Mesenchymal stem cells protect from acute liver injury by attenuating hepatotoxicity of liver natural killer T cells in an inducible nitric oxide synthase- and indoleamine 2,3-dioxygenase-dependent manner

Immunomodulatory effects and clinical application of exosomes derived from mesenchymal stem cells

Exosomes (Exos) are extracellular vesicles secreted by cells and serve as crucial mediators of intercellular communication. They play a pivotal role in the pathogenesis and progression of various diseases and offer promising avenues for therapeutic interventions. Exos derived from mesenchymal stem cells (MSCs) have significant immunomodulatory properties. They effectively regulate immune responses by modulating both innate and adaptive immunity. These Exos can inhibit excessive inflammatory responses and promote tissue repair. Moreover, they participate in antigen presentation, which is essential for activating immune responses. The cargo of these Exos, including ligands, proteins, and microRNAs, can suppress T cell activity or enhance the population of immunosuppressive cells to dampen the immune response. By inhibiting lymphocyte proliferation, acting on macrophages, and increasing the population of regulatory T cells, these Exos contribute to maintaining immune and metabolic homeostasis. Furthermore, they can activate immune-related signaling pathways or serve as vehicles to deliver microRNAs and other bioactive substances to target tumor cells, which holds potential for immunotherapy applications. Given the immense therapeutic potential of MSC-derived Exos, this review comprehensively explores their mechanisms of immune regulation and therapeutic applications in areas such as infection control, tumor suppression, and autoimmune disease management. This article aims to provide valuable insights into the mechanisms behind the actions of MSC-derived Exos, offering theoretical references for their future clinical utilization as cell-free drug preparations.

Trapa natans L. Extract Attenuates Inflammation and Oxidative Damage in Cisplatin-Induced Cardiotoxicity in Rats by Promoting M2 Macrophage Polarization

Background: Trapa natans L. fruits and leaf extracts have a broad range of immunomodulatory, anti-inflammatory, and antioxidant effects; however, their effects on cardiac protection have not been investigated. Objective: The study aims to test the biological activity of Trapa natans L. extract (TNE) in cisplatin (CDDP)-induced cardiotoxicity. Methods: Wistar albino rats received a single dose of CDDP intraperitoneally and TNE ones per day for 2 weeks orally. Cardiac inflammation, necrosis, and fibrosis were determined by histological and immunohistochemical analyses. Cytokines in rat sera and cardiac tissue were detected by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time (qRT)-PCR. Rat macrophages cultured in the presence of TNE for 48 h were harvested for flow cytometry, while supernatants were collected for cytokine and reactive oxygen species (ROS) measurement. Results: Application of TNE significantly attenuated CDDP induced cardiotoxicity as demonstrated by biochemical and histopathological analysis. Administration of TNE once daily for 14 days decreased level of proinflammatory (TNF-α, IFN-γ, and IL-6) and prooxidative parameters (NO2, O2, and H2O2), while increased level of immunosuppressive IL-10 and antioxidative glutathione (GSH), catalase (CAT) and uperoxide dismutase (SOD) in the systemic circulation. TNE treatment resulted in attenuated heart inflammation and fibrosis accompanied with the reduced infiltration of macrophages and reduced expression of proinflammatory and profibrotic genes in heart tissue of CDDP-treated animals. In vitro lipopolysaccharide (LPS)-stimulated macrophages cultured in the presence of TNE adopted immunosuppressive phenotype characterized by decreased production of proinflammatory cytokines and prooxidative mediators. Conclusion: Our study provides the evidence that TNE ameliorates cisplatin-induced cardiotoxicity in rats by reducing inflammation and oxidative stress via promoting M2 macrophage polarization.

Cell therapy for end-stage liver disease: Current state and clinical challenge

ABSTRACT

Liver disease involves a complex interplay of pathological processes, including inflammation, hepatocyte necrosis, and fibrosis. End-stage liver disease (ESLD), such as liver failure and decompensated cirrhosis, has a high mortality rate, and liver transplantation is the only effective treatment. However, to overcome problems such as the shortage of donor livers and complications related to immunosuppression, there is an urgent need for new treatment strategies that need to be developed for patients with ESLD. For instance, hepatocytes derived from donor livers or stem cells can be engrafted and multiplied in the liver, substituting the host hepatocytes and rebuilding the liver parenchyma. Stem cell therapy, especially mesenchymal stem cell therapy, has been widely proved to restore liver function and alleviate liver injury in patients with severe liver disease, which has contributed to the clinical application of cell therapy. In this review, we discussed the types of cells used to treat ESLD and their therapeutic mechanisms. We also summarized the progress of clinical trials around the world and provided a perspective on cell therapy.

Stimuli-Responsive Substrates to Control the Immunomodulatory Potential of Stromal Cells

Mesenchymal stromal cells (MSCs) have broad immunomodulatory properties that range from regulation, proliferation, differentiation, and immune cell activation to secreting bioactive molecules that inhibit inflammation and regulate immune response. These properties provide MSCs with high therapeutic potency that has been shown to be relevant to tissue engineering and regenerative medicine. Hence, researchers have explored diverse strategies to control the immunomodulatory potential of stromal cells using polymeric substrates or scaffolds. These substrates alter the immunomodulatory response of MSCs, especially through biophysical cues such as matrix mechanical properties. To leverage these cell-matrix interactions as a strategy for priming MSCs, emerging studies have explored the use of stimuli-responsive substrates to enhance the therapeutic value of stromal cells. This review highlights how stimuli-responsive materials, including chemo-responsive, microenvironment-responsive, magneto-responsive, mechano-responsive, and photo-responsive substrates, have specifically been used to promote the immunomodulatory potential of stromal cells by controlling their secretory activity.

Stem Cell Secretions as a Potential Therapeutic Agent for Autism Spectrum Disorder: A Narrative Review

Autism spectrum disorder (ASD) is a neurodevelopmental illness characterized by impaired social interaction and restricted repetitive behaviors or interests. The rising prevalence of ASD diagnosis has triggered a surge in research into investigating the underlying neuropathological processes and finding new therapeutic approaches. ASD is characterized by neuroinflammation and dysregulation of neuro-immune cross-talk, which suggests that stem cell treatment might be a potential therapeutic approach. The beneficial and restorative effects of stem cells are mainly due to their paracrine activity, in which stem cells generate and release extracellular vesicles such as exosomes and distinct secreted non-vesicle soluble proteins, including, growth factors, chemokines, cytokines, and immunomodulatory molecules referred to as the Secretome. In this paper, we reviewed the existing research exploring the therapeutic potential of stem cell secretome focusing on their role in addressing ASD pathology. Furthermore, we proposed a comprehensive mechanism of action for stem cell secretions, encompassing the broader secretome as well as the specific contribution of exosomes, in alleviating ASD neuropathology. Across the reviewed studies, exosomes and secreted soluble factors of the transplanted stem cell demonstrate a potential efficacy in ameliorating autistic-like behaviors. The proposed mechanism of action involves the modulation of signaling pathways implicated in neuroinflammation, angiogenesis, cellular apoptosis, and immunomodulation.

Stem Cell-Based Strategies: The Future Direction of Bioartificial Liver Development

Acute liver failure (ALF) results from severe liver damage or end-stage liver disease. It is extremely fatal and causes serious health and economic burdens worldwide. Once ALF occurs, liver transplantation (LT) is the only definitive and recommended treatment; however, LT is limited by the scarcity of liver grafts. Consequently, the clinical use of bioartificial liver (BAL) has been proposed as a treatment strategy for ALF. Human primary hepatocytes are an ideal cell source for these methods. However, their high demand and superior viability prevent their widespread use. Hence, finding alternatives that meet the seed cell quality and quantity requirements is imperative. Stem cells with self-renewing, immunogenic, and differentiative capacities are potential cell sources. MSCs and its secretomes encompass a spectrum of beneficial properties, such as anti-inflammatory, immunomodulatory, anti-ROS (reactive oxygen species), anti-apoptotic, pro-metabolomic, anti-fibrogenesis, and pro-regenerative attributes. This review focused on the recent status and future directions of stem cell-based strategies in BAL for ALF. Additionally, we discussed the opportunities and challenges associated with promoting such strategies for clinical applications.

Human placental mesenchymal stromal cells modulate IFN-γ and IL-10 secretion by CD4+T cells via CD73, and alleviate intestinal damage in mice with graft-versus-host disease

BACKGROUND

Intestinal inflammatory damage is an important factor in the development of graft-versus-host disease (GVHD). IFN-γ and IL-10 play key roles in gastrointestinal inflammation, and human placental mesenchymal stromal cells (hPMSCs) can alleviate inflammatory damage during GVHD. CD73 is highly expressed by hPMSCs. We aimed to study whether hPMSCs could alleviate intestinal damage in GVHD mice by modulating IFN-γ and IL-10 in CD4+T cells by CD73.

METHODS

A GVHD mouse model was induced using 8-week-old C57BL/6J and BALB/c mice, which were treated with regular hPMSCs (hPMSCs) or hPMSCs expressing low level of CD73 (shCD73). Then, the levels of IFN-γ and IL-10 in CD4+T cells were determined using flow cytometry. Transmission electron microscopy, western blotting, and morphological staining were employed to observe the intestinal damage.

RESULTS

hPMSCs ameliorated pathological damage and inhibited the reduction of the tight junction molecules occludin and ZO-1. They also downregulated IFN-γ and upregulated IL-10 secretion in CD4+T cells via CD73. Moreover, IL-10 mitigated the inhibitory effects of IFN-γ on the expression of occludin in both Caco-2 and NCM460 cells in vitro, but did not affect ZO-1. In addition, hPMSCs upregulated the level of AMPK phosphorylation in CD4+T cells by CD73, which is positively associated with the proportion of CD4+IFN-γ+IL-10+T, and CD4+IFN-γ-IL-10+T cells.

CONCLUSIONS

Our findings suggested that hPMSCs may balance the levels of IFN-γ and IL-10 in CD4+T cells by promoting the phosphorylation of AMPK via CD73, which alleviates the loss of occludin and ZO-1 in intestinal epithelial cells and, in turn, reduces inflammatory injury in GVHD mice.

Multiple Dimensions of using Mesenchymal Stem Cells for Treating Liver Diseases: From Bench to Beside

Liver diseases impose a huge burden worldwide. Although hepatocyte transplantation has long been considered as a potential strategy for treating liver diseases, its clinical implementation has created some obvious limitations. As an alternative strategy, cell therapy, particularly mesenchymal stem cell (MSC) transplantation, is widely used in treating different liver diseases, including acute liver disease, acute-on-chronic liver failure, hepatitis B/C virus, autoimmune hepatitis, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, alcoholic liver disease, liver fibrosis, liver cirrhosis, and hepatocellular carcinoma. Here, we summarize the status of MSC transplantation in treating liver diseases, focusing on the therapeutic mechanisms, including differentiation into hepatocyte-like cells, immunomodulating function with a variety of immune cells, paracrine effects via the secretion of various cytokines and extracellular vesicles, and facilitation of homing and engraftment. Some improved perspectives and current challenges are also addressed. In summary, MSCs have great potential in the treatment of liver diseases based on their multi-faceted characteristics, and more accurate mechanisms and novel therapeutic strategies stemming from MSCs will facilitate clinical practice.

Asiatic acid ameliorates rifampicin- and isoniazid-induced liver injury in vivo by regulating sphingolipid metabolism and mitogen-activated protein kinase signalling pathways

In this study, we aimed to determine whether asiatic acid (AA) exerts any therapeutic effects on rifampicin (RFP)- and isoniazid (INH)-induced liver injury and elucidate the underlying mechanisms. Briefly, liver injury in mice was induced via RFP and INH administration. We investigated the effects and potential action mechanisms of AA on liver injury using transcriptomics, metabolomics and various examinations. We found that AA significantly ameliorated the pathological changes in liver tissues and decreased the transaminase activity, inflammation and oxidative stress damage. Transcriptomics revealed 147 differentially expressed genes (DEGs) between the AA and model groups that were enriched in metabolic and mitogen-activated protein kinase (MAPK) signalling pathways. Metabolomics revealed 778 differentially expressed metabolites between the AA and model groups. Furthermore, integrated transcriptomics and metabolomics analyses revealed strong correlations between DEGs and differentially expressed metabolites and indicated that AA regulates the sphingolipid metabolism by inhibiting the expression of delta 4-desaturase, sphingolipid 1. Experimental results confirmed that AA inhibited the MAPK signalling pathway. In summary, AA inhibits inflammation and oxidative stress damage by regulating the sphingolipid metabolism pathway and blocking the MAPK signalling pathway, thereby relieving the RFP/INH-induced liver injury.

Liver Disease and Cell Therapy: Advances Made and Remaining Challenges

The limited availability of organs for liver transplantation, the ultimate curative treatment for end stage liver disease, has resulted in a growing and unmet need for alternative therapies. Mesenchymal stromal cells (MSCs) with their broad ranging anti-inflammatory and immunomodulatory properties have therefore emerged as a promising therapeutic agent in treating inflammatory liver disease. Significant strides have been made in exploring their biological activity. Clinical application of MSC has shifted the paradigm from using their regenerative potential to one which harnesses their immunomodulatory properties. Reassuringly, MSCs have been extensively investigated for over 30 years with encouraging efficacy and safety data from translational and early phase clinical studies, but questions remain about their utility. Therefore, in this review, we examine the translational and clinical studies using MSCs in various liver diseases and their impact on dampening immune-mediated liver damage. Our key observations include progress made thus far with use of MSCs for clinical use, inconsistency in the literature to allow meaningful comparison between different studies and need for standardized protocols for MSC manufacture and administration. In addition, the emerging role of MSC-derived extracellular vesicles as an alternative to MSC has been reviewed. We have also highlighted some of the remaining clinical challenges that should be addressed before MSC can progress to be considered as therapy for patients with liver disease.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: An Emerging Diagnostic and Therapeutic Biomolecules for Neurodegenerative Disabilities

Mesenchymal stem cells (MSCs) are a type of versatile adult stem cells present in various organs. These cells give rise to extracellular vesicles (EVs) containing a diverse array of biologically active elements, making them a promising approach for therapeutics and diagnostics. This article examines the potential therapeutic applications of MSC-derived EVs in addressing neurodegenerative disorders such as Alzheimer's disease (AD), multiple sclerosis (MS), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Furthermore, the present state-of-the-art for MSC-EV-based therapy in AD, HD, PD, ALS, and MS is discussed. Significant progress has been made in understanding the etiology and potential treatments for a range of neurodegenerative diseases (NDs) over the last few decades. The contents of EVs are carried across cells for intercellular contact, which often results in the control of the recipient cell's homeostasis. Since EVs represent the therapeutically beneficial cargo of parent cells and are devoid of many ethical problems connected with cell-based treatments, they offer a viable cell-free therapy alternative for tissue regeneration and repair. Developing innovative EV-dependent medicines has proven difficult due to the lack of standardized procedures in EV extraction processes as well as their pharmacological characteristics and mechanisms of action. However, recent biotechnology and engineering research has greatly enhanced the content and applicability of MSC-EVs.

Cigarette smoke attenuates mesenchymal stem cell-based suppression of immune cell-driven acute liver failure

Detrimental effects of smoking on mesenchymal stem cell (MSC)-dependent immunosuppression and hepatoprotection are unknown. Herewith, by using α-galactosylceramide (α-GalCer)-induced liver injury, a well-established murine model of fulminant hepatitis, we examined molecular mechanisms which were responsible for negative effects of cigarette smoke on MSC-dependent immunomodulation. MSC which were grown in cigarette smoke-exposed medium (MSCWS-CM) obtained pro-inflammatory phenotype, were not able to optimally produce hepatoprotective and immunosuppressive cytokines (TGF-β, HGF, IL-10, NO, KYN), and secreted significantly higher amounts of inflammatory cytokines (IFN-γ, TNF-α, IL-17, IL-6) than MSC that were cultured in standard medium never exposed to cigarette smoke (MSCCM). In contrast to MSCCM, which efficiently attenuated α-GalCer-induced hepatitis, MSCWS-CM were not able to prevent hepatocyte injury and liver inflammation. MSCWS-CM had reduced capacity for the suppression of liver-infiltrated inflammatory macrophages, dendritic cells (DCs) and lymphocytes. Although significantly lower number of IL-12-producing macrophages and DCs, TNF-α, IFN-γ or IL-17-producing CD4 + and CD8 +T lymphocytes, NK and NKT cells were noticed in the livers of α-GalCer+MSCCM-treated mice compared to α-GalCer+saline-treated animals, this phenomenon was not observed in α-GalCer-injured mice that received MSCWS-CM. MSCWS-CM could not induce expansion of anti-inflammatory IL-10-producing FoxP3 +CD4 + and CD8 + T regulatory cells and were not able to create immunosuppressive microenvironment in the liver as MSCCM. Similarly as it was observed in mice, MSCWS-CM were not able to optimally inhibit production of inflammatory and hepatototoxic cytokines in activated human Th1/Th17 and NKT1/NKT17 cells, confirming the hypothesis that cigarette smoke significantly attenuates therapeutic potential of MSC in cell-based immunotherapy of inflammatory liver diseases.

Scaling up human mesenchymal stem cell manufacturing using bioreactors for clinical uses

Human mesenchymal stem cells (hMSCs) are multipotent cells and an attractive therapeutic agent in regenerative medicine and intensive clinical research. Despite the great potential, the limitation that needs to be overcome is the necessity of ex vivo expansion because of insufficient number of hMSCs presented within adult organs and the high doses required for a transplantation. As a result, numerous research studies aim to provide novel expansion methods in order to achieve appropriate numbers of cells with preserved therapeutic quality. Bioreactor-based cell expansion provide high-level production of hMSCs in accordance with good manufacturing practice (GMP) and quality standards. This review summarizes current knowledge about the hMSCs manufacturing platforms with a main focus to the application of bioreactors for large-scale production of GMP-grade hMSCs.

Pretreated Mesenchymal Stem Cells and Their Secretome: Enhanced Immunotherapeutic Strategies

Mesenchymal stem cells (MSCs) with self-renewing, multilineage differentiation and immunomodulatory properties, have been extensively studied in the field of regenerative medicine and proved to have significant therapeutic potential in many different pathological conditions. The role of MSCs mainly depends on their paracrine components, namely secretome. However, the components of MSC-derived secretome are not constant and are affected by the stimulation MSCs are exposed to. Therefore, the content and composition of secretome can be regulated by the pretreatment of MSCs. We summarize the effects of different pretreatments on MSCs and their secretome, focusing on their immunomodulatory properties, in order to provide new insights for the therapeutic application of MSCs and their secretome in inflammatory immune diseases.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: New Soldiers in the War on Immune-Mediated Diseases

Inflammatory diseases are a group of debilitating disorders with varying degrees of long-lasting functional impairment of targeted system. New therapeutic agents that will attenuate on-going inflammation and, at the same time, promote regeneration of injured organ are urgently needed for the treatment of autoimmune and inflammatory disorders. During the last decade numerous studies have demonstrated that crucial therapeutic benefits of mesenchymal stem cells (MSCs) in inflammatory diseases are based on the effects of MSC-produced paracrine mediators and not on the activity of engrafted cells themselves. Thus, to overcome the limitations of stem cell transplantation, MSC-derived extracellular vesicles (MSC-EVs) have been rigorously investigated, as a promising cell-free pharmaceutical component. In this review, we focus on the mechanisms of MSC-EV covering the current knowledge on their potential therapeutic applications for immune-mediated diseases.

Improved efficacy of mesenchymal stromal cells stably expressing CXCR4 and IL-10 in a xenogeneic graft versus host disease mouse model

Previous clinical trials have shown that mesenchymal stromal cells (MSCs) can modulate graft versus host disease (GvHD) after allogeneic hematopoietic transplantation, although with variable efficacy. To improve the anti-GvHD effect of these cells, adipose tissue derived-human MSCs (Ad-MSCs) were transduced with a lentiviral vector conferring stable expression of CXCR4, a molecule involved in cell migration to inflamed sites, and IL-10, a cytokine with potent anti-inflammatory properties. In vitro experiments showed that the expression of these molecules in Ad-MSCs (named CXCR4-IL10-MSCs) efficiently enhanced their migration towards SDF-1α and also improved their immunomodulatory properties compared to unmodified Ad-MSCs (WT-MSCs). Moreover, using a humanized GvHD mouse model, CXCR4-IL10-MSCs showed improved therapeutic effects, which were confirmed by histopathologic analysis in the target organs. Additionally, compared to WT-MSCs, CXCR4-IL10-MSCs induced a more marked reduction in the number of pro-inflammatory Th1 and Th17 cells, a higher polarization towards an anti-inflammatory T cell profile (CD3⁺-IL10⁺ cells), and increased the number of regulatory T and B cells. Our in vitro and in vivo studies strongly suggest that CXCR4-IL10-MSCs should constitute an important new generation of MSCs for the treatment of GvHD in patients transplanted with allogeneic hematopoietic grafts.

Indoleamine 2,3-dioxygenase mediates the therapeutic effects of adipose-derived stromal/stem cells in experimental periodontitis by modulating macrophages through the kynurenine-AhR-NRF2 pathway

OBJECTIVES

Mesenchymal stromal/stem cell (MSC)-based therapy has become a promising approach to periodontal tissue repair. Adipose-derived stromal/stem cells (ASCs), compared with other dental or non-dental MSCs, serve as promising candidates for MSC therapy due to non-invasive acquisition and abundant sources. This study aimed to explore the effects of ASC therapy in experimental periodontitis and the underlying mechanism.

METHODS

Micro-CT was performed to evaluate the alveolar bone parameters following local injection of ASCs. Immunohistochemistry and immunofluorescence were employed to detect the expression of IL-1β, osteocalcin (OCN), nuclear factor (erythroid-derived 2)-like 2 (NRF2), and surface markers of macrophage polarization. Afterward, multiple reaction monitoring (MRM)-based targeted tryptophan metabolomic analysis was used to examine the ASC metabolites. Chromatin immunoprecipitation (ChIP)-qPCR assay was performed to investigate the direct binding of aryl hydrocarbon receptor (AhR) and NRF2.

RESULTS

Alveolar bone loss was reduced, and the ratio of iNOS⁺/CD206⁺ macrophages was significantly decreased after ASC injection in the rat models of periodontitis. ASCs promoted NRF2 expression and activation in macrophages, while NRF2 silencing in macrophages blocked the regulation of ASCs on macrophages. Furthermore, the expression of indoleamine 2,3-dioxygenase (IDO) of ASCs in the inflammatory condition was high. The inhibitor of IDO, 1-methyltryptophan (1-MT), impaired the therapeutic effects of ASCs in experimental periodontitis and regulation of macrophage polarization. Mechanistically, kynurenine (Kyn), a metabolite of ASCs catalyzed by IDO, activated AhR and enhanced its binding to the promoter of NRF2, which stimulated M2 macrophage polarization.

CONCLUSIONS

These findings suggested that ASCs can alleviate ligature-induced periodontitis through modulating macrophage polarization by the IDO-dependent Kyn-AhR-NRF2 pathway, uncovering a novel mechanism and providing a scientific basis for ASC-based therapy in experimental periodontitis.

Therapeutic potential of mesenchymal stem cells in the treatment of acute liver failure

Acute liver failure (ALF) is a severe and life-threatening condition in which rapid deterioration of liver function develops in a patient who has no preexisting liver disease. Mesenchymal stem cells (MSCs) are immunoregulatory stem cells which are able to modulate phenotype and function of all immune cells that play pathogenic role in the development and progression of ALF. MSCs in juxtacrine and paracrine manner attenuate antigen-presenting properties of dendritic cells and macrophages, reduce production of inflammatory cytokines in T lymphocytes, suppress hepatotoxicity of natural killer T (NKT) cells and promote generation and expansion of immunosuppressive T, B and NKT regulatory cells in acutely inflamed liver. Due to their nano-sized dimension and lipid envelope, intravenously injected MSC-derived exosomes (MSC-Exos) may by-pass all biological barriers to deliver MSC-sourced immunoregulatoy factors directly into the liver-infiltrated immune cells and injured hepatocytes. Results obtained by us and others revealed that intravenous administration of MSCs and MSC-Exos efficiently attenuated detrimental immune response and acute inflammation in the liver, suggesting that MSCs and MSC-Exos could be considered as potentially new remedies in the immunotherapy of ALF. In this review, we emphasize the current knowledge about molecular and cellular mechanisms which are responsible for MSC-based modulation of liver-infiltrated immune cells and we discuss different insights regarding the therapeutic potential of MSCs in liver regeneration.

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.

Exo-D-Mapps Attenuates Production of Inflammatory Cytokines and Promoted Generation of Immunosuppressive Phenotype in Peripheral Blood Mononuclear Cells

Mesenchymal stem cells (MSCs) produce immunomodulatory factors that regulate production of cytokines and chemokines in immune cells affecting their functional properties. Administration of MSCs-sourced secretome, including MSC-derived conditioned medium (MSC-CM) and MSC-derived exosomes (MSC-Exos), showed beneficial effects similar to those observed after transplantation of MSCs. Due to their nano-size dimension, MSC-Exos easily penetrate through the tissue and in paracrine and endocrine manner, may deliver MSC-sourced factors to the target immune cells modulating their function. MSCs derived from amniotic fluid (AF-MSCs) had superior cell biological properties than MSCs derived from bone marrow. We recently developed “Exosomes Derived Multiple Allogeneic Proteins Paracrine Signaling (Exo-d-MAPPS)”, a biological product in which the activity is based on AF-MSC-derived Exos capable to deliver immunomodulatory molecules and growth factors to the target cells. Herewith, we analyzed immunosuppressive capacity of Exo-d-MAPPS against human peripheral blood mononuclear cells (pbMNCs) and demonstrated that Exo-d-MAPPS efficiently suppressed generation of inflammatory phenotype in activated pbMNCs. Exo-d-MAPPS attenuated production of inflammatory cytokines and promoted generation of immunosuppressive phenotype in Lipopolysaccharide-primed pbMNCs. Exo-d-MAPPS treatment reduced expansion of inflammatory Th1 and Th17 cells and promoted generation of immunosuppressive T regulatory cells in the population of Concanavalin A-primed pbMNCs. Similarly, Exod-MAPPS treatment suppressed pro-inflammatory and promoted anti-inflammatory properties of α-GalCer-primed pbMNCs. In summing up, due to its capacity for suppression of activated pbMNCs, Exo-d-MAPPS should be further explored in animal models of acute and chronic inflammatory diseases as a potentially new remedy for the attenuation of detrimental immune response.

Application of Mesenchymal Stem Cells During Machine Perfusion: An Emerging Novel Strategy for Organ Preservation

Although solid organ transplantation remains the definitive management for patients with end-stage organ failure, this ultimate treatment has been limited by the number of acceptable donor organs. Therefore, efforts have been made to expand the donor pool by utilizing marginal organs from donation after circulatory death or extended criteria donors. However, marginal organs are susceptible to ischemia-reperfusion injury (IRI) and entail higher requirements for organ preservation. Recently, machine perfusion has emerged as a novel preservation strategy for marginal grafts. This technique continually perfuses the organs to mimic the physiologic condition, allows the evaluation of pretransplant graft function, and more excitingly facilitates organ reconditioning during perfusion with pharmacological, gene, and stem cell therapy. As mesenchymal stem cells (MSCs) have anti-oxidative, immunomodulatory, and regenerative properties, mounting studies have demonstrated the therapeutic effects of MSCs on organ IRI and solid organ transplantation. Therefore, MSCs are promising candidates for organ reconditioning during machine perfusion. This review provides an overview of the application of MSCs combined with machine perfusion for lung, kidney, liver, and heart preservation and reconditioning. Promising preclinical results highlight the potential clinical translation of this innovative strategy to improve the quality of marginal grafts.

Mesenchymal Stem Cell-Based Therapy as a New Approach for the Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is an intractable autoimmune disease with unmet medical needs. Conventional immunosuppressive therapies have modest efficacy and obvious side effects. Targeted therapies with small molecules and antibodies remain under investigation in small pilot studies. The major breakthrough was the development of autologous haematopoietic stem cell transplantation (AHSCT) to treat refractory SSc with rapidly progressive internal organ involvement. However, AHSCT is contraindicated in patients with advanced visceral involvement. Mesenchymal stem cells (MSCs) which are characterized by immunosuppressive, antifibrotic and proangiogenic capabilities may be a promising alternative option for the treatment of SSc. Multiple preclinical and clinical studies on the use of MSCs to treat SSc are underway. However, there are several unresolved limitations and safety concerns of MSC transplantation, such as immune rejections and risks of tumour formation, respectively. Since the major therapeutic potential of MSCs has been ascribed to their paracrine signalling, the use of MSC-derived extracellular vesicles (EVs)/secretomes/exosomes as a "cell-free" therapy might be an alternative option to circumvent the limitations of MSC-based therapies. In the present review, we overview the current knowledge regarding the therapeutic efficacy of MSCs in SSc, focusing on progresses reported in preclinical and clinical studies using MSCs, as well as challenges and future directions of MSC transplantation as a treatment option for patients with SSc.

Human Wharton's jelly-derived mesenchymal stem cells alleviate concanavalin A-induced fulminant hepatitis by repressing NF-κB signaling and glycolysis

Background

Fulminant hepatitis is a severe life-threatening clinical condition with rapid progressive loss of liver function. It is characterized by massive activation and infiltration of immune cells into the liver and disturbance of inflammatory cytokine production. Mesenchymal stem cells (MSCs) showed potent immunomodulatory properties. Transplantation of MSCs is suggested as a promising therapeutic approach for a host of inflammatory conditions.

Methods

In the current study, a well-established concanavalin A (Con A)-induced fulminant hepatitis mouse model was used to investigate the effects of transplanting human umbilical cord Wharton's jelly-derived MSCs (hWJ-MSCs) on fulminant hepatitis.

Results

We showed that hWJ-MSCs effectively alleviate fulminant hepatitis in mouse models, primarily through inhibiting T cell immunity. RNA sequencing of liver tissues and human T cells co-cultured with hWJ-MSCs showed that NF-κB signaling and glycolysis are two main pathways mediating the protective role of hWJ-MSCs on both Con A-induced hepatitis in vivo and T cell activation in vitro.

Conclusion

In summary, our data confirmed the potent therapeutic role of MSCs-derived from Wharton's jelly of human umbilical cord on Con A-induced fulminant hepatitis, and uncovered new mechanisms that glycolysis metabolic shift mediates suppression of T cell immunity by hWJ-MSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02560-x.

Indoleamine 2, 3-dioxygenase 1 aggravates acetaminophen-induced acute liver failure by triggering excess nitroxidative stress and iron accumulation

Acetaminophen (APAP) is the leading cause of acute liver failure (ALF), which is characterized by GSH depletion, oxidative stress and mitochondrial dysfunction. However, the specific mechanism of APAP-induced ALF remains to be clarified. In this study, we demonstrated that indoleamine 2,3-dioxygenase 1 (IDO1) aggravated APAP-induced ALF associated with excess lipid peroxidation, which was reversed by lipid peroxidation inhibitor (ferrostatin-1). Meanwhile, IDO1 deficiency effectively decreased the accumulation of reactive nitrogen species. Additionally, IDO1 deficiency prevented against APAP-induced liver injury through suppressing the activation of macrophages, thereby reduced their iron uptake and export, eventually reduced iron accumulation in hepatocytes through transferrin and transferrin receptor axis. In summary, our study confirmed that APAP-induced IDO1 aggravated ALF by triggering excess oxidative and nitrative stress and iron accumulation in liver. These results offer new insights for the clinical treatment of ALF or iron-dysregulated liver diseases in the future.

The Emerging Role of Exosomes in the Treatment of Human Disorders With a Special Focus on Mesenchymal Stem Cells-Derived Exosomes

Extracellular vesicles (EVs) are produced by diverse eukaryotic and prokaryotic cells. They have prominent roles in the modulation of cell-cell communication, inflammation versus immunomodulation, carcinogenic processes, cell proliferation and differentiation, and tissue regeneration. These acellular vesicles are more promising than cellular methods because of the lower risk of tumor formation, autoimmune responses and toxic effects compared with cell therapy. Moreover, the small size and lower complexity of these vesicles compared with cells have made their production and storage easier than cellular methods. Exosomes originated from mesenchymal stem cells has also been introduced as therapeutic option for a number of human diseases. The current review aims at summarization of the role of EVs in the regenerative medicine with a focus on their therapeutic impacts in liver fibrosis, lung disorders, osteoarthritis, colitis, myocardial injury, spinal cord injury and retinal injury.

Application of Modified Mesenchymal Stem Cells Transplantation in the Treatment of Liver Injury

Acute and chronic hepatitis, cirrhosis, and other liver diseases pose a serious threat to human health; however, liver transplantation is the only reliable treatment for the terminal stage of liver diseases. Previous researchers have shown that mesenchymal stem cells (MSCs) are characterized by differentiation and paracrine effects, as well as anti-oxidative stress and immune regulation functions. When MSCs are transplanted into animals, they migrate to the injured liver tissue along with the circulation, to protect the liver and alleviate the injury through the paracrine, immune regulation and other characteristics, making mesenchymal stem cell transplantation a promising alternative therapy for liver diseases. Although the efficacy of MSCs transplantation has been confirmed in various animal models of liver injury, many researchers have also proposed various pretreatment methods to improve the efficacy of mesenchymal stem cell transplantation, but there is still lack a set of scientific methods system aimed at improving the efficacy of transplantation therapy in scientific research and clinical practice. In this review, we summarize the possible mechanisms of MSCs therapy and compare the existing methods of MSCs modification corresponding to the treatment mechanism, hoping to provide as a reference to help future researchers explore a safe and simple transplantation strategy.

Molecular Mechanisms Responsible for Mesenchymal Stem Cell-Based Treatment of Viral Diseases

Mesenchymal stem cells (MSCs) are adult, immunomodulatory stem cells which reside in almost all postnatal tissues. Viral antigens and damage-associated molecular patterns released from injured and infected cells activate MSCs, which elicit strong antiviral immune response. MSC-sourced interferons and inflammatory cytokines modulate the cytotoxicity of NK cells and CTLs, enhance the antigen-presentation properties of DCs and macrophages, regulate cytokine synthesis in CD4+ T helper cells and promote antibody production in B cells. After the elimination of viral pathogens, MSCs produce immunoregulatory cytokines and trophic factors, prevent the over-activation of immune cells and promote tissue repair and regeneration. In this review article, we summarize the current knowledge on the molecular mechanisms that are responsible for the MSC-dependent elimination of virus-infected cells, and we emphasize the therapeutic potential of MSCs and their secretomes in the treatment of viral diseases.

Mesenchymal stromal cell-dependent immunoregulation in chemically-induced acute liver failure

Drug-induced liver injury (DILI), which refers to liver damage caused by a drug or its metabolites, has emerged as an important cause of acute liver failure (ALF) in recent years. Chemically-induced ALF in animal models mimics the pathology of DILI in humans; thus, these models are used to study the mechanism of potentially effective treatment strategies. Mesenchymal stromal cells (MSCs) possess immunomodulatory properties, and they alleviate acute liver injury and decrease the mortality of animals with chemically-induced ALF. Here, we summarize some of the existing research on the interaction between MSCs and immune cells, and discuss the possible mechanisms underlying the immuno-modulatory activity of MSCs in chemically-induced ALF. We conclude that MSCs can impact the phenotype and function of macrophages, as well as the differentiation and maturation of dendritic cells, and inhibit the proliferation and activation of T lymphocytes or B lymphocytes. MSCs also have immuno-modulatory effects on the production of cytokines, such as prostaglandin E2 and tumor necrosis factor-alpha-stimulated gene 6, in animal models. Thus, MSCs have significant benefits in the treatment of chemically-induced ALF by interacting with immune cells and they may be applied to DILI in humans in the near future.

Strategies to Potentiate Paracrine Therapeutic Efficacy of Mesenchymal Stem Cells in Inflammatory Diseases

Mesenchymal stem cells (MSCs) have been developed as cell therapeutics for various immune disorders using their immunoregulatory properties mainly exerted by their paracrine functions. However, variation among cells from different donors, as well as rapid clearance after transplantation have impaired the uniform efficacy of MSCs and limited their application. Recently, several strategies to overcome this limitation have been suggested and proven in pre-clinical settings. Therefore, in this review article, we will update the knowledge on bioengineering strategies to improve the immunomodulatory functions of MSCs, including genetic modification and physical engineering.

Apoptosis: A friend or foe in mesenchymal stem cell-based immunosuppression

Mesenchymal stem cells (MSC) are adult stem cells which reside in almost all postnatal tissue where, in juxtacrine and paracrine manner, regulate phenotype and function of immune cells, maintain tissue homeostasis, attenuate on-going inflammation and promote repair and regeneration of injured tissues. Due to their capacity to suppress detrimental immune response, MSC have been considered as potentially new therapeutic agents in the treatment of autoimmune and inflammatory diseases. It was recently revealed that apoptosis may increase anti-inflammatory properties of MSC by enhancing their capacity to induce generation of immunosuppressive phenotype in macrophages and dendritic cells. Upon phagocytosis, apoptotic MSC induce generation of immunosuppressive phenotype in monocytes/macrophages and promote production of anti-inflammatory cytokines and growth factors that attenuate inflammation and facilitate repair and regeneration of injured tissues. Importantly, immunomodulation mediated by apoptotic MSC was either similar or even better than immunomodulation accomplished by viable MSC. In contrast to viable MSC, which obtain either pro- or anti-inflammatory phenotype upon engraftment in different tissue microenvironments, apoptotic MSC were not subject to changes in their immunomodulatory characteristics upon diverse stimuli, indicating their potential for clinical use. In this chapter, we summarized current knowledge about beneficial effects of apoptotic MSC in the suppression of detrimental local and systemic immune response, and we emphasized their therapeutic potential in the treatment of inflammatory diseases.

Mesenchymal Stem Cells Attenuate Acute Liver Failure by Promoting Expansion of Regulatory T Cells in an Indoleamine 2,3-Dioxygenase-Dependent Manner

The influence of mesenchymal stem cells (MSCs) on the phenotype and function of CD4+CD49b+FoxP3- regulatory cells has not been elucidated. We used Concanavalin A (ConA) - and α-galactosylceramide (α-GalCer)-induced acute liver injury to estimate the effects of MSCs on liver-infiltrating CD4+CD49b+FoxP3-regulatory cells. MSCs significantly reduced ConA- and α-GalCer-mediated liver injury in C57BL/6 mice, as demonstrated by biochemical tests, reduced influx of inflammatory CD4+ T cells, and increased presence of CD4+CD49b+FoxP3- regulatory cells in the injured livers. The number of CD4+CD49b+FoxP3-regulatory cells was also significantly increased in α-GalCer-treated mice that received MSC-derived conditioned medium (MSC-CM). The presence of 1-methyltryptophan, a specific inhibitor of indoleamine 2,3-dioxygenase (IDO), in MSC-CM completely abrogated the hepatoprotective eff ect of MSCs and significantly decreased the total number of liver-infiltrated CD4+CD49b+FoxP3- regulatory cells, indicating the crucial importance of MSC-derived IDO for the expansion of CD4+CD49b+FoxP3- regulatory cells and the consequent MSC-dependent attenuation of acute liver injury.

The mechanisms of cellular crosstalk between mesenchymal stem cells and natural killer cells: Therapeutic implications

Mesenchymal stem cells (MSCs) are mesenchymal precursors of various origins, with well-known immunomodulatory effects. Natural killer (NK) cells, the major cells of the innate immune system, are critical for the antitumor and antiviral defenses; however, in certain cases, they may be the main culprits in the pathogenesis of some NK-related conditions such as autoimmunities and hematological malignancies. On the other hand, these cells seem to be the major responders in beneficial phenomena like graft versus leukemia. Substantial data suggest that MSCs can variably affect NK cells and can be affected by these cells. Accordingly, acquiring a profound understanding of the crosstalk between MSCs and NK cells and the involved mechanisms seems to be a necessity to develop therapeutic approaches based on such interactions. Therefore, in this study, we made a thorough review of the existing literature on the interactions between MSCs and NK cells with a focus on the underlying mechanisms. The current knowledge herein suggests that MSCs possess a great potential to be used as tools for therapeutic targeting of NK cells in disease context and that preconditioning of MSCs, as well as their genetic manipulation before administration, may provide a wider variety of options in terms of eliciting more specific and desirable therapeutic outcomes. Nevertheless, our knowledge regarding the effects of MSCs on NK cells is still in its infancy, and further studies with well-defined conditions are warranted herein.

Immunomodulatory and Tissue-preserving Effects of Human Dental Follicle Stem Cells in a Rat Cecal Ligation and Perforation Sepsis Model

BACKGROUND

Mesenchymal stem cells may be used for the treatment of sepsis. Dental follicle stem cells (DFSCs) are easily accessible but have not been studied in vivo or in clinical trials in sepsis models.

AIM OF THE STUDY

We aim to elucidate DFSC effects on host immunological functions in a rat cecal ligation and perforation (CLP) sepsis model.

METHODS

Adult male rats were categorized into group 1 (sham procedure SP), group 2 (SP + 1 × 10⁶ DFSCs administered 0 h after SP), group 3 (CLP + saline), group 4 (CLP + 1 × 10⁶ DFSCs administered 0 h after CLP), and group 5 (CLP + 1 × 10⁶ DFSCs administered 4 h after CLP). Green fluorescent protein-labeled cells were used for imaging. Histopathological examination of ileal tissues was performed.

RESULTS

A significant increase in the percentage of CD4+/CD25+/Foxp3+ Treg cells in groups 4 and 5 occurred compared with that in group 3. No significant changes in CD3+/CD4+ helper T-cells and CD3+/CD8+ cytotoxic T-cells were observed. Treatment with DFSCs at 4 h significantly decreased the level of TNF-α compared with that in group 3. No significant changes in IL-10 levels and lymphocyte proliferation suppression were observed. During histopathological examination, no high scoring (Chiu scores: 3 or 4) rats were observed in the curative treatment group (group 5).

CONCLUSIONS

Treatment with DFSC after 4 h of sepsis induction downregulates tissue inflammatory responses by decreasing TNF-α levels and increasing Treg cell ratio. This also has a protective effect on intestinal tissues during sepsis.

The role of Interleukin 1 receptor antagonist in mesenchymal stem cell-based tissue repair and regeneration

Interleukin (IL)-1 receptor antagonist (IL-1Ra), a naturally occurring antagonist of IL-1α/IL-1β signaling pathways, has been attributed to the immunosuppressive effects of mesenchymal stem cells (MSCs). MSCs, in IL-1Ra-dependent manner, suppressed production of IL-1β in dermal macrophages, induced their polarization in anti-inflammatory M2 phenotype, attenuated antigen-presenting properties of dendritic cells (DCs), and promoted expansion of immunosuppressive T regulatory cells in the skin, which resulted in enhanced repair of the nonhealing wounds. Reduced activation of inflammasome and suppressed production of IL-1β in macrophages were mainly responsible for beneficial effects of MSC-derived IL-1Ra in alleviation of acute lung injury, dry eye syndrome, and corneal injury. Through the production of IL-1Ra, MSCs reduced migration of DCs to the draining lymph nodes and attenuated generation of inflammatory Th1 and Th17 cells that resulted in alleviation of fulminant hepatitis and rheumatoid arthritis. MSCs, in IL-1Ra-dependent manner, reduced liver fibrosis by suppressing production of Type I collagen in hepatic stellate cells. IL-1Ra was, at least partially, responsible for enhanced proliferation of hepatocytes and chondrocytes in MSC-treated animals with partial hepatectomy and osteoarthritis. Despite of these beneficial effects, IL-1Ra-dependent inhibition of IL-1α/IL-1β-signaling significantly increased risk of infections. Therefore, future experimental and clinical studies should delineate potential side effects of MSC-derived IL-1Ra before IL-1Ra-overexpressing MSCs could be used as a potentially new therapeutic agent for the treatment of acute and chronic inflammatory diseases.

Mesenchymal stromal cells promote liver regeneration through regulation of immune cells

The liver is sensitive to pathogen-induced acute or chronic liver injury, and liver transplantation (LT) is the only effective strategy for end-stage liver diseases. However, the clinical application is limited by a shortage of liver organs, immunological rejection and high cost. Mesenchymal stromal cell (MSC)-based therapy has gradually become a hot topic for promoting liver regeneration and repairing liver injury in various liver diseases, since MSCs are reported to migrate toward injured tissues, undergo hepatogenic differentiation, inhibit inflammatory factor release and enhance the proliferation of liver cells in vivo. MSCs exert immunoregulatory effects through cell-cell contact and the secretion of anti-inflammatory factors to inhibit liver inflammation and promote liver regeneration. In addition, MSCs are reported to effectively inhibit the activation of cells of the innate immune system, including macrophages, natural killer (NK) cells, dendritic cells (DCs), monocytes and other immune cells, and inhibit the activation of cells of the adaptive immune system, including T lymphocytes, B lymphocytes and subsets of T cells or B cells. In the current review, we mainly focus on the potential effects and mechanisms of MSCs in inhibiting the activation of immune cells to attenuate liver injury in models or patients with acute liver failure (ALF), nonalcoholic fatty liver disease (NAFLD), and liver fibrosis and in patients or models after LT. We highlight that MSC transplantation may replace general therapies for eliminating acute or chronic liver injury in the near future.

Immune modulation by mesenchymal stem cells

Mesenchymal stem cells (MSCs) can be derived from various adult tissues with multipotent and self-renewal abilities. The characteristics of presenting no major ethical concerns, having low immunogenicity and possessing immune modulation functions make MSCs promising candidates for stem cell therapies. MSCs could promote inflammation when the immune system is underactivated and restrain inflammation when the immune system is overactivated to avoid self-overattack. These cells express many immune suppressors to switch them from a pro-inflammatory phenotype to an anti-inflammatory phenotype, resulting in immune effector cell suppression and immune suppressor cell activation. We would discuss the mechanisms governing the immune modulation function of these cells in this review, especially the immune-suppressive effects of MSCs.

Mesenchymal Stem Cell-Derived Exosomes and Other Extracellular Vesicles as New Remedies in the Therapy of Inflammatory Diseases

There is growing evidence that mesenchymal stem cell (MSC)-based immunosuppression was mainly attributed to the effects of MSC-derived extracellular vesicles (MSC-EVs). MSC-EVs are enriched with MSC-sourced bioactive molecules (messenger RNA (mRNA), microRNAs (miRNAs), cytokines, chemokines, immunomodulatory factors) that regulate phenotype, function and homing of immune cells. In this review article we emphasized current knowledge regarding molecular mechanisms responsible for the therapeutic effects of MSC-EVs in attenuation of autoimmune and inflammatory diseases. We described the disease-specific cellular targets of MSC-EVs and defined MSC-sourced molecules, which were responsible for MSC-EV-based immunosuppression. Results obtained in a large number of experimental studies revealed that both local and systemic administration of MSC-EVs efficiently suppressed detrimental immune response in inflamed tissues and promoted survival and regeneration of injured parenchymal cells. MSC-EVs-based anti-inflammatory effects were relied on the delivery of immunoregulatory miRNAs and immunomodulatory proteins in inflammatory immune cells (M1 macrophages, dendritic cells (DCs), CD4+Th1 and Th17 cells), enabling their phenotypic conversion into immunosuppressive M2 macrophages, tolerogenic DCs and T regulatory cells. Additionally, through the delivery of mRNAs and miRNAs, MSC-EVs activated autophagy and/or inhibited apoptosis, necrosis and oxidative stress in injured hepatocytes, neurons, retinal cells, lung, gut and renal epithelial cells, promoting their survival and regeneration.

Melatonin prevents senescence of canine adipose-derived mesenchymal stem cells through activating NRF2 and inhibiting ER stress

Transplantation of adipose-derived mesenchymal stem cells (ADMSCs) can aid in the treatment of numerous diseases in animals. However, natural aging during in vitro expansion of ADMSCs prior to their use in transplantation restricts their beneficial effects. Melatonin is reported to exert biorhythm regulation, anti-oxidation, and anti-senescence effects in various animal and cell models. Herein, by using a senescent canine ADMSCs (cADMSCs) cell model subjected to multiple passages in vitro, we investigated the effects of melatonin on ADMSCs senescence. We found that melatonin alleviates endoplasmic reticulum stress (ERS) and cell senescence. MT1/MT2 melatonin receptor inhibitor, luzindole, diminished the mRNA expression levels and rhythm expression amplitude of Bmal1 and Nrf2 genes. Nrf2 knockdown blocked the stimulatory effects of melatonin on endoplasmic reticulum-associated degradation (ERAD)-related gene expression and its inhibitory effects on ERS-related gene expression. At the same time, the inhibitory effects of melatonin on the NF-κB signaling pathway and senescence-associated secretory phenotype (SASP) were blocked by Nrf2 knockdown in cADMSCs. Melatonin pretreatment improved the survival of cADMSCs and enhanced the beneficial effects of cADMSCs transplantation in canine acute liver injury. These results indicate that melatonin activates Nrf2 through the MT1/MT2 receptor pathway, stimulates ERAD, inhibits NF-κB and ERS, alleviates cADMSCs senescence, and improves the efficacy of transplanted cADMSCs.

Molecular Mechanisms Responsible for Therapeutic Potential of Mesenchymal Stem Cell-Derived Secretome

Mesenchymal stem cell (MSC)-sourced secretome, defined as the set of MSC-derived bioactive factors (soluble proteins, nucleic acids, lipids and extracellular vesicles), showed therapeutic effects similar to those observed after transplantation of MSCs. MSC-derived secretome may bypass many side effects of MSC-based therapy, including unwanted differentiation of engrafted MSCs. In contrast to MSCs which had to be expanded in culture to reach optimal cell number for transplantation, MSC-sourced secretome is immediately available for treatment of acute conditions, including fulminant hepatitis, cerebral ischemia and myocardial infarction. Additionally, MSC-derived secretome could be massively produced from commercially available cell lines avoiding invasive cell collection procedure. In this review article we emphasized molecular and cellular mechanisms that were responsible for beneficial effects of MSC-derived secretomes in the treatment of degenerative and inflammatory diseases of hepatobiliary, respiratory, musculoskeletal, gastrointestinal, cardiovascular and nervous system. Results obtained in a large number of studies suggested that administration of MSC-derived secretomes represents a new, cell-free therapeutic approach for attenuation of inflammatory and degenerative diseases. Therapeutic effects of MSC-sourced secretomes relied on their capacity to deliver genetic material, growth and immunomodulatory factors to the target cells enabling activation of anti-apoptotic and pro-survival pathways that resulted in tissue repair and regeneration.

Modulating autophagy in mesenchymal stem cells effectively protects against hypoxia- or ischemia-induced injury

In mammals, a basal level of autophagy, a self-eating cellular process, degrades cytosolic proteins and subcellular organelles in lysosomes to provide energy, recycles the cytoplasmic components, and regenerates cellular building blocks; thus, autophagy maintains cellular and tissue homeostasis in all eukaryotic cells. In general, adaptive autophagy increases when cells confront stressful conditions to improve the survival rate of the cells, while destructive autophagy is activated when the cellular stress is not manageable and elicits the regenerative capacity. Hypoxia-reoxygenation (H/R) injury and ischemia-reperfusion (I/R) injury initiate excessive autophagy and endoplasmic reticulum (ER) stress and consequently induce a string of damage in mammalian tissues or organs. Mesenchymal stem cell (MSC)-based therapy has yielded promising results in repairing H/R- or I/R-induced injury in various tissues. However, MSC transplantation in vivo must overcome the barriers including the low survival rate of transplanted stem cells, limited targeting capacity, and low grafting potency; therefore, much effort is needed to increase the survival and activity of MSCs in vivo. Modulating autophagy regulates the stemness and the anti-oxidative stress, anti-apoptosis, and pro-survival capacity of MSCs and can be applied to MSC-based therapy for repairing H/R- or I/R-induced cellular or tissue injury.

Mesenchymal stem cell therapy for the treatment of inflammatory diseases: Challenges, opportunities, and future perspectives

Mesenchymal stem cells (MSCs) are promising alternative agents for the treatment of inflammatory disorders due to their immunomodulatory functions, and several clinical trials on MSC-based products are currently being conducted. In this review, we discuss recent progress made on the use of MSCs as immunomodulatory agents, developmental challenges posed by MSC-based therapy, and the strategies being used to overcome these challenges. In this context, current understanding of the mechanisms responsible for MSC interactions with the immune system and the molecular responses of MSCs to inflammatory signals are discussed. The immunosuppressive activities of MSCs are initiated by cell-to-cell contact and the release of immuno-regulatory molecules. By doing so, MSCs can inhibit the proliferation and function of T cells, natural killer cells, B cells, and dendritic cells, and can also increase the proliferation of regulatory T cells. However, various problems, such as low transplanted cell viability, poor homing and engraftment into injured tissues, MSC heterogeneity, and lack of adequate information on optimum MSC doses impede clinical applications. On the other hand, it has been shown that the immunomodulatory activities and viabilities of MSCs might be enhanced by 3D-cultured systems, genetic modifications, preconditioning, and targeted-delivery.

Current understanding of the immunosuppressive properties of mesenchymal stromal cells

Several studies have demonstrated the anti-inflammatory potential of mesenchymal stromal cells (MSCs) isolated from bone marrow, adipose tissue, placenta, and other sources. Nevertheless, MSCs may also induce immunosuppression when administered systemically or directly to injured environments, as shown in different preclinical disease models. MSCs express certain receptors, including toll-like receptors and the aryl-hydrocarbon receptor, that are activated by the surrounding environment, thus leading to modulation of their immunosuppressive activity. Once MSCs are activated, they can affect a wide range of immune cells (e.g., neutrophils, monocytes/macrophages, dendritic cells, natural killer cells, T and B lymphocytes), a phenomenon that has been correlated to secretion of several mediators (e.g., indolamine 2,3-dioxygenase, galectins, prostaglandin E₂, nitric oxide, and damage- and pathogen-associated molecular patterns) and stimulation of certain signaling pathways (e.g., protein kinase R, signal transducer and activator of transcription-1, nuclear factor-κB). Additionally, MSC manipulation and culture conditions, as well as the number of passages, duration of cryopreservation, and O₂ content available, can significantly affect the immunosuppressive properties of MSCs. This review sheds light on current knowledge regarding the mechanisms by which MSCs exert immunosuppressive effects both in vitro and in vivo, focusing on the receptors expressed by MSCs, the correlation between soluble factors secreted by MSCs and their immunosuppressive effects, and interactions between MSCs and immune cells.

Molecular Mechanisms Involved in Oxidative Stress-Associated Liver Injury Induced by Chinese Herbal Medicine: An Experimental Evidence-Based Literature Review and Network Pharmacology Study

Oxidative stress, defined as a disequilibrium between pro-oxidants and antioxidants, can result in histopathological lesions with a broad spectrum, ranging from asymptomatic hepatitis to hepatocellular carcinoma in an orchestrated manner. Although cells are equipped with sophisticated strategies to maintain the redox biology under normal conditions, the abundance of redox-sensitive xenobiotics, such as medicinal ingredients originated from herbs or animals, can dramatically invoke oxidative stress. Growing evidence has documented that the hepatotoxicity can be triggered by traditional Chinese medicine (TCM) during treating various diseases. Meanwhile, TCM-dependent hepatic disorder represents a strong correlation with oxidative stress, especially the persistent accumulation of intracellular reactive oxygen species. Of note, since TCM-derived compounds with their modulated targets are greatly diversified among themselves, it is complicated to elaborate the potential pathological mechanism. In this regard, data mining approaches, including network pharmacology and bioinformatics enrichment analysis have been utilized to scientifically disclose the underlying pathogenesis. Herein, top 10 principal TCM-modulated targets for oxidative hepatotoxicity including superoxide dismutases (SOD), malondialdehyde (MDA), glutathione (GSH), reactive oxygen species (ROS), glutathione peroxidase (GPx), Bax, caspase-3, Bcl-2, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and nitric oxide (NO) have been identified. Furthermore, hepatic metabolic dysregulation may be the predominant pathological mechanism involved in TCM-induced hepatotoxic impairment.

Modulation of autophagy as new approach in mesenchymal stem cell-based therapy

Due to their trophic and immunoregulatory characteristics mesenchymal stem cells (MSCs) have tremendous potential for use in a variety of clinical applications. Challenges in MSCs' clinical applications include low survival of transplanted cells and low grafting efficiency requiring use of a high number of MSCs to achieve therapeutic benefits. Accordingly, new approaches are urgently needed in order to overcome these limitations. Recent evidence indicates that modulation of autophagy in MSCs prior to their transplantation enhances survival and viability of engrafted MSCs and promotes their pro-angiogenic and immunomodulatory characteristics. Here, we review the current literature describing mechanisms by which modulation of autophagy strengthens pro-angiogenic and immunosuppressive characteristics of MSCs in animal models of multiple sclerosis, osteoporosis, diabetic limb ischemia, myocardial infarction, acute graft-versus-host disease, kidney and liver diseases. Obtained results suggest that modulation of autophagy in MSCs may represent a new therapeutic approach that could enhance efficacy of MSCs in the treatment of ischemic and autoimmune diseases.

Crosstalk between mesenchymal stem cells and T regulatory cells is crucially important for the attenuation of acute liver injury

One of the therapeutic options for the treatment of fulminant hepatitis is repopulation of intrahepatic regulatory cells because their pool is significantly reduced during acute liver failure. Although it is known that mesenchymal stem cells (MSCs), which have beneficent effects in the therapy of fulminant hepatitis, may promote expansion of regulatory T cells (Tregs) and regulatory B cells (Bregs), the role of these regulatory cells in MSC-mediated attenuation of acute liver injury is unknown. Herewith, we described the molecular mechanisms involved in the crosstalk between MSCs and liver regulatory cells and analyzed the potential of MSC-based therapy for the expansion of intrahepatic regulatory cells in mouse model of acute liver failure. MSC-dependent attenuation of α-galactosylceramide (α-GalCer)-induced acute liver injury in mice was accompanied with an increased presence of interleukin (IL) 10-producing CD4⁺ CD25⁺ forkhead box P3⁺ Tregs and IL10- and transforming growth factor β-producing marginal zone-like Bregs in the liver. Depletion of Bregs did not alter MSC-based alleviation of acute liver failure, whereas depletion of Tregs completely abrogated hepatoprotective effects of MSCs and inhibited their capacity to attenuate hepatotoxicity of liver natural killer T cells (NKTs), indicating that Tregs, and not Bregs, were critically involved in MSC-based modulation of acute liver inflammation. MSCs, in a paracrine, indoleamine 2,3-dioxygenase-dependent manner, significantly increased the capacity of Tregs to produce immunosuppressive IL10 and to suppress hepatotoxicity of liver NKTs. Accordingly, adoptive transfer of MSC-primed Tregs resulted in the complete attenuation of α-GalCer-induced acute liver failure. In conclusion, our findings highlighted the crucial importance of Tregs for MSC-based attenuation of acute liver failure and indicated the significance of MSC-mediated priming of Tregs as a new therapeutic approach in Treg-based therapy of acute liver injury. Liver Transplantation 24 687-702 2018 AASLD.

Attenuation of NK cells facilitates mammary tumor growth in streptozotocin-induced diabetes in mice

Diabetic patients have higher incidence and mortality of cancer. Recent study revealed that hyperglycemia-induced oxidative stress is involved in the acceleration of tumor metastasis. We used model of high-dose streptozotocin-induced diabetes to investigate its effect on tumor growth and modulation of antitumor immune response of 4T1 murine breast cancer in BALB/c mice. Diabetes accelerated tumor appearance, growth and weight, which was associated with decreased NK cells cytotoxicity against 4T1 tumor cells in vitro Diabetes reduced frequencies of systemic NKG2D⁺, perforin⁺, granzyme⁺, IFN-γ⁺ and IL-17⁺ NK cells, while increased level of PD-1 expression and production of IL-10 in NK cells. Diabetes decreased percentage of NKG2D⁺NK cells and increased percentage of PD-1⁺ NK cells also in primary tumor. Diabetes increased accumulation of IL-10⁺ Tregs and TGF-β⁺ myeloid-derived suppressor cells (MDSCs) in spleen and tumor. Diabetic sera in vitro significantly increased the percentage of KLRG-1⁺ and PD-1⁺ NK cells, decreased the percentage of IFN-γ⁺NK cells, expression of NKp46 and production of perforin, granzyme, CD107a and IL-17 per NK cell in comparison to glucose-added mouse sera and control sera. Significantly increased percentages of inducible nitric oxide synthase (iNOS) and indoleamine 2,3-dioxygenase (IDO) producing MDSCs and dendritic cells (DC) were found in the spleens of diabetic mice prior to tumor induction. 1-methyl-DL-tryptophan, specific IDO inhibitor, almost completely restored phenotype of NK cells cultivated in diabetic sera. These findings indicate that diabetes promotes breast cancer growth at least in part through increased accumulation of immunosuppressive cells and IDO-mediated attenuation of NK cells.

Molecular mechanisms underlying therapeutic potential of pericytes

BACKGROUND

Pericytes are multipotent cells present in every vascularized tissue in the body. Despite the fact that they are well-known for more than a century, pericytes are still representing cells with intriguing properties. This is mainly because of their heterogeneity in terms of definition, tissue distribution, origin, phenotype and multi-functional properties. The body of knowledge illustrates importance of pericytes in the regulation of homeostatic and healing processes in the body.

MAIN BODY

In this review, we summarized current knowledge regarding identification, isolation, ontogeny and functional characteristics of pericytes and described molecular mechanisms involved in the crosstalk between pericytes and endothelial or immune cells. We highlighted the role of pericytes in the pathogenesis of fibrosis, diabetes-related complications (retinopathy, nephropathy, neuropathy and erectile dysfunction), ischemic organ failure, pulmonary hypertension, Alzheimer disease, tumor growth and metastasis with the focus on their therapeutic potential in the regenerative medicine. The functions and capabilities of pericytes are impressive and, as yet, incompletely understood. Molecular mechanisms responsible for pericyte-mediated regulation of vascular stability, angiogenesis and blood flow are well described while their regenerative and immunomodulatory characteristics are still not completely revealed. Strong evidence for pericytes' participation in physiological, as well as in pathological conditions reveals a broad potential for their therapeutic use. Recently published results obtained in animal studies showed that transplantation of pericytes could positively influence the healing of bone, muscle and skin and could support revascularization. However, the differences in their phenotype and function as well as the lack of standardized procedure for their isolation and characterization limit their use in clinical trials.

CONCLUSION

Critical to further progress in clinical application of pericytes will be identification of tissue specific pericyte phenotype and function, validation and standardization of the procedure for their isolation that will enable establishment of precise clinical settings in which pericyte-based therapy will be efficiently applied.

Molecular Mechanisms Responsible for Anti-inflammatory and Immunosuppressive Effects of Mesenchymal Stem Cell-Derived Factors

Mesenchymal stem cells (MSCs) are self-renewable cells capable for multilineage differentiation and immunomodulation. MSCs are able to differentiate into all cell types of mesodermal origin and, due to their plasticity, may generate cells of neuroectodermal or endodermal origin in vitro. In addition to the enormous differentiation potential, MSCs efficiently modulate innate and adaptive immune response and, accordingly, were used in large number of experimental and clinical trials as new therapeutic agents in regenerative medicine. Although MSC-based therapy was efficient in the treatment of many inflammatory and degenerative diseases, unwanted differentiation of engrafted MSCs represents important safety concern. MSC-based beneficial effects are mostly relied on the effects of MSC-derived immunomodulatory, pro-angiogenic, and trophic factors which attenuate detrimental immune response and inflammation, reduce ischemic injuries, and promote tissue repair and regeneration. Accordingly, MSC-conditioned medium (MSC-CM), which contains MSC-derived factors, has the potential to serve as a cell-free, safe therapeutic agent for the treatment of inflammatory diseases. Herein, we summarized current knowledge regarding identification, isolation, ontogeny, and functional characteristics of MSCs and described molecular mechanisms responsible for MSC-CM-mediated anti-inflammatory and immunosuppressive effects in the therapy of inflammatory lung, liver, and kidney diseases and ischemic brain injury.

Mesenchymal Stem Cells as New Therapeutic Agents for the Treatment of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a chronic autoimmune cholestatic liver disease characterized by the progressive destruction of small- and medium-sized intrahepatic bile ducts with resultant cholestasis and progressive fibrosis. Ursodeoxycholic acid and obethicholic acid are the only agents approved by the US Food and Drug Administration (FDA) for the treatment of PBC. However, for patients with advanced, end-stage PBC, liver transplantation is still the most effective treatment. Accordingly, the alternative approaches, such as mesenchymal stem cell (MSC) transplantation, have been suggested as an effective alternative therapy for these patients. Due to their immunomodulatory characteristics, MSCs are considered as promising therapeutic agents for the therapy of autoimmune liver diseases, including PBC. In this review, we have summarized the therapeutic potential of MSCs for the treatment of these diseases, emphasizing molecular and cellular mechanisms responsible for MSC-based effects in an animal model of PBC and therapeutic potential observed in recently conducted clinical trials. We have also presented several outstanding problems including safety issues regarding unwanted differentiation of transplanted MSCs which limit their therapeutic use. Efficient and safe MSC-based therapy for PBC remains a challenging issue that requires continuous cooperation between clinicians, researchers, and patients.