NK cells and trophoblasts: partners in pregnancy

The influence of the oral microbiota in full-term pregnant women on immune regulation during pregnancy

BACKGROUND

This study aims to conduct a preliminary exploration of the correlation between the oral microbiota of full-term pregnant women and both local placental immunity and the systemic immune system of the mother.

METHODS

A total of 26 pregnant women participated in this study, with samples collected from oral swabs, placental tissue, and peripheral venous blood. High-throughput sequencing was used to examine the oral microbial community. Flow cytometry was employed to assess immune cells in placental tissue and peripheral venous blood. ELISA and Luminex liquid bead chip technology were utilized to detect cytokines in both placental tissue and peripheral venous blood.

RESULTS

In placental tissue, The oral microbial community is primarily negatively correlated with placental CD3+CD4+CD8+T cells and positively correlated with placental IL-5. In the peripheral blood, The oral microbial community is primarily positively correlated with maternal systemic immune parameters, including CD3+CD4+ T cells and the CD4+/CD8+ ratio, as well as positively correlated with peripheral IL-18.

CONCLUSIONS

The oral microbiota of full-term pregnant women participates in the regulatory function of the maternal immune system. Meanwhile, the oral microbial community may also be an important factor mediating local immune regulation in the placenta.

Preeclampsia epidemiology(ies) and pathophysiology(ies)

Preeclampsia/eclampsia was first described 2000 years ago. Concepts guiding diagnosis have changed over time making longitudinal studies challenging. Similarly, concepts of pathophysiology have evolved from eclampsia as a pregnancy seizure disorder to preeclampsia as a hypertensive and renal disorder to our current concept of a preeclampsia as a pregnancy specific, multisystemic inflammatory disorder. Although preeclampsia is pregnancy specific and many pathophysiologic findings begin to resolve with delivery, its impact extends beyond pregnancy. The risk of cardiovascular and neurological disease is increased after pregnancy in women who have had preeclampsia. The disorder is not a disease, but a syndrome and emerging data indicate multiple pathways to the syndrome. It is likely that our failure to have a major impact on prediction and prevention despite a large increase in understanding is due to the existence of multiple subtypes of preeclampsia. This concept should guide future research.

Deciphering the Epigenetic Landscape: Placental Development and Its Role in Pregnancy Outcomes

The placenta stands out as a unique, transitory, and multifaceted organ, essential to the optimal growth and maturation of the fetus. Functioning as a vital nexus between the maternal and fetal circulatory systems, it oversees the critical exchange of nutrients and waste. This exchange is facilitated by placental cells, known as trophoblasts, which adeptly invade and remodel uterine blood vessels. Deviations in placental development underpin a slew of pregnancy complications, notably fetal growth restriction (FGR), preeclampsia (PE), recurrent spontaneous abortions (RSA), and preterm birth. Central to placental function and development is epigenetic regulation. Despite its importance, the intricate mechanisms by which epigenetics influence the placenta are not entirely elucidated. Recently, the scientific community has turned its focus to parsing out the epigenetic alterations during placental development, such as variations in promoter DNA methylation, genomic imprints, and shifts in non-coding RNA expression. By establishing correlations between epigenetic shifts in the placenta and pregnancy complications, researchers are unearthing invaluable insights into the biology and pathophysiology of these conditions. This review seeks to synthesize the latest findings on placental epigenetic regulation, spotlighting its crucial role in shaping fetal growth trajectories and development. Through this lens, we underscore the overarching significance of the placenta in the larger narrative of gestational health.

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.

Relative expression of receptors in uterine natural killer cells compared to peripheral blood natural killer cells

One would expect maternal immune cells to attack the invading trophoblast as the placenta is semi-allogenic. However, they appear to cooperate with the trophoblast in disrupting the arterial wall which has been determined in several studies. uNK cells are a particular type of immune cell that appears to play a role in pregnancy. As in pregnancy, the key contributors to trophoblast invasion appear to be a unique combination of genes, which appear to regulate multiple components of the interactions between placental and maternal cells, called HLA class 1b genes. The HLA class 1b genes have few alleles, which makes them unlikely to be recognized as foreign by the maternal cells. The low polymorphic properties of these particular HLAs may aid trophoblasts in actively avoiding immune attacks. This review gives a complete description of the mechanisms of interaction between HLAs and maternal uNK cells in humans.

Natural killer cell profiles in recurrent pregnancy loss: Increased expression and positive associations with TACTILE and LILRB1

PROBLEM

NK cells are important for healthy pregnancy and aberrant phenotypes or effector functions have been associated with RPL. We compared expression of a broad panel of NK cell receptors, including immune checkpoint receptors, and investigated their clinical association with RPL as this might improve patient stratification and prediction of RPL.

METHOD OF STUDY

Peripheral blood mononuclear cells were isolated from 52 women with RPL and from 2 women with an uncomplicated pregnancy for flowcytometric analysis and plasma was used to determine anti-CMV IgG antibodies.

RESULTS

Between RPL and controls, we observed no difference in frequencies of T-, NKT or NK cells, in CD56dimCD16+ or CD56brightCD16- NK cell subsets or in the expression of KIRs, NKG2A, NKG2C, NKG2D, NKp30, NKp44, NKp46 or DNAM1. NK cells from women with RPL had a higher expression of LILRB1 and TACTILE and this was associated with the number of losses. The immune checkpoint receptors PD1, TIM3 and LAG3 were not expressed on peripheral blood NK cells. In RPL patients, there was a large variation in NKG2C expression and higher levels could be explained by CMV seropositivity.

CONCLUSION

Our study identified LILRB1 and TACTILE as NK cell receptors associated with RPL. Moreover, we provide first support for the potential role of CMV in RPL via its impact on the NK cell compartment. Thereby our study could guide future studies to confirm the clinical association of LILRB1, TACTILE and NKG2C with RPL in a larger cohort and to explore their functional relevance in reproductive success.

Number and function of uterine natural killer cells in recurrent miscarriage and implantation failure: a systematic review and meta-analysis

BACKGROUND

Uterine natural killer cells (uNK) are the most abundant lymphocytes found in the decidua during implantation and in first trimester pregnancy. They are important for early placental development, especially trophoblast invasion and transformation of the spiral arteries. However, inappropriate uNK function has been implicated in reproductive failure, such as recurrent miscarriage (RM) or recurrent implantation failure (RIF). Previous studies have mainly focussed on peripheral NK cells (pNK), despite the well-documented differences in pNK and uNK phenotype and function. In recent years, there has been an explosion of studies conducted on uNK, providing a more suitable representation of the immune environment at the maternal-foetal interface. Here, we summarize the evidence from studies published on uNK in women with RM/RIF compared with controls.

OBJECTIVE AND RATIONALE

The objectives of this systematic review and meta-analysis are to evaluate: differences in uNK level in women with RM/RIF compared with controls; pregnancy outcome in women with RM/RIF stratified by high and normal uNK levels; correlation between uNK and pNK in women with RM/RIF; and differences in uNK activity in women with RM/RIF compared with controls.

SEARCH METHODS

MEDLINE, EMBASE, Web of Science and Cochrane Trials Registry were searched from inception up to December 2020 and studies were selected in accordance with PRISMA guidelines. Meta-analyses were performed for uNK level, pregnancy outcome and uNK/pNK correlation. Narrative synthesis was conducted for uNK activity. Risk of bias was assessed by ROBINS-I and publication bias by Egger's test.

OUTCOMES

Our initial search yielded 4636 articles, of which 60 articles were included in our systematic review. Meta-analysis of CD56+ uNK level in women with RM compared with controls showed significantly higher levels in women with RM in subgroup analysis of endometrial samples (standardized mean difference (SMD) 0.49, CI 0.08, 0.90; P = 0.02; I2 88%; 1100 women). Meta-analysis of CD56+ uNK level in endometrium of women with RIF compared with controls showed significantly higher levels in women with RIF (SMD 0.49, CI 0.01, 0.98; P = 0.046; I2 84%; 604 women). There was no difference in pregnancy outcome in women with RM/RIF stratified by uNK level, and no significant correlation between pNK and uNK levels in women with RM/RIF. There was wide variation in studies conducted on uNK activity, which can be broadly divided into regulation and receptors, uNK cytotoxicity, cytokine secretion and effect of uNK on angiogenesis. These studies were largely equivocal in their results on cytokine secretion, but most studies found lower expression of inhibitory receptors and increased expression of angiogenic factors in women with RM.

WIDER IMPLICATIONS

The observation of significantly increased uNK level in endometrium of women with RM and RIF may point to an underlying disturbance of the immune milieu culminating in implantation and/or placentation failure. Further research is warranted to elucidate the underlying pathophysiology. The evidence for measuring pNK as an indicator of uNK behaviour is sparse, and of limited clinical use. Measurement of uNK level/activity may be more useful as a diagnostic tool, however, a standardized reference range must be established before this can be of clinical use.

Dynamic Changes in Uterine NK Cell Subset Frequency and Function Over the Menstrual Cycle and Pregnancy

Uterine natural killer cells (uNK) play an important role in promoting successful pregnancy by regulating trophoblast invasion and spiral artery remodelling in the first trimester. Recently, single-cell RNA sequencing (scRNAseq) on first-trimester decidua showed that uNK can be divided into three subsets, which may have different roles in pregnancy. Here we present an integration of previously published scRNAseq datasets, together with novel flow cytometry data to interrogate the frequency, phenotype, and function of uNK1–3 in seven stages of the reproductive cycle (menstrual, proliferative, secretory phases of the menstrual cycle; first, second, and third trimester; and postpartum). We found that uNK1 and uNK2 peak in the first trimester, but by the third trimester, the majority of uNK are uNK3. All three subsets are most able to degranulate and produce cytokines during the secretory phase of the menstrual cycle and express KIR2D molecules, which allow them to interact with HLA-C expressed by placental extravillous trophoblast cells, at the highest frequency during the first trimester. Taken together, our findings suggest that uNK are particularly active and able to interact with placental cells at the time of implantation and that uNK1 and uNK2 may be particularly involved in these processes. Our findings are the first to establish how uNK frequency and function change dynamically across the healthy reproductive cycle. This serves as a platform from which the relationship between uNK function and impaired implantation and placentation can be investigated. This will have important implications for the study of subfertility, recurrent miscarriage, pre-eclampsia, and pre-term labour.

Endometrial HLA-F expression is influenced by genotypes and correlates differently with immune cell infiltration in IVF and recurrent implantation failure patients

STUDY QUESTION

Is human leukocyte antigen (HLA)-F protein expressed in mid-secretory endometrium, and are its expression levels influenced by HLA-F gene polymorphisms and correlated with the abundance of uterine natural killer (uNK) cells and anti-inflammatory M2 macrophages?

SUMMARY ANSWER

HLA-F protein is expressed in mid-secretory endometrium, and levels are correlated with immune cell infiltration, plasma progesterone concentrations and HLA-F single-nucleotide polymorphisms (SNPs), however, women experiencing recurrent implantation failure (RIF) show differences when compared to women attending their first IVF treatment.

WHAT IS KNOWN ALREADY

The immunomodulatory HLA class Ib molecules HLA-G and HLA-F are expressed on the extravillous trophoblast cells and interact with receptors on maternal immune cells. Little is known regarding HLA-F expression in endometrial stroma and HLA-F function; furthermore, HLA-F and HLA-G SNP genotypes and haplotypes have been correlated with differences in time-to-pregnancy.

STUDY DESIGN, SIZE, DURATION

Primary endometrial stromal cell (ESC) cultures (n = 5) were established from endometrial biopsies from women attending IVF treatment at a fertility clinic. Basic HLA-F and HLA-G protein expression by the ESCs were investigated. A prospective controlled cohort study was performed including 85 women with a history of RIF and 36 control women beginning their first fertility treatment and with no history of RIF. In some analyses, the RIF group was divided into unknown cause, male infertility, female infertility, and both female and male infertility. Endometrial biopsies and blood samples were obtained the day equivalent to embryo transfer in a hormone-substituted cycle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

HLA protein expression by ESCs was characterized using flow cytometry and western blot. In the cohort study, the specific immune markers HLA-F and HLA-G, CD56 and CD16 (NK cells), CD163 (M2 macrophages), FOXP3 (regulatory T cells) and CD138 (plasma cells) were analysed by immunohistochemistry and a digital image analysis system in endometrial biopsies. Endometrial receptivity was assessed by an endometrial receptivity array test (the ERA® test). Endometrial biopsies were examined according to modified Noyes' criteria. SNPs at the HLA-F gene and HLA-G haplotypes were determined.

MAIN RESULTS AND THE ROLE OF CHANCE

HLA-F protein is expressed in the endometrium at the time of implantation. Furthermore, the HLA-F protein levels were different according to the womeńs HLA-F SNP genotypes and diplotypes, which have previously been correlated with differences in time-to-pregnancy. Endometrial HLA-F was positively correlated with anti-inflammatory CD163+ M2 macrophage infiltration and CD56+ uNK cell abundance for the entire cohort. However, this was not the case for CD56+ in the female infertility RIF subgroup. HLA-F levels in the endometrial stroma were negatively correlated with plasma progesterone concentrations in the RIF subgroup with known female infertility. Conversely, HLA-F and progesterone were positively correlated in the RIF subgroup with infertility of the male partner and no infertility diagnosis of the woman indicating interconnections between progesterone, HLA-F and immune cell infiltration. Glandular sHLA-G expression was also positively correlated with uNK cell abundance in the RIF subgroup with no female infertility but negatively correlated in the RIF subgroup with a female infertility diagnosis.

LARGE SCALE DATA

Immunohistochemistry analyses of endometrial biopsies and DNA sequencing of HLA genes. Data will be shared upon reasonable request to the corresponding author.

LIMITATIONS, REASONS FOR CAUTION

The control group of women attending their first IVF treatment had an anticipated good prognosis but was not proven fertile. A significant age difference between the RIF group and the IVF group reflects the longer treatment period for women with a history of RIF. The standardization of hormonal endometrial preparation, which allowed consistent timing of endometrial and blood sampling, might be a strength because a more uniform hormonal background may more clearly show an influence on the immune marker profile and HLA class Ib levels in the endometrium by other factors, for example genetic polymorphisms. However, the immune marker profile might be different during a normal cycle.

WIDER IMPLICATIONS OF THE FINDINGS

The findings further highlight the importance of HLA-F and HLA-G at the implantation site and in early pregnancy for pregnancy success. Diagnostic measures and modulation of the complex interactions between HLA class Ib molecules, maternal immune cells and hormonal factors may have potential to improve fertility treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Region Zealand Health Sciences Research Foundation and the Zealand University Hospital through the ReproHealth Research Consortium ZUH. The authors declared there are no conflicts of interest.

HLA-G genetic diversity and evolutive aspects in worldwide populations

HLA-G is a promiscuous immune checkpoint molecule. The HLA-G gene presents substantial nucleotide variability in its regulatory regions. However, it encodes a limited number of proteins compared to classical HLA class I genes. We characterized the HLA-G genetic variability in 4640 individuals from 88 different population samples across the globe by using a state-of-the-art method to characterize polymorphisms and haplotypes from high-coverage next-generation sequencing data. We also provide insights regarding the HLA-G genetic diversity and a resource for future studies evaluating HLA-G polymorphisms in different populations and association studies. Despite the great haplotype variability, we demonstrated that: (1) most of the HLA-G polymorphisms are in introns and regulatory sequences, and these are the sites with evidence of balancing selection, (2) linkage disequilibrium is high throughout the gene, extending up to HLA-A, (3) there are few proteins frequently observed in worldwide populations, with lack of variation in residues associated with major HLA-G biological properties (dimer formation, interaction with leukocyte receptors). These observations corroborate the role of HLA-G as an immune checkpoint molecule rather than as an antigen-presenting molecule. Understanding HLA-G variability across populations is relevant for disease association and functional studies.

ERAP, KIR, and HLA-C Profile in Recurrent Implantation Failure

The mother’s uterine immune system is dominated by uterine natural killer (NK) cells during the first trimester of pregnancy. These cells express killer cell immunoglobulin-like receptors (KIRs) of inhibitory or activating function. Invading extravillous trophoblast cells express HLA-C molecules, and both maternal and paternal HLA-C allotypes are presented to KIRs. Endoplasmic reticulum aminopeptidase 1 (ERAP1) and 2 (ERAP2) shape the HLA class I immunopeptidome. The ERAPs remove N-terminal residues from antigenic precursor peptides and generate optimal-length peptides to fit into the HLA class I groove. The inability to form the correct HLA class I complexes with the appropriate peptides may result in a lack of immune response by NK cells. The aim of this study was to investigate the role of ERAP1 and ERAP2 polymorphisms in the context of KIR and HLA-C genes in recurrent implantation failure (RIF). In addition, for the first time, we showed the results of ERAP1 and ERAP2 secretion into the peripheral blood of patients and fertile women. We tested a total of 881 women. Four hundred ninety-six females were patients who, together with their partners, participated in in vitro fertilization (IVF). A group of 385 fertile women constituted the control group. Women positive for KIR genes in the Tel AA region and HLA-C2C2 were more prevalent in the RIF group than in fertile women (p/p_corr. = 0.004/0.012, OR = 2.321). Of the ERAP polymorphisms studied, two of them (rs26653 and rs26618) appear to affect RIF susceptibility in HLA-C2-positive patients. Moreover, fertile women who gave birth in the past secreted significantly more ERAP1 than IVF women and control pregnant women (p < 0.0001 and p = 0.0005, respectively). In the case of ERAP2, the opposite result was observed; i.e., fertile women secreted far less ERAP2 than IVF patients (p = 0.0098). Patients who became pregnant after in vitro fertilization embryo transfer (IVF-ET) released far less ERAP2 than patients who miscarried (p = 0.0032). Receiver operating characteristic (ROC) analyses indicate a value of about 2.9 ng/ml of ERAP2 as a point of differentiation between patients who miscarried and those who gave birth to a healthy child. Our study indicates that both ERAP1 and ERAP2 may be involved in processes related to reproduction.

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.

Plasma Endocan Levels in Early and Late-Onset Preeclampsia

Preeclampsia (PE) may represent an inflammatory process. Endocan (ESM-1) is a marker of endothelial inflammation. We compared plasma endocan levels between PE and control groups and between early and late-onset PE. Study design: Maternal plasma endocan levels were measured in 41 preeclampsia (PE) pregnancies - 25 early-onset (<34 weeks); 16 late-onset (≥34 weeks), and 37 non-complicated pregnancies (22 matched with early-onset PE, 15 with late onset). Results: There was no significant differences between plasma endocan levels of patients with PE and control group (468.8(IQR: 169.7)ng/L vs 462.4(IQR: 321.1)ng/L, p > 0.05), between early and late-onset PE (458.8(221.8)ng/L vs 469.8(122.6)ng/L, p > 0.05), between early-onset PE and corresponding control group (458.8(221.8)ng/L vs 506.2(1481.9)ng/L, p > 0.05), or late-onset PE and corresponding control group (469.8(122.6)ng/L vs 451.0(85.1)ng/L, p > 0.05). Conclusion: There was no significant difference between endocan levels of early or late-onset PE compared with their corresponding control groups, nor between early and late-onset preeclampsia groups.

Prospective longitudinal cohort study of uterine arteries Doppler in singleton pregnancies obtained by IVF/ICSI with oocyte donation or natural conception

STUDY QUESTION

Do uterine arteries Doppler studies show different pulsatility index (UtA-PI) measurements in IVF/ICSI pregnancies with oocyte donation (OD) as compared to natural conceptions?

SUMMARY ANSWER

In IVF/ICSI pregnancies with OD, UtA-PI is reduced by an average of about 40% as compared to pregnancies with natural conception.

WHAT IS KNOWN ALREADY

OD pregnancies present worse pregnancy outcomes as compared to natural conception, particularly for increased incidence of pre-eclampsia (PE). Recent evidence shows that IVF/ICSI pregnancies with frozen blastocyst transfer also present higher prevalence of PE and 15% lower UtA-PI as compared to pregnancies after fresh blastocyst transfers.

STUDY DESIGN, SIZE, DURATION

Prospective, longitudinal matched cohort study performed in the Fetal Medicine and Obstetric Departments of San Raffaele Hospital in Milan, between 2013 and 2018. The analysis is based on 584 Doppler observations collected from 296 women with different method of conception (OD n = 122; natural conception n = 174).

PARTICIPANTS/MATERIALS, SETTING, METHODS

IVF/ICSI viable singleton pregnancies with OD and natural conception control pregnancies matched for BMI and smoking, performing repeated UtA-PI measurements at 11-34 weeks. Miscarriages, abnormalities, twins, significant maternal diseases and other types of ARTs were excluded. Log mean left-right UtA-PI was used for analysis with linear mixed model (LMM) and correction for significant confounders. Pregnancy outcome was also analyzed.

MAIN RESULTS AND THE ROLE OF CHANCE

Participants after OD were older and more frequently nulliparous (mean age: OD 43.4, 95% CI from 42.3 to 44.6; natural conception 35.1, 95% CI from 34.5 to 35.7; P-value < 0.001; nulliparous: OD 96.6%; natural conception 56.2%; P-value < 0.001). Mean pulsatility index was lower in OD (UtA-PI: natural conception 1.22; 95% CI from 1.11 to 1.28; OD 1.04; 95% CI from 0.96 to 1.12; P-value < 0.001). A significant effect of parity, gestational age (GA) modeled with a cubic polynomial and BMI was described in the LMM. The mean Log UtA-PI was on average 37% lower in OD as compared to natural conception pregnancies at LMM (P-value < 0.001). We also found a significant interaction between longitudinal UtA-PI Doppler and GA. Therefore, at 11 weeks' gestation the Log UtA-PI was 42% lower and, at 34 weeks, the differences reduced to 32%. GA at delivery and birth weight were statistically lower in OD group; however, birthweight centile was not statistically different. Preeclampsia was 11-fold more common in the OD group (0.6% and 6.6%, P-value = 0.003). No other significant difference in pregnancy outcome was shown in the study groups (gestational diabetes mellitus, small or large for GA).

LIMITATIONS, REASONS FOR CAUTION

It was not possible to properly match for maternal age and to blind the assessment given the major differences between cohorts; however, we did not find significant within-groups effects related to maternal age. Future research is needed to reassess outcomes and correct them for maternal characteristics (e.g. cardiovascular function).

WIDER IMPLICATIONS OF THE FINDINGS

This finding reproduces our previous discovery of lower UtA-PI in frozen as compared to fresh blastocyst transfer. The vast majority of OD is obtained by the use of cryopreservation. We speculate that increased uterine perfusion may be the physiological response to compensate dysfunctions both in the mother and in the placenta.

STUDY FUNDING/COMPETING INTEREST(S)

This is a non-funded study. The authors do not declare competing interest.

TRIAL REGISTRATION NUMBER

N/A.

The Interplay between CD27dull and CD27bright B Cells Ensures the Flexibility, Stability, and Resilience of Human B Cell Memory

Memory B cells (MBCs) epitomize the adaptation of the immune system to the environment. We identify two MBC subsets in peripheral blood, CD27^dull and CD27^bright MBCs, whose frequency changes with age. Heavy chain variable region (VH) usage, somatic mutation frequency replacement-to-silent ratio, and CDR3 property changes, reflecting consecutive selection of highly antigen-specific, low cross-reactive antibody variants, all demonstrate that CD27^dull and CD27^bright MBCs represent sequential MBC developmental stages, and stringent antigen-driven pressure selects CD27^dull into the CD27^bright MBC pool. Dynamics of human MBCs are exploited in pregnancy, when 50% of maternal MBCs are lost and CD27^dull MBCs transit to the more differentiated CD27^bright stage. In the postpartum period, the maternal MBC pool is replenished by the expansion of persistent CD27^dull clones. Thus, the stability and flexibility of human B cell memory is ensured by CD27^dull MBCs that expand and differentiate in response to change.

Transcriptomic Profiling of Human Placenta in Gestational Diabetes Mellitus at the Single-Cell Level

Gestational diabetes mellitus (GDM) is associated with an increased risk of adverse pregnancy outcomes. Increasing evidence shows that placentation defects may play important roles in GDM. However, our understanding of the human placenta remains limited. In this study, we generated a comprehensive transcriptomic profile of cellular signatures and transcriptomes in the human placenta in GDM using single-cell RNA sequencing (scRNA-seq), constructed a comprehensive cell atlas, and identified cell subtypes and subtype-specific marker genes. In addition, we investigated the placental cellular function and intercellular interactions in GDM. These findings help to elucidate the molecular mechanisms of GDM, and may facilitate the development of new approaches to GDM treatment and prevention.

UDP-glucose, a cellular danger signal, and nucleotide receptor P2Y14 enhance the invasion of human extravillous trophoblast cells

INTRODUCTION

P2Y14, one of the P2Y purinergic G-protein coupled receptors, is expressed in a variety of cells and tissues. Its ligand, UDP-glucose (UDPG), is released from damaged and stress-stimulated cells and acts as a danger signal via P2Y14. Thus, P2Y14 plays an important role in immunological defense systems. Here, we aimed to elucidate the expression, localization, and role of P2Y14 in human trophoblasts and the placenta.

METHODS

Human chorionic villus and placental tissues were subjected to immunostaining for P2Y14 protein and an extravillous trophoblast (EVT) marker, HLA-G. We examined the expression of P2Y14 and the effect of UDPG on cell proliferation and invasion in an EVT cell line, HTR-8/SVneo, using an MTS assay and a Transwell assay, respectively. We tested the effect of UDPG on cell invasion in P2Y14-underexpressing HTR-8/SVneo clones established by the lentiviral introduction of shRNA for P2RY14 mRNA.

RESULTS

Immunostaining revealed that P2Y14 was exclusively expressed by EVTs. P2RY14 mRNA and P2Y14 protein were expressed in HTR-8/SVneo cells. UDPG did not affect cell proliferation but it did enhance invasion. Inhibition of P2Y14 and decreasing the expression of P2Y14 suppressed UDPG-mediated invasive activity.

CONCLUSIONS

These results showed that EVT selectively expressed P2Y14 and that P2Y14 was positively involved in UDPG-enhanced EVT invasion. It suggests the possible existence of a danger signal-mediated physiological system at the fetomaternal interface where UDPG released from maternal tissues through destruction by EVT invasion may accelerate EVT invasion, allowing EVTs to undergo successful placentation and vascular remodeling.

Parental human leukocyte antigen-C allotypes are predictive of live birth rate and risk of poor placentation in assisted reproductive treatment

OBJECTIVE

To study the pregnancy, miscarriages, and live birth rates (LBRs) according to maternal killer cell immunoglobulin-like receptor (KIR) genes expressed by uterine natural killer cells and paternal or oocyte donor human leukocyte antigen-C (HLA-C) genes expressed by trophoblast cells in patients with recurrent reproductive failure.

DESIGN

Prospective observational cohort study.

SETTING

Private infertility center.

PATIENT(S)

Participants included 204 women with recurrent miscarriage or recurrent implantation failure.

INTERVENTION(S)

The KIR and HLA-C genotypes of all women and HLA-C of their partners, gamete donors, miscarriage tissue, and babies were analyzed.

MAIN OUTCOME MEASURE(S)

All clinical variables (pregnancy, miscarriage, and LBRs) were analyzed and categorized based on KIR, oocyte origin, and single embryo transfer (SET)/double embryo transfer (DET).

RESULT(S)

A higher miscarriage rate was observed after DETs in KIR AA mothers (47.8% egg donation and 37.5% in vitro fertilization [IVF]) compared with KIR AB (10.5% egg donation and 12.5% IVF) or KIR BB (6.7% egg donation and 0% IVF). A significantly decreased LBR was observed after DETs with oocyte donation in KIR AA patients (4.3%) compared with KIR AB (26.3%) or BB (46.7%). The LBR decreased significantly as the fetal HLA-C2 load increased in KIR AA women.

CONCLUSION(S)

Elective SET improves the reproductive outcomes compared with DET. An increased embryo HLA-C2 load has a negative impact on the LBR in KIR AA patients. The selection of HLA-C1 over HLA-C2 donors could have a positive impact on the LBR in KIR AA patients.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04052438.

Role of ROS/RNS in Preeclampsia: Are Connexins the Missing Piece?

Preeclampsia is a pregnancy complication that appears after 20 weeks of gestation and is characterized by hypertension and proteinuria, affecting both mother and offspring. The cellular and molecular mechanisms that cause the development of preeclampsia are poorly understood. An important feature of preeclampsia is an increase in oxygen and nitrogen derived free radicals (reactive oxygen species/reactive nitrogen species (ROS/RNS), which seem to be central players setting the development and progression of preeclampsia. Cell-to-cell communication may be disrupted as well. Connexins (Cxs), a family of transmembrane proteins that form hemichannels and gap junction channels (GJCs), are essential in paracrine and autocrine cell communication, allowing the movement of signaling molecules between cells as well as between the cytoplasm and the extracellular media. GJCs and hemichannels are fundamental for communication between endothelial and smooth muscle cells and, therefore, in the control of vascular contraction and relaxation. In systemic vasculature, the activity of GJCs and hemichannels is modulated by ROS and RNS. Cxs participate in the development of the placenta and are expressed in placental vasculature. However, it is unknown whether Cxs are modulated by ROS/RNS in the placenta, or whether this potential modulation contributes to the pathogenesis of preeclampsia. Our review addresses the possible role of Cxs in preeclampsia, and the plausible modulation of Cxs-formed channels by ROS and RNS. We suggest these factors may contribute to the development of preeclampsia.

Oleic acid stimulation of motility of human extravillous trophoblast cells is mediated by stearoyl-CoA desaturase-1 activity

STUDY QUESTION

Do fatty acids regulate development and motility of human extravillous trophoblast cells (EVTs)?

SUMMARY ANSWER

Oleic acid is a promising lipid molecule that has beneficial effects on motility and development of human EVTs.

WHAT IS KNOWN ALREADY

Fatty acid uptake into trophoblast cells is important for maintaining cellular events during pregnancy, but the molecular mechanisms of action of various fatty acids, including trans fatty acids, saturated fatty acids and monounsaturated fatty acids, in EVT cell lines are not clear.

STUDY DESIGN, SIZE, DURATION

Effects of oleic acid, elaidic acid, palmitic acid and stearic acid on HTR8/SVneo cells were assessed in diverse assays in a dose- and time-dependent manner.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Effects of fatty acids on cell proliferation, migration, invasion and apoptosis (Annexin V expression, propidium iodide staining, TUNEL and invasion assays) of HTR8/SVneo cells were determined. Signal transduction pathways in HTR8/SVneo cells in response to fatty acids were determined by Western blot analyses. Regulation of fatty acids on oxidative conditions in EVTs were determined and validated by measurement of production of cellular reactive oxygen species, intracellular concentrations of free Ca2+and lipid peroxidation assays.

MAIN RESULTS AND THE ROLE OF CHANCE

In present study, we confirmed different effects of oleic acid and elaidic acid on migration, invasion, proliferation and apoptosis of the EVT cell line, HTR8/SVneo. We also investigated stearoyl-CoA desaturase-1 (SCD1) to determine if its activity contributed to oleic acid-induced migration of HTR8/SVneo cells. Next, we analyzed cell signaling molecules mediated by oleic acid and elaidic acid treatment, including MAPK and PI3K/AKT pathways in HTR8/SVneo cells. We further established whether selective inhibition of signaling molecules altered the ability of fatty acids to cause changes in migration and proliferation of HTR8/SVneo cells. Last, we examined the regulatory effects of oleic acid and SCD1 on oxidative stress in HTR8/SVneo cells.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The lack of in vivo animal studies is a major limitation of this research. Effectiveness of oleic acid to stimulate migration of human EVT cells requires further investigation.

WIDER IMPLICATIONS OF THE FINDINGS

Our results suggest that oleic acid can play an important role in promoting invasion of human EVT cell lines while both trans fatty acids and saturated fatty acids are not conducive to normal placentation. This may have implications for the prevention of pre-eclampsia and intrauterine growth restriction.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (No. HI15C0810) awarded to G.S. and (No. HI17C0929) awarded to W.L. There are no conflicts of interest.

Geometric and hemodynamic characterization of uterine spiral arteries: The concept of resistance reserve

BACKGROUND

The coiled geometry of spiral arteries in the human uteroplacental circulation is a hemodynamic enigma because of added length of a spiral artery compared with that of a straight artery, as well as added complexity of the flow within the vessel because of the coiling curvature.

METHODS

We examined the geometric and hemodynamic characteristics of mathematically defined helical and spiral arteries and compared these with the corresponding characteristics of a straight artery traversing the same depth of tissue, with the aim of gaining some insight into the possible role of spiral geometry in uteroplacental perfusion.

RESULTS

The results indicate that the added length of a spiral artery provides the uteroplacental circulation with a reserve of high resistance to flow. The effect of coiling geometry on the flow within the artery is the development of churning vortices in planes normal (perpendicular) to the main flow direction.

CONCLUSIONS

In the early stages of pregnancy the reserve of high resistance is intact, thus keeping blood supply low. As pregnancy progresses, the reserve is gradually purged by trophoblast invasion and transformation of the distal portion of the spiral artery into an open funnel, thus providing the required high blood supply. The development of churning vortices within the spiral artery support earlier suggestions in the literature that the "spurts" of maternal blood emerging from these arteries may play a role in shaping the anatomy of the villous trees among placental lobules.

The perplexing pregnancy disorder preeclampsia: what next?

Preeclampsia occurs in 3–5% of pregnancies and is a leading cause of deaths of mothers and their infants worldwide. It was initially described over 100 yr ago as a pregnancy abnormality defined by new-onset hypertension and proteinuria. Progress in understanding the pathophysiology was impeded by attention to these diagnostic findings. Hypertension and proteinuria were actually serendipitously recognized components of a complex multisystemic syndrome and not especially pertinent to outcome. With the recognition of inflammatory activation with consequent endothelial dysfunction 30 yr ago redirection of research resulted in an explosive increase in understanding of the disorder. The immunological origins, the role of the placenta and its functional alterations due to endoplasmic reticulum and oxidative stress, identification of placental products linking placental dysfunction to maternal systemic pathophysiology, and the role of the maternal constitution have been elegantly demonstrated by clinical, fundamental, and epidemiological findings and clever animal experimentation. Nonetheless, this increase in knowledge has not translated into improved prediction and prevention of preeclampsia. In this presentation the likelihood is discussed that this is secondary to a much greater complexity than has been previously considered and the existence of subtypes of preeclampsia that may not share an identical pathophysiology. The necessity for collaboration with data, sample, and intellectual sharing is addressed. An approach to addressing the challenges posed to such collaboration exemplified by the Global Pregnancy Collaboration is presented.

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.

Why natural killer cells are not enough: a further understanding of killer immunoglobulin-like receptor and human leukocyte antigen

The immune system's role in recurrent reproductive failure is a controversial issue in assisted reproduction. Most studies into immune system implication in reproduction have focused on finding markers of peripheral blood and less on the uterine environment. Peripheral blood natural killer cells have become an "immune study core" for women with recurrent miscarriage or recurrent implantation failure, based on the mistaken notion that they cause reproductive failure by killing or "rejecting" the embryo. Maternal-fetal tolerance begins at the uterine level, so successful adaptation to the fetus occurs after a complicated process. Insufficient uterine lining invasion by an invading extravillous trophoblast is the primary defect in pregnancy disorders such as recurrent miscarriage. This process is regulated by the interaction between maternal killer immunoglobulin-like receptors (KIRs), expressed by uterine natural killer cells (uNK), and their ligand human leukocyte antigen (HLA) C, expressed by the extravillous trophoblast. Pregnancies are an increased risk of disorders in mothers with KIR AA when the fetus has paternal HLA-C2. A recent report has indicated that the expression of more than one paternal HLA-C by the extravillous trophoblast in assisted reproduction may affect placentation in mothers with KIR AA. This review provides insight into the immune system's role in assisted reproductive treatments. These insights can have an impact on the selection of single-embryo transfer and/or oocyte/sperm donor according to HLA-C in patients with recurrent implantation failure and recurrent miscarriage depending on their KIR haplotype.

Decreased Endothelial Progenitor Cells (EPCs) and increased Natural Killer (NK) cells in peripheral blood as possible early markers of preeclampsia: a case-control analysis

PURPOSE

Endothelial Progenitor Cells (EPCs) and Natural Killer (NK) cells were recently advocates in the pathogenesis of preeclampsia (PE), since they can be mobilized into the bloodstream and may orchestrate vascular endothelium function. The aim of our study was to evaluate in early pregnancy circulating EPCs and NK cells in peripheral blood in women who later developed PE compared to uncomplicated pregnancies.

METHODS

We prospectively enrolled pregnant women at 9⁺⁰-11⁺⁶ weeks of gestation at the time of first-trimester integrated screening for trisomy 21, who underwent peripheral venous blood (20 mL) sample. We included only women who later developed PE (cases) and women with uncomplicated pregnancy (controls), matched for maternal age, parity, and Body Mass Index. In these groups, we evaluated the levels of CD16⁺CD45⁺CD56⁺ NK cells and CD34⁺CD133⁺VEGF-R2⁺ EPCs in peripheral blood samples previously stored.

RESULTS

EPCs were significantly lower (p < 0.001), whereas NK cells were significantly higher (p < 0.001) in PE group compared to uncomplicated pregnancies during the first trimester.

CONCLUSION

The evaluation of EPCs and NK cells in peripheral blood during the first trimester may be considered an effective screening for the early identification of women at risk of developing PE.

Regulatory B Cells in Pregnancy: Lessons from Autoimmunity, Graft Tolerance, and Cancer

The success of pregnancy is contingent on the maternal immune system recognizing and accommodating a growing semi-allogeneic fetus. Specialized subsets of lymphocytes capable of negative regulation are fundamental in this process, and include the regulatory T cells (Tregs) and potentially, regulatory B cells (Bregs). Most of our current understanding of the immune regulatory role of Bregs comes from studies in the fields of autoimmunity, transplantation tolerance, and cancer biology. Bregs control autoimmune diseases and can elicit graft tolerance by inhibiting the differentiation of effector T cells and dendritic cells (DCs), and activating Tregs. Furthermore, in cancer, Bregs are hijacked by neoplastic cells to promote tumorigenesis. Pregnancy therefore represents a condition that reconciles these fields-mechanisms must be in place to ensure maternal immunological tolerance throughout gravidity to allow the semi-allogeneic fetus to grow within. Thus, the mechanisms underlying Breg activities in autoimmune diseases, transplantation tolerance, and cancer may take place during pregnancy as well. In this review, we discuss the potential role of Bregs as guardians of pregnancy and propose an endocrine-modulated feedback loop highlighting the Breg-Treg-tolerogenic DC interface essential for the induction of maternal immune tolerance.

Is HLA-E a possible genetic marker relevant for natural conception?

BACKGROUND

HLA-E products, class Ib human leukocyte antigens, act in the immunology of human reproduction as modulators of the maternal immune system during pregnancy.

AIMS

To evaluate HLA-E role in the establishment of a viable pregnancy.

MATERIALS & METHODS

HLA-E was genotyped by sequence-based typing (SBT) and analyzed for specific polymorphisms, comparing couples who underwent assisted reproduction treatment (ART) and fertile control couples.

RESULTS

There was a significant difference in HLA-E allele and genotype distributions between ART couples and control couples. The allele HLA-E*01:03 was observed in 63.2% of ART men and in 35.1% of fertile men (P = 0.0032).

CONCLUSION

These results suggest that HLA-E allelic variants may play a role in the modulation of immune responses in the context of the inability of natural conception and establishment of a viable pregnancy.

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.

Marginal zone B cells emerge as a critical component of pregnancy well-being

The success of eutherian mammal evolution was certainly supported by the ability of the already existing immune system to adapt to the presence of the semi-allogeneic fetus without losing the capability to defend the mother against infections. This required the acquisition of highly regulated and coordinated immunological mechanisms. Failures in the development of these strategies not only lead to the interruption of pregnancy but also compromise maternal health. Alongside changes on the cytokine profile - expansion of tolerogenic dendritic and regulatory T cells - a profound adaptation of the B cell compartment during pregnancy was recently described. Among others, the suppression of B cell lymphopoiesis and B cell lymphopenia were proposed to be protective mechanisms tending to reduce the occurrence of autoreactive B cells that might recognize fetal structures and put pregnancy on risk. On the other hand, expansion of the pre-activated marginal zone (MZ) B cell phenotype was described as a compensatory strategy launched to overcome B cell lymphopenia thus ensuring a proper defense. In this work, using an animal model of pregnancy disturbances, we demonstrated that the suppression of B cell lymphopoiesis as well as splenic B cell lymphopenia occur independently of pregnancy outcome. However, only animals undergoing normal pregnancies, but not those suffering from pregnancy disturbances, could induce an expansion and activation of the MZ B cells. Hence, our results clearly show that MZ B cells, probably due to the production of natural protective antibodies, participate in the fine balance of immune activation required for pregnancy well-being.

IL-17 producing innate lymphoid cells 3 (ILC3) but not Th17 cells might be the potential danger factor for preeclampsia and other pregnancy associated diseases

In pregnancy, the immunologic system plays an important role that ensures normal pregnancy development and can as well promote the development of complications. Pregnancy success appears to rely on a discrete balance between the Th cytokines, which are involved in fetal growth and development. Preeclampsia and gestational diabetes are known complications associated with pregnancy. However, the source of the increased IL-17 cytokine in preeclampsia and other pregnancy associated diseases still remains unclear amidst numerous inconsistencies. The recent identification of innate lymphoid cells (ILC) has raised more doubts about the sources of most of the Th associated cytokines. We investigated the source of peripheral IL-17 levels in preeclamptic, gestational diabetics and chronic diabetics compared to healthy pregnancy subjects. To evaluate the source of the increased IL-17 cytokine among preeclampsia, chronic diabetic and gestational diabetic patients we investigated the proportion of Th17 cell populations in peripheral blood mononuclear cells using flow cytometry as well as analyzing levels of IFN-γ, IL-17, IL-1β and HMGB1. This study found that the Th17 cell populations in peripheral blood of preeclamptic, gestational nor chronic diabetes during pregnancy did not correlate with the increased IL-17. We report that the increased IL-17 levels observed in patients with preeclampsia, gestational diabetes and chronic diabetes are associated with innate lymphoid cells 3 (ILC3) and may pose threats to the fetus if disregulated.

Regional changes of placental vascularization in preeclampsia: a review

Preeclampsia is characterized by vascular dysfunction and results in maternal and fetal morbidity and mortality. The placenta plays a critical role in the growth and development of the fetus, and recent studies indicate that placental architecture, oxygen availability, and oxidative stress indices vary across different regions of the placenta. Our earlier studies have reported altered maternal angiogenesis and differential placental gene expression and methylation patterns of angiogenic factors in women with preeclampsia when compared with normotensive women. We have also demonstrated lower maternal and placental neurotrophin (NT) levels in women with preeclampsia. Studies suggest that oxidative stress is associated with proteases like matrix metalloproteinases (MMPs) and growth factors like NTs and angiogenic factors known to be involved in the process of angiogenesis. Recently, we have reported regionwise differential oxidative stress, antioxidant enzyme activity, and NT levels in placenta from normotensive control women and women with preeclampsia. The current review describes the regional changes in the placenta and highlights the role of placental oxidative stress in influencing regional differences in the expression of angiogenic factors, MMPs, and NTs. This review discusses the need for further research on various growth factors and proteins involved in the process of placental development across different regions of the placenta. This would help to understand whether regional differences in these factors affect the growth and development of the fetus.

Intrauterine insemination of cultured peripheral blood mononuclear cells prior to embryo transfer improves clinical outcome for patients with repeated implantation failures

Implantation failure is a major limiting factor in assisted reproduction improvement. Dysfunction of embryo–maternal immuno-tolerance pathways may be responsible for repeated implantation failures. This fact is supported by immunotropic theory stipulating that maternal immune cells, essentially uterine CD56+ natural killer cells, are determinants of implantation success. In order to test this hypothesis, we applied endometrium immuno-modulation prior to fresh embryo transfer for patients with repeated implantation failures. Peripheral blood mononuclear cells were isolated from repeated implantation failure patients undergoing assisted reproductive technology cycles. On the day of ovulation induction, cells were isolated and then cultured for 3 days and transferred into the endometrium cavity prior to fresh embryo transfer. This immunotherapy was performed on 27 patients with repeated implantation failures and compared with another 27 patients who served as controls. Implantation and clinical pregnancy were increased significantly in the peripheral blood mononuclear cell test versus control (21.54, 44.44 vs. 8.62, 14.81%). This finding suggests a clear role for endometrium immuno-modulation and the inflammation process in implantation success. Our study showed the feasibility of intrauterine administration of autologous peripheral blood mononuclear cells as an effective therapy to improve clinical outcomes for patients with repeated implantation failures and who are undergoing in vitro fertilization cycles.

Enhanced prevalence of plasmatic soluble MHC class I chain-related molecule in vascular pregnancy diseases

The major histocompatibility complex class I related chain (MIC) is a stress-inducible protein modulating the function of immune natural killer (NK) cells, a major leukocyte subset involved in proper trophoblast invasion and spiral artery remodeling. Aim of the study was to evaluate whether upregulation of soluble MIC (sMIC) may reflect immune disorders associated to vascular pregnancy diseases (VPD). sMIC was more frequently detected in the plasma of women with a diagnostic of VPD (32%) than in normal term-matched pregnancies (1.6%, P < 0.0001), with highest prevalence in intrauterine fetal death (IUDF, 44%) and vascular intrauterine growth restriction (IUGR, 39%). sMIC levels were higher in preeclampsia (PE) than in IUFD (P < 0.01) and vascular IUGR (P < 0.05). sMIC detection was associated with bilateral early diastolic uterine notches (P = 0.037), thrombocytopenia (P = 0.03), and high proteinuria (P = 0.03) in PE and with the vascular etiology of IUGR (P = 0.0038). Incubation of sMIC-positive PE plasma resulted in downregulation of NKG2D expression and NK cell-mediated IFN-γ production in vitro. Our work thus suggests that detection of sMIC molecule in maternal plasma may constitute a hallmark of altered maternal immune functions that contributes to vascular disorders that complicate pregnancy, notably by impairing NK-cell mediated production of IFN-γ, an essential cytokine favoring vascular modeling.

Association of maternal KIR and fetal HLA-C genes with the risk of preeclampsia in the Chinese Han population

INTRODUCTION

This study is to investigate the distribution of inhibitory and activating killer-cell immunoglobulin-like receptors (KIRs) and the combination of KIR/human leukocyte antigen (HLA)-C in women with preeclampsia in the Chinese Han population.

METHODS

A total of 271 patients and 295 controls were enrolled in our study. The inhibitory/activating KIR and HLA-C genes were detected using the PCR-SSP (polymerase chain reaction with sequence-specific primers) method.

RESULTS

Our result showed that decreased numbers of individual activating KIR genes (2DS2, 2DS3, and 2DS5) were observed in women with preeclampsia. Furthermore, the gene frequency of total activating KIRs was significantly lower in patients compared with that of the controls (P = 0.03). The frequency of the KIR2DL1 gene was increased in women with preeclampsia when a homozygous HLA-C2 allele appeared in the fetus.

CONCLUSION

The results suggest that a KIR genetic variation might influence the risk of preeclampsia. The lack of activating KIRs could possibly lower uterine natural killer (uNK) cell activation, thereby contributing to the pathogenesis of preeclampsia. Moreover, the imbalance of the inhibitory or activating signals at the maternal-fetal interface seems to play a regulatory role in the occurrence of preeclampsia.

Pathophysiology of ischemic placental disease

The pregnancy disorders associated with placental ischemia share many similar pathological and pathophysiological features and are associated with the failure to deliver adequate nutrients and oxygen to the placenta. The origins of this deficiency are a subject of intense study. In this article, I review the genesis and consequences of this pathology addressing the similarities and the differences with the different disorders and addressing current gaps in our knowledge.

Embryonic trophoblasts induce decidual regulatory T cell differentiation and maternal-fetal tolerance through thymic stromal lymphopoietin instructing dendritic cells

Physiological pregnancy requires the maternal immune system to recognize and tolerate embryonic Ags. Although multiple mechanisms have been proposed, it is not yet clear how the fetus evades the maternal immune system. In this article, we demonstrate that trophoblast-derived thymic stromal lymphopoietin (TSLP) instructs decidual CD11c(+) dendritic cells (dDCs)with increased costimulatory molecules; MHC class II; and Th2/3-type, but not Th1-type, cytokines. TSLP-activated dDCs induce proliferation and differentiation of decidual CD4(+)CD25(-) T cells into CD4(+)CD25(+)FOXP3(+) regulatory T cells (Tregs) through TGF-β1. TSLP-activated dDC-induced Tregs display immunosuppressive features and express Th2-type cytokines. In addition, decidual CD4(+)CD25(+)FOXP3(+) Tregs promote invasiveness and HLA-G expression of trophoblasts, resulting in preferential production of Th2 cytokines and reduced cytotoxicity in decidual CD56(bright)CD16(-) NK cells. Of interest, decreased TSLP expression and reduced numbers of Tregs were observed at the maternal-fetal interface during miscarriage. Our study identifies a novel feedback loop between embryo-derived trophoblasts and maternal decidual leukocytes, which induces a tolerogenic immune response to ensure a successful pregnancy.

Carbon monoxide promotes proliferation of uterine natural killer cells and remodeling of spiral arteries in pregnant hypertensive heme oxygenase-1 mutant mice

Heme Oxygenase-1 (HO-1) and its metabolite carbon monoxide (CO) promote implantation and placentation. Pregnancy disorders such as preeclampsia and intrauterine growth restriction are linked to both HO-1 diminution and impaired remodeling of maternal spiral arteries (SAs). Here, we investigated whether CO is able to prevent preeclampsia and intrauterine growth restriction through the modulation of uterine natural killer (uNK) cells that are necessary for initiation of SA remodeling. Hmox1(+/-) or Hmox1(-/-) implantations presented fewer uNK cell numbers and lower expression of uNK-related angiogeneic factors compared with Hmox1(+/+) sites. Quantitative histology revealed that Hmox1(+/-) and Hmox1(-/-) implantations had shallow SA development that was accompanied by intrauterine growth restriction and gestational hypertension. Application of CO at low dose during early to midgestation prevented intrauterine growth restriction in Hmox1(+/-) mothers, this being associated with enhanced in situ proliferation of uNK cells and normalization of angiogenic parameters. Most importantly, CO improved SA remodeling and normalized blood pressure, ensuring a proper fetal growth. Thus, CO emerges as a key molecular player in pregnancy success by modulating uNK cells, which results in promotion of SA remodeling, adequate fetal support/growth, and prevention of hypertension.

Expression of the activating receptor, NKp46 (CD335), in human natural killer and T-cell neoplasia

OBJECTIVES

To evaluate the expression of CD335 (NKp46), an activation receptor that is selectively expressed on natural killer (NK) cells.

METHODS

We assessed CD335's potential utility as a diagnostic marker in 657 cases by flow cytometry and 410 cases by immunohistochemistry.

RESULTS

We observed that CD335 was highly specific for NK cells in nonneoplastic tissues. Moreover, 61 (90%) of 68 of NK cell neoplasms demonstrated CD335 expression, whereas B-cell, myelomonocytic, and plasma cell neoplasms lacked expression. Notably, 16 (20%) of 82 mature T-cell neoplasms, particularly T-cell large granular lymphocytic leukemia, mycosis fungoides, and ALK+ anaplastic large cell lymphoma, aberrantly expressed CD335.

CONCLUSIONS

Collectively, these data support the diagnostic utility of CD335 in evaluating hematopoietic malignancies and suggest that CD335 could be a useful target for selective immunotherapy in patients with mature NK and T-cell neoplasms.

If we know so much about preeclampsia, why haven't we cured the disease?

Preeclampsia has been recognized for at least 100 years. In the last 20 years, the consideration of the disorder as more than simply hypertension in pregnancy has led to an explosion in knowledge about preeclampsia pathophysiology. It is now evident that for most cases of preeclampsia, the root cause is the placenta. Relatively reduced placental perfusion leads to inflammation, oxidative stress, and endoplasmic reticulum stress, which converge to modify maternal physiology, with endothelium an important target. Although preeclampsia is characteristically diagnosed in the last third of pregnancy, it is evident that many of these pathophysiological changes can be detected long before clinically evident disease. Furthermore, it is evident that the "maternal constitution," including genetic, behavioral, and metabolic factors, influences the maternal response to the abnormal placentation of preeclampsia. These insights would seem to provide a guide for the prediction of the disorder in early pregnancy, along with targets for intervention. However, this has not been the case. Predictive tests guided by this knowledge do not predict well and several interventions guided by the expanded understanding of pathophysiology do not prevent the disease. We propose that these failures are secondary to the fact that preeclampsia is more than one disorder. Further, we suggest that future progress toward prediction and prevention will require research guided by this concept.