Decidual natural killer cell receptor expression is altered in pregnancies with impaired vascular remodeling and a higher risk of pre-eclampsia

Maternal-Fetal Compatibility in Recurrent Pregnancy Loss

Nowadays, recurrent pregnancy loss (RPL) is an undesirable condition suffered by many patients of reproductive age. In this scenario, certain immune cell populations and molecules, involved in maternal-fetal compatibility, have emerged as factors related with the pathogenesis of RPL. Among them, uterine Natural Killer cells (uNKs) appear to be of great relevance. These cells are involved in numerous processes during pregnancy, such as the remodeling of uterine spiral arteries or the control of trophoblast invasion. These functions are regulated by the interactions that these cells establish with the extravillous trophoblast, mainly through their Killer Immunoglobulin-like Receptors (KIRs) and the Human Leukocyte Antigen-C (HLA-C) molecules expressed by the embryo. A high level of polymorphism has been reported for both molecules involved in this interaction, with some of the possible KIR-HLA-C combinations being associated with an increased risk of RPL. However, the complexity of the maternal-fetal interface goes beyond this, as other HLA molecules also appear to be related to this reproductive pathology. In this review, we will discuss the role of uNKs in pregnancy, as well as the polymorphisms and clinical implications of KIR-HLA-C binding. We will also address the involvement of other, different HLA molecules in RPL, and the current advice on the appropriate management of patients with 'immunological mismatch', thus covering the main aspects regarding the involvement of maternal-fetal compatibility in RPL.

NK cell receptor profiling of endometrial and decidual NK cells reveals pregnancy-induced adaptations

Natural killer (NK) cells, with a unique NK cell receptor phenotype, are abundantly present in the non-pregnant (endometrium) and pregnant (decidua) humanuterine mucosa. It is hypothesized that NK cells in the endometrium are precursors for decidual NK cells present during pregnancy. Microenvironmental changes can alter the phenotype of NK cells, but it is unclear whether decidual NK cell precursors in the endometrium alter their NK cell receptor repertoire under the influence of pregnancy. To examine whether decidual NK cell precursors reveal phenotypic modifications upon pregnancy, we immunophenotyped the NK cell receptor repertoire of both endometrial and early-pregnancy decidual NK cells using flow cytometry. We showed that NK cells in pre-pregnancy endometrium have a different phenotypic composition compared to NK cells in early-pregnancy decidua. The frequency of killer-immunoglobulin-like receptor (KIR expressing NK cells, especially KIR2DS1, KIR2DL2L3S2, and KIR2DL2S2 was significantly lower in decidua, while the frequency of NK cells expressing activating receptors NKG2D, NKp30, NKp46, and CD244 was significantly higher compared to endometrium. Furthermore, co-expression patterns showed a lower frequency of NK cells co-expressing KIR3DL1S1 and KIR2DL2L3S2 in decidua. Our results provide new insights into the adaptations in NK cell receptor repertoire composition that NK cells in the uterine mucosa undergo upon pregnancy.

The normality of the first-trimester placentae collected from elective terminations

Placentae collected from elective terminations during the first trimester are commonly used as control samples in research. However, it is widely acknowledged that many complications of pregnancies can occur or originate during the early stage of gestation. This raises the question that the placentae collected from the first trimester may not accurately reflect normal placental conditions. In this study, 95 placentae were collected from elective terminations and histology was performed. Out of these, 53 placentae (56 %) exhibited the typical structure of placental villi, indicating normal development. However, 42 placentae (44 %) showed placental hydrops, with varying degrees of severity (mild, moderate, or severe). Placental hydrops has been linked to several complicated pregnancies in the later stages of gestation. Our findings suggest that the development of pregnancy pathologies could start in the first trimester, as observed by the presence of hydrops. Placental researchers should be aware of when using first-trimester placentae from termination as controls in studies. However, it remains unclear whether pathological morphologies resolve or ameliorate as the pregnancy progression or whether such placentae continue to have such pathology, but clinical symptoms/signs do not manifest.

The novel role of activating receptor KIR2DS5 in preeclampsia

Preeclampsia (PE) is a serious complication of pregnancy. Decidual natural killer (dNK) cells were reported to participate in the remodeling of spiral arteries through producing a group of cytokines, including granulocyte-macrophage colony stimulating factor (GM-CSF). KIR2DS5 is an activating receptor of NK cells that specifically recognizes HLA-C2 on trophoblasts. Currently, there are no reports regarding the precise mechanism of KIR2DS5 in PE. This study included 30 PE patients and 30 healthy pregnant women. We found that the expressions of KIR2DS5 were significantly lower in PE deciduae compared to those of healthy pregnancies. By transfecting knockdown and overexpression lentivirus vectors of KIR2DS5 into dNK cells isolated from deciduae of early pregnancy, we altered the KIR2DS5 expression level in dNK cells. Then, these dNK cells and trophoblast cell lines were co-cultured as trophoblast-dNK cells. In the trophoblast-dNK cells, we examined the influence of KIR2DS5 on the biological manifestations of trophoblasts. As anticipated, overexpression of KIR2DS5 could facilitate cell proliferation, migration, and invasion. Furthermore, increased expression of KIR2DS5 inhibited cell apoptosis and enhanced the progression of cells from theG1 to theS stage. Further mechanistic study demonstrated a positive relationship between KIR2DS5 and GM-CSF in trophoblast-dNK cells. Accordingly, our observations indicated that a decrease in KIR2DS5 could reduce the expression of GM-CSF via the JAK2/STAT5 pathway, resulting in the failure of the activated signal to be transmitted to dNK cells and ultimately leading to the occurrence of PE. KIR2DS5 may be a new contributor for the prediction and diagnosis of PE.

Innate and Adaptive Immune Systems in Physiological and Pathological Pregnancy

The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.

Uterine NK cells underexpress KIR2DL1/S1 and LILRB1 in reproductive failure

A significant proportion of recurrent miscarriage, recurrent implantation failure and infertility are unexplained, and these conditions have been proposed to have an etiology of immunological dysfunction at the maternal-fetal interface. Uterine Natural Killer cells (uNK) comprise three subsets and are the most numerous immune cells found in the uterine mucosa at the time of implantation. They are thought to play an important role in successful pregnancy by regulation of extravillous trophoblast (EVT) invasion and spiral artery remodelling. Here, we examine the frequency, phenotype and function of uNK1-3 from the uterine mucosa of 16 women with unexplained reproductive failure compared to 11 controls with no reproductive problems, during the window of implantation. We report that KIR2DL1/S1 and LILRB1 expression is lower in the reproductive failure group for both uNK (total uNK, uNK 2 and 3) and pNK. We also show that degranulation activity is significantly reduced in total uNK, and that TNF-α production is lower in all uNK subsets in the reproductive failure group. Taken together, our findings suggest that reproductive failure is associated with global reduction in expression of uNK receptors important for interaction with HLA-C and HLA-G on EVT during early pregnancy, leading to reduced uNK activation. This is the first study to examine uNK subsets during the window of implantation in women with reproductive failure and will serve as a platform to focus on particular aspects of phenotype and function of uNK subsets in future studies. Further understanding of uNK dysregulation is important to establish potential diagnostic and therapeutic targets in the population of women with unexplained reproductive failure.

Phenotypic and functional alteration of CD45+ immune cells in the decidua of preeclampsia patients analyzed by mass cytometry (CyTOF)

Preeclampsia (PE) is a severe placenta-related pregnancy disease that has been associated with maternal systemic inflammation and immune system disorders. However, the distribution and functional changes in immune cells of the maternal-placental interface have not been well characterized. Herein, cytometry by time-of-flight mass spectrometry (CyTOF) was used to investigate the immune atlas at the decidua, which was obtained from four PE patients and four healthy controls. Six superclusters were identified, namely, T cells, B cells, natural killer (NK) cells, monocytes, granulocytes, and others. B cells were significantly decreased in the PE group, among which the reduction in CD27+CD38+ regulatory B cell (Breg)-like cells may stimulate immune activation in PE. The significantly increased migration of B cells could be linked to the significantly overexpressed chemokine C-X-C receptor 5 (CXCR5) in the PE group, which may result in the production of excessive autoantibodies and the pathogenesis of PE. A subset of T cells, CD11c+CD8+ T cells, was significantly decreased in PE and might lead to sustained immune activation in PE patients. NK cells were ultimately separated into four subsets. The significant reduction in a novel subset of NK cells (CD56-CD49a-CD38+) in PE might have led to the failure to suppress inflammation at the maternal-fetal interface during PE progression. Moreover, the expression levels of functional markers were significantly altered in the PE group, which also inferred that shifts in the decidual immune state contributed to the development of PE and might serve as potential treatment targets. This is a worthy attempt to elaborate the differences in the phenotype and function of CD45+ immune cells in the decidua between PE and healthy pregnancies by CyTOF, which contributes to understand the pathogenesis of PE, and the altered cell subsets and markers may inspire the immune modulatory therapy for PE.

The central role of natural killer cells in preeclampsia

Preeclampsia (PE) is a disease that is unique to pregnancy and affects multiple systems. It can lead to maternal and perinatal mortality. The precise etiology of PE is unclear. Patients with PE may have systemic or local immune abnormalities. A group of researchers has proposed that the immune communication between the fetus and mother is primarily moderated by natural killer (NK) cells as opposed to T cells, since NK cells are the most abundant immune cells in the uterus. This review examines the immunological roles of NK cells in the pathogenesis of PE. Our aim is to provide obstetricians with a comprehensive and updated research progress report on NK cells in PE patients. It has been reported that decidual NK (dNK) cells contribute to the process of uterine spiral artery remodeling and can modulate trophoblast invasion. Additionally, dNK cells can stimulate fetal growth and regulate delivery. It appears that the count or proportion of circulating NK cells is elevated in patients with or at risk for PE. Changes in the number or function of dNK cells may be the cause of PE. The Th1/Th2 equilibrium in PE has gradually shifted to an NK1/NK2 equilibrium based on cytokine production. An improper combination of killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA)-C may lead to insufficient activation of dNK cells, thereby causing PE. In the etiology of PE, NK cells appear to exert a central effect in both peripheral blood and the maternal-fetal interface. To maintain immune equilibrium both locally and systemically, it is necessary to take therapeutic measures directed at NK cells.

Uterine Natural Killer Cells: A Rising Star in Human Pregnancy Regulation

Uterine natural killer (uNK) cells are an immune subset located in the uterus. uNK cells have distinct tissue-specific characteristics compared to their counterparts in peripheral blood and lymphoid organs. Based on their location and the pregnancy status of the host, uNK cells are classified as endometrial NK (eNK) cells or decidua NK (dNK) cells. uNK cells are important in protecting the host from pathogen invasion and contribute to a series of physiological processes that affect successful pregnancy, including uterine spiral artery remodeling, fetal development, and immunity tolerance. Abnormal alterations in uNK cell numbers and/or impaired function may cause pregnancy complications, such as recurrent miscarriage, preeclampsia, or even infertility. In this review, we introduce recent advances in human uNK cell research under normal physiological or pathological conditions, and summarize their unique influences on the process of pregnancy complications or uterine diseases. Finally, we propose the potential clinical use of uNK cells as a novel cellular immunotherapeutic approach for reproductive disorders.

CD158a+ /CD158b+ NK cell imbalance correlates with hypertension in patients with pre-eclampsia

PROBLEM

Preeclampsia, a pregnancy complication with hypertension and proteinuria, seriously threats the health and lives of the mother and the baby. The pathogenesis of pre-eclampsia remains incompletely understood. The role of peripheral natural killer cells (NK cells) in the pre-eclampsia is unclear.

METHOD OF STUDY

Flow cytometry was performed to detect the expression of CD158a (KIR2DL1) and CD158b (KIR2DL2/3) in peripheral NK cells of healthy pregnant women (HP) and patients with pre-eclampsia (PE). Differentially expressed genes (DEGs) in CD158a⁺ and CD158b⁺ NK cells were identified by RNA-sequencing and real-time PCR. Protein array analysis was used to identify altered protein levels in the serum of study participants.

RESULTS

CD158a⁺ NK cell numbers were increased in the peripheral blood of patients while the number of CD158b⁺ NK cells was reduced. In addition, the percentage of CD158a⁺ NK cells within the peripheral NK subset was positively correlated with systolic blood pressure while the percentage of CD158b⁺ NK cells was negatively correlated with systolic blood pressure. RNA-seq and real-time PCR showed that the expression of ERAP2 and GCH1, the genes that regulate blood pressure and angiogenesis, was decreased in CD158a⁺ compared to CD158b⁺ NK cells. Consistently, the level of proteins involved in angiogenesis was altered in the serum of pre-eclampsia patients compared to healthy individuals.

CONCLUSIONS

CD158a⁺ NK cells increased while CD158b⁺ NK cells decreased in the peripheral blood of patients with pre-eclampsia compared to healthy individuals. The change in the frequency of CD158a⁺ /CD158b⁺ NK cells is related to the increase in blood pressure.

Uterine Natural Killer Cells and Implantation

Decidual leukocytes make up approximately 30% of all decidual stromal cells in early pregnancy, of which 70% are uterine natural killer (uNK) cells. uNK cells are phenotypically distinct from peripheral blood NK cells, being CD56[Formula: see text]CD16[Formula: see text]. A recent single-cell sequencing project of the decidua identified three subsets of uNK cells, but we are yet to determine how they differ functionally. Several roles for uNK cells in implantation are starting to emerge including biosensing of poor-quality embryos, killing of bacteria infected trophoblast, spiral artery remodeling, and regulation of trophoblast invasion. Altered numbers of uNK cells have been identified in several pathological conditions, but whether this is causative of the condition is currently unclear.

Role of Natural Killer Cells during Pregnancy and Related Complications

A high number of leucocytes reside in the human endometrium and are distributed differentially during the menstrual cycle and pregnancy. During early pregnancy, decidual natural killer (dNK) cells are the most common type of natural killer (NK) cells in the uterus. The increase in the number of uterine NK (uNK) cells during the mid-secretory phase of the menstrual cycle, followed by further increase of dNK cells in early pregnancy, has heightened interest in their involvement during pregnancy. Extensive research has revealed various roles of dNK cells during pregnancy including the formation of new blood vessels, migration of trophoblasts, and immunological tolerance. The present review article is focused on the significance of NK cells during pregnancy and their role in pregnancy-related diseases. The article will provide an in-depth review of cellular and molecular interactions during pregnancy and related disorders, with NK cells playing a pivotal role. Moreover, this study will help researchers to understand the physiology of normal pregnancy and related complications with respect to NK cells, so that future research work can be designed to alleviate the complications.

Cellular immune responses in the pathophysiology of preeclampsia

Preeclampsia, defined as new-onset hypertension accompanied by proteinuria occurring at 20 weeks of gestation or later, is a leading cause of perinatal morbidity and mortality worldwide. The pathophysiology of this major multi-systemic syndrome includes defective deep placentation, oxidative stress, endothelial dysfunction, the presence of an anti-angiogenic state, and intravascular inflammation, among others. In this review, we provide a comprehensive overview of the cellular immune responses involved in the pathogenesis of preeclampsia. Specifically, we summarize the role of innate and adaptive immune cells in the maternal circulation, reproductive tissues, and at the maternal-fetal interface of women affected by this pregnancy complication. The major cellular subsets involved in the pathogenesis of preeclampsia are regulatory T cells, effector T cells, NK cells, monocytes, macrophages, and neutrophils. We also summarize the literature on those immune cells that have been less characterized in this clinical condition, such as γδ T cells, invariant natural killer T cells, dendritic cells, mast cells, and B cells. Moreover, we discuss in vivo studies utilizing a variety of animal models of preeclampsia to further support the role of immune cells in this disease. Finally, we highlight the existing gaps in knowledge of the immunobiology of preeclampsia that require further investigation. The goal of this review is to promote translational research leading to clinically relevant strategies that can improve adverse perinatal outcomes resulting from the obstetrical syndrome of preeclampsia.

Killer Timing: The Temporal Uterine Natural Killer Cell Differentiation Pathway and Implications for Female Reproductive Health

Natural killer (NK) cells are the predominant maternal uterine immune cell component, and they densely populate uterine mucosa to promote key changes in the post-ovulatory endometrium and in early pregnancy. It is broadly accepted that (a) immature, inactive endometrial NK (eNK) cells in the pre-ovulatory endometrium become activated and transition into decidual NK (dNK) cells in the secretory stage, peri-implantation endometrium, and continue to mature into early pregnancy; and (b) that secretory-stage and early pregnancy dNK cells promote uterine vascular growth and mediate trophoblast invasion, but do not exert their killing function. However, this may be an overly simplistic view. Evidence of specific dNK functional killer roles, as well as opposing effects of dNK cells on the uterine vasculature before and after conception, indicates the presence of a transitory secretory-stage dNK cell (s-dNK) phenotype with a unique angiodevelopmental profile during the peri-implantation period, that is that is functionally distinct from the angiomodulatory dNK cells that promote vessel destabilisation and vascular cell apoptosis to facilitate uterine vascular changes in early pregnancy. It is possible that abnormal activation and differentiation into the proposed transitory s-dNK phenotype may have implications in uterine pathologies ranging from infertility to cancer, as well as downstream effects on dNK cell differentiation in early pregnancy. Further, dysregulated transition into the angiomodulatory dNK phenotype in early pregnancy will likely have potential repercussions for adverse pregnancy outcomes, since impaired dNK function is associated with several obstetric complications. A comprehensive understanding of the uterine NK cell temporal differentiation pathway may therefore have important translational potential due to likely NK phenotypic functional implications in a range of reproductive, obstetric, and gynaecological pathologies.

The Genomic Organization of the LILR Region Remained Largely Conserved Throughout Primate Evolution: Implications for Health And Disease

The genes of the leukocyte immunoglobulin-like receptor (LILR) family map to the leukocyte receptor complex (LRC) on chromosome 19, and consist of both activating and inhibiting entities. These receptors are often involved in regulating immune responses, and are considered to play a role in health and disease. The human LILR region and evolutionary equivalents in some rodent and bird species have been thoroughly characterized. In non-human primates, the LILR region is annotated, but a thorough comparison between humans and non-human primates has not yet been documented. Therefore, it was decided to undertake a comprehensive comparison of the human and non-human primate LILR region at the genomic level. During primate evolution the organization of the LILR region remained largely conserved. One major exception, however, is provided by the common marmoset, a New World monkey species, which seems to feature a substantial contraction of the number of LILR genes in both the centromeric and the telomeric region. Furthermore, genomic analysis revealed that the killer-cell immunoglobulin-like receptor gene KIR3DX1, which maps in the LILR region, features one copy in humans and great ape species. A second copy, which might have been introduced by a duplication event, was observed in the lesser apes, and in Old and New World monkey species. The highly conserved gene organization allowed us to standardize the LILR gene nomenclature for non-human primate species, and implies that most of the receptors encoded by these genes likely fulfill highly preserved functions.

Uterine natural killer cell biology and role in early pregnancy establishment and outcomes

Objective

While immune cells were originally thought to only play a role in maternal tolerance of the semiallogenic fetus, an active role in pregnancy establishment is becoming increasingly apparent. Uterine natural killer (uNK) cells are of specific interest because of their cyclic increase in number during the window of implantation. As a distinct entity from their peripheral blood counterparts, understanding the biology and function of uNK cells will provide the framework for understanding their role in early pregnancy establishment and adverse pregnancy outcomes.

Evidence Review

This review discusses unique uNK cell characteristics and presents clinical implications resulting from their dysfunction. We also systematically present existing knowledge about uNK cell function in three processes critical for successful human embryo implantation and placentation: stromal cell decidualization, spiral artery remodeling, and extravillous trophoblast invasion. Finally, we review the features of uNK cells that could help guide future investigations.

Results

It is clear the uNK cells are intimately involved in multiple facets of early pregnancy. This is accomplished directly, through the secretion of factors that regulate stromal cells and trophoblast function; and indirectly, via interaction with other maternal cell types present at the maternal-fetal interface. Current work also suggests that uNK cells are a heterogenous population, with subsets that potentially accomplish different functions.

Conclusion

Establishment of pregnancy through successful embryo implantation and placentation requires crosstalk between multiple maternal cell types and invading fetal trophoblast cells. Defects in this process have been associated with multiple adverse perinatal outcomes including hypertensive disorders of pregnancy, placenta accreta, and recurrent miscarriage though the mechanism underlying development of these defects remain unclear. Abnormalities in NK cell number and function which would disrupt physiological maternal-fetal crosstalk, could play a critical role in abnormal implantation and placentation. It is therefore imperative to dissect the unique physiological role of uNK cells in pregnancy and use this knowledge to inform clinical practice by determining how uNK cell dysfunction could lead to reproductive failure.

Killer-cell immunoglobulin-like receptor/human leukocyte antigen-C combination and 'great obstetrical syndromes' (Review)

Recurrent pregnancy loss (RPL), pre-eclampsia (PE), fetal growth restriction (FGR), and preterm delivery are examples of ‘great obstetrical syndromes’ (GOS). Placental dysfunction is the most common pathogenesis of GOS. In human pregnancies, the effects of uterine natural killer cells involve angiogenesis, promoting the remodeling of uterine spiral artery, and improving the invasion of trophoblast cells. The uNK cells supply killer immunoglobulin-like receptors (KIRs), which come into contact with human leukocyte antigen-C (HLA-C) ligands expressed by extravillous trophoblast cells (EVTs). Numerous studies have investigated the association between GOS and KIR/HLA-C combination. However, the outcomes have not been conclusive. The present review aimed to reveal the association between GOS and KIR/HLA-C combination to screen out high-risk pregnancies, strengthen the treatment of pregnancy complications, and reduce the frequency of adverse maternal and fetal outcomes. It has been reported that a female with a KIR AA genotype and a neonate with a paternal HLA-C2 molecule is more prone to develop GOS and have a small fetus since less cytokines were secreted by uNK cells. Conversely, the combination of KIR BB haplotype (including the activating KIR2DS1) and HLA-C2 can induce the production of cytokines and increase trophoblast invasion, leading to the birth of a large fetus. KIR/HLA-C combinations may be applicable in selecting third-party gametes or surrogates. Detection of maternal KIR genes and HLA-C molecules from the couple could serve as useful markers for predicting and diagnosing GOS.

Uterine natural killer cells: from foe to friend in reproduction

BACKGROUND

Recurrent miscarriage and pre-eclampsia are common reproductive disorders, but their causes are often unknown. Recent evidence has provided new insight into immune system influences in reproductive disorders. A subset of lymphocytes of the innate immune system known as uterine natural killer (uNK) cells are now recognized as fundamental to achieving embryo implantation and successful pregnancy, but were initially attributed a bad reputation. Indeed, immune therapies have been developed to treat the 'exaggerated' immune response from uNK cells. These treatments have been based on studies of peripheral blood natural killer (pbNK) cells. However, uNK cells and pbNK cells have different phenotypic and functional characteristics. The functions of uNK cells are closely related to their interactions with the extravillous trophoblast cells (EVTs) and spiral arteries, which underlie an essential role in regulating vascular function, controlling trophoblast invasion and promoting placental development. EVTs express MHC molecules of class I HLA-C/E/G/F, while uNK cells express, among other receptors, killer cell immunoglobulin-like receptors (KIRs) that bind to HLA-C or CD94/NKG2A inhibitory receptors, and then bind HLA-E. Associations of certain KIR/HLA-C combinations with recurrent miscarriage, pre-eclampsia, and foetal growth restriction and the interactions between uNK cells, trophoblasts and vascular cells have led to the hypothesis that uNK cells may play a role in embryo implantation.

OBJECTIVE AND RATIONALE

Our objective was to review the evolution of our understanding of uNK cells, their functions, and their increasingly relevant role in reproduction.

SEARCH METHODS

Relevant literature through June 2020 was retrieved using Google Scholar and PubMed. Search terms comprised uNK cells, human pregnancy, reproductive failure, maternal KIR and HLA-C, HLA-E/G/F in EVT cells, angiogenic cytokines, CD56+ NK cells, spiral artery, oestrogen and progesterone receptors, KIR haplotype and paternal HLA-C2.

OUTCOMES

This review provides key insights into the evolving conceptualization of uNK cells, from their not-so-promising beginnings to now, when they are considered allies in reproduction. We synthesized current knowledge about uNK cells, their involvement in reproduction and their main functions in placental vascular remodeling and trophoblast invasion. One of the issues that this review presents is the enormous complexity involved in studying the immune system in reproduction. The complexity in the immunology of the maternal-foetal interface lies in the great variety of participating molecules, the processes and interactions that occur at different levels (molecular, cellular, tissue, etc.) and the great diversity of genetic combinations that are translated into different types of responses.

WIDER IMPLICATIONS

Insights into uNK cells could offer an important breakthrough for ART outcomes, since each patient could be assessed based on the combination of HLA and its receptors in their uNK cells, evaluating the critical interactions at the materno-foetal interface. However, owing to the technical challenges in studying uNK cells in vivo, there is still much knowledge to gain, particularly regarding their exact origin and functions. New studies using novel molecular and genetic approaches can facilitate the identification of mechanisms by which uNK cells interact with other cells at the materno-foetal interface, perhaps translating this knowledge into clinical applicability.

Expression of leukocyte immunoglobulin-like receptor subfamily B expression on immune cells in hepatocellular carcinoma

BACKGROUND

Leukocyte immunoglobulin-like receptor subfamily B (LILRB) is a group of inhibitory receptors involved in innate immune mainly expressed on lymphoid and myelomonocytic cells. LILRB is proposed to serve as immune checkpoint like PD-1 and CTLA-4 for tumor treatment. We recently reported that the expression of LILRB2 in CD1c⁺ mDC from tumor tissue might suppress immune for HCC patients. However, the expression of all the LILRB family on other immune cells in peripheral blood and tumor microenvironment of HCC patients has not been systematically studied.

METHODS

The expression of LILRB family (LILRB1, LILRB2, LILRB3, LILRB4 and LILRB5) on immune cells, including granulocytes, NK cells, NKT cells, monocyte subsets, TAMs, B cells, γδ T cells, CD4⁺ T cells, CD8⁺ T cells and MDSC subsets, was analyzed by flow cytometry in the peripheral blood of 20 HCC patients and 20 healthy donors as well as in the tumor and tumor free tissues of 10 HCC patients.

RESULTS

LILRB1, LILRB2 and LILRB3 in granulocytes from peripheral blood were expressed increased in HCC patients compared with healthy donors. The expression of LILRB5 in NK cells and NKT cells from HCC blood were higher compared with healthy donors` blood. CD14⁺CD16⁺ monocyte subsets in blood of HCC patients expressed increased LILRB1 and LILRB4 than that in healthy donors. CD14⁺CD16^- monocyte subsets in blood of HCC patients expressed increased LILRB3 than that in healthy donors. Compared to corresponding TFL, LILRB3, LILRB4 and LILRB5 were expressed enhanced in TAMs from HCC tumors. LILRB1 expressed on the B cells both in the blood and tumor had significantly increased compared with healthy donors or corresponding TFL. Different from peripheral blood, in the HCC microenvironment, CD4⁺ T cells expressed lower LILRB2, LILRB3 and LILRB4 than that from TFL and CD8⁺ T cells expressed decreased LILRB2. And γδ T cells expressed LILRB1 in HCC blood and microenvironment. Surprisingly, the percentage of LILRB1 expressed on MDSC from HCC peripheral blood and tumors was lower than that from healthy donors and corresponding TFL.

CONCLUSIONS

This is the first systemically examination of the LILRB family expression on a variety of immune cells from both peripheral blood and microenvironment in HCC patients. The specific increasing expression of LILRB on immune cells may regulate innate and adaptive immune and impact on HCC progression. Our findings justify further investigation of LILRB function in HCC.

Pathogenesis of uteroplacental acute atherosis: An update on current research

Uteroplacental acute atherosis is a type of arterial vascular disease that affects the placenta during pregnancy and predominates in the maternal spiral arteries in the decidua basalis layer of the pregnant uterus. This condition is characterized by fibrin-like necrosis of the blood vessel walls, the accumulation of macrophages containing fat (foam cells), and the infiltration of macrophages around blood vessels. Uteroplacental acute atherosis is rare in normal pregnancy but occurs more frequently in patients with pregnancy complications, including preeclampsia, spontaneous preterm labor, preterm prelabor rupture of membranes, mid-trimester spontaneous abortion, fetal death, and small-for-gestational age. It is believed that the mechanisms underlying the development of uteroplacental acute atherosis are related to the incomplete physiological transformation of spiral arteries, placental inflammation, abnormal lipid metabolism, and oxidative stress. In this review, we describe the pathogenesis of uteroplacental acute atherosis to provide reference guidelines for the future prevention and treatment of uteroplacental acute atherosclerotic disease.

Pregnancy immune tolerance at the maternal-fetal interface

Pregnancy is a natural process that poses an immunological challenge because non-self fetus must be accepted. During the pregnancy period, the fetus as 'allograft' inherits maternal and also paternal antigens. For successful and term pregnancy, the fetus is tolerated and nurtured enjoying immune privileges that minimize the risk of being rejected by maternal immune system. Multiple mechanisms contribute to tolerate the semi-allogeneic fetus. Here, we summarize the recent progresses on how the maternal immune system actively collaborates to maintain the immune balance and maternal-fetal tolerance.

Molecular mechanism of the effect of angiopoietin-like protein 8 on the proliferation, invasion and migration of placental trophoblasts in preeclampsia

Preeclampsia (PE) is a pregnancy-specific systemic disorder characterized by various manifestations of organ dysfunction. Inadequate trophoblastic invasion of the uterine wall is involved in the pathogenesis of PE. Angiopoietin-like protein 8 (ANGPTL8) serves an important role in cardiovascular disease development and may have a potential effect on cell proliferation. In the present study, downregulation of ANGPTL8 promoted cell proliferation, decreased p21 expression, and increased the expression levels of cyclin-dependent kinase 2 and proliferating cell nuclear antigen in HTR8/SVneo cells. Silencing of ANGPTL8 led to significant acceleration in cell migration and invasion, and markedly enhanced the matrix metalloproteinase (MMP)-2 and MMP-9 expression levels. In addition, the protein expression levels of tissue inhibitor of matrix metalloproteinase (TIMP)-1 and TIMP-2 were decreased in the group transfected with small interfering RNA (si)-ANGPTL8-1 as compared with those in the control and si-negative control groups. Taken together, these results indicated that ANGPTL8 downregulation promoted the proliferation, migration and invasion of trophoblast cells. Thus, ANGPTL8 suppresses the viability, proliferation, migration and invasion of trophoblast cells, and may be a potential therapeutic target for the clinical treatment of PE.

The Roles of Uterine Natural Killer (NK) Cells and KIR/HLA-C Combination in the Development of Preeclampsia: A Systematic Review

Preeclampsia (PE) is termed as a systemic disease that involves multiple organs; however, the exact etiology is still quite unclear. It is believed that the poor remodeling of uterine spiral arteries triggers PE, thereby causing failed placentation and producing inflammatory factors. The decline of blood flow results in lowering the nutrients and oxygen received by the fetus and augmenting the placental pressure in PE. Decidual immune cells, especially uterine natural killer (uNK) cells, are involved in the process of placentation. Decidual NK (dNK) cells significantly contribute to the vascular remodeling through the secretion of cytokines and angiogenic mediators in normal placental development. The abnormal activation of NK cells in both the peripheral blood and the decidua was counted among the causes leading to PE. The correlation existing between maternal killer cell immunoglobulin-like receptor (KIR) and HLA-C in trophoblast cells constitutes a robust evidence for the genetic etiology of PE. The combinations of the two kinds of gene systems, together with the KIR genotype in the mother and the HLA-C group in her fetus, are likely to exactly decide the pregnancy outcome. The women, who have the inappropriate match of KIR/HLA-C, are likely to be prone to the augmented risk of PE. However, the combinations of KIR/HLA-C in PE undergo ethnic changes. The extensive prospective research works in Europe, Asia, and Africa are required for providing more findings in PE patients.

The phenotype of decidual CD56+ lymphocytes is influenced by secreted factors from decidual stromal cells but not macrophages in the first trimester of pregnancy

During the first trimester of pregnancy the decidua is comprised of decidual stromal cells (DSC), invading fetal trophoblast cells and maternal leukocytes, including decidual natural killer (dNK) cells and macrophages. dNK cells are distinct from peripheral blood NK cells and have a role in regulating trophoblast invasion and spiral artery remodelling. The unique phenotype of dNK cells results from the decidual environment in which they reside, however the interaction and influence of other cells in the decidua on dNK phenotype is unknown. We isolated first trimester DSC and decidual macrophages and investigated the effect that DSC and decidual macrophage secreted factors have on CD56+ decidual lymphocyte receptor expression and cytokine secretion (including dNK cells). We report that DSC secreted factors induce the secretion of the cytokines IL-8 and IL-6 from first trimester CD56+ cells. However, neither DSC nor decidual macrophage secreted factors changed CD56+ cell receptor expression. These results suggest that secreted factors from DSC influence CD56+ decidual lymphocytes during the first trimester of pregnancy and therefore may play a role in regulating the unique phenotype and function of dNK cells during placentation.

Placental bed research: II. Functional and immunological investigations of the placental bed

Research on the placenta as the interface between the mother and the fetus has been undertaken for some 150 years, and in 2 subsequent reviews, we attempted to summarize the situation. In the first part, we described the discovery of unique physiological modifications of the uteroplacental spiral arteries, enabling them to cope with a major increase in blood flow necessary to ensure proper growth of the fetus. These consist of an invasion of the arterial walls by trophoblast and a progressive disappearance of its normal structure. Researchers then turned to the pathophysiology of the placental bed and in particular to its maternal vascular tree. This yielded vital information for a better understanding of the so-called great obstetrical syndromes (preeclampsia, fetal growth restriction, premature labor and delivery, placenta accreta). Systematic morphological investigations of the uteroplacental vasculature showed that preeclampsia is associated with decreased or failed transformation of spiral arteries and the persistence of endothelial and smooth muscle cells in segments of their myometrial portion. Here we report on recent functional investigations of the placental bed, including in situ biophysical studies of uteroplacental blood flow and vascular resistance, and manipulation of uteroplacental perfusion. These new methodologies have provided a novel way of identifying pregnancies in which remodeling is impaired. In animals it is now possible to manipulate uteroplacental blood flow, leading to an enhancement of fetal growth; this opens the way to trials in abnormal human pregnancies. In this second part, we explored a new, extremely important area of research that deals with the role of specific subsets of leukocytes and macrophages in the placental bed. The human first-trimester decidua is rich in leukocytes called uterine natural killer cells. Both macrophages and uterine natural killer cells increase in number from the secretory endometrium to early pregnancy and play a critical role in mediating the process of spiral artery transformation by inducing initial structural changes. It seems therefore that vascular remodeling of spiral arteries is initiated independently of trophoblast invasion. Dysregulation of the immune system may lead to reproductive failure or pregnancy complications, and in this respect, recent studies have advanced our understanding of the mechanisms regulating immunological tolerance during pregnancy, with several mechanisms being proposed for the development of tolerance to the semiallogeneic fetus. In particular, these include several strategies by which the trophoblast avoids maternal recognition. Finally, an important new dimension is being explored: the likelihood that pregnancy syndromes and impaired uteroplacental vascular remodeling may be linked to future maternal and even the child's cardiovascular disease risk. The functional evidence underlying these observations will be discussed.

Preeclampsia: a gestational cardiorenal syndrome

It is generally accepted today that there are two different types of preeclampsia: an early-onset or placental type and a late-onset or maternal type. In the latent phase, the first one presents with a low output/high resistance circulation eventually leading in the late second or early third trimester to an intense and acutely aggravating systemic disorder with an important impact on maternal and neonatal mortality and morbidity; the other type presents initially as a high volume/low resistance circulation, gradually evolving to a state of circulatory decompensation usually in the later stages of pregnancy, with a less severe impact on maternal and neonatal outcome. For both processes, numerous dysfunctions of the heart, kidneys, arteries, veins and interconnecting systems are reported, most of them presenting earlier and more severely in early- than in late-onset preeclampsia; however, some very specific dysfunctions exist for either type. Experimental, clinical and epidemiological observations before, during and after pregnancy are consistent with gestation-induced worsening of subclinical pre-existing chronic cardiovascular dysfunction in early-onset preeclampsia, and thus sharing the pathophysiology of cardiorenal syndrome type II, and with acute volume overload decompensation of the maternal circulation in late-onset preeclampsia, thus sharing the pathophysiology of cardiorenal syndrome type 1. Cardiorenal syndrome type V is consistent with the process of preeclampsia superimposed upon clinical cardiovascular and/or renal disease, alone or as part of a systemic disorder. This review focuses on the specific differences in haemodynamic dysfunctions between the two types of preeclampsia, with special emphasis on the interorgan interactions between heart and kidneys, introducing the theoretical concept that the pathophysiological processes of preeclampsia can be regarded as the gestational manifestations of cardiorenal syndromes.

Uterine natural killer cells: Time for a re-appraisal?

The presence of unusual natural killer cells in human endometrium has been recognized for 30 years, but despite considerable research effort, the in vivo role of uterine natural killer (uNK) cells in both normal and pathological pregnancy remains uncertain. uNK cells may differentiate from precursors present in endometrium, but migration from peripheral blood in response to chemokine stimuli with in situ modification to a uNK cell phenotype is also possible. uNK cells produce a wide range of secretory products with diverse effects on trophoblast and spiral arteries which may play an important role in implantation and early placentation. Interactions with other decidual cell populations are also becoming clear. Recent evidence has demonstrated subpopulations of uNK cells and the presence of other innate lymphoid cell populations in decidua which may refine future approaches to investigation of the role of uNK cells in human pregnancy.

Features of Human Decidual NK Cells in Healthy Pregnancy and During Viral Infection

The hallmark of human early pregnancy is the accumulation of a unique population of Natural Killer (dNK) cells at the main maternal-fetal interface, the decidua basalis. dNK cells play a crucial role in successful placentation probably by orchestrating the invasion of trophoblast cells deep into the decidua basalis and remodeling of the maternal spiral arteries. Recent advances in the field emphasize the importance of the local microenvironment in shaping both the phenotype and the effector functions of these innate lymphoid cells. Despite slow progress in the field, ex vivo studies revealed that dNK cells sense and destroy infected cells in order to protect the fetus from invading pathogens. In this review, we will discuss key features of dNK cells during healthy pregnancy as well as their functional adaptations in limiting pathogen dissemination to the growing conceptus. The challenge is to better understand the plasticity of dNK cells in the maternal-fetal interface. Such insights would enable greater understanding of the pathogenesis in congenital infections and pregnancy disorders.

lncRNA HIF1A Antisense RNA 2 Modulates Trophoblast Cell Invasion and Proliferation through Upregulating PHLDA1 Expression

Long noncoding RNAs (lncRNAs) have been reported to be involved in various human diseases, and increasing studies have revealed that lncRNAs can play a vital role in preeclampsia (PE). In our study, lncRNA hypoxia-inducible factor 1 alpha (HIF1A) antisense RNA 2 (HIF1A-AS2) was found to be significantly downregulated in placenta tissues of PE patients by quantitative real-time PCR analysis. Moreover, Cell Counting Kit-8 (CCK-8) assays showed that downregulation of HIF1A-AS2 can impede cell proliferation of HTR-8/SVneo and JAR trophoblasts cells. Ectopic overexpression of HIF1A-AS2 can increase the function of trophoblasts cell migration and invasion in vitro. RNA-sequencing (RNA-seq), RNA immunoprecipitation (RIP), and chromatin immunoprecipitation (ChIP) experiments showed that HIF1A-AS2 can recruit lysine-specific demethylase 1 (LSD1) and epigenetically repress pleckstrin homology-like domain, family A, member 1 (PHLDA1) transcription in human trophoblasts cells. In summary, our findings suggest that downregulated HIF1A-AS2 may play a role in the pathogenesis and progression of PE, and has potential as a novel prognostic marker in PE.

TGFb1 suppresses the activation of distinct dNK subpopulations in preeclampsia

BACKGROUND

Decidual natural killer (dNK) cells are the predominant lymphocytes accumulated at the maternal-fetal interface. Regulatory mechanism of dNK cells in preeclampsia, a gestational complication characterized by high blood pressure and increased proteinuria occurring after 20 weeks pregnancy, is not completely understood.

METHODS

Multi-parameter flow cytometry is applied to investigate the phenotype and function of dNK cells freshly isolated from decidual samples or conditionally cultured by TGFb stimulation.

FINDINGS

In preeclampsia, we documented elevated numbers of CD56⁺ CD3^- dNK cells in close proximity to Foxp3⁺ regulatory T (Treg) cells within the decidua. In vitro experiments using dNK cells from early gestation showed that dNK activation (IFNG, IL-8 and CD107a) can be downregulated by Treg cells. The expression of these markers by dNK cells was significantly lower in preeclampsia. We also observed a positive correlation between the expression of dNK activation receptors (NKp30 and NKG2D) and the expression of IFNG in specific dNK subsets. TGFb levels are increased in the decidua of preeclamptic pregnancies. We analyzed co-expression of activation (IFNG/IL-8/CD107a) and angiogenic (VEGF) markers in dNK cells. TGFb treatment reduced while blockade of TGFb increased co-expression of these markers.

INTERPRETATION

Our findings suggest that elevated decidual TGFb1 supresses the activation of specific subsets of dNK which in turn contributes to the uteroplacental pathology associated with the onset of preeclampsia.

Fetal human leukocyte antigen-C and maternal killer-cell immunoglobulin-like receptors in cases of severe preeclampsia

INTRODUCTION

The pathogenesis of preeclampsia may involve inadequate trophoblast invasion caused by excessive inhibition of uterine natural killer cells (uNK) by extravillous trophoblast cells (EVT). This may be the result of a combination of maternal killer-cell immunoglobin-like receptor (KIR) AA genotype and fetal human leukocyte antigen-C2 (HLA-C2) genotype. A few studies have reported a significantly increased frequency of the maternal KIR AA/fetal HLA-C2 combination in cases of preeclampsia compared to controls.

METHODS

Study subjects were 259 cases of severe preeclampsia/eclampsia and 259 matched pregnant women without preeclampsia or eclampsia. All pregnancies were singleton pregnancies, and mothers were preferentially primigravidae. Blood samples from women and their newborns were obtained from the Danish National Birth Cohort (DNBC) and the Danish Neonatal Screening Biobank. Significant differences in the frequencies of KIR AA and HLA-C2 between cases and controls were investigated.

RESULTS

No significant difference was observed between cases and controls in the frequency of maternal KIR AA (OR = 0.86, 95%CI = 0.60-1.23, P = 0.41), neither when the fetus carried an HLA-C2 allele (OR = 0.85, 95%CI = 0.52-1.38, P = 0.51), nor when the fetus carried an HLA-C2 allele more than its mother (OR = 0.75, 95%CI = 0.34-1.64, P = 0.47).

CONCLUSION

The Results show no influence of HLA-C/KIR genetic variation on the risk of severe preeclampsia, contrary to what some previous studies have observed. An explanation could be that severe preeclampsia represents a separate pathological entity compared to mild preeclampsia.

Ophthalmic artery Doppler for prediction of pre-eclampsia: systematic review and meta-analysis

OBJECTIVE

To determine the accuracy of ophthalmic artery Doppler in pregnancy for the prediction of pre-eclampsia (PE).

METHODS

MEDLINE, EMBASE, CINAHL and The Cochrane Library were searched for relevant citations without language restrictions. Two reviewers independently selected studies that evaluated the accuracy of ophthalmic artery Doppler to predict the development of PE and extracted data to construct 2 × 2 tables. Individual patient data were obtained from the authors if available. A bivariate random-effects model was used for the quantitative synthesis of data. Logistic regression analysis was employed to generate receiver-operating characteristics (ROC) curves and obtain optimal cut-offs for each investigated parameter, and a bivariate analysis was employed using predetermined cut-offs to obtain sensitivity and specificity values and generate summary ROC curves.

RESULTS

A total of 87 citations matched the search criteria of which three studies, involving 1119 pregnancies, were included in the analysis. All included studies had clear description of the index and reference tests, avoidance of verification bias and adequate follow-up. Individual patient data were obtained for all three included studies. First diastolic peak velocity of ophthalmic artery Doppler at a cut-off of 23.3 cm/s showed modest sensitivity (61.0%; 95% CI, 44.2-76.1%) and specificity (73.2%; 95% CI, 66.9-78.7%) for the prediction of early-onset PE (area under the ROC curve (AUC), 0.68; 95% CI, 0.61-0.76). The first diastolic peak velocity had a much lower sensitivity (39.0%; 95% CI, 20.6-61.0%), a similar specificity (73.2%; 95% CI, 66.9-78.7%) and a lower AUC (0.58; CI, 0.52-0.65) for the prediction of late-onset PE. The pulsatility index of the ophthalmic artery did not show a clinically useful sensitivity or specificity at any cut-off for early- or late-onset PE. Peak ratio above 0.65 showed a similar diagnostic accuracy to that of the first diastolic peak velocity with an AUC of 0.67 (95% CI, 0.58-0.77) for early-onset PE and 0.57 (95% CI, 0.51-0.63) for late-onset disease.

CONCLUSIONS

Ophthalmic artery Doppler is a simple, accurate and objective technique with a standalone predictive value for the development of early-onset PE equivalent to that of uterine artery Doppler evaluation. The relationship between ophthalmic Doppler indices and PE cannot be a consequence of trophoblast invasion and may be related to maternal hemodynamic adaptation to pregnancy. The findings of this review justify efforts to elucidate the effectiveness and underlying mechanism whereby two seemingly unrelated maternal vessels can be used for the prediction of a disease considered a 'placental disorder'. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

The association of the placental Hypoxia-inducible factor1-α polymorphisms and HIF1-α mRNA expression with preeclampsia

INTRODUCTION

Evidence has confirmed that placental/fetal hypoxia plays a key role in both endothelial cell dysfunction and PE pathogenesis. The aim of the present study was to investigate whether maternal/placental hypoxia-inducible factor1-α (HIF1-α) C1772T (rs11549465) and/or G1790A (rs11549467) polymorphisms and HIF1-α mRNA expression are associated with PE development.

METHODS

The blood samples of 203 PE and 202 control women and the placenta of 86 PE and 84 control women were collected after delivery. The HIF1-α polymorphisms were genotyped using PCR- RFLP method. The mRNA expression levels were measured by Quantitative Real -Time PCR.

RESULTS

The present study found no association between maternal HIF1-α rs11549465 and rs11549467 and placental rs11549467 polymorphisms and PE. However, the placental rs11549465 polymorphism was associated with PE in the dominant model. The CT/GG combined genotypes and TG haplotype of placental rs11549465 and rs11549467 polymorphisms were associated with higher risk of PE. The HIF1-α mRNA expression was 3-fold higher in the PE women. The rs11549465 TT genotype was associated with higher HIF1-α mRNA expression in PE women and in total population and rs11549467 GA genotype was associated with higher mRNA expression in total population. The relative mRNA expression of HIF1-α gene was higher in presence of CC/GA, TT/GG and TT/GA combined genotypes.

CONCLUSION

This study found an association between placental but not maternal HIF1-α rs11549465 polymorphism and PE in the dominant model. The HIF1-α mRNA expression was higher in the placenta of PE women and was associated with rs11549465 and rs11549467 polymorphisms.

Three macrophage subsets are identified in the uterus during early human pregnancy

Macrophages are crucial for a successful pregnancy, and malfunctions of decidual macrophages correlate with adverse pregnancy outcomes, such as spontaneous abortion and preeclampsia. Previously, decidual macrophages were often thought to be a single population. In the present study, we identified three decidual macrophage subsets, CCR2-CD11cLO (CD11c^low, ~80%), CCR2-CD11cHI (CD11c^high, ~5%), and CCR2+CD11cHI (CD11c^high, 10-15%), during the first trimester of human pregnancy by flow cytometry analysis. CCR2-CD11cLO macrophages are widely distributed in the decidua, while CCR2-CD11cHI and CCR2+CD11cHI macrophages are primarily detected close to extravillous trophoblast cells according to immunofluorescence staining. According to RNA sequencing bioinformatics analysis and in vitro functional studies, these three subsets of macrophages have different phagocytic capacities. CCR2+CD11cHI macrophages have pro-inflammatory characteristics, while the CCR2-CD11cHI population is suggested to be anti-oxidative and anti-inflammatory due to its high expression of critical heme metabolism-related genes, suggesting that these two subsets of macrophages maintain an inflammatory balance at the leading edge of trophoblast invasion to facilitate the clearance of pathogen infection as well as maintain the homeostasis of the maternal-fetal interface. The present study physiologically identifies three decidual macrophage subsets. Further clarification of the functions of these subsets will improve our understanding of maternal-fetal crosstalk in the maintenance of a healthy pregnancy.

Decidual cell regulation of trophoblast is altered in pregnancies at risk of pre-eclampsia

Successful implantation and placentation are dependent on the interaction between decidual stromal cells (DSC) and extravillous trophoblast (EVT) cells. The extent of trophoblast invasion relies on communication between the placenta and maternal decidua. The cyclical process of decidualisation induces a transformation of endometrial fibroblasts to secretory DSC; these secreted products have many functions including the control of trophoblast invasion. Inadequate trophoblast invasion and remodelling of the uterine vessels (the spiral arteries) are associated with pregnancy disorders such as pre-eclampsia. Uterine artery Doppler resistance index (RI) in the first trimester of pregnancy can be used as a proxy measure of remodelling. DSC were isolated from pregnancies with normal (normal RI) or impaired (high RI) spiral artery remodelling. Following isolation, DSC were re-decidualised using cAMP and MPA and secretion of the decidualisation markers IGFBP-1 and prolactin assessed. We examined the impact of DSC-secreted factors on trophoblast cell function, using the EVT cell line SGHPL-4. We demonstrated that DSC exposed to decidual factors were able to re-decidualise in vitro and that the chemoattraction of trophoblasts by DSC is impaired in pregnancies with high RI. This study provides new insights into the role that DSC play in regulating EVT functions during the first trimester of pregnancy. This is the first study to demonstrate that DSC from pregnancies with impaired vascular remodelling in the first trimester secrete factors that inhibit the directional movement of trophoblast cells. This finding may be important in understanding aberrant trophoblast invasion in pregnancies where vascular remodelling is impaired.

Progress in the understanding of the etiology and predictability of fetal growth restriction

Fetal growth restriction (FGR) is defined as the failure of fetus to reach its growth potential for various reasons, leading to multiple perinatal complications and adult diseases of fetal origins. Shallow extravillous trophoblast (EVT) invasion-induced placental insufficiency and placental dysfunction are considered the main reasons for idiopathic FGR. In this review, first we discuss the major characteristics of anti-angiogenic state and the pro-inflammatory bias in FGR. We then elaborate major abnormalities in placental insufficiency at molecular levels, including the interaction between decidual leukocytes and EVT, alteration of miRNA expression and imprinted gene expression pattern in FGR. Finally, we review current animal models used in FGR, an experimental intervention based on animal models and the progress of predictive biomarker studies in FGR.Free Chinese abstract: A Chinese translation of this abstract is freely available at http://www.reproduction-online.org/content/153/6/R215/suppl/DC1.

Uncovering the Pharmacological Mechanism of Astragalus Salvia Compound on Pregnancy-Induced Hypertension Syndrome by a Network Pharmacology Approach

To uncover the pharmacological mechanism of Astragalus Salvia compound (ASC) on pregnancy-induced hypertension syndrome (PIH), to provide useful information for clinical, as well as to connect the basic and clinical by a network pharmacological approach, we used network pharmacological approach. We collected ASC's compounds by traditional Chinese Medicine databases, and input them into PharmMapper to got their targets. Then we acquired PIH targets from Genecards and OMIM, collected the interactions of all the targets and other human proteins via String and INACT. We also constructed the network by Cytoscape and analyze it by MCODE so as to get clusters. Finally, we put all the targets of clusters into DAVID to do GO enrichment analysis. After these, four networks are constructed by Cytoscape; they are PIH network, compound-compound target network of ASC, ASC-PIH network, and compound target-PIH target-other human proteins' PPI network. According to the results, we think that ASC may directly regulate several biological processes and their genes in "endothelial cell activation and injury" and "placental or trophoblast cell ischemia" models to treat PIH. And it may indirectly act on the rest of the biological process to treat PIH or may not.

Angiogenic and antiangiogenic factors in preeclampsia

BACKGROUND

Pre-eclampsia is a multifactorial hypertensive disorder that is triggered by placental insufficiency and that accounts for up to 15% of maternal deaths. In normal pregnancies, this process depends on the balance between the expression of angiogenic factors and antiangiogenic factors, which are responsible for remodeling the spiral arteries, as well as for neoangiogenesis and fetal development.

PURPOSE

The aim of this review is to discuss the main scientific findings regarding the role of angiogenic and antiangiogenic factors in the etiopathogenesis of preeclampsia.

METHODS

An extensive research was conducted in the Pubmed database in search of scientific manuscripts discussing potential associations between angiogenic and antiangiogenic factors and preeclampsia. Ninety-one papers were included in this review.

RESULTS

There is an increased expression of soluble fms-like tyrosine kinase receptor and soluble endoglin in pre-eclampsia, as well as reduced placental expression of vascular endothelial growth factor and placental growth factor. Systemic hypertension, proteinuria and kidney injury - such as enlargement and glomerular fibrin deposit, capillary occlusion due to edema, and hypertrophy of endocapillary cells - are some of these changes. The complex etiopathogenesis of preeclampsia instigates research of different biomarkers that allow for the early diagnosis of this entity, such as vascular endothelial growth factor, placental growth factor, soluble fms-like tyrosine kinase receptor, soluble endoglin, placental glycoprotein pregnancy-associated plasma protein-A and protein 13.

CONCLUSION

Even though it is possible to establish an efficient and effective diagnostic tool, three key principles must be observed in the management of preeclampsia: prevention, early screening and treatment.

Activated NK cells cause placental dysfunction and miscarriages in fetal alloimmune thrombocytopenia

Miscarriage and intrauterine growth restriction (IUGR) are devastating complications in fetal/neonatal alloimmune thrombocytopenia (FNAIT). We previously reported the mechanisms for bleeding diatheses, but it is unknown whether placental, decidual immune cells or other abnormalities at the maternal-fetal interface contribute to FNAIT. Here we show that maternal immune responses to fetal platelet antigens cause miscarriage and IUGR that are associated with vascular and immune pathologies in murine FNAIT models. Uterine natural killer (uNK) cell recruitment and survival beyond mid-gestation lead to elevated NKp46 and CD107 expression, perforin release and trophoblast apoptosis. Depletion of NK cells restores normal spiral artery remodeling and placental function, prevents miscarriage, and rescues hemorrhage in neonates. Blockade of NK activation receptors (NKp46, FcɣRIIIa) also rescues pregnancy loss. These findings shed light on uNK antibody-dependent cell-mediated cytotoxicity of invasive trophoblasts as a pathological mechanism in FNAIT, and suggest that anti-NK cell therapies may prevent immune-mediated pregnancy loss and ameliorate FNAIT.Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a gestational disease caused by maternal immune responses against fetal platelets. Using a FNAIT mouse model and human trophoblast cell lines, here the authors show that uterine natural killer cell-mediated trophoblast apoptosis contributes to FNAIT pathogenesis.

Strategies for investigating the maternal-fetal interface in the first trimester of pregnancy: What can we learn about pathology?

The pathologies of the pregnancy complications pre-eclampsia (PE) and fetal growth restriction (FGR) are established in the first trimester of human pregnancy. In a normal pregnancy, decidual spiral arteries are transformed into wide diameter, non-vasoactive vessels capable of meeting the increased demands of the developing fetus for nutrients and oxygen. Disruption of this transformation is associated with PE and FGR. Very little is known of how these first trimester changes are regulated normally and even less is known about how they are compromised in complicated pregnancies. Interactions between maternal and placental cells are essential for pregnancy to progress and this review will summarise the challenges in investigating this area. We will discuss how first trimester studies of pregnancies with an increased risk of developing PE/FGR have started to provide valuable information about pregnancy at this most dynamic and crucial time. We will discuss where there is scope to progress these studies further by refining the ability to identify compromised pregnancies at an early stage, by integrating information from many cell types from the same pregnancy, and by improving our methods for modelling the maternal-fetal interface in vitro.

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Pathology of PE/FGR begins in the first trimester.

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Investigating pregnancies with increased risk of PE/FGR is giving valuable information.

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This will improve further with advances in identifying compromised pregnancies.

Composition and dynamics of the uterine NK cell KIR repertoire in menstrual blood

Uterine natural killer (NK) cells are abundantly present in endometrium and decidua. Their function is governed by interactions between killer cell immunoglobulin-like receptors (KIRs) and cognate human leukocyte antigen (HLA) class I ligands. These interactions have implications for reproductive success. Whereas most uterine NK cells are known to express KIRs, little information is available about KIR repertoire formation and stability over time. This is primarily due to inherent difficulties in gaining access to human uterine tissue. As endometrial immune cells are shed during menstruation, menstrual blood may serve as a source for studies of KIRs on uterine NK cells. Here, we performed a combined assessment of six inhibitory and activating KIRs on uterine NK cells from paired menstrual and peripheral blood. Menstrual blood contained a high frequency of uterine NK cells expressing KIRs. The uterine NK cell KIR repertoires were markedly different from those in peripheral blood NK cells, biased toward KIR2D-receptor expression, and formed independently of selection conferred by cognate HLA class I molecules. Moreover, uterine NKG2C⁺self-KIR⁺ NK cell expansions were detected. Finally, the distinct KIR repertoires of uterine NK cells were stable over multiple menstrual cycles. Our results provide novel insight into KIR repertoire formation on human uterine NK cells.

The role of decidual NK cells in pregnancies with impaired vascular remodelling

The pathologies of the dangerous pregnancy complications pre-eclampsia (PE) and fetal growth restriction (FGR) are established in the first trimester of human pregnancy yet we know little of how this happens. Finely tuned interactions between maternal and placental cells are essential for pregnancy to progress without complications; however, the precise nature of this cross-talk and how it can go wrong are crucial questions that remain to be answered. This review summarises recent studies examining the role played by natural killer cells in regulating normal placentation and remodelling. Their involvement when it is impaired in PE/FGR pregnancies will additionally be discussed.

The decidua-the maternal bed embracing the embryo-maintains the pregnancy

The decidua has been known as maternal uterine tissue, which plays essential roles in protecting the embryo from being attacked by maternal immune cells and provides nutritional support for the developing embryo prior to placenta formation. However, there are questions that still remain to be answered: (1) How does the decidua supply nutrition and provide a physical scaffold for the growing embryo, before placental vascular connection is established? (2) How is the balance between preventing an anti-embryo immune response and protecting both embryo and mother from infections established? To understand basic personas in decidual tissues, we review the structure of the decidua composed of terminally differentiated uterine stromal cells, blood vessels, and a number of repertoire of uterine local immune cells, including the well-known uterine natural killer (uNK) cells and recently discovered innate lymphoid cells (ILCs). Decidual macrophages and uterine dendritic cells (DCs) are supposed to modulate adaptive immunity via balancing cytokines and promoting generation of regulatory T (T_reg) cells. During decidualization, vascular and tissue remodeling in the uterus provide nutritional and physical support for the developing embryo. Secretion of various cytokines and chemokines from both the embryo and the decidual cells activates multiple signaling network between the mother and the embryo upon implantation. Defects in the decidual development during early pregnancy result in loss of pregnancy or complications in later gestational stage.

Effect of hypoxia on expression of placental trophoblast cells SATB1 and β-catenin and its correlation with the pathogenesis of preeclampsia

OBJECTIVE

To study the effect of hypoxia on the expression of placental trophoblast cells SATB1 and β-catenin and its correlation with the pathogenesis of preeclampsia.

METHODS

Trophoblastic cell lines HRT8/SVneo were cultured, SATB1 and β-catenin expression and cell biological behavior were determined after hypoxia reoxygenation treatment; cell biological behavior and the expression of related genes were determined after the transfection of SATB1 and β-catenin siRNA; preeclampsia placenta and normal placenta tissues were collected and the expression of SATB1 and β-catenin were determined.

RESULTS

OD value, cell migration rate, mRNA contents of SATB1 and β-catenin of H/R group were significantly lower than those of Nor group, cell apoptosis rate was higher than that of Nor group and the number of invasive cells was less than that of Nor group; OD value and bcl-2 mRNA content of SATB1-siRNA group were lower than those of NC group; cell apoptosis rate as well as Bax, Caspase-3, Caspase-6 and Caspase-9 mRNA contents were higher than those of NC group; cell migration rate as well as CTSB, CTSD, MMP2 and MMP9 mRNA contents of β-catenin-siRNA group were lower than those of NC group; the number of invasive cells was less than that of NC group; the expression levels of SATB1 and β-catenin in preeclampsia placenta tissue were significantly lower than those in normal placenta tissue.

CONCLUSIONS

Hypoxia can inhibit the expression of SATB1 and β-catenin in the pathogenesis of preeclampsia, which can affect the proliferation, apoptosis, migration and invasion of cells.

Effect of Indoleamine 2,3-Dioxygenase Expressed in HTR-8/SVneo Cells on Decidual NK Cell Cytotoxicity

PROBLEM

To study the effect of indoleamine 2,3-dioxygenase (IDO) expressed in HTR-8/SVneo cells on NKG2D and NKp46 expression and cytotoxicity of decidual NK (dNK) and peripheral NK (pNK) cells.

METHOD OF STUDY

CD56(+) dNK and pNK cells purified were cultured with HTR-8/SVneo cell conditioned medium (CM), 1-MT+HTR-8/SVneo cell CM, and complete RPMI 1640 medium (negative control) in vitro. The mRNA and protein expression of NKG2D and NKp46 in NK cells were then assessed by qRT-PCR and flow cytometry, respectively. Their cytotoxicity was evaluated with LDH assays, and TNF-α secretion was analyzed by ELISA.

RESULTS

For dNK cells, the mRNA and protein expression of NKp46 as well as NKG2D did not differ significantly among the three groups (P > 0.05), whereas for pNK cells, the expression level was significantly decreased in HTR-8/SVneo cell CM group than the other two groups (P < 0.01). Peripheral NK cells cultured with HTR-8/SVneo cell CM showed reduced cytotoxicity and TNF-α secretion than the other two groups (P < 0.01), although there were no significant differences among three groups for dNK cells (P > 0.05).

CONCLUSION

IDO expressed by HTR-8/SVneo cells can down-regulate NKp46 and NKG2D expression and reduce cytotoxicity in pNK cells, and may contribute to keep dNK cytotoxicity at a low level, suggesting an important role for IDO in the maintenance of normal pregnancy.

To serve and to protect: the role of decidual innate immune cells on human pregnancy

The maternal-fetal interface undergoes dynamic changes that promote successful development of the embryo/fetal allograft during pregnancy. This immune privilege of the conceptus is mediated through local and systemic cellular responses. In species in which endometrial decidualization accompanies pregnancy, unique immune cell niches are found. Many studies have addressed the enigmatic roles of uterine (u)NK cells as killers and helpers because they are frequently found in the uterine lining and decidua of normal and pathological pregnancies. Accumulating evidence indicates that uNK cells are induced and transformed by sensing signals within their microenvironment to both protect the mother from the fetal allograft and support the fetus during its development. Here, we review the mechanisms that modulate these functions of uNK cells during pregnancy. We suggest that uNK cells must be tightly regulated in order to serve these two roles and support a healthy pregnancy.