Mesenchymal stem cells can induce regulatory T cells via modulating miR-126a but not miR-10a. Gene. 2017;627:327-336. [PMID: 28600182 DOI: 10.1016/j.gene.2017.06.012]

The immunoregulatory property of mesenchymal stem cells in Crocin treatment by expression modulation of microRNA-155, microRNA-21, microRNA-23b, microRNA-126a, and their target inflammatory genes

Mesenchymal stem cells (MSCs) have high priority in clinical applications for treatment of immune disorders because of their immunomodulatory function. A lot of researches have currently been undertaken to enhance the stemness capacities of the cells and pick an excellent type of MSCs for clinical approaches. This study aims to assess the immunomodulatory related MicroRNAs (miRNAs) expression as well as their target genes in both adipose derived stem cells (Ad-SCs) and dental pulp derived stem cell (DP-SCs) in the presence or lack of Crocin (saffron plant's bioactive compound). For this purpose, first MSCs were extracted from adipose and dental pulp tissues, and then their mesenchymal nature was confirmed using flow cytometry and differentiation tests. Following the cell treatment with an optimal-non-toxic dose of Crocin (Obtained by MTT test), the expression of 4 selected immunomodulatory-related micro-RNAs (Mir-126, -21, -23, and-155) and their target genes (PI3K/ Akt 1 and 2/ NFKB and RELA) were assessed by RT-PCR. Our findings revealed that miRNA-23 and miRNA-126 were up-regulated in both types of cells treated with Crocin, while in the other side, miRNA-21 and miRNA-155 were down-regulated in DP-SCs and were up-regulated in Ad-SCs under treatment. Moreover, the real-time PCR results indicated that Crocin could significantly down regulate the expression of PI3K/ Akt1/ Akt2/ NFKB/ RELA genes in DP-SCs and PI3K/Akt2 genes in Ad-SCs and up regulate the expression of Akt1/ NFKB/ RELA genes in recent cells. Based on the analysis of the obtained data, the immunoregulatory effects of Crocin were higher in DP-SCs than in Ad-SCs. In conclusion, Crocin could control essential signaling pathways related to the inflammation by regulating the expression of related- miRNAs genes that play a key function in the immune regulation pathways in MSCs. Our findings can give an understanding of the mechanisms by which Crocin enhances the immunomodulatory feature of MSCs. According to the research findings, DP-SCs are probably a better immunomodulator in Crocin treatment than Ad-SCs and it may be helpful for MSCs selection in clinical applications for modulation or treatment of autoimmune disorders.

Bone marrow mesenchymal stem cells suppress activated CD4+ T cells proliferation through TGF-beta and IL10 dependent of autophagy in pathological hypoxic microenvironment

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) mediated immunomodulation by secreting certain bioactive cytokines has been recognized as a promising approach for disease treatment. However, microenvironmental oxygen tension affect immunomodulatory functions and activate autophagy in BMSCs. The mechanism governing BMSCs immunomodulation in hypoxia hasn't been expounded clearly. The aim of this study is to investigate the function of pathological hypoxia on immunomodulatory properties of bone marrow mesenchymal stem cells and its possible mechanism.

METHODS

BMSCs were cultured in either normoxia (21 % oxygen) or hypoxia (0.1 % oxygen) for 24 h, then electron microscopy (EM) and immunofluorescence staining were used to detect the activation of autophagy. Besides autophagy-related markers were monitored by Western blotting. Atg5 siRNA induced autophagic inhibition. Additional, gene expression levels of Real-time fluorescence quantitative PCR and Western blot were used to detect BMSCs related cytokines. Both the proliferation and apoptosis of CD4+ T cell in co-culture were detected by flow cytometry. Exogenous anti-IL-10 antibody and anti-TGF-β1 antibody were used in co-cultured BMSCs-CM and CD4+ T cells, which enabled us to assess how autophagy affected BMSCs-mediated CD4+ T cell proliferation in low oxygen tension.

RESULT

Compared with normal BMSCs, Hypo-BMSCs enhanced the immunosuppressive effect of BMSCs on CD4+ T cell proliferation, while si-atg5 weakened the inhibition of Hypo-BMSCs. Furthermore, exogenous anti-TGF-β1 antibody and the addition of anti-TGF-β1 antibody reversed the immunosuppressive ability of Hypo-BMSCs.

CONCLUSIONS

Our findings reveal that BMSCs possess significant immunosuppression on CD4+T cell through IL-10 and TGF-β1 dependent of autophagy in hypoxic microenvironment.

Mesenchymal stem cells modulate IL-17 and IL-9 production induced by Th17-inducing cytokine conditions in autoimmune arthritis: an explorative analysis

BACKGROUND

The importance of proinflammatory T-cells and their cytokine production in patients with autoimmune arthritis has been widely described. Due to their immunomodulatory properties, mesenchymal stem cells (MSCs) have come into focus as a potential therapeutic concept. The aim of this study was to investigate the influence of MSCs on the phenotype, cytokine profile, and functionality of naive and non-naive CD4+ T-cells from healthy donors (HD) and patients with autoimmune arthritis under Th17-cytokine polarizing conditions in an explorative way using a transwell system prohibiting any cell-cell-contact.

METHODS

Magnetically isolated naive and non-naive CD4+ T-cells were stimulated under Th17-polarizing proinflammatory cytokine conditions in presence and absence of bone marrow derived mesenchymal stromal cells (MSCs). After an incubation period of 6 days, the proportions of the T-cell subpopulations TEMRA (CD45RA+CD27-), memory (CD45RA-CD27+), effector (CD45RA-CD27-) and naive cells (CD45RA+CD27+) were determined. Quantitative immunofluorescence intensity was used as a measure for IL-9, IL-17 and IFN-γ production in each subpopulation.

RESULTS

In isolated naive CD4+ T-cells from HD and patients, MSCs suppressed the differentiation of naive towards an effector phenotype while memory and naive cells showed higher percentages in culture with MSCs. In patients, MSCs significantly decreased the proportion of IL-9 and IL-17 producing effector T-cells. MSCs also reduced IFN-γ production in the naive and memory phenotype from HD.

CONCLUSION

The results of the study indicate significant immunomodulatory properties of MSCs, as under Th17-polarizing conditions MSCs are still able to control T-cell differentiation and proinflammatory cytokine production in both HD and patients with autoimmune arthritis.

Transfer of mesenchymal stem cell mitochondria to CD4+ T cells contributes to repress Th1 differentiation by downregulating T-bet expression

BACKGROUND

Mesenchymal stem/stromal cells (MSCs) are multipotent cells with strong tissue repair and immunomodulatory properties. Due to their ability to repress pathogenic immune responses, and in particular T cell responses, they show therapeutic potential for the treatment of autoimmune diseases, organ rejection and graft versus host disease. MSCs have the remarkable ability to export their own mitochondria to neighboring cells in response to injury and inflammation. However, whether mitochondrial transfer occurs and has any role in the repression of CD4⁺ Th1 responses is unknown.

METHODS AND RESULTS

In this report we have utilized CD4⁺ T cells from HNT TCR transgenic mice that develop Th1-like responses upon antigenic stimulation in vitro and in vivo. Allogeneic bone marrow-derived MSCs reduced the diabetogenic potential of HNT CD4⁺ T cells in vivo in a transgenic mouse model of disease. In co-culture experiments, we have shown that MSCs were able to reduce HNT CD4⁺ T cell expansion, expression of key effector markers and production of the effector cytokine IFNγ after activation. This was associated with the ability of CD4⁺ T cells to acquire mitochondria from MSCs as evidenced by FACS and confocal microscopy. Remarkably, transfer of isolated MSC mitochondria to CD4⁺ T cells resulted in decreased T cell proliferation and IFNγ production. These effects were additive with those of prostaglandin E2 secreted by MSCs. Finally, we demonstrated that both co-culture with MSCs and transfer of isolated MSC mitochondria prevent the upregulation of T-bet, the master Th1 transcription factor, on activated CD4⁺ T cells.

CONCLUSION

The present study demonstrates that transfer of MSC mitochondria to activated CD4⁺ T cells results in the suppression of Th1 responses in part by downregulating T-bet expression. Furthermore, our studies suggest that MSC mitochondrial transfer might represent a general mechanism of MSC-dependent immunosuppression.

CD1d-independent NK1.1+ Treg cells are IL2-inducible Foxp3+ T cells co-expressing immunosuppressive and cytotoxic molecules

Regulatory T cells (Treg) play pivotal roles in maintaining self-tolerance and preventing immunological diseases such as allergy and autoimmunity through their immunosuppressive properties. Although Treg cells are heterogeneous populations with distinct suppressive functions, expression of natural killer (NK) cell receptors (NKR) by these cells remains incompletely explored. Here we identified that a small population of Foxp3+CD4+ Treg cells in mice expresses the NK1.1 NKR. Furthermore, we found that rare NK1.1+ subpopulations among CD4+ Treg cells develop normally in the spleen but not the thymus through CD1d-independent pathways. Compared with NK1.1- conventional Treg cells, these NK1.1+ Treg cells express elevated Treg cell phenotypic hallmarks, pro-inflammatory cytokines, and NK cell-related cytolytic mediators. Our results suggest that NK1.1+ Treg cells are phenotypically hybrid cells sharing functional properties of both NK and Treg cells. Interestingly, NK1.1+ Treg cells preferentially expanded in response to recombinant IL2 stimulation in vitro, consistent with their increased IL2Rαβ expression. Moreover, DO11.10 T cell receptor transgenic NK1.1+ Treg cells were expanded in an ovalbumin antigen-specific manner. In the context of lipopolysaccharide-induced systemic inflammation, NK1.1+ Treg cells downregulated immunosuppressive molecules but upregulated TNFα production, indicating their plastic adaptation towards a more pro-inflammatory rather than regulatory phenotype. Collectively, we propose that NK1.1+ Treg cells might play a unique role in controlling inflammatory immune responses such as infection and autoimmunity.

pcMSC Modulates Immune Dysregulation in Patients With COVID-19-Induced Refractory Acute Lung Injury

Background and Objectives

The novel coronavirus disease 2019 (COVID-19) has been a pandemic health issue in 30 January 2020. The mortality rate is as high as 50% in critically ill patients. Stem cell therapy is effective for those who are refractory to standard treatments. However, the immune responses that underlie stem cell therapy have not been well reported, particularly, in patients associated with moderate to severe acute respiratory distress syndrome (ARDS).

Methods

On Days 0 and 4, an intravenous infusion of 2 × 10⁷ placenta-derived mesenchymal stem cells (pcMSCs) (MatriPlax) were administered to five severe COVID-19 patients refractory to current standard therapies. Peripheral blood inflammatory markers and immune profiles were determined by multi-parameter flow cytometry and studied at Days 0, 4, and 8. Clinical outcomes were also observed.

Results

None of the pc-MSC treated patients experienced 28-day mortality compared with the control group and showed a significant improvement in the PaO₂/FiO₂ ratio, Murray’s lung injury scores, reduction in serum ferritin, lactate dehydrogenase (LDH), and C-reactive protein (CRP) levels. The cytokine profiles also showed a reduction in IL-1β, IFN-γ, IL-2, and IL-6, and an increase in IL-13 and IL-5 type 2 cytokines within 7 days of therapy. Lymphopenia was also significantly improved after 7 days of treatment. Immune cell profiles showed an increase in the proportions of CD4⁺ T cells (namely, CD4⁺ naïve T cells and CD4⁺ memory T cell subtypes), Treg cells, CD19⁺ B cells (namely, CD19⁺ naïve B cells, CD27⁺ switched B cell subtypes) and dendritic cells, and a significant decrease in the proportion of CD14⁺ monocytes (namely, CD16^- classical and CD16⁺ non-classical subtypes), and plasma/plasmablast cells. No adverse effects were seen at the serial follow-up visits for 2 months after initial therapy.

Conclusion

pc-MSCs therapy suppressed hyper-inflammatory states of the innate immune response to COVID-19 infection by increasing Treg cells, decreasing monocytes and plasma/plasmablast cells, and promoting CD4⁺ T cells and CD19⁺ B cells toward adaptive immune responses in severely critically ill COVID-19 patients with moderate to severe ARDS, especially those who were refractory to current standard care and immunosuppressive therapies.

Immunomodulatory effects of phytosomal curcumin on related-micro RNAs, CD200 expression and inflammatory pathways in dental pulp stem cells

Human dental pulp stem cells (hDPSCs) have significant potential of immunomodulatory for therapeutic and regenerative biomedical applications compared to other mesenchymal stem cells (MSCs). Nowadays, alteration of gene expression is an important way to improve the performance of MSCs in the clinic. MicroRNAs (miRs) and CD200 are known to modulate the immune system in MSCs. Curcumin is famous for its anti-inflammatory impacts. Phytosomal curcumin (PC) is a nanoparticle synthesized from curcumin that removes the drawbacks of curcumin. The purpose of this research was to assess the effects of PC on the expression of the CD200 and four key miRNAs in immune system. PC (30 μM) treatment of hDPSCs could ameliorate their immunoregulatory property, presented by reduced expressions of miR-21, miR-155 and miR-126, as well as enhanced expressions of miR-23 and CD200. The PC was also able to reduce PI3K\AKT1\NF-κB expressions that were target genes for these miRs and involved in inflammatory pathways. Moreover, PC was more effective than curcumin in improving the immune modulation of hDPSCs. Evidence in this study suggested that PC mediates immunoregulatory activities in hDPSC via miRs and CD200 to regulate PI3K\AKT1\NF-κB signalling pathways, which may provide a theoretical basis for PC in the treatment of many diseases. SIGNIFICANCE OF THE STUDY: Autoimmune diseases or tooth caries are partly attributed to global health problems and their common drug treatments have several side effects. The goal of this study is dentin regeneration and autoimmune diseases treatment via stem cell-based approaches with phytosomal curcumin (PC), for the first time. Because dental pulp stem cells have unique advantages (including higher immunomodulatory capacity) over other mesenchymal stem cells, we considered them the best option for treating these diseases. Using PC, we try to increase the immunomodulatory properties of these cells.

Differences and similarities between mesenchymal stem cell and endothelial progenitor cell immunoregulatory properties against T cells

Bone-marrow-derived mesenchymal stem cells and endothelial progenitor cells have some interesting biological properties that make them unique for cell therapy of degenerative and cardiovascular disorders. Although both cell populations have been already studied and used for their regenerative potentials, recently their special immunoregulatory features have brought much more attention. Mesenchymal stem cells and endothelial progenitor cells have both proangiogenic functions and have been shown to suppress the immune response, particularly T cell proliferation, activation, and cytokine production. This makes them suitable choices for allogeneic stem cell transplantation. Nevertheless, these two cells do not have equal immunoregulatory activities. Many elements including their extraction sources, age/passage, expression of different markers, secretion of bioactive mediators, and some others could change the efficiency of their immunosuppressive function. However, to our knowledge, no publication has yet compared mesenchymal stem cells and endothelial progenitor cells for their immunological interaction with T cells. This review aims to specifically compare the immunoregulatory effect of these two populations including their T cell suppression, deactivation, cytokine production, and regulatory T cells induction capacities. Moreover, it evaluates the implications of the tumor necrosis factor alpha-tumor necrosis factor receptor 2 axis as an emerging immune checkpoint signaling pathway controlling most of their immunological properties.

Small extracellular vesicles derived from interferon-γ pre-conditioned mesenchymal stromal cells effectively treat liver fibrosis

Mesenchymal stromal cells (MSCs) are used for ameliorating liver fibrosis and aiding liver regeneration after cirrhosis; Here, we analyzed the therapeutic potential of small extracellular vesicles (sEVs) derived from interferon-γ (IFN-γ) pre-conditioned MSCs (γ-sEVs). γ-sEVs effectively induced anti-inflammatory macrophages with high motility and phagocytic abilities in vitro, while not preventing hepatic stellate cell (HSC; the major source of collagen fiber) activation in vitro. The proteome analysis of MSC-derived sEVs revealed anti-inflammatory macrophage inducible proteins (e.g., annexin-A1, lactotransferrin, and aminopeptidase N) upon IFN-γ stimulation. Furthermore, by enabling CX₃CR1+ macrophage accumulation in the damaged area, γ-sEVs ameliorated inflammation and fibrosis in the cirrhosis mouse model more effectively than sEVs. Single cell RNA-Seq analysis revealed diverse effects, such as induction of anti-inflammatory macrophages and regulatory T cells, in the cirrhotic liver after γ-sEV administration. Overall, IFN-γ pre-conditioning altered sEVs resulted in efficient tissue repair indicating a new therapeutic strategy.

Human fetal liver MSCs are more effective than adult bone marrow MSCs for their immunosuppressive, immunomodulatory, and Foxp3+ T reg induction capacity

BACKGROUND

Mesenchymal stem cells (MSCs) exhibit active abilities to suppress or modulate deleterious immune responses by various molecular mechanisms. These cells are the subject of major translational efforts as cellular therapies for immune-related diseases and transplantations. Plenty of preclinical studies and clinical trials employing MSCs have shown promising safety and efficacy outcomes and also shed light on the modifications in the frequency and function of regulatory T cells (T regs). Nevertheless, the mechanisms underlying these observations are not well known. Direct cell contact, soluble factor production, and turning antigen-presenting cells into tolerogenic phenotypes, have been proposed to be among possible mechanisms by which MSCs produce an immunomodulatory environment for T reg expansion and activity. We and others demonstrated that adult bone marrow (BM)-MSCs suppress adaptive immune responses directly by inhibiting the proliferation of CD4+ helper and CD8+ cytotoxic T cells but also indirectly through the induction of T regs. In parallel, we demonstrated that fetal liver (FL)-MSCs demonstrates much longer-lasting immunomodulatory properties compared to BM-MSCs, by inhibiting directly the proliferation and activation of CD4+ and CD8+ T cells. Therefore, we investigated if FL-MSCs exert their strong immunosuppressive effect also indirectly through induction of T regs.

METHODS

MSCs were obtained from FL and adult BM and characterized according to their surface antigen expression, their multilineage differentiation, and their proliferation potential. Using different in vitro combinations, we performed co-cultures of FL- or BM-MSCs and murine CD3+CD25-T cells to investigate immunosuppressive effects of MSCs on T cells and to quantify their capacity to induce functional T regs.

RESULTS

We demonstrated that although both types of MSC display similar cell surface phenotypic profile and differentiation capacity, FL-MSCs have significantly higher proliferative capacity and ability to suppress both CD4+ and CD8+ murine T cell proliferation and to modulate them towards less active phenotypes than adult BM-MSCs. Moreover, their substantial suppressive effect was associated with an outstanding increase of functional CD4+CD25+Foxp3+ T regs compared to BM-MSCs.

CONCLUSIONS

These results highlight the immunosuppressive activity of FL-MSCs on T cells and show for the first time that one of the main immunoregulatory mechanisms of FL-MSCs passes through active and functional T reg induction.

Immunomodulatory Properties of Mesenchymal Stromal Cells: An Update

Mesenchymal stromal cells (MSCs) are characterized by an extraordinary capacity to modulate the phenotype and functional properties of various immune cells that play an essential role in the pathogenesis of inflammatory disorders. Thus, MSCs efficiently impair the phagocytic and antigen-presenting capacity of monocytes/macrophages and promote the expression of immunosuppressive molecules such as interleukin (IL)-10 and programmed cell death 1 ligand 1 by these cells. They also effectively inhibit the maturation of dendritic cells and their ability to produce proinflammatory cytokines and to stimulate potent T-cell responses. Furthermore, MSCs inhibit the generation and proinflammatory properties of CD4⁺ T helper (Th)1 and Th17 cells, while they promote the proliferation of regulatory T cells and their inhibitory capabilities. MSCs also impair the expansion, cytokine secretion, and cytotoxic activity of proinflammatory CD8⁺ T cells. Moreover, MSCs inhibit the differentiation, proliferation, and antibody secretion of B cells, and foster the generation of IL-10-producing regulatory B cells. Various cell membrane-associated and soluble molecules essentially contribute to these MSC-mediated effects on important cellular components of innate and adaptive immunity. Due to their immunosuppressive properties, MSCs have emerged as promising tools for the treatment of inflammatory disorders such as acute graft-versus-host disease, graft rejection in patients undergoing organ/cell transplantation, and autoimmune diseases.

Interactions Between Allogeneic Mesenchymal Stromal Cells and the Recipient Immune System: A Comparative Review With Relevance to Equine Outcomes

Despite significant immunosuppressive activity, allogeneic mesenchymal stromal cells (MSCs) carry an inherent risk of immune rejection when transferred into a recipient. In naïve recipients, this immune response is initially driven by the innate immune system, an immediate reaction to the foreign cells, and later, the adaptive immune system, a delayed response that causes cell death due to recognition of specific alloantigens by host cells and antibodies. This review describes the actions of MSCs to both suppress and activate the different arms of the immune system. We then review the survival and effectiveness of the currently used allogeneic MSC treatments.

Current Preventions and Treatments of aGVHD: From Pharmacological Prophylaxis to Innovative Therapies

Graft versus host disease (GVHD) is one of the main causes of mortality and the reason for up to 50% of morbidity after hematopoietic stem cell transplantations (HSCT) which is the treatment of choice for many blood malignancies. Thanks to years of research and exploration, we have acquired a profound understanding of the pathophysiology and immunopathology of these disorders. This led to the proposition and development of many therapeutic approaches during the last decades, some of them with very promising results. In this review, we have focused on the recent GVHD treatments from classical chemical and pharmacological prophylaxis to more innovative treatments including gene therapy and cell therapy, most commonly based on the application of a variety of immunomodulatory cells. Furthermore, we have discussed the advantages and potentials of cell-free therapy as a newly emerging approach to treat GVHD. Among them, we have particularly focused on the implication of the TNFα-TNFR2 axis as a new immune checkpoint signaling pathway controlling different aspects of many immunoregulatory cells.

Regulatory T cell induction by mesenchymal stem cells depends on the expression of TNFR2 by T cells

Mesenchymal stem/stromal cells can modulate the effector immune cells especially T lymphocytes. Due to this important feature, they can regulate the development of a variety of disorders including inflammatory and autoimmune disorders, cancers, and transplantation outcomes. One of the most important MSC immunoregulatory functions is their capacity to convert conventional T cells into regulatory T cells. Several mechanisms, mostly related to MSCs but not T cells, have been shown essential for this aspect. The inflammatory microenvironment majorly caused by pro-inflammatory cytokines has been demonstrated to govern the direction of the immune response. In this respect, we have recently revealed that the TNFα-TNFR2 signaling controls several aspects of MSC immunomodulatory properties including their ability to suppress T cells and their conversion towards Foxp3-expressing Tregs. Here in this work, we have looked from another angle by investigating the impact of TNFR2 expression by T cells on their ability to be converted to suppressive Tregs by MSCs. We showed that unlike WT-T cells, their TNFR2 KO counterparts are remarkably less able to convert into Foxp3+ and Foxp3- Tregs. Furthermore, TNFR2 blockade diminished the anti-inflammatory cytokine secretion by iTregs and consequently resulted in less T cell immunosuppression. This work is the first evidence of the crucial association of TNFR2 expression by T cells with their iTreg conversion capacity by MSCs. It strengthens once more the potential of anti-TNFR2 administration for a strong and effective interference with the immunosuppression exerted by TNFR2-expressing cells.

TNFR2 Is a Crucial Hub Controlling Mesenchymal Stem Cell Biological and Functional Properties

Mesenchymal stem cells (MSCs) have drawn lots of attention as gold standard stem cells in fundamental and clinical researches during the last 20 years. Due to their tissue and vascular repair capacities, MSCs have been used to treat a variety of degenerative disorders. Moreover, MSCs are able to modulate immune cells’ functions, particularly T cells while inducing regulatory T cells (iTregs). MSCs are very sensitive to inflammatory signals. Their biological functions could remarkably vary after exposure to different pro-inflammatory cytokines, notably TNFα. In this article, we have explored the importance of TNFR2 expression in a series of MSCs’ biological and functional properties. Thus, MSCs from wild-type (WT) and TNFR2 knockout (TNFR2 KO) mice were isolated and underwent several ex vivo experiments to investigate the biological significance of TNFR2 molecule in MSC main functions. Hampering in TNFR2 signaling resulted in reduced MSC colony-forming units and proliferation rate and diminished the expression of all MSC characteristic markers such as stem cell antigen-1 (Sca1), CD90, CD105, CD44, and CD73. TNFR2 KO-MSCs produced more pro-inflammatory cytokines like TNFα, IFNγ, and IL-6 and less anti-inflammatory mediators such as IL-10, TGFβ, and NO and induced Tregs with less suppressive effect. Furthermore, the TNFR2 blockade remarkably decreased MSC regenerative functions such as wound healing, complex tube formation, and endothelial pro-angiogenic support. Therefore, our results reveal the TNFα–TNFR2 axis as a crucial regulator of MSC immunological and regenerative functions.

Effect of Pomegranate Extract in Mesenchymal Stem Cells by Modulation of microRNA-155, microRNA-21, microRNA-23b, microRNA-126a, and PI3K\AKT1\NF- κ B Expression

Today, mesenchymal stem cells (MSCs) are candidates for various autoimmune disease treatments due to immunomodulatory activity in these cells. Much research has recently been done to improve the immunomodulatory activity of MSCs. Genetic variation is one of these methods. microRNAs (miRNAs) are small noncoding RNAs that control most of the cell's biological activities. Recent studies have shown that miRNAs play a significant role in the regulation of MSC immunomodulatory activity. Pomegranate is a fruit that has antioxidant, anti-inflammatory, and anticancer properties and has been used for many years for therapeutic purposes. The objective of this research is to evaluate the immunoregulatory-related miRNAs level of adipose-derived MSCs (Ad-MSCs) obtained from adipose tissue in the presence or lack of pomegranate (Punica granatum) extract (PGE). Our results showed that miRNA-23 and miRNA-126 were upregulated by PGE treatment in MSCs, and in contrast, miRNA-21 and miRNA-155 were downregulated by PGE treatment in MSCs. In addition this research shows that PGE can downregulate the expression of PI3K\AKT1\NF-κ B in Ad-MSCs. Our bioinformatics data have shown that the target of these four miRNAs and the signaling pathways, in which these targets are involved, can play an important role in regulating the immunomodulation function of stem cells. In conclusion, PGE can inhibit the expression of PI3K\AKT1\NF-κ B genes involved in inflammatory pathways via miRNA-23 and miRNA-126 overexpression or miRNA-21 and miRNA-155 downregulation that plays a role in the pathways of immune modulation in Ad-MSCs. These results may provide insight into the mechanism underlying the regulation of the immunomodulatory activity of Ad-MSCs by PGE.

TNFα/TNFR2 signaling pathway: an active immune checkpoint for mesenchymal stem cell immunoregulatory function

BACKGROUND

In addition to their multilineage potential, mesenchymal stem cells (MSCs) have a broad range of functions from tissue regeneration to immunomodulation. MSCs have the ability to modulate the immune response and change the progression of different inflammatory and autoimmune disorders. However, there are still many challenges to overcome before their widespread clinical administration including the mechanisms behind their immunoregulatory function. MSCs inhibit effector T cells and other immune cells, while inducing regulatory T cells (T regs), thus, reducing directly and indirectly the production of pro-inflammatory cytokines. TNF/TNFR signaling plays a dual role: while the interaction of TNFα with TNFR1 mediates pro-inflammatory effects and cell death, its interaction with TNFR2 mediates anti-inflammatory effects and cell survival. Many immunosuppressive cells like T regs, regulatory B cells (B regs), endothelial progenitor cells (EPCs), and myeloid-derived suppressor cells (MDSCs) express TNFR2, and this is directly related to their immunosuppression efficiency. In this article, we investigated the role of the TNFα/TNFR2 immune checkpoint signaling pathway in the immunomodulatory capacities of MSCs.

METHODS

Co-cultures of MSCs from wild-type (WT) and TNFR2 knocked-out (TNFR2 KO) mice with T cells (WT and TNFα KO) were performed under various experimental conditions.

RESULTS

We demonstrate that TNFR2 is a key regulatory molecule which is strongly involved in the immunomodulatory properties of MSCs. This includes their ability to suppress T cell proliferation, activation, and pro-inflammatory cytokine production, in addition to their capacity to induce active T regs.

CONCLUSIONS

Our results reveal for the first time the importance of the TNFα/TNFR2 axis as an active immune checkpoint regulating MSC immunological functions.

The TNF/TNFR2 signaling pathway is a key regulatory factor in endothelial progenitor cell immunosuppressive effect

Background

Endothelial progenitor cells (EPCs) are non-differentiated endothelial cells (ECs) present in blood circulation that are involved in neo-vascularization and correction of damaged endothelial sites. Since EPCs from patients with vascular disorders are impaired and inefficient, allogenic sources from adult or cord blood are considered as good alternatives. However, due to the reaction of immune system against allogenic cells which usually lead to their elimination, we focused on the exact role of EPCs on immune cells, particularly, T cells which are the most important cells applied in immune rejection. TNFα is one of the main activators of EPCs that recognizes two distinct receptors. TNFR1 is expressed ubiquitously and its interaction with TNFα leads to differentiation and apoptosis, whereas, TNFR2 is expressed predominantly on ECs, immune cells and neural cells and is involved in cell survival and proliferation. Interestingly, it has been shown that different immunosuppressive cells express TNFR2 and this is directly related to their immunosuppressive efficiency. However, little is known about immunological profile and function of TNFR2 in EPCs.

Methods

Using different in-vitro combinations, we performed co-cultures of ECs and T cells to investigate the immunological effect of EPCs on T cells. We interrupted in the TNFα/TNFR2 axis either by blocking the receptor using TNFR2 antagonist or blocking the ligand using T cells derived from TNFα KO mice.

Results

We demonstrated that EPCs are able to suppress T cell proliferation and modulate them towards less pro-inflammatory and active phenotypes. Moreover, we showed that TNFα/TNFR2 immune-checkpoint pathway is critical in EPC immunomodulatory effect.

Conclusions

Our results reveal for the first time a mechanism that EPCs use to suppress immune cells, therefore, enabling them to form new immunosuppressive vessels. Furthermore, we have shown the importance of TNFα/TNFR2 axis in EPCs as an immune checkpoint pathway. We believe that targeting TNFR2 is especially crucial in cancer immune therapy since it controls two crucial aspects of tumor microenvironment: 1) Immunosuppression and 2) Angiogenesis.

Immunoregulatory properties of mesenchymal stem cells: Micro-RNAs

Mesenchymal stem cells (MSCs) are multipotent cells that are excellent candidates for different cellular therapies due to their physiological properties such as immunoregulatory function. whetheare currently utilized for regenerative medication and treatment of a number of inflammatory illnesses given their ability to considerably impact tissue microenvironments via extracellular vesicles or toll-like receptor pathway modulation. MicroRNAs (miRNAs) are small noncoding RNAs that target the messenger RNA and play a critical role in different biological procedures, such as the development and reaction of the immune system. Moreover, miRNAs have recently been revealed to have serious functions in MSCs to regulate immunomodulatory properties. In this review, we study how the miRNAs pathway can modulate the immunoregulatory activity of MSCs by counting their interactions with immune cells and also discuss the possibility of using miRNA-based implications for MSC-based therapies.

Mitochondrial transfer from MSCs to T cells induces Treg differentiation and restricts inflammatory response

Mesenchymal stem cells (MSCs) have fueled ample translation for the treatment of immune-mediated diseases. They exert immunoregulatory and tissue-restoring effects. MSC-mediated transfer of mitochondria (MitoT) has been demonstrated to rescue target organs from tissue damage, yet the mechanism remains to be fully resolved. Therefore, we explored the effect of MitoT on lymphoid cells. Here, we describe dose-dependent MitoT from mitochondria-labeled MSCs mainly to CD4⁺ T cells, rather than CD8⁺ T cells or CD19⁺ B cells. Artificial transfer of isolated MSC-derived mitochondria increases the expression of mRNA transcripts involved in T-cell activation and T regulatory cell differentiation including FOXP3, IL2RA, CTLA4, and TGFβ1, leading to an increase in a highly suppressive CD25⁺ FoxP3⁺ population. In a GVHD mouse model, transplantation of MitoT-induced human T cells leads to significant improvement in survival and reduction in tissue damage and organ T CD4⁺ , CD8⁺ , and IFN-γ⁺ expressing cell infiltration. These findings point to a unique CD4⁺ T-cell reprogramming mechanism with pre-clinical proof-of-concept data that pave the way for the exploration of organelle-based therapies in immune diseases.

A novel direct co-culture assay analyzed by multicolor flow cytometry reveals context- and cell type-specific immunomodulatory effects of equine mesenchymal stromal cells

The immunomodulatory potential of multipotent mesenchymal stromal cells (MSC) provides a basis for current and future regenerative therapies. In this study, we established an approach that allows to address the effects of pro-inflammatory stimulation and co-culture with MSC on different specific leukocyte subpopulations. Equine peripheral blood leukocyte recovery was optimized to preserve all leukocyte subpopulations and leukocyte activation regimes were evaluated. Allogeneic labeled equine adipose-derived MSC were then subjected to direct co-culture with either non-stimulated, concanavalin A (ConA)-activated or phosphate 12-myristate 13-acetate and ionomycin (PMA/I)-activated leukocytes. Subsequently, production of the cytokines interferon-γ (IFN- γ), interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α) and presence of FoxP3 were determined in specific cell populations using multicolor flow cytometry. Prostaglandin E2 (PGE2) was measured in the supernatants. ConA-stimulation induced mild activation of leukocytes, whereas PMA/I-stimulation led to strong activation. In T cells, PMA/I promoted production of all cytokines, with no distinct suppressive effects of MSC. However, increased numbers of CD25/FoxP3-positive cells indicated that MSC supported regulatory T cell differentiation in PMA/I-activated leukocyte cultures. MSC also reduced numbers of cytokine-producing B cells and granulocytes, mostly irrespective of preceding leukocyte activation, and reversed the stimulatory effect of ConA on IFN-γ production in monocytes. Illustrating the possible suppressive mechanisms, higher numbers of MSC produced IL-10 when co-cultured with non-stimulated or ConA-activated leukocytes. This was not observed in co-culture with PMA/I-activated leukocytes. However, PGE2 concentration in the supernatant was highest in the co-culture with PMA/I-activated leukocytes, suggesting that PGE2 could still mediate modulatory effects in strongly inflammatory environment. These context- and cell type-specific modulatory effects observed give insight into the interactions between MSC and different types of immune cells and highlight the roles of IL-10 and PGE2 in MSC-mediated immunomodulation. The approach presented could provide a basis for further functional MSC characterization and the development of potency assays.

Immunomodulation by Mesenchymal Stem Cells (MSCs): Mechanisms of Action of Living, Apoptotic, and Dead MSCs

Expectations on mesenchymal stem cell (MSC) treatment are high, especially in the fields of sepsis, transplant medicine, and autoimmune diseases. Various pre-clinical studies have been conducted with encouraging results, although the mechanisms of action behind the observed immunomodulatory capacity of mesenchymal stem cells have not been fully understood. Previous studies have demonstrated that the immunomodulatory effect of MSCs is communicated via MSC-secreted cytokines and has been proven to rely on the local microenvironment as some of the observed effects depend on a pre-treatment of MSCs with inflammatory cytokines. Nonetheless, recent findings indicate that the cytokine-mediated effects are only one part of the equation as apoptotic, metabolically inactivated, or even fragmented MSCs have been shown to possess an immunomodulatory potential as well. Both cytokine-dependent and cytokine-independent mechanisms suggest a key role for regulatory T cells and monocytes in the overall pattern, but the principle as to why viable and non-viable MSCs have similar immunomodulatory capacities remains elusive. Here we review the current knowledge on cellular and molecular mechanisms involved in MSC-mediated immunomodulation and focus on the viability of MSCs, as there is still uncertainty concerning the tumorigenic potential of living MSCs.

Induction of CD4+CD25+Foxp3+ regulatory T cells by mesenchymal stem cells is associated with RUNX complex factors

Among the particular immunomodulation properties of mesenchymal stem cells (MSCs), one relies on their capacity to regulatory T cell (Treg) induction from effector T cells. Stable expression of Foxp3 has a dominant role in suppressive phenotype and stability of induced regulatory T cells (iTregs). How MSCs induce stable Foxp3 expression in iTregs remains unknown. We previously showed MSCs could enhance demethylation of Treg-specific demethylated region (TSDR) in iTregs in cell-cell contact manner (unpublished data). Here, we evaluated the possible effect of MSCs on the mRNA expression of Runx complex genes (Runx1, Runx3, and CBFB) that perch on TSDR in iTregs and play the main role in suppressive properties of Tregs, a regulatory pathway that has not yet been explored by MSCs. Also, we investigated the mRNA expression of MBD2 that promotes TSDR demethylation in Tregs. We first showed that in vitro MSC-iTreg induction was associated with strong mRNA modifications of genes involved in Runx complex. We next injected high doses of MSCs in a murine model of C57BL/6 into Balb/C allogeneic skin transplantation to prolong allograft survival. When splenocytes of grafted mice were analyzed, we realized that the Foxp3 expression was increased at day 5 and 10 post-graft merely in MSC-treated mice. Furthermore, Foxp3 mRNA expression was associated with modified Runx complex mRNA expression comparable to what was shown in in vitro studies. Hence, our data identify a possible mechanism in which MSCs convert conventional T cells to iTreg through strong modifications of mRNA of genes that are involved in Runx complex of Foxp3.

Immunoregulatory, proliferative and anti-oxidant effects of nanocurcuminoids on adipose-derived mesenchymal stem cells

Curcuminoids are dietary complexes extracted from the seeds of Curcuma longa L. that contain curcumin, bisdemethoxycurcumin and desmethoxycurcumin. Curcuminoids are popular for their pleiotropic therapeutic functions, such as their anti-inflammatory and anti-oxidant effects. Nonetheless, their clinical use is associated with poor systemic bioavailability and insolubility. The nano-formulation of curcuminoids eliminates these shortcomings. In the present study, we explored immunoregulatory, proliferative and anti-oxidant effects of nanocurcuminoids on adipose-derived mesenchymal stem cells (AT-MSCs). Flow cytometry analysis and MTT assay were employed to explore the effects of nanocurcuminoids on the apoptosis and proliferation of adipose-derived MSCs (AT-MSCs). The anti-oxidant effect of nanocurcuminoids on AT-MSCs also was examined. The immune regulatory effect of nanocurcuminoids was evaluated by the flow cytometric measurement of the T regulatory (Treg) population. The expression of inflammatory and anti-inflammatory cytokines was quantified using real-time PCR. Our findings demonstrate that low concentrations of nanocurcuminoids are beneficial for MSC proliferation, protection of MSCs from apoptosis, reducing inflammatory cytokines and SOD activity. A high concentration of nanocurcuminoids increases the population of Tregs and elevates the expression of TGFβ and FOXP3 genes. The beneficial effects of nanocurcuminoids on AT-MSCs were mainly observed at low doses of nanocurcuminoids.

Induction of CD4+CD25+FOXP3+ regulatory T cells by mesenchymal stem cells is associated with modulation of ubiquitination factors and TSDR demethylation

Background

Mesenchymal stem cells (MSCs) are known for their ability to induce the conversion of conventional T cells (Tconvs) into induced regulatory T cells (iTregs) in specific inflammatory contexts. Stable Foxp3 expression plays a major role in the phenotypic and functional stability of iTregs. However, how MSCs induce stable Foxp3 expression remains unknown.

Methods

We first investigated the role of cell–cell contact and cytokine secretion by bone marrow-derived MSCs (BM-MSCs) on the induction, stability, and suppressive functions of Tregs under various experimental conditions that lead to Foxp3 generation by flow cytometry and ELISA respectively. Second, we studied the effect of MSCs on TRAF6, GRAIL, USP7, STUB1, and UBC13 mRNA expression in CD4⁺ T cells in correlation with the suppressive function of iTregs by real-time PCR; also, we investigated Foxp3 Treg-specific demethylated region (TSDR) methylation in correlation with Foxp3 stability by the high-resolution melting technique. Third, we studied the effect of ex-vivo-expanded BM-MSCs on the induction of transplant tolerance in a model of fully allogeneic skin transplantation. We further analyzed the cytokine secretion patterns in grafted mice as well as the mRNA expression of ubiquitination genes in CD4⁺ T cells collected from the spleens of protected mice.

Results

We found that in-vitro MSC-induced Tregs express high mRNA levels of ubiquitination genes such as TRAF6, GRAIL, and USP7 and low levels of STUB1. Moreover, they have enhanced TSDR demethylation. Infusion of MSCs in a murine model of allogeneic skin transplantation prolonged allograft survival. When CD4⁺ T cells were harvested from the spleens of grafted mice, we observed that mRNA expression of the Foxp3 gene was elevated. Furthermore, Foxp3 mRNA expression was associated with increased TRAF6, GRAIL, UBC13, and USP7 and decreased STUB1 mRNA levels compared with the levels observed in vitro.

Conclusions

Our data suggest a possible ubiquitination mechanism by which MSCs convert Tconvs to suppressive and stable iTregs.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0991-1) contains supplementary material, which is available to authorized users.

Differentiation of umbilical cord derived mesenchymal stem cells to hepatocyte cells by transfection of miR-106a, miR-574-3p, and miR-451

Studying the profile of micro RNAs (miRs) elucidated the highest expressed miRs in hepatic differentiation. In this study, we investigated to clarify the role of three embryonic overexpressed miRs (miR-106a, miR-574-3p and miR-451) during hepatic differentiation of human umbilical cord derived mesenchymal stem cells (UC-MSCs). We furthermore, aimed to explore whether overexpression of any of these miRs alone is sufficient to induce the differentiation of the UC-MSCs into hepatocyte-like cells. UC-MSCs were transfected either alone or together with miR-106a, miR-574-3p and miR-451 and their potential hepatic differentiation and alteration in gene expression profile, morphological changes and albumin secretion ability were investigated. We found that up-regulation of any of these three miRs alone cannot induce expression of all hepatic specific genes. Transfection of each miR alone, led to Sox17, FoxA2 expression that are related to initiation step of hepatic differentiation. However, concurrent ectopic overexpression of three miRs together can induce UC-MSCs differentiation into functionally mature hepatocytes. These results show that miRs have the capability to directly convert UC-MSCs to a hepatocyte phenotype in vitro.