Human adipose tissue-derived mesenchymal stem cells abrogate plasmablast formation and induce regulatory B cells independently of T helper cells

International Society for Cell and Gene Therapy Clinical Translation Committee recommendations on mesenchymal stromal cells in graft-versus-host disease: easy manufacturing is faced with standardizing and commercialization challenges

Mesenchymal stromal cells (MSCs) have been used in multiple clinical trials for steroid-refractory moderate-severe (grade II-IV) acute graft-versus-host disease (aGVHD) across the world over the last two decades. Despite very promising results in a variety of trials, it failed to get widespread approval by regulatory agencies such as the U.S. Food and Drug Administration and the European Medicines Agency. What lessons can we learn from this for future studies on MSCs and other cell therapy products? Broad heterogeneity among published trials using MSCs in aGVHD was likely the core problem. We propose a standardized approach in regards to donor-related factors, MSCs-related characteristics, as well as clinical trial design, to limit heterogeneity in trials for aGVHD and to fulfill the requirements of regulatory agencies. This approach may be expanded beyond MSCs to other Cell and Gene therapy products and trials in other diseases.

B Cell-mediated Immune Regulation and the Quest for Transplantation Tolerance

Pathophysiologic function of B cells in graft rejection has been well recognized in transplantation. B cells promote alloantigen-specific T-cell response and secrete antibodies that can cause antibody-mediated graft failures and rejections. Therefore, strategies targeting B cells, for example, B-cell depletion, have been used for the prevention of both acute and chronic rejections. Interestingly, however, recent mounting evidence indicates that subsets of B cells yet to be further identified can display potent immune regulatory functions, and they contribute to transplantation tolerance and operational tolerance in both experimental and clinical settings, respectively. In this review, we integrate currently available information on B-cell subsets, including T-cell Ig domain and mucin domain 1-positive transitional and T-cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domain-positive memory B cells, displaying immune regulatory functions, with a focus on transplantation tolerance, by analyzing their mechanisms of action. In addition, we will discuss potential T-cell Ig domain and mucin domain 1-positive and T-cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domain-positive B cell-based strategies for the enhancement of operational tolerance in transplantation patients.

Dipeptidyl peptidase-4 marks distinct subtypes of human adipose stromal/stem cells with different hepatocyte differentiation and immunoregulatory properties

BACKGROUND

Human adipose-derived stromal/stem cells (hASCs) play important roles in regenerative medicine and numerous inflammatory diseases. However, their cellular heterogeneity limits the effectiveness of treatment. Understanding the distinct subtypes of hASCs and their phenotypic implications will enable the selection of appropriate subpopulations for targeted approaches in regenerative medicine or inflammatory diseases.

METHODS

hASC subtypes expressing dipeptidyl peptidase-4 (DPP4) were identified via fluorescence-activated cell sorting (FACS) analysis. DPP4 expression was knocked down in DPP4+ hASCs via DPP4 siRNA. The capacity for proliferation, hepatocyte differentiation, inflammatory factor secretion and T-cell functionality regulation of hASCs from DPP4-, DPP4+, and control siRNA-treated DPP4+ hASCs and DPP4 siRNA-treated DPP4+ hASCs were assessed.

RESULTS

DPP4+ hASCs and control siRNA-treated DPP4+ hASCs presented a lower proliferative capacity but greater hepatocyte differentiation capacity than DPP4- hASCs and DPP4 siRNA-treated DPP4+ hASCs. Both DPP4+ hASCs and DPP4- hASCs secreted high levels of vascular endothelial growth factor-A (VEGF-A), monocyte chemoattractant protein-1 (MCP-1), and interleukin 6 (IL-6), whereas the levels of other factors, including matrix metalloproteinase (MMP)-1, eotaxin-3, fractalkine (FKN, CX3CL1), growth-related oncogene-alpha (GRO-alpha, CXCL1), monokine induced by interferon-gamma (MIG), macrophage inflammatory protein (MIP)-1beta, and macrophage colony-stimulating factor (M-CSF), were significantly greater in the supernatants of DPP4+ hASCs than in those of DPP4- hASCs. Exposure to hASC subtypes and their conditioned media triggered changes in the secreted cytokine profiles of T cells from healthy donors. The percentage of functional T cells that secreted factors such as MIP-1beta and IL-8 increased when these cells were cocultured with DPP4+ hASCs. The percentage of polyfunctional CD8+ T cells that secreted multiple factors, such as IL-17A, tumour necrosis factor alpha (TNF-α) and TNF-β, decreased when these cells were cocultured with supernatants derived from DPP4+ hASCs.

CONCLUSIONS

DPP4 may regulate proliferation, hepatocyte differentiation, inflammatory cytokine secretion and T-cell functionality of hASCs. These data provide a key foundation for understanding the important role of hASC subpopulations in the regulation of T cells, which may be helpful for future immune activation studies and allow them to be customized for clinical application.

Exogenous MSC based tissue regeneration: a review of immuno-protection strategies from biomaterial scaffolds

Mesenchymal stem cell (MSC)-based tissue engineering holds great potential for regenerative medicine as a means of replacing damaged or lost tissues to restore their structure and function. However, the efficacy of MSC-based regeneration is frequently limited by the low survival rate and limited survival time of transplanted MSCs. Despite the inherent immune privileges of MSCs, such as low expression of major histocompatibility complex antigens, tolerogenic properties, local immunosuppressive microenvironment creation, and induction of immune tolerance, immune rejection remains a major obstacle to their survival and regenerative potential. Evidence suggests that immune protection strategies can enhance MSC therapeutic efficacy by prolonging their survival and maintaining their biological functions. Among various immune protection strategies, biomaterial-based scaffolds or cell encapsulation systems that mediate the interaction between transplanted MSCs and the host immune system or spatially isolate MSCs from the immune system for a specific time period have shown great promise. In this review, we provide a comprehensive overview of these biomaterial-based immune protection strategies employed for exogenous MSCs, highlighting the crucial role of modulating the immune microenvironment. Each strategy is critically examined, discussing its strengths, limitations, and potential applications in MSC-based tissue engineering. By elucidating the mechanisms behind immune rejection and exploring immune protection strategies, we aim to address the challenges faced by MSC-based tissue engineering and pave the way for enhancing the therapeutic outcomes of MSC therapies. The insights gained from this review will contribute to the development of more effective strategies to protect transplanted MSCs from immune rejection and enable their successful application in regenerative medicine.

Cause and consequence of heterogeneity in human mesenchymal stem cells: Challenges in clinical application

Human mesenchymal stem cells (hMSCs) are mesoderm-derived adult stem cells with self-proliferation capacity, pluripotent differentiation potency, and excellent histocompatibility. These advantages make hMSCs a promising tool in clinical application. However, the majority of clinical trials using hMSC therapy for diverse human diseases do not achieve expectations, despite the prospective pre-clinical outcomes in animal models. This is partly attributable to the intrinsic heterogeneity of hMSCs. In this review, the cause of heterogeneity in hMSCs is systematically discussed at multiple levels, including isolation methods, cultural conditions, donor-to-donor variation, tissue sources, intra-tissue subpopulations, etc. Additionally, the effect of hMSCs heterogeneity on the contrary role in tumor progression and immunomodulation is also discussed. The attempts to understand the cellular heterogeneity of hMSCs and its consequences are important in supporting and improving therapeutic strategies for hMSCs.

Cell-Based Therapy and Genome Editing as Emerging Therapeutic Approaches to Treat Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the joints. Although much remains unknown about the pathogenesis of RA, there is evidence that impaired immune tolerance and the development of RA are related. And it is precisely the restoration of immune tolerance at the site of the inflammation that is the ultimate goal of the treatment of RA. Over the past few decades, significant progress has been made in the treatment of RA, with higher rates of disease remission and improved long-term outcomes. Unfortunately, despite these successes, the proportion of patients with persistent, difficult-to-treat disease remains high, and the task of improving our understanding of the basic mechanisms of disease development and developing new ways to treat RA remains relevant. This review focuses on describing new treatments for RA, including cell therapies and gene editing technologies that have shown potential in preclinical and early clinical trials. In addition, we discuss the opportunities and limitations associated with the use of these new approaches in the treatment of RA.

Advances and clinical challenges of mesenchymal stem cell therapy

In recent years, cell therapy has provided desirable properties for promising new drugs. Mesenchymal stem cells are promising candidates for developing genetic engineering and drug delivery strategies due to their inherent properties, including immune regulation, homing ability and tumor tropism. The therapeutic potential of mesenchymal stem cells is being investigated for cancer therapy, inflammatory and fibrotic diseases, among others. Mesenchymal stem cells are attractive cellular carriers for synthetic nanoparticles for drug delivery due to their inherent homing ability. In this review, we comprehensively discuss the various genetic and non-genetic strategies of mesenchymal stem cells and their derivatives in drug delivery, tumor therapy, immune regulation, tissue regeneration and other fields. In addition, we discuss the current limitations of stem cell therapy and the challenges in clinical translation, aiming to identify important development areas and potential future directions.

TSG-6 Is Involved in Fibrous Structural Remodeling after the Injection of Adipose-derived Stem Cells

Background

Although aesthetic treatments can rejuvenate the skin, they often cause specific forms of tissue damage. Unlike wounding, which typically results in fibrotic scar tissue, damage from aesthetic treatments induces a distinct histological rejuvenation. The mechanisms that drive this rejuvenation are not yet fully understood. Here, we were interested in cellular responses following aesthetic treatments injecting adipose-derived stem cells (ASCs) subcutaneously. Through investigation with an ex vivo experimental model, a key gene was identified that orchestrates fibrous structural changes and tissue remodeling.

Methods

Using fresh human subcutaneous adipose tissue co-cultured with ASCs, the changes in the fibrous architecture of the tissue were sequentially mapped. The key regulatory genes involved in remodeling were identified using gene expression and computational analyses.

Results

We identified the regulatory elements that are crucial for tissue remodeling. Among those, we found that tumor necrosis factor-stimulated gene-6 (TSG-6) is a paracrine mediator essential for the collagen activity. It not only alleviates tissue inflammation but also promotes collagen replacement ex vivo. This is primarily achieved by inhibiting the formation of neutrophil extracellular traps, which are known to promote fibrosis.

Conclusions

TSG-6 is a key factor modulating tissue inflammation. As our results demonstrate, after ASCs treatment, this factor directs skin healing away from fibrosis by reducing neutrophil extracellular trap formation in subcutaneous adipose tissue and promotes fibrous rejuvenation.

Mesenchymal Stem Cells-Involved Strategies for Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the joints and bone destruction. Because of systemic administration and poor targeting, traditional anti-rheumatic drugs have unsatisfactory treatment efficacy and strong side effects, including myelosuppression, liver or kidney function damage, and malignant tumors. Consequently, mesenchymal stem cells (MSCs)-involved therapy is proposed for RA therapy as a benefit of their immunosuppressive and tissue-repairing effects. This review summarizes the progress of MSCs-involved RA therapy through suppressing inflammation and promoting tissue regeneration and predicts their potential clinical application.

Mesenchymal stromal cells (MSCs) as a therapeutic agent of inflammatory disease and infectious COVID-19 virus: live or dead mesenchymal?

The COVID-19 infection is a worldwide disease that causes numerous immune-inflammatory disorders, tissue damage, and lung dysfunction. COVID-19 vaccines, including those from Pfizer, AstraZeneca, and Sinopharm, are available globally as effective interventions for combating the disease. The severity of COVID-19 can be most effectively reduced by mesenchymal stromal cells (MSCs) because they possess anti-inflammatory activity and can reverse lung dysfunction. MSCs can be harvested from various sources, such as adipose tissue, bone marrow, peripheral blood, inner organs, and neonatal tissues. The regulation of inflammatory cytokines is crucial in inhibiting inflammatory diseases and promoting the presence of anti-inflammatory cytokines for infectious diseases. MSCs have been employed as therapeutic agents for tissue damage, diabetes, autoimmune diseases, and COVID-19 patients. Our research aimed to determine whether live or dead MSCs are more suitable for the treatment of COVID-19 patients. Our findings concluded that dead MSCs, when directly administered to the patient, offer advantages over viable MSCs due to their extended presence and higher levels of immune regulation, such as T-reg, B-reg, and IL-10, compared to live MSCs. Additionally, dead and apoptotic MSCs are likely to be more readily captured by monocytes and macrophages, prolonging their presence compared to live MSCs.

Enhancing Immunomodulatory Function of Mesenchymal Stromal Cells by Hydrogel Encapsulation

Mesenchymal stromal cells (MSCs) showcase remarkable immunoregulatory capabilities in vitro, positioning them as promising candidates for cellular therapeutics. However, the process of administering MSCs and the dynamic in vivo environment may impact the cell-cell and cell-matrix interactions of MSCs, consequently influencing their survival, engraftment, and their immunomodulatory efficacy. Addressing these concerns, hydrogel encapsulation emerges as a promising solution to enhance the therapeutic effectiveness of MSCs in vivo. Hydrogel, a highly flexible crosslinked hydrophilic polymer with a substantial water content, serves as a versatile platform for MSC encapsulation. Demonstrating improved engraftment and heightened immunomodulatory functions in vivo, MSCs encapsulated by hydrogel are at the forefront of advancing therapeutic outcomes. This review delves into current advancements in the field, with a focus on tuning various hydrogel parameters to elucidate mechanistic insights and elevate functional outcomes. Explored parameters encompass hydrogel composition, involving monomer type, functional modification, and co-encapsulation, along with biomechanical and physical properties like stiffness, viscoelasticity, topology, and porosity. The impact of these parameters on MSC behaviors and immunomodulatory functions is examined. Additionally, we discuss potential future research directions, aiming to kindle sustained interest in the exploration of hydrogel-encapsulated MSCs in the realm of immunomodulation.

Factors Defining Human Adipose Stem/Stromal Cell Immunomodulation in Vitro

Human adipose tissue-derived stem/stromal cells (hASCs) are adult multipotent mesenchymal stem/stromal cells with immunomodulatory capacities. Here, we present up-to-date knowledge on the impact of different experimental and donor-related factors on hASC immunoregulatory functions in vitro. The experimental determinants include the immunological status of hASCs relative to target immune cells, contact vs. contactless interaction, and oxygen tension. Factors such as the ratio of hASCs to immune cells, the cellular context, the immune cell activation status, and coculture duration are also discussed. Conditioning of hASCs with different approaches before interaction with immune cells, hASC culture in xenogenic or xenofree culture medium, hASC culture in two-dimension vs. three-dimension with biomaterials, and the hASC passage number are among the experimental parameters that greatly may impact the hASC immunosuppressive potential in vitro, thus, they are also considered. Moreover, the influence of donor-related characteristics such as age, sex, and health status on hASC immunomodulation in vitro is reviewed. By analysis of the literature studies, most of the indicated determinants have been investigated in broad non-standardized ranges, so the results are not univocal. Clear conclusions cannot be drawn for the fine-tuned scenarios of many important factors to set a standard hASC immunopotency assay. Such variability needs to be carefully considered in further standardized research. Importantly, field experts' opinions may help to make it clearer.

Immunomodulatory Effects of Primed Tonsil-Derived Mesenchymal Stem Cells on Atopic Dermatitis via B Cell Regulation

Mesenchymal stem cells (MSCs) ameliorate T-and B cell-mediated immune responses. In particular, tonsil-MSCs (T-MSCs) are attractive candidates for practical and clinical applications because of their ease of acquisition and relatively low immunogenicity compared with other MSC sources. The use of MSCs as a therapeutic tool in atopic dermatitis (AD) has been investigated, but that of T-MSCs remains to be explored. Therefore, we investigated the immunomodulatory effects of primed T-MSCs in AD pathogenesis. In our animal study, primed T-MSCs showed greater immunological suppressive effects than naïve T-MSCs. Additionally, in vitro, the proliferation of B cells was downregulated by the addition of primed T-MSCs compared with naïve T-MSCs. The activation of B cells to differentiate into antibody-secreting cells and produce IgE was also reduced when primed T-MSCs were added. Moreover, under CD40-knockdown conditions, we found that CD40 in primed T-MSCs played a critical role as a regulator of B cell activation and was mediated by the non-canonical NF-κB pathway. Therefore, our findings suggest a promising role for primed T-MSCs in the treatment of AD by regulating B cell-mediated inflammatory responses, which are dependent on CD40 expression on primed T-MSCs mediated through the non-canonical NF-κB pathway.

Acoustofluidic Interfaces for the Mechanobiological Secretome of MSCs

While mesenchymal stem cells (MSCs) have gained enormous attention due to their unique properties of self-renewal, colony formation, and differentiation potential, the MSC secretome has become attractive due to its roles in immunomodulation, anti-inflammatory activity, angiogenesis, and anti-apoptosis. However, the precise stimulation and efficient production of the MSC secretome for therapeutic applications are challenging problems to solve. Here, we report on Acoustofluidic Interfaces for the Mechanobiological Secretome of MSCs: AIMS. We create an acoustofluidic mechanobiological environment to form reproducible three-dimensional MSC aggregates, which produce the MSC secretome with high efficiency. We confirm the increased MSC secretome is due to improved cell-cell interactions using AIMS: the key mediator N-cadherin was up-regulated while functional blocking of N-cadherin resulted in no enhancement of the secretome. After being primed by IFN-γ, the secretome profile of the MSC aggregates contains more anti-inflammatory cytokines and can be used to inhibit the pro-inflammatory response of M1 phenotype macrophages, suppress T cell activation, and support B cell functions. As such, the MSC secretome can be modified for personalized secretome-based therapies. AIMS acts as a powerful tool for improving the MSC secretome and precisely tuning the secretory profile to develop new treatments in translational medicine.

Stromal-Modulated Epithelial-to-Mesenchymal Transition in Cancer Cells

The ability of cancer cells to detach from the primary site and metastasize is the main cause of cancer- related death among all cancer types. Epithelial-to-mesenchymal transition (EMT) is the first event of the metastatic cascade, resulting in the loss of cell-cell adhesion and the acquisition of motile and stem-like phenotypes. A critical modulator of EMT in cancer cells is the stromal tumor microenvironment (TME), which can promote the acquisition of a mesenchymal phenotype through direct interaction with cancer cells or changes to the broader microenvironment. In this review, we will explore the role of stromal cells in modulating cancer cell EMT, with particular emphasis on the function of mesenchymal stromal/stem cells (MSCs) through the activation of EMT-inducing pathways, extra cellular matrix (ECM) remodeling, immune cell alteration, and metabolic rewiring.

Interactions of mesenchymal stromal/stem cells and immune cells following MSC-based therapeutic approaches in rheumatoid arthritis

Rheumatoid arthritis (RA) is considered to be a degenerative and progressive autoimmune disorder. Although several medicinal regimens are used to treat RA, potential adverse events such as metabolic disorders and increased risk of infection, as well as drug resistance in some patients, make it essential to find an effective and safe therapeutic approach. Mesenchymal stromal/stem cells (MSCs) are a group of non-hematopoietic stromal cells with immunomodulatory and inhibitory potential. These cells exert their regulatory properties through direct cell-to-cell interactions and paracrine effects on various immune and non-immune cells. As conventional therapeutic approaches for RA are limited due to their side effects, and some patients became refractory to the treatment, MSCs are considered as a promising alternative treatment for RA. In this review, we introduced various experimental and clinical studies conducted to evaluate the therapeutic effects of MSCs on animal models of arthritis and RA patients. Then, possible modulatory and suppressive effects of MSCs on different innate and adaptive immune cells, including dendritic cells, neutrophils, macrophages, natural killer cells, B lymphocytes, and various subtypes of T cells, were categorized and summarized. Finally, limitations and future considerations for the efficient application of MSCs as a therapeutic approach in RA patients were presented.

Mesenchymal stem cells influence monocyte/macrophage phenotype: Regulatory mode and potential clinical applications

Mesenchymal stem cells (MSCs) are pluripotent stem cells derived from a variety of tissues, such as umbilical cord, fat, and bone marrow. Today, MSCs are widely recognized for their prominent anti-inflammatory properties in a variety of acute and chronic inflammatory diseases. In inflammatory diseases, monocytes/macrophages are an important part of the innate immune response in the body, and the alteration of the inflammatory phenotype plays a crucial role in the secretion of pro-inflammatory/anti-inflammatory factors, the repair of injured sites, and the infiltration of inflammatory cells. In this review, starting from the effect of MSCs on the monocyte/macrophage phenotype, we have outlined in detail the process by which MSCs influence the transformation of the monocyte/macrophage inflammatory phenotype, emphasizing the central role of monocytes/macrophages in MSC-mediated anti-inflammatory and damage site repair. MSCs are phagocytosed by monocytes/macrophages in various physiological states, the paracrine effect of MSCs and mitochondrial transfer of MSCs to macrophages to promote the transformation of monocytes/macrophages into anti-inflammatory phenotypes. We also review the clinical applications of the MSCs-monocytes/macrophages system and describe novel pathways between MSCs and tissue repair, the effects of MSCs on the adaptive immune system, and the effects of energy metabolism levels on monocyte/macrophage phenotypic changes.

The functional effects of Piezo channels in mesenchymal stem cells

Mesenchymal stem cells (MSCs) are widely used in cell therapy, tissue engineering, and regenerative medicine because of their self-renewal, pluripotency, and immunomodulatory properties. The microenvironment in which MSCs are located significantly affects their physiological functions. The microenvironment directly or indirectly affects cell behavior through biophysical, biochemical, or other means. Among them, the mechanical signals provided to MSCs by the microenvironment have a particularly pronounced effect on their physiological functions and can affect osteogenic differentiation, chondrogenic differentiation, and senescence in MSCs. Mechanosensitive ion channels such as Piezo1 and Piezo2 are important in transducing mechanical signals, and these channels are widely distributed in sites such as skin, bladder, kidney, lung, sensory neurons, and dorsal root ganglia. Although there have been numerous studies on Piezo channels in MSCs in recent years, the function of Piezo channels in MSCs is still not well understood, and there has been no summary of their relationship to illustrate which physiological functions of MSCs are affected by Piezo channels and the possible underlying mechanisms. Therefore, based on the members, structures, and functions of Piezo ion channels and the fundamental information of MSCs, this paper focused on summarizing the advances in Piezo channels in MSCs from various tissue sources to provide new ideas for future research and practical applications of Piezo channels and MSCs.

Mesenchymal Stromal Cells: Heterogeneity and Therapeutical Applications

Mesenchymal stromal cells nowadays emerge as a major player in the field of regenerative medicine and translational research. They constitute, with their derived products, the most frequently used cell type in different therapies. However, their heterogeneity, including different subpopulations, the anatomic source of isolation, and high donor-to-donor variability, constitutes a major controversial issue that affects their use in clinical applications. Furthermore, the intrinsic and extrinsic molecular mechanisms underlying their self-renewal and fate specification are still not completely elucidated. This review dissects the different heterogeneity aspects of the tissue source associated with a distinct developmental origin that need to be considered when generating homogenous products before their usage for clinical applications.

Immunomodulatory Mechanisms and Therapeutic Potential of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are regarded as highly promising cells for allogeneic cell therapy, owing to their multipotent nature and ability to display potent and varied functions in different diseases. The functions of MSCs, including native immunomodulation, high self-renewal characteristic, and secretory and trophic properties, can be employed to improve the immune-modulatory functions in diseases. MSCs impact most immune cells by directly contacting and/or secreting positive microenvironmental factors to influence them. Previous studies have reported that the immunomodulatory role of MSCs is basically dependent on their secretion ability from MSCs. This review discusses the immunomodulatory capabilities of MSCs and the promising strategies to successfully improve the potential utilization of MSCs in clinical research.

Cellular nanovesicles for therapeutic immunomodulation: A perspective on engineering strategies and new advances

Cellular nanovesicles which are referred to as cell-derived, nanosized lipid bilayer structures, have emerged as a promising platform for regulating immune responses. Owing to their outstanding advantages such as high biocompatibility, prominent structural stability, and high loading capacity, cellular nanovesicles are suitable for delivering various immunomodulatory molecules, such as small molecules, nucleic acids, peptides, and proteins. Immunomodulation induced by cellular nanovesicles has been exploited to modulate immune cell behaviors, which is considered as a novel cell-free immunotherapeutic strategy for the prevention and treatment of diverse diseases. Here we review emerging concepts and new advances in leveraging cellular nanovesicles to activate or suppress immune responses, with the aim to explicate their applications for immunomodulation. We overview the general considerations and principles for the design of engineered cellular nanovesicles with tailored immunomodulatory activities. We also discuss new advances in engineering cellular nanovesicles as immunotherapies for treating major diseases.

Regulatory B Cells Contribute to the Clinical Response After Bone Marrow-Derived Mesenchymal Stromal Cell Infusion in Patients With Systemic Sclerosis

Mesenchymal stromal cells (MSCs) have recently emerged as an interesting therapeutic approach for patients with progressive systemic sclerosis (SSc), a rare and life-threatening orphan autoimmune disease. Whereas MSC immunomodulatory potential is considered as a central mechanism for their clinical benefit, very few data are available on the impact of MSCs on immune cell subsets in vivo. In the current extended study of a phase I/II clinical trial exploring the injection of a single dose of allogeneic bone marrow-MSCs (alloBM-MSCs) in patients with severe SSc (NCT02213705), we performed a longitudinal in-depth characterization of circulating immune cells in 19 MSC-treated patients, including 14 responders and 5 non-responders. By a combination of flow cytometry and transcriptomic analyses, we highlighted an increase in circulating CD24hiCD27posCD38lo/neg memory B cells, the main IL-10-producing regulatory B cell (Breg) subset, and an upregulation of IL10 expression in ex-vivo purified B cells, specifically in responder patients, early after the alloBM-MSC infusion. In addition, a deeper alteration of the B-cell compartment before alloBM-MSC treatment, including a higher expression of profibrotic cytokines IL6 and TGFβ by sorted B cells was associated with a non-responder clinical status. Finally, BM-MSCs were able to directly upregulate IL-10 production in activated B cells in vitro. These data suggest that cytokine-producing B cells, in particular Breg, are pivotal effectors of BM-MSC therapeutic activity in SSc. Their quantification as activity biomarkers in MSC potency assays and patient selection criteria may be considered to reach optimal clinical benefit when designing MSC-based clinical trials.

Research progress of engineered mesenchymal stem cells and their derived exosomes and their application in autoimmune/inflammatory diseases

Autoimmune/inflammatory diseases affect many people and are an important cause of global incidence and mortality. Mesenchymal stem cells (MSCs) have low immunogenicity, immune regulation, multidifferentiation and other biological characteristics, play an important role in tissue repair and immune regulation and are widely used in the research and treatment of autoimmune/inflammatory diseases. In addition, MSCs can secrete extracellular vesicles with lipid bilayer structures under resting or activated conditions, including exosomes, microparticles and apoptotic bodies. Among them, exosomes, as the most important component of extracellular vesicles, can function as parent MSCs. Although MSCs and their exosomes have the characteristics of immune regulation and homing, engineering these cells or vesicles through various technical means, such as genetic engineering, surface modification and tissue engineering, can further improve their homing and other congenital characteristics, make them specifically target specific tissues or organs, and improve their therapeutic effect. This article reviews the advanced technology of engineering MSCs or MSC-derived exosomes and its application in some autoimmune/inflammatory diseases by searching the literature published in recent years at home and abroad.

Emerging of a new CD3+CD31HCD184+ tang cell phenothype in Sjögren’s syndrome induced by microencapsulated human umbilical cord matrix-derived multipotent stromal cells

Background

Sjögren’s syndrome (SS) is an autoimmune disease hallmarked by infiltration and destruction of exocrine glands. Currently, there is no therapy that warrants full recovery of the affected tissues. Umbilical cord-derived multipotent stromal cells, microincapsulated in an endotoxin-free alginate gel (CpS-hUCMS), were shown to modulate the inflammatory activity of PBMCs in SS patients in vitro, through release of soluble factors (TGFβ1, IDO1, IL6, PGE2, VEGF). These observations led us to set up the present study, aimed at defining the in vitro effects of CpS-hUCMS on pro- and anti-inflammatory lymphocyte subsets involved in the pathogenesis of SS.

Methods and results

Peripheral blood mononuclear cells (PBMCs) upon collection from SS patients and matched healthy donors, were placed in co-culture with CpS-hUCMS for five days. Cellular proliferation and T- (Tang, Treg) and B- (Breg, CD19+) lymphocyte subsets were studied by flow cytometry, while Multiplex, Real-Time PCR, and Western Blotting techniques were employed for the analysis of transcriptome and secretome. IFNγ pre-treated hUCMS were assessed with a viability assay and Western Blotting analysis before co-culture. After five days co-culture, CpS-hUCMS induced multiple effects on PBMCs, with special regard to decrease of lymphocyte proliferation, increase of regulatory B cells and induction of an angiogenic T cell population with high expression of the surface marker CD31, that had never been described before in the literature.

Conclusion

We preliminarily showed that CpS-hUCMS can influence multiple pro- and anti-inflammatory pathways that are deranged in SS. In particular, Breg raised and a new Tang phenothype CD3+CD31HCD184+ emerged. These results may considerably expand our knowledge on multipotent stromal cell properties and may open new therapeutic avenues for the management of this disease, by designing ad hoc clinical studies.

Mesenchymal Stem Cells in Acquired Aplastic Anemia: The Spectrum from Basic to Clinical Utility

Aplastic anemia (AA), a rare but potentially life-threatening disease, is a paradigm of bone marrow failure syndromes characterized by pancytopenia in the peripheral blood and hypocellularity in the bone marrow. The pathophysiology of acquired idiopathic AA is quite complex. Mesenchymal stem cells (MSCs), an important component of the bone marrow, are crucial in providing the specialized microenvironment for hematopoiesis. MSC dysfunction may result in an insufficient bone marrow and may be associated with the development of AA. In this comprehensive review, we summarized the current understanding about the involvement of MSCs in the pathogenesis of acquired idiopathic AA, along with the clinical application of MSCs for patients with the disease. The pathophysiology of AA, the major properties of MSCs, and results of MSC therapy in preclinical animal models of AA are also described. Several important issues regarding the clinical use of MSCs are discussed finally. With evolving knowledge from basic studies and clinical applications, we anticipate that more patients with the disease can benefit from the therapeutic effects of MSCs in the near future.

Modulation of Mesenchymal Stem Cells-Mediated Adaptive Immune Effectors' Repertoire in the Recovery of Systemic Lupus Erythematosus

The breakdown of self-tolerance of the immune response can lead to autoimmune conditions in which chronic inflammation induces tissue damage. Systemic lupus erythematosus (SLE) is a debilitating multisystemic autoimmune disorder with a high prevalence in women of childbearing age; however, SLE incidence, prevalence, and severity are strongly influenced by ethnicity. Although the mystery of autoimmune diseases remains unsolved, disturbance in the proportion and function of B cell subsets has a major role in SLE's pathogenesis. Additionally, colocalizing hyperactive T helper cell subgroups within inflammatory niches are indispensable. Despite significant advances in standard treatments, nonspecific immunosuppression, the risk of serious infections, and resistance to conventional therapies in some cases have raised the urgent need for new treatment strategies. Without the need to suppress the immune system, mesenchymal stem cells (MSCs), as ''smart" immune modulators, are able to control cellular and humoral auto-aggression responses by participating in precursor cell development. In lupus, due to autologous MSCs disorder, the ability of allogenic engrafted MSCs in tissue regeneration and resetting immune homeostasis with the provision of a new immunocyte repertoire has been considered simultaneously. In Brief The bone marrow mesenchymal stem cells (BM-MSCs) lineage plays a critical role in maintaining the hematopoietic stem-cell microstructure and modulating immunocytes. The impairment of BM-MSCs and their niche partially contribute to the pathogenesis of SLE-like diseases. Allogenic MSC transplantation can reconstruct BM microstructure, possibly contributing to the recovery of immunocyte phenotype restoration of immune homeostasis. In terms of future prospects of MSCs, artificially gained by ex vivo isolation and culture adaptation, the wide variety of potential mediators and mechanisms might be linked to the promotion of the immunomodulatory function of MSCs.

Toward transplantation tolerance with adipose tissue-derived therapeutics

Solid organ and composite tissue allotransplanation have been widely applied to treat end-stage organ failure and massive tissue defects, respectively. Currently there are a lot of research endeavors focusing on induction of transplantation tolerance, to relieve the burden derived from long-term immunosuppressant uptake. The mesenchymal stromal cells (MSCs) have been demonstrated with potent immunomodulatory capacities and applied as promising cellular therapeutics to promote allograft survival and induce tolerance. As a rich source of adult MSCs, adipose tissue provides additional advantages of easy accessibility and good safety profile. In recent years, the stromal vascular fraction (SVF) isolated from adipose tissues following enzymatic or mechanical processing without in vitro culture and expansion has demonstrated immunomodulatory and proangiogenic properties. Furthermore, the secretome of AD-MSCs has been utilized in transplantation field as a potential "cell-free" therapeutics. This article reviews recent studies that employ these adipose-derived therapeutics, including AD-MSCs, SVF, and secretome, in various aspects of organ and tissue allotransplantation. Most reports validate their efficacies in prolonging allograft survival. Specifically, the SVF and secretome have performed well for graft preservation and pretreatment, potentially through their proangiogenic and antioxidative capacities. In contrast, AD-MSCs were suitable for peri-transplantation immunosuppression. The proper combination of AD-MSCs, lymphodepletion and conventional immunosuppressants could consistently induce donor-specific tolerance to vascularized composite allotransplants (VCA). For each type of transplantation, optimizing the choice of therapeutics, timing, dose, and frequency of administration may be required. Future progress in the application of adipose-derived therapeutics to induce transplantation tolerance will be further benefited by continued research into their mechanisms of action and the development of standardized protocols for isolation methodologies, cell culture, and efficacy evaluation.

Timing of Mesenchymal Stromal Cell Therapy Defines its Immunosuppressive Effects in a Rat Lung Transplantation Model

Cell therapy using mesenchymal stromal cells (MSCs) is being studied for its immunosuppressive effects. In organ transplantation, the amount of MSCs that accumulate in transplanted organs and other organs may differ depending on administration timing, which may impact their immunosuppressive effects. In vitro, adipose-derived mesenchymal stem cells (ADMSCs) suppress lymphocyte activation under cell-to-cell contact conditions. However, in vivo, it is controversial whether ADMSCs are more effective in accumulating in transplanted organs or in secondary lymphoid organs. Herein, we aimed to investigate whether the timing of ADMSC administration affects its immunosuppression ability in a rat lung transplantation model. In the transplantation study, rats were intramuscularly administered half the usual dose of tacrolimus (0.5 mg/kg) every 24 h after lung transplantation. ADMSCs (1 × 106) were administered via the jugular vein before (PreTx) or after (PostTx) transplantation. Cell tracking using quantum dots was performed. ADMSCs accumulated predominantly in the lung and liver; fewer ADMSCs were distributed in the grafted lung in the PreTx group than in the PostTx group. The rejection rate was remarkably low in the ADMSC-administered groups, particularly in the PostTx group. Serum tumor necrosis factor-α (TNF-α), interferon-γ, and interleukin (IL)-6 levels showed a greater tendency to decrease in the PreTx group than in the PostTx group. The proportion of regulatory T cells in the grafted lung 10 days after transplantation was higher in the PostTx group than in the PreTx group. PostTx administration suppresses rejection better than PreTx administration, possibly due to regulatory T cell induction by ADMSCs accumulated in the transplanted lungs, suggesting a mechanism different from that in heart or kidney transplantation that PreTx administration is more effective than PostTx administration. These results could help establish cell therapy using MSCs in lung transplantation.

Immunological priming of mesenchymal stromal/stem cells and their extracellular vesicles augments their therapeutic benefits in experimental graft-versus-host disease via engagement of PD-1 ligands

Mesenchymal stromal cells (MSCs) and their extracellular vesicles (EVs) exert profound anti-inflammatory and regenerative effects in inflammation and tissue damage, which makes them an attractive tool for cellular therapies. In this study we have assessed the inducible immunoregulatory properties of MSCs and their EVs upon stimulation with different combinations of cytokines. First, we found that MSCs primed with IFN-γ, TNF-α and IL-1β, upregulate the expression of PD-1 ligands, as crucial mediators of their immunomodulatory activity. Further, primed MSCs and MSC-EVs, compared to unstimulated MSCs and MSC-EVs, had increased immunosuppressive effects on activated T cells and mediated an enhanced induction of regulatory T cells, in a PD-1 dependent manner. Importantly, EVs derived from primed MSCs reduced the clinical score and prolonged the survival of mice in a model of graft-versus-host disease. These effects could be reversed in vitro and in vivo by adding neutralizing antibodies directed against PD-L1 and PD-L2 to both, MSCs and their EVs. In conclusion, our data reveal a priming strategy that potentiates the immunoregulatory function of MSCs and their EVs. This concept also provides new opportunities to improve the clinical applicability and efficiency of cellular or EV-based therapeutic MSC products.

Conglomeration of T- and B-Cell Matrix Responses Determines the Potency of Human Bone Marrow Mesenchymal Stromal Cells

Cell manufacturing facilities need to define the potency of mesenchymal stromal cells (MSCs) as cellular therapeutics in advanced clinical trials or marketing approval. Since MSCs' mechanism of action in humans is not well defined, more than a single functional property of MSCs needs to be captured as a surrogate measure of potency utilizing assay matrix technologies. However, the current limitation is the sole investigation of MSC-mediated T-cell suppression as a surrogate measure of potency. We investigated the effect of MSCs on B-cell matrix responses to be incorporated into the assay matrix potency analytical system. Our results demonstrate that MSCs inhibit B-cell differentiation and block pan-antibody secretion upon activation of B cells in the PBMCs. In contrast, MSCs are inferior in blocking B-cell matrix responses when purified B cells are used. Mechanistic analysis has demonstrated that MSC-mediated inhibition of B-cell matrix responses is non-contact dependent and Tryptophan metabolic pathway plays a major role, akin to the mechanism of MSC-mediated T-cell suppression. MSCs also inhibit both T-cell and B-cell responses when both of these lymphoid populations are concurrently activated in the PBMCs. Secretome analysis of MSC and T/B cell-activated PBMC cocultures identified direct and inverse correlative matrix signatures between humoral antibody isotypes and secretory molecules. The current analysis of the combined and concomitant investigation of T-cell and B-cell matrix responses fulfills the potency assay matrix strategy by incorporating MSCs' interaction with more than a single inflammatory immune responder.

MSCs can be a double-edged sword in tumorigenesis

Mesenchymal stem cells (MSCs) have been used to treat various diseases including Alzheimer's disease and cancer. In particular, the immunomodulatory function of MSCs plays a major role in cancer therapy using stem cells. However, MSCs exert promotive and inhibitory effects on cancer. The immunomodulatory effects of MSCs in the tumor microenvironment (TME) are ambiguous, which is the primary reason for the different outcomes of MSCs therapies for tumors. This review discusses the use of MSCs in cancer immunotherapy and their immunomodulatory mechanisms in cancers.

Mesenchymal Stem Cells and MSCs-Derived Extracellular Vesicles in Infectious Diseases: From Basic Research to Clinical Practice

Mesenchymal stem cells (MSCs) are attractive in various fields of regenerative medicine due to their therapeutic potential and complex unique properties. Basic stem cell research and the global COVID-19 pandemic have given impetus to the development of cell therapy for infectious diseases. The aim of this review was to systematize scientific data on the applications of mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) in the combined treatment of infectious diseases. Application of MSCs and MSC-EVs in the treatment of infectious diseases has immunomodulatory, anti-inflammatory, and antibacterial effects, and also promotes the restoration of the epithelium and stimulates tissue regeneration. The use of MSC-EVs is a promising cell-free treatment strategy that allows solving the problems associated with the safety of cell therapy and increasing its effectiveness. In this review, experimental data and clinical trials based on MSCs and MSC-EVs for the treatment of infectious diseases are presented. MSCs and MSC-EVs can be a promising tool for the treatment of various infectious diseases, particularly in combination with antiviral drugs. Employment of MSC-derived EVs represents a more promising strategy for cell-free treatment, demonstrating a high therapeutic potential in preclinical studies.

Bibliometric and visualization analysis of mesenchymal stem cells and rheumatoid arthritis (from 2012 to 2021)

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disease that can lead to joint deformity and loss of function. Recent studies have shown great progress in the research of mesenchymal stem cells (MSCs) in RA. However, thus far, there have been no bibliometric or visualization analyses in this field. This bibliometric analysis provides a comprehensive overview of the general information and research hotspots of MSCs and RA.

Methods

Articles relevant to MSCs and RA, published between 2012 and 2021, were searched using the Web of Science Core Collection database. Irrelevant publications were excluded from the analysis. Bibliometric and visualization analyses were conducted using VOSviewer, CiteSpace, and Scimago Graphica.

Results

A total of 577 articles were analyzed. The annual number of publications increased from 2012 to 2017 and plateaued from 2017 to 2021. China and the USA had the largest number of publications. Collaboration among different organizations mainly occurs between institutes of the same country. Stem Cell Research and Therapy and Frontiers in Immunology were the most popular journals in this field. All the top 20 co-cited authors had a positive co-citation relationship. The top references indicate that MSCs can contribute to RA research and treatment mainly via immunomodulation. From 2012 to 2021, “collagen-induced arthritis,” “immunomodulation,” and “therapy” were some of the keywords associated with MSCs and RA, while “extracellular vesicles” showed a strong keyword burst from 2019 to 2021.

Conclusion

MSCs and RA have been widely studied in different countries and institutions and by different authors over the last ten years. China and the USA had the largest number of publications. Different types of journals provide admirable sources for researchers. Some keywords, including immunomodulation and extracellular vesicles, may be hot spots in the near future. There will be more basic research and clinical translation of MSCs and RA, and substantial new treatments for RA will soon be developed.

“Adipose-derived mesenchymal stem cell therapy for the management of female sexual dysfunction: Literature reviews and study design of a clinical trial”

Hormone imbalance and female sexual dysfunction immensely affect perimenopausal female health and quality of life. Hormone therapy can improve female hormone deficiency, but long-term use increases the risk of cardiovascular diseases and cancer. Therefore, it is necessary to develop a novel effective treatment to achieve long-term improvement in female general and sexual health. This study reviewed factors affecting syndromes of female sexual dysfunction and its current therapy options. Next, the authors introduced research data on mesenchymal stromal cell/mesenchymal stem cell (MSC) therapy to treat female reproductive diseases, including Asherman’s syndrome, premature ovarian failure/primary ovarian insufficiency, and vaginal atrophy. Among adult tissue-derived MSCs, adipose tissue-derived stem cells (ASCs) have emerged as the most potent therapeutic cell therapy due to their abundant presence in the stromal vascular fraction of fat, high proliferation capacity, superior immunomodulation, and strong secretion profile of regenerative factors. Potential mechanisms and side effects of ASCs for the treatment of female sexual dysfunction will be discussed. Our phase I clinical trial has demonstrated the safety of autologous ASC therapy for women and men with sexual hormone deficiency. We designed the first randomized controlled crossover phase II trial to investigate the safety and efficacy of autologous ASCs to treat female sexual dysfunction in perimenopausal women. Here, we introduce the rationale, trial design, and methodology of this clinical study. Because aging and metabolic diseases negatively impact the bioactivity of adult-derived MSCs, this study will use ASCs cultured in physiological oxygen tension (5%) to cope with these challenges. A total of 130 perimenopausal women with sexual dysfunction will receive two intravenous infusions of autologous ASCs in a crossover design. The aims of the proposed study are to evaluate 1) the safety of cell infusion based on the frequency and severity of adverse events/serious adverse events during infusion and follow-up and 2) improvements in female sexual function assessed by the Female Sexual Function Index (FSFI), the Utian Quality of Life Scale (UQOL), and the levels of follicle-stimulating hormone (FSH) and estradiol. In addition, cellular aging biomarkers, including plasminogen activator inhibitor-1 (PAI-1), p16 and p21 expression in T cells and the inflammatory cytokine profile, will also be characterized. Overall, this study will provide essential insights into the effects and potential mechanisms of ASC therapy for perimenopausal women with sexual dysfunction. It also suggests direction and design strategies for future research.

Mesenchymal stromal cells induced regulatory B cells are enriched in extracellular matrix genes and IL-10 independent modulators

Regulatory B cells (Breg) are essential players in tolerance and immune homeostasis. However, lack of specific Breg markers limit their potential in clinical settings. Mesenchymal stromal cells (MSC) modulate B cell responses and are described to induce Breg in vitro. The aim of this work was to characterize MSC induced Breg (iBreg) and identify specific Breg biomarkers by RNAseq. After 7-day coculture with adipose tissue-derived MSC, B cells were enriched in transitional B cell populations, with increased expression and secretion of IL-10 and no TNFα. In addition, iBreg showed potential to modulate T cell proliferation at 2 to 1 cell ratios and their phenotype remained stable for 72h. RNAseq analysis of sorted IL-10 positive and negative iBreg populations identified over 1500 differentially expressed genes (DEG) among both populations. Analysis of biological processes of DEG highlighted an enrichment of immune regulation and extracellular matrix genes in IL-10- iBreg populations, while IL-10+ iBreg DEG were mostly associated with cell activation. This was supported by T cells modulation assays performed in the presence of anti-IL-10 neutralizing antibodies showing the non-essential role of IL-10 in the immunomodulatory capacity of iBregs on T cells. However, based on RNAseq results we explored the role of TGF-β and found out that it plays a major role on iBreg induction and iBreg immunomodulatory properties. Therefore, we report that MSC induce B cell populations characterized by the generation of extracellular matrix and immune modulation independently of IL-10.

Global scientific trends on the immunomodulation of mesenchymal stem cells in the 21st century: A bibliometric and visualized analysis

Background

Since the discovery of the immunomodulatory functions of mesenchymal stem cells (MSCs), their application in immunomodulation has attracted considerable attention, and an increasing number of studies have been conducted worldwide. Our research aimed to investigate the global status and trends in this field.

Methods

Publications on the immunomodulatory functions of MSCs from 1 January 2000 to 7 March 2022 were retrieved from the Web of Science Core Collection. The data were studied and indexed using the bibliometric methodology. Visualization analysis, co-authorship, co-occurrence analysis, and publication trends in MSC immunomodulation were conducted using the VOSviewer software.

Results

In total, 4,227 papers were included in the study. The number of publications and research interests has significantly increased globally. China published the highest number of related articles, while the US published articles with the highest number of citations. Stem Cell Research & Therapy had the highest number of publications. Sun Yat-sen University, Shanghai Jiao Tong University, Harvard University, and Seoul National University were the most contributive institutions. Furthermore, the studies were divided into four research hotspots for MSC immunomodulation: MSC immunomodulation in regenerative medicine, the effects and mechanisms of MSC immunomodulation, MSC therapy for immune diseases, and the cell source of MSCs.

Conclusion

This study indicates that the number of publications on MSC immunomodulation will increase in the future, and MSC immunomodulation mechanisms and clinical applications of MSC immunotherapy should be the next hotspots in this research field.

Mesenchymal stem cells and their microenvironment

Mesenchymal stem cells (MSCs), coming from a wide range of sources, have multi-directional differentiation ability. MSCs play vital roles in immunomodulation, hematopoiesis and tissue repair. The microenvironment of cells often refers to the intercellular matrix, other cells, cytokines and humoral components. It is also the place for cells’ interaction. The stability of the microenvironment is pivotal for maintaining cell proliferation, differentiation, metabolism and functional activities. Abnormal changes in microenvironment components can interfere cell functions. In some diseases, MSCs can interact with the microenvironment and accelerate disease progression. This review will discuss the characteristics of MSCs and their microenvironment, as well as the interaction between MSCs and microenvironment in disease.

Potential mesenchymal stem cell therapeutics for treating primary biliary cholangitis: advances, challenges, and perspectives

Primary biliary cholangitis (PBC) is a cholestatic autoimmune liver disease characterized by the gradual destruction of small intrahepatic bile ducts that eventually leads to liver cirrhosis, failure, and even carcinoma. The treatment options for PBC are limited, and the main treatment choices are the US Food and Drug Administration–approved ursodeoxycholic acid and obeticholic acid. However, many patients fail to respond adequately to these drugs and the adverse effects frequently lead to low life quality. For patients with end-stage PBC, liver transplantation remains the only effective treatment. Given their low immunogenicity, prominent immunomodulation property, differentiation potential, and tissue maintenance capacity, mesenchymal stem cells (MSCs) are emerging as new options for treating liver diseases, including PBC. Accumulating evidence from basic research to clinical studies supports the positive effects of MSC-based therapy for treating PBC. In this review, we characterized the underlying roles and mechanisms of MSCs for treating liver diseases and highlight recent basic and clinical advances in MSC-based therapy for treating PBC. Finally, the current challenges and perspectives for MSC-based therapy in clinical application are discussed, which could help accelerate the application of MSCs in clinical practice, especially for refractory diseases such as PBC.

Potency assays for human adipose-derived stem cells as a medicinal product toward wound healing

In pre-clinical studies, human adipose-derived stem cells (hASCs) have shown great promise as a treatment modality for healing of cutaneous wounds. The advantages of hASCs are that they are relatively easy to obtain in large numbers from basic liposuctions, they maintain their characteristics after long-term in vitro culture, and they possess low immunogenicity, which enables the use of hASCs from random donors. It has been hypothesized that hASCs exert their wound healing properties by reducing inflammation, inducing angiogenesis, and promoting fibroblast and keratinocyte growth. Due to the inherent variability associated with the donor-dependent nature of ASC-based products, it appears necessary that the quality of the different products is prospectively certified using a set of most relevant potency assays. In this review, we present an overview of the available methodologies to assess the Mode and the Mechanism of Action of hASCs, specifically in the wound healing scenario. In conclusion, we propose a panel of potential potency assays to include in the future production of ASC-based medicinal products.

Functional and Immune Modulatory Characteristics of Bone Marrow Mesenchymal Stromal Cells in Patients With Aplastic Anemia: A Systematic Review

Background

In most patients with aplastic anemia (AA), the diagnosis is limited to a description of the symptoms. Lack of understanding of the underlying pathophysiological mechanisms causing bone marrow failure (BMF), hampers tailored treatment. In these patients, auto-immune cell-mediated destruction of the bone marrow is often presumed to be the causative mechanism. The status of the bone marrow microenvironment, particularly the mesenchymal stromal cell (MSC) component, was recently suggested as a potential player in the pathophysiology of AA. Therefore, functional, and immune modulatory characteristics of bone marrow MSCs might represent important parameters for AA.

Objective

To conduct a systematic review to evaluate in vitro functional properties of MSCs derived from patients with AA compared to healthy controls.

Methods

According to PRISMA guidelines, a comprehensive search strategy was performed by using online databases (Pubmed, ISI Web of Science, Embase, and the Cochrane Library). Studies reporting on phenotypical characterization, proliferation potential, differentiation capacity, immunomodulatory potential, and ability to support hematopoiesis were identified and screened using the Rayyan software tool.

Results

23 articles were included in this systematic review, describing a total of 324 patients with AA and 285 controls. None of the studies identified a significant difference in expression of any MSC surface marker between both groups. However, AA-MSCs showed a decreased proliferation potential, an increased tendency to differentiate into the adipogenic lineage and decreased propensity towards osteogenic differentiation. Importantly, AA-MSCs show reduced capacity of immunosuppression and hematopoietic support in comparison to healthy controls.

Conclusion

We conclude that there are indications for a contribution of MSCs in the pathophysiology of AA. However, the current evidence is of poor quality and requires better defined study populations in addition to a more robust methodology to study MSC biology at a cellular and molecular level. Future studies on bone marrow microenvironment should aim at elucidating the interaction between MSCs, hematopoietic stem cells (HSCs) and immune cells to identify impairments associated with/causing BMF in patients with AA.

Mesenchymal stromal/stem cells and their exosomes application in the treatment of intervertebral disc disease: A promising frontier

Today, the application of mesenchymal stromal/stem cells (MSCs) and their exosomes to treat degenerative diseases has received attention. Due to the characteristics of these cells, such as self-renewability, differentiative and immunomodulatory effects, their use in laboratory and clinical studies shows promising results. However, the allogeneic transplantation problems of MSCs limit the use of these cells in the clinic. Scientists propose the application of exosomes to use from the therapeutic effect of MSCs and overcome their defects. These vesicles change the target cell behaviour and transcription profile by transferring various cargo such as proteins, mi-RNAs, and lipids. One of the degenerative tissue diseases in which MSCs and their exosomes are used in their treatment is intervertebral disc disease (IDD). Different factors such as genetics, nutrition, ageing, and environmental factors play a significant role in the onset and progression of this disease. These factors affect the cellular and molecular properties of the disc, leading to tissue destruction. Nucleus pulposus cells (NPCs) are among the most important cells involved in the pathogenesis of disc degeneration. MSCs exert their therapeutic effects by differentiating, reducing apoptosis, increasing proliferation, and decreasing senescence in NPCs. In addition, the use of MSCs and their exosomes also affects the annulus fibrosus and cartilaginous endplate cells in disc tissue and prevents disc degeneration progression.

A Brief Overview of Global Trends in MSC-Based Cell Therapy

Human mesenchymal stem cells (MSCs), also known as mesenchymal stromal cells or medicinal signaling cells, are important adult stem cells for regenerative medicine, largely due to their regenerative characteristics such as self-renewal, secretion of trophic factors, and the capability of inducing mesenchymal cell lineages. MSCs also possess homing and trophic properties modulating immune system, influencing microenvironment around damaged tissues and enhancing tissue repair, thus offering a broad perspective in cell-based therapies. Therefore, it is not surprising that MSCs have been the broadly used adult stem cells in clinical trials. To gain better insights into the current applications of MSCs in clinical applications, we perform a comprehensive review of reported data of MSCs clinical trials conducted globally. We summarize the biological effects and mechanisms of action of MSCs, elucidating recent clinical trials phases and findings, highlighting therapeutic effects of MSCs in several representative diseases, including neurological, musculoskeletal diseases and most recent Coronavirus infectious disease. Finally, we also highlight the challenges faced by many clinical trials and propose potential solutions to streamline the use of MSCs in routine clinical applications and regenerative medicine.

Human Mesenchymal Stem/Stromal Cells in Immune Regulation and Therapy

Studies of mesenchymal stem (or stromal) cells (MSCs) have moved from bedside to bench and back again. The stromal cells or fibroblasts are found in all tissues and participate in building the extracellular matrix (ECM). Bone marrow (BM)-derived MSCs have been studied for more than 50 years and have multiple roles. They function as stem cells and give rise to bone, cartilage, and fat in the BM (these are stem cells); support hematopoiesis (pericytes); and participate in sensing environmental changes and balancing pro- and anti-inflammatory conditions. In disease states, they migrate to sites of injury and release cytokines, hormones, nucleic acids depending on the microenvironment they find. Clinicians have begun to exploit these properties of BM, adipose tissue, and umbilical cord MSCs because they are easy to harvest and expand in culture. In this review, I describe the uses to which MSCs have been put, list ongoing clinical trials by organ system, and outline how MSCs are thought to regulate the innate and adaptive immune systems. I will discuss some of the reasons why clinical applications are still lacking. Much more work will have to be done to find the sources, doses, and culture conditions needed to exploit MSCs optimally and learn their healing potential. They are worth the effort.

Mesenchymal Stem Cell-Derived Extracellular Vesicles in Liver Immunity and Therapy

Mesenchymal stem cells (MSCs), as the most common cell source for stem cell therapy, play an important role in the modulation of innate and adaptive immune responses and have been widely used in clinical trials to treat autoimmune and inflammatory diseases. Recent experimental and clinical studies have shown that MSC-derived extracellular vesicles (MSC-EVs) can inhibit the activation and proliferation of a variety of proinflammatory cells, such as Th1, Th17 and M1 macrophages, reducing the secretion of proinflammatory cytokines, while promoting the proliferation of anti-inflammatory cells, such as M2 macrophages and Tregs, and increasing the secretion of anti-inflammatory cytokines, thus playing a role in immune regulation and exhibiting immunomodulatory functions. Besides MSC-EVs are more convenient and less immunogenic than MSCs. There is growing interest in the role of MSC-EVs in liver diseases owing to the intrinsic liver tropism of MSC-EVs. In this review, we focus on the immunomodulatory effects of MSC-EVs and summarize the pivotal roles of MSC-EVs as a cell-free therapy in liver diseases, including NAFLD, AIH, acute liver failure, liver fibrosis and hepatic ischemia–reperfusion injury. Moreover, we provide a concise overview of the potential use and limits of MSC-EVs in clinical application.

Mesenchymal stem cells transfer mitochondria to allogeneic Tregs in an HLA-dependent manner improving their immunosuppressive activity

Cell-based immunotherapies can provide safe and effective treatments for various disorders including autoimmunity, cancer, and excessive proinflammatory events in sepsis or viral infections. However, to achieve this goal there is a need for deeper understanding of mechanisms of the intercellular interactions. Regulatory T cells (Tregs) are a lymphocyte subset that maintain peripheral tolerance, whilst mesenchymal stem cells (MSCs) are multipotent nonhematopoietic progenitor cells. Despite coming from different origins, Tregs and MSCs share immunoregulatory properties that have been tested in clinical trials. Here we demonstrate how direct and indirect contact with allogenic MSCs improves Tregs’ potential for accumulation of immunosuppressive adenosine and suppression of conventional T cell proliferation, making them more potent therapeutic tools. Our results also demonstrate that direct communication between Tregs and MSCs is based on transfer of active mitochondria and fragments of plasma membrane from MSCs to Tregs, an event that is HLA-dependent and associates with HLA-C and HLA-DRB1 eplet mismatch load between Treg and MSC donors.

Regulatory T (Treg) cells and mesenchymal stem cells (MSCs) are both cell populations capable of immune tolerance induction. Here the authors show that the transfer of mitochondria from mesenchymal stem cells to allogeneic Treg cells in an HLA-dependent manner results in enhanced immunosuppressive functions of Treg cells.

Clinical efficacy and mechanism of mesenchymal stromal cells in treatment of COVID-19

Coronavirus disease 2019 (COVID-19) is a highly infectious epidemic disease that has seriously affected human health worldwide. To date, however, there is still no definitive drug for the treatment of COVID-19. Cell-based therapies could represent a new breakthrough. Over the past several decades, mesenchymal stromal cells (MSCs) have proven to be ideal candidates for the treatment of many viral infectious diseases due to their immunomodulatory and tissue repair or regeneration promoting properties, and several relevant clinical trials for the treatment of COVID-19 have been registered internationally. Herein, we systematically summarize the clinical efficacy of MSCs in the treatment of COVID-19 based on published results, including mortality, time to symptom improvement, computed tomography (CT) imaging, cytokines, and safety, while elaborating on the possible mechanisms underpinning the effects of MSCs, to provide a reference for subsequent studies.

Mesenchymal Stem Cell-Immune Cell Interaction and Related Modulations for Bone Tissue Engineering

Critical bone defects and related delayed union and nonunion are still worldwide problems to be solved. Bone tissue engineering is mainly aimed at achieving satisfactory bone reconstruction. Mesenchymal stem cells (MSCs) are a kind of pluripotent stem cells that can differentiate into bone cells and can be used as one of the key pillars of bone tissue engineering. In recent decades, immune responses play an important role in bone regeneration. Innate immune responses provide a suitable inflammatory microenvironment for bone regeneration and initiate bone regeneration in the early stage of fracture repair. Adaptive immune responses maintain bone regeneration and bone remodeling. MSCs and immune cells regulate each other. All kinds of immune cells and secreted cytokines can regulate the migration, proliferation, and osteogenic differentiation of MSCs, which have a strong immunomodulatory ability to these immune cells. This review mainly introduces the interaction between MSCs and immune cells on bone regeneration and its potential mechanism, and discusses the practical application in bone tissue engineering by modulating this kind of cell-to-cell crosstalk. Thus, an in-depth understanding of these principles of bone immunology can provide a new way for bone tissue engineering.

Immunoregulatory effects of dental mesenchymal stem cells on T and B lymphocyte responses in primary Sjögren's syndrome

Background: In this article, the authors investigate the modulatory effects of dental mesenchymal stem cells (MSCs) on lymphocyte responses in primary Sjögren's syndrome (pSS), which is an autoimmune disease resulting from keratoconjunctivitis sicca and xerostomia. Methods: Mononuclear cells isolated from pSS patients cultured with or without dental MSCs and analyzed for lymphocyte responses via flow cytometry. Results: Dental-follicle (DF)- and dental-pulp (DP)-MSCs downregulated CD4⁺ T lymphocyte proliferation by increasing Fas-ligand expression on T lymphocytes and FoxP3 expressing Tregs, and decreasing intracellular IFN-γ and IL-17 secretion in pSS patients. DF-MSCs decreased the plasma B cell ratio in the favor of naive B cell population in pSS patients' mononuclear cells. Conclusion: DF- and DP-MSCs can be the new cellular therapeutic candidates for the regulation of immune responses in pSS.

Research progress of the application of mesenchymal stem cells in chronic inflammatory systemic diseases

Chronic inflammatory systemic diseases are the result of the body's immune imbalance, with a long course and recurring episodes. Immunosuppressants are the main treatment, but not all patients respond well to it. Being capable of both self-renewal and differentiation into multiple tissue cells and low immunogenicity, mesenchymal stem cell is a promising treatment for chronic inflammatory systemic diseases. In this article, we describe the research progress and clinical application of mesenchymal stem cells in chronic inflammatory systemic diseases and look for influencing factors and biomarkers that can predict the outcome of patient with mesenchymal stem cell transplantation.