Programming of human monocytes by the uteroplacental environment

Pro- and Anti-Inflammatory Cytokines in the Context of NK Cell-Trophoblast Interactions

During pregnancy, uterine NK cells interact with trophoblast cells. In addition to contact interactions, uterine NK cells are influenced by cytokines, which are secreted by the cells of the decidua microenvironment. Cytokines can affect the phenotypic characteristics of NK cells and change their functional activity. An imbalance of pro- and anti-inflammatory signals can lead to the development of reproductive pathology. The aim of this study was to assess the effects of cytokines on NK cells in the presence of trophoblast cells in an in vitro model. We used TNFα, IFNγ, TGFβ and IL-10; the NK-92 cell line; and peripheral blood NK cells (pNKs) from healthy, non-pregnant women. For trophoblast cells, the JEG-3 cell line was used. In the monoculture of NK-92 cells, TNFα caused a decrease in CD56 expression. In the coculture of NK cells with JEG-3 cells, TNFα increased the expression of NKG2C and NKG2A by NK-92 cells. Under the influence of TGFβ, the expression of CD56 increased and the expression of NKp30 decreased in the monoculture. After the preliminary cultivation of NK-92 cells in the presence of TGFβ, their cytotoxicity increased. In the case of adding TGFβ to the PBMC culture, as well as coculturing PBMCs and JEG-3 cells, the expression of CD56 and NKp44 by pNK cells was reduced. The differences in the effects of TGFβ in the model using NK-92 cells and pNK cells may be associated with the possible influence of monocytes or other lymphoid cells from the mononuclear fraction.

Association between phagocytic activity of monocytes and days to conception after parturition in dairy cows when considering the hormonal and metabolic milieu

The nutritional conditions and immune status of dairy cows affect reproductive performance. This study was conducted with the aim to analyze the phagocytic activity (PA) and phagocytic capacity (PC) of circulating monocytes after the period of transition from pregnancy to lactation, to evaluate possible associations with duration of time period to conception following parturition. Results indicated PA was not associated with duration of time period to conception following parturition. In contrast, cows with a lesser PC conceived earlier (98 ± 9 days in milk, DIM) than those with a greater PC (168 ± 15 DIM). Based on these results, to analyze the association of the hormonal and metabolic milieu with the PA and PC, the animals were grouped considering the days to conception following parturition. In the group with the greater number of days to conception (>168 DIM), the PA was associated with concentrations of progesterone and beta-hydroxybutyrate (BHB) at 90 DIM and glucose at 120 DIM, whereas PC was associated with the concentrations of progesterone, cortisol and glucose at 90 DIM, non-esterified fatty acids (NEFA) at 120 DIM, 17β-estradiol at 150 DIM, and 17β-estradiol and BHB at 180 DIM. Overall, these results represent a new perspective related to the reproductive performance of dairy cows. The modifications of cellular functions may be useful for predicting the onset of health complications in dairy cows and to manage cows in ways that result in an enhanced fertility during the subsequent lactational period.

SARS-CoV-2 Infection in Pregnant Women: Neuroimmune-Endocrine Changes at the Maternal-Fetal Interface

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has devastating effects on the population worldwide. Given this scenario, the extent of the impact of the disease on more vulnerable individuals, such as pregnant women, is of great concern. Although pregnancy may be a risk factor in respiratory virus infections, there are no considerable differences regarding COVID-19 severity observed between pregnant and nonpregnant women. In these circumstances, an emergent concern is the possibility of neurodevelopmental and neuropsychiatric harm for the offspring of infected mothers. Currently, there is no stronger evidence indicating vertical transmission of SARS-CoV-2; however, the exacerbated inflammatory response observed in the disease could lead to several impairments in the offspring's brain. Furthermore, in the face of historical knowledge on possible long-term consequences for the progeny's brain after infection by viruses, we must consider that this might be another deleterious facet of COVID-19. In light of neuroimmune interactions at the maternal-fetal interface, we review here the possible harmful outcomes to the offspring brains of mothers infected by SARS-CoV-2.

Follicular-phase endometrial scratching: a truncated randomized controlled trial

STUDY QUESTION

Does intentional endometrial injury (scratching) during the follicular phase of ovarian stimulation (OS) increase the clinical pregnancy rate (CPR) in ART?

SUMMARY ANSWER

CPR did not vary between the endometrial injury and the control group, but the trial was underpowered due to early termination because of a higher clinical miscarriage rate observed in the endometrial injury arm after a prespecified interim analysis.

WHAT IS KNOWN ALREADY

Intentional endometrial injury has been put forward as an inexpensive clinical tool capable of enhancing endometrial receptivity. However, despite its widespread use, the benefit of endometrial scratching remains controversial, with several recent randomized controlled trials (RCTs) being unable to confirm its added value. So far, most research has focused on endometrial scratching during the luteal phase of the cycle preceding the one with embryo transfer (ET), while only a few studies investigated in-cycle injury during the follicular phase of OS. Also, the persistence of a scratch effect in subsequent treatment cycles remains unclear and possible harms have been insufficiently studied.

STUDY DESIGN, SIZE, DURATION

This RCT was performed in a tertiary hospital setting between 3 April 2014 and 8 October 2017. A total of 200 women (100 per study arm) undergoing IVF/ICSI in a GnRH antagonist suppressed cycle followed by fresh ET were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were randomized with a 1:1 allocation ratio to either undergo a pipelle endometrial biopsy between Days 6 and 8 of OS or to be in the control group.The primary outcome was CPR. Secondary outcomes included biochemical pregnancy rate, live birth rate (LBR), early pregnancy loss (biochemical pregnancy losses and clinical miscarriages), excessive procedure pain/bleeding and cumulative reproductive outcomes within 6 months of the study cycle.

MAIN RESULTS AND THE ROLE OF CHANCE

The RCT was stopped prematurely by the trial team after the second prespecified interim analysis raised safety concerns, namely a higher clinical miscarriage rate in the intervention group. The intention-to-treat CPR was similar between the biopsy and the control arm (respectively, 44 versus 40%, P = 0.61, risk difference = 3.6 with 95% confidence interval = -10.1;17.3), as was the LBR (respectively, 32 versus 36%, P = 0.52). The incidence of a biochemical pregnancy loss was comparable between both groups (10% in the intervention group versus 15% in the control, P = 0.49), but clinical miscarriages occurred significantly more frequent in the biopsy group (25% versus 8%, P = 0.032). In the intervention group, 3% of the patients experienced excessive procedure pain and 5% bleeding. The cumulative LBR taking into account all conceptions (spontaneous or following ART) within 6 months of randomization was not significantly different between the biopsy and the control group (54% versus 60%, respectively, P = 0.43).

LIMITATIONS, REASONS FOR CAUTION

The trial was stopped prematurely due to safety concerns after the inclusion of 200 of the required 360 patients. Not reaching the predefined sample size implies that definite conclusions on the outcome parameters cannot be drawn. Furthermore, the pragmatic design of the study may have limited the detection of specific subgroups of women who may benefit from endometrial scratching.

WIDER IMPLICATIONS OF THE FINDINGS

Intentional endometrial injury during the follicular phase of OS warrants further attention in future research, as it may be harmful. These findings should be taken in consideration together with the growing evidence from other RCTs that scratching may not be beneficial.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by 'Fonds Wetenschappelijk Onderzoek' (FWO, Flanders, Belgium, 11M9415N, 1524417N). None of the authors have a conflict of interest to declare with regard to this study.

The expression of intracellular cytokines of decidual natural killer cells in unexplained recurrent pregnancy loss

OBJECTIVE

This study aims to investigate the expression levels of TNF-α, IFN-γ, IL-4, and IL-10 in dNK cells and determine whether or not the MAPK signal pathway is involved in the regulation of cytokine secretion by dNK cells at the maternal-fetal interface.

METHODS

In this study, we collected decidua specimens from patients with apparently normal pregnant and unexplained recurrent pregnancy loss (URPL) and extracted dNK cells by enzymatic digestion. Then the expression of cytokines were analyzed by flow cytometry and Real-Time PCR respectively.

RESULTS

The secretions of both IFN-γ and TNF-α in dNK cells in URPL were significantly higher than those in normal pregnancy. Furthermore, p38/MAPK inhibitors can inhibit the secretion of four cytokines in normal pregnancy, while in URPL cases, p38/MAPK inhibitors only significantly inhibit the secretion of IL-4 and IFN-γ. ERK inhibitors had no effect on the expression of all four cytokines and JNK/MAPK inhibitors varied on different cytokines.

CONCLUSION

URPL is associated with a NK1 cytokine profile. MAPK signaling pathway is involved in the regulation of cytokine secretion by decidual NK cells at maternal-fetal interface.

Novel pathways of inflammation in human fetal membranes associated with preterm birth and preterm pre-labor rupture of the membranes

Spontaneous preterm birth (PTB) and preterm pre-labor rupture of the membranes (pPROM) are major pregnancy complications. Although PTB and pPROM have common etiologies, they arise from distinct pathophysiologic pathways. Inflammation is a common underlying mechanism in both conditions. Balanced inflammation is required for fetoplacental growth; however, overwhelming inflammation (physiologic at term and pathologic at preterm) can lead to term and preterm parturition. A lack of effective strategies to control inflammation and reduce the risk of PTB and pPROM suggests that there are several modes of the generation of inflammation which may be dependent on the type of uterine tissue. The avascular fetal membrane (amniochorion), which provides structure, support, and protection to the intrauterine cavity, is one of the key contributors of inflammation. Localized membrane inflammation helps tissue remodeling during pregnancy. Two unique mechanisms that generate balanced inflammation are the progressive development of senescence (aging) and cyclic cellular transitions: epithelial to mesenchymal (EMT) and mesenchymal to epithelial (MET). The intrauterine build-up of oxidative stress at term or in response to risk factors (preterm) can accelerate senescence and promote a terminal state of EMT, resulting in the accumulation of inflammation. Inflammation degrades the matrix and destabilizes membrane function. Inflammatory mediators from damaged membranes are propagated via extracellular vesicles (EV) to maternal uterine tissues and transition quiescent maternal uterine tissues into an active state of labor. Membrane inflammation and its propagation are fetal signals that may promote parturition. This review summarizes the mechanisms of fetal membrane cellular senescence, transitions, and the generation of inflammation that contributes to term and preterm parturitions.

Trophoblast-secreted soluble-PD-L1 modulates macrophage polarization and function

Decidual macrophages are in close contact with trophoblast cells during placenta development, and an appropriate crosstalk between these cellular compartments is crucial for the establishment and maintenance of a healthy pregnancy. During different phases of gestation, macrophages undergo dynamic changes to adjust to the different stages of fetal development. Trophoblast-secreted factors are considered the main modulators responsible for macrophage differentiation and function. However, the phenotype of these macrophages induced by trophoblast-secreted factors and the factors responsible for their polarization has not been elucidated. In this study, we characterized the phenotype and function of human trophoblast-induced macrophages. Using in vitro models, we found that human trophoblast-educated macrophages were CD14⁺ CD206⁺ CD86^- and presented an unusual transcriptional profile in response to TLR4/LPS activation characterized by the expression of type I IFN-β expression. IFN-β further enhances the constitutive production of soluble programmed cell death ligand 1 (PD-L1) from trophoblast cells. PD-1 blockage inhibited trophoblast-induced macrophage differentiation. Soluble PD-L1 (sPD-L1) was detected in the blood of pregnant women and increased throughout the gestation. Collectively, our data suggest the existence of a regulatory circuit at the maternal fetal interface wherein IFN-β promotes sPD-L1 expression/secretion by trophoblast cells, which can then initiate a PD-L1/PD-1-mediated macrophage polarization toward an M2 phenotype, consequently decreasing inflammation. Macrophages then maintain the expression of sPD-L1 by the trophoblasts through IFN-β production induced through TLR4 ligation.

Role of Macrophages in Pregnancy and Related Complications

Macrophages (MФs) are the leukocytes produced from differentiation of monocytes and are located in almost all tissues of human body. They are involved in various processes, such as phagocytosis, innate and adaptive immunity, proinflammatory (M1) and anti-inflammatory (M2) activity, depending on the tissue microenvironment. They play a crucial role in pregnancy, and their dysfunction or alteration of polarity is involved in pregnancy disorders, like preeclampsia, recurrent spontaneous abortion, infertility, intrauterine growth restriction, and preterm labor. About 50-60% of decidual leukocytes are natural killer (NK) cells followed by MФs (the second largest population). MФs are actively involved in trophoblast invasion, tissue and vascular remodeling during early pregnancy, besides their role as major antigen-presenting cells in the decidua. These cells have different phenotypes and polarities in different stages of pregnancy. They have also been observed to enhance tumor growth by their anti-inflammatory activity (M2 type) and prevent immunogenic rejection. Targeted alteration of polarity (M1-M2 or vice versa) could be a major focus in the future treatment of pregnancy complications. This review is focused on the role of MФs in pregnancy, their involvement in pregnancy disorders, and decidual MФs as possible therapeutic targets for the treatment of pregnancy complications.

Human Decidual Stromal Cells as a Component of the Implantation Niche and a Modulator of Maternal Immunity

The human decidua is a specialized tissue characterized by embryo-receptive properties. It is formed during the secretory phase of menstrual cycle from uterine mucosa termed endometrium. The decidua is composed of glands, immune cells, blood and lymph vessels, and decidual stromal cells (DSCs). In the process of decidualization, which is controlled by oestrogen and progesterone, DSCs acquire specific functions related to recognition, selection, and acceptance of the allogeneic embryo, as well as to development of maternal immune tolerance. In this review we discuss the relationship between the decidualization of DSCs and pathological obstetrical and gynaecological conditions. Moreover, the critical influence of DSCs on local immune cells populations as well as their relationship to the onset and maintenance of immune tolerance is described.

Human trophoblast cells induced MDSCs from peripheral blood CD14(+) myelomonocytic cells via elevated levels of CCL2

Successful human pregnancy requires the maternal immune system to recognize and tolerate the semi-allogeneic fetus. Myeloid-derived suppressor cells (MDSCs), which are capable of inhibiting T-cell responses, are highly increased in the early stages of pregnancy. Although recent reports indicate a role for MDSCs in fetal-maternal tolerance, little is known about the expansion of MDSCs during pregnancy. In the present study, we demonstrated that the trophoblast cell line HTR8/SVneo could instruct peripheral CD14(+) myelomonocytic cells toward a novel subpopulation of MDSCs, denoted as CD14(+)HLA-DR(-/low) cells, with suppressive activity and increased expression of IDO1, ARG-1, and COX2. After interaction with HTR8/SVneo cells, CD14(+) myelomonocytic cells secrete high levels of CCL2, promoting the expression of signal transducer and activator of transcription 3. We utilized a neutralizing monoclonal antibody to reveal the prominent role of CCL2 in the induction of CD14(+)HLA-DR(-/low) MDSCs. In combination, the results of the present study support a novel role for the cross-talk between the trophoblast cell line HTR8/SVneo and maternal CD14(+) myelomonocytic cells in initiating MDSCs induction, prompting a tolerogenic immune response to ensure a successful pregnancy.

HLA-G Orchestrates the Early Interaction of Human Trophoblasts with the Maternal Niche

Extravillous trophoblasts (EVTs) play a central role in educating maternal leukocytes, endometrial stromal and endothelial cells to generate a receptive decidual microenvironment tailored to accept the semi-allogeneic fetus. HLA-G, a non-classical HLA class I molecule endowed with immune-regulatory functions, is primarily expressed on EVTs lining the placenta and on the naturally occurring tolerogenic dendritic cells, named DC-10, which are enriched in the human first trimester decidua. Decidual DC-10 are involved in HLA-G-mediated tolerance at the maternal–fetal interface. EVTs not only establish a tolerogenic microenvironment through the interaction with maternal innate and adaptive cells but also orchestrate placenta vascular and tissue remodeling, leading to a successful pregnancy. Here, we discuss the potential implications of the HLA-G-mediated cross-talk among the cells present at the maternal–fetal interface, and its role in maintaining a positive relationship between the mother and the fetus.

The contribution of the maternal immune system to the establishment of pregnancy in cattle

Immune cells play an integral role in affecting successful reproductive function. Indeed, disturbed or aberrant immune function has been identified as primary mechanisms behind infertility. In contrast to the extensive body of literature that exists for human and mouse, studies detailing the immunological interaction between the embryo and the maternal endometrium are quite few in cattle. Nevertheless, by reviewing the existing studies and extrapolating from sheep, pig, mouse, and human data, we can draw a reasonably comprehensive picture. Key contributions of immune cell populations include granulocyte involvement in follicle differentiation and gamete transfer, monocyte invasion of the peri-ovulatory follicle and their subsequent role in corpus luteum formation and the pivotal roles of maternal macrophage and dendritic cells in key steps of the establishment of pregnancy, particularly, the maternal immune response to the embryo. These contributions are reviewed in detail below and key findings are discussed.

Biopsy-induced inflammatory conditions improve endometrial receptivity: the mechanism of action

A decade ago, we first reported that endometrial biopsy significantly improves the success of pregnancy in IVF patients with recurrent implantation failure, an observation that was later confirmed by others. Recently, we have demonstrated that this treatment elevated the levels of endometrial pro-inflammatory cytokines and increased the abundance of macrophages (Mac) and dendritic cells (DCs). We therefore hypothesised that the biopsy-related successful pregnancy is secondary to an inflammatory response, and aimed at deciphering its mechanism of action. Supporting our hypothesis, we found that the pro-inflammatory TNFα stimulated primary endometrial stromal cells to express cytokines that attracted monocytes and induced their differentiation into DCs. These monocyte-derived DCs stimulated endometrial epithelial cells to express the adhesive molecule SPP1 (osteopontin (OPN)) and its receptors ITGB3 and CD44, whereas MUC16, which interferes with adhesion, was downregulated. Other implantation-associated genes, such as CHST2, CCL4 (MIP1B) and GROA, were upregulated by monocyte-derived Mac. These findings suggest that uterine receptivity is mediated by the expression of molecules associated with inflammation. Such an inflammatory milieu is not generated in some IVF patients with recurrent implantation failure in the absence of local injury provoked by the biopsy treatment.

Trophoblast induces monocyte differentiation into CD14+/CD16+ macrophages

PROBLEM

During early pregnancy, macrophages and trophoblast come into close contact during placenta development, and regulated cross talk between these cellular compartments is crucial for maintaining a healthy pregnancy. As trophoblast cells constitutively secrete many chemokines and cytokines, we hypothesize that trophoblast-secreted factors can differentiate monocytes into a decidual phenotype. In this study, we describe a unique macrophage phenotype, following monocytes' exposure to trophoblast-soluble factors.

METHOD OF STUDY

Peripheral blood monocytes were treated with or without conditioned media (CM) from first trimester trophoblast cells. Phenotypic changes and phagocytic capacity were determined by flow cytometry. Cytokine and chemokine production was determined by multiplex analysis.

RESULTS

Monocytes exposed to trophoblast factors undergo morphologic changes characterized by a gain in size and complexity and acquire a unique phenotype characterized by gain of CD14 surface expression as well as CD16. The presence of CD14+/CD16+ macrophages was confirmed in normal decidua. These cells secrete higher levels of IL-1b, IL-10, and IP-10 and have increased capacity for phagocytosis.

CONCLUSION

We demonstrate that trophoblast-secreted factors can induce monocyte differentiation into a unique macrophage phenotype. These findings suggest that the microenvironment of the placenta can modulate the phenotype of macrophages present at the decidua.

Potential Pathophysiological Mechanisms of the Beneficial Role of Endometrial Injury in In Vitro Fertilization Outcome

Successful embryo implantation is a complex process that involves multiple biological mechanisms and reciprocal interactions between the embryo and the proliferated endometrium. In this review, we provide an informative contribution on the pathways underlying the beneficial nature of endometrial injury toward improving implantation rates of embryos conceived and through in vitro fertilization. The evidence published to date are in favor of inducing local endometrial injury in the preceding cycle of ovarian stimulation to improve pregnancy outcomes in women with unexplained and recurrent implantation failure. Endometrial injury triggers a series of biological responses but the findings suggest that no particular pathway is solely adequate to explain the association between trauma and improved pregnancy rates rather than a cluster of events in response to trauma which benefits embryo implantation in ways both known and unknown to the scientific community.

IFPA Senior Award Lecture: Reproductive immunology in perspective--reprogramming at the maternal-fetal interface

Involvement of the maternal and fetal immune systems in the events of pregnancy was generally overlooked by reproductive biologists until the mid-twentieth century when many landmark explorations were reported. Now, more than half a century later, it is well understood that with the initiation of pregnancy, immune cells in mammalian uteri are reprogrammed, losing their cytotoxic potential and providing an immunosuppressive environment suitable for harboring the genetically different fetus. We propose that it is the placenta that is mainly responsible for this conversion and maintenance throughout pregnancy. Studies in our laboratory indicate that trophoblast-derived soluble HLA-G has a subtle but well defined role in programming uterine placental macrophages, a potentially destructive immune cell population. Thus, placental HLA-G plays a critical role in assuring that the developing fetus emerges unscathed at parturition.

Endometrial inflammation and effect on implantation improvement and pregnancy outcome

Implantation failure, which is presently the major barrier in human fertility, is attributed, in many cases, to the failure of the uterus to acquire receptivity. The transition into a receptive uterus includes cellular changes in the endometrium and the modulated expression of different cytokines, growth factors, transcription factors, and prostaglandins. These molecules partake in the generation of an inflammatory response followed by the recruitment of immune cells. These cells have shown to be involved in the maternal immune tolerance toward the implanted embryo as well as in the maternal–fetus interaction during pregnancy. Most of the accumulated evidence indicates that embryo implantation is associated with an active Th1 inflammatory response while a Th2-humoral inflammation is required for pregnancy maintenance. Yet, recent findings suggest that a Th1 inflammatory response is also necessary for the acquisition of uterine receptivity. This notion was originally suggested by reports from our and other clinical centers worldwide that IVF patients with repeated implantation failure subjected to endometrial biopsy exhibit a substantial improvement in their chances to conceive. These findings, followed by the demonstration of an elevated pro-inflammatory cytokine/chemokine expression, as well as an increased abundance of immune cells, in the endometrium of these patients, raised the idea that acquisition of uterine receptivity is closely associated with an inflammatory response. This review summarizes the molecular and biochemical evidence that confirm this notion and proposes a mechanism by which injury-induced inflammation improves uterine receptivity and the subsequent pregnancy outcome.

[Immunological aspect of pregnancy]

Pregnancy is a temporary semi-allograft that survives for nine months. The importance of this event for the survival of the species justifies several tolerance mechanisms that are put into place at the beginning of pregnancy, some of which occur even at the time of implantation. The presence of multiple tolerance mechanisms and the richness of the means employed underline the central importance of the trophoblast. Understanding these mechanisms, and in particular, their integration into an overall scheme, enables the anomalies encountered in certain pathologies of pregnancy to be placed into context. Understanding these mechanisms and their interruption at the end of pregnancy should improve our understanding of disappointing results from current immunological treatments facilitate the implementation of new prophylactic and therapeutic strategies.

Inflammation: a link between endometriosis and preterm birth

Endometriosis is a chronic inflammatory disease affecting women's health. Pain and infertility are the major symptoms caused by a hormonal/immunological dysfunction, which causes an endometrial impairment. The same pathogenetic mechanisms are also associated with preterm birth: hormones, cytokines, neurohormones, and growth factors interact in modulating extracellular matrix and prostaglandin secretion, thus activating the inflammatory process in placental membranes and myometrium. An overlap of molecules and mechanisms may explain the evidence that preterm birth is a common outcome in pregnant patients with endometriosis.

Methylome of fetal and maternal monocytes and macrophages at the feto-maternal interface

PROBLEM

Decidual macrophages (dMφ) of the mother and placental macrophages (Hofbauer cells, HC) of the fetus are deployed at a critical location: the feto-maternal interface. This study was conducted to compare the DNA methylome of maternal and fetal monocytes, dMφ, and HC and thereby to determine the immunobiological importance of DNA methylation in pregnancy.

METHOD OF STUDY

Paired samples were obtained from normal pregnant women at term not in labor and their neonates. Maternal monocytes (MMo) and fetal monocytes (FMo) were isolated from the peripheral blood of mothers and fetal cord blood, respectively. dMφ and HC were obtained from the decidua of fetal membranes and placentas, respectively. DNA methylation profiling was performed using the Illumina Infinium Human Methylation27 BeadChip. Quantitative real-time PCR and Western Blot were performed for validation experiments.

RESULTS

(i) Significant differences in DNA methylation were found in each comparison (MMo versus FMo, 65 loci; dMφ versus HC, 266 loci; MMo versus dMφ, 199 loci; FMo versus HC, 1030 loci). (ii) Many of the immune response-related genes were hypermethylated in fetal cells (FMo and HC) compared to maternal cells (MMo and dMφ). (iii) Genes encoding markers of classical macrophage activation were hypermethylated, and genes encoding alternative macrophage activation were hypomethylated in dMφ and HC compared to MMo and FMo, respectively. (iv) mRNA expressions of DNMT1, DNMT3A, and DNMT3B were significantly lower in dMφ than in HC. (v) 5-azacytidine treatment increased expression of INCA1 in dMφ.

CONCLUSIONS

The findings herein indicate that DNA methylation patterns change during monocyte-macrophage differentiation at the feto-maternal interface. It is also suggested that DNA methylation is an important component of the biological machinery conferring an anti-inflammatory phenotype to macrophages at the feto-maternal interface.

Selective inhibition and augmentation of alternative macrophage activation by progesterone

Progesterone is the female sex hormone necessary for the maintenance of pregnancy, and is known to modulate macrophage activation. However, studies have concentrated exclusively on the ability of progesterone to negatively regulate the innate and classical pathways of activation, associated with nitric oxide (NO) and interleukin (IL)-12 production. Our aim was to examine the ability of progesterone to modulate alternative macrophage activation. Bone marrow cells were isolated and differentiated from male BALB/c mice, exposed to varying concentrations of progesterone and stimulated with lipopolysaccharide (LPS) (innate activation), IL-4 (alternative activation) or LPS in combination with IL-4. Our present study demonstrates that progesterone not only down-regulates inducible nitric oxide synthase 2 (iNOS) activity in macrophages but also arginase activity, in a dose-dependent manner, independent of the stimuli, whether it is induced by LPS (innate activation), IL-4 (alternative activation) or LPS in combination with IL-4. The ability of progesterone to down-modulate IL-4-induced cell surface expression of the mannose receptor further suggested a negative regulation of alternative macrophage activation by this hormone. Analysis of mRNA expression, by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), of genes associated with innate and alternative macrophage activation revealed that progesterone down-regulated LPS-induced macrophage nos2, argI and p40 (IL-12/IL-23) expression and IL-4-induced argI, mrc-1 and fizz1 expression. However, progesterone up-regulated IL-4-induced macrophage expression of ym1, while dectin-1 expression remained unaltered. Following treatment of macrophages with LPS and IL-4 in combination a similar pattern was observed, with the exception that progesterone up-regulated macrophage expression of fizz1 as well as ym1 and did not modify mrc-1 expression. Our data demonstrate for the first time that a hormone has the ability to regulate selectively the expression of different genes associated with alternative macrophage activation.

Placental immunology and maternal alloimmune responses

During pregnancy, women are tolerant of their semi-allogeneic fetus whilst not being immunosuppressed and indeed readily form alloantibodies. This 'Immunological Paradox of Pregnancy' may be explained by an understanding of placental anatomy and immunology. Trophoblast cells form the interface between the fetus and maternal tissues and blood and escape allorecognition because they lack classical human leucocyte antigen (HLA) class I and II molecules. Local immunoregulation, or tolerance, in the decidua is mediated partly by HLA-G(+) extravillous trophoblasts (EVT) that invade the tissue and prevent killing by maternal natural killer cells, cytotoxic T cells and macrophages. Placental hormones orchestrate the composition and regulatory function of maternal immune cells. In contrast, syncytiotrophoblast cells at the surface of chorionic villi, in contact with maternal blood, maintain a state of mild maternal systemic immunity via activation of innate immunity and skewing towards humoral immunity. This enables maintenance of a healthy immune system in pregnant women and robust protective antibody responses to pathogens whilst enabling survival of the fetus. However, this has the unfortunate consequence that pregnant women readily form alloantibodies to incompatible alloantigens on fetal red cells, platelets and leucocytes if fetomaternal haemorrhage (FMH) occurs. The antibodies are initially low affinity but after re-immunization with further FMH become functionally effective, high-titre IgG.

Molecular phenotype of monocytes at the maternal-fetal interface

OBJECTIVE

The purpose of this study was to gain insight into the pathways that are associated with inflammation at the maternal-fetal interface. This study examined the molecular characteristics of monocytes that were derived from the maternal circulation and the placenta of obese women.

STUDY DESIGN

Mononuclear cells were isolated from placenta, venous maternal, and umbilical cord blood at term delivery; activated monocytes were separated with CD14 immunoselection. The genotype and expression pattern of the monocytes were analyzed by microarray and real-time reverse transcriptase-polymerase chain reaction.

RESULTS

The transcriptome of the maternal blood and placental CD14 monocytes exhibited 73% homology, with 10% (1800 common genes) differentially expressed. Genes for immune sensing and regulation, matrix remodeling, and lipid metabolism were enhanced 2-2006 fold in placenta, compared with maternal monocytes. The CD14 placental monocytes exhibited a maternal genotype (9% DYS14 expression) as opposed to the fetal genotype (90% DYS14 expression) of the trophoblast cells.

CONCLUSION

CD14 monocytes from the maternal blood and the placenta share strong phenotypic and genotypic similarities with an enhanced inflammatory pattern in the placenta. The functional traits of the CD14 blood and placental monocytes suggest that they both contribute to propagation of inflammation at the maternal-fetal interface.

Relaxin modulates proinflammatory cytokine secretion from human decidual macrophages

Relaxin (RLN) is a systemic hormone from the corpus luteum, and its levels remain low during normal human gestation. Indeed, elevation of circulating RLN has long been associated with preterm birth, for which there has been no physiological explanation. Recent studies have shown that RLN suppresses endotoxin-induced cytokine secretion from THP-1 monocytic cells by acting on the glucocorticoid receptor (GR), but its effects on primary macrophages are unknown. Therefore, in the present study, we examined the effects of RLN on cytokine secretion from primary decidual macrophages (DMs) obtained at term before labor. Unlike THP-1 cells, RLN had no effects on the cytokine responses induced by either lipopolysaccharide (LPS) or interleukin (IL) 1B, mimicking infection-induced or sterile inflammation, respectively. However, RLN alone for 4 h significantly decreased (P < 0.05) colony-stimulating factor 2 (CSF2; also known as granulocyte-macrophage colony-stimulating factor) and IL8 but for 24 h significantly increased IL6 (P < 0.01). We show that DMs express both the RLN receptor (RXFP1) and the GR. RLN suppression of CSF2 and IL8 was sensitive to the GR-antagonist mifepristone (RU-486). However, RLN activation of RXFP1 induced a dose-dependent cAMP response, which when mimicked by forskolin also caused significantly increased (P < 0.05) secretion of IL6. Thus, RLN may be anti-inflammatory in DMs via activation of the GR but proinflammatory via activation of RXFP1 and cAMP. In summary, we have shown that RLN targeting DMs may modulate proinflammatory cytokine secretion at the maternal-fetal interface and contribute to the localized inflammatory response associated with parturition in women.

Human trophoblast-derived exosomal fibronectin induces pro-inflammatory IL-1β production by macrophages

PROBLEM  Our previous studies demonstrated that trophoblast-derived exosomes induced synthesis and release of pro-inflammatory cytokines, including interleukin-1β (IL-1β) by macrophages. The objective of this study was to characterize the mechanism and receptors associated with this induction. METHOD OF STUDY  Exosomes were isolated from Sw71 trophoblast-conditioned media by ultrafiltration and ultracentrifugation. Using macrophages isolated from normal donors, cytochalasin D was used to block exosome uptake. Induction of IL-1β mRNA was investigated by qRT-PCR, pro-IL-1β protein by western immunoblotting, and mature IL-1β release by ELISA. RGD peptides were used to block fibronectin binding by macrophage α5β1 integrin. RESULTS  Uptake of exosomes by macrophages was completely blocked by pre-treatment with cytochalasin D. Although induction of some cytokines (such as C4A and CCL11) requires uptake, induction of IL-1β occurred without exosome internalization. Cytochalasin D treatment did not inhibit exosome-mediated induction of IL-1β mRNA, production of the pro-protein, or release of mature IL-1β. Blocking of fibronectin binding using RGD peptides demonstrated the abrogation of exosome-mediated IL-1β production. CONCLUSION  Although trophoblast-derived exosomes have been demonstrated to induce IL-1β, this is the first demonstration of IL-1β induction by exosome-associated fibronectin. Based on this pro-inflammatory role of exosome-associated fibronectin, it may represent an important general immunoregulatory mechanism.

Trophoblast-derived exosomes mediate monocyte recruitment and differentiation

INTRODUCTION

trophoblast cells have been demonstrated to regulate monocyte migration and differentiation, leading to pro-inflammatory profiles. Because trophoblast cells release exosomes with immunoregulatory properties, trophoblast-derived exosomes are proposed to 'educate' monocytes, creating a pro-inflammatory environment.

METHOD OF STUDY

exosomes were isolated from conditioned media of Swan71 cells by ultrafiltration and ultracentrifugation. Exosome-induced migration was assessed using a two-chamber system. Cytokine profiles were defined using cytokine arrays, and mRNA levels of affected cytokines were examined by qRT-PCR and ELISA.

RESULTS

within 20 min, 8-10% of monocytes took up labeled exosomes isolated from Swan71 cells. Trophoblast-derived exosomes increased monocyte migration in a dose-dependent manner and produced significant increases in production of interleukin (IL)-1β, IL-6, Serpin-E1, granulocyte colony-stimulating factor, granulocyte/monocyte colony-stimulating factor, and tumor necrosis factor-α.

CONCLUSION

this study presents the initial demonstration that trophoblast-derived exosomes are capable of recruiting and 'educating' monocytes to produce pro-inflammatory cytokine/chemokine profiles in a cell-contact-independent manner.

The hygiene hypothesis revisited: role of materno-fetal interactions

For 20 years, the hygiene hypothesis has dominated attempts to explain the increasing prevalence of allergic disease. A causal link between maternal innate immune response during pregnancy and disease protection in the offspring was recently demonstrated. Central to this was a systemically diffused signal that downregulated Toll-like receptor expression in placental tissues. Herein we develop the hypothesis that maternal systemic regulatory mechanisms operational during pregnancy could impact allergic disease risk of the offspring, depending on the type of inflammatory response from which they originate. Classic microbial-derived, mild, subacute inflammation provides a protective signal, whereas allergic inflammation provides a negative one. Mild, subacute inflammation of pregnant women leads to systemically diffused signals manifest in the gestation-associated tissues and by the fetus and newborn as a dampened inflammatory response. The converse is true if the mother has allergic inflammation during pregnancy. In both cases, these impact on development of the airways and of balanced immune function at birth and in early postnatal life. Thus, we seem to be at the dawn of a new incarnation of the hygiene hypothesis in which the pregnant woman's inflammatory response is crucial to determining the child's likelihood of developing allergic disease.

Vascular-leukocyte interactions: mechanisms of human decidual spiral artery remodeling in vitro

Transformation of uterine spiral arteries is critical for healthy human pregnancy. We recently proposed a role for maternal leukocytes in decidual spiral artery remodeling and suggested that matrix metalloprotease (MMP) activity contributed to the destruction of the arterial wall. In the current study we used our first trimester placental-decidual co-culture (PDC) model to define the temporal relationship and test the mechanistic aspects of this process. PDC experiments were assessed by image analysis over a six-day time-course for degree of vascular transformation and leukocyte distribution around progressively remodeled arterioles. We observed rapid transformation in PDCs associated with loss of vascular smooth muscle cells, widening of the vessel lumen, and significant accumulation of uterine Natural Killer cells and macrophages within the vascular wall (P < 0.001) before trophoblast presence in the vessel lumens. These events did not occur in decidua-only cultures. Active MMP-9 was detected in leukocytes and vascular cells of remodeling arterioles, and inhibition of MMP-2/9 activity in PDC resulted in failure of decidual vascular remodeling compared with vehicle-treated PDCs. Apoptosis of vascular cells, macrophage-mediated phagocytosis, and vascular smooth muscle cell dedifferentiation contributed to the remodeling observed. The PDC model indicates that placental presence is required to initiate decidual spiral artery remodeling but that uterine Natural Killer cells and macrophages mediate the early stages of this process at the cellular level.

Local injury of the endometrium induces an inflammatory response that promotes successful implantation

OBJECTIVE

To study whether an injury-induced inflammation might be the mechanism underlying the favorable effect of endometrial biopsy on the implantation rate in in vitro fertilization (IVF) patients.

DESIGN

Controlled clinical study.

SETTING

A medical center IVF unit and a research institute.

PATIENT(S)

Women undergoing IVF who had previous failed treatment cycles.

INTERVENTION(S)

Endometrial samples were collected from two groups of patients on day 21 of their spontaneous menstrual cycle. The experimental, but not the control group underwent prior biopsy treatment on days 8 or/and 11 to 13 of that same cycle.

MAIN OUTCOME MEASURE(S)

Abundance of immune cells, cytokines/chemokines level, correlation between these parameters and pregnancy outcome.

RESULT(S)

A statistically significantly higher amount of macrophages/dendritic cells (HLA-DR+ CD11c+ cells) and elevated proinflammatory cytokines, tumor necrosis factor-α (TNF-α), growth-regulated oncogene-α (GRO-α), interleukin-15 (IL-15), and macrophage inflammatory protein 1B (MIP-1B), were detected in day-21 endometrial samples of the experimental group. A direct stimulatory effect of TNF-α on MIP-1B, GRO-α, and IL-15 messenger RNA (mRNA) expression was demonstrated. A positive correlation was found between the levels of macrophages/dendritic cells, MIP-1B expression, and TNF-α expression and the pregnancy outcome.

CONCLUSION(S)

A biopsy-induced inflammatory response may facilitate the preparation of the endometrium for implantation. Increased MIP-1B expression could possibly serve for prediction of implantation competence.

The immunomodulatory roles of macrophages at the maternal-fetal interface

Macrophages are versatile cells that play a central role in innate and adaptive immunity and participate in a wide variety of biological processes. In the uterine decidua, macrophages represent a major leukocyte subset throughout pregnancy. Here, decidual macrophages exert an immunosuppressive phenotype characterized by abundant production of interleukin (IL)-10 and indoleamine 2,3-dioxygenase activity. Their polarized cytokine secretion pattern has recently been classified as an M2 phenotype. These features of decidual macrophages favor maternal immune tolerance to semiallogenic fetus. In addition, macrophages cooperate with trophoblast cells during the early stages of human pregnancy to support uterine vasculature remodeling by removing apoptotic cells and through the production of proteases that degrade the extracellular matrix. In the peripartum period, macrophages also participate in the regulation of cervical ripening and the initiation of parturition through the production of proinflammatory cytokines and prostaglandin E(2) (PGE(2)). Aberrant activity of uterine macrophages is linked to the pathogenesis of preeclampsia and preterm delivery. Here, we review the immunomodulatory roles of decidual macrophages during pregnancy.

Inflammation in reproductive disorders

Inflammatory disorders account for a significant percentage of gynecologic disease, particularly in reproductive age women. Inflammation is a basic method by which we respond to infection, irritation, or injury. Inflammation is now recognized as a type of nonspecific immune response, either acute or chronic. In gynecology, inflammation leads to anatomic disorders primarily as a result of infectious disease; however inflammation can affect ovulation and hormone production as well as be associated with endometriosis. Similarly, immune cell trafficking is an important component of cyclic endometrial development in each menstrual cycle. These immune cells are required for endometrial function, producing a vast array of inflammatory cytokines. Inflammation alters endometrial receptivity, however it may also play a role in tissue repair and remodeling. Finally, inflammation affects the trophoblast and trophoblast-endometrial interaction. Some components of the immune response are required for optimal fertility and normal tissue remodeling. A better understanding of the necessary role of inflammation in reproduction will allow more rational and targeted treatment of inflammatory disorders in reproductive medicine.