CXCR2-Mediated Granulocytic Myeloid-Derived Suppressor Cells' Functional Characterization and Their Role in Maternal Fetal Interface

Kisspeptin prevents pregnancy loss by modulating the immune microenvironment at the maternal-fetal interface in recurrent spontaneous abortion

PROBLEM

Immune factors are crucial in the development of recurrent spontaneous abortion (RSA). This study aimed to investigate whether kisspeptin regulates immune cells at the maternal-fetal interface and whether G protein-coupled receptor 54 (GPR54) is involved in this process, through which it contributes to the pathogenesis of RSA.

METHOD OF STUDY

Normal pregnancy (NP) (CBA/J × BALB/c) and RSA (CBA/J × DBA/2) mouse models were established. NP mice received tail vein injections of PBS and KP234 (blocker of kisspeptin receptor), whereas RSA mice received PBS and KP10 (active fragment of kisspeptin). The changes in immune cells in mouse spleen and uterus were assessed using flow cytometry and immunofluorescence. The expression of critical cytokines was examined by flow cytometry, ELISA, Western blotting, and qPCR. Immunofluorescence was employed to detect the coexpression of FOXP3 and GPR54.

RESULTS

The findings revealed that the proportion of Treg cells, MDSCs, and M2 macrophages in RSA mice was lower than that in NP mice, but it increased following the tail vein injection of KP10. Conversely, the proportion of these cells was reduced in NP mice after the injection of KP234. However, the trend of γδT cell proportion change is contrary to these cells. Furthermore, FOXP3 and GPR54 were coexpressed in mouse spleen and uterus Treg cells as well as in the human decidua samples.

CONCLUSION

Our results suggest that kisspeptin potentially participates in the pathogenesis of RSA by influencing immune cell subsets at the maternal-fetal interface, including Treg cells, MDSC cells, γδT cells, and M2 macrophages.

Myeloid-derived suppressor cells as a potential biomarker for recurrent pregnancy loss and recurrent implantation failure: Increased levels of MDSCs in recurrent reproductive failure

PROBLEM

Recurrent pregnancy loss (RPL) and recurrent implantation failure (RIF) represent distinct clinical conditions with established definitions, both of which have been linked to an underlying pro-inflammatory state. This study aimed to explore the levels of monocytic-myeloid-derived suppressor cells (M-MDSCs) and regulatory T cells (TReg ) in a cohort of RPL and RIF women and their potential contribution to RPL and RIF.

METHOD OF STUDY

One hundred and eight non-pregnant women were evaluated: 40 RPL, 41 RIF, and 27 fertile healthy controls (HC). A multiparametric flow cytometry approach was utilized to measure and quantify the frequency of M-MDSCs and TReg cells. Cytokine levels in plasma samples were evaluated through a multiplex assay. M-MDSCs levels were significantly higher in RPL and RIF patients compared to HC.

RESULTS

M-MDSCs levels were significantly higher in RPL (9.4% [7-11.6]) and RIF (8.1% [5.9-11.6]) patients compared to HC (6% [4.2-7.6]). An optimal cut-off of 6.1% for M-MDSCs disclosed a sensitivity of 75.6% and 89.7% and a specificity of 57.7% and 57.7% in RIF and RPL groups, respectively. A significant negative correlation was observed between M-MDSCs and TReg (p = .002, r = -.51).

CONCLUSIONS

Our preliminary data allowed us to build a predictive model that may aid as a potential diagnostic tool in the clinic. These findings could provide a better understanding of these pathologies and a better definition of patients that could benefit from personalized treatments to promote pregnancy. Additional exploration and confirmation in distinct study groups are needed to fully assess the diagnostic capabilities of this biomarker.

Myeloid-derived suppressor cells: Are they involved in gestational diabetes mellitus?

Gestational diabetes mellitus (GDM) is currently the most common metabolic complication during pregnancy, with an increasing prevalence worldwide. Maternal immune dysregulation might be partly responsible for the pathophysiology of GDM. Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of cells, emerging as a new immune regulator with potent immunosuppressive capacity. Although the fate and function of these cells were primarily described in pathological conditions such as cancer and infection, accumulating evidences have spotlighted their beneficial roles in homeostasis and physiological conditions. Recently, several studies have explored the roles of MDSCs in the diabetic microenvironment. However, the fate and function of these cells in GDM are still unknown. The current review summarized the existing knowledges about MDSCs and their potential roles in diabetes during pregnancy in an attempt to highlight our current understanding of GDM-related immune dysregulation and identify areas where further study is required.

In vitro-Generated MDSCs Reduce the Pregnancy Complications in an Abortion-Prone Murine Model

Recurrent spontaneous abortion (RSA) is one of the major pregnancy-related complications. The roles of different immune cells have been studied in pregnancy complications. The current study aimed to investigate myeloid-derived suppressor cells (MDSCs) in a murine abortion model and introduce a therapeutic approach by using in vitro-generated MDSCs in this model. CBA/J × DBA/2 (abortion prone) and CBA/J × Balb/C (normal pregnancy) mice were used. The frequency of granulocytic MDSCs, monocytic MDSCs, and Tregs was checked in the bone marrow and uteroplacental tissue of mice on three gestational days (gd9.5, gd13.5, and gd17.5) using the flow cytometry approach. MDSCs were generated in vitro from bone marrow-isolated cells using GM-CSF and IL-6 cytokines. Abortion-prone mice were injected intravenously with in vitro-generated MDSCs at gd0.5, and pregnancy outcomes were recorded in treated mice. The frequency of G-MDSCs and M-MDSCs in the bone marrow of abortion-prone mice was decreased at gd9.5 (p = 0.026 and p = 0.05, respectively). In uteroplacental tissue, the frequency of G-MDSCs was significantly lower at gd9.5 and gd13.5 (p = 0.001, p = 0.029, respectively), while M-MDSCs only showed decreased number at gd9.5 (p = 0.05) in abortion-prone mice. Injection of in vitro-generated MDSCs resulted in the increased fetus and placenta weights (p = 0.049 and p = 0.012, respectively) but showed no effect on the number of live fetuses and abortion rate. The reduced frequency of both G-MDSCs and M-MDSCs in the bone marrow and at the feto-maternal interface is associated with pregnancy complications. In vitro-generated MDSCs could be considered as a potential approach to reduce these complications.

MDSCs in pregnancy and pregnancy-related complications: an update†

Maternal-fetal immune tolerance is a process that involves complex interactions of the immune system, and myeloid-derived suppressor cells have emerged as one of the novel immunomodulator in the maintenance of maternal-fetal immune tolerance. Myeloid-derived suppressor cells are myeloid progenitor cells with immunosuppressive activities on both innate and adaptive cells through various mechanisms. Emerging evidence demonstrates the accumulation of myeloid-derived suppressor cells during healthy pregnancy to establish maternal-fetal immune tolerance, placentation, and fetal-growth process. By contrast, the absence or decreased myeloid-derived suppressor cells in pregnancy complications like preeclampsia, preterm birth, stillbirth, and recurrent spontaneous abortion have been reported. Here, we have summarized the origin, mechanisms, and functions of myeloid-derived suppressor cells during pregnancy along with the recent advancements in this dynamic field. We also shed light on the immunomodulatory activity of myeloid-derived suppressor cells, which can be a foundation for potential therapeutic manipulation in immunological pregnancy complications.

Myeloidderived suppressor cells: Escorts at the maternal-fetal interface

Myeloid-derived suppressor cells (MDSCs) are a novel heterogenous group of immunosuppressive cells derived from myeloid progenitors. Their role is well known in tumors and autoimmune diseases. In recent years, the role and function of MDSCs during reproduction have attracted increasing attention. Improving the understanding of their strong association with recurrent implantation failure, pathological pregnancy, and neonatal health has become a focus area in research. In this review, we focus on the interaction between MDSCs and other cell types (immune and non-immune cells) from embryo implantation to postpartum. Furthermore, we discuss the molecular mechanisms that could facilitate the therapeutic targeting of MDSCs. Therefore, this review intends to encourage further research in the field of maternal-fetal interface immunity in order to identify probable pathways driving the accumulation of MDSCs and to effectively target their ability to promote embryo implantation, reduce pathological pregnancy, and increase neonatal health.

Pre-Existing Diabetes Mellitus, Hypertension and KidneyDisease as Risk Factors of Pre-Eclampsia: A Disease of Theories and Its Association with Genetic Polymorphism

Pre-existing diabetes, hypertension and kidney disorders are prominent risk factors of pre-eclampsia (PE). It is a multifactorial pregnancy disorder associated with high blood pressure, proteinuria, and multiorgan failure, which develops after the 20th week of pregnancy. It is one of the most feared pregnancy disorders, as it consumes thousands of fetomaternal lives per annum. According to clinical and pathological studies, the placenta appears to be a key player in the pathogenesis of PE; however, the exact origin of this disorder is still under debate. Defective placentation and angiogenesis are the hallmarks of PE progression. This angiogenic imbalance, together with maternal susceptibility, might determine the severity and clinical presentation of PE. This article comprehensively examines the mechanisms of pathogenesis of PE and current evidence of the factors involved in its progression. Finally, this article will explore the genetic association of PE, various candidate genes, their proposed mechanisms and variants involved in its pathogenesis.

The Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Oral Cavity and Abdominal Organs

CXCL1 is a CXC chemokine, CXCR2 ligand and chemotactic factor for neutrophils. In this paper, we present a review of the role of the chemokine CXCL1 in physiology and in selected major non-cancer diseases of the oral cavity and abdominal organs (gingiva, salivary glands, stomach, liver, pancreas, intestines, and kidneys). We focus on the importance of CXCL1 on implantation and placentation as well as on human pluripotent stem cells. We also show the significance of CXCL1 in selected diseases of the abdominal organs, including the gastrointestinal tract and oral cavity (periodontal diseases, periodontitis, Sjögren syndrome, Helicobacter pylori infection, diabetes, liver cirrhosis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), HBV and HCV infection, liver ischemia and reperfusion injury, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), obesity and overweight, kidney transplantation and ischemic-reperfusion injury, endometriosis and adenomyosis).

Intracellular Lipid Accumulation Drives the Differentiation of Decidual Polymorphonuclear Myeloid-Derived Suppressor Cells via Arachidonic Acid Metabolism

Decidual polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are essential to immune tolerance during pregnancy. A reduction in the number of these cells is associated with unexplained recurrent pregnancy loss (URPL). In our previous study, we reported that PMN-MDSCs are a group of mature neutrophils that are activated by the decidua microenvironment. In the present study, we show that the decidua microenvironment induces substantial lipid accumulation in neutrophils during their differentiation to PMN-MDSCs. Lower levels of lipid accumulation are detected in PMN-MDSCs from URPL patients, and the amount of lipid in the PMN-MDSCs is positively correlated with the proportion of PMN-MDSCs. Next, we demonstrate that decidua-derived IL6 with the presence of arachidonic acid upregulates fatty acid-binding protein 5 (FABP5) via the phosphorylation of signal transducer and activator of transcription 3 (STAT3). Fy -60ABP5 then continuously stimulates intracellular lipid accumulation. Increased intracellular lipid accumulation mediates arachidonic acid metabolism, a pathway that is significantly activated by the induction of the decidua microenvironment, to stimulate the synthesis of prostaglandin E2 (PGE2) and finally induce the differentiation of PMN-MDSCs. To summarize, decidua-derived IL6 facilitates the differentiation of PMN-MDSCs from neutrophils via the pSTAT3/FABP5/PGE2 pathway. Defects in the process may result in impaired differentiation and dysfunction of PMN-MDSCs in URPL. These findings enhance our understanding of the physiological mechanisms of immune tolerance in pregnancy and provide therapeutic options for URPL.

Neutrophils in pregnancy: New insights into innate and adaptive immune regulation

The immunology of pregnancy has been the focus of many studies to better understand how the mother is able to tolerate the presence of a semi-allogeneic fetus. Far from the initial view of pregnancy as a state of immunosuppression, successful fetal development from implantation to birth is now known to be under the control of an intricate balance of immune cells. The balance between pro-inflammatory functions used to promote embryo implantation and placental development and immunosuppressive activity to maintain maternal tolerance of the fetus is an immunological phenotype unique to pregnancy, which is dependent on the time of gestation. Neutrophils are one of a host of innate immune cells detected at the maternal-fetal interface, but very little is known of their function. In this review, we explore the emerging functions of neutrophils during pregnancy and their interactions with and regulation of T cells, a key adaptive immune cell population essential for the establishment of fetal-maternal tolerance.

MDSCs interactions with other immune cells and their role in maternal-fetal tolerance

MDSCs (myeloid-derived suppressor cells) are a population of immature and heterogeneous bone marrow cells with immunosuppressive functions, and they are mainly divided into two subgroups: granulocytic MDSCs (G-MDSCs) and monocytic MDSCs (M-MDSCs). Immunosuppression is the main and most important function of MDSCs, and they mainly exert an inhibitory effect through endoplasmic reticulum stress and some enzymes related to inhibitors, as well as some cytokines and other factors. In addition, MDSCs also interact with other immune cells, especially NK cells, DCs and Tregs, to participate in immune regulation. A large number of MDSCs are found during normal pregnancy. Combined with their immunosuppressive effects, these results suggest that MDSCs are likely to be closely related to maternal-fetal immune tolerance. This review mainly shows the interaction of MDSCs with other immune cells and the important role of MDSCs in maternal-fetal tolerance. The current research shows that MDSCs are mainly mediated by STAT3, HLA-G, CXCR2, Arg-1 and HIF1-α in immune regulation during pregnancy. Interpreting maternal-fetal tolerance from the perspective of MDSCs provides a special perspective for research on immune regulation and maternal-fetal tolerance of MDSCs to obtain a more comprehensive understanding of immune regulation and immune tolerance.

Decidua-derived granulocyte macrophage colony-stimulating factor induces polymorphonuclear myeloid-derived suppressor cells from circulating CD15+ neutrophils

STUDY QUESTION

Do decidua-derived factors stimulate the conversion of circulating neutrophils to polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in early human pregnancy?

SUMMARY ANSWER

Circulating neutrophils can acquire PMN-MDSC-like phenotypes and function via phosphorylated signal transducer and activator of transcription 5/programmed death ligand 2 (pSTAT5/PD-L2) signalling after stimulation with decidua-derived granulocyte macrophage colony-stimulating factor (GM-CSF).

WHAT IS KNOWN ALREADY

PMN-MDSCs are an important immunoregulatory cell type in early pregnancy. Neutrophils are of high heterogeneity and plasticity and can polarize to immunosuppressive PMN-MDSCs upon stimulation.

STUDY DESIGN, SIZE, DURATION

For analysis of myeloid-derived suppressor cell (MDSC) subset proportions, 12 endometrium tissues and 12 peripheral blood samples were collected from non-pregnant women, and 40 decidua tissues and 16 peripheral blood samples were obtained from women with normal early pregnancy undergoing elective surgical pregnancy termination for nonmedical reasons with gestation age of 6-10 weeks. Twenty-nine decidua tissues were collected for isolation of CD15+ PMN-MDSCs. Twenty endometrium tissues and 30 decidua tissues were collected for cytokine analysis, immunohistochemistry or neutrophil stimulation. Peripheral blood samples were obtained from 36 healthy donors for isolation of CD3+ T cells and CD15+ neutrophils.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The proportion of MDSC subsets in the decidua and peripheral blood of normal early pregnancy, endometrium and peripheral blood of non-pregnant women was analysed by flow cytometry. The phenotypes and function of decidual PMN-MDSCs and circulating neutrophils were compared by flow cytometry. Circulating neutrophils were stimulated with decidual explant supernatant (DES) and the phenotypes were measured by flow cytometry and immunofluorescence. The suppressive capacity of decidual PMN-MDSCs and DES-conditioned neutrophils was analysed by flow cytometry with or without anti-programmed cell death-1 (PD-1) antibody. Cytokines from DES and endometrial explant supernatant (EES) were detected by a Luminex assay. GM-CSF expression was determined by ELISA and immunohistochemistry. Neutrophils were stimulated with DES, EES, DES with anti-GM-CSF antibody or EES with GM-CSF. CD11b, lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), PD-L2 and pSTAT5 expression were measured by flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

The frequency of PMN-MDSCs was significantly increased in the decidua of early pregnancy compared with peripheral blood of non-pregnant women, the endometrium of non-pregnant women or peripheral blood during early pregnancy. Decidual PMN-MDSCs suppressed T-cell proliferation and cytokine production. Phenotypes of decidual PMN-MDSCs were similar to mature activated neutrophils. DES-induced CD11b, LOX-1, PD-L2 expression and STAT5 phosphorylation in neutrophils. The PD-L2 expression in neutrophils was dependent on STAT5 phosphorylation. Both decidual PMN-MDSCs and DES-conditioned neutrophils suppressed T-cell proliferation via PD-1 signalling. GM-CSF was up-regulated in the decidua and induced CD11b, LOX-1 and PD-L2 expression on neutrophils. DES significantly induced CD11b, LOX-1, PD-L2 expression and STAT5 phosphorylation. Anti-GM-CSF antibody remarkably blocked such stimulation in neutrophils. EES did not induce CD11b, LOX-1, PD-L2 expression or STAT5 phosphorylation, while GM-CSF treatment sufficiently stimulated CD11b, LOX-1, PD-L2 expression and STAT5 phosphorylation in neutrophils.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The study was based on in vitro experiments and we were not able to evaluate neutrophils differentiation to PMN-MDSCs in other sites before entering the maternal-foetal interface due to the limited availability of human samples. This needs to be explored using murine models.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study demonstrating that decidual PMN-MDSCs are a group of immunoregulatory cells with mature status, and that neutrophils can be induced to a PMN-MDSC-like phenotype with decidua-derived GM-CSF via pSTAT5/PD-L2 signalling. This study indicates that GM-CSF can facilitate immune tolerance of early pregnancy through regulating PMN-MDSCs and further provides a potential role of GM-CSF in prevention and treatment for pregnancy complications.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (81671481) and National Natural Science Foundation of China (81871179). All authors have no competing interests to declare.

Neutrophils: Need for Standardized Nomenclature

Neutrophils are the most abundant innate immune cell with critical anti-microbial functions. Since the discovery of granulocytes at the end of the nineteenth century, the cells have been given many names including phagocytes, polymorphonuclear neutrophils (PMN), granulocytic myeloid derived suppressor cells (G-MDSC), low density neutrophils (LDN) and tumor associated neutrophils (TANS). This lack of standardized nomenclature for neutrophils suggest that biologically distinct populations of neutrophils exist, particularly in disease, when in fact these may simply be a manifestation of the plasticity of the neutrophil as opposed to unique populations. In this review, we profile the surface markers and granule expression of each stage of granulopoiesis to offer insight into how each stage of maturity may be identified. We also highlight the remarkable surface marker expression profiles between the supposed neutrophil populations.

Therapies for tuberculosis and AIDS: myeloid-derived suppressor cells in focus

The critical role of suppressive myeloid cells in immune regulation has come to the forefront in cancer research, with myeloid-derived suppressor cells (MDSCs) as a main oncology immunotherapeutic target. Recent improvement and standardization of criteria classifying tumor-induced MDSCs have led to unified descriptions and also promoted MDSC research in tuberculosis (TB) and AIDS. Despite convincing evidence on the induction of MDSCs by pathogen-derived molecules and inflammatory mediators in TB and AIDS, very little attention has been given to their therapeutic modulation or roles in vaccination in these diseases. Clinical manifestations in TB are consequences of complex host-pathogen interactions and are substantially affected by HIV infection. Here we summarize the current understanding and knowledge gaps regarding the role of MDSCs in HIV and Mycobacterium tuberculosis (co)infections. We discuss key scientific priorities to enable application of this knowledge to the development of novel strategies to improve vaccine efficacy and/or implementation of enhanced treatment approaches. Building on recent findings and potential for cross-fertilization between oncology and infection biology, we highlight current challenges and untapped opportunities for translating new advances in MDSC research into clinical applications for TB and AIDS.

Myeloid-Derived Suppressor Cells Are a Major Source of Wnt5A in the Melanoma Microenvironment and Depend on Wnt5A for Full Suppressive Activity

Metastatic dissemination remains a significant barrier to successful therapy for melanoma. Wnt5A is a potent driver of invasion in melanoma and is believed to be secreted from the tumor microenvironment (TME). Our data suggest that myeloid-derived suppressor cells (MDSC) in the TME are a major source of Wnt5A and are reliant upon Wnt5A for multiple actions. Knockdown of Wnt5A specifically in the myeloid cells demonstrated a clear decrease in Wnt5A expression within the TME in vivo as well as a decrease in intratumoral MDSC and regulatory T cell (Treg). Wnt5A knockdown also decreased the immunosuppressive nature of MDSC and decreased expression of TGFβ1 and arginase 1. In the presence of Wnt5A-depleted MDSC, tumor-infiltrating lymphocytes expressed decreased PD-1 and LAG3, suggesting a less exhausted phenotype. Myeloid-specific Wnt5A knockdown also led to decreased lung metastasis. Tumor-infiltrating MDSC from control animals showed a strong positive correlation with Treg, which was completely ablated in animals with Wnt5A-negative MDSC. Overall, our data suggest that while MDSC contribute to an immunosuppressive and less immunogenic environment, they exhibit an additional function as the major source of Wnt5A in the TME. SIGNIFICANCE: These findings demonstrate that myeloid cells provide a major source of Wnt5A to facilitate metastatic potential in melanoma cells and rely on Wnt5A for their immunosuppressive function.

Myeloid-Derived Suppressor Cells in Pregnancy and the Neonatal Period

During pregnancy, the immune systems of mother and offspring are challenged by their close adjacency to balance tolerance and rejection. After birth the neonate has to continue this balance towards its new environment by tolerating commensals while rejecting pathogens and towards its developing tissues to avoid inflammatory damage while overcoming immunosuppression. Our group was the first to link immunosuppressive features of myeloid derived suppressor cells (MDSC) to materno-fetal tolerance, neonatal susceptibility to infection and inflammation control. Here we summarize recent advances in this dynamic field.

Upregulated TRAIL and Reduced DcR2 Mediate Apoptosis of Decidual PMN-MDSC in Unexplained Recurrent Pregnancy Loss

Myeloid-derived suppressor cells (MDSC), especially polymorphonuclear MDSC (PMN-MDSC), accumulate in maternal-fetal interface during pregnancy and are involved in the maintenance of immune tolerance. Decreased PMN-MDSC is associated with pregnancy complications such as unexplained recurrent pregnancy loss (URPL). In the present study we showed decreased PMN-MDSC in the URPL group compared with the normal pregnancy (NP) group, and PMN-MDSC was the major subset of MDSC in human decidua with potent immune suppression activity. We then performed gene expression profile and found that human decidual PMN-MDSC in the NP and URPL groups showed different gene and pathway signature, including apoptosis. Apoptosis of decidual PMN-MDSC was mediated by TNF-related apoptosis–induced ligand (TRAIL) in a Caspase 3 dependent manner. TRAIL was expressed in decidua and upregulated in decidua of the URPL group. Notably, of all the membrane TRAIL receptors, only DcR2 was down-regulated in PMN-MDSC in the URPL group. In vitro experiment demonstrated that DcR2 blockade sensitized PMN-MDSC to TRAIL-mediated apoptosis. Together, these data indicate that increased TRAIL and reduced DcR2 on PMN-MDSC sensitize PMN-MDSC response to TRAIL-induced apoptosis in the URPL group, which is responsible for decreased accumulation of PMN-MDSC in URPL.

Myeloid-derived suppressor cells in obstetrical and gynecological diseases

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid-origin cells which have immunosuppressive activities in several conditions, such as cancer and inflammation. Recent research has also associated MDSCs with numerous obstetrical and gynecological diseases. During pregnancy, MDSCs accumulate to ensure maternal-fetal immune tolerance, whereas they are decreased in patients who suffer from early miscarriage or pre-eclampsia. While the etiology of endometriosis is still unknown, abnormal accumulation of MDSCs in the peripheral blood and peritoneal fluid, alongside an increased level of reactive oxygen species (ROS), has been observed in these patients, which is central to the cellular immune regulations by MDSCs. Additionally, the regulation of MDSCs observed in tumours is also applicable to gynecologic neoplasms, including ovarian cancer and cervical cancer. More recently, emerging evidence has shown that there are high levels of MDSCs in premature ovarian failure (POF) and in vitro fertilization (IVF), but the underlying mechanisms are unknown. In this review, the generation and mechanisms of MDSCs are summarized. In particular, the modulation of these cells in immune-related obstetrical and gynecological diseases is discussed, including potential treatment options targeting MDSCs.

The health status alters the pituitary function and reproduction of mice in a Cxcr2-dependent manner

This study explores the effects of microbiota on reproductive function of Cxcr2 knockout animals. Cxcr2 is involved in the control of pituitary action and the subsequent development of mammary gland, uterus and ovary.

Microbiota and chronic infections can affect not only immune status, but also the overall physiology of animals. Here, we report that chronic infections dramatically modify the phenotype of Cxcr2 KO mice, impairing in particular, their reproduction ability. We show that exposure of Cxcr2 KO females to multiple types of chronic infections prevents their ability to cycle, reduces the development of the mammary gland and alters the morphology of the uterus due to an impairment of ovary function. Mammary gland and ovary transplantation demonstrated that the hormonal contexture was playing a crucial role in this phenomenon. This was further evidenced by alterations to circulating levels of sex steroid and pituitary hormones. By analyzing at the molecular level the mechanisms of pituitary dysfunction, we showed that in the absence of Cxcr2, bystander infections affect leukocyte migration, adhesion, and function, as well as ion transport, synaptic function behavior, and reproduction pathways. Taken together, these data reveal that a chemokine receptor plays a direct role in pituitary function and reproduction in the context of chronic infections.

MDSCs in pregnancy: Critical players for a balanced immune system at the feto-maternal interface

Myeloid-derived suppressor cells (MDSCs) have emerged as a new immune regulator at the feto-maternal interface. Although the phenotypes and functions of these cells were primarily studied in pathological conditions such as cancers and infections, new evidence has underscored their beneficial roles in homeostasis and physiological circumstances such as normal pregnancy. In this regard, studies have shown an increased number of MDSCs, particularly granulocytic MDSCs, at the feto-maternal interface. These cells participate in maintaining immunological tolerance between mother and semi-allograft fetus through various mechanisms. They further seem to play critical roles in placentation and fetus growth process. The absence or dysregulation of MDSCs during pregnancy have been reported in several pregnancy complications. These cells are also abundant in the cord blood of neonates so as to balance the immune responses and prevent aggressive inflammatory responses. The current review summarizes and organizes detailed data on MDSCs and their roles during pregnancy.

Myeloid-derived suppressor cells depletion may cause pregnancy loss via upregulating the cytotoxicity of decidual natural killer cells

PROBLEM

Maternal immune system tolerance to the semiallogeneic fetus is critical for a successful pregnancy. Studies have shown that myeloid-derived suppressor cells (MDSCs) play an important role in maintaining feto-maternal tolerance. However, the mechanisms remain poorly understood.

METHODS

Flow cytometry was used to evaluate the percentage of MDSCs in an allogeneic-normal-pregnant mouse model during different periods of gestation. We further assessed the percentage of MDSCs and their subtypes (granulocytic MDSCs [GR-MDSCs] and monocytic MDSCs [MO-MDSCs]) in a spontaneous abortion mouse model. The levels of the immunosuppressive molecules ARG-1, iNOS, IL-10, and TGF-β in MDSCs were also evaluated. MDSCs were depleted by anti-Gr-1 injection, and the resorption rate was calculated. The cytotoxicity of decidual natural killer (NK) cells was evaluated, and the percentage of regulatory NK (NKreg) cells and regulatory T lymphocytes (Tregs) were evaluated.

RESULTS

Myeloid-derived suppressor cells was accumulated in a time-dependent manner during pregnancy. However, the percentage of MDSCs was decreased in the spontaneous abortion mice compared with that in the control mice. In addition, the levels of ARG-1, iNOS, IL-10, and TGF-β in MDSCs decreased differentially. Finally, depletion of MDSCs was associated with increased rates of resorption and the proportion of NKreg and Treg cells in uterine tissues; meanwhile, the cytotoxicity of decidual NK cells was upregulated by increasing the level of perforin, granzyme B, and natural killer group protein 2 D-activating NK receptor (NKG2D).

CONCLUSION

Depletion of MDSCs may cause pregnancy loss, while upregulating the cytotoxicity of decidual NK cells and increasing NKreg and Treg cell numbers.

HIF-1α-Deficiency in Myeloid Cells Leads to a Disturbed Accumulation of Myeloid Derived Suppressor Cells (MDSC) During Pregnancy and to an Increased Abortion Rate in Mice

Abortions are the most important reason for unintentional childlessness. During pregnancy, maternal immune cells are in close contact to cells of the semi-allogeneic fetus. Dysregulation of the maternal immune system leading to defective adaptation to pregnancy often plays a role in pathogenesis of abortions. Myeloid-derived suppressor cells (MDSC) are myeloid cells that suppress functions of other immune cells, especially T-cells, thereby negatively affecting diseases such as cancer, sepsis or trauma. They seem, however, also necessary for maintenance of maternal-fetal tolerance. Mechanisms regulating MDSC expansion and function during pregnancy are only incompletely understood. In tumor environment, hypoxia is crucial for MDSC accumulation and activation. Hypoxia is also important for early placenta and embryo development. Effects of hypoxia are mediated through hypoxia-inducible factor 1α (HIF-1α). In the present study we aimed to examine the role of HIF-1α in myeloid cells for MDSC accumulation and MDSC function during pregnancy and for pregnancy outcome. We therefore used a mouse model with targeted deletion of HIF-1α in myeloid cells (myeloid HIF-KO) and analyzed blood, spleens and uteri of pregnant mice at gestational day E 10.5 in comparison to non-pregnant animals and wildtype (WT) animals. Further we analyzed pregnancy success by determining rates of failed implantation and abortion in WT and myeloid HIF-KO animals. We found that myeloid HIF-KO in mice led to an abrogated MDSC accumulation in the pregnant uterus and to impaired suppressive activity of MDSC. While expression of chemokine receptors and integrins on MDSC was not affected by HIF-1α, myeloid HIF-KO led to increased apoptosis rates of MDSC in the uterus. Myeloid-HIF-KO resulted in increased proportions of non-pregnant animals after positive vaginal plug and increased abortion rates, suggesting that activation of HIF-1α dependent pathways in MDSC are important for maintenance of pregnancy.

Association between polymorphisms in CXCR2 gene and preeclampsia

Background

Preeclampsia is a serious pregnancy‐specific syndrome with incompletely understood pathogenesis. Previous study has demonstrated that the decreased CXCR2 in preeclamptic placentas may contribute to the development of preeclampsia. The role of single nucleotide polymorphisms (SNPs) of CXCR2 gene in the pathogenesis of preeclampsia remains largely unexplored. Thus, we aimed to investigate the association between polymorphisms of CXCR2 gene and preeclampsia in Han Chinese women.

Methods

Totally 481 pregnant women, including 243 controls and 238 patients with preeclampsia were recruited. The rs1126579 and rs2230054 polymorphisms in CXCR2 gene were tested using polymerase chain reaction‐restriction fragment length polymorphism method.

Results

Significantly increased risk of preeclampsia was observed in the rs1126579 CC or TC/CC genotypes when compared with TT genotype (CC vs. TT: odss ratio [OR] = 2.11, 95% confidence interval [CI] = 1.18–3.76, p = 0.039; TC/CC vs. TT: OR = 1.89, 95% CI = 1.29–2.78, p = 0.001). Markedly higher risk of preeclampsia was found to be associated with rs1126579 TC genotype (TC vs. TT/CC: OR = 1.48, 95% CI = 1.04–2.12, p = 0.031). After stratification analysis, the different distribution of TC/CC genotypes was particularly significant in the severe preeclampsia group (OR = 2.15, 95% CI = 1.42–3.24, p < 0.01), the early‐onset severe preeclampsia group (OR = 1.97, 95% CI = 1.14–3.42, p = 0.013), and the late‐onset severe preeclampsia group (OR = 2.29, 95% CI = 1.39–3.78, p < 0.01). Besides, TC genotype carriers had a 1.55 fold increased risk of severe preeclampsia (95% CI = 1.06–2.27, p = 0.022) and a 1.80 fold increased risk of late onset severe preeclampsia (95% CI = 1.14–2.83, p = 0.01) than those of TT/CC genotype carriers.

Conclusions

Our study suggests a genetic association between rs1126579 polymorphism in CXCR2 gene and increased risk of preeclampsia. These data provide a new clue for future investigation.

Differential gene expression profile in monocytic myeloid-derived suppressor cells at maternal-fetal interface in a mouse model of spontaneous abortion

ABSTRACTBACKGROUND

Monocytic myeloid-derived suppressor cells (MO-MDSCs) play an important role in maintaining normal pregnancy. However, it is still not clear what kind of changes in MO-MDSCs may lead to miscarriage, and which gene expression changes take place when MO-MDSCs migrate to the uterus as bone marrow-derived cells.

METHODS

We used flow sorting technology to obtain MO-MDSCs from the maternal-fetal interface and bone marrow, respectively. Affymetrix 3'IVT expression profiling chip technology was used to detect the differential gene expression profiles in MO-MDSCs at the maternal-fetal interface in a mouse model of spontaneous abortion compared with the normal fertility control mice. We also compared the differential gene expression of MO-MDSCs at the maternal-fetal interface compared with bone marrow in the normal fertility control mice.

RESULTS

We found that 3,409 genes in MO-MDSCs were upregulated and 1,539 genes were downregulated at the maternal-fetal interface in the spontaneous abortion mice compared with the normal fertility mice. These genes are enriched in cellular components, biological processes, molecular functions, and protein binding, tumor signaling pathway, the PI3K-Akt signaling pathway, intratumoral proteoglycans, and extracellular matrix receptor interactions. Furthermore, we found that 270 genes in MO-MDSCs were upregulated and 383 genes were downregulated at the maternal-fetal interface in the normal fertility mice compared with those in the bone marrow. These genes are enriched in cellular components, biological processes, molecular functions, cell cycle, tumor transcriptional disorder, and cell adhesion molecules.

CONCLUSION

Differential gene expression in MO-MDSCs likely contributes to a successful pregnancy in fetal-maternal immunotolerance.

Semaphorin4D Inhibition Improves Response to Immune-Checkpoint Blockade via Attenuation of MDSC Recruitment and Function

Tumor infiltration by immunosuppressive myeloid cells, such as myeloid-derived suppressor cells (MDSCs), causes resistance to immunotherapy. Semaphorin4D, originally characterized for its axonal guidance properties, also contributes to endothelial cell migration and survival and modulates global immune cytokine profiles and myeloid cell polarization within the tumor microenvironment. Here, we show how a therapeutic murine Sema4D mAb improves responses to immune-checkpoint blockade (ICB) in two murine carcinoma models. Treatment of tumor-bearing mice with Sema4D mAb abrogated Ly6G^hi PMN-MDSC recruitment through reducing MAPK-dependent chemokine production by tumor cells in Murine oral cancer-1 (MOC1) tumors. PMN-MDSC suppressive capacity was reduced through inhibition of Sema4D-driven arginase expression. These changes led to enhanced tumor infiltration by CD8⁺ TIL and activation of tumor-draining lymph node T lymphocytes in response to tumor antigen. Sema4D mAb in combination with either CTLA-4 or PD-1 blockade enhanced rejection of tumors or tumor growth delay, resulting in prolonged survival with either treatment. This function of Sema4D mAb provides a rationale for its evaluation in combination with ICB to treat tumors with immunosuppressive myeloid infiltration.

Myeloid-derived suppressor cells coming of age

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells generated during a large array of pathologic conditions ranging from cancer to obesity. These cells represent a pathologic state of activation of monocytes and relatively immature neutrophils. MDSCs are characterized by a distinct set of genomic and biochemical features, and can, on the basis of recent findings, be distinguished by specific surface molecules. The salient feature of these cells is their ability to inhibit T cell function and thus contribute to the pathogenesis of various diseases. In this Review, we discuss the origin and nature of these cells; their distinctive features; and their biological roles in cancer, infectious diseases, autoimmunity, obesity and pregnancy.

Granulocytic myeloid-derived suppressor cells (GR-MDSC) accumulate in cord blood of preterm infants and remain elevated during the neonatal period

Preterm delivery is the leading cause of perinatal morbidity and mortality. Among the most important complications in preterm infants are peri- or postnatal infections. Myeloid-derived suppressor cells (MDSC) are myeloid cells with suppressive activity on other immune cells. Emerging evidence suggests that granulocytic MDSC (GR-MDSC) play a pivotal role in mediating maternal-fetal tolerance. The role of MDSC for postnatal immune-regulation in neonates is incompletely understood. Until the present time, nothing was known about expression of MDSC in preterm infants. In the present pilot study, we quantified GR-MDSC counts in cord blood and peripheral blood of preterm infants born between 23 + 0 and 36 + 6 weeks of gestation (WOG) during the first 3 months of life and analysed the effect of perinatal infections. We show that GR-MDSC are increased in cord blood independent of gestational age and remain elevated in peripheral blood of preterm infants during the neonatal period. After day 28 they drop to nearly adult levels. In case of perinatal or postnatal infection, GR-MDSC accumulate further and correlate with inflammatory markers C-reactive protein (CRP) and white blood cell counts (WBC). Our results point towards a role of GR-MDSC for immune-regulation in preterm infants and render them as a potential target for cell-based therapy of infections in these patients.

The mTOR signal regulates myeloid-derived suppressor cells differentiation and immunosuppressive function in acute kidney injury

The mammalian target of rapamycin (mTOR) signal controls innate and adaptive immune response in multiple immunoregulatory contexts. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells of potent immunosuppressive capacity. In this study, we aimed to investigate the role of MDSCs in the protection of acute kidney injury (AKI) and the regulation of mTOR signal on MDSC's protective role in this context. In mice AKI model, rapamycin administration was associated with improved renal function, restored histological damage and decreased CD4⁺ and CD8⁺ T-cell infiltration in kidney tissue. MDSCs, especially CD11b⁺Ly6G⁺Ly6C^low G-MDSCs were recruited to the injured kidney following the interaction of CXCL1, CXCL2 and their receptor CXCR2 after inhibiting mTOR signal with rapamycin treatment. The adoptive transfer of rapamycin-treated MDSCs into the mice with AKI significantly improved the renal function, ameliorated histologic damages and limited the infiltration of T cells in kidney tissue. In addition, the expression of pro-inflammatory cytokines IL-1β and IFN-γ mRNA was downregulated while the expression of TGF-β1 and Foxp3 mRNA was upregulated in kidney tissue after transferring rapamycin-treated MDSCs. Adoptive transfer of rapamycin-treated MDSCs also downregulated the serum levels of IL-1β, IL-6 and IFN-γ and upregulated the serum levels of TGF-β1 compared with the IR group and PBS-treated MDSC group. In in vitro study, inhibiting mTOR signal regulated the induction of MDSC towards the CD11b⁺Ly6G⁺Ly6C^low G-MDSC subset. The ability to suppress T-cell proliferation of both bone marrow–derived CD11b⁺Ly6G⁺Ly6C^low G-MDSCs and CD11b⁺Ly6G^-Ly6C^high M-MDSCs was enhanced by mTOR signal inhibition via upregulating the expression of Arginase-1 and iNOS. Accordingly, both G-MDSCs and M-MDSCs presented downregulated runx1 gene expression after rapamycin treatment. Taken together, our results demonstrated that MDSCs ameliorated AKI and the protective effect was enhanced by mTOR signal inhibition via promoting MDSCs recruitment, regulating the induction of MDSCs and strengthening their immunosuppressive activity.

Protective function of interleukin 27 in colitis-associated cancer via suppression of inflammatory cytokines in intestinal epithelial cells

Numerous studies have demonstrated that inflammation contributes to a variety of cancer formation, among them, colitis-associated cancer (CAC) represents a typical inflammation-related cancer. Interleukin 27 (IL-27) has been demonstrated to play an important role in inflammation-related disease. The effect of IL-27 in intestinal inflammation is controversial and its role in CAC is not elucidated yet. In our present study, we found that IL-27 has protective function in murine model of CAC through suppression of inflammatory cytokines in intestinal epithelial cells (IECs). IL-27Rα (WSX-1) deficiency promotes the CAC development in mice, which is driven by enhanced tumor cell proliferation, more intensive myeloid-derived suppressor cells (MDSC) accumulation in colon lamina propria and higher level of inflammatory cytokines and chemokines in IECs. The levels of IL-6, TNF-α, GM-CSF and CXCL1 triggered in vitro by toll-like receptor ligands are significantly upregulated in IECs from WSX-1 KO mice. Removal of commensal microorganism through antibiotic treatment in mice to eliminate TLR ligands deprives the protective function of IL-27 on CAC tumor growth. Thus, IL-27 suppresses CAC formation through an anti-inflammation mechanism targeting IECs and in turn resists the tumorigenesis. Hence, our study explained how IL-27 exerts its anti-inflammatory function on epithelial cells to fight against chronic-inflammation-associated cancer, which might provide new insights on the potential therapeutic strategies for cancer.

CCR5 ameliorates Japanese encephalitis via dictating the equilibrium of regulatory CD4(+)Foxp3(+) T and IL-17(+)CD4(+) Th17 cells

Background

CCR5 is a CC chemokine receptor involved in the migration of effector leukocytes including macrophages, NK, and T cells into inflamed tissues. Also, the role of CCR5 in CD4⁺Foxp3⁺ regulatory T cell (Treg) homing has recently begun to grab attention. Japanese encephalitis (JE) is defined as severe neuroinflammation of the central nervous system (CNS) following infection with mosquito-borne flavivirus JE virus. However, the potential contribution of CCR5 to JE progression via mediating CD4⁺Foxp3⁺ Treg homing has not been investigated.

Methods

Infected wild-type (Ccr5^+/+) and CCR5-deficient (Ccr5^−/−) mice were examined daily for mortality and clinical signs, and neuroinflammation in the CNS was evaluated by infiltration of inflammatory leukocytes and cytokine expression. In addition, viral burden, NK- and JEV-specific T cell responses were analyzed. Adoptive transfer of CCR5⁺CD4⁺Foxp3⁺ Tregs was used to evaluate the role of Tregs in JE progression.

Results

CCR5 ablation exacerbated JE without altering viral burden in the extraneural and CNS tissues, as manifested by increased CNS infiltration of Ly-6C^hi monocytes and Ly-6G^hi granulocytes. Compared to Ccr5^+/+ mice, Ccr5^−/− mice unexpectedly showed increased responses of IFN-γ⁺NK and CD8⁺ T cells in the spleen, but not CD4⁺ T cells. More interestingly, CCR5-ablation resulted in a skewed response to IL-17⁺CD4⁺ Th17 cells and correspondingly reduced CD4⁺Foxp3⁺ Tregs in the spleen and brain, which was closely associated with exacerbated JE. Our results also revealed that adoptive transfer of sorted CCR5⁺CD4⁺Foxp3⁺ Tregs into Ccr5^−/− mice could ameliorate JE progression without apparently altering the viral burden and CNS infiltration of IL-17⁺CD4⁺ Th17 cells, myeloid-derived Ly-6C^hi monocytes and Ly-6G^hi granulocytes. Instead, adoptive transfer of CCR5⁺CD4⁺Foxp3⁺ Tregs into Ccr5^−/− mice resulted in increased expression of anti-inflammatory cytokines (IL-10 and TGF-β) in the spleen and brain, and transferred CCR5⁺ Tregs were found to produce IL-10.

Conclusions

CCR5 regulates JE progression via governing timely and appropriate CNS infiltration of CD4⁺Foxp3⁺ Tregs, thereby facilitating host survival. Therefore, this critical and extended role of CCR5 in JE raises possible safety concerns regarding the use of CCR5 antagonists in human immunodeficiency virus (HIV)-infected individuals who inhabit regions in which both HIV and flaviviruses, such as JEV and West Nile virus, are endemic.