Gene expression profiling of placentae from women with early- and late-onset pre-eclampsia: down-regulation of the angiogenesis-related genes ACVRL1 and EGFL7 in early-onset disease

Placenta accreta spectrum disorder at single-cell resolution: a loss of boundary limits in the decidua and endothelium

BACKGROUND

Placenta accreta spectrum disorders are associated with severe maternal morbidity and mortality. Placenta accreta spectrum disorders involve excessive adherence of the placenta preventing separation at birth. Traditionally, this condition has been attributed to excessive trophoblast invasion; however, an alternative view is a fundamental defect in decidual biology.

OBJECTIVE

This study aimed to gain insights into the understanding of placenta accreta spectrum disorder by using single-cell and spatially resolved transcriptomics to characterize cellular heterogeneity at the maternal-fetal interface in placenta accreta spectrum disorders.

STUDY DESIGN

To assess cellular heterogeneity and the function of cell types, single-cell RNA sequencing and spatially resolved transcriptomics were used. A total of 12 placentas were included, 6 placentas with placenta accreta spectrum disorder and 6 controls. For each placenta with placenta accreta spectrum disorder, multiple biopsies were taken at the following sites: placenta accreta spectrum adherent and nonadherent sites in the same placenta. Of note, 2 platforms were used to generate libraries: the 10× Chromium and NanoString GeoMX Digital Spatial Profiler for single-cell and spatially resolved transcriptomes, respectively. Differential gene expression analysis was performed using a suite of bioinformatic tools (Seurat and GeoMxTools R packages). Correction for multiple testing was performed using Clipper. In situ hybridization was performed with RNAscope, and immunohistochemistry was used to assess protein expression.

RESULTS

In creating a placenta accreta cell atlas, there were dramatic difference in the transcriptional profile by site of biopsy between placenta accreta spectrum and controls. Most of the differences were noted at the site of adherence; however, differences existed within the placenta between the adherent and nonadherent site of the same placenta in placenta accreta. Among all cell types, the endothelial-stromal populations exhibited the greatest difference in gene expression, driven by changes in collagen genes, namely collagen type III alpha 1 chain (COL3A1), growth factors, epidermal growth factor-like protein 6 (EGFL6), and hepatocyte growth factor (HGF), and angiogenesis-related genes, namely delta-like noncanonical Notch ligand 1 (DLK1) and platelet endothelial cell adhesion molecule-1 (PECAM1). Intraplacental tropism (adherent versus non-adherent sites in the same placenta) was driven by differences in endothelial-stromal cells with notable differences in bone morphogenic protein 5 (BMP5) and osteopontin (SPP1) in the adherent vs nonadherent site of placenta accreta spectrum.

CONCLUSION

Placenta accreta spectrum disorders were characterized at single-cell resolution to gain insight into the pathophysiology of the disease. An atlas of the placenta at single cell resolution in accreta allows for understanding in the biology of the intimate maternal and fetal interaction. The contributions of stromal and endothelial cells were demonstrated through alterations in the extracellular matrix, growth factors, and angiogenesis. Transcriptional and protein changes in the stroma of placenta accreta spectrum shift the etiologic explanation away from "invasive trophoblast" to "loss of boundary limits" in the decidua. Gene targets identified in this study may be used to refine diagnostic assays in early pregnancy, track disease progression over time, and inform therapeutic discoveries.

Pathogenic Variant Frequencies in Hereditary Haemorrhagic Telangiectasia Support Clinical Evidence of Protection from Myocardial Infarction

Hereditary haemorrhagic telangiectasia (HHT) is a vascular dysplasia inherited as an autosomal dominant trait, due to a single heterozygous loss-of-function variant, usually in ACVRL1 (encoding activin receptor-like kinase 1 [ALK1]), ENG (encoding endoglin [CD105]), or SMAD4. In a consecutive single-centre series of 37 positive clinical genetic tests performed in 2021-2023, a skewed distribution pattern was noted, with 30 of 32 variants reported only once, but ACVRL1 c.1231C>T (p.Arg411Trp) identified as the disease-causal gene in five different HHT families. In the same centre's non-overlapping 1992-2020 series where 110/134 (82.1%) HHT-causal variants were reported only once, ACVRL1 c.1231C>T (p.Arg411Trp) was identified in nine further families. In a 14-country, four-continent HHT Mutation Database where 181/250 (72.4%) HHT-causal variants were reported only once, ACVRL1 c.1231C>T (p.Arg411Trp) was reported by 12 different laboratories, the adjacent ACVRL1 c.1232G>A (p.Arg411Gln) by 14, and ACVRL1 c.1120C>T (p.Arg374Trp) by 18. Unlike the majority of HHT-causal ACVRL1 variants, these encode ALK1 protein that reaches the endothelial cell surface but fails to signal. Six variants of this type were present in the three series and were reported 6.8-25.5 (mean 8.9) times more frequently than the other ACVRL1 missense variants (all p-values < 0.0039). Noting lower rates of myocardial infarction reported in HHT, we explore potential mechanisms, including a selective paradigm relevant to ALK1's role in the initiating event of atherosclerosis, where a plausible dominant negative effect of these specific variants can be proposed. In conclusion, there is an ~9-fold excess of kinase-inactive, cell surface-expressed ACVRL1/ALK1 pathogenic missense variants in HHT. The findings support further examination of differential clinical and cellular phenotypes by HHT causal gene molecular subtypes.

Preeclampsia-associated lncRNA FEZF1-AS1 regulates cell proliferation and apoptosis in placental trophoblast cells through the ELAVL1/NOC2L axis

BACKGROUND

LncRNAs have been shown to be involved in and control the biological processes of multiple diseases, including preeclampsia (PE). The impairment of trophoblast cell proliferation is recognized as a significant anomaly contributing to the development of PE. LncRNA FEZF1-AS1 was found downregulated in placental tissues of PE patients. However, the precise regulatory mechanism of FEZF1-AS1 in placental trophoblast proliferation and apoptosis remains unclear.

RESULTS

In this study, we conducted an investigation into the expression levels of FEZF1-AS1 and NOC2L in placental tissues obtained from patients diagnosed with PE. Subsequently, we employed CCK-8 and EdU assays to quantify cell proliferation, while TUNEL staining and western blot for apoptosis-related protein detection to assess apoptosis. Furthermore, the interactions between FEZF1-AS1 and ELAVL1, as well as NOC2L and ELAVL1, were confirmed through the implementation of RIP and RNA pull-down assays. We found a downregulation of lncRNA FEZF1-AS1 and NOC2L in placental tissues of PE patients. Overexpression of FEZF1-AS1 or NOC2L resulted in increased cell proliferation and inhibition of apoptosis, whereas knockdown of FEZF1-AS1 or NOC2L had the opposite effect. In addition, lncRNA FEZF1-AS1 stabilized NOC2L mRNA expression by interacting with ELAVL1. Moreover, partial reversal of the effects of FEZF1-AS1 overexpression on cell proliferation and apoptosis was observed upon suppression of ELAVL1 or NOC2L.

CONCLUSIONS

PE related lncRNA FEZF1-AS1 could regulate apoptosis and proliferation of placental trophoblast cells through the ELAVL1/NOC2L axis.

Elevated expression of glycolytic genes as a prominent feature of early-onset preeclampsia: insights from integrative transcriptomic analysis

Introduction: Preeclampsia (PE), a notable pregnancy-related disorder, leads to 40,000+ maternal deaths yearly. Recent research shows PE divides into early-onset (EOPE) and late-onset (LOPE) subtypes, each with distinct clinical features and outcomes. However, the molecular characteristics of various subtypes are currently subject to debate and are not consistent. Methods: We integrated transcriptomic expression data from a total of 372 placental samples across 8 publicly available databases via combat algorithm. Then, a variety of strategies including Random Forest Recursive Feature Elimination (RF-RFE), differential analysis, oposSOM, and Weighted Correlation Network Analysis were employed to identify the characteristic genes of the EOPE and LOPE subtypes. Finally, we conducted in vitro experiments on the key gene HK2 in HTR8/SVneo cells to explore its function. Results: Our results revealed a complex classification of PE placental samples, wherein EOPE manifests as a highly homogeneous sample group characterized by hypoxia and HIF1A activation. Among the core features is the upregulation of glycolysis-related genes, particularly HK2, in the placenta-an observation corroborated by independent validation data and single-cell data. Building on the pronounced correlation between HK2 and EOPE, we conducted in vitro experiments to assess the potential functional impact of HK2 on trophoblast cells. Additionally, the LOPE samples exhibit strong heterogeneity and lack distinct features, suggesting a complex molecular makeup for this subtype. Unsupervised clustering analysis indicates that LOPE likely comprises at least two distinct subtypes, linked to cell-environment interaction and cytokine and protein modification functionalities. Discussion: In summary, these findings elucidate potential mechanistic differences between the two PE subtypes, lend support to the hypothesis of classifying PE based on gestational weeks, and emphasize the potential significant role of glycolysis-related genes, especially HK2 in EOPE.

Evaluation Of Epidermal Growth Factor-Like Domain (EGFL7) mRNA Expression and its Protein Level in Preeclampsia

Objectives

To evaluate the mRNA expression of epidermal growth factor-like domain 7 (EGFL7) in maternal blood and its protein level in sera of pregnant women complicated with preeclampsia (PE).

Method

Case-control study involving 25 pregnant women diagnosed with PE (cases) and 25 gestational age-matched normal pregnant women (controls). EGFL7 mRNA expression in normal and PE patients was quantified by (qRT-PCR), and EGFL7 protein level was estimated using ELISA.

Results

The RQ values of EGFL7 in the PE group were significantly higher than in the NC group (P < 0.001). Pregnancies affected with PE showed higher serum EGFL7 protein compared with matched controls (P < 0.001). EGFL7 serum level cutoff value ≥ 38.25 µg/ml could be used in the diagnosis of PE with sensitivity = 92%, and specificity = 88%.

Conclusion

EGFL7 mRNA is overexpressed in maternal blood of pregnancies complicated with preeclampsia. Serum EGFL7 protein is elevated in PE cases and can be used as a diagnostic marker for preeclampsia.

Circulating EGFL7 distinguishes between IUGR and PE: an observational case-control study

Isolated intrauterine growth restriction (IUGR) and preeclampsia (PE) share common placental pathogenesis. Differently from IUGR, PE is a systemic disorder which may also affect liver and brain. Early diagnosis of these conditions may optimize maternal and fetal management. Aim of this study was to assess whether Epidermal Growth Factor-Like domain 7 (EGFL7) dosage in maternal blood discriminates between isolated IUGR and PE. A total of 116 women were enrolled in this case–control study: 12 non-pregnant women, 34 healthy pregnant women, 34 women presenting with isolated IUGR and 36 presenting with PE. Levels of circulating EGFL7 and other known pro- and anti-angiogenic factors were measured by ELISA at different gestational ages (GA). Between 22–25 weeks of gestation, EGFL7 levels in early-onset PE (e-PE) plasma samples were significantly higher than those measured in controls or isolated IUGR samples (69.86 ± 6.17 vs. 19.8 ± 2.5 or 18.8 ± 2.8 µg/ml, respectively). Between 26–34 weeks, EGFL7 levels remained significantly higher in e-PE compared to IUGR. At term, circulating and placental EGFL7 levels were comparable between IUGR and late-onset PE (l-PE). In contrast, circulating levels of PlGF were decreased in both IUGR- and PE- complicated pregnancies, while levels of both sFLT-1 and sENDOGLIN were increased in both conditions. In conclusion, EGFL7 significantly discriminates between isolated IUGR and PE.

Current approaches and developments in transcript profiling of the human placenta

BACKGROUND

The placenta is the active interface between mother and foetus, bearing the molecular marks of rapid development and exposures in utero. The placenta is routinely discarded at delivery, providing a valuable resource to explore maternal-offspring health and disease in pregnancy. Genome-wide profiling of the human placental transcriptome provides an unbiased approach to study normal maternal–placental–foetal physiology and pathologies.

OBJECTIVE AND RATIONALE

To date, many studies have examined the human placental transcriptome, but often within a narrow focus. This review aims to provide a comprehensive overview of human placental transcriptome studies, encompassing those from the cellular to tissue levels and contextualize current findings from a broader perspective. We have consolidated studies into overarching themes, summarized key research findings and addressed important considerations in study design, as a means to promote wider data sharing and support larger meta-analysis of already available data and greater collaboration between researchers in order to fully capitalize on the potential of transcript profiling in future studies.

SEARCH METHODS

The PubMed database, National Center for Biotechnology Information and European Bioinformatics Institute dataset repositories were searched, to identify all relevant human studies using ‘placenta’, ‘decidua’, ‘trophoblast’, ‘transcriptome’, ‘microarray’ and ‘RNA sequencing’ as search terms until May 2019. Additional studies were found from bibliographies of identified studies.

OUTCOMES

The 179 identified studies were classifiable into four broad themes: healthy placental development, pregnancy complications, exposures during pregnancy and in vitro placental cultures. The median sample size was 13 (interquartile range 8–29). Transcriptome studies prior to 2015 were predominantly performed using microarrays, while RNA sequencing became the preferred choice in more recent studies. Development of fluidics technology, combined with RNA sequencing, has enabled transcript profiles to be generated of single cells throughout pregnancy, in contrast to previous studies relying on isolated cells. There are several key study aspects, such as sample selection criteria, sample processing and data analysis methods that may represent pitfalls and limitations, which need to be carefully considered as they influence interpretation of findings and conclusions. Furthermore, several areas of growing importance, such as maternal mental health and maternal obesity are understudied and the profiling of placentas from these conditions should be prioritized.

WIDER IMPLICATIONS

Integrative analysis of placental transcriptomics with other ‘omics’ (methylome, proteome and metabolome) and linkage with future outcomes from longitudinal studies is crucial in enhancing knowledge of healthy placental development and function, and in enabling the underlying causal mechanisms of pregnancy complications to be identified. Such understanding could help in predicting risk of future adversity and in designing interventions that can improve the health outcomes of both mothers and their offspring. Wider collaboration and sharing of placental transcriptome data, overcoming the challenges in obtaining sufficient numbers of quality samples with well-defined clinical characteristics, and dedication of resources to understudied areas of pregnancy will undoubtedly help drive the field forward.

Abnormal expression of the costimulatory molecule B7-H4 in placental chorionic villous and decidual basalis tissues of patients with preeclampsia and HELLP syndrome

BACKGROUND

B7-H4, a checkpoint molecule of the B7 family, regulates a broad spectrum such as T-cell activation, cytokine secretion, tumour progression, and invasion capacities. Our previous data revealed that soluble B7-H4 (sB7-H4) blood serum levels are elevated in women at high risk for the hypertensive pregnancy disorder preeclampsia (PE) in the first trimester, as well as in patients with confirmed early/late-onset PE.

AIM

We here aim to investigate the expression pattern of B7-H4 in placental tissues of PE and HELLP Syndrome versus control group.

METHODS

B7-H4 protein expression and localization were investigated by immunoblotting and co-immunohistochemistry in placental chorionic villous and decidual basalis tissues.

RESULTS

B7-H4 protein was prominently expressed at the cell membrane, in the cytoplasm of the syncytiotrophoblast (STB) and interstitial extravillous trophoblast (EVT). B7-H4 protein levels in placental chorionic villous tissue were significantly higher in women with early-onset/late-onset PE and HELLP, while it was decreased in decidual basalis tissues of early-onset PE and HELLP compared with controls.

CONCLUSION

B7-H4 was inversely expressed in placental chorionic villous and decidual basalis tissues of PE and HELLP patients. The increase in B7-H4 in the STB in PE and HELLP may lead to excessive apical expression and release of soluble B7-H4 in the maternal circulation. In contrast, the decrease in B7-H4 in decidual basalis tissues could be related to the decrease in invasion ability of the EVT in PE. Thus, the current results strongly suggest that B7-H4 is involved in the pathogenesis of PE and HELLP.

Distinct placental molecular processes associated with early-onset and late-onset preeclampsia

Background: Patients with preeclampsia display a spectrum of onset time and severity of clinical presentation, yet the underlying molecular bases for the early-onset and late-onset clinical subtypes are not known. Although several transcriptome studies have been done on placentae from PE patients, only a small number of differentially expressed genes have been identified due to very small sample sizes and no distinguishing of clinical subtypes. Methods: We carried out RNA-seq on 65 high-quality placenta samples, including 33 from 30 patients and 32 from 30 control subjects, to search for dysregulated genes and the molecular network and pathways they are involved in. Results: We identified two functionally distinct sets of dysregulated genes in the two major subtypes: 2,977 differentially expressed genes in early-onset severe preeclampsia, which are enriched with metabolism-related pathways, notably transporter functions; and 375 differentially expressed genes in late-onset severe preeclampsia, which are enriched with immune-related pathways. We also identified some key transcription factors, which may drive the widespread gene dysregulation in both early-onset and late-onset patients. Conclusion: These results suggest that early-onset and late-onset severe preeclampsia have different molecular mechanisms, whereas the late-onset mild preeclampsia may have no placenta-specific causal factors. A few regulators may be the key drivers of the dysregulated molecular pathways.

Identification of potential crucial genes associated with early-onset preeclampsia via bioinformatic analysis

INTRODUCTION

Early-onset preeclampsia is a pregnancy complication associated with high maternal and perinatal morbidity, mortality. Intense efforts have been made to elucidate the pathogenesis, but the molecular mechanism is still elusive. This study aimed to identify potential key genes related to early-onset preeclampsia, and to obtain a better understanding of the molecular mechanisms of this disease.

METHODS

We performed a multi-step integrative bioinformatics analysis of microarray dataset GSE74341 downloaded from Gene Expression Omnibus (GEO) database including 7 early-onset preeclampsia and 5 gestational age matched normotensive controls. The differentially expressed genes (DEGs) were identified using the "limma" package, and their potential functions were predicted by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Furthermore, the protein-protein interaction network (PPI) was obtained from the STRING database and the PPI network was visualized by Cytoscape software. Then, hub modules and hub genes were screened out from the PPI network, and enrichment analysis was performed for them. Also, validation of hub genes expression in early-onset PE was down by using microarray dataset GSE44711.

RESULTS

A total of 628 DEGs (256 down- and 372 up-regulated) were identified in early-onset PE compared to controls. A total of 4 significant hub modules and 26 significant hub genes were identified.

CONCLUSION

In conclusion, the DEGs related to cell-cell or cell-extracellular matrix interaction (ITGA5, SPP1, LUM, VCAN, APP), placenta metabolic or oxidative stress (CCR7, NT5E, CYBB) were predicted to be newly potential crucial genes that may play significant roles in the pathogenesis of early-onset PE.

Comprehensive Analysis of Differently Expressed and Methylated Genes in Preeclampsia

Preeclampsia (PE) is one of the mainly caused maternal and infant incidences and mortalities worldwide. However, the mechanisms underlying PE remained largely unclear. The present study identified 1716 high expressions of gene and 2705 low expressions of gene using GSE60438 database, and identified 7087 hypermethylated and 15120 hypomethylated genes in preeclampsia using GSE100197. Finally, 536 upregulated genes with hypomethylation and 322 downregulated genes with hypermethylation were for the first time revealed in PE. Gene Ontology (GO) analysis revealed that these genes were associated with peptidyl-tyrosine phosphorylation, skeletal system development, leukocyte migration, transcription regulation, T cell receptor and IFN-γ-involved pathways, innate immune response, signal transduction, cell adhesion, angiogenesis, and hemopoiesis. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that aberrantly methylated differentially expressed genes were involved in regulating adherens junction, pluripotency of stem cell regulation, immune processing, T cell receptor and NF-κB pathways, HTLV-I and HSV infections, leishmaniasis, and NK-induced cytotoxicity. Protein-protein interaction (PPI) network analysis identified several hub networks and key genes, including MAPK8, CCNF, CDC23, ABL1, NF1, UBE2E3, CD44, and PIK3R1. We hope these findings will draw more attention to these hub genes in future PE studies.

Evaluation of carcinoembryonic antigen-related cell adhesion molecule 1 blood serum levels in women at high risk for preeclampsia

PROBLEM

The aim of this study was to evaluate the sCEACAM1 concentrations in serum from patients in the first trimester who have a high risk for developing PE during pregnancy.

METHOD OF THE STUDY

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) levels were determined with ELISA. The patients (n = 109) were divided into two groups: patients who have a high risk of developing PE early-onset and a control group. Patients who have a high risk of developing PE were then divided into two subgroups depending on PE development in third trimester of pregnancy: PE in third trimester versus no PE in third trimester.

RESULTS

sCEACAM1 concentrations in patients who were screened as having a high risk for developing PE were significantly higher than in healthy pregnant women in the first trimester (p = .03). The highest sCEACAM1 concentration was found in the high-risk group with PE development compared to the control group (p = .004).

CONCLUSION

Elevated sCEACAM1 blood serum levels in women with PE suggest that there is immune dysregulation in early pregnancy, which may be helpful in PE prediction and therapy.

Preeclampsia-Associated lncRNA INHBA-AS1 Regulates the Proliferation, Invasion, and Migration of Placental Trophoblast Cells

Preeclampsia is believed to be caused by impaired placentation with insufficient trophoblast invasion, leading to impaired uterine spiral artery remodeling and angiogenesis. However, the underlying molecular mechanism remains unknown. We recently carried out transcriptome profiling of placental long noncoding RNAs (lncRNAs) and identified 383 differentially expressed lncRNAs in early-onset severe preeclampsia. Here, we are reporting our identification of lncRNA INHBA-AS1 as a potential causal factor of preeclampsia and its downstream pathways that may be involved in placentation. We found that INHBA-AS1 was upregulated in patients and positively correlated with clinical severity. We systematically searched for potential INHBA-AS1-binding transcription factors and their targets in databases and found that the targets were enriched with differentially expressed genes in the placentae of patients. We further demonstrated that the lncRNA INHBA-AS1 inhibited the invasion and migration of trophoblast cells through restraining the transcription factor CENPB from binding to the promoter of TNF receptor-associated factor 1 (TRAF1). Therefore, we have identified the dysregulated pathway "INHBA-AS1-CENPB-TRAF1" as a contributor to the pathogenesis of preeclampsia through prohibiting the proliferation, invasion, and migration of trophoblasts during placentation.

Identification of Differentially Expressed Genes and Signaling Pathways in Placenta Tissue of Early-Onset and Late-Onset Pre-Eclamptic Pregnancies by Integrated Bioinformatics Analysis

Background

Pre-eclampsia (PE) can be divided into 2 sub-groups: early-onset and late-onset PE. Although these sub-groups show overlapping molecular and cellular mechanisms and similar clinical manifestations, they are regarded as 2 different phenotypes with heterogeneous manifestations. The pathophysiological mechanisms underlying early-onset and late-onset PE still remain unclear. Therefore, the present study aimed to identify the key genes and pathways related to early-onset and late-onset PE, and to investigate the molecular mechanisms that are involved in gene regulation.

Material/Methods

Our analysis involved the Gene Expression Series (GSE) 74341 and GSE22526 from the National Center of Biotechnology Information (NCBI) Gene Expression Omnibus Database. These 2 microarray datasets included 15 patients with early-onset PE and 15 patients with late-onset PE.

Results

Our analyses identified 15 differentially expressed genes (DEGs), including CGA, EGR1, HBB, HBA2, LEP, and LHB. Gene Ontology (GO) functional annotation showed that the biological functions of these DEGs were mainly associated with steroid biosynthetic, oxidative stress, angiogenesis, and sex differentiation. Signaling pathway analyses showed that these DEGs were mainly involved in the prolactin signaling pathway, hormone metabolism, the AMPK signaling pathway, and the FoxO signaling pathway. Protein-protein interaction (PPI) network analysis identified 4 genes with the highest degree of interaction. The hub genes for this selection of DEGS were EGR1, LEP, and HBB.

Conclusions

Integrated bioinformatic analyses provide us with a new approach to further understand the pathophysiology and molecular mechanisms underlying early-onset and late-onset PE. The DEGs identified in this study represent potential biomarkers for the early diagnosis of PE and may provide significant options the treatment of these 2 subtypes of PE.

From animal models to patients: the role of placental microRNAs, miR-210, miR-126, and miR-148a/152 in preeclampsia

Placental microRNAs (miRNAs) regulate the placental transcriptome and play a pathological role in preeclampsia (PE), a hypertensive disorder of pregnancy. Three PE rodent model studies explored the role of placental miRNAs, miR-210, miR-126, and miR-148/152 respectively, by examining expression of the miRNAs, their inducers, and potential gene targets. This review evaluates the role of miR-210, miR-126, and miR-148/152 in PE by comparing findings from the three rodent model studies with in vitro studies, other animal models, and preeclamptic patients to provide comprehensive insight into genetic components and pathological processes in the placenta contributing to PE. The majority of studies demonstrate miR-210 is upregulated in PE in part driven by HIF-1α and NF-κBp50, stimulated by hypoxia and/or immune-mediated processes. Elevated miR-210 may contribute to PE via inhibiting anti-inflammatory Th2-cytokines. Studies report an up- and downregulation of miR-126, arguably reflecting differences in expression between cell types and its multifunctional capacity. MiR-126 may play a pro-angiogenic role by mediating the PI3K-Akt pathway. Most studies report miR-148/152 family members are upregulated in PE. Evidence suggests they may inhibit DNA methylation of genes involved in metabolic and inflammatory pathways. Given the genetic heterogeneity of PE, it is unlikely that a single placental miRNA is a suitable therapeutic target for all patients. Investigating miRNAs in PE subtypes in patients and animal models may represent a more appropriate approach going forward. Developing methods for targeting placental miRNAs and specific placental cell types remains crucial for research seeking to target placental miRNAs as a novel treatment for PE.

An Insight into the Angiogenic and Lymphatic Interplay in Pre-eclampsia Comorbid with HIV Infection

PURPOSE OF REVIEW

To provide insight on the imbalance of angiogenic and lymphangiogenic factors in pre-eclampsia, as well as highlight polymorphism in genes related to angiogenesis and lymphangiogenesis.

RECENT FINDINGS

The pregnancy-specific disorder pre-eclampsia is diagnosed by the presence of hypertension with/without proteinuria, after 20 weeks of gestation. The pathogenesis of pre-eclampsia remains ambiguous, but research over the years has identified an imbalance in maternal and foetal factors. Familial predisposition and gene variation are also linked to pre-eclampsia development. The sFlt-1/PIGF ratio has attracted great attention over the years; more recently several researchers have reported that a sFlt-1/PIGF ratio of ≤ 38 can be used to predict short-term absence of pre-eclampsia. This ratio has the potential to prevent adverse pregnancy outcomes and reduce healthcare costs significantly. Genome-wide studies have additionally identified variation in the foetal gene near Flt-1. The development of preeclampsia is not limited to the maternal interface, but foetal involvement as well as genetic interplay is associated with the disorder.

The TGFβ Family in Human Placental Development at the Fetal-Maternal Interface

Emerging data suggest that a trophoblast stem cell (TSC) population exists in the early human placenta. However, in vitro stem cell culture models are still in development and it remains under debate how well they reflect primary trophoblast (TB) cells. The absence of robust protocols to generate TSCs from humans has resulted in limited knowledge of the molecular mechanisms that regulate human placental development and TB lineage specification when compared to other human embryonic stem cells (hESCs). As placentation in mouse and human differ considerably, it is only with the development of human-based disease models using TSCs that we will be able to understand the various diseases caused by abnormal placentation in humans, such as preeclampsia. In this review, we summarize the knowledge on normal human placental development, the placental disease preeclampsia, and current stem cell model systems used to mimic TB differentiation. A special focus is given to the transforming growth factor-beta (TGFβ) family as it has been shown that the TGFβ family has an important role in human placental development and disease.

Integrated analysis of the transcriptome-wide m6A methylome in preeclampsia and healthy control placentas

N6-methyladenosine (m6A) is the most prevalent modification in eukaryotic mRNA and potential regulatory functions of m6A have been shown by mapping the RNA m6A modification landscape. m6A modification in active gene regulation manifests itself as altered methylation profiles. The number of reports regarding to the profiling of m6A modification and its potential role in the placenta of preeclampsia (PE) is small. In this work, placental samples were collected from PE and control patients. Expression of m6A-related genes was investigated using quantitative real-time PCR. MeRIP-seq and RNA-seq were performed to detect m6A methylation and mRNA expression profiles. Gene ontology (GO) functional and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses were also conducted to explore the modified genes and their clinical significance. Our findings show that METTL3 and METTL14 were up-regulated in PE. In total, 685 m6A peaks were differentially expressed as determined by MeRIP-seq. Altered peaks of m6A-modified transcripts were primarily associated with nitrogen compound metabolic process, positive regulation of vascular-associated smooth muscle cell migration, and endoplasmic reticulum organisation. The m6A hyper-methylated genes of Wnt/β-catenin signalling pathway, mTOR signalling pathway, and several cancer-related pathways may contribute to PE. We also verified that the significant increase of HSPA1A mRNA and protein expression was regulated by m6A modification, suggesting m6A plays a key role in the regulation of gene expression. Our data provide novel information regarding m6A modification alterations in PE and help our understanding of the pathogenesis of PE.

Pre-eclampsia: pathophysiology and clinical implications

Pre-eclampsia is a common disorder that particularly affects first pregnancies. The clinical presentation is highly variable but hypertension and proteinuria are usually seen. These systemic signs arise from soluble factors released from the placenta as a result of a response to stress of syncytiotrophoblast. There are two sub-types: early and late onset pre-eclampsia, with others almost certainly yet to be identified. Early onset pre-eclampsia arises owing to defective placentation, whilst late onset pre-eclampsia may center around interactions between normal senescence of the placenta and a maternal genetic predisposition to cardiovascular and metabolic disease. The causes, placental and maternal, vary among individuals. Recent research has focused on placental-uterine interactions in early pregnancy. The aim now is to translate these findings into new ways to predict, prevent, and treat pre-eclampsia.

Increased circulating levels of Epidermal Growth Factor-like Domain 7 in pregnant women affected by preeclampsia

Proper placental development is crucial to establish a successful pregnancy. Defective placentation is the major cause of several pregnancy complications, including preeclampsia (PE). We have previously demonstrated that the secreted factor Epidermal Growth Factor-like Domain 7 (EGFL7) is expressed in trophoblast cells of the human placenta and that it regulates trophoblast migration and invasion, suggesting a role in placental development. In the present study, we demonstrate that circulating levels of EGFL7 are undetectable in nonpregnant women, increase during pregnancy and decline toward term. Close to term, circulating levels of EGFL7 are significantly higher in patients affected by PE when compared to normal pregnancies. Consistent with these results, villus explant cultures obtained from placentas affected by PE display increased release of EGFL7 in the culture medium when compared to those from normal placentas. Our results suggest that increased release of placenta-derived EGFL7 and increased circulating levels of EGFL7 are associated with the clinical manifestation of PE.

Comparative Analysis of the Transcriptome and Proteome during Mouse Placental Development

The condition of the placenta is a determinant of the short- and long-term health of the mother and the fetus. However, critical processes occurring in early placental development, such as trophoblast invasion and establishment of placental metabolism, remain poorly understood. To gain a better understanding of the genes involved in regulating these processes, we utilized a multiomics approach, incorporating transcriptome, proteome, and phosphoproteome data generated from mouse placental tissue collected at two critical developmental time points. We found that incorporating information from both the transcriptome and proteome identifies genes associated with time point-specific biological processes, unlike using the proteome alone. We further inferred genes upregulated on the basis of the proteome data but not the transcriptome data at each time point, leading us to identify 27 genes that we predict to have a role in trophoblast migration or placental metabolism. Finally, using the phosphoproteome data set, we discovered novel phosphosites that may play crucial roles in the regulation of placental transcription factors. By generating the largest proteome and phosphoproteome data sets in the developing placenta, and integrating transcriptome analysis, we uncovered novel aspects of placental gene regulation.

EGFL7 gene expression is regulated by hypoxia in trophoblast and altered in the plasma of patients with early preeclampsia

INTRODUCTION

Preeclampsia is a severe complication of pregnancy, and likely arises from abnormal placental development in early pregnancy. Persistent placental hypoxia is thought to trigger the release of anti-angiogenic factors into the maternal circulation leading to widespread endothelial dysfunction. Epidermal growth factor-like domain 7 (EGFL7) is a secreted angiogenic factor that may play a key role in the disrupted angiogenesis seen in response to placental hypoxia that characterizes preeclampsia.

METHODS

Primary trophoblasts were isolated and cultured in both normoxic and hypoxic conditions. Under hypoxia HIF1α was silenced and EGFL7 mRNA expression was assessed. EGFL7 mRNA expression was measured in placentas obtained from women with early (<34 weeks) and late onset preeclampsia; and in peripheral whole blood maternal samples from women with preeclampsia and gestation matched controls. EGFL7 plasma levels were assessed in plasma from women with preeclampsia, compared to gestation-matched controls.

RESULTS

EGFL7 expression was significantly upregulated in primary human trophoblasts cultured in hypoxia (>2-fold, p < 0.0001), however this was not regulated via a HIF1α dependent manner. EGFL7 mRNA expression was not altered in placenta from women with early or late onset preeclampsia. Circulating EGFL7 protein levels were not different in women with severe preeclampsia. In contrast, EGFL7 mRNA expression was increased in maternal blood in women with early onset preeclampsia (∼1.6-fold, p < 0.05).

DISCUSSION

EGFL7 mRNA expression is increased with hypoxia in human trophoblast and is increased in the maternal circulation in women with preeclampsia. Further studies aimed at understanding the role and regulation of EGLF7 in the pathophysiology of preeclampsia are required.

Integrated Systems Biology Approach Identifies Novel Maternal and Placental Pathways of Preeclampsia

Preeclampsia is a disease of the mother, fetus, and placenta, and the gaps in our understanding of the complex interactions among their respective disease pathways preclude successful treatment and prevention. The placenta has a key role in the pathogenesis of the terminal pathway characterized by exaggerated maternal systemic inflammation, generalized endothelial damage, hypertension, and proteinuria. This sine qua non of preeclampsia may be triggered by distinct underlying mechanisms that occur at early stages of pregnancy and induce different phenotypes. To gain insights into these molecular pathways, we employed a systems biology approach and integrated different "omics," clinical, placental, and functional data from patients with distinct phenotypes of preeclampsia. First trimester maternal blood proteomics uncovered an altered abundance of proteins of the renin-angiotensin and immune systems, complement, and coagulation cascades in patients with term or preterm preeclampsia. Moreover, first trimester maternal blood from preterm preeclamptic patients in vitro dysregulated trophoblastic gene expression. Placental transcriptomics of women with preterm preeclampsia identified distinct gene modules associated with maternal or fetal disease. Placental "virtual" liquid biopsy showed that the dysregulation of these disease gene modules originates during the first trimester. In vitro experiments on hub transcription factors of these gene modules demonstrated that DNA hypermethylation in the regulatory region of ZNF554 leads to gene down-regulation and impaired trophoblast invasion, while BCL6 and ARNT2 up-regulation sensitizes the trophoblast to ischemia, hallmarks of preterm preeclampsia. In summary, our data suggest that there are distinct maternal and placental disease pathways, and their interaction influences the clinical presentation of preeclampsia. The activation of maternal disease pathways can be detected in all phenotypes of preeclampsia earlier and upstream of placental dysfunction, not only downstream as described before, and distinct placental disease pathways are superimposed on these maternal pathways. This is a paradigm shift, which, in agreement with epidemiological studies, warrants for the central pathologic role of preexisting maternal diseases or perturbed maternal-fetal-placental immune interactions in preeclampsia. The description of these novel pathways in the "molecular phase" of preeclampsia and the identification of their hub molecules may enable timely molecular characterization of patients with distinct preeclampsia phenotypes.

Soluble B7-H4 blood serum levels are elevated in women at high risk for preeclampsia in the first trimester, as well as in patients with confirmed preeclampsia

PROBLEM

B7-H4 negatively regulates T-cell-mediated immunity and might play an important role in preeclampsia (PE). Here, we have investigated the association between PE and maternal soluble B7-H4 (sB7-H4) serum levels and B7-H4 mRNA expression in the placenta.

METHOD OF STUDY

Maternal serum levels of sB7-H4 were determined by enzyme-linked immunosorbent assay in women between 11 and 13 weeks' gestation with elevated risk for PE (n = 48) and women without elevated risk for PE (n = 47). In the third trimester, sB7-H4 serum levels (n = 166) and B7-H4 mRNA expression in the placenta (n = 54) were determined in women with early-onset PE, late-onset PE, fetal growth restriction (FGR), and in healthy controls.

RESULTS

In the first trimester, significant higher levels of sB7-H4 were detected in women at elevated risk for PE compared to women without risk for PE (P < .0001). sB7-H4 has some predictive ability to identify cases with an elevated risk of developing PE with area under the curve (AUC) value of 0.88 (95% CI 0.8-0.94). Using a specificity of 90.0% led to a sensitivity of 47.9% and a threshold of 3.63 ng/mL. In the third trimester, the highest serum levels of sB7-H4 and B7-H4 mRNA expression in the placenta were observed in early-onset PE. Significant higher serum levels of sB7-H4 and B7-H4 mRNA expression in the placenta were observed in women with early-onset PE (P = .01 and P = .006, respectively) and late-onset PE (P = .03 and P = .004, respectively) compared to healthy controls, but not compared to FGR.

CONCLUSION

sB7-H4 is involved in the regulation of immune tolerance in women with PE in the third trimester. In the first trimester of pregnancy, sB7-H4 might serve as a predictive immunological biomarker for women who are at elevated risk of developing PE.

FLT1 and transcriptome-wide polyadenylation site (PAS) analysis in preeclampsia

Maternal symptoms of preeclampsia (PE) are primarily driven by excess anti-angiogenic factors originating from the placenta. Chief among these are soluble Flt1 proteins (sFlt1s) produced from alternatively polyadenylated mRNA isoforms. Here we used polyadenylation site sequencing (PAS-Seq) of RNA from normal and PE human placentae to interrogate transcriptome-wide gene expression and alternative polyadenylation signatures associated with early-onset PE (EO-PE; symptom onset < 34 weeks) and late-onset PE (LO-PE; symptom onset > 34 weeks) cohorts. While we observed no general shift in alternative polyadenylation associated with PE, the EO-PE and LO-PE cohorts do exhibit gene expression profiles distinct from both each other and from normal placentae. The only two genes upregulated across all transcriptome-wide PE analyses to date (microarray, RNA-Seq and PAS-Seq) are NRIP1 (RIP140), a transcriptional co-regulator linked to metabolic syndromes associated with obesity, and Flt1. Consistent with sFlt1 overproduction being a significant driver of clinical symptoms, placental Flt1 mRNA levels strongly correlate with maternal blood pressure. For Flt1, just three mRNA isoforms account for > 94% of all transcripts, with increased transcription of the entire locus driving Flt1 upregulation in both EO-PE and LO-PE. These three isoforms thus represent potential targets for therapeutic RNA interference (RNAi) in both early and late presentations.

The prediction of late-onset preeclampsia: Results from a longitudinal proteomics study

BACKGROUND

Late-onset preeclampsia is the most prevalent phenotype of this syndrome; nevertheless, only a few biomarkers for its early diagnosis have been reported. We sought to correct this deficiency using a high through-put proteomic platform.

METHODS

A case-control longitudinal study was conducted, including 90 patients with normal pregnancies and 76 patients with late-onset preeclampsia (diagnosed at ≥34 weeks of gestation). Maternal plasma samples were collected throughout gestation (normal pregnancy: 2-6 samples per patient, median of 2; late-onset preeclampsia: 2-6, median of 5). The abundance of 1,125 proteins was measured using an aptamers-based proteomics technique. Protein abundance in normal pregnancies was modeled using linear mixed-effects models to estimate mean abundance as a function of gestational age. Data was then expressed as multiples of-the-mean (MoM) values in normal pregnancies. Multi-marker prediction models were built using data from one of five gestational age intervals (8-16, 16.1-22, 22.1-28, 28.1-32, 32.1-36 weeks of gestation). The predictive performance of the best combination of proteins was compared to placental growth factor (PIGF) using bootstrap.

RESULTS

1) At 8-16 weeks of gestation, the best prediction model included only one protein, matrix metalloproteinase 7 (MMP-7), that had a sensitivity of 69% at a false positive rate (FPR) of 20% (AUC = 0.76); 2) at 16.1-22 weeks of gestation, MMP-7 was the single best predictor of late-onset preeclampsia with a sensitivity of 70% at a FPR of 20% (AUC = 0.82); 3) after 22 weeks of gestation, PlGF was the best predictor of late-onset preeclampsia, identifying 1/3 to 1/2 of the patients destined to develop this syndrome (FPR = 20%); 4) 36 proteins were associated with late-onset preeclampsia in at least one interval of gestation (after adjustment for covariates); 5) several biological processes, such as positive regulation of vascular endothelial growth factor receptor signaling pathway, were perturbed; and 6) from 22.1 weeks of gestation onward, the set of proteins most predictive of severe preeclampsia was different from the set most predictive of the mild form of this syndrome.

CONCLUSIONS

Elevated MMP-7 early in gestation (8-22 weeks) and low PlGF later in gestation (after 22 weeks) are the strongest predictors for the subsequent development of late-onset preeclampsia, suggesting that the optimal identification of patients at risk may involve a two-step diagnostic process.

Altered feto-placental vascularization, feto-placental malperfusion and fetal growth restriction in mice with Egfl7 loss of function

EGFL7 is a secreted angiogenic factor produced by embryonic endothelial cells. To understand its role in placental development, we established a novel Egfl7 knockout mouse. The mutant mice have gross defects in chorioallantoic branching morphogenesis and placental vascular patterning. Microangiography and 3D imaging revealed patchy perfusion of Egfl7^-/- placentas marked by impeded blood conductance through sites of narrowed vessels. Consistent with poor feto-placental perfusion, Egfl7 knockout resulted in reduced placental weight and fetal growth restriction. The placentas also showed abnormal fetal vessel patterning and over 50% reduction in fetal blood space. In vitro, placental endothelial cells were deficient in migration, cord formation and sprouting. Expression of genes involved in branching morphogenesis, Gcm1, Syna and Synb, and in patterning of the extracellular matrix, Mmrn1, were temporally dysregulated in the placentas. Egfl7 knockout did not affect expression of the microRNA embedded within intron 7. Collectively, these data reveal that Egfl7 is crucial for placental vascularization and embryonic growth, and may provide insight into etiological factors underlying placental pathologies associated with intrauterine growth restriction, which is a significant cause of infant morbidity and mortality.

Gene expression in term placentas is regulated more by spinal or epidural anesthesia than by late-onset preeclampsia or gestational diabetes mellitus

Pre-eclampsia (PE) and gestational diabetes mellitus (GDM) are common complications of pregnancy, but the mechanisms underlying these disorders remain unclear. The aim was to identify the extent of altered gene expression in term placentas from pregnant women with late-onset PE and GDM compared to controls. RNAseq identified few significantly differentially regulated genes in placental biopsies between PE, GDM, or uncomplicated pregnancy (n = 10 each group). Five genes were altered in placentas from PE including 4 non-coding genes and Angiopoietin 2 (ANGPT2). No genes were significantly regulated by GDM. In contrast, many genes were significantly regulated by fetal, maternal and delivery-specific variables, particularly spinal and epidural anesthesia. We selected ANGPT2 and Chemokine (C-X-C motif) ligand 14 (CXCL14) to test with qPCR in a larger set of placentas (n = 475) and found no differences between the groups. However, regression analysis revealed a stronger association between placental ANGPT2 and CXCL14 mRNA expression and fetal, maternal and delivery-specific variables than diagnostic group. To conclude, the gene expression in term placentas are highly affected by fetal, maternal and delivery specific variables. Few regulated genes were found in late-onset PE and GDM placentas, which may suggest that these conditions could be more affected by maternal factors.

Gene expression profiling reveals different molecular patterns in G-protein coupled receptor signaling pathways between early- and late-onset preeclampsia

Early-onset preeclampsia and late-onset preeclampsia have been regarded as two different phenotypes with heterogeneous manifestations; To gain insights into the pathogenesis of the two traits, we analyzed the gene expression profiles in preeclamptic placentas. A whole genome-wide microarray was used to determine the gene expression profiles in placental tissues from patients with early-onset (n = 7; <34 weeks), and late-onset (n = 8; >36 weeks) preeclampsia and their controls who delivered preterm (n = 5; <34 weeks) or at term (n = 5; >36 weeks). Genes were termed differentially expressed if they showed a fold-change ≥ 2 and q-value < 0.05. Quantitative real-time reverse transcriptase PCR was used to verify the results. Western blotting was performed to verify the expressions of secreted genes at the protein level.

RESULTS

Six hundred twenty-seven genes were differentially expressed in early-compared with late-onset preeclampsia (177 genes were up-regulated and 450 were down-regulated). Gene ontology analysis identified significant alterations in several biological processes; the top two were immune response and cell surface receptor linked signal transduction. Among the cell surface receptor linked signal transduction-related, differentially expressed genes, those involved in the G-protein coupled receptor protein signaling pathway were significantly enriched. G-protein coupled receptor signaling pathway related genes, such as GPR124 and MRGPRF, were both found to be down-regulated in early-onset preeclampsia. The results were consistent with those of western blotting that the abundance of GPR124 was lower in early-onset compared with late-onset preeclampsia. The different gene expression profiles reflect the different levels of transcription regulation between the two conditions and supported the hypothesis that they are separate disease entities. Moreover, the G-protein coupled receptor signaling pathway related genes may contribute to the mechanism underlying early- and late-onset preeclampsia.

Extensive shift in placental transcriptome profile in preeclampsia and placental origin of adverse pregnancy outcomes

One in five pregnant women suffer from gestational complications, prevalently driven by placental malfunction. Using RNASeq, we analyzed differential placental gene expression in cases of normal gestation, late-onset preeclampsia (LO-PE), gestational diabetes (GD) and pregnancies ending with the birth of small-for-gestational-age (SGA) or large-for-gestational-age (LGA) newborns (n = 8/group). In all groups, the highest expression was detected for small noncoding RNAs and genes specifically implicated in placental function and hormonal regulation. The transcriptome of LO-PE placentas was clearly distinct, showing statistically significant (after FDR) expressional disturbances for hundreds of genes. Taqman RT-qPCR validation of 45 genes in an extended sample (n = 24/group) provided concordant results. A limited number of transcription factors including LRF, SP1 and AP2 were identified as possible drivers of these changes. Notable differences were detected in differential expression signatures of LO-PE subtypes defined by the presence or absence of intrauterine growth restriction (IUGR). LO-PE with IUGR showed higher correlation with SGA and LO-PE without IUGR with LGA placentas. Whereas changes in placental transcriptome in SGA, LGA and GD cases were less prominent, the overall profiles of expressional disturbances overlapped among pregnancy complications providing support to shared placental responses. The dataset represent a rich catalogue for potential biomarkers and therapeutic targets.

Gestational tissue transcriptomics in term and preterm human pregnancies: a systematic review and meta-analysis

BACKGROUND

Preterm birth (PTB), or birth before 37 weeks of gestation, is the leading cause of newborn death worldwide. PTB is a critical area of scientific study not only due to its worldwide toll on human lives and economies, but also due to our limited understanding of its pathogenesis and, therefore, its prevention. This systematic review and meta-analysis synthesizes the landscape of PTB transcriptomics research to further our understanding of the genes and pathways involved in PTB subtypes.

METHODS

We evaluated published genome-wide pregnancy studies across gestational tissues and pathologies, including those that focus on PTB, by performing a targeted PubMed MeSH search and systematically reviewing all relevant studies.

RESULTS

Our search yielded 2,361 studies on gestational tissues including placenta, decidua, myometrium, maternal blood, cervix, fetal membranes (chorion and amnion), umbilical cord, fetal blood, and basal plate. Selecting only those original research studies that measured transcription on a genome-wide scale and reported lists of expressed genetic elements identified 93 gene expression, 21 microRNA, and 20 methylation studies. Although 30 % of all PTB cases are due to medical indications, 76 % of the preterm studies focused on them. In contrast, only 18 % of the preterm studies focused on spontaneous onset of labor, which is responsible for 45 % of all PTB cases. Furthermore, only 23 of the 10,993 unique genetic elements reported to be transcriptionally active were recovered 10 or more times in these 134 studies. Meta-analysis of the 93 gene expression studies across 9 distinct gestational tissues and 29 clinical phenotypes showed limited overlap of genes identified as differentially expressed across studies.

CONCLUSIONS

Overall, profiles of differentially expressed genes were highly heterogeneous both between as well as within clinical subtypes and tissues as well as between studies of the same clinical subtype and tissue. These results suggest that large gaps still exist in the transcriptomic study of specific clinical subtypes as well in the generation of the transcriptional profile of well-studied clinical subtypes; understanding the complex landscape of prematurity will require large-scale, systematic genome-wide analyses of human gestational tissues on both understudied and well-studied subtypes alike.

Association between ACVR2A and early-onset preeclampsia: replication study in a Northeastern Brazilian population

INTRODUCTION

Preeclampsia is a complex and heterogeneous disease with increased risk of maternal mortality, especially for earlier gestational onset. There is a great inconsistency regarding the genetics of preeclampsia across the literature. The gene Activin A receptor, type IIA (ACVR2A), was reported as associated to preeclampsia in Australian/New Zealand and Norwegian populations. The goal of this study was to validate this genetic association in a Brazilian population.

METHODS

We performed a case-control study using 693 controls and 613 cases (443 preeclampsia, 64 eclampsia and 106 HELLP syndrome), from a Northeastern Brazilian population. Five single nucleotide polymorphisms (SNPs) in ACVR2A were tested for association through multiple logistic regression models.

RESULTS

There was no statistical association with preeclampsia (per se), eclampsia or HELLP. However, by grouping preeclampsia in accordance to the gestational age at delivery, SNPs rs1424954 (OR = 1.86; 95% CI, 1.25-2.78; p = 0.002) and rs1014064 (OR = 1.77; 95% CI, 1.21-2.60; p = 0.004) were significantly associated with early onset preeclampsia (gestational age ≤ 34 weeks). The risk haplotype had a frequency of 0.468 in early preeclampsia compared to 0.316 in controls (p = 0.0008 and permuted p = 0.002).

DISCUSSION

Activin A receptors are important in decidualization, trophoblast invasion and placentation processes during pregnancy. The gene ACVR2A was associated with the more severe early onset preeclampsia. This finding supports the hypothesis of different pathogenic mechanisms contributing to the early- and late-onset preeclampsia.

Placental expression of proBNP/NT-proBNP and plasma levels of NT-proBNP in early- and late-onset preeclampsia

BACKGROUND

Levels of plasma N-terminal pro B-type natriuretic peptide (NT-proBNP) are elevated in preeclampsia. In this study, the possibility that the placenta produces and releases proBNP/NT-proBNP was explored. Plasma levels of NT-proBNP in early- and late-onset preeclampsia were also measured.

METHODS

Placental proBNP mRNA in early-onset preeclampsia (n = 7), late-onset preeclampsia (n = 8), and controls of similar gestational age (n = 10) was assessed by quantitative real-time polymerase chain reaction. ProBNP/NT-proBNP protein was studied in placental samples with immunohistochemistry (n = 8) and tissue culture (n = 2). Plasma levels of NT-proBNP were measured in early-onset preeclampsia (n = 18), late-onset preeclampsia (n = 20), and relevant controls (n = 36).

RESULTS

Transcripts of proBNP mRNA were found in 20 out of 25 samples, there were no differences in expression between the groups. ProBNP/NT-proBNP protein was observed in maternal spiral arteries and in syncytiotrophoblasts in all placental samples. After placental tissue culture, there were measurable amounts of NT-proBNP in the culture media. Women with both early- (365 [14-9815] pg/ml) and late-onset preeclampsia (176 [33-2547] pg/ml) had higher levels of NT-proBNP than their controls (P < 0.001). There was a tendency toward higher levels of NT-proBNP in women with early-onset preeclampsia than in women with late-onset preeclampsia (P = 0.057).

CONCLUSION

The results indicate possible placental production and release of proBNP/NT-proBNP into the maternal circulation.

Impaired adenosine-mediated angiogenesis in preeclampsia: potential implications for fetal programming

Preeclampsia is a pregnancy-specific syndrome, defined by such clinical hallmarks as the onset of maternal hypertension and proteinuria after 20 weeks of gestation. The syndrome is also characterized by impaired blood flow through the utero-placental circulation and relative placental ischemia, which in turn, may generate feto-placental endothelial dysfunction. Endothelial dysfunction in offspring born from preeclamptic pregnancies has been associated with an increased risk of cardiovascular disease, including hypertension, later in life. Interestingly, diminished endothelial function, manifested by low angiogenic capacity, leads to hypertension in animal studies. Recently, we have shown that the adenosine receptor A_2A/nitric oxide/vascular endothelial growth factor axis is reduced in human umbilical vein endothelial cells derived from preeclamptic pregnancies, an effect correlated with gestational age at onset of preeclampsia. We and others suggested that impaired vascular function might be associated with high cardiovascular risk in offspring exposed to pregnancy diseases. However, we are not aware of any studies that examine impaired adenosine-mediated angiogenesis as a possible link to hypertension in offspring born from preeclamptic pregnancies. In this review, we present evidence supporting the hypothesis that reduced adenosine-mediated angiogenesis during preeclamptic pregnancies might be associated with development of hypertension in the offspring.

Novel expression of EGFL7 in placental trophoblast and endothelial cells and its implication in preeclampsia

The mammalian placenta is the site of nutrient and gas exchange between the mother and fetus, and is comprised of two principal cell types, trophoblasts and endothelial cells. Proper placental development requires invasion and differentiation of trophoblast cells, together with coordinated fetal vasculogenesis and maternal vascular remodeling. Disruption in these processes can result in placental pathologies such as preeclampsia (PE), a disease characterized by late gestational hypertension and proteinuria. Epidermal Growth Factor Like Domain 7 (EGFL7) is a largely endothelial-restricted secreted factor that is critical for embryonic vascular development, and functions by modulating the Notch signaling pathway. However, the role of EGFL7 in placental development remains unknown. In this study, we use mouse models and human placentas to begin to understand the role of EGFL7 during normal and pathological placentation. We show that Egfl7 is expressed by the endothelium of both the maternal and fetal vasculature throughout placental development. Importantly, we uncovered a previously unknown site of EGFL7 expression in the trophoblast cell lineage, including the trophectoderm, trophoblast stem cells, and placental trophoblasts. Our results demonstrate significantly reduced Egfl7 expression in human PE placentas, concurrent with a downregulation of Notch target genes. Moreover, using the BPH/5 mouse model of PE, we show that the downregulation of Egfl7 in compromised placentas occurs prior to the onset of characteristic maternal signs of PE. Together, our results implicate Egfl7 as a possible factor in normal placental development and in the etiology of PE.

Fetal–maternal communication: the role of Notch signalling in embryo implantation

The establishment of a successful pregnancy requires the implantation of a competent blastocyst into a ‘receptive’ endometrium, facilitating the formation of a functional placenta. Inadequate or inappropriate implantation and placentation is a major reason for infertility and is thought to lead to first-trimester miscarriage, placental insufficiency and other obstetric complications. Blastocyst–endometrial interactions are critical for implantation and placental formation. The Notch signalling family is a receptor–ligand family that regulates cellular processes as diverse as proliferation, apoptosis, differentiation, invasion and adhesion. Notch signalling is achieved via cell–cell interaction; thus, via Notch, cells can have direct effects on the fate of their neighbours. Recently, a number of studies have identified Notch receptors and ligands in the endometrium, blastocyst and placenta. This review collates current knowledge of this large receptor–ligand family and explores the role of Notch signalling during implantation and placentation, drawing on information from both human and animal studies. Overall, the evidence suggests that Notch signalling is a critical component of fetal–maternal communication during implantation and placentation and that abnormal Notch expression is associated with impaired placentation and pre-eclampsia.

The common variant rs11646213 is associated with preeclampsia in Han Chinese women

Background

Preeclampsia, characterized by hypertension and proteinuria, is a multifactorial disease caused by complex interactions between environmental and genetic factors. A recent genome-wide association study of blood pressure reported an association between hypertension and rs11646213. This study evaluated the association between preeclampsia and rs11646213.

Methods

A total of 454 cases and 460 controls were recruited to participate in this study. The single nucleotide polymorphism (SNP) rs11646213 was genotyped by polymerase chain reaction (PCR) and direct sequencing.

Results

The allele frequency of rs11646213 was significantly different between the preeclampsia and control groups (P = 0.017, OR = 1.36, 95% CI = 1.06–1.76). Differences were particularly significant in the severe preeclampsia subgroup (P = 0.002, OR = 1.54, 95% CI = 1.17–2.03) and the early-onset preeclampsia subgroup (P = 0.004, OR = 1.57, 95% CI = 1.16–2.13). Genotyping analysis showed that the T allele of rs11646213 could confer a risk for preeclampsia, severe preeclampsia and early-onset preeclampsia.

Conclusions

Rs11646213 upstream of the CDH13 gene is associated with preeclampsia in Han Chinese women.

A lesson for cancer research: placental microarray gene analysis in preeclampsia

Tumor progression and pregnancy share many common features, such as immune tolerance and invasion. The invasion of trophoblasts in the placenta into the uterine wall is essential for fetal development, and is thus precisely regulated. Its deregulation has been implicated in preeclampsia, a leading cause for maternal and perinatal mortality and morbidity. Pathogenesis of preeclampsia remains to be defined. Microarray-based gene profiling has been widely used for identifying genes responsible for preeclampsia. In this review, we have summarized the recent data from the microarray studies with preeclamptic placentas. Despite the complex of gene signatures, suggestive of the heterogeneity of preeclampsia, these studies identified a number of differentially expressed genes associated with preeclampsia. Interestingly, most of them have been reported to be tightly involved in tumor progression. We have discussed these interesting genes and analyzed their potential molecular functions in preeclampsia, compared with their roles in malignancy development. Further investigations are warranted to explore the involvement in molecular network of each identified gene, which may provide not only novel strategies for prevention and therapy for preeclampsia but also a better understanding of cancer cells. The trophoblastic cells, with their capacity for proliferation and differentiation, apoptosis and survival, migration, angiogenesis and immune modulation by exploiting similar molecular pathways, make them a compelling model for cancer research.

Circulating mRNA for epidermal growth factor-like domain 7 (EGFL7) in maternal blood and early intrauterine growth restriction. A preliminary analysis

OBJECTIVE

To evaluate the alteration in epidermal growth factor-like domain 7 (EGFL7) mRNA expression in maternal blood from pregnancies affected by early-onset intrauterine growth restriction (IUGR) at 20-24 weeks.

METHOD

Case-control study encompassing six women with pregnancies affected by IUGR (cases) matched in a 1 : 7 ratio for gestational age and fetal gender with 42 controls. We quantified EGFL7 mRNA expression in normal and IUGR patients. Matched rank-sum analysis and multiples of median were used to evaluate differences of the marker of interest between cases and controls. Spearman regression analysis was used to correlate the estimated fetal weight at blood sampling with the EGFL7 mRNA values.

RESULTS

The mean observed rank in the IUGR group was significantly higher than that of controls (6.67 vs 4.19, p = 0.01). Pregnancies affected with IUGR exhibited 1.70-fold higher levels of maternal EGFL7 mRNA compared with matched controls (p = 0.014). EGFL7 mRNA values were inversely correlated with estimated fetal weight (Spearman's ρ = -0.429, p = 0.198).

CONCLUSION

Early IUGR at 20-24 weeks' gestation is associated with higher values of EGFL7 expression in maternal plasma.

Impaired A2A adenosine receptor/nitric oxide/VEGF signaling pathway in fetal endothelium during late- and early-onset preeclampsia

To investigate whether fetal endothelial cell proliferation and migration are modulated by the A2A adenosine receptor (A2AAR), nitric oxide (NO) and the vascular endothelial growth factor (VEGF) signaling pathway, we isolated human umbilical vein endothelial cells from normal pregnancy (n = 23), preterm delivery (n = 4), and late-onset (LOPE, n = 10) and early-onset preeclampsia (EOPE, n = 8). We used the non-selective adenosine receptor agonist (NECA) and the selective agonist (CGS-21680) and/or selective antagonist (ZM-241385) for A2AAR. Also, the nitric oxide synthase (NOS) inhibitor, L-NAME, was used in co-incubation with CGS-21680. Compared to normal pregnancy, EOPE exhibited low cell proliferation and migration associated with reduced expressions of A2AAR and VEGF and NO synthesis (i.e., total and phosphorylated serine(1177) endothelial NOS and nitrite formation). In contrast, LOPE exhibited the opposite behavior in all these markers compared to normal pregnancy or EOPE. Cell proliferation and migration were increased by CGS-21680 (or NECA) in all analyzed groups (EOPE>LOPE>normal pregnancy) compared to their respective basal conditions, an effect that was associated with high NO and VEGF synthesis and blocked by ZM-241385 with significantly different IC50 for each group (EOPE>LOPE>normal pregnancy). The differences seem independent of gestational age. L-NAME blocked the CGS-21680-mediated cell proliferation and migration in normal pregnancy and LOPE (IC50 = 36.2 ± 2.5 and 8.6 ± 2.2 nM, respectively) as well as the VEGF expression in normal pregnancy. Therefore, the A2AAR/NO/VEGF signaling pathway exhibits a pro-angiogenic effect in normal pregnancies and LOPE, whereas impairment in this pathway seems related to the reduced angiogenic capacity of the fetal endothelium in EOPE.