Short and Long Term Clinical and Immunologic Follow up after Bone Marrow Mesenchymal Stromal Cell Therapy in Progressive Multiple Sclerosis-A Phase I Study

Translational potential of mesenchymal stem cells in regenerative therapies for human diseases: challenges and opportunities

Advances in stem cell technology offer new possibilities for patients with untreated diseases and disorders. Stem cell-based therapy, which includes multipotent mesenchymal stem cells (MSCs), has recently become important in regenerative therapies. MSCs are multipotent progenitor cells that possess the ability to undergo in vitro self-renewal and differentiate into various mesenchymal lineages. MSCs have demonstrated promise in several areas, such as tissue regeneration, immunological modulation, anti-inflammatory qualities, and wound healing. Additionally, the development of specific guidelines and quality control methods that ultimately result in the therapeutic application of MSCs has been made easier by recent advancements in the study of MSC biology. This review discusses the latest clinical uses of MSCs obtained from the umbilical cord (UC), bone marrow (BM), or adipose tissue (AT) in treating various human diseases such as pulmonary dysfunctions, neurological disorders, endocrine/metabolic diseases, skin burns, cardiovascular conditions, and reproductive disorders. Additionally, this review offers comprehensive information regarding the clinical application of targeted therapies utilizing MSCs. It also presents and examines the concept of MSC tissue origin and its potential impact on the function of MSCs in downstream applications. The ultimate aim of this research is to facilitate translational research into clinical applications in regenerative therapies.

Re-establishing immune tolerance in multiple sclerosis: focusing on novel mechanisms of mesenchymal stem cell regulation of Th17/Treg balance

The T-helper 17 (Th17) cell and regulatory T cell (Treg) axis plays a crucial role in the development of multiple sclerosis (MS), which is regarded as an immune imbalance between pro-inflammatory cytokines and the maintenance of immune tolerance. Mesenchymal stem cell (MSC)-mediated therapies have received increasing attention in MS research. In MS and its animal model experimental autoimmune encephalomyelitis, MSC injection was shown to alter the differentiation of CD4+T cells. This alteration occurred by inducing anergy and reduction in the number of Th17 cells, stimulating the polarization of antigen-specific Treg to reverse the imbalance of the Th17/Treg axis, reducing the inflammatory cascade response and demyelination, and restoring an overall state of immune tolerance. In this review, we summarize the mechanisms by which MSCs regulate the balance between Th17 cells and Tregs, including extracellular vesicles, mitochondrial transfer, metabolic reprogramming, and autophagy. We aimed to identify new targets for MS treatment using cellular therapy by analyzing MSC-mediated Th17-to-Treg polarization.

Neurological efficacy and safety of mesenchymal stem cells (MSCs) therapy in people with multiple sclerosis (pwMS): An updated systematic review and meta-analysis

BACKGROUND

Current therapeutic strategies for multiple sclerosis (MS) aim to suppress the immune response and reduce relapse rates. As alternative treatments, mesenchymal stem cells (MSCs) are being explored. MSCs show promise in repairing nerve tissue and reducing autoimmune responses in people with MS (pwMS).

OBJECTIVE

This review delves into the literature on the efficacy and safety of MSC therapy for pwMS.

METHODS

A comprehensive search strategy was employed to identify relevant articles from five databases until January 2024. The inclusion criteria encompassed interventional studies. Efficacy and safety data concerning MSC therapy in relapsing-remitting MS (RRMS), secondary progressive MS (SPMS), and primary progressive MS (PPMS) groups were extracted and analyzed.

RESULTS

A comprehensive analysis encompassing 30 studies revealed that individuals who underwent intrathecal (IT) protocol-based transplantation of MSCs experienced a noteworthy improvement in their expanded disability status scale (EDSS) compared to the placebo group. Weighted mean difference (WMD) was -0.28; 95 % CI -0.53 to -0.03, I2 = 0 %, p-value = 0.028); however, the intravenous (IV) group did not show significant changes in EDSS scores. The annualized relapse rate (ARR) did not significantly decrease among pwMS (WMD = -0.34; 95 % CI -1.05 to 0.38, I2 = 98 %, p-value = 0.357). Favorable results were observed in magnetic resonance imaging (MRI), with only 19.11 % of pwMS showing contrast-enhanced lesions (CEL) in the short term and no long-term MRI activity. The most common complications in both short-term and long-term follow-ups were infection, back pain, and gastrointestinal symptoms.

CONCLUSIONS

The study highlights the safety potential of MSC therapy for pwMS. While MRI-based neural regeneration shows significant treatment potential, the effectiveness of MSC therapy remains uncertain due to study limitations and ineffective outcome measures. Further research is needed to establish efficacy and optimize evaluation methods for MSC therapy on pwMS.

The Therapeutic Mechanisms of Mesenchymal Stem Cells in MS-A Review Focusing on Neuroprotective Properties

In multiple sclerosis (MS), there is a great need for treatment with the ability to suppress compartmentalized inflammation within the central nervous system (CNS) and to promote remyelination and regeneration. Mesenchymal stem cells (MSCs) represent a promising therapeutic option, as they have been shown to migrate to the site of CNS injury and exert neuroprotective properties, including immunomodulation, neurotrophic factor secretion, and endogenous neural stem cell stimulation. This review summarizes the current understanding of the underlying neuroprotective mechanisms and discusses the translation of MSC transplantation and their derivatives from pre-clinical demyelinating models to clinical trials with MS patients.

Mesenchymal Stem Cell Therapy in Multiple Sclerosis: A Systematic Review and Meta-Analysis

The assurance of safety and effectiveness is a significant focal point in all therapeutic approaches. Although mesenchymal stem cells (MSCs) have been identified as a potential novel therapeutic strategy for multiple sclerosis (MS), existing evidence regarding the effectiveness and safety of this strategy remains inconclusive. Thus, the primary aim of this systematic review and meta-analysis (SRMA) was to comprehensively assess the effectiveness and safety of MSC therapy in individuals diagnosed with MS. A comprehensive search was conducted using appropriate keywords in the PubMed, Scopus, Cochrane, ScienceDirect, and Google Scholar databases to determine the eligible studies. The change in the expanded disability status scale (EDSS) score from baseline to follow-up was used to assess MSC efficacy. The effectiveness of the therapy was assessed using a random-effects model, which calculated the combined prevalence and 95% confidence intervals (CIs) for MS patients who experienced improvement, stability, or worsening of their condition. The protocol was registered in PROSPERO (CRD42020209671). The findings indicate that 40.4% (95% CI: 30.6-50.2) of MS patients exhibited improvements following MSC therapy, 32.8% (95% CI: 25.5-40.1) remained stable, and 18.1% (95% CI: 12.0-24.2) experienced a worsening of their condition. Although no major complications were observed, headaches 57.6 [37.9-77.3] and fever 53.1 [20.7-85.4] were commonly reported as minor adverse events. All of the results reported in this meta-analysis are consistent and credible according to the sensitivity analyses. Regardless of different individual studies, our meta-analysis provides a comprehensive overview showing the potential of MSC therapy as a possible effective treatment strategy for patients with MS.

Mesenchymal stromal cell-derived secretome-based therapy for neurodegenerative diseases: overview of clinical trials

BACKGROUND

Over the past few years, mesenchymal stromal cells (MSCs) have attracted a great deal of scientific attention owing to their promising results in the treatment of incurable diseases. However, there are several concerns about their possible side effects after direct cell transplantation, including host immune response, time-consuming cell culture procedures, and the dependence of cell quality on the donor, which limit the application of MSCs in clinical trials. On the other hand, it is well accepted that the beneficial effects of MSCs are mediated by secretome rather than cell replacement. MSC secretome refers to a variety of bioactive molecules involved in different biological processes, specifically neuro-regeneration.

MAIN BODY

Due to the limited ability of the central nervous system to compensate for neuronal loss and relieve disease progress, mesenchymal stem cell products may be used as a potential cure for central nervous system disorders. In the present study, the therapeutic effects of MSC secretome were reviewed and discussed the possible mechanisms in the three most prevalent central nervous system disorders, namely Alzheimer's disease, multiple sclerosis, and Parkinson's disease. The current work aimed to help discover new medicine for the mentioned complications.

CONCLUSION

The use of MSC-derived secretomes in the treatment of the mentioned diseases has encouraging results, so it can be considered as a treatment option for which no treatment has been introduced so far.

Current advances in the pharmacological prevention and management of cognitive dysfunction in multiple sclerosis

INTRODUCTION

Cognitive impairment (CI) is a core feature of Multiple Sclerosis (MS), being detectable in up to 65% of subjects. Treatment of CI can be considered of paramount importance. However, no standardized strategies are available to date to define the best treatment approach, especially for the pharmacological management.

AREAS COVERED

In this narrative review, the authors outline the latest advances in pharmacological management of CI in MS, including Disease Modifying Treatments (DMTs) which indirectly may or may not influence CI and symptomatic drugs. Selected publications were restricted to those written in English, reporting on an adult relapsing-remitting MS or progressive MS sample, assessing the effects of (at least) 1 DMT or treatment in a longitudinal design, reporting data on (at least) one standardized cognitive test performed at baseline and follow-up, and published between January 2018 and May 2022.

EXPERT OPINION

Recent data can be considered encouraging and inspiring for future studies. Overall, there is preliminary evidence of a beneficial effect of DMTs on cognition, particularly for high-efficacy DMTs. As for symptomatic treatments, dalfampridine appears to be the only medication with robust evidence of a positive effect on cognition. However, the definition of clinically meaningful change/improvement in cognitive functions remains an unmet need. Future studies should assess the role of other patient-related factors that can be associated with a better cognitive response to treatments and investigate the possible positive effect of multimodal interventions on cognition.

Aging and Mesenchymal Stem Cells: Basic Concepts, Challenges and Strategies

Aging and frailty are complex processes implicating multifactorial mechanisms, such as replicative senescence, oxidative stress, mitochondrial dysfunction, or autophagy disorder. All of these mechanisms drive dramatic changes in the tissue environment, such as senescence-associated secretory phenotype factors and inflamm-aging. Thus, there is a demand for new therapeutic strategies against the devastating effects of the aging and associated diseases. Mesenchymal stem cells (MSC) participate in a "galaxy" of tissue signals (proliferative, anti-inflammatory, and antioxidative stress, and proangiogenic, antitumor, antifibrotic, and antimicrobial effects) contributing to tissue homeostasis. However, MSC are also not immune to aging. Three strategies based on MSC have been proposed: remove, rejuvenate, or replace the senescent MSC. These strategies include the use of senolytic drugs, antioxidant agents and genetic engineering, or transplantation of younger MSC. Nevertheless, these strategies may have the drawback of the adverse effects of prolonged use of the different drugs used or, where appropriate, those of cell therapy. In this review, we propose the new strategy of "Exogenous Restitution of Intercellular Signalling of Stem Cells" (ERISSC). This concept is based on the potential use of secretome from MSC, which are composed of molecules such as growth factors, cytokines, and extracellular vesicles and have the same biological effects as their parent cells. To face this cell-free regenerative therapy challenge, we have to clarify key strategy aspects, such as establishing tools that allow us a more precise diagnosis of aging frailty in order to identify the therapeutic requirements adapted to each case, identify the ideal type of MSC in the context of the functional heterogeneity of these cellular populations, to optimize the mass production and standardization of the primary materials (cells) and their secretome-derived products, to establish the appropriate methods to validate the anti-aging effects and to determine the most appropriate route of administration for each case.

Bone marrow mesenchymal stromal cells for diabetes therapy: touch, fuse, and fix?

Bone marrow mesenchymal stromal cells (BM-MSCs) have anti-inflammatory and pro-survival properties. Naturally, they do not express human leukocyte antigen class II surface antigens and have immunosuppressive capabilities. Together with their relatively easy accessibility and expansion, they are an attractive tool for organ support in transplantation and regenerative therapy. Autologous BM-MSC transplantation alone or together with transplanted islets improves β-cell function, graft survival, and glycemic control in diabetes. Albeit MSCs’ capacity to transdifferentiate into β-cell is limited, their protective effects are mediated mainly by paracrine mechanisms through BM-MSCs circulating through the body. Direct cell–cell contact and spontaneous fusion of BM-MSCs with injured cells, although at a very low rate, are further mechanisms of their supportive effect and for tissue regeneration. Diabetes is a disease of long-term chronic inflammation and cell therapy requires stable, highly functional cells. Several tools and protocols have been developed by mimicking natural fusion events to induce and accelerate fusion in vitro to promote β-cell-specific gene expression in fused cells. BM-MSC-islet fusion before transplantation may be a strategy for long-term islet survival and improved function. This review discusses the cell-protective and anti-inflammatory characteristics of BM-MSCs to boost highly functional insulin-producing cells in vitro and in vivo, and the efficacy of their fusion with β-cells as a path to promote β-cell regeneration.

Safety and Clinical Efficacy of Mesenchymal Stem Cell Treatment in Traumatic Spinal Cord Injury, Multiple Sclerosis and Ischemic Stroke - A Systematic Review and Meta-Analysis

Background

Mesenchymal stem cells (MSCs) is an attractive candidate in regenerative research and clinical trials have assessed their therapeutic potential in different neurological conditions with disparate etiologies. In this systematic review, we aimed to assess safety and clinical effect of MSC treatment in traumatic spinal cord injury (TSCI), multiple sclerosis (MS) and ischemic stroke (IS).

Methods

A systematic search was performed 2021-12-10 in MEDLINE, EMBASE, Web of Science and Cochrane where clinical studies assessing MSC treatment in TSCI, MS or IS were included. Studies without control group were excluded for efficacy analysis, but included in the safety analysis. For efficacy, AIS score, EDSS score and mRS were used as clinical endpoints and assessed in a meta-analysis using the random effects model.

Findings

Of 5,548 identified records, 54 studies were included. Twenty-six studies assessed MSC treatment in TSCI, 14 in MS and nine in IS, of which seven, seven and five studies were controlled, respectively. There were seven serious adverse events (SAEs), of which four were related to the surgical procedure and included one death due to complications following the implantation of MSCs. Three SAEs were considered directly related to the MSC treatment and all these had a transient course. In TSCI, a meta-analysis showed no difference in conversion from AIS A to C and a trend toward more patients treated with MSCs improving from AIS A to B as compared to controls (p = 0.05). A subgroup analysis performed per protocol, showed more MSC treated patients improving from AIS A to C in studies including patients within 8 weeks after injury (p = 0.04). In MS and IS, there were no significant differences in clinical outcomes between MSC treated patients and controls as measured by EDSS and mRS, respectively.

Interpretation

MSC-treatment is safe in patients with TSCI, MS and IS, although surgical implantation of MSC led to one fatal outcome in TSCI. There was no clear clinical benefit of MSC treatment, but this is not necessarily a proof of inefficacy due to the low number of controlled studies. Future studies assessing efficacy of MSC treatment should aim to do this in randomized, controlled studies.

Aging and “rejuvenation” of resident stem cells — a new way to active longevity?

This review presents the current data on the methodology for assessing the biological and epigenetic age, describes the concept of the epigenetic clock, and characterizes the main types of resident stem cells and the specifics of their aging. It has been shown that age-related changes in organs and tissues, as well as age-related diseases, are largely due to the aging of resident stem cells. The latter represent an attractive target for cell rejuvenation, as they can be isolated, cultured ex vivo, modified, and re-introduced into the resident niches. Two main methodologies for the cellular rejuvenation are presented: genetic reprogramming with zeroing the age of a cell using transient expression of transcription factors, and various approaches to epigenetic rejuvenation. The close relationship between aging, regeneration, and oncogenesis, and between these factors and the functioning of resident stem cell niches requires further precision studies, which, we are sure, can result in the creation of an effective anti-aging strategy and prolongation of human active life.

Electromagnetic field exposure as a plausible approach to enhance the proliferation and differentiation of mesenchymal stem cells in clinically relevant scenarios

Mesenchymal stem/stromal cell (MSC)‍-based therapy has been regarded as one of the most revolutionary breakthroughs in the history of modern medicine owing to its myriad of immunoregulatory and regenerative properties. With the rapid progress in the fields of osteo- and musculoskeletal therapies, the demand for MSC-based treatment modalities is becoming increasingly prominent. In this endeavor, researchers around the world have devised new and innovative techniques to support the proliferation of MSCs while minimizing the loss of hallmark features of stem cells. One such example is electromagnetic field (EMF) exposure, which is an alternative approach with promising potential. In this review, we present a critical discourse on the efficiency, practicability, and limitations of some of the relevant methods, with insurmountable evidence backing the implementation of EMF as a feasible strategy for the clinically relevant expansion of MSCs.

Safety, tolerability, and activity of mesenchymal stem cells versus placebo in multiple sclerosis (MESEMS): a phase 2, randomised, double-blind crossover trial

BACKGROUND

Mesenchymal stem cells (MSCs), also known as mesenchymal stromal cells, have been proposed as a promising therapeutic option for people with multiple sclerosis on the basis of their immunomodulatory and neuroprotective properties. The MEsenchymal StEm cells for Multiple Sclerosis (MESEMS) study was devised to evaluate the safety, tolerability, and activity of autologous MSCs derived from bone marrow and infused intravenously in patients with active multiple sclerosis.

METHODS

MESEMS is a randomised phase 2 trial done at 15 sites in nine countries. Patients (aged 18-50 years) with active relapsing-remitting or progressive multiple sclerosis were included if they had a disease duration of 2-15 years since onset of multiple sclerosis and an Expanded Disability Status Scale score of 2·5-6·5. Patients were randomly assigned (1:1), according to a crossover design, to receive a single intravenous dose of autologous bone marrow-derived MSCs followed by placebo at week 24, or to receive placebo followed by autologous MSCs at week 24, with a follow-up visit at week 48. Primary objectives were to test safety and activity of MSC treatment. The primary safety endpoint was to assess the number and severity of adverse events within each treatment arm. The primary efficacy endpoint was the number of gadolinium-enhancing lesions (GELs) counted over week 4, 12, and 24 compared between treatment groups. The primary efficacy endpoint was assessed in the full analyis set, after all participants completed the week 24 visit. Efficacy endpoints were evaluated using a predefined statistical testing procedure. Safety was monitored throughout the study by recording vital signs and adverse events at each visit.

FINDINGS

From July 16, 2012, until July 31, 2019, 144 patients were randomly assigned to first receive early intravenous infusion of autologous bone marrow-derived MSCs (n=69) or placebo (n=75). MSC treatment did not meet the primary endpoint of efficacy on the total number of GELs accumulated from baseline to week 24 (rate ratio [RR] 0·94, 95% CI 0·58-1·50; p=0·78). 213 adverse events were recorded, similarly distributed between groups (93 cases recorded in 35 [51%] of 69 patients treated first with MSCs vs 120 cases in 42 [56%] of 75 patients infused first with placebo). The most frequent adverse events reported were infection and infestations, with a total of 54 (25%) of 213 adverse events (18 [19%] of 93 in the early-MSC group and 36 [30%] of 120 in the delayed-MSC group). Nine serious adverse events were reported in seven patients treated with placebo versus none in the MSC group. All serious adverse events were considered to be unrelated to the treatment infusion. No deaths were reported during the study.

INTERPRETATION

Bone marrow-derived MSC treatment was safe and well tolerated but did not show an effect on GELs, an MRI surrogate marker of acute inflammation, in patients with active forms of multiple sclerosis, at week 24. Thus, this study does not support the use of bone marrow-derived MSCs to treat active multiple sclerosis. Further studies should address the effect of MSCs on parameters related to tissue repair.

FUNDING

Fondazione Italiana Sclerosi Multipla (FISM), the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS), and the Multiple Sclerosis International Federation (MSIF) for centralised activities. Individual trials participating in the MESEMS network are funded by the following agencies: FISM and Compagnia di San Paolo (Italy); The Danish Multiple Sclerosis Society, The Toyota Foundation, and Danish Blood Donors' Research Foundation (Denmark); the Spanish Health Research Institute Carlos 3 and the Andalusian Public Foundation Progreso y Salud (Spain); the Royan Institute for Stem Cell Biology and Technology (Iran); the Spinal Cord Injury and Tissue Regeneration Centre Salzburg, Paracelsus Medical University, and Salzburg (Austria); the Fondation pour l'aide à la recherche sur la sclérose en plaques (ARSEP), French Muscular Dystrophy Association (AFM)-Telethon (France); the UK Multiple Sclerosis Society and the UK Stem Cell Foundation (UK); and the Multiple Sclerosis Society of Canada and The Multiple Sclerosis Scientific Research Foundation and Research Manitoba (Canada).

Epigenetic Clock and Circadian Rhythms in Stem Cell Aging and Rejuvenation

This review summarizes the current understanding of the interaction between circadian rhythms of gene expression and epigenetic clocks characterized by the specific profile of DNA methylation in CpG-islands which mirror the senescence of all somatic cells and stem cells in particular. Basic mechanisms of regulation for circadian genes CLOCK-BMAL1 as well as downstream clock-controlled genes (ССG) are also discussed here. It has been shown that circadian rhythms operate by the finely tuned regulation of transcription and rely on various epigenetic mechanisms including the activation of enhancers/suppressors, acetylation/deacetylation of histones and other proteins as well as DNA methylation. Overall, up to 20% of all genes expressed by the cell are subject to expression oscillations associated with circadian rhythms. Additionally included in the review is a brief list of genes involved in the regulation of circadian rhythms, along with genes important for cell aging, and oncogenesis. Eliminating some of them (for example, Sirt1) accelerates the aging process, while the overexpression of Sirt1, on the contrary, protects against age-related changes. Circadian regulators control a number of genes that activate the cell cycle (Wee1, c-Myc, p20, p21, and Cyclin D1) and regulate histone modification and DNA methylation. Approaches for determining the epigenetic age from methylation profiles across CpG islands in individual cells are described. DNA methylation, which characterizes the function of the epigenetic clock, appears to link together such key biological processes as regeneration and functioning of stem cells, aging and malignant transformation. Finally, the main features of adult stem cell aging in stem cell niches and current possibilities for modulating the epigenetic clock and stem cells rejuvenation as part of antiaging therapy are discussed.

Mesenchymal stromal cells: Putative microenvironmental modulators become cell therapy

An exceptional safety profile has been shown in a large number of cell therapy clinical trials that use mesenchymal stromal cells (MSCs). However, reliable potency assays are still lacking to predict MSC immunosuppressive efficacy in the clinical setting. Nevertheless, MSCs are approved in Japan and Europe for the treatment of graft-versus-host and Crohn's fistular diseases, but not in the United States for any clinical indication. We discuss potential mechanisms of action for the therapeutic effects of MSC transplantation, experimental models that dissect tissue modulating function of MSCs, and approaches for identifying MSC effects in vivo by integrating biomarkers of disease and MSC activity.

Stem Cell Therapies for Progressive Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by demyelination and axonal degeneration. MS patients typically present with a relapsing-remitting (RR) disease course, manifesting as sporadic attacks of neurological symptoms including ataxia, fatigue, and sensory impairment. While there are several effective disease-modifying therapies able to address the inflammatory relapses associated with RRMS, most patients will inevitably advance to a progressive disease course marked by a gradual and irreversible accrual of disabilities. Therapeutic intervention in progressive MS (PMS) suffers from a lack of well-characterized biological targets and, hence, a dearth of successful drugs. The few medications approved for the treatment of PMS are typically limited in their efficacy to active forms of the disease, have little impact on slowing degeneration, and fail to promote repair. In looking to address these unmet needs, the multifactorial therapeutic benefits of stem cell therapies are particularly compelling. Ostensibly providing neurotrophic support, immunomodulation and cell replacement, stem cell transplantation holds substantial promise in combatting the complex pathology of chronic neuroinflammation. Herein, we explore the current state of preclinical and clinical evidence supporting the use of stem cells in treating PMS and we discuss prospective hurdles impeding their translation into revolutionary regenerative medicines.

Interplay between mesenchymal stromal cells and immune system: clinical applications in immune-related diseases

Mesenchymal stromal cells (MSCs) are a mesodermal stem cell population, with known self-renewal and multilineage differentiation properties. In the last century, MSCs have been widely used in regenerative medicine and tissue engineering approaches. MSCs initially were isolated from bone marrow aspirates, but currently have been identified in a great number of tissues of the human body. Besides their utilization in regenerative medicine, MSCs possess significant immunoregulatory/immunosuppressive properties, through interaction with the cells of innate and adaptive immunity. MSCs can exert their immunomodulatory properties with either cell-cell contact or via paracrine secretion of molecules, such as cytokines, growth factors and chemokines. Of particular importance, the MSCs’ immunomodulatory properties are explored as promising therapeutic strategies in immune-related disorders, such as autoimmune diseases, graft versus host disease, cancer. MSCs may also have an additional impact on coronavirus disease-19 (COVID-19), by attenuating the severe symptoms of this disorder. Nowadays, a great number of clinical trials, of MSC-mediated therapies are evaluated for their therapeutic potential. In this review, the current knowledge on cellular and molecular mechanisms involved in MSC-mediated immunomodulation were highlighted. Also, the most important aspects, regarding their potential application in immune-related diseases, will be highlighted. The broad application of MSCs has emerged their role as key immunomodulatory players, therefore their utilization in many disease situations is full of possibilities for future clinical treatment.

Safety and immunological proof-of-concept following treatment with tolerance-inducing cell products in patients with autoimmune diseases or receiving organ transplantation: A systematic review and meta-analysis of clinical trials

In the past years, translational approaches have led to early-stage clinical trials assessing safety and efficacy of tolerance-inducing cell-based treatments in patients. This review aims to determine if tolerance-inducing cell-based therapies, including dendritic cells, regulatory T cells and mesenchymal stem cells, are safe in adult patients who underwent organ transplantation or in those with autoimmune diseases, including multiple sclerosis, diabetes mellitus type 1, Crohn's disease and rheumatoid arthritis. Immunological and clinical outcomes were reviewed, to provide evidence for proof-of-concept and efficacy. To summarize the current knowledge, a systematic review and meta-analysis were conducted. A total of 8906 records were reviewed by 2 independent assessors and 48 records were included in the final quantitative analysis. The overall frequency of serious adverse events was low: 0.018 (95% CI: 0.006-0.051). Immunological outcomes could not be assessed quantitatively because of heterogeneity in outcome assessments and description as well as lack of individual data. Most randomized controlled studies were at a medium risk of bias due to open-label treatment without masking of assessors and/or patients to the intervention. In conclusion, tolerance-inducing cell-based therapies are safe. We advocate for harmonization of study protocols of trials investigating cell-based therapies, adverse event reporting and systematic inclusion of immunological outcome measures in clinical trials evaluating tolerance-inducingcell-basedtreatment. Registration: PROSPERO, registration number CRD42020170557.

Mesenchymal Stem Cells for Neurological Disorders

Neurological disorders are becoming a growing burden as society ages, and there is a compelling need to address this spiraling problem. Stem cell-based regenerative medicine is becoming an increasingly attractive approach to designing therapies for such disorders. The unique characteristics of mesenchymal stem cells (MSCs) make them among the most sought after cell sources. Researchers have extensively studied the modulatory properties of MSCs and their engineering, labeling, and delivery methods to the brain. The first part of this review provides an overview of studies on the application of MSCs to various neurological diseases, including stroke, traumatic brain injury, spinal cord injury, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, Parkinson's disease, and other less frequently studied clinical entities. In the second part, stem cell delivery to the brain is focused. This fundamental but still understudied problem needs to be overcome to apply stem cells to brain diseases successfully. Here the value of cell engineering is also emphasized to facilitate MSC diapedesis, migration, and homing to brain areas affected by the disease to implement precision medicine paradigms into stem cell-based therapies.

Novel cell-based therapies in inflammatory bowel diseases: the established concept, promising results

Inflammatory bowel diseases (IBDs) are chronic and relapsing disorders that affect the quality of life in many individuals around the world. Over the past few years, the prevalence of IBDs is substantially rising which might pose a considerable social and economic burden on health systems. Progresses in the management of chronic inflammatory diseases lead to prolonged remission phase and decreased hospitalization rate. However, during treatment, many patients become refractory to conventional therapies. Recently, advanced approaches using somatic cell therapy medicinal products (SCTMPs) including immune and stem cell-based therapies have drawn many researchers' attentions. Promising results from recent trials, alongside with the emerging market indicated that these therapeutic approaches could be an alternative and promising treatment to conventional therapies. In this review, we will discuss recent advances in cell-based therapies, which have been developed for treatment of IBDs. In addition, the global emerging market and the novel products in this field are highlighted.

Mesenchymal stromal cells as potential immunomodulatory players in severe acute respiratory distress syndrome induced by SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus-2 and the related coronavirus disease-19 (COVID-19) is a worldwide emerging situation, which was initially reported in December 2019 in Wuhan, China. Currently, more than 7258842 new cases, and more than 411879 deaths have been reported globally. This new highly transmitted coronavirus is responsible for the development of severe acute respiratory distress syndrome. Due to this disorder, a great number of patients are hospitalized in the intensive care unit followed by connection to extracorporeal membrane oxygenation for breath supporting and survival. Severe acute respiratory distress syndrome is mostly accompanied by the secretion of proinflammatory cytokines, including interleukin (IL)-2, IL-6, IL-7, granulocyte colony-stimulating factor (GSCF), interferon-inducible protein 10 (IP10), monocyte chemotactic protein-1 (MCP1), macrophage inflammatory protein 1A (MIP1A), and tumor necrosis factor alpha (TNF-α), an event which is known as "cytokine storm". Further disease pathology involves a generalized modulation of immune responses, leading to fatal multiorgan failure. Currently, no specific treatment or vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been developed. Mesenchymal stromal cells (MSCs), which are known for their immunosuppressive actions, could be applied as an alternative co-therapy in critically-ill COVID-19 patients. Specifically, MSCs can regulate the immune responses through the conversion of Th1 to Th2, activation of M2 macrophages, and modulation of dendritic cells maturation. These key immunoregulatory properties of MSCs may be exerted either by produced soluble factors or by cell-cell contact interactions. To date, several clinical trials have been registered to assess the safety, efficacy, and therapeutic potential of MSCs in COVID-19. Moreover, MSC treatment may be effective for the reversion of ground-glass opacity of damaged lungs and reduce the tissue fibrosis. Taking into account the multifunctional properties of MSCs, the proposed stem-cell-based therapy may be proven significantly effective in critically-ill COVID-19 patients. The current therapeutic strategy may improve the patient's overall condition and in parallel may decrease the mortality rate of the current disease.

Mesenchymal Stem Cell Senescence and Rejuvenation: Current Status and Challenges

Over the past decades, mesenchymal stem cell (MSC)-based therapy has been intensively investigated and shown promising results in the treatment of various diseases due to their easy isolation, multiple lineage differentiation potential and immunomodulatory effects. To date, hundreds of phase I and II clinical trials using MSCs have been completed and many are ongoing. Accumulating evidence has shown that transplanted allogeneic MSCs lose their beneficial effects due to immunorejection. Nevertheless, the function of autologous MSCs is adversely affected by age, a process termed senescence, thus limiting their therapeutic potential. Despite great advances in knowledge, the potential mechanisms underlying MSC senescence are not entirely clear. Understanding the molecular mechanisms that contribute to MSC senescence is crucial when exploring novel strategies to rejuvenate senescent MSCs. In this review, we aim to provide an overview of the biological features of senescent MSCs and the recent progress made regarding the underlying mechanisms including epigenetic changes, autophagy, mitochondrial dysfunction and telomere shortening. We also summarize the current approaches to rejuvenate senescent MSCs including gene modification and pretreatment strategies. Collectively, rejuvenation of senescent MSCs is a promising strategy to enhance the efficacy of autologous MSC-based therapy, especially in elderly patients.

Mesenchymal Stem/Stromal Cells in Immunity and Disease: A Better Understanding for an Improved Use

In this Special Issue, directed and supervised by Dr. Mehdi Najar, a collection of basic research articles and reviews, on the state of the art of Mesenchymal Stem/Stromal Cells (MSCs) immune biology, is presented. Among the major goals of this Special Issue is the presentation of an update about the immunomodulatory properties of MSCs and their capacity to respond to tissue microenvironment changes. MSCs hold great promise in the field of immunotherapy and regenerative medicine. Accordingly, a better understanding of MSC immune biology will improve their therapeutic value and use.