Aberrant positioning of trophoblast and lymphocytes in the feto-maternal interface with pre-eclampsia

Prevalence of placental bed spiral artery pathology in preeclampsia and fetal growth restriction: A prospective cohort study

BACKGROUND

Preeclampsia and fetal growth restriction (PE/FGR) are pregnancy complications known to be associated with poor utero-placental function due to abnormal "physiological" remodeling of spiral arteries and unfavorable maternal cardiovascular health. However, the prevalence and degree of impaired spiral artery remodeling has not been clearly established.

METHOD

Prospective, multi-center observational cohort study to assess the prevalence of lesions associated with abnormal development of spiral arteries in placental bed biopsies systematically obtained from 121 women undergoing Caesarian section for PE/FGR compared with a reference group of 149 healthy controls.

RESULTS

PE/FGR was associated with a high prevalence of impaired spiral artery remodeling compared with controls (63.6 vs 10.1 %, p < 0.001), and a higher prevalence of non-remodeled spiral arteries without the presence of intramural trophoblast (45.5 vs 6.7 %, p < 0.001), despite abundant interstitial trophoblast invasion in surrounding decidua and myometrium. Normal remodeling was associated with circumferential presence of intramural trophoblast and hardly any trophoblast in surrounding tissue. Acute atherosis (28.9 vs 3.4 %, p < 0.001) and thrombosis (16.5 vs 5.4 %, p = 0.003) lesions were significantly more prevalent in PE/FGR. Impaired remodeling, acute atherosis and thrombosis lesions were equally present in both decidual and myometrial segments of the spiral arteries in both groups. Impaired remodeling was most prominent in the groups with FGR (with or without PE) and thrombosis was most often seen in the group with PE and FGR.

CONCLUSION

PE/FGR is associated with a high prevalence of impaired physiological remodeling and vascular lesions of the uterine spiral arteries in the placental bed.

Are innate lymphoid cells friend or foe in human pregnancy?

Innate lymphoid cells (ILCs) are involved in the innate immune system because they lack specific antigen receptors and lineage markers. ILCs also display phenotypic and characteristic features of adaptive immune cells. Therefore, ILCs are functional in essential interactions between adaptive and innate immunity. ILCs are found in both lymphoid and nonlymphoid tissues and migrate to the area of inflammation during the inflammatory process. ILCs respond to pathogens by producing a variety of cytokines and are involved in the barrier defense of antigens and in many immunological processes such as allergic events. Recent research has shown that ILCs are functional during human pregnancy and have been suggested to be essential for the healthy progression of pregnancy. In this review, we focus on the role of ILCs in human pregnancy by discussing the relationship between ILCs and the pregnancy microenvironment, specifically summarizing the role of ILCs in physiological and pathological pregnancies.

Changes in expression levels of immune cells and inflammatory cytokines in pre-eclampsia patients before and after delivery

OBJECTIVE

By analyze the expression levels of immune cells and cytokines secreted by preeclampsia patients before and after delivery. Furthermore, to determine the inflammatory and immunological mechanism responsible for preeclampsia, to provide better future prevention and treatment.

METHODS

Twenty-one preeclampsia-diagnosed pregnant women were involved in this study as an observation group. Twenty pregnant women with no history of PE, age-matched, were added to the control group. Thirty NP women, age-matched were included as the reference. The levels of cytokines secreted by T, B, NK and Treg immune cells and Th1, Th2 and Th17 cells were detected before and after delivery.

RESULTS

The number of CD3 + cells in women without preeclampsia before delivery was not statistically different from that in PE patients, but the number of CD4 + and CD8 + cells was lower than that in women without preeclampsia. After delivery, CD4 + cells were larger than those in pregnant women without preeclampsia, while CD8 + cells were smaller than those in pregnant women without preeclampsia. The level of cytokines secreted by Th1 in pregnant women without preeclampsia before delivery was higher than that in PE patients. The levels of cytokines produced by Th1, Th2 and Th17 cells before and after delivery were higher in pregnant women without preeclampsia than in NP women, while Th2 and Th17 were in PE group.

CONCLUSION

PE patients may reduce CD4 + cells and CD8 + cells, and down-regulate the level of cytokines (especially TNF-β) secreted by Th1 cells to reduce the maternal rejection of embryos, thereby reducing the risk of premature delivery, which is a protective adaptive compensation mechanism in favor of embryos.

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.

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.

The New Old CD8+ T Cells in the Immune Paradox of Pregnancy

CD8+ T cells are the most frequent T cell population in the immune cell compartment at the feto-maternal interface. Due to their cytotoxic potential, the presence of CD8+ T cells in the immune privileged pregnant uterus has raised considerable interest. Here, we review our current understanding of CD8+ T cell biology in the uterus of pregnant women and discuss this knowledge in relation to a recently published immune cell Atlas of human decidua. We describe how the expansion of CD8+ T cells with an effector memory phenotype often presenting markers of exhaustion is critical for a successful pregnancy, and host defense towards pathogens. Moreover, we review new evidence on the presence of long-lasting immunological memory to former pregnancies and discuss its impact on prospective pregnancy outcomes. The formation of fetal-specific memory CD8+ T cell subests in the uterus, in particular of tissue resident, and stem cell memory cells requires further investigation, but promises interesting results to come. Advancing the knowledge of CD8+ T cell biology in the pregnant uterus will be pivotal for understanding not only tissue-specific immune tolerance but also the etiology of complications during pregnancy, thus enabling preventive or therapeutic interventions in the future.

Significance of inhibitory maternal killer-cell immunoglobulin-like receptor (KIR) and fetal KIR ligand genotype combinations in placenta related obstetric complications

Some maternal killer-cell immunoglobulin-like receptor (KIR) and fetal KIR ligand genotypes are associated with obstetric complications, such as recurrent miscarriage, fetal growth restriction, preeclampsia, and preterm birth. However, how KIR/KIR ligand genotypes affect these placenta-related obstetric complications has not been fully understood. We aimed to demonstrate the association of maternal KIR-fetal KIR ligand genotype combinations with immunological/metabolic risk factor associated placenta-related obstetric complications. This study consisted of three groups of pregnant women: 1) Miscarriage group (n = 30), 2) Complicated Pregnancy (CP) group (n = 30), and 3) Control group (n = 30). The observed maternal genotype frequencies of all inhibitory and activating KIRs were similar in all groups (p > 0.05). However, inhibitory 2DL3 was quite frequent in the miscarriage group (p = 0.052). There was no difference between groups in terms of centromeric and telomeric maternal haplotypes (p > 0.05). The fetal group 1 HLA-C genotype was frequently detected in the miscarriage and CP groups with rates of 83.3 % and 93.3 % respectively, while the observed frequency was 70 % in the control group. The fetal group 2 HLA-C genotype was the same in all groups. The results demonstrated significantly less fetal group 2 HLA-C homozygosity in the CP groups when compared to the control group (p = 0.020). The fetal HLA-Bw4 genotype was detected more frequently in the miscarriage and CP groups (p = 0.028 and p = 0.001, respectively). The inhibitory KIR/KIR ligand genotype combinations of 2DL3-C1 and 3DL1-Bw4 were more frequent in the miscarriage and CP groups (p = 0.045 and p = 0.002, respectively). Enhanced NK cell inhibition may be one of the mechanisms underlying placenta-related obstetric complications.

Biology and pathology of the uterine microenvironment and its natural killer cells

Tissues are the new frontier of discoveries in immunology. Cells of the immune system are an integral part of tissue physiology and immunity. Determining how immune cells inhabit, housekeep, and defend gut, lung, brain, liver, uterus, and other organs helps revealing the intimate details of tissue physiology and may offer new therapeutic targets to treat pathologies. The uterine microenvironment modulates the development and function of innate lymphoid cells [ILC, largely represented by natural killer (NK) cells], macrophages, T cells, and dendritic cells. These immune cells, in turn, contribute to tissue homeostasis. Regulated by ovarian hormones, the human uterine mucosa (endometrium) undergoes ~400 monthly cycles of breakdown and regeneration from menarche to menopause, with its fibroblasts, glands, blood vessels, and immune cells remodeling the tissue into the transient decidua. Even more transformative changes occur upon blastocyst implantation. Before the placenta is formed, the endometrial glands feed the embryo by histiotrophic nutrition while the uterine spiral arteries are stripped of their endothelial layer and smooth muscle actin. This arterial remodeling is carried out by invading fetal trophoblast and maternal immune cells, chiefly uterine NK (uNK) cells, which also assist fetal growth. The transformed arteries no longer respond to maternal stimuli and meet the increasing demands of the growing fetus. This review focuses on how the everchanging uterine microenvironment affects uNK cells and how uNK cells regulate homeostasis of the decidua, placenta development, and fetal growth. Determining these pathways will help understand the causes of major pregnancy complications.

The enrichment of neutrophil extracellular traps impair the placentas of systemic lupus erythematosus through accumulating decidual NK cells

Despite the advances made in the management of pregnancies in women with systemic lupus erythematosus (SLE), the rate of adverse pregnancy outcomes is still higher than that in the general population. In the last few years, neutrophil extracellular traps (NETs) were proven to be detrimental in both autoimmune diseases and placental injury. We investigated whether NETs could be detected in the placentas of pregnant individuals with SLE and explored the relationship between NETs and decidual natural killer cells (dNKs), which comprise the majority of immune cells at the maternal–fetal interface, using clinical samples and animal models. In this study, we found that the infiltration of NETs and dNKs, especially CD56⁺CD16⁺ NK cells, was significantly increased in pregnant individuals with SLE with placental insufficiency. In the murine models of SLE, the number of dNKs was significantly decreased due to the decreased formation of NETs affected by Ly6G. Moreover, the histopathological placental injury was reduced, with a remarkable increase in fetal birth weight. This study shows that NETs may contribute to immunological disorder in the placenta and the pathological changes in pregnancies with SLE, which provides a research basis for further explorations of the mechanism of SLE in placental impairment.

Cannabinoid Signalling in Immune-Reproductive Crosstalk during Human Pregnancy

Despite the intricate involvement of the endocannabinoid system in various physiological processes, it remains one of the most under-studied biological systems of the human body. The scope of endocannabinoid signalling is widespread, ranging from modulation of immune responses in innate and adaptive immunity to gestational processes in female physiology. Cannabinoid receptors are ubiquitously distributed in reproductive tissues and are thought to play a role in regulating the immune-reproductive interactions required for successful pregnancy, specifically among uterine natural killer cells and placental extravillous trophoblasts. The use of cannabis during pregnancy, however, can perturb endocannabinoid homeostasis through effects mediated by its major constituents, Δ-9-tetrahydrocannabinol and cannabidiol. Decidualization of the endometrium, invasion, and angiogenesis may be impaired as a consequence, leading to clinical complications such as miscarriage and preeclampsia. In this review, the crosstalk between endocannabinoid signalling in uterine natural killer cells and placental extravillous trophoblasts will be examined in healthy and complicated pregnancies. This lays a foundation for discussing the potential of targeting the endocannabinoid system for therapeutic benefit, particularly with regard to the emerging field of synthetic cannabinoids.

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.

Regulation of Uterine Spiral Artery Remodeling: a Review

Extravillous trophoblast remodeling of the uterine spiral arteries is essential for promoting blood flow to the placenta and fetal development, but little is known about the regulation of this process. A defect in spiral artery remodeling underpins adverse conditions of human pregnancy, notably early-onset preeclampsia and fetal growth restriction, which result in maternal and fetal morbidity and mortality. Many in vitro studies have been conducted to determine the ability of growth and other factors to stimulate trophoblast cells to migrate across a synthetic membrane. Clinical studies have investigated whether the maternal levels of various factors are altered during abnormal human pregnancy. Animal models have been established to assess the ability of various factors to recapitulate the pathophysiological symptoms of preeclampsia. This review analyzes the results of the in vitro, clinical, and animal studies and describes a nonhuman primate experimental paradigm of defective uterine artery remodeling to study the regulation of vessel remodeling.

Reduced frequency and functional defects of CD4+CD25highCD127low/- regulatory T cells in patients with unexplained recurrent spontaneous abortion

BACKGROUND

Unexplained recurrent spontaneous abortion (URSA) is defined as two or more consecutive pregnancy losses, generally of unknown cause; it is related to a failure of fetal-maternal immunological tolerance. Regulatory T cells (Tregs) exert immunosuppressive effects, which are essential to maintain fetal-maternal immunological tolerance and regulate immune balance. In this study, we used the specific cell-surface phenotype of CD4⁺CD25^highCD127^low/- Tregs to investigate the number and suppressive function of Tregs isolated from the peripheral blood of patients with URSA with the aim of expanding our understanding of their role in URSA.

METHODS

We isolated a relatively pure population of peripheral CD4⁺CD25^highCD127^low/- Tregs and CD4⁺CD25^- responder T cells (Tresps) from the patients with URSA and normal fertile nonpregnant control women via fluorescence-activated cell sorting. We compared the frequency, suppressive capacity, and forkhead box transcription factor P3 (FOXP3) expression of Tregs in the peripheral blood between patients with URSA and normal controls.

RESULTS

The frequency of CD4⁺CD25^highCD127^low/- Tregs in the peripheral blood was lower in URSA patients than in the controls (P < 0.05). The mean fluorescence intensity of FOXP3 and FOXP3 mRNA expression in Tregs was also significantly lower in the URSA patients (P < 0.01). Tregs suppressed the activity of autologous Tresps stimulated with anti-CD3/CD28 beads in a concentration-dependent manner, with the strongest suppression occurring in cocultures with a 1:1 Treg:Tresp ratio in both groups; however, patient-derived Tregs exhibited a poorer capacity to suppress the proliferation of autologous Tresps than the Tregs from normal controls (P < 0.01). Moreover, Tregs isolated from URSA patients inhibited the proliferation of Tresps from normal controls less potently than the Tregs from normal controls (P < 0.01), and Tresps from URSA patients were less effectively suppressed by autologous Tregs than by those from normal controls (P < 0.01). Tresp activity were intact in both groups.

CONCLUSIONS

We observed a lower frequency of peripheral CD4⁺CD25^highCD127^low/- Tregs with lower FOXP3 expression in the peripheral blood of URSA patients. In addition, highly purified Tregs from patients with URSA exhibited impaired suppressive effects. The defect in immune regulation in URSA patients appears to be primarily related to impaired Tregs, and not to increased resistance of Tresps to suppression. Our findings reveal a potential novel therapeutic target for URSA.

Dynamic Function and Composition Changes of Immune Cells During Normal and Pathological Pregnancy at the Maternal-Fetal Interface

A successful pregnancy requires a fine-tuned and highly regulated balance between immune activation and embryonic antigen tolerance. Since the fetus is semi-allogeneic, the maternal immune system should exert tolerant to the fetus while maintaining the defense against infection. The maternal-fetal interface consists of different immune cells, such as decidual natural killer (dNK) cells, macrophages, T cells, dendritic cells, B cells, and NKT cells. The interaction between immune cells, decidual stromal cells, and trophoblasts constitute a vast network of cellular connections. A cellular immunological imbalance may lead to adverse pregnancy outcomes, such as recurrent spontaneous abortion, pre-eclampsia, pre-term birth, intrauterine growth restriction, and infection. Dynamic changes in immune cells at the maternal-fetal interface have not been clearly stated. While many studies have described changes in the proportions of immune cells in the normal maternal-fetus interface during early pregnancy, few studies have assessed the immune cell changes in mid and late pregnancy. Research on pathological pregnancy has provided clues about these dynamic changes, but a deeper understanding of these changes is necessary. This review summarizes information from previous studies, which may lay the foundation for the diagnosis of pathological pregnancy and put forward new ideas for future studies.

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.

Immune Cells at the Fetomaternal Interface: How the Microenvironment Modulates Immune Cells To Foster Fetal Development

Immune cells adapt their phenotypic and functional characteristics in response to the tissue microenvironment within which they traffic and reside. The fetomaternal interface, consisting of placental trophoblasts and the maternal decidua, is a highly specialized tissue with a unique and time-limited function: to nourish and support development of the semiallogeneic fetus and protect it from inflammatory or immune-mediated injury. It is therefore important to understand how immune cells within these tissues are educated and adapt to fulfill their biological functions. This review article focuses on the local regulatory mechanisms ensuring that both innate and adaptive immune cells appropriately support the early events of implantation and placental development through direct involvement in promoting immune tolerance of fetal alloantigens, suppressing inflammation, and remodeling of maternal uterine vessels to facilitate optimal placental function and fetal growth.

Chronic infusion of interleukin-17 promotes hypertension, activation of cytolytic natural killer cells, and vascular dysfunction in pregnant rats

Previous studies by our lab have established that placental-ischemia stimulated T-helper 17 cells (TH 17s) cause increased cytolytic natural killer (cNK) cell proliferation and activation during pregnancy; however, the exact mechanism is unknown. The objective of this study was to investigate the role of interlukin 17 (IL-17) in inducing cNK cell activation in pregnancy. We infused 150 pg/day of recombinant IL-17 into a subset of normal pregnant (NP) Sprague Dawley rats from gestation day (GD) 12-19 (NP+IL-17). On GD 19, mean arterial pressure (MAP), fetal and placental weights, cytokines, cNK cell activation, cytotoxic enzymes, and vascular reactivity were assessed. MAP significantly increased from 99 ± 3 mmHg in NP to 120 ± 1 mmHg in NP+IL-17 (P < 0.05). Fetal weight significantly decreased from 2.52 ± 0.04 g in NP to 2.32 ± 0.03 g in NP+IL-17 as did placental weight (NP: 0.65 ± 0.03 g; NP+IL-17: 0.54 ± 0.01 g, P < 0.05). Plasma levels of TNF-α increased to 281.4 ± 55.07 pg/mL in NP+IL-17 from 145.3 ± 16.03 pg/mL in NP (P < 0.05) while placental levels of VEGF decreased from 74.2 ± 6.48 pg/mg in NP to 54.2 ± 3.19 pg/mg in NP+IL-17. Total NK cells were increased in the placenta (NP: 14.3 ± 3.49%; NP+IL-17: 29.33 ± 2.76%, P < 0.05) as were cytolytic NK cells (NP: 3.31 ± 1.25%; NP+IL-17: 13.41 ± 1.81%, P < 0.05). A similar trend was observed in circulating NK cells. Plasma granzyme K increased from 3.55 ± 2.29 pg/mL in NP to 20.9 ± 7.76 pg/mL in NP+IL-17 (P < 0.05), and plasma granzyme B increased from 10.95 ± 0.64 pg/mL in NP to 14.9 ± 0.98 pg/mL in NP+IL-17(P < 0.05). In the placenta, both granzyme A (NP: 246.1 ± 16.7 pg/mg; NP+IL-17: 324.3 ± 15.07 pg/mg, P < 0.05) and granzyme B (NP: 15.18 ± 3.79 pg/mg; NP+IL-17: 27.25 ± 2.34 pg/mg, P < 0.05) increased in response to IL-17 infusion. Finally, vascular reactivity of uterine arteries was significantly impaired in response to IL-17 infusion. The results of this study suggest that IL-17 plays a significant role in the activation of cNK cells during pregnancy.

T lymphocytes in the third trimester decidua in preeclampsia

OBJECTIVE

The aim of study was to conduct immunohistochemical quantification of CD3+ and CD8+ decidual lymphocytes in preeclampsia.

METHODS

A study group included 30 cases of preeclampsia and a control group included 20 healthy pregnant women, all delivered by Cesarean section. Samples of placental bed were analyzed after immunohistochemical staining of CD45+, CD3+ and CD8+ cells.

RESULTS

The group with preeclampsia included a significantly higher number of CD3+ (p < 0.01) and CD8+ (p < 0.05) T lymphocytes.

CONCLUSION

It is certain that thebalance dysregulation of T cell of the immune milieu of deciduais of importance in etiopathogenesis and manifestations of preeclampsia.

Expression of dNK cells and their cytokines in twin pregnancies with preeclampsia

OBJECTIVES

To assess the expression of decidual natural killer (dNK) cells and their cytokines in twin pregnancies with preeclampsia.

METHODS

This was a prospective case-control study. The inclusion criteria were diamniotic (monochorionic or dichorionic) twin pregnancies in the third trimester with negative serological results for infectious diseases; absence of major fetal abnormalities or twin-twin transfusion syndrome; and no history of administration of corticosteroids in this pregnancy. The control group (CG) included uncomplicated twin pregnancies, and the preeclampsia group (PEG) included twin gestations with clinical and laboratory confirmation of the disease according to well-established criteria. Samples of the decidua were obtained and analyzed by immunohistochemistry for the expression of dNK cells and interleukins (ILs) 10, 12 and 15. In addition, maternal serum samples were collected to determine the levels of these interleukins.

RESULTS

Thirty twin pregnancies were selected: 20 in the control group (CG) and 10 in the preeclampsia group (PEG). The PEG showed strong placental immunostaining for IL-15 (p=0.001) and high maternal serum levels of IL-10 (22.7 vs. 11.9 pg/mL, p=0.024) and IL-15 (15.9 vs. 7.4 pg/mL, p=0.024).

CONCLUSION

A higher maternal serum concentration of both pro- and anti-inflammatory factors was observed in the twin pregnancies in the PEG. However, no difference in placental expression of IL-10 was found between the groups. These findings may suggest that maternal attempts to balance these interleukins were not sufficient to cause a placental response, and this failure may contribute to the development of preeclampsia.

Regulation of Placental Extravillous Trophoblasts by the Maternal Uterine Environment

During placentation invasive extravillous trophoblasts (EVTs) migrate into the maternal uterus and modify its vessels. In particular, remodeling of the spiral arteries by EVTs is critical for adapting blood flow and nutrient transport to the developing fetus. Failures in this process have been noticed in different pregnancy complications such as preeclampsia, intrauterine growth restriction, stillbirth, or recurrent abortion. Upon invasion into the decidua, the endometrium of pregnancy, EVTs encounter different maternal cell types such as decidual macrophages, uterine NK (uNK) cells and stromal cells expressing a plethora of growth factors and cytokines. Here, we will summarize development of the EVT lineage, a process occurring independently of the uterine environment, and formation of its different subtypes. Further, we will discuss interactions of EVTs with arteries, veins and lymphatics and illustrate how the decidua and its different immune cells regulate EVT differentiation, invasion and survival. The present literature suggests that the decidual environment and its soluble factors critically modulate EVT function and reproductive success.

Innate immune cells in the placental bed in healthy pregnancy and preeclampsia

Immune cells in the placental bed are important for adequate development of the placental bed. The most prominent immune cells in the placental bed early in pregnancy are uterine natural killer cells (uNK) cells and macrophages. Also dendritic cells and mast cells can be found in the early placental bed. These cells not only have an immune regulatory function, but are also involved in the regulation of trophoblast invasion, angiogenesis and spiral artery remodeling. In preeclampsia, one of the major complications of pregnancy, decreased trophoblast invasion and spiral artery remodeling has been found. This is associated with decreased numbers of uNK cells, increased numbers of macrophages around the spiral arteries and similar or increased numbers of dendritic cells in the placental bed. In this review, we discuss the current insights in the functions of uNK cells, macrophages, dendritic cells and mast cells in the placental bed in humans during healthy pregnancy and during preeclampsia. As animal models are instrumental in understanding the role of immune cells in the placental bed, we also review studies on the function and phenotype of these innate immune cells in experimental preeclampsia. A better understanding of the dynamics and functional changes of these immune cells in the placental bed may eventually lead to new therapeutic targets for preeclampsia.

Number of decidual natural killer cells & macrophages in pre-eclampsia

Background & objectives:

The process of human placentation is complex and still not well understood. This study was aimed to examine the relationship between clinical features of pre-eclampsia and degree of trophoblastic invasion after its immunohistochemical visualization in the context of possible alterations in the number of natural killer (NK) cells and macrophages in the decidua.

Methods:

This prospective study included a study group comprising 30 pregnant women with pre-eclampsia delivered by caesarean section and a control group comprising 20 healthy pregnant women also delivered by caesarean section. Samples of placental bed obtained during caesarean section were analyzed after immunohistochemical labelling CD56⁺ NK cells, CD68⁺ macrophages and cytokeratin 7 trophoblastic cells.

Results:

In pre-eclampsia, there was a significantly lower number of CD56⁺ NK cells in the decidua (P<0.001) and a higher number of CD68⁺ macrophages (P<0.001) compared to control group. In the subgroup of pre-eclampsia with intrauterine growth retardation (IUGR), a significantly greater number of NK cells (P<0.05) was recorded, as well as an increased number of macrophages, but not significantly compared to pre-eclampsia without IUGR. There was no significant difference in the distribution of these cells in the decidua in relation to the severity of pre-eclampsia. CD56⁺ NK cells were significantly less (P<0.05) and macrophages were more (P<0.05) in the group with poor trophoblastic invasion.

Interpretation & conclusions:

Alterations in the number of immune cells in relation to the degree of trophoblastic invasion indicated their role in aetiopathogenesis of pre-eclampsia, while the direct association between their number and severity of pre-eclampsia was not confirmed.

HHV-6A Infection of Endometrial Epithelial Cells Induces Increased Endometrial NK Cell-Mediated Cytotoxicity

Background: We have recently reported the presence of Human herpesvirus-6A (HHV-6A) DNA in the 43% of endometrial epithelial cells from primary idiopathic infertile women, with no positivity in fertile women. To investigate the possible effect of HHV-6A infection in endometrial (e)NK cells functions, we examined activating/inhibitory receptors expressed by eNK cells and the corresponding ligands on endometrial cells during HHV-6A infection.

Methods: Endometrial biopsies and uterine flushing samples during the secretory phase were obtained from 20 idiopathic infertile women and twenty fertile women. HHV-6A infection of endometrial epithelial cells was analyzed by Real-Time PCR, immunofluorescence and flow cytometry. eNKs receptors and endometrial ligands expression were evaluated by immunofluorescence and flow cytometry.

Results: We observed the presence of HHV-6A infection (DNA, protein) of endometrial epithelial cells in the 40% of idiopathic infertile women. The eNK from all the subgroups expressed high levels of NKG2D and NKG2A receptors. Functional studies showed that NKG2D activating receptor and FasL are involved in the acquired cytotoxic function of eNK cells during HHV-6A infection of endometrial epithelial cells. In the presence of HHV-6A infection, eNK cells increased expression of CCR2, CXCR3 and CX3CR1 chemokine receptors (p = 0.01) and endometrial epithelial cells up-modulated the corresponding ligands: MCP1 (Monocyte chemotactic protein 1, CCL2), IP-10 (Interferon gamma-induced protein 10, CXCL10) and Eotaxin-3 (CCL26).

Conclusion: Our results, for the first time, showed the implication of eNK cells in controlling HHV-6A endometrial infection and clarify the mechanisms that might be implicated in female idiopathic infertility.

Upregulated unique long 16 binding protein 1 detected in preeclamptic placenta affects human extravillous trophoblast cell line (HTR-8/SVneo) invasion by modulating the function of uterine natural killer cells

Well-controlled trophoblast invasion at the maternal-fetal interface is crucial for normal placentation and successful pregnancy, otherwise pathological conditions of pregnancy occur, such as preeclampsia. In previous studies, it has been demonstrated that unique long 16 binding protein (ULBP)1, a ligand for the natural-killer group (NKG)2D receptor on uterine natural killer (uNK) cells, is upregulated in the placenta in patients with preeclampsia. As they are present on the majority of the decidua, uNK have an important role in pregnancy. The aim of the present study was to determine the role of ULBP1 in trophoblast cell invasion, which is closely associated with the occurrence of preeclampsia. In the present study, ULBP1 expression levels in placentas collected after cesarean section from women with preeclampsia and normal pregnant women were determined by immunohistochemistry, reverse transcription-quantitative polymerase chain reaction and western blotting. The effects of ULBP1 on extravillous trophoblast cell line (HTR-8/SVneo) invasion mediated via uNK cells and the underlying mechanisms were investigated. mRNA and protein expression levels of ULBP1 were significantly upregulated (P<0.05) in preeclamptic placentas compared with normal controls. ULBP1 inhibited HTR-8/SVneo cells via the regulation of biological functions of uNK cells, including the downregulation of NKG2D expression on uNK cells and the stimulation of production of cytokines and chemokines that affect extravillous cytotrophoblast invasion by uNK cells. ULBP1 may have an important role in the pathophysiology of preeclampsia through the modification of biological functions of uNK cells, which may affect trophoblast invasion.

Evidence-Based Revised View of the Pathophysiology of Preeclampsia

Preeclampsia is a life-threatening vascular disorder of pregnancy due to a failing stressed placenta. Millions of women risk death to give birth each year and globally each year, almost 300,000 lose their life in this process and over 500,000 babies die as a consequence of preeclampsia. Despite decades of research, we lack pharmacological agents to treat it. Maternal endothelial oxidative stress is a central phenomenon responsible for the preeclampsia phenotype of high maternal blood pressure and proteinuria. In 1997, it was proposed that preeclampsia arises due to the loss of VEGF activity, possibly due to elevation in anti-angiogenic factor, soluble Flt-1 (sFlt-1). Researchers showed that high sFlt-1 and soluble endoglin (sEng) elicit the severe preeclampsia phenotype in pregnant rodents. We demonstrated that heme oxygenase-1 (HO-1)/carbon monoxide (CO) pathway prevents placental stress and suppresses sFlt-1 and sEng release. Likewise, hydrogen sulphide (H₂S)/cystathionine-γ-lyase (Cth) systems limit sFlt-1 and sEng and protect against the preeclampsia phenotype in mice. Importantly, H₂S restores placental vasculature, and in doing so improves lagging fetal growth. These molecules act as the inhibitor systems in pregnancy and when they fail, preeclampsia is triggered. In this review, we discuss what are the hypotheses and models for the pathophysiology of preeclampsia on the basis of Bradford Hill causation criteria for disease causation and how further in vivo experimentation is needed to establish 'proof of principle'. Hypotheses that fail to meet the Bradford Hill causation criteria include abnormal spiral artery remodelling and inflammation and should be considered associated or consequential to the disorder. In contrast, the protection against cellular stress hypothesis that states that the protective pathways mitigate cellular stress by limiting elevation of anti-angiogenic factors or oxidative stress and the subsequent clinical signs of preeclampsia appear to fulfil most of Bradford Hill causation criteria. Identifying the candidates on the roadmap to this pathway is essential in developing diagnostics and therapeutics to target the pathogenesis of preeclampsia.

Is parturition-timing machinery related to the number of inhibitor CD94/NKG2A positive uterine natural killer cells?

PURPOSE

Prematurity is the most common cause of infant mortality and morbidity. To prevent this, the timing of parturition and its mechanisms should be understood. It is likely that inhibitor CD94/NKG2A positive decidual natural killer cells (uNK) provide for the continuation of pregnancy. Here, we aimed to evaluate whether CD94/NKG2A positive uNK cells are highest in elective cesarian section (C/S) (suggesting ongoing gestation), moderate in normal full-term birth, and lowest in pre-eclamptic parturition.

METHODS

Of 48 pregnant women, 21 C/S, 16 normal, and 11 pre-eclamptic deliveries were included in this study. Five placentas in each group were assigned randomly. After staining, the volumetric analysis of the placental villi and villous blood vessels was performed via the Cavalieri principle. The CD94/NKG2A positive uNK cells were counted using the physical disector method.

RESULTS

The gestation periods and birth weights of the pre-eclamptic deliveries were lower than those of the other two groups. Additionally, the villi and villous vascular volumes were lowest in the pre-eclamptic placentas. As proposed in our hypothesis, the inhibitor CD94/NKG2A positive uNK cells were the highest in the C/S, moderate in the normal, and lowest in the pre-eclamptic placentas.

CONCLUSIONS

These data suggest that CD94/NKG2A positive uNK cells are related with the continuation of pregnancy, and that our human model could be used to search for parturition-timing machinery. We believe that CD94/NKG2A positive uNK cells are also related to the timing of birth.

Acute atherosis in vacuum suction biopsies of decidua basalis: An evidence based research definition

BACKGROUND

Acute atherosis (AA) of the uteroplacental spiral arteries has been characterised by subendothelial lipid-laden foam cells, perivascular leukocyte infiltrates (PVI) and fibrinoid necrosis. Because precise diagnostic criteria are not available for comparative research studies we developed and tested new simplified criteria based on 237 cases.

METHODS

Decidual basalis samples were collected by vacuum suction at elective cesarean deliveries. Spiral arteries were evaluated in serial decidual tissue sections from women with normal pregnancy, preeclampsia, and diabetes. Features of AA were sought in parallel sections stained with H&E and immunostained for CD68, cytokeratin CK7 and desmin, and costained with Periodic Acid Schiff (PAS).

RESULTS

Foam cell lesions were defined as two or more adjacent, intramural, vacuolated CD68 positive cells, PVI as a focal perivascular lymphocyte accumulation, more dense than in the surrounding decidua. Increased fibrinoid (PAS positive) was identified if present in ≥75% of the arterial wall circumference. PVI and increased fibrinoid were significantly associated with preeclampsia but not specifically associated with the presence of foam cell lesions. Hence we diagnosed decidua basalis AA lesions solely by the presence of foam cell lesions, occurring in preeclampsia (37%), diabetes (10%) and healthy normotensive women (11%). The simplified criterion was reproducible by different investigators. Decidua basalis AA occurred most commonly and extensively in preeclampsia, but did not distinguish between preterm and term disease.

DISCUSSION

Our evidence based criterion for decidua basalis AA diagnosis in vacuum suction biopsies may not apply to myometrial or decidua parietalis arteries. In decidual basalis samples it should facilitate comparisons between research studies, to improve pathophysiological understanding of AA and preeclampsia.

The possible role of virus-specific CD8(+) memory T cells in decidual tissue

The most abundant lymphocyte present in decidual tissue is the CD8(+) T cell. It has been shown that most decidual CD8(+) T cells have an effector-memory phenotype, but expressed reduced levels of perforin and granzyme B compared with the peripheral CD8(+) effector-memory T cells. The specificity of these CD8(+) memory T cells has yet to be determined. One hypothesis is that the decidual memory T cells are virus-specific T cells that should protect the fetus against incoming pathogens. As virus-specific CD8(+) memory T cells can cross-react with human leukocyte alloantigens, an alternative, but not mutually exclusive, hypothesis is that these CD8(+) T cells are fetus-specific. Using virus-specific tetramers, we found increased percentages of virus-specific CD8(+) T cells in decidual tissue compared with peripheral blood after uncomplicated pregnancy. So far, no evidence has been obtained for a cross-reactive response of these virus-specific T cells to fetal human leukocyte antigens. These results suggest that the virus-specific memory T cells accumulate in the placenta to protect the fetus from a harmful infection.

The Role of Uterine NK Cells in Normal Reproduction and Reproductive Disorders

The human endometrium contains a substantial population of leucocytes which vary in distribution during the menstrual cycle and pregnancy. An unusual population of natural killer (NK) cells, termed uterine NK (uNK) cells, are the most abundant of these cells in early pregnancy. The increase in number of uNK cells in the mid-secretory phase of the cycle with further increases in early pregnancy has focused attention on the role of uNK cells in early pregnancy. Despite many studies, the in vivo role of these cells is uncertain. This chapter reviews current information regarding the role of uNK cells in healthy human pregnancy and evidence indicating their importance in various reproductive and pregnancy problems. Studies in humans are limited by the availability of suitable tissues and the limitations of extrapolation from animal models.

Ultrastructure alteration of decidual natural killer cells in women with unexplained recurrent miscarriage: a possible association with impaired decidual vascular remodelling

This study aimed to evaluate the extent of remodelling of intra-decidual segments of the spiral arteries in human deciduas between the 6th and 10th gestational weeks in women with unexplained recurrent miscarriages (RM) in comparison to gestational-matched controls. A possible association with the number, immunoexpressive behaviour and ultrastructural changes of decidual natural killer cells (dNKCs) was investigated. Decidual biopsies were obtained from RM cases (n = 40) and women with no history of spontaneous miscarriage and at least one live birth at term (n = 30). Staining was performed using PAS, anti-CD34 and anti-CD56 antibodies, using an avidin-biotin-peroxides technique. Analysis by means of light and transmission electron microscopy was employed. To determine the extent of remodelling of decidual vessels, a quantitative score was analysed using histological criteria of vascular transformation and then related to the number of CD56(+) dNKCs. In RM, dNKCs were distributed among decidual cells and around the vessels. They possessed numerous polyploidic protrusions on cell membranes crossing from one cell to another. The cells became more irregular and exhibited heterogeneous electron-dense granules in their cytoplasm compared to controls. The non-remodelling score and number of dNKCs were significantly increased in RM group (p < 0.001). The number of dNKCs was significantly correlated with the scores in both control (r = 0.491; p = 0.006) and RM (r = 0.852; p < 0.001) groups. It appears that dNKCs play a key role in impaired decidual artery remodelling that may be involved with early RM. This may be due to increased numbers of cells or impaired cellular interactions resulting from alterations to the ultrastructure.

A role for uric acid and the Nalp3 inflammasome in antiphospholipid antibody-induced IL-1β production by human first trimester trophoblast

Women with antiphospholipid syndrome (APS) are at risk of recurrent pregnancy loss and obstetrical disorders, such as preeclampsia and intrauterine growth restriction (IUGR). Antiphospholipid antibodies (aPL) directly target the placenta by binding beta₂-glycoprotein I (β₂GPI) expressed on the trophoblast. We recently demonstrated in human first trimester trophoblast cells that anti-β₂GPI antibodies (Abs) induce the secretion of IL-1β in a Toll-like receptor 4 (TLR4)-dependent manner. IL-1β secretion requires processing of pro-IL-1β and this is mediated by the inflammasome, a complex of Nalp3, apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1. The objective of this study was to determine if aPL induce IL-1β production in trophoblast via the inflammasome. Using a human first trimester trophoblast cell line, we demonstrated that a mouse anti-β₂GPI mAb and human polyclonal aPL-IgG induce IL-1β processing and secretion, which was partially blocked upon caspase-1 inhibition. Nalp3 and ASC knockdown also attenuated anti-β₂GPI Ab-induced IL-1β secretion. Furthermore, aPL stimulated the production of uric acid in a TLR4-dependent manner; and inhibition of uric acid prevented aPL-induced IL-1β production by the trophoblast. These findings demonstrate that aPL, via TLR4 activation, induce a uric acid response in human trophoblast, which in turn activates the Nalp3/ASC inflammasome leading to IL-1β processing and secretion. This novel mechanism may account for the inflammation at the maternal-fetal interface, which causes placental dysfunction and increases the risk of adverse pregnancy outcome in patients with APS.

Association of microparticles and preeclampsia

Preeclampsia (PE) is a syndrome characterized by poor placentation and endothelial dysfunction. The diagnosis for this syndrome is based in hypertension and proteinuria presented after the 20th week of pregnancy. Despite intensive research, PE is still one of the leading causes of maternal mortality, although reliable screening tests or effective treatments of this disease have yet to be proposed. Microparticles (MPs) are small vesicles released after cell activation or apoptosis, which contain membrane proteins that are characteristic of the original parent cell. MPs have been proven to play key role in thrombosis, inflammation, and angiogenesis, as well as to mediate cell-cell communication by transferring mRNAs and microRNA from the cell of origin to target cells. Placenta-derived syncytiotrophoblast MPs are one of the most increased MPs during PE and may play an important role in the pathogenesis of this syndrome. Therefore, a better overall understanding of the role of MPs in PE may be useful for new clinical diagnoses and therapeutic approaches.

Circulating microparticles in severe preeclampsia

The present study aimed to evaluate microparticles (MPs) from different sources in women with severe preeclampsia (PE) compared with normotensive pregnant women and non-pregnant women. This case-control study evaluated 28 pregnant women with severe PE, 30 normotensive pregnant women, and 29 non-pregnant women. MPs from neutrophils, endothelial cells, monocytes, platelets, leukocytes, erythrocytes, and syncytiotrophoblast were evaluated using flow cytometry. A higher total number of MPs were observed in women with severe PE compared with normotensive pregnant women and non-pregnant women (P=0.004 and P=0.001, respectively). MPs derived from erythrocytes were increased in women with severe PE compared with normotensive pregnant women (P=0.002). A trend towards association was observed between platelet count and the number of MPs derived from platelets (P=0.09) in severe PE group. A positive correlation was also found between the number of endothelial cell-derived MPs and the number of platelet-derived MPs, leukocyte-derived MPs, neutrophil-derived MPs, and lymphocyte-derived MPs (P<0.05) in severe PE pregnant women. MP counts can be increased in severe PE, and erythrocyte and endothelial cell-derived MPs seem to be associated to severe PE.

Innate immunity, decidual cells, and preeclampsia

Preeclampsia (PE) manifested by hypertension and proteinuria complicates 3% to 8% of pregnancies and is a leading cause of fetal-maternal morbidity and mortality worldwide. It may lead to intrauterine growth restriction, preterm delivery, and long-term sequelae in women and fetuses, and consequently cause socioeconomic burden to the affected families and society as a whole. Balanced immune responses are required for the maintenance of successful pregnancy. Although not a focus of most studies, decidual cells, the major resident cell type at the fetal-maternal interface, have been shown to modulate the local immune balance by interacting with other cell types, such as bone marrow derived-immune cells, endothelial cells, and invading extravillous trophoblasts. Accumulating evidence suggests that an imbalanced innate immunity, facilitated by decidual cells, plays an important role in the pathogenesis of PE. Thus, this review will discuss the role of innate immunity and the potential contribution of decidual cells in the pathogenesis of PE.

Extravillous trophoblast and decidual natural killer cells: a remodelling partnership

BACKGROUND

During pregnancy, maternal uterine spiral arteries (SAs) are remodelled from minimal-flow, high-resistance vessels into larger diameter vessels with low resistance and high flow. Fetal extravillous trophoblasts (EVT) have important roles in this process. Decidual natural killer cells (dNK cells) are the major maternal immune component of the decidua and accumulate around SAs before trophoblast invasion. A role for dNK cells in vessel remodelling is beginning to be elucidated. This review examines the overlapping and dissimilar mechanisms used by EVT and dNK cells in this process and how this may mirror another example of tissue remodelling, namely cancer development.

METHODS

The published literature was searched using Pubmed focusing on EVT, dNK cells and SA remodelling. Additional papers discussing cancer development are also included.

RESULTS

Similarities exist between actions carried out by dNK cells and EVT. Both interact with vascular cells lining the SA, as well as with each other, to promote transformation of the SA. EVT differentiation has previously been likened to the epithelial-mesenchymal transition in cancer cells, and we discuss how dNK-EVT interactions at the maternal-fetal interface can also be compared with the roles of immune cells in cancer.

CONCLUSIONS

The combined role that dNK cells and EVT play in SA remodelling suggests that these interactions could be described as a partnership. The investigation of pregnancy as a multicellular system involving both fetal and maternal components, as well as comparisons to similar examples of tissue remodelling, will further identify the key mechanisms in SA remodelling that are required for a successful pregnancy.

Preeclampsia, hypoxia, thrombosis, and inflammation

Reductions in uteroplacental flow initiate a cascade of molecular effects leading to hypoxia, thrombosis, inflammation, and endothelial cell dysfunction resulting in untoward pregnancy outcomes. In this review, we detail these effects and their relationship to preeclampsia (PE) and intrauterine growth restriction (IUGR).

Do uterine natural killer (uNK) cells contribute to female reproductive disorders?

The most abundant immune cells in the uterine decidua around the time of implantation and early placental development are the uterine natural killer (uNK) cells. Altered numbers of uNK cells have been associated with several human reproductive disorders, including recurrent miscarriage, recurrent implantation failure, uterine fibroids, sporadic miscarriage, fetal growth restriction and preeclampsia. Understanding of the function of uNK cells in non-pregnant and pregnant endometrium is now increasing; the potential contribution of altered numbers and function of uNK cells to reproductive disorders is the focus of this review.

Persistence of decidual NK cells and KIR genotypes in healthy pregnant and preeclamptic women: a case-control study in the third trimester of gestation

BACKGROUND

Natural Killer (NK) cells are the most abundant lymphocytes in the decidua during early gestation. The interactions of NK cells with the extravillous cytotrophoblast have been associated with a normal spiral artery remodeling process, an essential event for a successful pregnancy. Recent data indicate that alterations in the amount of decidual NK (dNK) cells contribute to the development of preeclampsia (PE). Moreover, genetic studies suggest that Killer Immunoglobulin-like Receptors (KIR) expressed in dNK cells influence the susceptibility to PE. Although dNK cells have been well characterized during early pregnancy, they have been scarcely studied in the third trimester of gestation. The aim of this work was to characterize dNK cells at the last trimester of gestation and to analyze the KIR genotype of healthy and PE women.

METHODS

Decidual samples were obtained during Caesarean section from control (n = 10) and PE (n = 9) women. Flow cytometric analysis of CD3, CD56, CD16 and CD9 was used to characterize and quantify dNK cells in both groups. Cell surface markers from decidual leukocytes were compared with PBMC from healthy donors.KIR genotyping was performed in genomic DNA (control, n = 86; PE, n = 90) using PCR-SSP.

RESULTS

The results indicate that dNK cells persist throughout pregnancy. They represented 20% of total leukocytes in control and PE groups, and they expressed the same cell surface markers (CD3-, CD56+, CD16- and CD9+) as dNK in the first trimester of gestation. There were no significant differences in the percentage of dNK cells between control and PE groups. The analysis of KIR gene frequencies and genotypes was not statistically different between control and PE groups. The ratio of activating to inhibitory genes indicated that the overall inhibitory balance (0.2-0.5) was more frequent in the PE group (control, 31.3% vs PE, 45.5%), and the activating balance (0.6-1.1) was more frequent in the control group (control, 68.6% vs PE, 54.4%). However this difference was not significant.

CONCLUSION

We demonstrated the persistence of dNK cells in PE and control women at the third trimester of pregnancy; these dNK cells had a similar phenotype to those found during early pregnancy. The predominance of a KIR inhibitory balance in the PE group could be associated to the physiopathology of PE.

Pre-eclampsia: fitting together the placental, immune and cardiovascular pieces

The success of pregnancy is a result of countless ongoing interactions between the placenta and the maternal immune and cardiovascular systems. Pre-eclampsia is a serious pregnancy complication that arises from multiple potential aberrations in these systems. The pathophysiology of pre-eclampsia is established in the first trimester of pregnancy, when a range of deficiencies in placentation affect the key process of spiral artery remodelling. As pregnancy progresses to the third trimester, inadequate spiral artery remodelling along with multiple haemodynamic, placental and maternal factors converge to activate the maternal immune and cardiovascular systems, events which may in part result from increased shedding of placental debris. As we understand more about the pathophysiology of pre-eclampsia, it is becoming clear that the development of early- and late-onset pre-eclampsia, as well as intrauterine growth restriction (IUGR), does not necessarily arise from the same underlying pathology.