Allogeneic mesenchymal stem cells do not protect NZBxNZW F1 mice from developing lupus disease

A State-of-the-Art Review on the Recent Advances of Mesenchymal Stem Cell Therapeutic Application in Systematic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with an unknown etiology that has widespread clinical and immunological manifestations. Despite the increase in knowledge about the pathogenesis process and the increase in treatment options, however, the treatments fail in half of the cases. Therefore, there is still a need for research on new therapies. Mesenchymal stem cells (MSCs) are powerful regulators of the immune system and can reduce the symptoms of systemic lupus erythematosus. This study aimed to review the mechanisms of immune system modulation by MSCs and the role of these cells in the treatment of SLE. MSCs suppress T lymphocytes through various mechanisms, including the production of transforming growth factor-beta (TGF-B), prostaglandin E2 (PGE2), nitric oxide (NO), and indolamine 2 and 3-oxygenase (IDO). In addition, MSCs inhibit the production of their autoantibodies by inhibiting the differentiation of lymphocytes. The production of autoantibodies against nuclear antigens is an important feature of SLE. On the other hand, MSCs inhibit antigen delivery by antigen-presenting cells (APCs) to T lymphocytes. Studies in animal models have shown the effectiveness of these cells in treating SLE. However, few studies have been performed on the effectiveness of this treatment in humans. It can be expected that new treatment strategies for SLE will be introduced in the future, given the promising results of MSCs application.

Allogeneic Mesenchymal Stem Cells After In Vivo Transplantation: A Review

Autologous mesenchymal stem cells (MSCs) are ideal for tissue regeneration because of their ability to circumvent host rejection, but their procurement and processing present logistical and time-sensitive challenges. Allogeneic MSCs provide an alternative cell-based therapy capable of positively affecting all human organ systems, and can be readily available. Extensive research has been conducted in the treatment of autoimmune, degenerative, and inflammatory diseases with such stem cells, and has demonstrated predominantly safe outcomes with minimal complications. Nevertheless, continued clinical trials are necessary to ascertain optimal harvest and transplant techniques.

hUC-MSC transplantation therapy effects on lupus-prone MRL/lpr mice at early disease stages

BACKGROUND

The efficacy of human umbilical cord mesenchymal stem cell (hUC-MSC) transplantation in treating systemic lupus erythematosus (SLE) has been confirmed by small-scale clinical trials. However, these trials focused on severe or refractory SLE, while few studies focused on mild SLE. Therefore, this study focused on the therapeutic effects of hUC-MSC transplantation in early-stage or mild MRL/lpr lupus model mice.

METHODS

Commercially available hUC-MSCs were transplanted into 8-week-old MRL/lpr mice by tail vein injection. Flow cytometry was used to analyze B cells and their subsets in the peripheral blood. Further, plasma inflammatory factors, autoantibodies, and plasma biochemical indices were detected using protein chip technology and ELISA kits. In addition, pathological staining and immunofluorescence were performed to detect kidney injury in mice.

RESULTS

hUC-MSC transplantation did not affect the mice's body weight, and both middle and high dose hUC-MSC transplantation (MD and HD group) actually reduced spleen weight. hUC-MSC transplantation significantly decreased the proportion of plasmablasts (PB), IgG1- PB, IgG1+ PB, IgG1+ memory B (MB) cells, IgG1+ DN MB, and IgG1+ SP MB cells. The hUC-MSC transplantation had significantly reduced plasma levels of inflammatory factors, such as TNF-α, IFN-γ, IL-6, and IL-13. Pathological staining showed that the infiltration of glomerular inflammatory cells was significantly reduced and that the level of glomerular fibrosis was significantly alleviated in hUC-MSC-transplanted mice. Immunofluorescence assays showed that the deposition of IgG and IgM antibodies in the kidneys of hUC-MSC-transplanted mice was significantly lower than in the control.

CONCLUSION

hUC-MSC transplantation could inhibit the proliferation and differentiation of peripheral blood B cells in the early-stage of MRL/lpr mice, thereby alleviating the plasma inflammatory environment in mice, leading to kidney injury remission. The study provides a new and feasible strategy for SLE treatment.

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.

Advancement in therapeutic strategies for immune-mediated oral diseases

BACKGROUND

Immune-mediated diseases are a diverse group of conditions characterized by alteration of cellular homeostasis and inflammation triggered by dysregulation of the normal immune response. Several immune-mediated diseases exhibit oral signs and symptoms. Traditionally, these conditions are treated with corticosteroids or immunosuppressive agents, including azathioprine, cyclophosphamide, and thalidomide. Recent research into the developmental pathways of these diseases has led to the exploration of novel approaches in treatment. This review examines newer treatment modalities for the management of immune-mediated diseases with oral presentations. Topical calcineurin inhibitors (TCIs) such as tacrolimus and pimecrolimus have been employed successfully in managing oral lichen planus and pemphigus vulgaris. Biologic agents, comprising monoclonal antibodies, fusion proteins, and recombinant cytokines, can provide targeted therapy with fewer adverse effects. Neutraceutical agents comprising aloe vera, curcumin, and honey are commonly used in traditional medicine and offer a holistic approach. They may have a place as adjuvants to current standard therapeutic protocols. Photodynamic therapy (PDT) and low-level laser therapy (LLLT) utilize a specific wavelength of light to achieve desired cellular change. While the use of PDT in immune-mediated diseases is contentious, LLLT has shown positive results. Newer therapeutic modalities involve kinase inhibitors, S1P₁ receptor modulators, MSCs, and iRNA providing targeted treatment of specific diseases.

Immunomodulatory Activity of Mesenchymal Stem Cells in Lupus Nephritis: Advances and Applications

Lupus nephritis (LN) is a significant cause of various acute and chronic renal diseases, which can eventually lead to end-stage renal disease. The pathogenic mechanisms of LN are characterized by abnormal activation of the immune responses, increased cytokine production, and dysregulation of inflammatory signaling pathways. LN treatment is an important issue in the prevention and treatment of systemic lupus erythematosus. Mesenchymal stem cells (MSCs) have the advantages of immunomodulation, anti-inflammation, and anti-proliferation. These unique properties make MSCs a strong candidate for cell therapy of autoimmune diseases. MSCs can suppress the proliferation of innate and adaptive immune cells, such as natural killer cells (NKs), dendritic cells (DCs), T cells, and B cells. Furthermore, MSCs suppress the functions of various immune cells, such as the cytotoxicity of T cells and NKs, maturation and antibody secretion of B cells, maturation and antigen presentation of DCs, and inhibition of cytokine secretion, such as interleukins (ILs), tumor necrosis factor (TNF), and interferons (IFNs) by a variety of immune cells. MSCs can exert immunomodulatory effects in LN through these immune functions to suppress autoimmunity, improve renal pathology, and restore kidney function in lupus mice and LN patients. Herein, we review the role of immune cells and cytokines in the pathogenesis of LN and the mechanisms involved, as well as the progress of research on the immunomodulatory role of MSCs in LN.

Cell Based Treatment of Autoimmune Diseases in Children

Mesenchymal stem cells have recently been recoined as medicinal signaling cells (MSC) for their ability to promote tissue homeostasis through immune modulation, angiogenesis and tropism. During the last 20 years, there has been a plethora of publications using MSC in adults and to lesser extent neonates on a variety of illnesses. In parts of the world, autologous and allogeneic MSCs have been purified and used to treat a range of autoimmune conditions, including graft versus host disease, Crohn's disease, multiple sclerosis, refractory systemic lupus erythematosus and systemic sclerosis. Generally, these reports are not part of stringent clinical trials but are of note for good outcomes with minimal side effects. This review is to summarize the current state of the art in MSC therapy, with a brief discussion of cell preparation and safety, insights into mechanisms of action, and a review of published reports of MSC treatment of autoimmune diseases, toward the potential application of MSC in treatment of children with severe autoimmune diseases using multicenter clinical trials and treatment algorithms.

The immunomodulatory effects of mesenchymal stromal cell-based therapy in human and animal models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune inflammatory disease with no absolute cure. Although the exact etiopathogenesis of SLE is still enigmatic, it has been well demonstrated that a combination of genetic predisposition and environmental factors trigger a disturbance in immune responses and thereby participate in the development of this condition. Almost all available therapeutic strategies in SLE are primarily based on the administration of immunosuppressive drugs and are not curative. Mesenchymal stromal cells (MSCs) are a subset of non-hematopoietic adult stem cells that can be isolated from many adult tissues and are increasingly recognized as immune response modulating agents. MSC-mediated inhibition of immune responses is a complex mechanism that involves almost every aspect of the immune response. MSCs suppress the maturation of antigen-presenting cells (DC and MQ), proliferation of T cells (Th1, T17, and Th2), proliferation and immunoglobulin production of B cells, the cytotoxic activity of CTL and NK cells in addition to increasing regulatory cytokines (TGF-β and IL10), and decreasing inflammatory cytokines (IL17, INF-ϒ, TNF-α, and IL12) levels. MSCs have shown encouraging results in the treatment of several autoimmune diseases, in particular SLE. This report aims to review the beneficial and therapeutic properties of MSCs; it also focuses on the results of animal model studies, preclinical studies, and clinical trials of MSC therapy in SLE from the immunoregulatory aspect.

Bone Marrow-derived Mesenchymal Stem Cells and Chronic Allograft Disease in a Bronchiolitis Obliterans Animal Model

INTRODUCTION

Bronchiolitis obliterans (BO) is the most common expression of chronic allograft dysfunction in lung transplantation. Moreover, BO represents the major cause of death in the long-term after this procedure. On the other hand, mesenchymal stem cells have been tested in animal models of BO aiming to interfere in its development. The aim of this experimental study is to explore the role of bone-marrow derived stem cells (BMSCs) as a preventive intervention of BO occurrence.

MATERIALS AND METHODS

This an experimental randomized study. A bronchiolitis obliterans animal model in rats was reproduced: heterotopical tracheal transplant model in lung parenchyma. Five of these animals were used as control group. After setting up the model, individuals were divided in 3 groups of treatment (n=15), in which BMSCs were administered in 3 different time points after the tracheal transplant (tracheal transplantation and BMSCs administration occurred the same day, group G0; after 7 days, group G7; after 14 days, group G14. In addition, within each group, BMSCs were administered through 3 different routes: endotracheally, endovascular and topically in the lung parenchyma). Animals were sacrificed at 21 days. Histology, fluorescence in situ hybridization and immunohistochemistry techniques were performed for identifying stem cells.

RESULTS

Compared to control group, animals receiving BMSCs showed large neovessels in a loose fibrous matrix. Group G7 showed less fibrosis (p<0.033) and edema (p<0.028). Moreover, G7 animals receiving stem cells endotracheally showed no fibrosis (p<0.008). Alveolar-like patches of tissue were observed among all groups (53.4%, 46.7% and 40% in G0, G7 and G14 respectively), consisting of cells expressing both stem and alveolar cells biomarkers.

CONCLUSION

BMSCs modify the course of bronchiolitis obliterans and differentiate into alveolar cells. Endotracheal administration of BMSCs 7 days after the heterotopical tracheal transplant might be considered an effective way to prevent BO in this animal model.

Xenogeneic Transplantation of Human Placenta-Derived Mesenchymal Stem Cells Alleviates Renal Injury and Reduces Inflammation in a Mouse Model of Lupus Nephritis

Human placenta-derived mesenchymal stem cells (pMSCs) are considered a good source for cell therapy. The purpose of this study was to observe whether the transplantation of human pMSCs would affect the treatment of lupus nephritis (LN)-prone MRL/lpr mice. Multiple injections (at the 16th, 18th, and 20th week of age) of 1 × 10⁶ pMSCs were administered. Urine was collected to evaluate proteinuria and urine creatinine levels. Blood was collected for the measurement of serum antinuclear antibody (ANA) and anti-double-stranded DNA (dsDNA) antibody levels. Renal tissues were collected for histological staining and examination by light and electron microscopy quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western Blot. The results confirmed that pMSC treatment reduced the severity of 24-h proteinuria, decreased the production of anti-dsDNA antibodies, and ameliorated renal pathological changes in MRL/lpr mice. Furthermore, pMSCs reduced renal inflammation by inhibiting the expression of nuclear factor kappa B (NF-κB) and then downregulating the expression of tumor necrosis factor-α (TNF-α), intercellular cell adhesion molecule-1 (ICAM-1), and plasminogen activator inhibitor-1 (PAI-1). Therefore, our present study demonstrated a protective effect of pMSCs against renal injury and inflammation in MRL/lpr mice.

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

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

Mesenchymal Stem Cells in Primary Sjögren's Syndrome: Prospective and Challenges

Primary Sjögren's syndrome (pSS) is a chronic systemic inflammatory autoimmune disease characterized by lymphocytic infiltrates in exocrine glands. Current approaches do not control harmful autoimmune attacks or prevent irreversible damage and have considerable side effects. Mesenchymal stem cells (MSCs) have been effective in the treatment of several autoimmune diseases. The objective of this review is to illustrate the potential therapeutic role of MSCs in pSS. We summarize the recent advances in what is known about their immunomodulatory function and therapeutic applications in pSS. MSC transfusion can suppress autoimmunity and restore salivary gland secretory function in mouse models and patients with pSS by inducing regulatory T cells, suppressing Th1, Th17, and T follicular helper cell responses. In addition, MSCs can differentiate into salivary epithelial cells, presenting an option as a suitable alternative treatment. We also discuss current bioengineering methods which improve functions of MSCs for pSS. However, there remain many challenges to overcome before their wide clinical application.

Stem cells for lupus nephritis: a concise review of current knowledge

Lupus nephritis (LN), a common manifestation of systemic lupus erythematosus (SLE), accounts for significant morbidity and mortality in SLE patients. Since the available standard therapies and biologic agents for LN are yet to achieve the desired response and have considerable secondary effects, stem cell therapy has now emerged as a new approach. This therapy involves the transplantation of hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Our current review will highlight the progress of stem cell therapy for LN, along with the challenges encountered and the future direction of this approach.

Critical Role of Tumor Necrosis Factor Signaling in Mesenchymal Stem Cell-Based Therapy for Autoimmune and Inflammatory Diseases

Mesenchymal stem cells (MSCs) have been broadly used as a therapy for autoimmune disease in both animal models and clinical trials. MSCs inhibit T effector cells and many other immune cells, while activating regulatory T cells, thus reducing the production of pro-inflammatory cytokines, including tumor necrosis factor (TNF), and repressing inflammation. TNF can modify the MSC effects via two TNF receptors, i.e., TNFR1 in general mediates pro-inflammatory effects and TNFR2 mediates anti-inflammatory effects. In the central nervous system, TNF signaling plays a dual role, which enhances inflammation via TNFR1 on immune cells while providing cytoprotection via TNFR2 on neural cells. In addition, the soluble form of TNFR1 and membrane-bound TNF also participate in the regulation to fine-tune the functions of target cells. Other factors that impact TNF signaling and MSC functions include the gender of the host, disease course, cytokine concentrations, and the length of treatment time. This review will introduce the fascinating progress in this aspect of research and discuss remaining questions and future perspectives.

Mesenchymal stem cell transplantation in systemic lupus erythematous, a mesenchymal stem cell disorder

Systemic lupus erythematosus (SLE) is a chronic autoimmune and inflammatory disorder with involvement of several organs and systems such as the kidney, lung, brain and the hematopoietic system. As the most prevailing organ manifestation, lupus nephritis is the major cause of mortality and morbidity in SLE patients. The most classically and widely administered immunosuppressive medications, namely corticosteroids and cyclophosphamide, have eventuated in a remarkable amelioration in disease complications over the last few years and reduced the progression to end-stage multiorgan failure. Mesenchymal stem cells (MSCs) are considered as non-hematopoietic and multipotential progenitor cells, which are able to differentiate into multiple cell lineages such as chondrocytes, osteoblasts, myoblasts, endothelial cells, adipocytes, neuron-like cells, hepatocytes and cardiomyocytes. MSCs from SLE patients have demonstrated defects such as aberrant cytokine production. Moreover, impaired phenotype, growth and immunomodulatory functions of MSCs from patients with SLE in comparison to healthy controls have been reported. Therefore, it is hypothesized that SLE is potentially an MSC-mediated disease and, as a result, allogeneic rather than autologous MSC transplantation can be argued to be a potentially advantageous therapy for patients with SLE. On the other hand, the MSC senescence phenomenon may meet the current therapeutic approaches with challenges and demand more attention. Here, we discuss MSC transplantations to date in animal models and humans and focus on the MSC senescence complications in SLE patients.

Treatment with Allogenic Mesenchymal Stromal Cells in a Murine Model of Systemic Lupus Erythematosus

Objective

Pre-clinical and uncontrolled studies in patients with systemic lupus erythematosus (SLE) showed that mesenchymal stromal cells (MSCs) have a potential therapeutic role in refractory cases. The optimal therapeutic strategy in these patients remain to be elucidated. Our aim was to test the hypothesis that repeated administrations of 1×10⁶/kg body weight of allogenic MSCs, that is a significantly lower dosage with respect to the fixed 1×10⁶ MSC used in animal models, can be effective in improving the clinical course of a murine SLE model.

Methods

Bone marrow derived MSCs were obtained from 12-week-old C57BL/6J mice. Seventy-five 8 weeks old female NZ mice were randomly assigned to receive via caudal vein the following alternative treatments: 1) single infusion of 10⁶ MSCs/kg body weight at 18 weeks of age (NZ_s18) or at at 22 weeks of age (NZ_s22); 2) multiple monthly infusions of 10⁶ MSCs/kg body weight starting at 18 weeks of age (NZ_M18) or at 22 weeks of age (NZ_M22); 3) saline infusions (NZ_c) Fifteen 8 weeks old C57BL/6J mice (Envigo, Huntingdon, UK) were used as untreated controls (C). Weekly, body weight was recorded and twenty-four hour urines were collected by metabolic cages for each animal; proteinuria was detected by dipstick analysis. At sacrifice, peripheral blood samples were collected from mice and anti-dsDNA antibodies were detected by enzyme immunoassorbent assay (ELISA) method using commercial kits. At sacrifice, kidneys were analyzed for histopathology and immunohistochemical analysis for B220, CD4, MPO, CD4^＋Foxp3, F40/80 infiltration was performed.

Results

Proteinuria occurrence was delayed NZ_S and NZ_M mice, no differences were observed in anti-dsDNA autoantibody titer among the groups at the different time-points; at 36 weeks, no significant differences were observed in term of nephritis scores. Inflammatory cells deposition (MPO and F4/80 positive cells) in NZ_M was significantly higher than in NZ and NZ_S. An overexpression of B lymphocytes (B220) was found in NZ_M while T regulatory cells (CD4^＋ Foxp3^＋ cells) were reduced in both NZ_S and NZ_M with respect to NZ_c.

Conclusions

Overall, our study failed to show a positive effect of a treatment with murine MSCs in this model and, for some aspects, even deleterious results seem to be observed.

Mesenchymal stromal cells and autoimmunity

Mesenchymal stromal cells (MSCs) are committed progenitors of mesodermal origin that are found virtually in every organ and exhibit multilineage differentiation into osteocytes, adipocytes and chondrocytes. MSCs also mediate a wide spectrum of immunoregulatory activities that usually dampen innate and adaptive immune responses. These features have attracted interest in the perspective of developing novel cell therapies for autoimmune disease. However, depending on the microenvironmental conditions, MSCs may show a plastic behavior and switch to an immunostimulatory phenotype. After thorough characterization of the effects of MSCs on the immune system, MSC cell therapy has been tested in animal models of autoimmunity using different cell sources, protocols of in vitro expansion and routes and schedules of administration. The pre-clinical results have been encouraging in some models [e.g. Crohn's disease (CD), multiple sclerosis] and heterogeneous in others (e.g. graft-versus-host disease, systemic lupus erythematosus, rheumatoid arthritis). Clinical trials have been carried out and many are ongoing. As discussed, the results obtained are too preliminary to draw any conclusion, with the only exception of topical administration of MSCs in CD that has proven efficacious. The mechanism of action of infused MSCs is still under investigation, but the apparent paradox of a therapeutic effect achieved in spite of the very low number of cells reaching the target organ has been solved by the finding that MSC-derived extracellular vesicles (EVs) closely mimic the therapeutic activity of MSCs in pre-clinical models. These issues are critically discussed in view of the potential clinical use of MSC-derived EVs.

CD117+CD44+ Stem T Cells Develop in the Thymus and Potently Suppress T-cell Proliferation by Modulating the CTLA-4 Pathway

BACKGROUND

CD117 is expressed on double-negative (DN; CD4^-CD8^-) cells (Nat Rev Immunol 14:529-545; 2014), but whether it is expressed in other stages and its subsequent functions are unclear. We used an improved method of flow cytometry to analyze different populations of thymocytes (Sci Rep 4:5781; 2014). The expression of CD117 and CTLA-4 were directly assayed in the early stage of thymocytes.

METHODS

Flow cytometry was used to analyze different populations of thymocytes, and T-cell proliferation assays, RT-PCR, and real-time RT-PCR were used to characterize the stem cells and examine the function of CD44⁺CD117⁺ cells.

RESULTS

In DN cells, CD117 expression was greatest on CD44⁺CD25⁺ cells (DN₂), followed by CD44⁺CD25^- (DN₁), CD44^-CD25⁺ (DN₃), and CD44^-CD25^- (DN₄) cells. In thymocytes, CD117 expression was highest in DN cells, followed by single-positive (SP; CD4 or CD8) and double-positive (DP; CD4⁺CD8⁺) cells.  Especially, CD117 expression was positively associated with CD44 and CTLA-4 expression. CTLA-4 expression was highest in DN cells, followed by SP and DP cells. CTLA-4 expression was positively associated with CD25, CD44, and Foxp3 expression. CD44⁺CD117⁺ T cells expressed more CTLA-4, which suppressed T-cell proliferation and blocked CTLA-4 to cause antibody-induced T-cell proliferation.

CONCLUSION

These results suggest that CD44⁺CD117⁺ T cells are stem cells and a specific T-cell phenotype that initially develops in the thymus, but they do not progress through DN₃ and DN₄ stages, lack a DP stage, and potently suppress T-cell proliferation and modulate the CTLA-4 pathway.

Adipose-Derived Cell Transplantation in Systemic Sclerosis: State of the Art and Future Perspectives

Systemic sclerosis (SSc) is one of the most complex connective tissue diseases. Although significant progress in the knowledge of pathogenic mechanisms and timely diagnosis, therapeutic options remain limited. The attempt to find new treatments for SSc has led researchers to investigate the potential of cellular therapies using autologous and allogeneic stem cells. Multipotent mesenchymal stromal cells (MSCs) are considered an attractive candidate for cell-based therapies. MSCs comprise a heterogeneous population of cells with multilineage differentiation potential that are preferentially able to home to the sites of damage, and secrete various cytokines and growth factors that can have immunomodulatory, angiogenic, anti-inflammatory and anti-apoptotic effects. MSCs from bone-marrow have been first extensively characterized. Adipose tissue represents an additional abundant and accessible source of stem cells. Compared with BM-MSCs, adipose-derived stromal/stem cells (ASCs) offer several advantages, including ease of isolation, less donor morbidity, relative abundance, and rapidity of expansion. For all these reasons, at present ASCs are one of the most attractive and promising sources of adult stem cells for cell therapy, finding a field of application in the treatment of SSc, too. This review will focus on the current applications and possible future perspectives of adipose tissue-cell therapies in SSc.

Bone Marrow Mesenchymal Stem Cells Enhance the Differentiation of Human Switched Memory B Lymphocytes into Plasma Cells in Serum-Free Medium

The differentiation of human B lymphocytes into plasma cells is one of the most stirring questions with regard to adaptive immunity. However, the terminal differentiation and survival of plasma cells are still topics with much to be discovered, especially when targeting switched memory B lymphocytes. Plasma cells can migrate to the bone marrow in response to a CXCL12 gradient and survive for several years while secreting antibodies. In this study, we aimed to get closer to niches favoring plasma cell survival. We tested low oxygen concentrations and coculture with mesenchymal stem cells (MSC) from human bone marrow. Besides, all cultures were performed using an animal protein-free medium. Overall, our model enables the generation of high proportions of CD38⁺CD138⁺CD31⁺ plasma cells (≥50%) when CD40-activated switched memory B lymphocytes were cultured in direct contact with mesenchymal stem cells. In these cultures, the secretion of CXCL12 and TGF-β, usually found in the bone marrow, was linked to the presence of MSC. The level of oxygen appeared less impactful than the contact with MSC. This study shows for the first time that expanded switched memory B lymphocytes can be differentiated into plasma cells using exclusively a serum-free medium.

Mesenchymal Stem Cell Therapy for rheumatic diseases

Mesenchymal stem cell therapy (MSCT) is an innovative treatment for rheumatic diseases. Underlying mechanism of how MSCT works in rheumatic diseases are still uncertain and with various hypotheses. Animal studies in MSCT show conflicting results mainly attributed by the differences in administration methods of MSCT, types of MSC use and randomization procedures. Human studies of MSCT are so far small scale but with satisfactory results in patients with systemic lupus erythematosus (SLE). Human studies of MSCT, however, showed less rewarding results in patients with rheumatoid arthritis (RA) and systemic sclerosis (SSc). Larger scale studies are needed to confirm the efficiency of MSCT as well as the safety profile in human use.

No significant effects of Poly(I:C) on human umbilical cord-derived mesenchymal stem cells in the treatment of B6.MRL-Fas(lpr) mice

OBJECTIVE

Our study aimed to compare the curative effect and immunoregulation between MSCs activated by Poly(I:C) for 24hours and unactivated MSCs on lupus mice.

MATERIALS AND METHODS

MSCs were pretreated by Poly(I:C) at 50μg/mL for 24h. B6.MRL-Fas(lpr) mice were divided into UC-MSC treated group, FLS treated group, Poly(I:C) preconditioned MSC treated group (P-MSC) and untreated group randomly. All treated mice were infused with 1×10(6) MSCs or FLSs at the 24th week and were sacrificed 4 weeks later. The spleen weight, serum immunoglobulin G (IgG) levels, serum anti-double stranded DNA (anti-dsDNA) antibody levels, immune cell subsets, renal lesions and IgG deposition in the kidney were evaluated. The effects of two kinds of MSCs on the proliferation and apoptosis of CD4+ T cells were detected by flow cytometry. The TLR3 expression at protein level in MSCs was assessed with and without Poly(I:C) treatment. The expression of immunoregulatory factors were detected by qRT-PCR in different dose and duration of Poly(I:C).

RESULT

Poly(I:C) preconditioned MSCs had similar therapeutic effects in lupus mice compared with untreated MSCs in vivo. Furthermore, Poly(I:C) treated MSCs and untreated MSCs had comparable inhibitory effects on proliferation of T cells, and Poly(I:C) could enhance the expression of TLR3 at protein and mRNA level. Poly(I:C) could partly alter the mRNA levels of immunoregulatory factors, such as hepatocyte growth factor, transforming growth factor β1, vascular endothelial growth factor, but did not have significant changes in cyclooxygenase 2, interleukin 6, tumor necrosis factor α, indoleamine 2,3-dioxygenase, interferon γ and chemokine (C-C motif) ligand 2.

CONCLUSION

Our study did not find that Poly(I:C) treatment could enhance the therapeutic effect of MSCs in lupus mice in vivo.

The murine Pbx1-d lupus susceptibility allele accelerates mesenchymal stem cell differentiation and impairs their immunosuppressive function

Pre–B cell leukemia homeobox 1 (Pbx1)-d is a dominant-negative splice isoform of the gene Pbx1 that corresponds to the NZM2410 lupus susceptibility locus Sle1a1. Pbx1 is required to maintain stem cell self-renewal, including that of mesenchymal stem cells (MSCs). MSCs have immunosuppressive functions that require stem cell maintenance. We tested the hypothesis that the expression of Pbx1-d favors MSC differentiation and impairs their immunosuppressive functions. We demonstrate that Sle1a1 MSCs express high levels of Pbx1-d as compared with congenic C57BL/6J (B6) MSCs. Sle1a1 MSCs grew faster and differentiated significantly more rapidly into osteoblasts than did B6 MSCs. This corresponded to a significant decrease in the expression of genes associated with stemness and an increase in the expression of genes associated with differentiation. Additionally, Sle1a1 MSCs express a gene expression profile associated with an enhanced innate immunity and inflammation. Suppression of Ig production from TLR-activated B6 B cells and IL-2 secretion from activated B6 CD4+ T cells was significantly impaired in Sle1a1 MSCs as compared with B6 MSCs. B6.Sle1a1 MSCs showed intermediate activity in suppressing lupus immunophenotypes in three different mouse models. Taken together, these data suggest that the expression of the lupus susceptibility allele Pbx1-d isoform impairs MSC functions, which may contribute to lupus pathogenesis both through a defective immunosuppression and the promotion of a proinflammatory environment.

Human embryonic stem cell-derived mesenchymal cells preserve kidney function and extend lifespan in NZB/W F1 mouse model of lupus nephritis

Adult tissue-derived mesenchymal stromal cells (MSCs) are showing promise in clinical trials for systemic lupus erythematosus (SLE). However, the inability to manufacture large quantities of functional cells from a single donor as well as donor-dependent variability in quality limits their clinical utility. Human embryonic stem cell (hESC)-derived MSCs are an alternative to adult MSCs that can circumvent issues regarding scalability and consistent quality due to their derivation from a renewable starting material. Here, we show that hESC-MSCs prevent the progression of fatal lupus nephritis (LN) in NZB/W F1 (BWF1) mice. Treatment led to statistically significant reductions in proteinuria and serum creatinine and preserved renal architecture. Specifically, hESC-MSC treatment prevented disease-associated interstitial inflammation, protein cast deposition, and infiltration of CD3⁺ lymphocytes in the kidneys. This therapy also led to significant reductions in serum levels of tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6), two inflammatory cytokines associated with SLE. Mechanistically, in vitro data support these findings, as co-culture of hESC-MSCs with lipopolysaccharide (LPS)-stimulated BWF1 lymphocytes decreased lymphocyte secretion of TNFα and IL-6, and enhanced the percentage of putative regulatory T cells. This study represents an important step in the development of a commercially scalable and efficacious cell therapy for SLE/LN.

Update on mesenchymal stem cell-based therapy in lupus and scleroderma

Current systemic therapies are rarely curative for patients with severe life-threatening forms of autoimmune diseases (ADs). During the past 15 years, autologous hematopoietic stem cell transplantation has been demonstrated to cure some patients with severe AD refractory to all other available therapies. As a consequence, ADs such as lupus and scleroderma have become an emerging indication for cell therapy. Multipotent mesenchymal stem cells (MSCs), isolated from bone marrow and other sites, display specific immunomodulation and anti-inflammatory properties and appear as ideal tools to treat such diseases. The present update aims at summarizing recent knowledge acquired in the field of MSC-based therapies for lupus and scleroderma.

Inhibition of B-cell proliferation and antibody production by mesenchymal stromal cells is mediated by T cells

Bone marrow (BM)-derived mesenchymal stromal cells (MSCs), endowed with immunosuppressive and anti-inflammatory properties, represent a promising tool in immunoregulatory and regenerative cell therapy. Clarifying the interactions between MSCs and B-lymphocytes may be crucial for designing innovative MSC-based strategies in conditions in which B cells play a role, including systemic lupus erythematosus (SLE) and rejection of kidney transplantation. In this study, we show that, both in healthy subjects and in patients, in vitro B-cell proliferation, plasma-cell differentiation, and antibody production are inhibited by BM-derived MSCs when peripheral blood lymphocytes are stimulated with CpG, but not when sorted B cells are cultured with MSCs+CpG. Inhibition is restored in CpG+MSC cocultures when sorted T cells are added to sorted B cells, suggesting that this effect is mediated by T cells, with both CD4(+) and CD8(+) cells playing a role. Moreover, cell-cell contact between MSCs and T cells, but not between MSCs and B cells, is necessary to inhibit B-cell proliferation. Thus, the presence of functional T cells, as well as cell-cell contact between MSCs and T cells, are crucial for B-cell inhibition. This information can be relevant for implementing MSC-based therapeutic immune modulation in patients in whom T-cell function is impaired.

Comparative Efficacies of Long-Term Serial Transplantation of Syngeneic, Allogeneic, Xenogeneic, or CTLA4Ig-Overproducing Xenogeneic Adipose Tissue-Derived Mesenchymal Stem Cells on Murine Systemic Lupus Erythematosus

Allogeneic and xenogeneic transplantation are suitable alternatives for treating patients with stem cell defects and autoimmune diseases. The purpose of this study was to compare the effects of long-term serial transplantation of adipose tissue-derived mesenchymal stem cells (ASCs) from (NZB × NZW) F1 mice (syngeneic), BALB/c mice (allogeneic), or humans (xenogeneic) on systemic lupus erythematosus (SLE). The effects of transplanting human ASCs overproducing CTLA4Ig (CTLA4Ig-hASC) were also compared. Animals were divided into five experimental groups, according to the transplanted cell type. Approximately 500,000 ASCs were administered intravenously every 2 weeks from 6 to 60 weeks of age to all mice except for the control mice, which received saline. The human ASC groups (hASC and CTLA4Ig-hASC) showed a 13-week increase in average life spans and increased survival rates and decreased blood urea nitrogen, proteinuria, and glomerular IgG deposition. The allogeneic group also showed higher survival rates compared to those of the control, up to 40, 41, 42, 43, 44, 45, 52, and 53 weeks of age. Syngeneic ASC transplantation did not accelerate the mortality of the mice. The mean life span of both the syngeneic and allogeneic groups was prolonged for 6-7 weeks. Both human ASC groups displayed increased serum interleukin-10 and interleukin-4 levels, whereas both mouse ASC groups displayed significantly increased GM-CSF and interferon-γ levels in the serum. The strongest humoral immune response was induced by xenogeneic transplantation, followed by allogeneic, CTLA4Ig-xenogeneic, and syngeneic transplantations. Long-term serial transplantation of the ASCs from various sources displayed different patterns of cytokine expression and humoral responses, but all of them increased life spans in an SLE mouse model.

Mesenchymal stromal cells protect against caspase 3-mediated apoptosis of CD19(+) peripheral B cells through contact-dependent upregulation of VEGF

The immune suppressive and anti-inflammatory capabilities of bone marrow-derived mesenchymal stromal cells (MSCs) represent an innovative new tool in regenerative medicine and immune regulation. The potent immune suppressive ability of MSC over T cells, dendritic cells, and natural killer cells has been extensively characterized, however, the effect of MSC on B cell function has not yet been clarified. In this study, the direct effect of MSC on peripheral blood B cell function is defined and the mechanism utilized by MSC in enhancing B cell survival in vitro identified. Human MSC supported the activation, proliferation, and survival of purified CD19(+) B cells through a cell contact-dependent mechanism. These effects were not mediated through B cell activating factor or notch signaling. However, cell contact between MSC and B cells resulted in increased production of vascular endothelial growth factor (VEGF) by MSC facilitating AKT phosphorylation within the B cell and inhibiting caspase 3-mediated apoptosis. Blocking studies demonstrated that this cell contact-dependent effect was not dependent on signaling through CXCR4-CXCL12 or through the epidermal growth factor receptor (EGFR). These results suggest that direct cell contact between MSC and B cells supports B cell viability and function, suggesting that MSC may not represent a suitable therapy for B cell-mediated disease.

The immunomodulatory function of mesenchymal stem cells: mode of action and pathways

Mesenchymal stem cells (MSCs) are being increasingly investigated as a therapeutic alternative, not only for their possible regenerative potential but also for their immunomodulatory action, which is being exploited for controlling diseases associated with inflammation. Understanding their direct and indirect target cells, as well as their mode of action and relevant pathways, is a prerequisite for the appropriate and optimal use of MSCs in therapy. Here, we review recent findings on the effects of MSCs on adaptive and innate immune cells. We also consider the impact of the environment on MSC profile, both anti- and proinflammatory, and the mechanisms and molecular pathways through which their effects are mediated, both at the MSC and target cell levels.

Transplantation of Adipose Tissue-Derived Mesenchymal Stem Cells Prevents the Development of Lupus Dermatitis

MRL/lpr mice spontaneously develop high titers of anti-dsDNA antibodies and symptoms such as glomerular nephritis and organ weight gain. They also develop spontaneous skin inflammation similar to the cutaneous lesions common in human lupus erythematosus. This study aimed to compare the effects of long-term serial administration of human adipose tissue-derived mesenchymal stem cells (ASCs), CTLA4Ig-overexpressing ASCs, and cyclophosphamide treatment in MRL/lpr mice. MRL/lpr mice were divided into saline (C), cyclophosphamide (Y), ASC early (E), ASC late (L), and CTLA4Ig-overexpressing ASC (CT) treatment groups. Background-matched control MRL/MPJ mice treated with saline (N) were also compared. The treatment period was 5-23 weeks, except for the L group (15-23 weeks). Blood and tissue samples were collected when the mice were 24 weeks old. Organ weight, anti-dsDNA antibodies, urine protein, skin and kidney histologic abnormalities, and trabecular bone volume were evaluated. The Y group showed the greatest decrease in anti-dsDNA antibodies, organ weight, degree of kidney inflammation and glomerular infiltration of C3, and incidence rate of severe proteinuria; the E, L, and CT treatment groups showed better results than the C group. ASC transplantation reduced anti-dsDNA antibody levels significantly. Mice treated with ASCs or CTLA4Ig-ASCs starting from the early disease stage did not show dermatitis upon gross examination; they demonstrated significant improvement in hyperkeratosis, acanthosis, and inflammatory cell infiltration scores in histopathology. Micro-CT analysis revealed that cyclophosphamide treatment significantly decreased bone volume and increased bone spacing in the trabecular bone. Thus, we found that ASC and CTLA4-ASC treatments prevent lupus dermatitis development in MRL/lpr mice without adverse effects.

New strategies for overcoming limitations of mesenchymal stem cell-based immune modulation

Mesenchymal stem cells (MSCs) have rapidly been applied in a broad field of immune-mediated disorders since the first successful clinical use of MSCs for treatment of graft-versus-host disease. Despite the lack of supporting data, expectations that MSCs could potentially treat most inflammatory conditions led to rushed application and development of commercialized products. Today, both pre-clinical and clinical studies present mixed results for MSC therapy and the discrepancy between expected and actual efficacy of MSCs in various diseases has evoked a sense of discouragement. Therefore, we believe that MSC therapy may now be at a critical milestone for re-evaluation and re-consideration. In this review, we summarize the current status of MSC-based clinical trials and focus on the discrepancy between expected and actual outcome of MSC therapy from bench to bedside. Importantly, we discuss the underlying limitations of MSCs and suggest a new guideline for MSC therapy in hopes of improving their therapeutic efficacy.

Infusion of Human Bone Marrow-Derived Mesenchymal Stem Cells Alleviates Autoimmune Nephritis in a Lupus Model by Suppressing Follicular Helper T-Cell Development

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies to components of the cell nucleus. These autoantibodies are predominantly produced with the help of follicular helper T (Tfh) cells and form immune complexes that trigger widespread inflammatory damage, including nephritis. In recent studies, mesenchymal stem cells (MSCs) elicited diverse, even opposing, effects in experimental and clinical SLE. Here we investigated the effect of human bone marrow-derived MSCs (hBM-MSCs) in a murine model of SLE, the F1 hybrid between New Zealand Black and New Zealand White strains (NZB/W). We found that infusion of female NZB/W mice with hBM-MSCs attenuated glomerulonephritis; it also decreased levels of autoantibodies and the incidence of proteinuria and improved survival. These effects coincided with a decrease in Tfh cells and downstream components. Infiltration of long-lived plasma cells into the inflamed kidney was also reduced in the hBM-MSC-treated mice. Importantly, hBM-MSCs directly suppressed the in vitro differentiation of naive CD4(+) T cells toward Tfh cells in a contact-dependent manner. These results suggest that MSCs attenuate lupus nephritis by suppressing the development of Tfh cells and the subsequent activation of humoral immune components. They thus reveal a novel mechanism by which MSCs regulate humoral autoimmune diseases such as SLE.

Mesenchymal stem cells in the treatment of inflammatory and autoimmune diseases in experimental animal models

Multipotent mesenchymal stromal cells [also known as mesenchymal stem cells (MSCs)] are currently being studied as a cell-based treatment for inflammatory disorders. Experimental animal models of human immune-mediated diseases have been instrumental in establishing their immunosuppressive properties. In this review, we summarize recent studies examining the effectiveness of MSCs as immunotherapy in several widely-studied animal models, including type 1 diabetes, experimental autoimmune arthritis, experimental autoimmune encephalomyelitis, inflammatory bowel disease, graft-vs-host disease, and systemic lupus erythematosus. In addition, we discuss mechanisms identified by which MSCs mediate immune suppression in specific disease models, and potential sources of functional variability of MSCs between studies.

Immunoregulation by mesenchymal stem cells: biological aspects and clinical applications

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiation into mesenchymal lineages and that can be isolated from various tissues and easily cultivated in vitro. Currently, MSCs are of considerable interest because of the biological characteristics that confer high potential applicability in the clinical treatment of many diseases. Specifically, because of their high immunoregulatory capacity, MSCs are used as tools in cellular therapies for clinical protocols involving immune system alterations. In this review, we discuss the current knowledge about the capacity of MSCs for the immunoregulation of immunocompetent cells and emphasize the effects of MSCs on T cells, principal effectors of the immune response, and the immunosuppressive effects mediated by the secretion of soluble factors and membrane molecules. We also describe the mechanisms of MSC immunoregulatory modulation and the participation of MSCs as immune response regulators in several autoimmune diseases, and we emphasize the clinical application in graft versus host disease (GVHD).

Adipose tissue-derived mesenchymal stem cells induce expansion of interleukin-10-producing regulatory B cells and ameliorate autoimmunity in a murine model of systemic lupus erythematosus

Mesenchymal stem cells (MSCs) are multipotent cells characterized by immunomodulatory properties and are therefore considered a promising tool for the treatment of autoimmune diseases. One functional B-cell subset, regulatory B cells (Bregs), has recently been shown to restrain excessive inflammatory responses in autoimmune diseases. In the present study, we investigated the impact of human adipose-derived MSCs on Bregs and their therapeutic effect in an animal model of systemic lupus erythematosus (SLE). Coculture of human adipose-derived MSCs with splenocytes from C57BL/6 mice expanded the population of interleukin-10-producing B cells (B10 B cells). In vivo treatment with human adipose-derived MSCs reduced serum anti-double-stranded antibody levels and improved renal pathology of lupus mice (Roquin(san/san) mice). MSCs decreased ICOS(+)CD44(+) follicular helper T cells, Th1 cells and Th17 cells, in spleens of Roquin(san/san) mice. In contrast, MSCs increased Foxp3-expressing regulatory T cells. MSCs also decreased the size and number of germinal centers and effector B cells. As expected, in vivo treatment with MSCs expanded the population of Bregs in spleens of Roquin(san/san) mice. Our results indicate that human adipose-derived MSCs induce the expansion of Bregs and ameliorate autoimmunity in a murine model of SLE. These findings suggest that human adipose-derived MSCs may be a promising therapeutic strategy targeting B-cell-mediated autoimmune diseases such as SLE.

Bone marrow stromal cells as immunomodulators. A primer for dermatologists

Bone marrow stromal cells (BMSCs, also known as mesenchymal stem cells or MSCs) represent a unique cell population in the bone marrow with a long-known function to support hematopoiesis and replace skeletal tissues. The recent discovery that BMSCs also possess potent immunoregulatory features attracted a great deal of attention from stem cell biologists, immunologists and clinicians of different specialties worldwide. Initial clinical experience along with several animal models suggested that intravenously delivered BMSCs are able to regulate a wide variety of host immune cells and act in a way that is beneficial for the recipient in a variety of diseases. The role of the present review is to give a short introduction to the biology of BMSCs and to summarize our current understanding of how BMSCs modulate the immune system with special emphasis on available clinical data. Considering the audience of this journal we will also attempt to guide dermatologists in choosing the right skin conditions where BMSCs might be considered as a therapeutic alternative.

Differential efficacy of human mesenchymal stem cells based on source of origin

Mesenchymal stem cells (MSCs) are useful in tissue repair but also possess immunomodulatory properties. Murine and uncontrolled human trials suggest efficacy of MSCs in treating lupus. Autologous cells are preferable; however, recent studies suggest that lupus-derived MSCs lack efficacy in treating disease. Thus, the optimum derivation of MSCs for use in lupus is unknown. It is also unknown which in vitro assays of MSC function predict in vivo efficacy. The objectives for this study were to provide insight into the optimum source of MSCs and to identify in vitro assays that predict in vivo efficacy. We derived MSCs from four umbilical cords, four healthy bone marrows (BMs), and four lupus BMs. In diseased MRL/lpr mice, MSCs from healthy BM and umbilical cords significantly decreased renal disease, whereas lupus BM MSCs only delayed disease. Current in vitro assays did not differentiate efficacy of the different MSCs. However, differences in MSC efficacy were observed in B cell proliferation assays. Our results suggest that autologous MSCs from lupus patients are not effective in treating disease. Furthermore, standard in vitro assays for MSC licensing are not predictive of in vivo efficacy, whereas inhibiting B cell proliferation appears to differentiate effective MSCs from ineffective MSCs.

Mesenchymal stem cell population derived from human pluripotent stem cells displays potent immunomodulatory and therapeutic properties

Mesenchymal stem cells (MSCs) are being tested in a wide range of human diseases; however, loss of potency and inconsistent quality severely limit their use. To overcome these issues, we have utilized a developmental precursor called the hemangioblast as an intermediate cell type in the derivation of a highly potent and replenishable population of MSCs from human embryonic stem cells (hESCs). This method circumvents the need for labor-intensive hand-picking, scraping, and sorting that other hESC-MSC derivation methods require. Moreover, unlike previous reports on hESC-MSCs, we have systematically evaluated their immunomodulatory properties and in vivo potency. As expected, they dynamically secrete a range of bioactive factors, display enzymatic activity, and suppress T-cell proliferation that is induced by either allogeneic cells or mitogenic stimuli. However, they also display unique immunophenotypic properties, as well as a smaller size and >30,000-fold proliferative capacity than bone marrow-derived MSCs. In addition, this is the first report which demonstrates that hESC-MSCs can inhibit CD83 up-regulation and IL-12p70 secretion from dendritic cells and enhance regulatory T-cell populations induced by interleukin 2 (IL-2). This is also the first report which shows that hESC-MSCs have therapeutic efficacy in two different autoimmune disorder models, including a marked increase in survival of lupus-prone mice and a reduction of symptoms in an autoimmune model of uveitis. Our data suggest that this novel and therapeutically active population of MSCs could overcome many of the obstacles that plague the use of MSCs in regenerative medicine and serve as a scalable alternative to current MSC sources.

The promising potential of menstrual stem cells for antenatal diagnosis and cell therapy

Menstrual-derived stem cells (MenSCs) are a new source of mesenchymal stem cells isolated from the menstrual fluid. Currently, there is a growing interest in their clinical potential due to fact that they are multipotent, highly proliferative, and easy to obtain in a non-invasive manner. Sampling can be repeated periodically in a simplified and reproducible manner devoid of complications that no existing cell source can match. MenSCs are also free of ethical dilemmas, and display novel properties with regard to presently known adult derived stem cells. This review details their distinctive biological properties regarding immunophenotype and function, proliferation rate, differentiation potential, and paracrine effects mediated by secreted factors. Their possible role in antenatal diagnosis is also discussed. While more insight on their immunomodulatory and diagnostic properties is needed, the impact of clinical and epidemiological factors, such as age, use of contraceptives, or hormonal status still requires further investigations to properly assess their current and future use in clinical application and diagnosis.

Preclinical efficacy and mechanisms of mesenchymal stem cells in animal models of autoimmune diseases

Mesenchymal stem cells (MSCs) are present in diverse tissues and organs, including bone marrow, umbilical cord, adipose tissue, and placenta. MSCs can expand easily in vitro and have regenerative stem cell properties and potent immunoregulatory activity. They inhibit the functions of dendritic cells, B cells, and T cells, but enhance those of regulatory T cells by producing immunoregulatory molecules such as transforming growth factor-β, hepatic growth factors, prostaglandin E₂, interleukin-10, indolamine 2,3-dioxygenase, nitric oxide, heme oxygenase-1, and human leukocyte antigen-G. These properties make MSCs promising therapeutic candidates for the treatment of autoimmune diseases. Here, we review the preclinical studies of MSCs in animal models for systemic lupus erythematosus, rheumatoid arthritis, Crohn's disease, and experimental autoimmune encephalomyelitis, and summarize the underlying immunoregulatory mechanisms.

Novel approaches to lupus drug discovery using stem cell therapy. Role of mesenchymal-stem-cell-secreted factors

INTRODUCTION

Patients with systemic lupus erythematosus (SLE) are at increased risk for premature death, particularly among young adults, and present dilemmas regarding drug efficacy versus toxicity. Novel therapeutic strategies have included the use of mesenchymal stem cell (MSC) therapies that are promising but still have limitations. In several disease models, it has become apparent that MSCs do not necessarily replace diseased tissues but rather exert complex paracrine effects that are mediated by their extracellular-secreted products.

AREAS COVERED

In this review, the authors highlight the data on MSC treatment of SLE and related mechanisms of actions. This data includes the recent evidence that MSC-secreted factors such as extracellular microvesicles (MVs) are important mediators of MSC therapy. Among MVs, the authors delineate the role of exosomes as triggers of regenerative effects in target cells, mediated by transfer of proteins, mRNAs or microRNAs. The authors also outline some of the biological and regulatory restraints encountered by MSC therapy, in contrast to the potential advantages of MSC-derived exosomes as new therapeutic tools in SLE.

EXPERT OPINION

There is concern about reproducible data on the use of MSC therapy in rheumatic diseases and specifically SLE. Although most experts consider MSCs to be safe, there are still worries over donor variability, immune-mediated rejection, culture-induced senescence, loss of functional properties and genetic instability or eventual malignant transformation. MSC-released factors could avoid most limiting factors associated with cell therapy and are therefore expected to provide a new and safe therapeutic option at an affordable cost.

Mesenchymal stem cells do not prevent antibody responses against human α-L-iduronidase when used to treat mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPSI) is an autosomal recessive disease that leads to systemic lysosomal storage, which is caused by the absence of α-L-iduronidase (IDUA). Enzyme replacement therapy is recognized as the best therapeutic option for MPSI; however, high titers of anti-IDUA antibody have frequently been observed. Due to the immunosuppressant properties of MSC, we hypothesized that MSC modified with the IDUA gene would be able to produce IDUA for a long period of time. Sleeping Beauty transposon vectors were used to modify MSC because these are basically less-immunogenic plasmids. For cell transplantation, 4×10⁶ MSC-KO-IDUA cells (MSC from KO mice modified with IDUA) were injected into the peritoneum of KO-mice three times over intervals of more than one month. The total IDUA activities from MSC-KO-IDUA before cell transplantation were 9.6, 120 and 179 U for the first, second and third injections, respectively. Only after the second cell transplantation, more than one unit of IDUA activity was detected in the blood of 3 mice for 2 days. After the third cell transplantation, a high titer of anti-IDUA antibody was detected in all of the treated mice. Anti-IDUA antibody response was also detected in C57Bl/6 mice treated with MSC-WT-IDUA. The antibody titers were high and comparable to mice that were immunized by electroporation. MSC-transplanted mice had high levels of TNF-alpha and infiltrates in the renal glomeruli. The spreading of the transplanted MSC into the peritoneum of other organs was confirmed after injection of ¹¹¹In-labeled MSC. In conclusion, the antibody response against IDUA could not be avoided by MSC. On the contrary, these cells worked as an adjuvant that favored IDUA immunization. Therefore, the humoral immunosuppressant property of MSC is questionable and indicates the danger of using MSC as a source for the production of exogenous proteins to treat monogenic diseases.

Recent advances in mesenchymal stem cell immunomodulation: the role of microvesicles

Mesenchymal stem cells are the most widely used cell phenotype for therapeutic applications, the main reasons being their well-established abilities to promote regeneration of injured tissues and to modulate immune responses. Efficacy was reported in the treatment of several animal models of inflammatory and autoimmune diseases and, in clinical settings, for the management of disorders such as GVHD, systemic lupus erythematosus, multiple sclerosis, and inflammatory bowel disease. The effects of mesenchymal stem cells are believed to be largely mediated by paracrine signals, and several secreted molecules have been identified as contributors to the net biological effect. Recently, it has been recognized that bioactive molecules can be shuttled from cell to cell packed in microvesicles, tiny portions of cytoplasm surrounded by a membrane. Coding and noncoding RNAs are also carried in such microvesicles, transferring relevant biological activity to target cells. Several reports indicate that the regenerative effect of mesenchymal stem cells can be reproduced by microvesicles isolated from their culture medium. More recent evidence suggests that the immunomodulatory effects of mesenchymal stem cells are also at least partially mediated by secreted microvesicles. These findings allow better understanding of the mechanisms involved in cell-to-cell interaction and may have interesting implications for the development of novel therapeutic tools in place of the parent cells.

T cells from autoimmune patients display reduced sensitivity to immunoregulation by mesenchymal stem cells: role of IL-2

Mesenchymal stem cells (MSCs) are multipotent progenitor cells which have been shown to possess broad immunoregulatory and anti-inflammatory capabilities, making them a promising tool to treat autoimmune diseases (AIDs). Nevertheless, as in recent years T cells from AID patients have been found to resist suppression by regulatory T cells, the question of whether they could be regulated by MSCs arises. To use MSCs as a therapeutic tool in human autoimmune diseases, one prerequisite is that T cells from autoimmune patients will be sensitive to these stem cells. The aim of this work was to investigate the ability of healthy donor derived MSCs to inhibit the proliferation of T cells from two pathophysiologically different AIDs: Multiple Sclerosis (MS) and Myasthenia Gravis (MG). We show that MSC-induced inhibition of interferon-γ production and surface expression of the CD3, CD4 and CD28 receptors by activated lymphocytes was similar in the AID patients and healthy controls. Contrarily, the MSCs' ability to suppress the proliferation of T cells of both diseases was significantly weaker compared to their ability to affect T cells of healthy individuals. Although we found that the inhibitory mechanism is mediated through CD14+ monocytes, the faulty cellular component is the patients' T cells. MSC-treated MS and MG lymphocytes were shown to produce significantly more IL-2 than healthy subjects while coupling of the MSC treatment with neutralizing IL-2 antibodies resulted in inhibition levels similar to those of the healthy controls. MSCs were also found to down-regulate the lymphocyte surface expression of the IL-2 receptor (CD25) through both transcription inhibition and induction of receptor shedding. Addition of IL-2 to MSC-inhibited lymphocytes restored proliferation thus suggesting a key role played by this cytokine in the inhibitory mechanism. Taken together, these results demonstrate the potential of a MSC-based cellular therapy for MS, MG and possibly other autoimmune diseases but also highlight the need for a better understanding of the underlying mechanisms for development and optimization of clinical protocols.