Immunoregulatory Effects of Mesenchymal Stem Cell-Derived Extracellular Vesicles on T Lymphocytes

Characterization of Exosome-Related Gene Risk Model to Evaluate the Tumor Immune Microenvironment and Predict Prognosis in Triple-Negative Breast Cancer

Background

As a kind of small membrane vesicles, exosomes are secreted by most cell types from multivesicular endosomes, including tumor cells. The relationship between exosomes and immune response plays a vital role in the occurrence and development of tumors. Nevertheless, the interaction between exosomes and the microenvironment of tumors remains unclear. Therefore, we set out to study the influence of exosomes on the triple-negative breast cancer (TNBC) microenvironment.

Method

One hundred twenty-one exosome-related genes were downloaded from ExoBCD database, and IVL, CXCL13, and AP2S1 were final selected because of the association with TNBC prognosis. Based on the sum of the expression levels of these three genes, provided by The Cancer Genome Atlas (TCGA), and the regression coefficients, an exosome risk score model was established. With the median risk score value, the patients in the two databases were divided into high- and low-risk groups. R clusterProfiler package was employed to compare the different enrichment ways between the two groups. The ESTIMATE and CIBERSORT methods were employed to analyze ESTIMATE Score and immune cell infiltration. Finally, the correlation between the immune checkpoint-related gene expression levels and exosome-related risk was analyzed. The relationship between selected gene expression and drug sensitivity was also detected.

Results

Different risk groups exhibited distinct result of TNBC prognosis, with a higher survival rate in the low-risk group than in the high-risk group. The two groups were enriched by immune response and biological process pathways. A better overall survival (OS) was demonstrated in patients with high scores of immune and ESTIMATE rather than ones with low scores. Subsequently, we found that CD4⁺-activated memory T cells and M1 macrophages were both upregulated in the low-risk group, whereas M2 macrophages and activated mast cell were downregulated in the low-risk group in patients from the TCGA and GEO databases, respectively. Eventually, four genes previously proposed to be targets of immune checkpoint inhibitors were evaluated, resulting in the expression levels of CD274, CTLA4, LAG3, and TIM3 being higher in the low-risk group than high-risk group.

Conclusion

The results of our study suggest that exosome-related risk model was related to the prognosis and ratio of immune cell infiltration in patients with TNBC. This discovery may make contributions to improve immunotherapy for TNBC.

Immunomodulatory Effect of MSCs and MSCs-Derived Extracellular Vesicles in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a common autoimmune connective tissue disease with unclear etiology and pathogenesis. Mesenchymal stem cell (MSC) and MSC derived extracellular vesicles (EVs) play important roles in regulating innate and adaptive immunity, which are involved in many physiological and pathological processes and contribute to the immune homeostasis in SLE. The effects of MSCs and EVs on SLE have been drawing more and more attention during the past few years. This article reviews the immunomodulatory effects and underlying mechanisms of MSC/MSC-EVs in SLE, which provides novel insight into understanding SLE pathogenesis and guiding the biological therapy.

Stimulation of Treg Cells to Inhibit Osteoclastogenesis in Gorham-Stout Disease

Gorham-Stout disease (GSD) is a very rare syndrome displaying excessive bone erosion and vascular lesion. Due to the rarity of the disease and to the limited studies, its etiopathogenesis is not entirely known. The involvement of immune system in the progressive osteolysis was recently suggested. Indeed, extensive reciprocal interactions between the immune and skeletal systems have been demonstrated. This study aimed to evaluate alterations of immune cells in GSD. An increase of CD8+ cells and reduction of CD4+ and CD4+CD25+CD127^low cells was revealed in patients. Interestingly, patients’ regulatory T cells maintain the ability to respond to extracellular stimuli and to regulate osteoclastogenesis; GSD cells proliferate under aCD3/CD28 signal reaching similar levels to those observed in control culture and exert their immunomodulatory activity on effector T cells. GSD Treg cells preserved their inhibitory effects on the osteoclastogenesis. These results suggest that stimulation of Treg cells could open the way for the identification and testing of new therapeutic approaches for patients affected by GSD.

Immunomodulatory Properties of Umbilical Cord Blood-Derived Small Extracellular Vesicles and Their Therapeutic Potential for Inflammatory Skin Disorders

Umbilical cord blood (UCB) has long been seen as a rich source of naïve cells with strong regenerative potential, likely mediated by paracrine signals. More recently, small extracellular vesicles (sEV), such as exosomes, have been shown to play essential roles in cell-to-cell communication, via the transport of numerous molecules, including small RNAs. Often explored for their potential as biomarkers, sEV are now known to have regenerative and immunomodulating characteristics, particularly if isolated from stem cell-rich tissues. In this study, we aim to characterize the immunomodulating properties of umbilical cord blood mononuclear cell-derived sEV (UCB-MNC-sEV) and explore their therapeutic potential for inflammatory skin diseases. UCB-MNC-sEV were shown to shift macrophages toward an anti-inflammatory phenotype, which in turn exert paracrine effects on fibroblasts, despite previous inflammatory stimuli. Additionally, the incubation of PBMC with UCB-MNC-sEV resulted in a reduction of total CD4+ and CD8+ T-cell proliferation and cytokine release, while specifically supporting the development of regulatory T-cells (Treg), by influencing FOXP3 expression. In a 3D model of psoriatic skin, UCB-MNC-sEV reduced the expression of inflammatory and psoriatic markers IL6, IL8, CXCL10, COX2, S100A7, and DEFB4. In vivo, UCB-MNC-sEV significantly prevented or reversed acanthosis in imiquimod-induced psoriasis, and tendentially increased the number of Treg in skin, without having an overall impact on disease burden. This work provides evidence for the anti-inflammatory and tolerogenic effect of UCB-MNC-sEV, which may be harnessed for the treatment of Th17-driven inflammatory skin diseases, such as psoriasis.

The Therapeutic Potential of Mesenchymal Stromal Cells for Regenerative Medicine: Current Knowledge and Future Understandings

In recent decades, research on the therapeutic potential of progenitor cells has advanced considerably. Among progenitor cells, mesenchymal stromal cells (MSCs) have attracted significant interest and have proven to be a promising tool for regenerative medicine. MSCs are isolated from various anatomical sites, including bone marrow, adipose tissue, and umbilical cord. Advances in separation, culture, and expansion techniques for MSCs have enabled their large-scale therapeutic application. This progress accompanied by the rapid improvement of transplantation practices has enhanced the utilization of MSCs in regenerative medicine. During tissue healing, MSCs may exhibit several therapeutic functions to support the repair and regeneration of injured tissue. The process underlying these effects likely involves the migration and homing of MSCs, as well as their immunotropic functions. The direct differentiation of MSCs as a cell replacement therapeutic mechanism is discussed. The fate and behavior of MSCs are further regulated by their microenvironment, which may consequently influence their repair potential. A paracrine pathway based on the release of different messengers, including regulatory factors, chemokines, cytokines, growth factors, and nucleic acids that can be secreted or packaged into extracellular vesicles, is also implicated in the therapeutic properties of MSCs. In this review, we will discuss relevant outcomes regarding the properties and roles of MSCs during tissue repair and regeneration. We will critically examine the influence of the local microenvironment, especially immunological and inflammatory signals, as well as the mechanisms underlying these therapeutic effects. Importantly, we will describe the interactions of local progenitor and immune cells with MSCs and their modulation during tissue injury. We will also highlight the crucial role of paracrine pathways, including the role of extracellular vesicles, in this healing process. Moreover, we will discuss the therapeutic potential of MSCs and MSC-derived extracellular vesicles in the treatment of COVID-19 (coronavirus disease 2019) patients. Overall, this review will provide a better understanding of MSC-based therapies as a novel immunoregenerative strategy.

Immunomodulation effect of mesenchymal stem cells in islet transplantation

Mesenchymal stem cells (MSCs) therapy has brought a great enthusiasm to the treatment of various immune disorders, tissue regeneration and transplantation therapy. MSCs are being extensively investigated for their immunomodulatory actions. MSCs can deliver immunomodulatory signals to inhibit allogeneic T cell immune responses by downregulating pro-inflammatory cytokines and increasing regulatory cytokines and growth factors. Islet transplantation is a therapeutic alternative to the insulin therapy for the treatment of type 1 diabetes mellitus (T1DM). However, the acute loss of islets due to the lack of vasculature and hypoxic milieu in the immediate post-transplantation period may lead to treatment failure. Moreover, despite the use of potent immunosuppressive drugs, graft failure persists because of immunological rejection. Many in vitro and in vivo researches have demonstrated the multipotency of MSCs as a mediator of immunomodulation and a great approach for enhancement of islet engraftment. MSCs can interact with immune cells of the innate and adaptive immune systems via direct cell-cell contact or through secretomes containing numerous soluble growth and immunomodulatory factors or mitochondrial transfer. This review highlights the interactions between MSCs and different immune cells to mediate immunomodulatory functions along with the importance of MSCs therapy for the successful islet transplantation.

The Potential Role of Extracellular Vesicles in COVID-19 Treatment: Opportunity and Challenge

SARS-CoV-2 infection has become an urgent public health concern worldwide, severely affecting our society and economy due to the long incubation time and high prevalence. People spare no effort on the rapid development of vaccine and treatment all over the world. Amongst the numerous ways of tackling this pandemic, some approaches using extracellular vesicles (EVs) are emerging. In this review, we summarize current prevalence and pathogenesis of COVID-19, involving the combination of SARS-CoV-2 and virus receptor ACE2, endothelial dysfunction and micro thrombosis, together with cytokine storm. We also discuss the ongoing EVs-based strategies for the treatment of COVID-19, including mesenchymal stem cell (MSC)-EVs, drug-EVs, vaccine-EVs, platelet-EVs, and others. This manuscript provides the foundation for the development of targeted drugs and vaccines for SARS-CoV-2 infections.

Therapeutic Role of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Female Reproductive Diseases

Reproductive disorders, including intrauterine adhesion (IUA), premature ovarian insufficiency (POI), and polycystic ovary syndrome (PCOS), are great threats to female reproduction. Recently, mesenchymal stem cells derived-extracellular vesicles (MSC-EVs) have presented their potentials to cure these diseases, not only for the propensity ability they stemmed from the parent cells, but also for the higher biology stability and lower immunogenicity, compared to MSCs. EVs are lipid bilayer complexes, functional as mediators by transferring multiple molecules to recipient cells, such as proteins, microRNAs, lipids, and cytokines. EVs appeared to have a therapeutic effect on the female reproductive disorder, such as repairing injured endometrium, suppressing fibrosis of endometrium, regulating immunity and anti-inflammatory, and repressing apoptosis of granulosa cells (GCs) in ovaries. Although the underlying mechanisms of MSC-EVs have reached a consensus, several theories have been proposed, including promoting angiogenesis, regulating immunity, and reducing oxidate stress levels. In the current study, we summarized the current knowledge of functions of MSC-EVs on IUA, POI, and PCOS. Given the great potentials of MSC-EVs on reproductive health, the critical issues discussed will guide new insights in this rapidly expanding field.

Human umbilical cord mesenchymal stem cell-derived extracellular vesicles attenuate experimental autoimmune encephalomyelitis via regulating pro and anti-inflammatory cytokines

The therapeutic effects of mesenchymal stem cells-extracellular vesicles have been proved in many inflammatory animal models. In the current study, we aimed to investigate the effect of extracellular vesicles (EVs) derived from human umbilical cord-MSC (hUCSC-EV) on the clinical score and inflammatory/anti-inflammatory cytokines on the EAE mouse model. After induction of EAE in C57Bl/6 mice, they were treated intravenously with hUCSC-EV or vehicle. The clinical score and body weight of all mice was registered every day. On day 30, mice were sacrificed and splenocytes were isolated for cytokine assay by ELISA. Cytokine expression of pro-/anti-inflammatory cytokine by real-time PCR, leukocyte infiltration by hematoxylin and eosin (H&E) staining, and the percent of glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) positive cells by immunohistochemistry were assessed in the spinal cord. Our results showed that hUCSC-EV-treated mice have lower maximum mean clinical score (MMCS), pro-inflammatory cytokines, and inflammatory score in comparison to the control mice. We also showed that hUCSC-EV administration significantly improved body weight and increased the anti-inflammatory cytokines and the frequency of Treg cells in the spleen. There was no significant difference in the percent of GFAP and MBP positive cells in the spinal cord of experimental groups. Finally, we suggest that intravenous administration of hUCSC-EV alleviate induce-EAE by reducing the pro-inflammatory cytokines, such as IL-17a, TNF-α, and IFN-γ, and increasing the anti-inflammatory cytokines, IL-4 and IL-10, and also decrease the leukocyte infiltration in a model of MS. It seems that EVs from hUC-MSCs have the same therapeutic effects similar to EVs from other sources of MSCs, such as adipose or bone marrow MSCs.

Potential of Mesenchymal Stem Cells in the Rejuvenation of the Aging Immune System

Rapid growth of the geriatric population has been made possible with advancements in pharmaceutical and health sciences. Hence, age-associated diseases are becoming more common. Aging encompasses deterioration of the immune system, known as immunosenescence. Dysregulation of the immune cell production, differentiation, and functioning lead to a chronic subclinical inflammatory state termed inflammaging. The hallmarks of the aging immune system are decreased naïve cells, increased memory cells, and increased serum levels of pro-inflammatory cytokines. Mesenchymal stem cell (MSC) transplantation is a promising solution to halt immunosenescence as the cells have excellent immunomodulatory functions and low immunogenicity. This review compiles the present knowledge of the causes and changes of the aging immune system and the potential of MSC transplantation as a regenerative therapy for immunosenescence.

Mesenchymal stromal cell mitochondrial transfer to human induced T-regulatory cells mediates FOXP3 stability

The key obstacle to clinical application of human inducible regulatory T cells (iTreg) as an adoptive cell therapy in autoimmune disorders is loss of FOXP3 expression in an inflammatory milieu. Here we report human iTreg co-cultured with bone marrow-derived mesenchymal stromal cells (MSCs) during short-term ex vivo expansion enhances the stability of iTreg FOXP3 expression and suppressive function in vitro and in vivo, and further that a key mechanism of action is MSC mitochondrial (mt) transfer via tunneling nanotubules (TNT). MSC mt transfer is driven by mitochondrial metabolic function (CD39/CD73 signaling) in proliferating iTreg and promotes iTreg expression of FOXP3 stabilizing factors BACH2 and SENP3. These results elucidate cellular and molecular mechanisms underlying human MSC mt transfer to proliferating cells. MSC mt transfer stabilizes FOXP3 expression in iTregs, thereby enhancing and sustaining their suppressive function in inflammatory conditions in vitro and in vivo.

Investigating the effects of IDO1, PTGS2, and TGF-β1 overexpression on immunomodulatory properties of hTERT-MSCs and their extracellular vesicles

The therapeutic potential of mesenchymal stem cells (MSCs) is out of the question. Yet, recent drawbacks have resulted in a strategic shift towards the application of MSC-derived cell-free products such as extracellular vesicles (EVs). Recent reports revealed that functional properties of MSCs, including EV secretion patterns, correlate with microenvironmental cues. These findings highlight the urgent need for defining the optimal circumstances for EV preparation. Considering the limitations of primary cells, we employed immortalized cells as an alternative source to prepare therapeutically sufficient EV numbers. Herein, the effects of different conditional environments are explored on human TERT-immortalized MSCs (hTERT-MSCs). The latter were transduced to overexpress IDO1, PTGS2, and TGF-β1 transgenes either alone or in combination, and their immunomodulatory properties were analyzed thereafter. Likewise, EVs derived from these various MSCs were extensively characterized. hTERT-MSCs-IDO1 exerted superior inhibitory effects on lymphocytes, significantly more than hTERT-MSCs-IFN-γ. As such, IDO1 overexpression promoted the immunomodulatory properties of such enriched EVs. Considering the limitations of cell therapy like tumor formation and possible immune responses in the host, the results presented herein might be considered as a feasible model for the induction of immunomodulation in off-the-shelf and cell-free therapeutics, especially for autoimmune diseases.

miR-155 Contributes to the Immunoregulatory Function of Human Mesenchymal Stem Cells

Objectives

Mesenchymal stem/stromal cells (MSCs) are widely investigated in regenerative medicine thanks to their immunomodulatory properties. They exert their anti-inflammatory function thanks to the secretion of a number of mediators, including proteins and miRNAs, which can be released in the extracellular environment or in the cargo of extracellular vesicles (EVs). However, the role of miRNAs in the suppressive function of MSCs is controversial. The aim of the study was to identify miRNAs that contribute to the immunomodulatory function of human bone marrow-derived MSCs (BM-MSCs).

Methods

Human BM-MSCs were primed by coculture with activated peripheral blood mononuclear cells (aPBMCs). High throughput miRNA transcriptomic analysis was performed using Human MicroRNA TaqMan® Array Cards. The immunosuppressive function of miRNAs was investigated in mixed lymphocyte reactions and the delayed type hypersensitivity (DTH) murine model.

Results

Upon priming, 21 out of 377 tested miRNAs were significantly modulated in primed MSCs. We validated the up-regulation of miR-29a, miR-146a, miR-155 and the down-regulation of miR-149, miR-221 and miR-361 in additional samples of primed MSCs. We showed that miR-155 significantly reduced the proliferation of aPBMCs in vitro and inflammation in vivo, using the DTH model. Analysis of miRNA-mRNA interactions revealed miR-221 as a potential target gene that is down-regulated by miR-155 both in primed MSCs and in aPBMCs.

Conclusion

Here, we present evidence that miR-155 participates to the immunosuppressive function of human BM-MSCs and down-regulates the expression of miR-221 as a possible inflammatory mediator.

Anti-Inflammatory Effects of Plasma Circulating Exosomes Obtained from Normal-Weight and Obese Subjects on Hepatocytes

INTRODUCTION

Obesity is a disorder with low-grade chronic inflammation that plays a key role in hepatic inflammation and steatosis. Moreover, there are studies to support the role of exosomes in cellular communications, the regulation of metabolic homeostasis and immunomodulatory activity. Accordingly, we aimed to evaluate the influence of plasma circulating exosomes derived from females with normal-weight and obesity on the secretion of inflammatory cytokines in human liver cells.

METHODS

Plasma circulating exosomes were isolated from four normal (N-Exo) and four obese (OExo) women. The exosomes were characterized and approved for CD63 expression (common exosomal protein marker) and morphology/size using the western blot and TEM methods, respectively. The exosomes were used for the stimulation of HepG2 cells in vitro. After 24 h of incubation, the protein levels of TNF-α, IL-6, and IL-1β were measured in the culture supernatant of HepG2 cells using the ELISA kit.

RESULTS

The protein levels of IL-6 and TNF-α in the cells treated with O-Exo and N-Exo reduced significantly in comparison with the control group (P=0.039 and P<0.001 respectively), while significant differences were not found between normal and obese groups (P=0.808, and P=0.978 respectively). However, no significant differences were found among the three groups in terms of IL-1β levels (P=0.069). Based on the correlation analysis, the protein levels of IL-6 were positively correlated with TNF-α (r 0.978, P<0.001).

CONCLUSION

These findings suggest that plasma circulating exosomes have probably antiinflammatory properties independent of body mass index and may decrease the secretion of inflammatory cytokines in the liver. However, further in vitro and in vivo investigations are needed to address the anti-inflammatory function of N-Exo and O-Exo in human liver cells and/or other cells.

The Current Status of Mesenchymal Stromal Cells: Controversies, Unresolved Issues and Some Promising Solutions to Improve Their Therapeutic Efficacy

Mesenchymal stromal cells (MSCs) currently constitute the most frequently used cell type in advanced therapies with different purposes, most of which are related with inflammatory processes. Although the therapeutic efficacy of these cells has been clearly demonstrated in different disease animal models and in numerous human phase I/II clinical trials, only very few phase III trials using MSCs have demonstrated the expected potential therapeutic benefit. On the other hand, diverse controversial issues on the biology and clinical applications of MSCs, including their specific phenotype, the requirement of an inflammatory environment to induce immunosuppression, the relevance of the cell dose and their administration schedule, the cell delivery route (intravascular/systemic vs. local cell delivery), and the selected cell product (i.e., use of autologous vs. allogeneic MSCs, freshly cultured vs. frozen and thawed MSCs, MSCs vs. MSC-derived extracellular vesicles, etc.) persist. In the current review article, we have addressed these issues with special emphasis in the new approaches to improve the properties and functional capabilities of MSCs after distinct cell bioengineering strategies.

Expedition into Exosome Biology: A Perspective of Progress from Discovery to Therapeutic Development

Exosomes are membrane-enclosed distinct cellular entities of endocytic origin that shuttle proteins and RNA molecules intercellularly for communication purposes. Their surface is embossed by a huge variety of proteins, some of which are used as diagnostic markers. Exosomes are being explored for potential drug delivery, although their therapeutic utilities are impeded by gaps in knowledge regarding their formation and function under physiological condition and by lack of methods capable of shedding light on intraluminal vesicle release at the target site. Nonetheless, exosomes offer a promising means of developing systems that enable the specific delivery of therapeutics in diseases like cancer. This review summarizes information on donor cell types, cargoes, cargo loading, routes of administration, and the engineering of exosomal surfaces for specific peptides that increase target specificity and as such, therapeutic delivery.

Cell-derived vesicles for delivery of cancer immunotherapy

In recent years, cancer immunotherapy has received unprecedented attention due to the clinical achievements. The applications of biomedical engineering and materials science to cancer immunotherapy have solved the challenges caused by immunotherapy to a certain extent. Among them, cell-derived vesicles are natural biomaterials chosen as carriers or immune-engineering in view of their many unique advantages. This review will briefly introduce the recent applications of cell-derived vesicles for cancer immunotherapy.

Cell-derived vesicles for delivery of cancer immunotherapy

In recent years, cancer immunotherapy has received unprecedented attention due to the clinical achievements. The applications of biomedical engineering and materials science to cancer immunotherapy have solved the challenges caused by immunotherapy to a certain extent. Among them, cell-derived vesicles are natural biomaterials chosen as carriers or immune-engineering in view of their many unique advantages. This review will briefly introduce the recent applications of cell-derived vesicles for cancer immunotherapy.

Cellular therapies for graft-versus-host disease: a tale of tissue repair and tolerance

The success of allogeneic hematopoietic cell transplantation depends heavily on the delicate balance between the activity of the donor immune system against malignant and nonmalignant cells of the recipient. Abrogation of alloreactivity will lead to disease relapse, whereas untamed allo-immune responses will lead to lethal graft-versus-host disease (GVHD). A number of cell types have been identified that can be used to suppress alloreactive immune cells and prevent lethal GVHD in mice. Of those, mesenchymal stromal cells and, to a lesser extent, regulatory T cells have demonstrated efficacy in humans. Ideally, cellular therapy for GVHD will not affect alloreactive immune responses against tumor cells. The importance of tissue damage in the pathophysiology of GVHD rationalizes the development of cells that support tissue homeostasis and repair, such as innate lymphoid cells. We discuss recent developments in the field of cellular therapy to prevent and treat acute and chronic GVHD, in the context of GVHD pathophysiology.

Cytochalasin B-Induced Membrane Vesicles from Human Mesenchymal Stem Cells Overexpressing IL2 Are Able to Stimulate CD8+ T-Killers to Kill Human Triple Negative Breast Cancer Cells

Simple Summary

Almost all human cells release extracellular vesicles participating in intercellular communication. Extracellular vesicles are rounded structures surrounded by the cytoplasmic membrane, which embody cytoplasmic contents of the parental cells, which makes extracellular vesicles a promising therapeutic tool for cell-free cancer therapy. In this study, human mesenchymal stem cells were genetically modified to overexpress human interleukin-2 (IL2), a cytokine which regulates the proliferation and activation of immune cells. Membrane vesicle release from native and genetically modified stem cells was induced by cytochalasin B treatment to increase the yield of membrane vesicles. To evaluate the immunomodulating properties of isolated membrane vesicles, immune cells were isolated from human peripheral blood and co-cultured with membrane vesicles from native or IL2 overexpressing stem cells. To analyze the anti-tumor activity of immune cells after interaction with IL2-enriched membrane vesicles, immune cells were co-cultured with triple negative breast cancer cells. As a result, IL2-enriched membrane vesicles were able to activate and stimulate the proliferation of immune cells, which in turn were able to induce apoptosis in breast cancer cells. Therefore, the production of IL2-enriched membrane vesicles represents a unique opportunity to meet the potential of extracellular vesicles to be used in clinical applications for cancer therapy.

Abstract

Interleukin 2 (IL2) was one of the first cytokines used for cancer treatment due to its ability to stimulate anti-cancer immunity. However, recombinant IL2-based therapy is associated with high systemic toxicity and activation of regulatory T-cells, which are associated with the pro-tumor immune response. One of the current trends for the delivery of anticancer agents is the use of extracellular vesicles (EVs), which can carry and transfer biologically active cargos into cells. The use of EVs can increase the efficacy of IL2-based anti-tumor therapy whilst reducing systemic toxicity. In this study, human adipose tissue-derived mesenchymal stem cells (hADSCs) were transduced with lentivirus encoding IL2 (hADSCs-IL2). Membrane vesicles were isolated from hADSCs-IL2 using cytochalasin B (CIMVs-IL2). The effect of hADSCs-IL2 and CIMVs-IL2 on the activation and proliferation of human peripheral blood mononuclear cells (PBMCs) as well as the cytotoxicity of activated PBMCs against human triple negative cancer MDA-MB-231 and MDA-MB-436 cells were evaluated. The effect of CIMVs-IL2 on murine PBMCs was also evaluated in vivo. CIMVs-IL2 failed to suppress the proliferation of human PBMCs as opposed to hADSCs-IL2. However, CIMVs-IL2 were able to activate human CD8⁺ T-killers, which in turn, killed MDA-MB-231 cells more effectively than hADSCs-IL2-activated CD8⁺ T-killers. This immunomodulating effect of CIMVs-IL2 appears specific to human CD8⁺ T-killer cells, as the same effect was not observed on murine CD8⁺ T-cells. In conclusion, the use of CIMVs-IL2 has the potential to provide a more effective anti-cancer therapy. This compelling evidence supports further studies to evaluate CIMVs-IL2 effectiveness, using cancer mouse models with a reconstituted human immune system.

Cellular therapies in organ transplantation

Cellular therapy is a promising tool for improving the outcome of organ transplantation. Various cell types with different immunoregulatory and regenerative properties may find application for specific transplant rejection or injury-related indications. The current era is crucial for the development of cellular therapies. Preclinical models have demonstrated the feasibility of efficacious cell therapy in transplantation, early clinical trials have shown safety of several of these therapies, and the first steps towards efficacy studies in humans have been made. In this review, we address the current state of the art of cellular therapies in clinical transplantation and discuss monitoring tools and endpoints for these studies.

Intratracheal administration of mesenchymal stem cell-derived extracellular vesicles reduces lung injuries in a chronic rat model of bronchopulmonary dysplasia

Early therapeutic effect of intratracheally (IT)-administered extracellular vesicles secreted by mesenchymal stem cells (MSC-EVs) has been demonstrated in a rat model of bronchopulmonary dysplasia (BPD) involving hyperoxia exposure in the first 2 postnatal weeks. The aim of this study was to evaluate the protective effects of IT-administered MSC-EVs in the long term. EVs were produced from MSCs following GMP standards. At birth, rats were distributed in three groups: (a) animals raised in ambient air for 6 weeks (n = 10); and animals exposed to 60% hyperoxia for 2 weeks and to room air for additional 4 weeks and treated with (b) IT-administered saline solution (n = 10), or (c) MSC-EVs (n = 10) on postnatal days 3, 7, 10, and 21. Hyperoxia exposure produced significant decreases in total number of alveoli, total surface area of alveolar air spaces, and proliferation index, together with increases in mean alveolar volume, mean linear intercept and fibrosis percentage; all these morphometric changes were prevented by MSC-EVs treatment. The medial thickness index for <100 µm vessels was higher for hyperoxia-exposed/sham-treated than for normoxia-exposed rats; MSC-EV treatment significantly reduced this index. There were no significant differences in interstitial/alveolar and perivascular F4/8-positive and CD86-positive macrophages. Conversely, hyperoxia exposure reduced CD163-positive macrophages both in interstitial/alveolar and perivascular populations and MSC-EV prevented these hyperoxia-induced reductions. These findings further support that IT-administered EVs could be an effective approach to prevent/treat BPD, ameliorating the impaired alveolarization and pulmonary artery remodeling also in a long-term model. M2 macrophage polarization could play a role through anti-inflammatory and proliferative mechanisms.

Characterization of Urine Stem Cell-Derived Extracellular Vesicles Reveals B Cell Stimulating Cargo

Elucidation of the biological functions of extracellular vesicles (EVs) and their potential roles in physiological and pathological processes is an expanding field of research. In this study, we characterized USC-derived EVs and studied their capacity to modulate the human immune response in vitro. We found that the USC-derived EVs are a heterogeneous population, ranging in size from that of micro-vesicles (150 nm-1 μm) down to that of exosomes (60-150 nm). Regarding their immunomodulatory functions, we found that upon isolation, the EVs (60-150 nm) induced B cell proliferation and IgM antibody secretion. Analysis of the EV contents unexpectedly revealed the presence of BAFF, APRIL, IL-6, and CD40L, all known to play a central role in B cell stimulation, differentiation, and humoral immunity. In regard to their effect on T cell functions, they resembled the function of mesenchymal stem cell (MSC)-derived EVs previously described, suppressing T cell response to activation. The finding that USC-derived EVs transport a potent bioactive cargo opens the door to a novel therapeutic avenue for boosting B cell responses in immunodeficiency or cancer.

How severe RNA virus infections such as SARS-CoV-2 disrupt tissue and organ barriers—Reconstitution by mesenchymal stem cell-derived exosomes

The host tissue barriers arrange numerous lines of resistance to influx and cell-to-cell spread of pathogenic viruses. However, the highly virulent pathogens are equipped with diverse molecular mechanisms that can subvert the host countermeasures and/or exaggerate the host cell responses to toxic levels leading to severe illnesses. In his review, we discuss the immune-mediated pathogenesis of COVID-19 disease induced by the SARS-Cov-2 coronavirus. SARS-Cov-2 primarily infects type II alveolar epithelial cells. These cells are highly abundant with the ACE2 receptor protein, which occurs to be counterpart of the viral Spike protein and thus facilitates internalization of the virus. Following infection onset, the rapid clinical deterioration occurs about in a week suggesting that the respiratory failure in COVID-19 could result from a unique pattern of immune impairment characterized by severe Cytokine Release Syndrome (known as cytokine storm) leading to macrophage activation syndrome. In addition, the SARS-Cov-2 infection can induce a profound depletion of CD4 lymphocytes, CD19 lymphocytes, and natural killer cells, i.e., all major guardians cell components of the host immune barrier. However, while the numbers of that cells decline in the sequelae of the disease, the presence of persistent hyper-inflammation driving progressive tissue injury, suggests that the deteriorating impact of the systemic reactive responses can be more significant than the virus-induced cytopathic effects on the immunocompetent cells. In this respect, the authors discuss the emerging evidence of beneficial effects of administration of exosomes derived from mesenchymal stem cells—another sentinel-type cells—in management of the hyper-inflammatory response to SARS-CoV-2. Moreover, they also discuss the exosomes-originated mechanisms, which sustain regeneration of the damaged pulmonary lining cells and the vascular endothelial cells in various organs, including the brain.

Umbilical cord mesenchymal stem cells as well as their released exosomes suppress proliferation of activated PBMCs in multiple sclerosis

Multiple sclerosis (MS) is a central nervous system (CNS) degenerative disorder which is caused by a targeted autoimmune-mediated attack on myelin proteins. Previously, mesenchymal stem cells were considered as a novel and successful treatment of MS. One of the underlying mechanisms behind their immunomodulatory function is the release of extracellular vesicles, particularly exosomes. In this study, we aimed to evaluate the suppressive efficacy of MSCs and their exosomes on the proliferation of peripheral mononuclear blood cells (PBMC) in relapsing-remitting MS (RRMS) patients and healthy subjects. To do, mesenchymal stem cells were derived from human umbilical cord tissues and used for exosome isolation through ultracentrifugation. Suppressive function of MSCs and MSC-derived exosomes was examined in a coculture with CFSE-labelled PBMCs in vitro. PBMC proliferation of the patients and healthy individuals was measured using flow cytometry. We first demonstrated that proliferation of PBMCs decreased in the presence of MSCs and suppression was more efficient by MSC-derived exosomes, with a minimum alloreaction rate. However, suppression capacity of MSCs and their exosomes significantly decreased during extensive sub-culturing. The present study showed that MSC-derived exosomes as an effective cell-free therapy could prevent proliferation of PBMCs. However, further evaluations are need to move towards a functional approach that can be translated to the clinic.

Exosomes as Drug Delivery Systems: Endogenous Nanovehicles for Treatment of Systemic Lupus Erythematosus

Exosomes, nanometer-sized lipid-bilayer-enclosed extracellular vesicles (EVs), have attracted increasing attention due to their inherent ability to shuttle proteins, lipids and genes between cells and their natural affinity to target cells. Their intrinsic features such as stability, biocompatibility, low immunogenicity and ability to overcome biological barriers, have prompted interest in using exosomes as drug delivery vehicles, especially for gene therapy. Evidence indicates that exosomes play roles in both immune stimulation and tolerance, regulating immune signaling and inflammation. To date, exosome-based nanocarriers delivering small molecule drugs have been developed to treat many prevalent autoimmune diseases. This review highlights the key features of exosomes as drug delivery vehicles, such as therapeutic cargo, use of targeting peptide, loading method and administration route with a broad focus. In addition, we outline the current state of evidence in the field of exosome-based drug delivery systems in systemic lupus erythematosus (SLE), evaluating exosomes derived from various cell types and engineered exosomes.

Potential Benefits of Allogeneic Haploidentical Adipose Tissue-Derived Stromal Vascular Fraction in a Hutchinson-Gilford Progeria Syndrome Patient

Hutchinson-Gilford progeria syndrome (HGPS) is a rare, fatal, and genetic disorder in the LMNA gene encoding for prelamin A. Normally, prelamin A is processed to become lamin A protein. In HGPS patients, there is a heterozygous mutation in LMNA gene, in which there is a deletion of genetic codes responsible for 50 amino acids at the C-terminus of prelamin A. The processing of the abnormal prelamin A results in abnormal lamin A protein, called progerin, causing symptoms of accelerated early aging, probably due to the inflammaging process. It is well known that adipose tissue-derived mesenchymal stem cells (MSCs) have anti-inflammatory effects by modulating inflammatory cytokines and by extracellular vesicles. Here, we present a case of an HGPS patient who responded positively to injections of allogeneic haploidentical adipose tissue-derived stromal vascular fractions containing MSCs by showing rapid height and weight growth along with increased blood level of insulin-like growth factor 1.

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).

Human Adipose Tissue-Derived Stromal Cells Suppress Human, but Not Murine Lymphocyte Proliferation, via Indoleamine 2,3-Dioxygenase Activity

Over recent years, mesenchymal stromal cells (MSC) have gained immense attraction in immunotherapy, regenerative medicine and tissue engineering. MSC microenvironment modulation occurs through synergy of direct cell-cell contact, and secreted soluble factors and extracellular vesicles (EV). MSC-derived EV have been suggested as cell-free immunomodulatory alternative to MSC; however, previous findings have challenged this. Furthermore, recent data suggest that evaluating the mechanism of action of human MSC (hMSC) in animal models might promote adverse immune reactions or lack of functionality due to xeno-incompatibilities. In this study, we first assessed the immunomodulatory strength of different human MSC sources on in vitro stimulated T cells and compared this to interferon-gamma (IFNγ) primed MSC conditioned medium (CM) and EV. Second, we addressed the main molecular mechanisms, and third, we assessed the MSC in vitro immunosuppressive effect across interspecies barriers. We identified human adipose tissue-derived stromal cells (ASC) with strongest immunomodulatory strength, followed by bone marrow (BM) and cord blood-derived MSC (CB). Whilst CM from primed ASC managed to exert analogous effects as their cellular counterpart, EV derived thereof did not, reproducing previous findings. IFNγ-induced indoleamine 2,3-dioxygenase (IDO) activity was identified as key mechanism to suppress human lymphocyte proliferation, as in the presence of the IDO inhibitor epacadostat (Epac) a stimulation of proliferation was seen. In addition, we revealed MSC immunosuppressive effects to be species-specific, because human cells failed to suppress murine lymphocyte proliferation. In summary, ASC were the strongest immunomodulators with the IDO-kynurenine pathway being key within the human system. Importantly, the in vitro lack of interspecies immunomodulatory strength suggests that preclinical data need to be carefully interpreted especially when considering a possible translation to clinical field.

Improving hematopoietic engraftment: Potential role of mesenchymal stromal cell-derived extracellular vesicles

The therapeutic effects of mesenchymal stromal cells (MSCs) in graft failure or poor graft function after allogenic hematopoietic stem cell transplantation (HSCT) are currently undergoing clinical evaluation. MSCs exert their functions, at least partially, through the secretion of extracellular vesicles (MSC-EVs). The available information on the biological potential of MSC-EVs to improve hematopoietic function, both in in vitro studies and in reported preclinical models, focusing on the possible mechanisms of these effects are summarized in the current review. The potential advantages of EVs over MSCs are also discussed, as well as the limitations and uncertainties in terms of isolation, characterization, mechanism of action in this setting, and industrial scalability that should be addressed for their potential clinical application.

Synergistic therapeutic effect of mesenchymal stem cells and tolerogenic dendritic cells in an acute colitis mouse model

Cell-based therapy with tolerizing cells has been applied for the treatment of inflammatory bowel disease (IBD) in previous experimental and clinical studies with promising results. In the current study, we utilized the dextran sulfate sodium (DSS)-induced colitis model, to investigate if tolerogenic dendritic cell-mesenchymal stem cell (tDC-MSC) combination therapy can augment the therapeutic effects of single transplantation of each cell type. The effect of MSC and tDC co-transplantation on the severity of colitis was assessed by daily monitoring of body weight, stool consistency, and rectal bleeding, and compared with control groups. Moreover, the colon length, colon weight, myeloperoxidase (MPO) activity were measured and evaluated with histological analysis of colon tissues. The Treg cell percentage and cytokine levels in spleens and mesenteric lymph nodes (MLNs) were measured by flow cytometry and ELISA, respectively. The results showed co-transplantation of MSCs and tDCs was more effective in alleviating the clinical and histological manifestations of colitis than monotherapy, especially when compared with MSC alone. The protective effects of tDC-MSC were accompanied by the induction of Treg cells and increased the production of anti-inflammatory cytokines in spleens and mesenteric lymph nodes. Together, co-transplantation of MSCs and tDCs could be a promising and effective therapeutic approach in the treatment of IBD.

Immunosuppressive Effects of Mesenchymal Stem Cells-derived Exosomes

Mesenchymal stem cells (MSCs) have become important seed cells in therapy because of their immunosuppressive function and anti-inflammatory effects. MSCs exert immunosuppressive effects through direct contact or paracrine action. The paracrine functions of MSCs are at least partially mediated by exosomes, which are membrane vesicles, carrying abundant proteins, nucleic acids and other active molecules. MSC-exos have heterogeneity. The exosomes from different donors, tissues generations of MSCs carry different bioactive molecules. These cargos are transferred to recipient cells by endocytosis or binding to proteins on the receptor surface to mediate intercellular communication between different cell types and affect the functions of the recipient cells. Exosomes play an important role in the regulation of the immune system. Exosomes derived from MSCs (MSC-exos) carry immunomodulatory effectors or transmit active signal molecules to regulate the biological activities of immune cells and thus mediating immune suppression, especially on macrophages and T cells. Mitochondria and autophagy-related pathways are also associated with MSC-exos immunosuppressive effects. Graphical Abstract.

Mesenchymal stem cell-derived exosome: a promising alternative in the therapy of Alzheimer's disease

Alzheimer's disease (AD) has been a devastating public health with the development of global aging. Approaches for reducing the current AD epidemic are becoming a primary focus of human healthcare due to the lack of achieved lasting and complete remission strategies to treat AD with the characteristics of heterogeneity and complexity. Exosomes, which is the new emerging approach to intercellular communication, provide novel perspective on identified therapeutic strategies of AD. Mesenchymal stem cell-derived exosomes (MSC-exos) are emerging to be an appealing therapeutic tool for AD, with the donor-derived properties and the characteristics of minimal immunogenicity, effortless storage, nature delivery vehicles, and low risks of tumor formation based on the previous researches. In this review, we elaborate the mechanism of MSC-exos in the treatment of AD and discuss limitations in the clinical application.

Mesenchymal Stem Cells in Asthma

Asthma is one of the worldwide respiratory health problem that affect children and adult. Current treatment strategies such as conventional and allergen immunotherapy still fall behind. Mesenchymal stem cells (MSCs) have wide regenerative capacity and immunoregulatory activity with their wide range of secretions and contact dependent manner. In this review, we focus on the current treatment strategies for asthma and MSCs as a new therapeutic tool.

Effects of Cell-Derived Microparticles on Immune Cells and Potential Implications in Clinical Medicine

In the past few years, interest has increased in cell-derived microparticles (MPs), which are defined by their size of from 0.1 to 1 μm, and can be derived from various cell types, including endothelial cells, leukocytes, red blood cells (RBCs), and platelets. These MPs carry negatively charged phosphatidylserine (PS) on their surfaces and proteins packaged from numerous cellular components. MPs that have been shed by the body can play important roles in the pathophysiology of diseases and can affect various biological systems. Among these systems, the immune components have been shown to be modulated by MPs. Therefore, understanding the roles of MPs in the immune system is crucial to developing alternative therapeutic treatments for diseases. This review describes the effects of MPs on various immune cells and provides plausible potential applications of the immune-modulating properties of MPs in clinical medicine.

Quality control and immunomodulatory potential for clinical-grade equine bone marrow-derived mesenchymal stromal cells and conditioned medium

This study aimed to assess the safety and reproducibility of cell therapy for its use in clinical practice. We performed immunophenotypic characterization of equine bone marrow-derived mesenchymal stromal cells (BMMSCs) by flow cytometry using CD90, CD19, CD14, CD105, CD45, and HLA-DR markers (n = 4); GTG banding cytogenetic analysis (n = 3); and microbiological quality control (n = 4). The immunomodulatory potentials of BMMSCs (n = 4) and its conditioned medium (CM, n = 3) were investigated by in vitro lymphocyte inhibition assay using phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs). BMMSCs populations isolated from all animals showed high expression of CD90 and CD105, and low expression of CD19, CD4, CD45, and HLA-DR. Of the 60 metaphases analyzed, 5% presented aneuploidy on random chromosomes and no contamination was found based on microbiological analyses. Both treatments significantly inhibited lymphocyte proliferation (> 50%), compared with PHA-stimulated PBMCs (p < 0.0001). These promising results for BMMSCs and CM justify their potential as a therapeutic approach for inflammatory diseases. The techniques used in this study were effective in assessing the quality and determining the minimum criteria for the clinical use of BMMSCs in veterinary medicine.

Biology and therapeutic potential of mesenchymal stem cell-derived exosomes

Mesenchymal stem cells (MSC) are multipotent stromal cells with the potential to differentiate into several cell types. MSC‐based therapy has emerged as a promising strategy for various diseases. Accumulating evidence suggests that the paracrine effects of MSC are partially exerted by the secretion of soluble factors, in particular exosomes. MSC‐derived exosomes are involved in intercellular communication through transfer of proteins, RNA, DNA and bioactive lipids, which might constitute a novel intercellular communication mode. This review illustrates the current knowledge on the composition and biological functions as well as the therapeutic potential of MSC‐derived exosomes in cancer, with a focus on clinical translation opportunities.

Umbilical Cord-Derived Mesenchymal Stem Cells Are Able to Use bFGF Treatment and Represent a Superb Tool for Immunosuppressive Clinical Applications

Mesenchymal stem cells (MSCs) have become a promising tool in cellular therapy for restoring immune system haemostasis; however, the success of clinical trials has been impaired by the lack of standardized manufacturing processes. This study aims to determine the suitability of source tissues and culture media for the production of MSC-based advanced therapy medicinal products (ATMPs) and to define parameters to extend the set of release criteria. MSCs were isolated from umbilical cord (UC), bone marrow and lipoaspirate and expanded in three different culture media. MSC phenotype, proliferation capacity and immunosuppressive parameters were evaluated in normal MSCs compared to primed MSCs treated with cytokines mimicking an inflammatory environment. Compared to bone marrow and lipoaspirate, UC-derived MSCs (UC-MSCs) showed the highest proliferative capacity, which was further enhanced by media supplemented with bFGF, while the cells maintained their immunosuppressive characteristics. Moreover, UC-MSCs expanded in the bFGF-enriched medium were the least sensitive to undesirable priming-induced changes in the MSC phenotype. Surface markers and secreted factors were identified to reflect the cell response to inflammatory priming and to be variable among MSCs from different source tissues. This study demonstrates that UC is a favorable cell source for manufacturing MSC-based ATMPs for immunosuppressive applications. UC-MSCs are able to use the bFGF-enriched medium for higher cell yields without the impairment of immunosuppressive parameters and undesirable phenotype changes after inflammatory preconditioning of MSCs before transplantation. Additionally, immunosuppressive parameters were identified to help finding predictors of clinically efficient MSCs in the following clinical trials.

Mesenchymal stem cells and mesenchymal stem cell-derived extracellular vesicles: Potential roles in rheumatic diseases

BACKGROUND

Mesenchymal stem cells (MSCs) have been widely investigated in rheumatic disease due to their immunomodulatory and regenerative properties. Recently, mounting studies have implicated the therapeutic potency of MSCs mostly due to the bioactive factors they produce. Extracellular vesicles (EVs) derived from MSCs have been identified as a promising cell-free therapy due to low immunogenicity. Rheumatic disease, primarily including rheumatoid arthritis and osteoarthritis, is a group of diseases in which immune dysregulation and chronic progressive inflammation lead to irreversible joint damage. Targeting MSCs and MSC-derived EVs may be a more effective and promising therapeutic strategy for rheumatic diseases.

AIM

To evaluate the potential therapeutic effectiveness of MSCs and EVs generated from MSCs in rheumatic diseases.

METHODS

PubMed was searched for the relevant literature using corresponding search terms alone or in combination. Papers published in English language from January 1999 to February 2020 were considered. Preliminary screening of papers concerning analysis of "immunomodulatory function" or "regenerative function" by scrutinizing the titles and abstracts of the literature, excluded the papers not related to the subject of the article. Some other related studies were obtained by manually retrieving the reference lists of papers that comply with the selection criteria, and these studies were screened to meet the final selection and exclusion criteria.

RESULTS

Eighty-six papers were ultimately selected for analysis. After analysis of the literature, it was found that both MSCs and EVs generated from MSCs have great potential in multiple rheumatic diseases, such as rheumatoid arthritis and osteoarthritis, in repair and regeneration of tissues, inhibition of inflammatory response, and regulation of body immunity via promoting chondrogenesis, regulating innate and adaptive immune cells, and regulating the secretion of inflammatory factors. But EVs from MSCs exhibit much more advantages over MSCs, which may represent another promising cell-free restorative strategy. Targeting MSCs and MSC-derived EVs may be a more efficient treatment for patients with rheumatic diseases.

CONCLUSION

The enormous potential of MSCs and EVs from MSCs in immunomodulation and tissue regeneration offers a new idea for the treatment of rheumatism. However, more in-depth exploration is needed before their clinical application.

Mechanisms behind the Immunoregulatory Dialogue between Mesenchymal Stem Cells and Th17 Cells

Mesenchymal stem cells (MSCs) exhibit potent immunoregulatory abilities by interacting with cells of the adaptive and innate immune system. In vitro, MSCs inhibit the differentiation of T cells into T helper 17 (Th17) cells and repress their proliferation. In vivo, the administration of MSCs to treat various experimental inflammatory and autoimmune diseases, such as rheumatoid arthritis, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and bowel disease showed promising therapeutic results. These therapeutic properties mediated by MSCs are associated with an attenuated immune response characterized by a reduced frequency of Th17 cells and the generation of regulatory T cells. In this manuscript, we review how MSC and Th17 cells interact, communicate, and exchange information through different ways such as cell-to-cell contact, secretion of soluble factors, and organelle transfer. Moreover, we discuss the consequences of this dynamic dialogue between MSC and Th17 well described by their phenotypic and functional plasticity.

Mesenchymal stromal cells and their secreted extracellular vesicles as therapeutic tools for COVID-19 pneumonia?

The COVID-19 epidemic represents an unprecedented global health emergency, further aggravated by the lack of effective therapies. For this reason, several clinical trials are testing different off-label drugs, already approved for other pathologies. Mesenchymal stem/stromal cells (MSCs) have been tested during the last two decades for the treatment of various pathologic conditions, including acute and chronic lung diseases, both in animal models and in patients. In particular, promising results have been obtained in the experimental therapy of acute respiratory distress syndrome, which represents the most threatening complication of COVID-19 infection. Furthermore, more recently, great interest has been devoted to the possible clinical applications of extracellular vesicles secreted by MSCs, nanoparticles that convey much of the biological effects and of the therapeutic efficacy of their cells of origin. This review summarizes the experimental evidence underlying the possible use of MSCs and of MSC-EVs in severe COVID-19 infection and underlines the need to evaluate the possible efficacy of these therapeutic approaches through controlled studies under the supervision of the Regulatory Authorities.

Immunosuppressive properties of cytochalasin B-induced membrane vesicles of mesenchymal stem cells: comparing with extracellular vesicles derived from mesenchymal stem cells

Extracellular vesicles derived from mesenchymal stem cells (MSCs) represent a novel approach for regenerative and immunosuppressive therapy. Recently, cytochalasin B-induced microvesicles (CIMVs) were shown to be effective drug delivery mediators. However, little is known about their immunological properties. We propose that the immunophenotype and molecular composition of these vesicles could contribute to the therapeutic efficacy of CIMVs. To address this issue, CIMVs were generated from murine MSC (CIMVs-MSCs) and their cytokine content and surface marker expression determined. For the first time, we show that CIMVs-MSCs retain parental MSCs phenotype (Sca-1⁺, CD49e⁺, CD44⁺, CD45⁻). Also, CIMVs-MSCs contained a cytokine repertoire reflective of the parental MSCs, including IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12(p40), IL-13, IL-17, CCL2, CCL3, CCL4, CCL5, CCL11, G-CSF, GM-CSF and TNF-α. Next, we evaluated the immune-modulating properties of CIMVs-MSCs in vivo using standard preclinical tests. MSCs and CIMVs-MSCs reduced serum levels of anti-sheep red blood cell antibody and have limited effects on neutrophil and peritoneal macrophage activity. We compared the immunomodulatory effect of MSCs, CIMVs and EVs. We observed no immunosuppression in mice pretreated with natural EVs, whereas MSCs and CIMVs-MSCs suppressed antibody production in vivo. Additionally, we have investigated the biodistribution of CIMVs-MSCs in vivo and demonstrated that CIMVs-MSCs localized in liver, lung, brain, heart, spleen and kidneys 48 h after intravenous injection and can be detected 14 days after subcutaneous and intramuscular injection. Collectively our data demonstrates immunomodulatory efficacy of CIMVs and supports their further preclinical testing as an effective therapeutic delivery modality.

Mechanisms underlying the protective effects of mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. The therapeutic potential of MSCs is attributed to complex cellular and molecular mechanisms of action including differentiation into multiple cell lineages and regulation of immune responses via immunomodulation. The plasticity of MSCs in immunomodulation allow these cells to exert different immune effects depending on different diseases. Understanding the biology of MSCs and their role in treatment is critical to determine their potential for various therapeutic applications and for the development of MSC-based regenerative medicine. This review summarizes the recent progress of particular mechanisms underlying the tissue regenerative properties and immunomodulatory effects of MSCs. We focused on discussing the functional roles of paracrine activities, direct cell-cell contact, mitochondrial transfer, and extracellular vesicles related to MSC-mediated effects on immune cell responses, cell survival, and regeneration. This will provide an overview of the current research on the rapid development of MSC-based therapies.

Veterinary Regenerative Medicine for Musculoskeletal Disorders: Can Mesenchymal Stem/Stromal Cells and Their Secretome Be the New Frontier?

Regenerative medicine aims to restore the normal function of diseased or damaged cells, tissues, and organs using a set of different approaches, including cell-based therapies. In the veterinary field, regenerative medicine is strongly related to the use of mesenchymal stromal cells (MSCs), which belong to the body repair system and are defined as multipotent progenitor cells, able to self-replicate and to differentiate into different cell types. This review aims to take stock of what is known about the MSCs and their use in the veterinary medicine focusing on clinical reports on dogs and horses in musculoskeletal diseases, a research field extensively reported in the literature data. Finally, a perspective regarding the use of the secretome and/or extracellular vesicles (EVs) in the veterinary field to replace parental MSCs is provided. The pharmaceuticalization of EVs is wished due to the realization of a Good Manufacturing Practice (GMP product suitable for clinical trials.

Controlled Release of Stem Cell Secretome Attenuates Inflammatory Response against Implanted Biomaterials

Inflammatory response against implanted biomaterials impairs their functional integration and induces medical complications in the host's body. To suppress such immune responses, one approach is the administration of multiple drugs to halt inflammatory pathways. This challenges patient's adherence and can cause additional complications such as infection. Alternatively, biologics that regulate multiple inflammatory pathways are attractive agents in addressing the implants immune complications. Secretome of mesenchymal stromal cells (MSCs) is a multipotent biologic, regulating the homeostasis of lymphocytes and leukocytes. Here, it is reported that alginate microcapsules loaded with processed conditioned media (pCM-Alg) reduces the infiltration and/or expression of CD68+ macrophages likely through the controlled release of pCM. In vitro cultures revealed that alginate can dose dependently induce macrophages to secrete TNFα, IL-6, IL-1β, and GM-CSF. Addition of pCM to the cultures attenuates the secretion of TNFα (p = 0.023) and IL-6 (p < 0.0001) by alginate or lipopolysaccharide (LPS) stimulations. Mechanistically, pCM suppressed the NfκB pathway activation of macrophages in response to LPS (p < 0.0001) in vitro and cathepsin activity (p = 0.005) in response to alginate in vivo. These observations suggest the efficacy of using MSC-derived secretome to prevent or delay the host rejection of implants.

Extracellular vesicles derived from different sources of mesenchymal stem cells: therapeutic effects and translational potential

Mesenchymal stem cells (MSCs) were known to have excellent properties in cell therapy. However, the risk of immune rejection associated with cell transplant therapy hampers its use. Extracellular vesicles secreted by MSCs derived from different sources that contain therapeutic molecules such as RNA and proteins, which is a novel strategy for cell-free therapy. Recently, researches show EVs from MSCs (MSC-EVs) of different sources have special functions and effects on different diseases. Here, we collected these researches and compared them to each other. In addition, their potential and possible application in clinical treatment are described.

Present and Future of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common respiratory disorder among infants born extremely preterm. The pathogenesis of BPD involves multiple prenatal and postnatal mechanisms affecting the development of a very immature lung. Their combined effects alter the lung's morphogenesis, disrupt capillary gas exchange in the alveoli, and lead to the pathological and clinical features of BPD. The disorder is ultimately the result of an aberrant repair response to antenatal and postnatal injuries to the developing lungs. Neonatology has made huge advances in dealing with conditions related to prematurity, but efforts to prevent and treat BPD have so far been only partially effective. Seeing that BPD appears to have a role in the early origin of chronic obstructive pulmonary disease, its prevention is pivotal also in long-term respiratory outcome of these patients. There is currently some evidence to support the use of antenatal glucocorticoids, surfactant therapy, protective noninvasive ventilation, targeted saturations, early caffeine treatment, vitamin A, and fluid restriction, but none of the existing strategies have had any significant impact in reducing the burden of BPD. New areas of research are raising novel therapeutic prospects, however. For instance, early topical (intratracheal or nebulized) steroids seem promising: they might help to limit BPD development without the side effects of systemic steroids. Evidence in favor of stem cell therapy has emerged from several preclinical trials, and from a couple of studies in humans. Mesenchymal stromal/stem cells (MSCs) have revealed a reparatory capability, preventing the progression of BPD in animal models. Administering MSC-conditioned media containing extracellular vesicles (EVs) have also demonstrated a preventive action, without the potential risks associated with unwanted engraftment or the adverse effects of administering cells. In this paper, we explore these emerging treatments and take a look at the revolutionary changes in BPD and neonatology on the horizon.

Biological Considerations in Scaling Up Therapeutic Cell Manufacturing

Cell therapeutics - using cells as living drugs - have made advances in many areas of medicine. One of the most clinically studied cell-based therapy products is mesenchymal stromal cells (MSCs), which have shown promising results in promoting tissue regeneration and modulating inflammation. However, MSC therapy requires large numbers of cells, the generation of which is not feasible via conventional planar tissue culture methods. Scale-up manufacturing methods (e.g., propagation on microcarriers in stirred-tank bioreactors), however, are not specifically tailored for MSC expansion. These processes may, in principle, alter the cell secretome, a vital component underlying the immunosuppressive properties and clinical effectiveness of MSCs. This review outlines our current understanding of MSC properties and immunomodulatory function, expansion in commercial manufacturing systems, and gaps in our knowledge that need to be addressed for effective up-scaling commercialization of MSC therapy.

Mesenchymal Stem/Stromal Cell-Derived Exosomes for Immunomodulatory Therapeutics and Skin Regeneration

Exosomes are nano-sized vesicles that serve as mediators for cell-to-cell communication. With their unique nucleic acids, proteins, and lipids cargo compositions that reflect the characteristics of producer cells, exosomes can be utilized as cell-free therapeutics. Among exosomes derived from various cellular origins, mesenchymal stem cell-derived exosomes (MSC-exosomes) have gained great attention due to their immunomodulatory and regenerative functions. Indeed, many studies have shown anti-inflammatory, anti-aging and wound healing effects of MSC-exosomes in various in vitro and in vivo models. In addition, recent advances in the field of exosome biology have enabled development of specific guidelines and quality control methods, which will ultimately lead to clinical application of exosomes. This review highlights recent studies that investigate therapeutic potential of MSC-exosomes and relevant mode of actions for skin diseases, as well as quality control measures required for development of exosome-derived therapeutics.