and Anti-Oxidative Effects

Fetal kidney cells may contain multiple populations of kidney stem cells and thus appear to be a suitable cellular therapy for the treatment of acute renal failure (ARF) but their biological characteristics and therapeutic potential have not been adequately explored. We have culture expanded fetal kidney cells derived from rat fetal kidneys, characterized them and evaluated their therapeutic effect in an ischemia reperfusion (IR) induced rat model of ARF. The fetal kidney cells grew in culture as adherent spindle shaped/polygonal cells and expressed CD29, CD44, CD73, CD90, CD105, CD24 and CD133 markers. Administration of PKH26 labeled fetal kidney cells in ARF rats resulted in a significant decrease in the levels of blood urea nitrogen, creatinine, and neutrophil gelatinase-associated lipocalin and decreased tubular necrosis in the kidney tissues (p<0.05 for all). The injected fetal kidney cells were observed to engraft around injured tubular cells, and there was increased proliferation and decreased apoptosis of tubular cells in the kidneys (p<0.05 for both). In addition, the kidney tissues of ARF rats treated with fetal kidney cells had a higher gene expression of renotropic growth factors (VEGF-A, IGF-1, BMP-7 and bFGF) and anti-inflammatory cytokine (IL10); up regulation of anti-oxidative markers (HO-1 and NQO-1); and a lower Bax/Bcl2 ratio as compared to saline treated rats (p<0.05 for all). Our data shows that culture expanded fetal kidney cells express mesenchymal and renal progenitor markers, and ameliorate ischemic ARF predominantly by their anti-apoptotic, anti-inflammatory and anti-oxidative effects.     

Infusion of mesenchymal stem cells overexpressing GDNF ameliorates renal function in nephrotoxic serum nephritis

Nephrotoxic serum nephritis (NSN) is a well-established animal model of glomerulonephritis, a frequent clinical condition with a high mortality rate owing to the ineffectiveness of current therapies. Mesenchymal stem cells (MSCs) are adult stem cells with potential as novel therapies in regenerative medicine owing to the absence of allogenic rejection. Glial cell-derived neurotrophic factor (GDNF) acts as a morphogen in kidney development. The therapeutic effectiveness of bone marrow MSCs overexpressing GDNF (GDNF-MSCs) was evaluated in an NSN rat model. An adenoviral vector was used to transduce MSCs with GDNF and a green fluorescent protein reporter gene. Then, GDNF-MSCs were injected into NSN rats via the renal artery. The influence of GDNF on renal injury was assessed. The location of GDNF-MSCs in kidneys was detected using fluorescence microscopy, cells were counted, and kidney function was measured. Infusion of GNDF-MSCs enhanced the recovery of renal function in NSN rats. MSCs were detected in the kidney cortex after injection. Compared with control MSCs, GDNF-MSCs led to significantly better renal function and injury recovery in NSN rats. GDNF has a positive effect on MSC differentiation in renal tissue. Owing to their highly renoprotective capacity, GDNF-MSCs represent a possible novel cell-based paradigm for treatment of glomerulonephritis.     

Potential advantages of acute kidney injury management by mesenchymal stem cells

Mesenchymal stem cells are currently considered as a promising tool for therapeutic application in acute kidney injury (AKI) management. AKI is characterized by acute tubular injury with rapid loss of renal function. After AKI, inflammation, oxidative stress and excessive deposition of extracellular matrix are the molecular events that ultimately cause the end-stage renal disease. Despite numerous improvement of supportive therapy, the mortality and morbidity among patients remain high. Therefore, exploring novel therapeutic options to treat AKI is mandatory. Numerous evidence in animal models has demonstrated the capability of mesenchymal stem cells (MSCs) to restore kidney function after induced kidney injury. After infusion, MSCs engraft in the injured tissue and release soluble factors and microvesicles that promote cell survival and tissue repairing. Indeed, the main mechanism of action of MSCs in tissue regeneration is the paracrine/endocrine secretion of bioactive molecules. MSCs can be isolated from several tissues, including bone marrow, adipose tissue, and blood cord; pre-treatment procedures to improve MSCs homing and their paracrine function have been also described. This review will focus on the application of cell therapy in AKI and it will summarize preclinical studies in animal models and clinical trials currently ongoing about the use of mesenchymal stem cells after AKI.     

Manufacture of extracellular vesicles derived from mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are a promising therapy for various diseases ranging from ischemic stroke to wound healing and cancer. Their therapeutic effects are mainly mediated by secretome-derived paracrine factors, with extracellular vesicles (EVs) proven to play a key role. This has led to promising research on the potential of MSC-EVs as regenerative, off-the-shelf therapeutic agents. However, the translation of MSC-EVs into the clinic is hampered by the poor scalability of their production. Recently, new advanced methods have been developed to upscale MSC cultivation and EV production yields, ranging from new cell culture devices to priming procedures. This review gives an overview of these innovative strategies for manufacturing MSC-EVs.     

Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have attracted great interest in the field of regenerative medicine. They can home to damaged tissue, where they can exert pro-regenerative and anti-inflammatory properties. These therapeutic effects involve the secretion of growth factors, cytokines, and chemokines. Moreover, the functions of MSCs could be mediated by extracellular vesicles (EVs) that shuttle various signaling messengers. Although preclinical studies and clinical trials have demonstrated promising therapeutic results, the efficiency and the safety of MSCs need to be improved. After transplantation, MSCs face harsh environmental conditions, which likely dampen their therapeutic efficacy. A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed. The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment. In this review, we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs. As stated above, EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation. As a result, this novel type of cell-free therapy may be safer and more efficient than the whole cell product. We will, therefore, also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs.