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

Novel Applications of Mesenchymal Stem Cell-derived Exosomes for Myocardial Infarction Therapeutics

Cardiovascular diseases (CVDs) are the leading cause of mortality and morbidity globally, representing approximately a third of all deaths every year. The greater part of these cases is represented by myocardial infarction (MI), or heart attack as it is better known, which occurs when declining blood flow to the heart causes injury to cardiac tissue. Mesenchymal stem cells (MSCs) are multipotent stem cells that represent a promising vector for cell therapies that aim to treat MI due to their potent regenerative effects. However, it remains unclear the extent to which MSC-based therapies are able to induce regeneration in the heart and even less clear the degree to which clinical outcomes could be improved. Exosomes, which are small extracellular vesicles (EVs) known to have implications in intracellular communication, derived from MSCs (MSC-Exos), have recently emerged as a novel cell-free vector that is capable of conferring cardio-protection and regeneration in target cardiac cells. In this review, we assess the current state of research of MSC-Exos in the context of MI. In particular, we place emphasis on the mechanisms of action by which MSC-Exos accomplish their therapeutic effects, along with commentary on the current difficulties faced with exosome research and the ongoing clinical applications of stem-cell derived exosomes in different medical contexts.

Therapeutic effects of extracellular vesicles from human adipose-derived mesenchymal stem cells on chronic experimental autoimmune encephalomyelitis

Since in cell therapy, there are always concerns about immune rejection, genetic disability, and malignancies, special attention has been paid to extracellular vesicles (EVs) which are secreted by mesenchymal stem cells (MSCs). In the present study, we assessed and compared the therapeutic effects of human adipose-derived mesenchymal stem cells (hADSC) and hADSC-EVs from adipose tissue on experimental autoimmune encephalomyelitis (EAE). After induction of EAE in C57Bl/6 mice, they were treated with hADSCs, hADSC-EVs, or vehicle intravenously. The clinical score of all mice was recorded every other day. Mice were killed at Day 30 and splenocytes were isolated for proliferation assay and determination of the frequency of Treg cells by flow cytometry. Leukocyte infiltration by hematoxylin and eosin, percentages of demyelination areas by luxol fast blue, and mean fluorescence intensity of oligodendrocyte transcription factor 2 (OLIG2) and myelin basic protein (MBP) by immunohistochemistry were assessed in the spinal cord. Our results showed that the maximum mean clinical score and myelin oligodendrocyte glycoprotein-induced proliferation of splenocytes in hADSC- and hADSC-EV-treated mice were significantly lower than the control mice (p < .05). We also demonstrated that the frequency of CD4⁺ CD25⁺ Foxp3⁺ cells was significantly higher in the spleen of hADSC-treated mice than EAE control mice (p = .023). The inflammation score and the percentages of demyelination areas in hADSC- and hADSC-EV-treated groups significantly declined compared with the untreated control group (p < .05). We also showed that there was no significant difference in MFI of MBP and OLIG2 in the spinal cord of studied groups. Overall, we suggest that intravenous administration of hADSC-EVs attenuates the induced EAE through diminishing proliferative potency of T cells, mean clinical score, leukocyte infiltration, and demyelination in a chronic model of multiple sclerosis.

Extracellular Vesicles isolated from Mesenchymal Stromal Cells Modulate CD4+ T Lymphocytes Toward a Regulatory Profile

Mesenchymal stromal cells (MSCs) can generate immunological tolerance due to their regulatory activity in many immune cells. Extracellular vesicles (EVs) release is a pivotal mechanism by which MSCs exert their actions. In this study, we evaluate whether mesenchymal stromal cell extracellular vesicles (MSC-EVs) can modulate T cell response. MSCs were expanded and EVs were obtained by differential ultracentrifugation of the supernatant. The incorporation of MSC-EVs by T cells was detected by confocal microscopy. Expression of surface markers was detected by flow cytometry or CytoFLEX and cytokines were detected by RT-PCR, FACS and confocal microscopy and a miRNA PCR array was performed. We demonstrated that MSC-EVs were incorporated by lymphocytes in vitro and decreased T cell proliferation and Th1 differentiation. Interestingly, in Th1 polarization, MSC-EVs increased Foxp3 expression and generated a subpopulation of IFN-γ⁺/Foxp3⁺T cells with suppressive capacity. A differential expression profile of miRNAs in MSC-EVs-treated Th1 cells was seen, and also a modulation of one of their target genes, TGFbR2. MSC-EVs altered the metabolism of Th1-differentiated T cells, suggesting the involvement of the TGF-β pathway in this metabolic modulation. The addition of MSC-EVs in vivo, in an OVA immunization model, generated cells Foxp3⁺. Thus, our findings suggest that MSC-EVs are able to specifically modulate activated T cells at an alternative regulatory profile by miRNAs and metabolism shifting.

Comprehensive Molecular Profiles of Functionally Effective MSC-Derived Extracellular Vesicles in Immunomodulation

Accumulating evidence indicates that mesenchymal stem/stromal cell-derived extracellular vesicles (MSC-EVs) exhibit immunomodulatory effects by delivering therapeutic RNAs and proteins; however, the molecular mechanism underlying the EV-mediated immunomodulation is not fully understood. In this study, we found that EVs from early-passage MSCs had better immunomodulatory potency than did EVs from late-passage MSCs in T cell receptor (TCR)- or Toll-like receptor 4 (TLR4)-stimulated splenocytes and in mice with ocular Sjögren's syndrome. Moreover, MSC-EVs were more effective when produced from 3D culture of the cells than from the conventional 2D culture. Comparative molecular profiling using proteomics and microRNA sequencing revealed the enriched factors in MSC-EVs that were functionally effective in immunomodulation. Among them, manipulation of transforming growth factor β1 (TGF-β1), pentraxin 3 (PTX3), let-7b-5p, or miR-21-5p levels in MSCs significantly affected the immunosuppressive effects of their EVs. Furthermore, there was a strong correlation between the expression levels of TGF-β1, PTX3, let-7b-5p, or miR-21-5p in MSC-EVs and their suppressive function. Therefore, our comparative strategy identified TGF-β1, PTX3, let-7b-5p, or miR-21-5p as key molecules mediating the therapeutic effects of MSC-EVs in autoimmune disease. These findings would help understand the molecular mechanism underlying EV-mediated immunomodulation and provide functional biomarkers of EVs for the development of robust EV-based therapies.

Challenges for Immunotherapy in Multiple Myeloma: Bone Marrow Microenvironment-Mediated Immune Suppression and Immune Resistance

The power of immunotherapy in the battle of Multiple Myeloma (MM) started with allogeneic stem cell transplantation, and was rediscovered with immunomodulatory drugs and extended with the outstanding results achieved with targeted antibodies. Today, next to powerful antibodies Elotuzumab and Daratumumab, several T-cell-based immunotherapeutic approaches, such as bispecific antibodies and chimeric antigen receptor-transduced T-cells (CAR T-cells) are making their successful entry in the immunotherapy arena with highly promising results in clinical trials. Nonetheless, similar to what is observed in chemotherapy, MM appears capable to escape from immunotherapy, especially through tight interactions with the cells of the bone marrow microenvironment (BM-ME). This review will outline our current understanding on how BM-ME protects MM-cells from immunotherapy through immunosuppression and through induction of intrinsic resistance against cytotoxic effector mechanisms of T- and NK-cells.

[Review for different sources of exosomes in bone tissue engineering research]

Exosomes are 40-100 nm vesicles that are released into the extracellular environment upon the fusion of multivesicular bodies with the plasma membrane. The biologically cargoes transported by exosomes are diverse. Exosomes are important carriers of signal transmission and interaction between cells. Exosomes are believed to play an important role in tissue repair and bone regeneration. Studies have evaluated that exosomes secreted by cells play an increasingly significant roles in bone tissue engineering and have multiple functions, including regulating immunity, promoting cell proliferation and differentiation, enhancing bone regeneration and angiogenesis. The review analyzes the characteristics and biological properties of different cell-derived exosomes in the bone environment, summarizes their research progress in bone repair, and discusses the challenges and future directions for their application in bone tissue engineering.

Extracellular Vesicles After Allogeneic Hematopoietic Cell Transplantation: Emerging Role in Post-Transplant Complications

Extracellular vesicles (EVs) play an important role in the cellular crosstalk by transferring bioactive molecules through biological barriers from a cell to another, thus influencing recipient cell functions and phenotype. Therefore, EVs are increasingly being explored as biomarkers of disease progression or response to therapy and as potential therapeutic agents in different contexts including in hematological malignancies. Recently, an EV role has emerged in allogeneic hematopoietic cell transplantation (allo-HCT) as well. Allogeneic hematopoietic cell transplantation often represents the only curative option in several hematological disorders, but it is associated with potentially life-threatening complications that can have a significant impact on clinical outcomes. The most common complications have been well-established and include graft-versus-host disease and infections. Furthermore, relapse remains an important cause of treatment failure. The aim of this review is to summarize the current knowledge, the potential applications, and clinical relevance of EVs in allo-HCT. Herein, we will mainly focus on the immune-modulating properties of EVs, in particular those derived from mesenchymal stromal cells, as potential therapeutic strategy to improve allo-HCT outcome. Moreover, we will briefly describe the main findings on EVs as biomarkers to monitor graft-versus-host disease onset and tumor relapse.

Pro-Inflammatory Priming of Umbilical Cord Mesenchymal Stromal Cells Alters the Protein Cargo of Their Extracellular Vesicles

Umbilical cord mesenchymal stromal cells (UCMSCs) have shown an ability to modulate the immune system through the secretion of paracrine mediators, such as extracellular vesicles (EVs). However, the culture conditions that UCMSCs are grown in can alter their secretome and thereby affect their immunomodulatory potential. UCMSCs are commonly cultured at 21% O₂ in vitro, but recent research is exploring their growth at lower oxygen conditions to emulate circulating oxygen levels in vivo. Additionally, a pro-inflammatory culture environment is known to enhance UCMSC anti-inflammatory potential. Therefore, this paper examined EVs from UCMSCs grown in normal oxygen (21% O₂), low oxygen (5% O₂) and pro-inflammatory conditions to see the impact of culture conditions on the EV profile. EVs were isolated from UCMSC conditioned media and characterised based on size, morphology and surface marker expression. EV protein cargo was analysed using a proximity-based extension assay. Results showed that EVs had a similar size and morphology. Differences were found in EV protein cargo, with pro-inflammatory primed EVs showing an increase in proteins associated with chemotaxis and angiogenesis. This showed that the UCMSC culture environment could alter the EV protein profile and might have downstream implications for their functions in immunomodulation.

Human Fetal Liver Mesenchymal Stem Cell-Derived Exosomes Impair Natural Killer Cell Function

Mesenchymal stem cells (MSCs) are powerful immunomodulators that regulate the diverse functions of immune cells involved in allogeneic reactions, such as T cells and natural killer (NK) cells, through cell-cell contact or secreted factors. Exosomes secreted by MSCs may be involved in their regulatory functions, providing new therapeutic tools. Here, we showed that fetal liver (FL) MSC-derived exosomes inhibit proliferation, activation, and cytotoxicity of NK cells. Exosomes bearing latency associated peptide (LAP), TGFβ, and thrombospondin 1 (TSP1), a regulatory molecule for TGFβ, induced downstream TGFβ/Smad2/3 signaling in NK cells. The inhibition of TGFβ, using a neutralizing anti-TGFβ antibody, restored NK proliferation, differentiation, and cytotoxicity, demonstrating that FL-MSC-derived exosomes exert their inhibition on NK cell function via TGFβ. These results suggest that FL-MSC-derived exosomes regulate NK cell functions through exosome-associated TGFβ.

Immunoregulatory Effects of Stem Cell-Derived Extracellular Vesicles on Immune Cells

Recent investigations on the regulatory action of extracellular vesicles (EVs) on immune cells in vitro and in vivo have sparked interest on the subject. As commonly known, EVs are subcellular components secreted by a paracellular mechanism and are essentially a group of nanoparticles containing exosomes, microvesicles, and apoptotic bodies. They are double-layer membrane-bound vesicles enriched with proteins, nucleic acids, and other active compounds. EVs are recognized as a novel apparatus for intercellular communication that acts through delivery of signal molecules. EVs are secreted by almost all cell types, including stem/progenitor cells. The EVs derived from stem/progenitor cells are analogous to the parental cells and inhibit or enhance immune response. This review aims to provide its readers a comprehensive overview of the possible mechanisms underlying the immunomodulatory effects exerted by stem/progenitor cell-derived EVs upon natural killer (NK) cells, dendritic cells (DCs), monocytes/macrophages, microglia, T cells, and B cells.

Effect of mesenchymal stem cell-derived exosomes on the induction of mouse tolerogenic dendritic cells

Dendritic cells (DCs) orchestrate innate inflammatory responses and adaptive immunity through T‐cell activation via direct cell–cell interactions and/or cytokine production. Tolerogenic DCs (tolDCs) help maintain immunological tolerance through the induction of T‐cell unresponsiveness or apoptosis, and generation of regulatory T cells. Mesenchymal stromal cells (MSCs) are adult multipotent cells located within the stroma of bone marrow (BM), but they can be isolated from virtually all organs. Extracellular vesicles and exosomes are released from inflammatory cells and act as messengers enabling communication between cells. To investigate the effects of MSC‐derived exosomes on the induction of mouse tolDCs, murine adipose‐derived MSCs were isolated from C57BL/6 mice and exosomes isolated by ExoQuick‐TC kits. BM‐derived DCs (BMDCs) were prepared and cocultured with MSCs‐derived exosomes (100 μg/ml) for 72 hr. Mature BMDCs were derived by adding lipopolysaccharide (LPS; 0.1μg/ml) at Day 8 for 24 hr. The study groups were divided into (a) immature DC (iDC, Ctrl), (b) iDC + exosome (Exo), (c) iDC + LPS (LPS), and (d) iDC + exosome + LPS (EXO + LPS). Expression of CD11c, CD83, CD86, CD40, and MHCII on DCs was analyzed at Day 9. DC proliferation was assessed by coculture with carboxyfluorescein succinimidyl ester‐labeled BALB/C‐derived splenocytes p. Interleukin‐6 (IL‐6), IL‐10, and transforming growth factor‐β (TGF‐β) release were measured by enzyme‐linked immunosorbent assay. MSC‐derived exosomes decrease DC surface marker expression in cells treated with LPS, compared with control cells ( ≤ .05). MSC‐derived exosomes decrease IL‐6 release but augment IL‐10 and TGF‐β release (p ≤ .05). Lymphocyte proliferation was decreased (p ≤ .05) in the presence of DCs treated with MSC‐derived exosomes. CMSC‐derived exosomes suppress the maturation of BMDCs, suggesting that they may be important modulators of DC‐induced immune responses.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Novel Cell-Free Therapy

In recent years, mesenchymal stem/stromal cells (MSCs) have widely been considered as therapeutic tools in basic researches and clinical trials. Accumulating evidence supports the idea that MSCs perform their therapeutic roles in paracrine manner especially through trophic factors and extracellular vesicles (EVs). Compared to cells, EVs have several advantages to be used as therapeutic agents, such as they lack self-replicating capabilities, dangers of ectopic differentiation, and tumor formation, genetic instability, and cellular rejection by the immune system. Since the MSC-derived EVs (MSC-EVs) appear to exert similar therapeutic effects of their parent cells, such as ability to arrive themselves to the site of injury and immunomodulatory properties, MSC-EVs have been widely studied in many animal models, including kidney, liver, cardiovascular, immunological, and neurological diseases. Regarding this, MSC-EVs look to be a novel and interesting approach to be studied in clinical trials of different inflammatory diseases. In this review, we summarize the properties and applications of MSC-EVs in different diseases.

Impact of Mesenchymal Stromal Cells and Their Extracellular Vesicles in a Rat Model of Kidney Rejection

Background

Mesenchymal stromal cells (MSCs) from different sources possess great therapeutic potential due to their immunomodulatory properties associated with allograft tolerance. However, a crucial role in this activity resides in extracellular vesicles (EVs) and signaling molecules secreted by cells. This study aimed to evaluate the immunomodulatory properties of donor and recipient MSCs isolated from adipose tissue (AD) or bone marrow (BM) and their EVs on kidney outcome in a rat kidney transplant model.

Methods

The heterotopic-kidney-transplant Fisher-to-Lewis rat model (F-L) was performed to study mixed cellular and humoral rejection. After kidney transplantation, Lewis recipients were assigned to 10 groups; two control groups; four groups received autologous MSCs (either AD- or BM- MSC) or EVs (derived from both cell types); and four groups received donor-derived MSCs or EVs. AD and BM-EVs were purified by ultracentrifugation. Autologous cell therapies were administered three times intravenously; immediately after kidney transplantation, 4 and 8 weeks, whereas donor-derived cell therapies were administered once intravenously immediately after transplantation. Survival and renal function were monitored. Twelve weeks after kidney transplantation grafts were harvested, infiltrating lymphocytes were analyzed by flow cytometry and histological lesions were characterized.

Results

Autologous AD- and BM-MSCs, but not their EVs, prolonged graft and recipient survival in a rat model of kidney rejection. Autologous AD- and BM-MSCs significantly improved renal function during the first 4 weeks after transplantation. The amelioration of graft function could be associated with an improvement in tubular damage, as well as in T, and NK cell infiltration. On the other side, the application of donor-derived AD-MSC was harmful, and all rats died before the end of the protocol. AD-EVs did not accelerate the rejection. Contrary to autologous MSCs results, the single dose of donor-derived BM-MSCs is not enough to ameliorate kidney graft damage.

Conclusion

EVs treatments did not exert any benefit in our experimental settings. In the autologous setting, BM-MSCs prompted as a potentially promising therapy to improve kidney graft outcomes in rats with chronic mixed rejection. In the donor-derived setting, AD-MSC accelerated progression to end-stage kidney disease. Further experiments are required to adjust timing and dose for better long-term outcomes.

Effect of p53 activation through targeting MDM2/MDM4 heterodimer on T regulatory and effector cells in the peripheral blood of Type 1 diabetes patients

Various immunotherapies for the treatment of type 1 diabetes are currently under investigation. Some of these aim to rescue the remaining beta cells from autoimmune attack caused by the disease. Among the strategies employed, p53 has been envisaged as a possible target for immunomodulation. We studied the possible effect of p53 activation on Treg subsets and Treg/Teff balance in type 1 diabetes patients' PBMC. Upon p53 activation, we observed an increase in CD8+ Treg and activated CD8+ Teff whilst CD8+ Teff cells significantly decreased in healthy PBMC when stimulated with anti-CD3/CD28. No effect was detected on percentages of CD4+ Treg, while a reduction was seen in CD4+ Teff cells and an increase in activated CD4+ Teff cells. In patients' PBMC, upon p53 activation followed by 6 days of anti-CD3/CD28 stimulation, CD8+ Treg and activated CD8+ Teff were increased while CD8+ Teff were decreased. No differences were detected in the CD4+ counterparts. CD8+ Teff PD1+, CD8+ Teff PD1low were increased upon p53 activation in type 1 diabetics compared to controls while CD8+ Teff PD1high were increased in both groups. The same increased percentages were detected for CD4+ counterparts. CD4+ Treg PD1high cells were decreased in diabetics upon p53 activation at day 6 of anti-CD3/CD28 stimulation. In conclusion, a Teff dysregulation is observed upon p53 activation suggesting that molecules promoting p53 cannot be used for therapy in type 1 diabetics.

Bone marrow mesenchymal stem cell-derived exosome uptake and retrograde transport can occur at peripheral nerve endings

We investigated the occurrence of mesenchymal stem cell (MSC)-derived exosome uptake and retrograde transport at peripheral nerve endings using bone marrow MSCs (bMSCs) transduced with recombinant CD63-green fluorescent protein (GFP) lentiviral plasmid. GFP was used to track the release of bMSC-derived exosomes and the uptake and transport at peripheral nerve terminals, the dorsal root ganglion (DRG), and the spinal cord. In vitro cell culture and injection of a CD63-GFP exosome suspension into the right gastrocnemius muscle of an in vivo rat model were also performed. Fluorescence microscopy of co-cultured CD63-GFP exosomes and SH-SY5Y or BV2 cell lines and primary cultured DRG cells in a separate experiment demonstrated exosome uptake into DRG neurons and glia. Moreover, we observed both retrograde axoplasmic transport and hematogenous transport of exosomes injected into rat models at the DRG and the ipsilateral side of the anterior horn of the spinal cord using fluorescence microscopy, immunohistochemistry, and Western blot analyses. In conclusion, we showed that exosome uptake at peripheral nerve endings and retrograde transport of exosomes to DRG neurons and spinal cord motor neurons in the anterior horn can occur. In addition, our findings propose a novel drug delivery approach for treating neuronal diseases.

T cells and immune functions of plasma extracellular vesicles are differentially modulated from adults to centenarians

Aging is a universal and complex process that affects all tissues and cells types, including immune cells, in a process known as immunosenescence. However, many aspects of immunosenescence are not completely understood, as the characteristics of the immune cells of nonagenarians and centenarians or the features and implications of extracellular vesicles (EVs). In this study, we analyzed blood samples from 51 individuals aged 20-49 and 70-104 years. We found that senescent CD8 cells accumulate with age, while there is a partial reduction of senescent CD4 cells in nonagenarians and centenarians. Moreover, plasma EVs carry T cell specific markers, but no accumulation of "senescent-like EVs" was found within any of analyzed age groups. Our functional studies of cocultures of peripheral blood mononuclear cells and EVs showed that EVs enhance T cell viability and, under phytohemagglutinin stimulation, they influence cytokine secretion and cell activation in an age-dependent manner. These results underline the importance of EVs on the immune system functioning, and open new perspectives to further study their implication in human aging.

Therapeutic potential of mesenchymal stem/stromal cell-derived secretome and vesicles for lung injury and disease

Introduction: The acute respiratory distress syndrome (ARDS) is a devastating clinical condition common in patients with respiratory failure. Based largely on numerous preclinical studies and recent Phase I/II clinical trials, administration of stem cells, specifically mesenchymal stem or stromal cells (MSC), as a therapeutic for acute lung injury (ALI) holds great promise. However, concern for the use of stem cells, specifically the risk of iatrogenic tumor formation, remains unresolved. Accumulating evidence now suggest that stem cell-derived conditioned medium (CM) and/or extracellular vesicles (EV) might constitute compelling alternatives.Areas covered: The current review focuses on the preclinical studies testing MSC CM and/or EV as treatment for ALI and other inflammatory lung diseases.Expert opinion: Clinical application of MSC or their secreted CM may be limited by the cost of growing enough cells, the logistic of MSC storage, and the lack of standardization of what constitutes MSC CM. However, the clinical application of MSC EV remains promising, primarily due to the ability of EV to maintain the functional phenotype of the parent cell as a therapeutic. However, utilization of MSC EV will also require large-scale production, the cost of which may be prohibitive unless the potency of the EV can be increased.

Therapeutic Application of Mesenchymal Stem Cells Derived Extracellular Vesicles for Immunomodulation

The immunosuppressive potential of mesenchymal stem cells has been extensively investigated in many studies in vivo and in vitro. In recent years, a variety preclinical and clinical studies have demonstrated that mesenchymal stem cells ameliorate immune-mediated disorders, including autoimmune diseases. However, to date mesenchymal stem cells have not become a widely used therapeutic agent due to safety challenges, high cost and difficulties in providing long term production. A key mechanism underpinning the immunomodulatory effect of MSCs is the production of paracrine factors including growth factors, cytokines, chemokines, and extracellular vesicles (EVs). MSCs derived EVs have become an attractive therapeutic agent for immunomodulation and treatment of immune-mediated disorders. In addition to many preclinical studies of MSCs derived EVs, their beneficial effects have been observed in patients with both acute graft-vs.-host disease and chronic kidney disease. In this review, we discuss the current findings in the field of MSCs derived EVs-based therapies in immune-mediated disorders and approaches to scale EV production for clinical use.

Human bone marrow mesenchymal stem cell-derived extracellular vesicles attenuate neuroinflammation evoked by focal brain injury in rats

Background

Ischemic stroke is the major cause of long-term severe disability and death in aged population. Cell death in the infarcted region of the brain induces immune reaction leading to further progression of tissue damage. Immunomodulatory function of mesenchymal stem cells (MSCs) has been shown in multiple preclinical studies; however, it has not been successfully translated to a routine clinical practice due to logistical, economical, regulatory, and intellectual property obstacles. It has been recently demonstrated that therapeutic effect of intravenously administered MSCs can be recapitulated by extracellular vesicles (EVs) derived from them. However, in contrast to MSCs, EVs were not capable to decrease stroke-induced neuroinflammation. Therefore, the aim of the study was to investigate if intra-arterial delivery of MSC-derived EVs will have stronger impact on focal brain injury-induced neuroinflammation, which mimics ischemic stroke, and how it compares to MSCs.

Methods

The studies were performed in adult male Wistar rats with focal brain injury induced by injection of 1 μl of 50 nmol ouabain into the right hemisphere. Two days after brain insult, 5 × 10⁵ human bone marrow MSCs (hBM-MSCs) labeled with Molday ION or 1.3 × 10⁹ EVs stained with PKH26 were intra-arterially injected into the right hemisphere under real-time MRI guidance. At days 1, 3, and 7 post-transplantation, the rats were decapitated, the brains were removed, and the presence of donor cells or EVs was analyzed. The cellular immune response in host brain was evaluated immunohistochemically, and humoral factors were measured by multiplex immunoassay.

Results

hBM-MSCs and EVs transplanted intra-arterially were observed in the rat ipsilateral hemisphere, near the ischemic region. Immunohistochemical analysis of brain tissue showed that injection of hBM-MSCs or EVs leads to the decrease of cell activation by ischemic injury, i.e., astrocytes, microglia, and infiltrating leucocytes, including T cytotoxic cells. Furthermore, we observed significant decrease of pro-inflammatory cytokines and chemokines after hBM-MSC or EV infusion comparing with non-treated rats with focal brain injury.

Conclusions

Intra-arterially injected EVs attenuated neuroinflammation evoked by focal brain injury, which mimics ischemic stroke, and this effect was comparable to intra-arterial hBM-MSC transplantation. Thus, intra-arterial injection of EVs might be an attractive therapeutic approach, which obviates MSC-related obstacles.

Extracellular vesicles as a novel therapeutic tool for cell-free regenerative medicine in oral rehabilitation

Oral maxillofacial defects may always lead to complicated hard and soft tissue loss, including bone, nerve, blood vessels, teeth and skin, which are difficult to restore and severely influence the life quality of patients. Extracellular vesicles (EVs), including exosomes, microvesicles and apoptotic bodies, are emerging as potential solutions for complex tissue regeneration through cell-free therapies. In this review, we highlight the functional roles of EVs in the regenerative medicine for oral maxillofacial rehabilitation, specifically bone, skin, blood vessels, peripheral nerve and tooth-related tissue regeneration. Publications were reviewed by two researchers independently basing on three databases (PubMed, MEDLINE and Web of Science), until 31 December 2018. Basing on current researches, we classified the origin of EVs for regenerative medicine into four categories: related cells in the regenerative niche, mesenchymal stem cells, immune cells and body fluids. The secretome of different cells are distinct, while the same cells secrete different EVs under varied conditions; therefore, the content profiles of EVs and regulatory mechanisms on target cells are compared and emphasised. By unravelling the regulatory mechanisms of EVs in tissue regeneration, modified cells and tailored EVs with specific target may be produced for precision medicine with high efficacy.

Insights into the Role of MicroRNAs in the Onset and Development of Diabetic Neuropathy

Diabetic neuropathy is a serious complication of chronic hyperglycemia in diabetes patients. This complication can involve both peripheral sensorimotor and autonomic nervous system. The precise nature of injury to the peripheral nerves mediated by chronic hyperglycemia is unknown; however, several mechanisms have been proposed including polyol pathway activation, enhanced glycation of proteins and lipids, increased oxidative stress, and cytokine release in the site of injury. MicroRNAs (miRNAs) are small non-coding RNAs that mediate RNA interference by post-transcriptionally modulating gene expression and protein synthesis. Therefore, they have been implicated in several developmental, physiological, and pathophysiological processes where they modulate the expression of different proteins. Recently, miRNAs gained an increasing attention also for their role as diagnostic test in many diseases due to their stability in serum and their easy detection. Furthermore, recent studies suggest that miRNAs may be involved in diabetic neuropathy although their role in the onset and the development of this complication is not fully understood. In this review, we discuss the most recent literature providing evidence for miRNAs role in diabetic neuropathy opening new pathways to improve both early diagnosis and treatment of this complication.

Insights into the Secretome of Mesenchymal Stem Cells and Its Potential Applications

Mesenchymal stem cells (MSCs) have regenerative, immunoregulatory properties and can be easily isolated and expanded in vitro. Despite being a powerful tool for clinical applications, they present limitations in terms of delivery, safety, and variability of therapeutic response. Interestingly, the MSC secretome composed by cytokines, chemokines, growth factors, proteins, and extracellular vesicles, could represent a valid alternative to their use. It is noteworthy that MSC-derived extracellular vesicles (MSC-EVs) have the same effect and could be advantageous compared to the parental cells because of their specific miRNAs load. MiRNAs could be useful both in diagnostic procedures such as “liquid biopsy” to identify early pathologies and in the therapeutic field. Not only are MSC-EVs’ preservation, transfer, and production easier, but their administration is also safer, hence some clinical trials are ongoing. However, much effort is required to improve the characterization of EVs to avoid artifacts and guarantee reproducibility of the studies.

Mesenchymal stem versus stromal cells: International Society for Cell & Gene Therapy (ISCT®) Mesenchymal Stromal Cell committee position statement on nomenclature

The International Society for Cell & Gene Therapy (ISCT®) Mesenchymal Stromal Cell (ISCT MSC) committee offers a position statement to clarify the nomenclature of mesenchymal stromal cells (MSCs). The ISCT MSC committee continues to support the use of the acronym "MSCs" but recommends this be (i) supplemented by tissue-source origin of the cells, which would highlight tissue-specific properties; (ii) intended as MSCs unless rigorous evidence for stemness exists that can be supported by both in vitro and in vivo data; and (iii) associated with robust matrix of functional assays to demonstrate MSC properties, which are not generically defined but informed by the intended therapeutic mode of actions.

The potential of exosomes in the therapy of the cartilage and bone complications; emphasis on osteoarthritis

Osteoarthritis is a prevalent worldwide joint disease, which demonstrates a remarkable adverse effect on the patients' life modality. Medicinal agents, exclusively nonsteroidal anti-inflammatory drugs (NSAIDs), have been routinely applied in the clinic. But, their effects are restricted to pain control with insignificant effects on cartilage renovation, which would finally lead to cartilage destruction. In the field of regenerative medicine, many researchers have tried to use stem cells to repair tissues and other human organs. However, in recent years, with the discovery of extracellular microvesicles, especially exosomes, researchers have been able to offer more exciting alternatives on the subject. Exosomes and microvesicles are derived from different types of bone cells such as mesenchymal stem cells, osteoblasts, and osteoclasts. They are also recognized to play substantial roles in bone remodeling processes including osteogenesis, osteoclastogenesis, and angiogenesis. Specifically, exosomes derived from a mesenchymal stem cell have shown a great potential for the desired purpose. Exosomal products include miRNA, DNA, proteins, and other factors. At present, if it is possible to extract exosomes from various stem cells effectively and load certain products or drugs into them, they can be used in diseases, such as rheumatoid arthritis, osteoarthritis, bone fractures, and other diseases. Of course, to achieve proper clinical use, advances have to be made to establish a promising regenerative ability for microvesicles for treatment purposes in the orthopedic disorders. In this review, we describe the exosomes biogenesis and bone cell derived exosomes in the regenerate process of bone and cartilage remodeling.

The Immunomodulatory Functions of Mesenchymal Stromal/Stem Cells Mediated via Paracrine Activity

Mesenchymal stromal/stem cells (MSCs) exist in almost all tissues, possessing the potential to differentiate into specialized cell types and exert immunomodulatory functions. Thus, they have attracted much attention as a promising therapeutic candidate. Recent studies have demonstrated that paracrine signaling is mainly responsible for the involvement of MSCs in the modulation of immune responses and the progression of diseases. Through release of secretome consisting of a diverse range of cytokines, chemokines, and extracellular vesicles (EVs), MSCs convey regulatory messages to recipient immune cells in the microenvironment. In this review, we focus on the recent advances in how MSCs contribute to immunomodulation through the secretion of paracrine factors. The further improved understanding of the molecular mechanism underlying the interactions between MSCs and immune cells highlights the paracrine biology of MSCs in the modulation of the immune microenvironment and promotes the clinical application of MSCs in regenerative medicine and immune diseases.

Stem Cell-Derived Exosomes as Nanotherapeutics for Autoimmune and Neurodegenerative Disorders

To dissect therapeutic mechanisms of transplanted stem cells and develop exosome-based nanotherapeutics in treating autoimmune and neurodegenerative diseases, we assessed the effect of exosomes secreted from human mesenchymal stem cells (MSCs) in treating multiple sclerosis using an experimental autoimmune encephalomyelitis (EAE) mouse model. We found that intravenous administration of exosomes produced by MSCs stimulated by IFNγ (IFNγ-Exo) (i) reduced the mean clinical score of EAE mice compared to PBS control, (ii) reduced demyelination, (iii) decreased neuroinflammation, and (iv) upregulated the number of CD4+CD25+FOXP3+ regulatory T cells (Tregs) within the spinal cords of EAE mice. Co-culture of IFNγ-Exo with activated peripheral blood mononuclear cells (PBMCs) cells in vitro reduced PBMC proliferation and levels of pro-inflammatory Th1 and Th17 cytokines including IL-6, IL-12p70, IL-17AF, and IL-22 yet increased levels of immunosuppressive cytokine indoleamine 2,3-dioxygenase. IFNγ-Exo could also induce Tregs in vitro in a murine splenocyte culture, likely mediated by a third-party accessory cell type. Further, IFNγ-Exo characterization by deep RNA sequencing suggested that IFNγ-Exo contains anti-inflammatory RNAs, where their inactivation partially hindered the exosomes potential to induce Tregs. Furthermore, we found that IFNγ-Exo harbors multiple anti-inflammatory and neuroprotective proteins. These results not only shed light on stem cell therapeutic mechanisms but also provide evidence that MSC-derived exosomes can potentially serve as cell-free therapies in creating a tolerogenic immune response to treat autoimmune and central nervous system disorders.

The Necrobiology of Mesenchymal Stromal Cells Affects Therapeutic Efficacy

Rapid progress is occurring in understanding the mechanisms underlying mesenchymal stromal cell (MSC)-based cell therapies (MSCT). However, the results of clinical trials, while demonstrating safety, have been varied in regard to efficacy. Recent data from different groups have shown profound and significant influences of the host inflammatory environment on MSCs delivered systemically or through organ-specific routes, for example intratracheal, with subsequent actions on potential MSC efficacies. Intriguingly in some models, it appears that dead or dying cells or subcellular particles derived from them, may contribute to therapeutic efficacy, at least in some circumstances. Thus, the broad cellular changes that accompany MSC death, autophagy, pre-apoptotic function, or indeed the host response to these processes may be essential to therapeutic efficacy. In this review, we summarize the existing literature concerning the necrobiology of MSCs and the available evidence that MSCs undergo autophagy, apoptosis, transfer mitochondria, or release subcellular particles with effector function in pathologic or inflammatory in vivo environments. Advances in understanding the role of immune effector cells in cell therapy, especially macrophages, suggest that the reprogramming of immunity associated with MSCT has a weighty influence on therapeutic efficacy. If correct, these data suggest novel approaches to enhancing the beneficial actions of MSCs that will vary with the inflammatory nature of different disease targets and may influence the choice between autologous or allogeneic or even xenogeneic cells as therapeutics.

Emerging Role of Mesenchymal Stromal Cell-Derived Extracellular Vesicles in Pathogenesis of Haematological Malignancies

Homoeostasis of bone marrow microenvironment depends on a precise balance between cell proliferation and death, which is supported by the cellular-extracellular matrix crosstalk. Multipotent mesenchymal stromal cells (MSC) are the key elements to provide the specialized bone marrow microenvironment by supporting, maintaining, and regulating the functions and fate of haematopoietic stem cells. Despite the great potential of MSC for cell therapy in several diseases due to their regenerative, immunomodulatory, and anti-inflammatory properties, they can also contribute to modulate tumor microenvironment. The extracellular vesicles that comprise exosomes and microvesicles are important mediators of intercellular communication due to their ability to change phenotype and physiology of different cell types. These vesicles may interact not only with neighbouring cells but also with cells from distant tissues to either maintain tissue homoeostasis or participate in disease pathogenesis. This review focuses on the current knowledge about the physiological role of MSC-extracellular vesicles, as well as their deregulation in haematological malignancies and their potential applications as biomarkers for diagnosis, progression, and treatment monitoring of such diseases.

Extracellular vesicles from regenerative human cardiac cells act as potent immune modulators by priming monocytes

Background

Nano-sized vesicles, so called extracellular vesicles (EVs), from regenerative cardiac cells represent a promising new therapeutic approach to treat cardiovascular diseases. However, it is not yet sufficiently understood how cardiac-derived EVs facilitate their protective effects. Therefore, we investigated the immune modulating capabilities of EVs from human cardiac-derived adherent proliferating (CardAP) cells, which are a unique cell type with proven cardioprotective features.

Results

Differential centrifugation was used to isolate EVs from conditioned medium of unstimulated or cytokine-stimulated (IFNγ, TNFα, IL-1β) CardAP cells. The derived EVs exhibited typical EV-enriched proteins, such as tetraspanins, and diameters mostly of exosomes (< 100 nm). The cytokine stimulation caused CardAP cells to release smaller EVs with a lower integrin ß1 surface expression, while the concentration between both CardAP-EV variants was unaffected. An exposure of either CardAP-EV variant to unstimulated human peripheral blood mononuclear cells (PBMCs) did not induce any T cell proliferation, which indicates a general low immunogenicity. In order to evaluate immune modulating properties, PBMC cultures were stimulated with either Phytohemagglutin or anti-CD3. The treatment of those PBMC cultures with either CardAP-EV variant led to a significant reduction of T cell proliferation, pro-inflammatory cytokine release (IFNγ, TNFα) and increased levels of active TGFβ. Further investigations identified CD14⁺ cells as major recipient cell subset of CardAP–EVs. This interaction caused a significant lower surface expression of HLA-DR, CD86, and increased expression levels of CD206 and PD-L1. Additionally, EV-primed CD14⁺ cells released significantly more IL-1RA. Notably, CardAP-EVs failed to modulate anti-CD3 triggered T cell proliferation and pro-inflammatory cytokine release in monocultures of purified CD3⁺ T cells. Subsequently, the immunosuppressive feature of CardAP-EVs was restored when anti-CD3 stimulated purified CD3⁺ T cells were co-cultured with EV-primed CD14⁺ cells. Beside attenuated T cell proliferation, those cultures also exhibited a significant increased proportion of regulatory T cells.

Conclusions

CardAP-EVs have useful characteristics that could contribute to enhanced regeneration in damaged cardiac tissue by limiting unwanted inflammatory processes. It was shown that the priming of CD14⁺ immune cells by CardAP-EVs towards a regulatory type is an essential step to attenuate significantly T cell proliferation and pro-inflammatory cytokine release in vitro.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0504-0) contains supplementary material, which is available to authorized users.

Role of extracellular vesicles in stem cell biology

The extracellular vesicles (EVs) are membrane vesicles carrying proteins, nucleic acids, and bioactive lipids of the cell of origin. These vesicles released within the extracellular space and entering into the circulation may transfer their cargo to neighboring or distant cells and induce phenotypical and functional changes that may be relevant in several physiopathological conditions. In an attempt to define the biological properties of EVs, several investigations have focused on their cargo and on the effects elicited in recipient cells. EVs have been involved in modulation of tumor microenvironment and behavior, as well as in the immune and inflammatory response. In the present review, we address the paracrine action of EVs released by stem cells and their potential involvement in the activation of regenerative programs in injured cells.

Breast Cancer Tumor Stroma: Cellular Components, Phenotypic Heterogeneity, Intercellular Communication, Prognostic Implications and Therapeutic Opportunities

Although the mechanisms underlying the genesis and progression of breast cancer are better understood than ever, it is still the most frequent malignant tumor in women and one of the leading causes of cancer death. Therefore, we need to establish new approaches that lead us to better understand the prognosis of this heterogeneous systemic disease and to propose new therapeutic strategies. Cancer is not only a malignant transformation of the epithelial cells merely based on their autonomous or acquired proliferative capacity. Today, data support the concept of cancer as an ecosystem based on a cellular sociology, with diverse components and complex interactions between them. Among the different cell types that make up the stroma, which have a relevant role in the dynamics of tumor/stromal cell interactions, the main ones are cancer associated fibroblasts, endothelial cells, immune cells and mesenchymal stromal cells. Several factors expressed by the stroma of breast carcinomas are associated with the development of metastasis, such as matrix metalloproteases, their tissular inhibitors or some of their regulators like integrins, cytokines or toll-like receptors. Based on the expression of these factors, two types of breast cancer stroma can be proposed with significantly different influence on the prognosis of patients. In addition, there is evidence about the existence of bi-directional signals between cancer cells and tumor stroma cells with prognostic implications, suggesting new therapeutic strategies in breast cancer.

Exosomes from Human Gingiva-Derived Mesenchymal Stem Cells Combined with Biodegradable Chitin Conduits Promote Rat Sciatic Nerve Regeneration

At present, repair methods for peripheral nerve injury often fail to get satisfactory result. Although various strategies have been adopted to investigate the microenvironment after peripheral nerve injury, the underlying molecular mechanisms of neurite outgrowth remain unclear. In this study, we evaluate the effects of exosomes from gingival mesenchymal stem cells (GMSCs) combined with biodegradable chitin conduits on peripheral nerve regeneration. GMSCs were isolated from human gingival tissue and characterized by surface antigen analysis and in vitro multipotent differentiation. The cell supernatant was collected to isolate the exosomes. The exosomes were characterized by transmission electron microscopy, Western blot, and size distribution analysis. The effects of exosomes on peripheral nerve regeneration in vitro were evaluated by coculture with Schwann cells and DRGs. The chitin conduit was prepared and combined with the exosomes to repair rat sciatic nerve defect. Histology, electrophysiology, and gait analysis were used to test the effects of exosomes on sciatic nerve function recovery in vivo. We have successfully cultured GMSCs and isolated exosomes. The exosomes from GMSCs could significantly promote Schwann cell proliferation and DRG axon growth. The in vivo studies showed that chitin conduit combined with exosomes from GMSCs could significantly increase the number and diameter of nerve fibers and promote myelin formation. In addition, muscle function, nerve conduction function, and motor function were also obviously recovered. In summary, this study suggests that GMSC-derived exosomes combined with biodegradable chitin conduits are a useful and novel therapeutic intervention in peripheral nerve repair.

Extracellular vesicles from human umbilical cord mesenchymal stem cells improve nerve regeneration after sciatic nerve transection in rats

Peripheral nerve injury results in limited nerve regeneration and severe functional impairment. Mesenchymal stem cells (MSCs) are a remarkable tool for peripheral nerve regeneration. The involvement of human umbilical cord MSC-derived extracellular vesicles (hUCMSC-EVs) in peripheral nerve regeneration, however, remains unknown. In this study, we evaluated functional recovery and nerve regeneration in rats that received hUCMSC-EV treatment after nerve transection. We observed that hUCMSC-EV treatment promoted the recovery of motor function and the regeneration of axons; increased the sciatic functional index; resulted in the generation of numerous axons and of several Schwann cells that surrounded individual axons; and attenuated the atrophy of the gastrocnemius muscle. hUCMSC-EVs aggregated to rat nerve defects, down-regulated interleukin (IL)-6 and IL-1β, up-regulated IL-10 and modulated inflammation in the injured nerve. These effects likely contributed to the promotion of nerve regeneration. Our findings indicate that hUCMSC-EVs can improve functional recovery and nerve regeneration by providing a favourable microenvironment for nerve regeneration. Thus, hUCMSC-EVs have considerable potential for application in the treatment of peripheral nerve injury.

EP4 Antagonist-Elicited Extracellular Vesicles from Mesenchymal Stem Cells Rescue Cognition/Learning Deficiencies by Restoring Brain Cellular Functions

Adult brains have limited regenerative capacity. Consequently, both brain damage and neurodegenerative diseases often cause functional impairment for patients. Mesenchymal stem cells (MSCs), one type of adult stem cells, can be isolated from various adult tissues. MSCs have been used in clinical trials to treat human diseases and the therapeutic potentials of the MSC‐derived secretome and extracellular vesicles (EVs) have been under investigation. We found that blocking the prostaglandin E₂/prostaglandin E₂ receptor 4 (PGE₂/EP₄) signaling pathway in MSCs with EP₄ antagonists increased EV release and promoted the sorting of specific proteins, including anti‐inflammatory cytokines and factors that modify astrocyte function, blood–brain barrier integrity, and microglial migration into the damaged hippocampus, into the EVs. Systemic administration of EP₄ antagonist‐elicited MSC EVs repaired deficiencies of cognition, learning and memory, inhibited reactive astrogliosis, attenuated extensive inflammation, reduced microglial infiltration into the damaged hippocampus, and increased blood–brain barrier integrity when administered to mice following hippocampal damage. stem cells translational medicine2019

Novel insights into MSC-EVs therapy for immune diseases

Mesenchymal stromal cells (MSC) are a heterogeneous cell population with self-renewal and the ability to differentiate into different lineages. The novel regulatory role of MSC in both adaptive and innate immune responses got extensive investigation and MSC have been widely used in clinical trials as immunosuppressive agents for autoimmune and inflammatory diseases, including graft-versus-host disease (GVHD), multiple sclerosis (MS), systemic lupus erythematosus (SLE), chronic kidney disease, etc. Recent studies have found that MSC exerted their immunomodulation function through secreting extracellular vesicles (EVs), which delivered parent cell cargo to recipient cells without oncogenicity or variability. Since MSC-EVs exhibit most of the properties of MSC and take advantage of their cellular immunomodulatory fuction, MSC-EVs appear to a promising none-cell therapy in various human diseases. In this review, we summarize the pivotal roles of MSC-EVs as agents for immunotherapy in diseases.

Therapeutic Potential of Extracellular Vesicles for the Treatment of Nerve Disorders

The use of extracellular vesicles (EVs) as cell free therapy is a promising approach to stimulate tissue regeneration including that of the nervous system. EVs transfer bioactive proteins and lipids, RNA and microRNAs, which play a relevant role in EV-mediated intercellular communication. The immunomodulatory, anti-inflammatory, and neuroprotective effects of mesenchymal stem cells-derived EVs have been well studied, knowledge of this paracrine mechanism and the availability of these cells, positions mesenchymal stem cells as a potential source of EVs for cell free therapy for a variety of regenerative and nervous system disorders. In this review, we focus on the immunomodulatory and neuroprotective effects of stem cells-derived EVs within in vitro and in vivo models of nerve disorders.

Stem Cell-Derived Extracellular Vesicles as Immunomodulatory Therapeutics

Mesenchymal stem cells (MSCs) have been reported to possess regulatory functions on immune cells which make them alternative therapeutics for the treatment of inflammatory and autoimmune diseases. The interaction between MSCs and immune cells through paracrine factors might be crucial for these immunomodulatory effects of MSCs. Extracellular vesicles (EVs) are defined as bilayer membrane structures including exosomes and microvesicles which contain bioactive paracrine molecules affecting the characteristics of target cells. Recently, several studies have revealed that EVs derived from MSCs (MSC-EVs) can reproduce similar therapeutic impacts of parent MSCs; MSC-EVs could regulate proliferation, maturation, polarization, and migration of various immune effector cells and modulate the immune microenvironment depending on the context by delivering inflammatory cytokines, transcription factors, and microRNAs. Therefore, MSC-EVs can be applied as novel and promising tools for the treatment of immune-related disorders to overcome the limitations of conventional cell therapy regarding efficacy and toxicity issues. In this review, we will discuss current insights regarding the major outcomes in the evaluation of MSC-EV function against inflammatory disease models, as well as immune cells.

Extracellular Vesicles from Wharton's Jelly Mesenchymal Stem Cells Suppress CD4 Expressing T Cells Through Transforming Growth Factor Beta and Adenosine Signaling in a Canine Model

Mesenchymal stem cells (MSCs) are widely investigated as potential therapeutic agents due to their potent immunomodulatory capacity. Although specific mechanisms by which MSC acts on immune cells are emerging, many questions remain, including the potential of extracellular vesicles (EVs) to mediate biological activities. Canine MSCs are of interest for both veterinary and comparative models of disease and have been shown to suppress CD4^pos T cell proliferation. The aim of this study was to determine whether EV isolated from canine Wharton's jelly-derived MSC (WJ-MSC EV) suppresses CD4^pos T cell proliferation using biochemical mechanisms previously ascribed to soluble mediators [transforming growth factor beta (TGF-β) and adenosine]. WJ-MSC EV exhibited mode of 125 nm diameter, low buoyant density (1.1 g/mL), and expression of EV proteins Alix and TSG101. Functionally, EVs inhibited CD4^pos T cell proliferation in a dose-dependent manner, which was absent in EV-depleted samples and EVs from non-MSC fibroblasts. EV suppression of CD4^pos T cell proliferation was inhibited by a TGF-βRI antagonist, neutralizing antibodies to TGF-β, or A2A adenosine receptor blockade. TGF-β was present on EVs as latent complexes most likely tethered to EV membrane by betaglycan. These data demonstrate that canine WJ-MSC EV utilizes TGF-β and adenosine signaling to suppress proliferation of CD4^pos T cell and will enable further investigation into mechanisms of immune cell modulation, as well as refinement of WJ-MSC and their EVs for therapeutic application.

Mesenchymal stem cell-based therapy for autoimmune diseases: emerging roles of extracellular vesicles

In autoimmune disease body's own immune system knows healthy cells as undesired and foreign cells. Over 80 types of autoimmune diseases have been recognized. Currently, at clinical practice, treatment strategies for autoimmune disorders are based on relieving symptoms and preventing difficulties. In other words, there is no effective and useful therapy up to now. It has been well-known that mesenchymal stem cells (MSCs) possess immunomodulatory effects. This strongly suggests that MSCs might be as a novel modality for treatment of autoimmune diseases. Supporting this notion a few preclinical and clinical studies indicate that MSCs ameliorate autoimmune disorders. Interestingly, it has been found that the beneficial effects of MSCs in autoimmune disorders are not relying only on direct cell-to-cell communication but on their capability to produce a broad range of paracrine factors including growth factors, cytokines and extracellular vehicles (EVs). EVs are multi-signal messengers that play a serious role in intercellular signaling through carrying cargo such as mRNA, miRNA, and proteins. Numerous studies have shown that MSC-derived EVs are able to mimic the effects of the cell of origin on immune cells. In this review, we discuss the current studies dealing with MSC-based therapies in autoimmune diseases and provide a vision and highlight in order to introduce MSC-derived EVs as an alternative and emerging modality for autoimmune disorders.

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

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

Intratracheal administration of clinical-grade mesenchymal stem cell-derived extracellular vesicles reduces lung injury in a rat model of bronchopulmonary dysplasia

Mesenchymal stem cells (MSCs) prevent the onset of bronchopulmonary dysplasia (BPD) in animal models, an effect that seems to be mediated by their secreted extracellular vesicles (EVs). The aim of this study was to compare the protective effects of intratracheally (IT) administered MSCs versus MSC-EVs in a hyperoxia-induced rat model of BPD. At birth, rats were distributed as follows: animals raised in ambient air for 2 wk ( n = 10), and animals exposed to 60% oxygen for 2 wk and treated with IT-administered physiological solution ( n = 10), MSCs ( n = 10), or MSC-EVs ( n = 10) on postnatal days 3, 7, and 10. The sham-treated hyperoxia-exposed animals showed reductions in total surface area of alveolar air spaces, and total number of alveoli ( Nalv), and an increased mean alveolar volume (Valv). EVs prompted a significant increase in Nalv ( P < 0.01) and a significant decrease in Valv ( P < 0.05) compared with sham-treated animals, whereas MSCs only significantly improved Nalv ( P < 0.05). Small pulmonary vessels of the sham-treated hyperoxia-exposed rats also showed an increase in medial thickness, which only EVs succeeded in preventing significantly ( P < 0.05). In conclusion, both EVs and MSCs reduce hyperoxia-induced damage, with EVs obtaining better results in terms of alveolarization and lung vascularization parameters. This suggests that IT-administered EVs could be an effective approach to BPD treatment.

Mesenchymal Stromal Cell-Derived Exosomes Affect mRNA Expression and Function of B-Lymphocytes

Background: Bone marrow mesenchymal stem cells (bmMSC) may play a role in the regulation of maturation, proliferation, and functional activation of lymphocytes, though the exact mechanisms are unknown. MSC-derived exosomes induce a regulatory response in the function of B, T, and monocyte-derived dendritic cells. Here, we evaluated the specific inhibition of human lymphocytes by bmMSC-derived exosomes and the effects on B-cell function.

Methods: Exosomes were isolated from culture media of bmMSC obtained from several healthy donors. The effect of purified bmMSC-derived exosomes on activated peripheral blood mononuclear cells (PBMCs) and isolated B and T lymphocyte proliferation was measured by carboxyfluorescein succinimidyl ester assay. Using the Illumina sequencing platform, mRNA profiling was performed on B-lymphocytes activated in the presence or absence of exosomes. Ingenuity® pathway analysis software was applied to analyze pathway networks, and biological functions of the differentially expressed genes. Validation by RT-PCR was performed. The effect of bmMSC-derived exosomes on antibody secretion was measured by ELISA.

Results: Proliferation of activated PBMCs or isolated T and B cells co-cultured with MSC-derived exosomes decreased by 37, 23, and 18%, respectively, compared to controls. mRNA profiling of activated B-lymphocytes revealed 186 genes that were differentially expressed between exosome-treated and control cells. We observed down- and up-regulation of genes that are involved in cell trafficking, development, hemostasis, and immune cell function. RNA-Seq results were validated by real time PCR analysis for the expression of CXCL8 (IL8) and MZB1 genes that are known to have an important role in immune modulation. Functional alterations were confirmed by decreased IgM production levels. Consistent results were demonstrated among a wide variety of healthy human bmMSC donors.

Conclusion: Our data show that exosomes may play an important role in immune regulation. They inhibit proliferation of several types of immune cells. In B-lymphocytes they modulate cell function by exerting differential expression of the mRNA of relevant genes. The results of this study help elucidate the mechanisms by which exosomes induce immune regulation and may contribute to the development of newer and safer therapeutic strategies.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles Attenuate Dendritic Cell Maturation and Function

Mesenchymal stromal cells (MSCs) are potent regulators of immune responses largely through paracrine signaling. MSC secreted extracellular vesicles (MSC-EVs) are increasingly recognized as the key paracrine factors responsible for the biological and therapeutic function of MSCs. We report the first comprehensive study demonstrating the immunomodulatory effect of MSC-EVs on dendritic cell (DC) maturation and function. MSC-EVs were isolated from MSC conditioned media using differential ultracentrifugation. Human monocyte-derived DCs were generated in the absence or presence of MSC-EVs (20 ug/ml) then subjected to phenotypic and functional analysis in vitro. MSC-EV treatment impaired antigen uptake by immature DCs and halted DC maturation resulting in reduced expression of the maturation and activation markers CD83, CD38, and CD80, decreased secretion of pro-inflammatory cytokines IL-6 and IL-12p70 and increased production of anti-inflammatory cytokine TGF-β. MSC-EV treated DCs also demonstrated a diminished CCR 7 expression after LPS stimulation, coupled with a significantly reduced ability to migrate toward the CCR7-ligand CCL21, although they were still able to stimulate allogeneic T cell proliferation in vitro. Through microRNA profiling we have identified 49 microRNAs, which were significantly enriched in MSC-EVs compared to their parent MSCs. MicroRNAs with known effect on DC maturation and functions, including miR-21-5p, miR-142-3p, miR-223-3p, and miR-126-3p, were detected within the top 10 most enriched miRNAs in MSC-EVs, with MiR-21-5p as the third highest expressed miRNA in MSC-EVs. In silico analysis revealed that miR-21-5p targets the CCR7 gene for degradation. To verify these observations, DCs were transfected with miR-21-5p mimics and analyzed for their ability to migrate toward the CCR7-ligand CCL21 in vitro. MiR-21-5p mimic transfected DCs showed a clear trend of reduced CCR7 expression and a significantly decreased migratory ability toward the CCL21. Our findings suggest that MSC-EVs are able to recapitulate MSC mediated DC modulation and MSC-EV enclosed microRNAs may represent a novel mechanism through which MSCs modulate DC functions. As MSCs are currently used in clinical trials to treat numerous diseases associated with immune dysregulation, such as graft-versus-host disease and inflammatory bowel disease, our data provide novel evidence to inform potential future application of MSC-EVs as a cell-free therapeutic agent.

Pilot Production of Mesenchymal Stem/Stromal Freeze-Dried Secretome for Cell-Free Regenerative Nanomedicine: A Validated GMP-Compliant Process

In this paper, a pilot production process for mesenchymal stem/stromal freeze-dried secretome was performed in a validated good manufacturing practice (GMP)-compliant cell factory. Secretome was purified from culture supernatants by ultrafiltration, added to cryoprotectant, lyophilized and characterized. We obtained a freeze-dried, "ready-off-the-shelf" and free soluble powder containing extracellular vesicles and proteins. In the freeze-dried product, a not-aggregated population of extracellular vesicles was detected by nanoparticle tracking analysis; Fourier transform infrared spectra showed the simultaneous presence of protein and lipids, while differential scanning calorimetry demonstrated that lyophilization process successfully occurred. A proteomic characterization allowed the identification of proteins involved in immune response, response to stress, cytoskeleton and metabolism. Moreover, the product was not cytotoxic up to concentrations of 25 mg/mL (on human fibroblasts, chondrocytes and nucleus pulposus cells by MTT assay) and was blood compatible up to 150 mg/mL. Finally, at concentrations between 5 and 50 mg/mL, freeze-dried secretome showed to in vitro counteract the oxidative stress damage induced by H₂O₂ on nucleus pulposus cells by MTT assay.

Interaction between mesenchymal stromal cell-derived extracellular vesicles and immune cells by distinct protein content

Mesenchymal stromal cells (MSCs) can effectively contribute to tissue regeneration inside the inflammatory microenvironment mostly through modulating immune responses. MSC-derived extracellular vesicles (MSC-EVs) display immunoregulatory functions similar to parent cells. Interactions between MSC-EVs and immune cells make them an ideal therapeutic candidate for infectious, inflammatory, and autoimmune diseases. These properties of MSC-EVs have encouraged researchers to perform extensive studies on multiple factors that mediate MSC-EVs immunomodulatory effects. Investigation of proteins involved in the complex interplay of MSC-EVs and immune cells may help us to better understand their functions. Here, we performed a comprehensive proteomic analysis of MSC-EVs that was previously reported by ExoCarta database. A total of 938 proteins were identified as MSC-EV proteome using quantitative proteomics techniques. Kyoto Encyclopedia of Genes and Genomes analysis demonstrates that ECM-receptor interaction, focal adhesion, and disease-specific pathways are enriched in MSC-EVs. By detail analysis of proteins presence in immune system process, we found that expression of some cytokines, chemokines, and chemokine receptors such as IL10, HGF, LIF, CCL2, VEGFC, and CCL20, which leads to migration of MSC-EVs to injured sites, suppression of inflammation and promotion of regeneration in inflammatory and autoimmune diseases. Also, some chemoattractant proteins such as CXCL2, CXCL8, CXCL16, DEFA1, HERC5, and IFITM2 were found in MSC-EV proteome. They may actively recruit immune cells to the proximity of MSC or MSC-EVs, may result in boosting immune response under specific circumstances, and may have protective role in infectious diseases. In this review, we summarize available information about immunomodulation of MSC-EVs with particular emphasis on their proteomics analysis.

To Protect and to Preserve: Novel Preservation Strategies for Extracellular Vesicles

Extracellular vesicles (EVs)-based therapeutics are based on the premise that EVs shed by stem cells exert similar therapeutic effects and these have been proposed as an alternative to cell therapies. EV-mediated delivery is an effective and efficient system of cell-to-cell communication which can confer therapeutic benefits to their target cells. EVs have been shown to promote tissue repair and regeneration in various animal models such as, wound healing, cardiac ischemia, diabetes, lung fibrosis, kidney injury, and many others. Given the unique attributes of EVs, considerable thought must be given to the preservation, formulation and cold chain strategies in order to effectively translate exciting preclinical observations to clinical and commercial success. This review summarizes current understanding around EV preservation, challenges in maintaining EV quality, and also bioengineering advances aimed at enhancing the long-term stability of EVs.

Exosomes in perspective: a potential surrogate for stem cell therapy

Exosomes as a unique subtype of small extracellular vesicles (sEVs) have attracted increasing interest in recent years in the fields of mesenchymal stromal cell (MSC) research. Studies have confirmed that exosomes derived from MSCs preserve immunosuppressive phenotype and can mimic therapeutic benefits of their parent cells. This review briefly summarizes most recent findings on the potential of exosomes as an alternative of therapeutic MSCs, focusing on the role of MSCs and their secreted exosomes in regulation of immune cells, preclinical and clinical evidence of therapeutic outcomes of MSC exosomes, and the biodistribution and pharmacokinetic profile of systemically administered exosomes. It is appreciated that exosomes from MSCs of different sources have variable contents including inflammatory mediators, tropic factors, signaling molecules, and nucleic acids (DNA, mRNA, microRNA and long non-coding RNA). Diverse functions of exosomes derived from different sources are expected. More importantly, exosomes isolated in vitro may not mirror that from in vivo, where donor MSCs are exposed to specific disease or injury-related conditions. Simulating in vivo microenvironment by pretreatment of MSCs with relevant chemical mediators may lead to their secretion of therapeutically more efficient exosomes/sEVs. However, we know very little about the key molecules involved and the differences between exosomes released under different conditions. These issues would be of tremendous interest to preclinical research that pursues exosome biology-underlain therapeutic mechanisms of MSCs. Further studies are expected to demonstrate the superiority of MSC-derived exsomes/sEVs as a pharmaceutical entity with regard to efficacy, safety, and practicability.