Stromal Cell-Derived Factor-1 Mediates Cardiac Allograft Tolerance Induced by Human Endometrial Regenerative Cell-Based Therapy

Interleukin-37 contributes to endometrial regenerative cell-mediated immunotherapeutic effect on chronic allograft vasculopathy

BACKGROUND AIMS

Chronic allograft vasculopathy (CAV) remains a predominant contributor to late allograft failure after organ transplantation. Several factors have already been shown to facilitate the progression of CAV, and there is still an urgent need for effective and specific therapeutic approaches to inhibit CAV. Human mesenchymal-like endometrial regenerative cells (ERCs) are free from the deficiencies of traditional invasive acquisition methods and possess many advantages. Nevertheless, the exact immunomodulation mechanism of ERCs remains to be elucidated.

METHODS

C57BL/6 (B6) mouse recipients receiving BALB/c mouse donor abdominal aorta transplantation were treated with ERCs, negative control (NC)-ERCs and interleukin (IL)-37-/-ERCs (ERCs with IL-37 ablation), respectively. Pathologic lesions and inflammatory cell infiltration in the grafts, splenic immune cell populations, circulating donor-specific antibody levels and cytokine profiles were analyzed on postoperative day (POD) 40. The proliferative capacities of Th1, Th17 and Treg subpopulations were assessed in vitro.

RESULTS

Allografts from untreated recipients developed typical pathology features of CAV, namely endothelial thickening, on POD 40. Compared with untreated and IL-37-/-ERC-treated groups, IL-37-secreting ERCs (ERCs and NC-ERCs) significantly reduced vascular stenosis, the intimal hyperplasia and collagen deposition. IL-37-secreting ERCs significantly inhibited the proliferation of CD4+T cells, reduced the proportions of Th1 and Th17 cells, but increased the proportion of Tregs in vitro. Furthermore, in vitro results also showed that IL-37-secreting ERCs significantly inhibited Th1 and Th17 cell responses, abolished B-cell activation, diminished donor-specific antibody production and increased Treg proportions. Notably, IL-37-secreting ERCs remarkably downregulated the levels of pro-inflammatory cytokines (interferon-γ, tumor necrosis factor-α, IL-1β, IL-6 and IL-17A) and increased IL-10 levels in transplant recipients.

CONCLUSIONS

The knockdown of IL-37 dramatically abrogates the therapeutic ability of ERCs for CAV. Thus, this study highlights that IL-37 is indispensable for ERC-mediated immunomodulation for CAV and improves the long-term allograft acceptance.

The potential of mesenchymal stem cells to induce immune tolerance to allogeneic transplants

Organ allograft transplantation is an effective treatment plan for patients with organ failure. Although the application of continuous immunosuppressants makes successful allograft survival possible, the patients' long-term survival rate and quality of life are not ideal. Therefore, it is necessary to find a new strategy to alleviate transplant rejection by developing therapies for permanent allograft acceptance. One promising approach is the application of tolerogenic mesenchymal stem cells (MSCs). Extensive research on MSCs has revealed that MSCs have potent differentiation potential and immunomodulatory properties. This review describes the molecular markers and functional properties of MSCs as well as the immunomodulatory mechanisms of MSCs in transplantation, focuses on the research progress in clinical trials of MSCs, and expounds on the future development prospects and possible limitations.

CD73 mediates the therapeutic effects of endometrial regenerative cells in concanavalin A-induced hepatitis by regulating CD4+ T cells

BACKGROUND

As a kind of mesenchymal-like stromal cells, endometrial regenerative cells (ERCs) have been demonstrated effective in the treatment of Concanavalin A (Con A)-induced hepatitis. However, the therapeutic mechanism of ERCs is not fully understood. Ecto-5`-nucleotidase (CD73), an enzyme that could convert immune-stimulative adenosine monophosphate (AMP) to immune-suppressive adenosine (ADO), was identified highly expressed on ERCs. The present study was conducted to investigate whether the expression of CD73 on ERCs is critical for its therapeutic effects in Con A-induced hepatitis.

METHODS

ERCs knocking out CD73 were generated with lentivirus-mediated CRISPR-Cas9 technology and identified by flow cytometry, western blot and AMPase activity assay. CD73-mediated immunomodulatory effects of ERCs were investigated by CD4+ T cell co-culture assay in vitro. Besides, Con A-induced hepatitis mice were randomly assigned to the phosphate-buffered saline treated (untreated), ERC-treated, negative lentiviral control ERC (NC-ERC)-treated, and CD73-knockout-ERC (CD73-KO-ERC)-treated groups, and used to assess the CD73-mediated therapeutic efficiency of ERCs. Hepatic histopathological analysis, serum transaminase concentrations, and the proportion of CD4+ T cell subsets in the liver and spleen were performed to assess the progression degree of hepatitis.

RESULTS

Expression of CD73 on ERCs could effectively metabolize AMP to ADO, thereby inhibiting the activation and function of conventional CD4+ T cells was identified in vitro. In addition, ERCs could markedly reduce levels of serum and liver transaminase and attenuate liver damage, while the deletion of CD73 on ERCs dampens these effects. Furthermore, ERC-based treatment achieved less infiltration of CD4+ T and Th1 cells in the liver and reduced the population of systemic Th1 and Th17 cells and the levels of pro-inflammatory cytokines such as IFN-γ and TNF-α, while promoting the generation of Tregs in the liver and spleen, while deletion of CD73 on ERCs significantly impaired their immunomodulatory effects locally and systemically.

CONCLUSION

Taken together, it is concluded that CD73 is critical for the therapeutic efficiency of ERCs in the treatment of Con A-induced hepatitis.

CD73 mediated host purinergic metabolism in intestine contributes to the therapeutic efficacy of a novel mesenchymal-like endometrial regenerative cells against experimental colitis

Background

The disruption of intestinal barrier functions and the dysregulation of mucosal immune responses, mediated by aberrant purinergic metabolism, are involved in the pathogenesis of inflammatory bowel diseases (IBD). A novel mesenchymal-like endometrial regenerative cells (ERCs) has demonstrated a significant therapeutic effect on colitis. As a phenotypic marker of ERCs, CD73 has been largely neglected for its immunosuppressive function in regulating purinergic metabolism. Here, we have investigated whether CD73 expression on ERCs is a potential molecular exerting its therapeutic effect against colitis.

Methods

ERCs either unmodified or with CD73 knockout (CD73-/-ERCs), were intraperitoneally administered to dextran sulfate sodium (DSS)-induced colitis mice. Histopathological analysis, colon barrier function, the proportion of T cells, and maturation of dendritic cells (DCs) were investigated. The immunomodulatory effect of CD73-expressing ERCs was evaluated by co-culture with bone marrow-derived DCs under LPS stimulation. FACS determined DCs maturation. The function of DCs was detected by ELISA and CD4+ cell proliferation assays. Furthermore, the role of the STAT3 pathway in CD73-expressing ERCs-induced DC inhibition was also elucidated.

Results

Compared with untreated and CD73-/-ERCs-treated groups, CD73-expressing ERCs effectively attenuated body weight loss, bloody stool, shortening of colon length, and pathological damage characterized by epithelial hyperplasia, goblet cell depletion, the focal loss of crypts and ulceration, and the infiltration of inflammatory cells. Knockout of CD73 impaired ERCs-mediated colon protection. Surprisingly, CD73-expressing ERCs significantly decreased the populations of Th1 and Th17 cells but increased the proportions of Tregs in mouse mesenteric lymph nodes. Furthermore, CD73-expressing ERCs markedly reduced the levels of pro-inflammatory cytokines (IL-6, IL-1β, TNF-α) and increased anti-inflammatory factors (IL-10) levels in the colon. CD73-expressing ERCs inhibited the antigen presentation and stimulatory function of DCs associated with the STAT-3 pathway, which exerted a potent therapeutic effect against colitis.

Conclusions

The knockout of CD73 dramatically abrogates the therapeutic ability of ERCs for intestinal barrier dysfunctions and the dysregulation of mucosal immune responses. This study highlights the significance of CD73 mediates purinergic metabolism contributing to the therapeutic effects of human ERCs against colitis in mice.

IL-37 overexpression promotes endometrial regenerative cell-mediated inhibition of cardiac allograft rejection

BACKGROUND

Endometrial regenerative cells (ERCs) play an important role in attenuation of acute allograft rejection, while their effects are limited. IL-37, a newly discovered immunoregulatory cytokine of the IL-1 family, can regulate both innate and adaptive immunity. Whether IL-37 overexpression can enhance the therapeutic effects of ERCs in inhibition of acute cardiac allograft rejection remains unknown and will be explored in this study.

METHODS

C57BL/6 mice recipients receiving BALB/c mouse heterotopic heart allografts were randomly divided into the phosphate-buffered saline (untreated), ERC treated, negative lentiviral control ERC (NC-ERC) treated, and IL-37 overexpressing ERC (IL-37-ERC) treated groups. Graft pathological changes were assessed by H&E staining. The intra-graft cell infiltration and splenic immune cell populations were analyzed by immunohistochemistry and flow cytometry, respectively. The stimulatory property of recipient DCs was tested by an MLR assay. Furthermore, serum cytokine profiles of recipients were measured by ELISA assay.

RESULTS

Mice treated with IL-37-ERCs achieved significantly prolonged allograft survival compared with the ERC-treated group. Compared with all the other control groups, IL-37-ERC-treated group showed mitigated inflammatory response, a significant increase in tolerogenic dendritic cells (Tol-DCs), regulatory T cells (Tregs) in the grafts and spleens, while a reduction of Th1 and Th17 cell population. Additionally, there was a significant upregulation of immunoregulatory IL-10, while a reduction of IFN-γ, IL-17A, IL-12 was detected in the sera of IL-37-ERC-treated recipients.

CONCLUSION

IL-37 overexpression can promote the therapeutic effects of ERCs to inhibit acute allograft rejection and further prolong graft survival. This study suggests that gene-modified ERCs overexpressing IL-37 may pave the way for novel therapeutic options in the field of transplantation.

Uterus: A Unique Stem Cell Reservoir Able to Support Cardiac Repair via Crosstalk among Uterus, Heart, and Bone Marrow

Clinical evidence suggests that the prevalence of cardiac disease is lower in premenopausal women compared to postmenopausal women and men. Although multiple factors contribute to this difference, uterine stem cells may be a major factor, as a high abundance of these cells are present in the uterus. Uterine-derived stem cells have been reported in several studies as being able to contribute to cardiac neovascularization after injury. However, our studies uniquely show the presence of an “utero-cardiac axis”, in which uterine stem cells are able to home to cardiac tissue to promote tissue repair. Additionally, we raise the possibility of a triangular relationship among the bone marrow, uterus, and heart. In this review, we discuss the exchange of stem cells across different organs, focusing on the relationship that exists between the heart, uterus, and bone marrow. We present increasing evidence for the existence of an utero-cardiac axis, in which the uterus serves as a reservoir for cardiac reparative stem cells, similar to the bone marrow. These cells, in turn, are able to migrate to the heart in response to injury to promote healing.

Endometrial Regenerative Cell-Derived Conditioned Medium Alleviates Experimental Colitis

Background

Traditional interventions can play a certain role in attenuating ulcerative colitis (UC), known as one type of inflammatory bowel diseases, but sometimes are not effective. Endometrial regenerative cells (ERCs) have been shown to exert immunosuppressive effects in different models of inflammation, and stem cell-derived conditioned media (CM) have advantages over cell therapy in terms of easy access and direct action. However, whether ERC-CM could alleviate colitis remains unclear and will be explored in this study.

Methods

Menstrual blood was collected from healthy female volunteers to obtain ERCs and ERC-CM. Acute colitis was induced by 3% dextran sodium sulfate (DSS), and ERC-CM was injected on days 4, 6, and 8, respectively, after induction. The disease activity index was calculated through the record of weight change, bleeding, and fecal viscosity during the treatment process. Histological features, macrophage and CD4⁺ T cell in the spleen and colon, and cytokine profiles in the sera and colon were measured. In addition, an in vitro lymphocyte proliferation assay was measured by using a CCK-8 kit in this study.

Results

ERC-CM treatment significantly improved the symptoms and histological changes in colitis mice. ERC-CM increased the percentage of Tregs in the spleen and colon but decreased the percentages of M1 macrophages and Th1 and Th17 cells in the spleen and decreased the population of Th17 cells in the colon. In addition, ERC-CM treatment decreased the local expression of TNF-α, IL-6, and iNOS in the colon. Furthermore, ERC-CM increased the levels of anti-inflammatory cytokines IL-10 and IL-27 but decreased proinflammatory cytokines IL-6 and IL-17 in the sera. In addition, ERC-CM significantly inhibited ConA-induced mouse lymphocyte proliferation in vitro.

Conclusion

The results suggest that ERC-CM can exert similar therapeutic effects as ERCs and could be explored for future application of cell-free therapy in the treatment of colitis.

Understanding menstrual blood-derived stromal/stem cells: Definition and properties. Are we rushing into their therapeutic applications?

Cells with mesenchymal stem cell properties have been identified in menstrual blood and termed menstrual blood-derived stem/stromal cells (MenSCs). MenSCs have been proposed as ideal candidates for cell-based therapy in regenerative medicine and immune-related diseases. However, MenSCs identity has been loosely defined so far and there is controversy regarding their cell markers and differentiation potential. In this review, we outline the origin of MenSCs in the context of regenerating human endometrium, with attention to endometrial eMSCs as reference cells to understand MenSCs. We summarize the cell identity markers analyzed and the immunomodulatory and reparative properties reported. We also address the recent use of MenSCs in cell reprogramming. The main goal of this review is to contribute to the understanding of the identity and properties of MenSCs as well as to identify potential caveats and new venues that deserve to be explored to strengthen their potential applications.

Endometrial regenerative cells with galectin-9 high-expression attenuate experimental autoimmune hepatitis

Background

Autoimmune hepatitis (AIH) is a T cell-mediated immune disease that activates abnormally against hepatic antigens. We have previously reported that endometrial regenerative cells (ERCs) were a novel source of adult stem cells, which exhibiting with powerful immunomodulatory effects. Galectin-9 (Gal-9) is expressed in ERCs and plays an important role in regulating T cell response. This study aims to explore the role of ERCs in attenuation of AIH and to determine the potential mechanism of Gal-9 in ERC-mediated immune regulation.

Methods

ERCs were obtained from menstrual blood of healthy female volunteers. In vitro, ERCs were transfected with lentivirus vectors carrying LGALS9 gene and encoding green fluoresce protein (GFP-Gal-9-LVs) at a MOI 50, Gal-9 expression in ERCs was detected by ELISA and Q-PCR. CD4⁺ T cells isolated from C57BL/6 mouse spleen were co-cultured with ERCs. The proliferation of CD4⁺ T cells was detected by CCK-8 kit and the level of Lck/zap-70/LAT protein was measured by western blot. Furthermore, AIH was induced by ConA in C57BL/6 mice which were randomly assigned to untreated, unmodified ERC-treated and Gal-9 high-expressing ERC-treated groups. Histopathological score, liver function, CD4⁺/CD8⁺ cell infiltration in liver tissues, the proportion of immune cells in the spleen and liver, and ERC tracking were performed accordingly to assess the progression degree of AIH.

Results

After transfecting with GFP-Gal-9-LVs, Gal-9 expression in ERCs was significantly increased. Additionally, Gal-9 high-expressing ERCs effectively inhibited CD4⁺ T cell proliferation and downregulated CD4⁺ T cell active related proteins p-Lck/p-ZAP70/p-LAT in vitro. Furthermore, treatment with Gal-9 high-expressing ERCs restored liver function, ameliorated liver pathological damage, inhibit CD4⁺ and CD8⁺ T cell proliferation and suppress Th1 and Th17 cell response in the hepatitis mice. In addition, Gal-9 high-expressing ERCs further markedly enhanced the level of IL-10 but reduced the levels of IFN-γ, TNF-α, and IL-4 in mouse sera and liver. Cell tracking also showed that ERCs could migrate to the damaged liver organs.

Conclusions

The results suggested that Gal-9 was an essential modulator, which was required by ERCs in regulating T cell response and attenuating ConA-induced experimental hepatitis. And also, it provides a novel idea for the clinical treatment of AIH.

Oxymatrine protects cardiac allografts by regulating immunotolerant cells

Organ transplantation is an effective treatment strategy for patients with irreversible organ failure or congenital organ dysfunction. Oxymatrine (OMT) is a quinolizidine alkaloid with protective and anti-inflammatory effects on tissues and organs. The objective of this study was to investigate whether OMT could exert protective effects in cardiac allografts by regulating immune cells. In vitro cell proliferation and co-culture experiments were used to measure the effects of OMT on splenocyte proliferation and differentiation. In the in vivo study, C57BL/6 mice transplanted with BALB/c cardiac grafts were randomly divided into untreated, low-dose OMT treated, middle-dose OMT treated, high-dose OMT treated, and rapamycin-treated groups. Haematoxylin and eosin and immunohistochemical staining were used to assess pathological changes in the grafts, and fluorescence-activated cell sorting analysis was performed to measure the percentages of immune cells. The results showed that, in the in vitro study, OMT inhibited splenocyte proliferation, decreased the percentage of mature dendritic cells (DCs), and increased the percentage of regulatory T cells (Tregs) and regulatory B cells (Bregs). In the in vivo study, OMT exerted allograft protective effects by prolonging survival time, alleviating pathological damages to the cardiac allograft, decreasing intragraft CD3⁺ cell and increasing intragraft Foxp3⁺ cell infiltration, decreasing the percentages of mature DCs, increasing the percentages of Tregs and Bregs, and inhibiting the function of DCs. In conclusion, our study demonstrates that OMT exerted a protective effect on cardiac allografts by regulating immunotolerant cells. More in-depth studies of OMT may provide additional insight into the use of immunosuppressive drugs as a post-transplantation treatment strategy.

Endometrial stem/progenitor cells and their roles in immunity, clinical application, and endometriosis

Endometrial stem/progenitor cells have been proved to exist in periodically regenerated female endometrium and can be divided into three categories: endometrial epithelial stem/progenitor cells, CD140b+CD146+ or SUSD2+ endometrial mesenchymal stem cells (eMSCs), and side population cells (SPs). Endometrial stem/progenitor cells in the menstruation blood are defined as menstrual stem cells (MenSCs). Due to their abundant sources, excellent proliferation, and autotransplantation capabilities, MenSCs are ideal candidates for cell-based therapy in regenerative medicine, inflammation, and immune-related diseases. Endometrial stem/progenitor cells also participate in the occurrence and development of endometriosis by entering the pelvic cavity from retrograde menstruation and becoming overreactive under certain conditions to form new glands and stroma through clonal expansion. Additionally, the limited bone marrow mesenchymal stem cells (BMDSCs) in blood circulation can be recruited and infiltrated into the lesion sites, leading to the establishment of deep invasive endometriosis. On the other hand, cell derived from endometriosis may also enter the blood circulation to form circulating endometrial cells (CECs) with stem cell-like properties, and to migrate and implant into distant tissues. In this manuscript, by reviewing the available literature, we outlined the characteristics of endometrial stem/progenitor cells and summarized their roles in immunoregulation, regenerative medicine, and endometriosis, through which to provide some novel therapeutic strategies for reproductive and cancerous diseases.

The Use of Mesenchymal Stem Cells and their Derived Extracellular Vesicles in Cardiovascular Disease Treatment

BACKGROUND

Cardiovascular disease (CVD), including disorders of cardiac muscle and vascular, is the major cause of death globally. Many unsuccessful attempts have been made to intervene in the disease's pathogenesis and treatment. Stem cell-based therapies, as a regeneration strategy, cast a new hope for CVD treatment. One of the most well-known stem cells is mesenchymal stem cells (MSCs), classified as one of the adult stem cells and can be obtained from different tissues. These cells have superior properties, such as proliferation and highly specialized differentiation. On the other hand, they have the potential to modulate the immune system and anti-inflammatory activity. One of their most important features is the secreting the extracellular vesicles (EVs) like exosomes (EXOs) as an intercellular communication system mediating the different physiological and pathophysiological affairs.

METHODS

In this review study, the importance of MSC and its secretory exosomes for the treatment of heart disease has been together and specifically addressed and the use of these promising natural and accessible agents is predicted to replace the current treatment modalities even faster than we imagine.

RESULTS

MSC derived EXOs by providing a pro-regenerative condition allowing innate stem cells to repair damaged tissues successfully. As a result, MSCs are considered as the appropriate cellular source in regenerative medicine. In the plethora of experiments, MSCs and MSC-EXOs have been used for the treatment and regeneration of heart diseases and myocardial lesions.

CONCLUSION

Administration of MSCs has been provided a replacement therapeutic option for heart regeneration, obtaining great attention among the basic researcher and the medical doctors.

MiR-146a regulates regulatory T cells to suppress heart transplant rejection in mice

Regulatory T cells (Tregs), which characteristically express forkhead box protein 3 (Foxp3), are essential for the induction of immune tolerance. Here, we investigated microRNA-146a (miR-146a), a miRNA that is widely expressed in Tregs and closely related to their homeostasis and function, with the aim of enhancing the function of Tregs by regulating miR-146a and then suppressing transplant rejection. The effect of the absence of miR-146a on Treg function in the presence or absence of rapamycin was detected in both a mouse heart transplantation model and cell co-cultures in vitro. The absence of miR-146a exerted a mild tissue-protective effect by transiently prolonging allograft survival and reducing the infiltration of CD4⁺ and CD8⁺ T cells into the allografts. Meanwhile, the absence of miR-146a increased Treg expansion but impaired the ability of Tregs to restrict T helper cell type 1 (Th1) responses. A miR-146a deficiency combined with interferon (IFN)-γ blockade repaired the impaired Treg function, further prolonged allograft survival, and alleviated rejection. Importantly, miR-146a regulated Tregs mainly through the IFN-γ/signal transducer and activator of transcription (STAT) 1 pathway, which is implicated in Treg function to inhibit Th1 responses. Our data suggest miR-146a controls a specific aspect of Treg function, and modulation of miR-146a may enhance Treg efficacy in alleviating heart transplant rejection in mice.

Melatonin Synergizes With Mesenchymal Stromal Cells Attenuates Chronic Allograft Vasculopathy

Background

Chronic rejection characterized by chronic allograft vasculopathy (CAV) remains a major obstacle to long-term graft survival. Due to multiple complicated mechanisms involved, a novel therapy for CAV remains exploration. Although mesenchymal stromal cells (MSCs) have been ubiquitously applied to various refractory immune-related diseases, rare research makes a thorough inquiry in CAV. Meanwhile, melatonin (MT), a wide spectrum of immunomodulator, plays a non-negligible role in transplantation immunity. Here, we have investigated the synergistic effects of MT in combination with MSCs in attenuation of CAV.

Methods

C57BL/6 (B6) mouse recipients receiving BALB/c mouse donor aorta transplantation have been treated with MT and/or adipose-derived MSCs. Graft pathological changes, intragraft immunocyte infiltration, splenic immune cell populations, circulating donor-specific antibodies levels, cytokine profiles were detected on post-operative day 40. The proliferation capacity of CD4+ and CD8+ T cells, populations of Th1, Th17, and Tregs were also assessed in vitro.

Results

Grafts in untreated recipients developed a typical pathological feature of CAV characterized by intimal thickening 40 days after transplantation. Compared to untreated and monotherapy groups, MT in combination with MSCs effectively ameliorated pathological changes of aorta grafts indicated by markedly decreased levels of intimal hyperplasia and the infiltration of CD4+ cells, CD8+ cells, and macrophages, but elevated infiltration of Foxp3+ cells. MT either alone or in combination with MSCs effectively inhibited the proliferation of T cells, decreased populations of Th1 and Th17 cells, but increased the proportion of Tregs in vitro. MT synergized with MSCs displayed much fewer splenic populations of CD4+ and CD8+ T cells, Th1 cells, Th17 cells, CD4+ central memory T cells (Tcm), as well as effector memory T cells (Tem) in aorta transplant recipients. In addition, the percentage of splenic Tregs was substantially increased in the combination therapy group. Furthermore, MT combined with MSCs markedly reduced serum levels of circulating allospecific IgG and IgM, as well as decreased the levels of pro-inflammatory IFN-γ, TNF-α, IL-1β, IL-6, IL-17A, and MCP-1, but increased the level of IL-10 in the recipients.

Conclusions

These data suggest that MT has synergy with MSCs to markedly attenuate CAV and provide a novel therapeutic strategy to improve the long-term allograft acceptance in transplant recipients.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Galectin-9 is required for endometrial regenerative cells to induce long-term cardiac allograft survival in mice

Background

Endometrial regenerative cells (ERCs), a novel type of mesenchymal-like stem cells, were identified as an attractive candidate for immunoregulation and induction of cardiac allograft tolerance. However, the underlying mechanisms of ERCs in immune regulation still remain largely unclear. The present study is designed to determine whether the expression of Galectin-9 (Gal-9), a soluble tandem-repeat member of the galectin family, is crucial for ERC-based immunomodulation.

Methods

In this study, we measured Gal-9 expression on ERCs and then co-cultured Gal-9-ERCs, ERCs, and ERCs+lactose (Gal-9 blocker) with activated C57BL/6-derived splenocytes. Furthermore, we performed mouse heart transplantation between BALB/c (H-2^d) donor and C57BL/6 (H-2^b) recipient. ERCs were administrated 24 h after the surgery, either alone or in combination with rapamycin.

Results

Our data demonstrate that ERCs express Gal-9, and this expression is increased by IFN-γ stimulation in a dose-dependent manner. Moreover, both in vitro and in vivo results show that Gal-9-ERC-mediated therapy significantly suppressed Th1 and Th17 cell response, inhibited CD8⁺ T cell proliferation, abrogated B cell activation, decreased donor-specific antibody production, and enhanced the Treg population. The therapeutic effect of ERCs was further verified by their roles in prolonging cardiac allograft survival and alleviating graft pathological changes.

Conclusions

Taken together, these data indicate that Gal-9 is required for ERC-mediated immunomodulation and prevention of allograft rejection.

CD73 expression is critical to therapeutic effects of human endometrial regenerative cells in inhibition of cardiac allograft rejection in mice

The newly found mesenchymal‐like endometrial regenerative cells (ERCs) have been proved to induce immune tolerance in cardiac allograft transplantation. However, the therapeutic mechanism is not clear. The present study was undertaken to investigate whether ecto‐5′‐nucleotidase (CD73) expression on ERCs is critical to cardiac allograft protection. C57BL/6 mouse recipients receiving BALB/c mouse cardiac allografts were treated with unmodified ERCs or anti‐CD73 monoclonal antibodies (mAb) pretreated ERCs, respectively. It has been found that CD73 expression was critical to ERC‐induced attenuation of graft pathology. The blockage of CD73 expression on ERCs was related to the percentage decline of tolerogenic dendritic cells (Tol‐DCs), macrophages type 2 (M2), and regulatory T cells (Tregs). As compared with anti‐CD73 mAb pretreated ERCs group, CD73 expressing ERCs significantly increased the level of anti‐inflammatory cytokine IL‐10 but decreased levels of pro‐inflammatory cytokines including IFN‐γ and TNF‐α. In addition, CD73 expressing ERCs showed tissue protective function via the regulation of adenosine receptor expression which was related to the infiltration of CD4⁺ and CD8⁺ cells in the allografts. Furthermore, significant increase of A_2B receptors in the cardiac allograft was also associated with CD73 expressing ERC‐induced prolongation of cardiac allograft survival.

The Immunomodulatory Effects of Mesenchymal Stem Cells on Regulatory B Cells

The therapeutic potential of mesenchymal stem cells (MSCs) has been investigated in many preclinical and clinical studies. This potential is dominantly based on the immunosuppressive properties of MSCs. Although the therapeutic profiles of MSC transplantation are still not fully characterized, accumulating evidence has revealed that B cells change after MSC infusion, in particular inducing regulatory B cells (Bregs). The immunosuppressive effects of Bregs have been demonstrated, and these cells are being evaluated as new targets for the treatment of inflammatory diseases. MSCs are capable of educating B cells and inducing regulatory B cell production via cell-to-cell contact, soluble factors, and extracellular vesicles (EVs). These cells thus have the potential to complement each other's immunomodulatory functions, and a combined approach may enable synergistic effects for the treatment of immunological diseases. However, compared with investigations regarding other immune cells, investigations into how MSCs specifically regulate Bregs have been superficial and insufficient. In this review, we discuss the current findings related to the immunomodulatory effects of MSCs on regulatory B cells and provide optimal strategies for applications in immune-related disease treatments.

Mesenchymal stem cells transfected with sFgl2 inhibit the acute rejection of heart transplantation in mice by regulating macrophage activation

Background

Mesenchymal stem cells (MSCs) have become a promising candidate for cell-based immune therapy for acute rejection (AR) after heart transplantation due to possessing immunomodulatory properties. In this study, we evaluated the efficacy of soluble fibronectin-like protein 2 (sFgl2) overexpressing mesenchymal stem cells (sFgl2-MSCs) in inhibiting AR of heart transplantation in mice by regulating immune tolerance through inducing M2 phenotype macrophage polarization.

Methods and results

The sFgl2, a novel immunomodulatory factor secreted by regulatory T cells, was transfected into MSCs to enhance their immunosuppressive functions. After being co-cultured for 72 h, the sFgl2-MSCs inhibited M1 polarization whereas promoted M2 of polarization macrophages through STAT1 and NF-κB pathways in vitro. Besides, the sFgl2-MSCs significantly enhanced the migration and phagocytosis ability of macrophages stimulated with interferon-γ (IFN-γ) and lipopolysaccharide (LPS). Further, the application potential of sFgl2-MSCs in AR treatment was demonstrated by heterotopic cardiac transplantation in mice. The tissue damage and macrophage infiltration were evaluated by H&E and immunohistochemistry staining, and the secretion of inflammatory cytokines was analyzed by ELISA. The results showed that sFgl2-MSCs injected intravenously were able to locate in the graft, promote the M2 polarization of macrophages in vivo, regulate the local and systemic immune response, significantly protect tissues from damaging, and finally prolonged the survival time of mice heart grafts.

Conclusion

sFgl2-MSCs ameliorate AR of heart transplantation by regulating macrophages, which provides a new idea for the development of anti-AR treatment methods after heart transplantation.

Stromal Cell-Derived Factor-1 Enhances the Therapeutic Effects of Human Endometrial Regenerative Cells in a Mouse Sepsis Model

Endometrial regenerative cells (ERCs) are mesenchymal-like stromal cells obtained from human menstrual blood, whose positive therapeutic effects have been validated in several experimental models. Stromal cell-derived factor-1 (SDF-1), the ligand for CXCR4, plays an important role in the migration of mesenchymal stromal cells. The purpose of this study was to investigate the role of the SDF-1/CXCR4 pathway in the therapeutic effects of ERCs in a mouse sepsis model. Through preexperiment and confirmation, wild-type C57BL/6 mice were intraperitoneally injected with 10 mg/kg lipopolysaccharide (LPS). The therapeutic effects of ERCs with different pretreatments were evaluated by assessing sepsis-related symptoms, detecting tissue damage and measuring levels of inflammatory and oxidative stress-related factors. The in vitro experiments demonstrated that there was a much higher CXCR4 expression on ERCs when they were cocultured with SDF-1. The ex vivo experiment results showed that SDF-1 expression significantly increased in mouse tissues. Further experiments also confirmed that, compared with the unmodified ERC treatment group, SDF-1 pretreatment significantly enhanced the therapeutic effects of ERCs on alleviating sepsis symptoms, ameliorating pathological changes, reducing Bax level, and increasing Bcl-2 and PCNA expressions in mouse liver tissues. Furthermore, it was also found that SDF-1-pretreated ERCs contributed to reducing the levels of proinflammatory cytokines (TNF-α, IL-1β) and increasing the levels of anti-inflammatory factors (IL-4, IL10) in mouse serum, liver, and lung. Moreover, SDF-1-pretreated ERCs could also significantly decrease the levels of iNOS and MDA and increase the expression of Nrf2, HO-1, and SOD in liver tissues. Taken together, these results indicate that SDF-1 pretreatment plays a key role in improving the therapeutic effects of ERCs in alleviating sepsis-related symptoms, reducing tissue damage, regulating inflammatory imbalance, and relieving oxidative stress in a mouse sepsis model, which provides more possibilities for the clinical application of ERCs in sepsis and relevant diseases.

The Role of Macrophages in Oocyte Donation Pregnancy: A Systematic Review

The embryo of an oocyte donation (OD) pregnancy is completely allogeneic to the mother, which leads to a more serious challenge for the maternal immune system to tolerize the fetus. It is thought that macrophages are essential in maintaining a healthy pregnancy, by acting in immunomodulation and spiral arterial remodeling. OD pregnancies represent an interesting model to study complex immunologic interactions between the fetus and the pregnant woman since the embryo is totally allogeneic compared to the mother. Here, we describe a narrative review on the role of macrophages and pregnancy and a systematic review was performed on the role of macrophages in OD pregnancies. Searches were made in different databases and the titles and abstracts were evaluated by three independent authors. In total, four articles were included on OD pregnancies and macrophages. Among these articles, some findings are conflicting between studies, indicating that more research is needed in this area. From current research, we could identify that there are multiple subtypes of macrophages, having diverse biological effects, and that the ratio between subtypes is altered during gestation and in aberrant pregnancy. The study of macrophages’ phenotypes and their functions in OD pregnancies might be beneficial to better understand the maternal-fetal tolerance system.

PD-L1 is required for human endometrial regenerative cells-associated attenuation of experimental colitis in mice

Endometrial regenerative cells (ERCs) are easily isolated from menstrual blood, and can be cultured in large amounts. Although, ERCs can ameliorate DSS-induced colitis in mice, the molecular mechanism underlying ERCs-mediated immunosuppression is unclear. This study was aimed to assess the function of PD-L1 expressed on ERCs in colitis attenuation. ERCs with and without anti-PD-L1 mAb-pretreatment were administered to mice by injection at 2, 5 and 8 days after colitis induction by DSS treatment. Blood, spleen and colon samples were obtained 15 days post-DSS-induction. Then, clinicopathological alterations, cytokine levels, immune cell types and cell tracking were assessed. ERCs or ERCs preincubated with anti-PD-L1 antibody were co-cultured with splenocytes, whose phenotypes was analyzed by flow cytometry. We found that PD-L1 on ERCs was upregulated by IFN-γ stimulation. The transplanted PKH26-labeled ERCs were engrafted to the lung, liver, spleen and injured colon. Interestingly, ERC-based therapy markedly attenuated mouse colitis, but blockade of PD-L1 on ERCs with a specific monoclonal antibody conferred severe colitis to the animals. These effects of PD-L1 inhibition on colitis were associated with reduced amounts of pro-inflammatory cytokines and infiltrated immune cells, including CD3⁺CD4⁺ T lymphocytes, CD3⁺CD8⁺ T lymphocytes, CD11c⁺MHC-II⁺ Dendritic cells and F4/80⁺ macrophages, both in vivo and in vitro, as well as with elevated levels of anti-inflammatory cytokines and regulatory immune cells, including CD4⁺CD25⁺Foxp3⁺ Tregs and F4/80⁺CD206⁺ macrophages. These findings demonstrated that ERCs-based treatment promotes immune tolerance in mouse colitis, in association with PD-L1, thus indicating that PD-L1 modulates immunosuppression by ERCs.

SDF-1/CXCR4 axis enhances the immunomodulation of human endometrial regenerative cells in alleviating experimental colitis

Endometrial regenerative cells (ERCs) are a new type of mesenchymal-like stromal cells, and their therapeutic potential has been tested in a variety of disease models. SDF-1/CXCR4 axis plays a chemotaxis role in stem/stromal cell migration. The aim of the present study was to investigate the role of SDF-1/CXCR4 axis in the immunomodulation of ERCs on the experimental colitis. The immunomodulation of ERCs in the presence or absence of pretreatment of SDF-1 or AMD3100 was examined in both in vitro cell culture system and dextran sulphate sodium-induced colitis in mice. The results showed that SDF-1 increased the expression of CXCR4 on the surface of ERCs. As compared with normal ERCs, the SDF-1-treated, CXCR4 high-expressing ERCs more significantly suppressed dendritic cell population as well as stimulated both type 2 macrophages and regulatory T cells in vitro and in vivo. Meanwhile, SDF-1-pretreated ERCs increased the generation of anti-inflammatory factors (e.g., IL-4, IL-10) and decreased the pro-inflammatory factors (e.g., IL-6, TNF-α). In addition, SDF-1-pretreated CM-Dil-labeled ERCs were found to engraft to injured colon. Our results may suggest that an SDF-1-induced high level of CXCR4 expression enhances the immunomodulation of ERCs in alleviating experimental colitis in mice.

Therapeutic potential of menstrual blood-derived endometrial stem cells in cardiac diseases

Despite significant developments in medical and surgical strategies, cardiac diseases remain the leading causes of morbidity and mortality worldwide. Numerous studies involving preclinical and clinical trials have confirmed that stem cell transplantation can help improve cardiac function and regenerate damaged cardiac tissue, and stem cells isolated from bone marrow, heart tissue, adipose tissue and umbilical cord are the primary candidates for transplantation. During the past decade, menstrual blood-derived endometrial stem cells (MenSCs) have gradually become a promising alternative for stem cell-based therapy due to their comprehensive advantages, which include their ability to be periodically and non-invasively collected, their abundant source material, their ability to be regularly donated, their superior proliferative capacity and their ability to be used for autologous transplantation. MenSCs have shown positive therapeutic potential for the treatment of various diseases. Therefore, aside from a brief introduction of the biological characteristics of MenSCs, this review focuses on the progress being made in evaluating the functional improvement of damaged cardiac tissue after MenSC transplantation through preclinical and clinical studies. Based on published reports, we conclude that the paracrine effect, transdifferentiation and immunomodulation by MenSC promote both regeneration of damaged myocardium and improvement of cardiac function.

Human menstrual blood: a renewable and sustainable source of stem cells for regenerative medicine

Stem cells (SCs) play an important role in autologous and even allogenic applications. Menstrual blood discharge has been identified as a valuable source of SCs which are referred to as menstrual blood-derived stem cells (MenSCs). Compared to SCs from bone marrow and adipose tissues, MenSCs come from body discharge and obtaining them is non-invasive to the body, they are easy to collect, and there are no ethical concerns. There is, hence, a growing interest in the functions of MenSCs and their potential applications in regenerative medicine. This review presents recent progress in research into MenSCs and their potential application. Clinical indications of using MenSCs for various regenerative medicine applications are emphasized, and future research is recommended to accelerate clinical applications of MenSCs.

Treatment of experimental colitis by endometrial regenerative cells through regulation of B lymphocytes in mice

BACKGROUND

Endometrial regenerative cells (ERCs), a novel type of mesenchymal-like stem cell derived from menstrual blood, have been recently evaluated as an attractive candidate source in ulcerative colitis (UC); however, the mechanism is not fully understood. The present study was designed to investigate the effects of ERCs, especially on B-cell responses in UC.

METHODS

In this study, colitis was induced by administering 3% dextran sodium sulfate (DSS) via free drinking water for 7 days to BALB/c mice. In the treated group, mice were injected intravenously with 1 × 10⁶ ERCs on days 2, 5, and 8 after DSS induction. Therapeutic effects were assessed by monitoring body weight, disease activity, and pathological changes. Subpopulations of lymphocytes were determined by flow cytometry. IgG deposition in the colon was examined by immunohistochemistry staining. Cytokine levels were measured by enzyme-linked immunosorbent assay (ELISA), Western blot, or polymerase chain reaction (PCR) analysis. Adoptive transfer of regulatory B cells (Bregs) into colitis mice was performed.

RESULTS

Here, we demonstrated that ERC treatment prolonged the survival of colitis mice and attenuated disease activity with fewer pathological changes in colon tissue. ERCs decreased the proportion of immature plasma cells in the spleen and IgG deposition in the colon. On the other hand, ERCs increased the production of Bregs and the interleukin (IL)-10 level. Additionally, adoptive transferred Bregs exhibited significant therapeutic effects on colitis mice.

CONCLUSIONS

In conclusion, our results unravel the therapeutic role of ERCs on experimental colitis through regulating the B-lymphocyte responses.

Bone Marrow-Derived Mesenchymal Stem Cells Protect Islet Grafts Against Endoplasmic Reticulum Stress-Induced Apoptosis During the Early Stage After Transplantation

Early loss of grafted islets is the main obstacle to achieve favorable outcomes of islet transplantation. Mesenchymal stem cells are known to have a protective effect; however, its mechanism remains unclear. We hypothesized that bone marrow-derived mesenchymal stem cells (BMSCs) can protect grafted islets against endoplasmic reticulum stress (ERS)-induced apoptosis. In syngeneic streptozocin-induced diabetic BALB/c mice, islet grafts decreased blood glucose levels; however, the effect was not fully functional from the immediate post-transplant phase. β-Cell apoptosis was proven on days 1 and 3 after transplantation. Ultra-structural evidence of ERS was observed along with increased expressions of marker protein BIP and apoptosis-related protein CHOP. In contrast, BMSC co-transplantation maintained glucose hemostasis, inhibited apoptosis and alleviated ERS. In ex vivo culture, BMSCs improved viability of islets and decreased apoptosis. Increased ERS were observed in cultured islets exposed to hypoxia, but not in the islets cocultured with BMSCs. Furthermore, cocultured BMSCs protected islets against ERS-induced apoptosis as well as improved their insulin secretion, and BMSCs alleviated ERS by improving Myc expression through both stromal cell-derived factor 1 signal and contact effect. In conclusion, BMSCs protected the grafted islets against ERS-induced apoptosis during the early stage after transplantation. This study opens a new arena for ERS-targeted therapy to improve outcomes of islet transplantation. Stem Cells 2018;36:1045-1061.