Landscape of transcriptional deregulations in the preeclamptic placenta

Placental transcriptome variation associated with season, location, and urinary prenatal pyrethroid metabolites of Thai farm-working women

Prenatal exposure to pyrethroids is linked to adverse health effects in early life and proper placental function is critical to fetal development. This study explores the impact of prenatal pyrethroid exposure, as well as factors impacting exposure and effect, on the placental transcriptome, to understand pyrethroid exposures' relationship to placental function. The study of Asian Women and their Offspring's Development and Environmental Exposures (SAWASDEE) recruited pregnant farm-working women from two agricultural districts in the Chiang Mai province of Thailand between 2017 and 2019. This cohort was predominantly exposed to cypermethrin (type II), alongside pyrethroids such as cyfluthrin (type II) and permethrin (type I). In 253 participants, maternal urinary pyrethroid metabolites, 3-phenoxybenzoic acid (PBA), cis-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (CDCCA), and trans-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (TDCCA) were measured in early, middle, and late pregnancy and adjusted for urinary creatinine. The placental transcriptome was analyzed using RNA-Seq. Using generalized linear regression, we identified differentially expressed genes (DEGs) associated with the sum of each metabolite across pregnancy, as well as those associated with location of residence and season of birth. Pathway and upstream transcription factor analyses were performed to examine potential mechanisms associated with DEGs. Notably, TDCCA and CDCCA levels peaked in late pregnancy, with significant regional differences, particularly higher levels in the Fang region. Placental gene expression analysis showed no DEGs associated with individual metabolites at FDR<0.05. However, 251 DEGs by location, implicating immune response and oxidative phosphorylation pathways, were identified, while season of birth was associated with 2585 DEGs, over-represented in fibrosis signaling and metabolism pathways. Finally, transcription factor analysis identified 226 and 282 transcription factors associated with location and season, respectively, related to cell proliferation, differentiation, and the immune system. These alterations may have significant implications for fetal development and other pathologic processes, highlighting the importance of monitoring environmental exposures during pregnancy.

Integrative profiling of extrachromosomal circular DNA in placenta and maternal plasma provides insights into the biology of fetal growth restriction and reveals potential biomarkers

Introduction: Fetal growth restriction (FGR) is a placenta-mediated pregnancy complication that predisposes fetuses to perinatal complications. Maternal plasma cell-free DNA harbors DNA originating from placental trophoblasts, which is promising for the prenatal diagnosis and prediction of pregnancy complications. Extrachromosomal circular DNA (eccDNA) is emerging as an ideal biomarker and target for several diseases. Methods: We utilized eccDNA sequencing and bioinformatic pipeline to investigate the characteristics and associations of eccDNA in placenta and maternal plasma, the role of placental eccDNA in the pathogenesis of FGR, and potential plasma eccDNA biomarkers of FGR. Results: Using our bioinformatics pipelines, we identified multi-chromosomal-fragment and single-fragment eccDNA in placenta, but almost exclusively single-fragment eccDNA in maternal plasma. Relative to that in plasma, eccDNA in placenta was larger and substantially more abundant in exons, untranslated regions, promoters, repetitive elements [short interspersed nuclear elements (SINEs)/Alu, SINEs/mammalian-wide interspersed repeats, long terminal repeats/endogenous retrovirus-like elements, and single recognition particle RNA], and transcription factor binding motifs. Placental multi-chromosomal-fragment eccDNA was enriched in confident enhancer regions predicted to pertain to genes in apoptosis, energy, cell growth, and autophagy pathways. Placental eccDNA-associated genes whose abundance differed between the FGR and control groups were associated with immunity-related gene ontology (GO) terms. The combined analysis of plasma and placental eccDNA-associated genes in the FGR and control groups led to the identification of potential biomarkers that were assigned to the GO terms of the epigenetic regulation of gene expression and nutrient-related processes, respectively. Conclusion: Together, our results highlight links between placenta functions and multi-chromosomal-fragment and single-fragment eccDNA. The integrative analysis of placental and plasma eccDNA confirmed the potential of these molecules as disease-specific biomarkers of FGR.

A Data-Mining Approach to Identify NF-kB-Responsive microRNAs in Tissues Involved in Inflammatory Processes: Potential Relevance in Age-Related Diseases

The nuclear factor NF-kB is the master transcription factor in the inflammatory process by modulating the expression of pro-inflammatory genes. However, an additional level of complexity is the ability to promote the transcriptional activation of post-transcriptional modulators of gene expression as non-coding RNA (i.e., miRNAs). While NF-kB’s role in inflammation-associated gene expression has been extensively investigated, the interplay between NF-kB and genes coding for miRNAs still deserves investigation. To identify miRNAs with potential NF-kB binding sites in their transcription start site, we predicted miRNA promoters by an in silico analysis using the PROmiRNA software, which allowed us to score the genomic region’s propensity to be miRNA cis-regulatory elements. A list of 722 human miRNAs was generated, of which 399 were expressed in at least one tissue involved in the inflammatory processes. The selection of “high-confidence” hairpins in miRbase identified 68 mature miRNAs, most of them previously identified as inflammamiRs. The identification of targeted pathways/diseases highlighted their involvement in the most common age-related diseases. Overall, our results reinforce the hypothesis that persistent activation of NF-kB could unbalance the transcription of specific inflammamiRNAs. The identification of such miRNAs could be of diagnostic/prognostic/therapeutic relevance for the most common inflammatory-related and age-related diseases.

ANP promotes HTR-8/SVneo cell invasion by upregulating protein kinase N 3 via autophagy inhibition

Preeclampsia is a gestational disease characterized by two major pathological changes-shallow trophoblast invasion and impaired spiral artery remodeling. Atrial natriuretic peptide (ANP) is a kind of peptide hormone that regulates blood pressure, while the lack of active ANP participates in preeclampsia pathogenesis. However, the underlying mechanism of how ANP modulates trophoblasts function remains unclarified. Here, we performed isobaric tags for relative and absolute quantification (iTRAQ) in ANP-treated HTR-8/SVneo cells and identified Protein Kinase 3 (PKN3) as the downstream factor of ANP, which was downregulated in preeclamptic placenta. Chromatin immunoprecipitation analysis and luciferase assays showed that NFYA was one of the transcription factors for the PKN3 promoter, which was also regulated by ANP treatment in HTR-8/SVneo cells. Transmission electron microscopy and Western Blotting in HTR-8/SVneo cells indicated that ANP inhibited autophagy via AMPK-mTORC1 signaling, while excess autophagy was observed in preeclamptic placenta. The increased expression of PKN3 and enhanced cell invasion ability in HTR-8/SVneo cells induced by ANP could be abolished by autophagy activation or transfection with PKN3 shRNA or NFYA shRNA or NPR-A shRNA via regulating the invasion-related genes and the epithelial mesenchymal transition molecules. Our results demonstrated that ANP could enhance trophoblast invasion by upregulating PKN3 via NFYA promotion through autophagy inhibition in an AMPK/mTORC1 signaling-dependent manner.

Histopathologic and Transcriptomic Profiling Identifies Novel Trophoblast Defects in Patients With Preeclampsia and Maternal Vascular Malperfusion

Preeclampsia (PE) is a heterogeneous disease for which the current clinical classification system is based on the presence or absence of specific clinical features. PE-associated placentas also show heterogeneous findings on pathologic examination, suggesting that further subclassification is possible. We combined clinical, pathologic, immunohistochemical, and transcriptomic profiling of placentas to develop integrated signatures for multiple subclasses of PE. In total, 303 PE and 1388 nonhypertensive control placentas were included. We found that maternal vascular malperfusion (MVM) in the placenta was associated with preterm PE with severe features and with small-for-gestational-age neonates. Interestingly, PE placentas with either MVM or no histologic pattern of injury showed a linear decrease in proliferative (p63+) cytotrophoblast per villous area with increasing gestational age, similar to placentas obtained from the nonhypertensive patient cohort; however, PE placentas with fetal vascular malperfusion or villitis of unknown etiology lost this phenotype. This is mainly because of cases of fetal vascular malperfusion in placentas of patients with preterm PE and villitis of unknown etiology in placentas of patients with term PE, which are associated with a decrease or increase, respectively, in the cytotrophoblast per villous area. Finally, a transcriptomic analysis identified pathways associated with hypoxia, inflammation, and reduced cell proliferation in PE-MVM placentas and further subclassified this group into extravillous trophoblast-high and extravillous trophoblast-low PE, confirmed using an immunohistochemical analysis of trophoblast lineage-specific markers. Our findings suggest that within specific histopathologic patterns of placental injury, PE can be subclassified based on specific cellular and molecular defects, allowing the identification of pathways that may be targeted for diagnostic and therapeutic purposes.

Co-alterations of circadian clock gene transcripts in human placenta in preeclampsia

Pre-eclampsia (PE) is a hypertensive condition that occurs during pregnancy and complicates up to 4% of pregnancies. PE exhibits several circadian-related characteristics, and the placenta possesses a functioning molecular clock. We examined the associations of 17 core circadian gene transcripts in placenta with PE vs. non-PE (a mixture of pregnant women with term, preterm, small-for-gestational-age, or chorioamnionitis) using two independent gene expression datasets: GSE75010-157 (80 PE vs. 77 non-PE) and GSE75010-173 (77 PE and 96 non-PE). We found a robust difference in circadian gene expression between PE and non-PE across the two datasets, where CRY1 mRNA increases and NR1D2 and PER3 transcripts decrease in PE placenta. Gene set variation analysis revealed an interplay between co-alterations of circadian clock genes and PE with altered hypoxia, cell migration/invasion, autophagy, and membrane trafficking pathways. Using human placental trophoblast HTR-8 cells, we show that CRY1/2 and NR1D1/2 regulate trophoblast migration. A subgroup study including only term samples demonstrated that CLOCK, NR1D2, and PER3 transcripts were simultaneously decreased in PE placenta, a finding supported by CLOCK protein downregulation in an independent cohort of human term PE placenta samples. These findings provide novel insights into the roles of the molecular clock in the pathogenesis of PE.

Regulation of Placental Efflux Transporters during Pregnancy Complications

The placenta is essential for regulating the exchange of solutes between the maternal and fetal circulations. As a result, the placenta offers support and protection to the developing fetus by delivering crucial nutrients and removing waste and xenobiotics. ATP-binding cassette transporters, including multidrug resistance protein 1, multidrug resistance-associated proteins, and breast cancer resistance protein, remove chemicals through active efflux and are considered the primary transporters within the placental barrier. Altered transporter expression at the barrier could result in fetal exposure to chemicals and/or accumulation of xenobiotics within trophoblasts. Emerging data demonstrate that expression of these transporters is changed in women with pregnancy complications, suggesting potentially compromised integrity of placental barrier function. The purpose of this review is to summarize the regulation of placental efflux transporters during medical complications of pregnancy, including 1) placental inflammation/infection and chorioamnionitis, 2) hypertensive disorders of pregnancy, 3) metabolic disorders including gestational diabetes and obesity, and 4) fetal growth restriction/altered fetal size for gestational age. For each disorder, we review the basic pathophysiology and consider impacts on the expression and function of placental efflux transporters. Mechanisms of transporter dysregulation and implications for fetal drug and toxicant exposure are discussed. Understanding how transporters are up- or downregulated during pathology is important in assessing possible exposures of the fetus to potentially harmful chemicals in the environment as well as the disposition of novel therapeutics intended to treat placental and fetal diseases. SIGNIFICANCE STATEMENT: Diseases of pregnancy are associated with reduced expression of placental barrier transporters that may impact fetal pharmacotherapy and exposure to dietary and environmental toxicants.

BCL6, a key oncogene, in the placenta, pre-eclampsia and endometriosis

BACKGROUND

The key oncogene B-cell lymphoma 6 (BCL6) drives malignant progression by promoting proliferation, overriding DNA damage checkpoints and blocking cell terminal differentiation. However, its functions in the placenta and the endometrium remain to be defined.

OBJECTIVE AND RATIONALE

Recent studies provide evidence that BCL6 may play various roles in the human placenta and the endometrium. Deregulated BCL6 might be related to the pathogenesis of pre-eclampsia (PE) as well as endometriosis. In this narrative review, we aimed to summarize the current knowledge regarding the pathophysiological role of BCL6 in these two reproductive organs, discuss related molecular mechanisms, and underline associated research perspectives.

SEARCH METHODS

We conducted a comprehensive literature search using PubMed for human, animal and cellular studies published until October 2021 in the following areas: BCL6 in the placenta, in PE and in endometriosis, in combination with its functions in proliferation, fusion, migration, invasion, differentiation, stem/progenitor cell maintenance and lineage commitment.

OUTCOMES

The data demonstrate that BCL6 is important in cell proliferation, survival, differentiation, migration and invasion of trophoblastic cells. BCL6 may have critical roles in stem/progenitor cell survival and differentiation in the placenta and the endometrium. BCL6 is aberrantly upregulated in pre-eclamptic placentas and endometriotic lesions through various mechanisms, including changes in gene transcription and mRNA translation as well as post-transcriptional/translational modifications. Importantly, increased endometrial BCL6 is considered to be a non-invasive diagnostic marker for endometriosis and a predictor for poor outcomes of IVF. These data highlight that BCL6 is crucial for placental development and endometrium homeostasis, and its upregulation is associated with the pathogenesis of PE, endometriosis and infertility.

WIDER IMPLICATIONS

The lesson learned from studies of the key oncogene BCL6 reinforces the notion that numerous signaling pathways and regulators are shared by tumors and reproductive organs. Their alteration may promote the progression of malignancies as well as the development of gestational and reproductive disorders.

Epigenetic processes during preeclampsia and effects on fetal development and chronic health

Preeclampsia (PE), the leading cause of maternal and fetal morbidity and mortality, is associated with poor fetal growth, intrauterine growth restriction (IUGR) and low birth weight (LBW). Offspring of women who had PE are at increased risk for cardiovascular (CV) disease later in life. However, the exact etiology of PE is unknown. Moreover, there are no effective interventions to treat PE or alleviate IUGR and the developmental origins of chronic disease in the offspring. The placenta is critical to fetal growth and development. Epigenetic regulatory processes such as histone modifications, microRNAs and DNA methylation play an important role in placental development including contributions to the regulation of trophoblast invasion and remodeling of the spiral arteries. Epigenetic processes that lead to changes in placental gene expression in PE mediate downstream effects that contribute to the development of placenta dysfunction, a critical mediator in the onset of PE, impaired fetal growth and IUGR. Therefore, this review will focus on epigenetic processes that contribute to the pathogenesis of PE and IUGR. Understanding the epigenetic mechanisms that contribute to normal placental development and the initiating events in PE may lead to novel therapeutic targets in PE that improve fetal growth and mitigate increased CV risk in the offspring.

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.

Alternative splicing in normal and pathological human placentas is correlated to genetic variants

Two major obstetric diseases, preeclampsia (PE), a pregnancy-induced endothelial dysfunction leading to hypertension and proteinuria, and intra-uterine growth-restriction (IUGR), a failure of the fetus to acquire its normal growth, are generally triggered by placental dysfunction. Many studies have evaluated gene expression deregulations in these diseases, but none has tackled systematically the role of alternative splicing. In the present study, we show that alternative splicing is an essential feature of placental diseases, affecting 1060 and 1409 genes in PE vs controls and IUGR vs controls, respectively, many of those involved in placental function. While in IUGR placentas, alternative splicing affects genes specifically related to pregnancy, in preeclamptic placentas, it impacts a mix of genes related to pregnancy and brain diseases. Also, alternative splicing variations can be detected at the individual level as sharp splicing differences between different placentas. We correlate these variations with genetic variants to define splicing Quantitative Trait Loci (sQTL) in the subset of the 48 genes the most strongly alternatively spliced in placental diseases. We show that alternative splicing is at least partly piloted by genetic variants located either in cis (52 QTL identified) or in trans (52 QTL identified). In particular, we found four chromosomal regions that impact the splicing of genes in the placenta. The present work provides a new vision of placental gene expression regulation that warrants further studies.

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.

A Multi-Objective Approach for Drug Repurposing in Preeclampsia

Preeclampsia is a hypertensive disorder that occurs during pregnancy. It is a complex disease with unknown pathogenesis and the leading cause of fetal and maternal mortality during pregnancy. Using all drugs currently under clinical trial for preeclampsia, we extracted all their possible targets from the DrugBank and ChEMBL databases and labeled them as "targets". The proteins labeled as "off-targets" were extracted in the same way but while taking all antihypertensive drugs which are inhibitors of ACE and/or angiotensin receptor antagonist as query molecules. Classification models were obtained for each of the 55 total proteins (45 targets and 10 off-targets) using the TPOT pipeline optimization tool. The average accuracy of the models in predicting the external dataset for targets and off-targets was 0.830 and 0.850, respectively. The combinations of models maximizing their virtual screening performance were explored by combining the desirability function and genetic algorithms. The virtual screening performance metrics for the best model were: the Boltzmann-Enhanced Discrimination of ROC (BEDROC)α=160.9 = 0.258, the Enrichment Factor (EF)1% = 31.55 and the Area Under the Accumulation Curve (AUAC) = 0.831. The most relevant targets for preeclampsia were: AR, VDR, SLC6A2, NOS3 and CHRM4, while ABCG2, ERBB2, CES1 and REN led to the most relevant off-targets. A virtual screening of the DrugBank database identified estradiol, estriol, vitamins E and D, lynestrenol, mifrepristone, simvastatin, ambroxol, and some antibiotics and antiparasitics as drugs with potential application in the treatment of preeclampsia.

Collagen I Induces Preeclampsia-Like Symptoms by Suppressing Proliferation and Invasion of Trophoblasts

Preeclampsia is a common obstetric disorder affecting 2-8% of pregnancy worldwide. Fibrosis is an important histological change occurring in preeclamptic placenta, and might depend on the excess deposition of collagen I. However, the role of fibrotic placenta and collagen I in the pathogenesis of preeclampsia remains unclear. Therefore, we analyzed the collagen deposition and the expression of Collagen I in human placenta by Masson staining, Sirius red staining and western blotting. Further, the role of collagen I in preeclampsia pathogenesis was studied in C57BL/6 mice. HTR-8/SVneo cells were used to investigate the mechanisms underlying the effects of collagen I in trophoblasts by transcriptome sequencing and pharmacological agonists. Human preeclamptic placenta exhibited a significantly higher degree of fibrosis in stem villi and terminal villi than normal placenta, and was characterized by collagen I deposition. In vivo, a single injection of collagen I on gestational day 0.5 led to an increase in systolic pressure of pregnant mice from gestational days 4.5-17.5, to a decrease in weight and number of embryos, and to enhanced placental collagen I expression and degree of fibrosis compared with control mice. In vitro, collagen I attenuated the proliferation and invasion of HTR-8SV/neo cells. This effect could be reversed by treatment with agonists of ERK and β-catenin. Moreover, transcriptome sequencing demonstrated that signaling pathways related to cell proliferation and invasion were significantly downregulated in HTR-8SV/neo cells. Thus, we propose that collagen I induced preeclampsia-like symptoms by suppressing the proliferation and invasion of trophoblasts through inhibition of the ERK phosphorylation and WNT/β-catenin signaling pathways. Our findings could pave the way to the discovery of small-molecule inhibitors for preeclampsia treatment and future studies with larger sample size are required.

Transcription Factor PLAGL1 Is Associated with Angiogenic Gene Expression in the Placenta

During pregnancy, the placenta is important for transporting nutrients and waste between the maternal and fetal blood supply, secreting hormones, and serving as a protective barrier. To better understand placental development, we must understand how placental gene expression is regulated. We used RNA-seq data and ChIP-seq data for the enhancer associated mark, H3k27ac, to study gene regulation in the mouse placenta at embryonic day (e) 9.5, when the placenta is developing a complex network of blood vessels. We identified several upregulated transcription factors with enriched binding sites in e9.5-specific enhancers. The most enriched transcription factor, PLAGL1 had a predicted motif in 233 regions that were significantly associated with vasculature development and response to insulin stimulus genes. We then performed several experiments using mouse placenta and a human trophoblast cell line to understand the role of PLAGL1 in placental development. In the mouse placenta, Plagl1 is expressed in endothelial cells of the labyrinth layer and is differentially expressed in placentas from mice with gestational diabetes compared to placentas from control mice in a sex-specific manner. In human trophoblast cells, siRNA knockdown significantly decreased expression of genes associated with placental vasculature development terms. In a tube assay, decreased PLAGL1 expression led to reduced cord formation. These results suggest that Plagl1 regulates overlapping gene networks in placental trophoblast and endothelial cells, and may play a critical role in placental development in normal and complicated pregnancies.

Monochorionic twins with selective fetal growth restriction: insight from placental whole-transcriptome analysis

BACKGROUND

The underlying pathomechanism in placenta-related selective fetal growth restriction in monochorionic diamniotic twin pregnancy is not known.

OBJECTIVE

This study aimed to investigate any differences in placental transcriptomic profile between the selectively growth-restricted twins and the normally grown cotwins in monochorionic diamniotic twin pregnancies.

STUDY DESIGN

This was a prospective study of monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction. Placental biopsy specimens were obtained from the subjects in the delivery suite. The placental transcriptome of the selectively growth-restricted twin was compared with that of the normally grown cotwin. This study was divided into 2 stages: (1) gene discovery phase in which placental tissues from 5 monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction plus 2 control twin pregnancies underwent transcriptome profiling, and transcriptome profiling was carried out using whole-genome RNA sequencing; and (2) validation phase in which placental tissues from 13 monochorionic diamniotic twin pregnancies with selective fetal growth restriction underwent RNA and protein validation. RNA and protein expression levels of candidate genes were determined using quantitative real-time polymerase chain reaction and immunohistochemistry staining.

RESULTS

A total of 1429 transcripts were differentially expressed in the placentae of selectively growth-restricted twin pairs, where 610 were up-regulated and 819 were down-regulated. Endoplasmic reticulum lectin and mannose 6-phosphate receptor were consistently differentially up-regulated in all placentae of selectively growth-restricted twins. Quantitative real-time polymerase chain reaction and immunohistochemistry staining were used to validate the results (P<.05).

CONCLUSION

The expression of endoplasmic reticulum lectin and mannose 6-phosphate receptor, which are important for angiogenesis and fetal growth, was significantly increased in the placentae of selectively growth-restricted twin of a monochorionic twin pair.

Identifying new potential genetic biomarkers for HELLP syndrome using massive parallel sequencing

BACKGROUND

Preeclampsia (PE) is a frequently occurring multisystemic disease affecting ~5% of pregnancies. PE patients may develop HELLP syndrome (haemolysis, elevated liver enzymes, and low platelet), a mother and foetus life-threatening condition. Research into HELLP's genetic origin has been relatively unsuccessful, mainly because normal placental function and blood pressure regulation involve the fine-regulation of hundreds of genes.

OBJECTIVE

To identify new genes and mutations constituting potential biomarkers for HELLP syndrome.

STUDY DESIGN

The present case-control study involved whole-exome sequencing of 79 unrelated HELLP women. Candidate variants were screened in a control population constituted by 176 individuals. Stringent bioinformatics filters were used for selecting potentially etiological sequence variants in a subset of 487 genes. We used robust in silico mutation modelling for predicting the potential effect on protein structure.

RESULTS

We identified numerous sequence variants in genes related to angiogenesis/coagulation/blood pressure regulation, cell differentiation/communication/adhesion, cell cycle and transcriptional gene regulation, extracellular matrix biology, lipid metabolism and immunological response. Five sequence variants generated premature stop codons in genes playing an essential role in placental physiology (STOX1, PDGFD, IGF2, MMP1 and DNAH11). Six variants (ERAP1- p.Ile915Thr, ERAP2- p.Leu837Ser, COMT-p.His192Gln, CSAD-p.Pro418Ser, CDH1- p.Ala298Thr and CCR2-p.Met249Lys) led to destabilisation of protein structure as they had significant energy and residue interaction-related changes. We identified at least two mutations in 57% of patients, arguing in favour of a polygenic origin for the HELLP syndrome.

CONCLUSION

Our results provide novel evidence regarding PE/HELLP's genetic origin, leading to new biomarkers, having potential clinical usefulness, being proposed.

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.

Placental function in maternal obesity

Maternal obesity is associated with pregnancy complications and increases the risk for the infant to develop obesity, diabetes and cardiovascular disease later in life. However, the mechanisms linking the maternal obesogenic environment to adverse short- and long-term outcomes remain poorly understood. As compared with pregnant women with normal BMI, women entering pregnancy obese have more pronounced insulin resistance, higher circulating plasma insulin, leptin, IGF-1, lipids and possibly proinflammatory cytokines and lower plasma adiponectin. Importantly, the changes in maternal levels of nutrients, growth factors and hormones in maternal obesity modulate placental function. For example, high insulin, leptin, IGF-1 and low adiponectin in obese pregnant women activate mTOR signaling in the placenta, promoting protein synthesis, mitochondrial function and nutrient transport. These changes are believed to increase fetal nutrient supply and contribute to fetal overgrowth and/or adiposity in offspring, which increases the risk to develop disease later in life. However, the majority of obese women give birth to normal weight infants and these pregnancies are also associated with activation of inflammatory signaling pathways, oxidative stress, decreased oxidative phosphorylation and lipid accumulation in the placenta. Recent bioinformatics approaches have expanded our understanding of how maternal obesity affects the placenta; however, the link between changes in placental function and adverse outcomes in obese women giving birth to normal sized infants is unclear. Interventions that specifically target placental function, such as activation of placental adiponectin receptors, may prevent the transmission of metabolic disease from obese women to the next generation.

Transcription factor AP2A affects sFLT1 expression and decidualization in decidual stromal cells: Implications to preeclampsia pathology

Preeclampsia (PE) yields a spectrum of phenotypic expression, leading to varying degrees of hypertension, maternal renal dysfunction and placental insufficiency with resultant maternal and neonatal morbidity. Increased sFLT1 expression contributing to angiogenic factor imbalance, placental hypoxia, failed immune adaptation to the fetus and defective decidualization are among the commonly proposed theories of PE pathogenesis. Recently researchers have focused their attention on the events that occur at the maternal fetal interface as potential contributors to PE pathogenesis. Decidual stromal cells (DSC) isolated from preeclamptic women show diminished ability to decidualize upon stimulation and reduced capacity to downregulate sFlt-1 levels. In this study, we sought to gain insight into the molecular mechanism(s) involved in the aberrant decidualization capacity of PE DSC. Our findings using qRT-PCR show that PE DSCs have 6-fold higher basal levels of transcription factor AP2A (TFAP2A) RNA compared to women without PE and that expression of TFAP2A increases during decidualization but only in DSCs of normotensive (NT) women. Silencing of TFAP2A using Trilencer siRNA upregulated sFLT1 expression only in NT-DSCs but suppressed the expression of decidualization markers PRL, IGFBP1 and their regulator FOXO1 in cells from both groups. Collectively, our observations suggest that TFAP2A acts as a repressor of sFLT1 and plays a necessary role in decidualization possibly through interacting with another factor that is aberrantly expressed in PE DSCs.

Placental Microarray Profiling Reveals Common mRNA and lncRNA Expression Patterns in Preeclampsia and Intrauterine Growth Restriction

Preeclampsia (PE) and Intrauterine Growth Restriction (IUGR) are major contributors to perinatal morbidity and mortality. These pregnancy disorders are associated with placental dysfunction and share similar pathophysiological features. The aim of this study was to compare the placental gene expression profiles including mRNA and lncRNAs from pregnant women from four study groups: PE, IUGR, PE-IUGR, and normal pregnancy (NP). Gene expression microarray analysis was performed on placental tissue obtained at delivery and results were validated using RTq-PCR. Differential gene expression analysis revealed that the largest transcript variation was observed in the IUGR samples compared to NP (n = 461; 314 mRNAs: 252 up-regulated and 62 down-regulated; 133 lncRNAs: 36 up-regulated and 98 down-regulated). We also detected a group of differentially expressed transcripts shared between the PE and IUGR samples compared to NP (n = 39), including 9 lncRNAs with a high correlation degree (p < 0.05). Functional enrichment of these shared transcripts showed that cytokine signaling pathways, protein modification, and regulation of JAK-STAT cascade are over-represented in both placental ischemic diseases. These findings contribute to the molecular characterization of placental ischemia showing common epigenetic regulation implicated in the pathophysiology of PE and IUGR.

Reduced mRNA Expression of RGS2 (Regulator of G Protein Signaling-2) in the Placenta Is Associated With Human Preeclampsia and Sufficient to Cause Features of the Disorder in Mice

Cascade-specific termination of G protein signaling is catalyzed by the RGS (regulator of G protein signaling) family members, including RGS2. Angiotensin, vasopressin, and endothelin are implicated in preeclampsia, and RGS2 is known to inhibit G protein cascades activated by these hormones. Mutations in RGS2 are associated with human hypertension and increased risk of developing preeclampsia and its sequelae. RGS family members are known to influence maternal vascular function, but the role of RGS2 within the placenta has not been explored. Here, we hypothesized that reduced expression of RGS2 within the placenta represents a risk factor for the development of preeclampsia. Although cAMP/CREB signaling was enriched in placentas from human pregnancies affected by preeclampsia compared with clinically matched controls and RGS2 is known to be a CREB-responsive gene, RGS2 mRNA was reduced in placentas from pregnancies affected by preeclampsia. Experimentally reducing Rgs2 expression within the feto-placental unit was sufficient to induce preeclampsia-like phenotypes in pregnant wild-type C57BL/6J mice. Stimulation of RGS2 transcription within immortalized human HTR8/SVneo trophoblasts by cAMP/CREB signaling was discovered to be dependent on the activity of histone deacetylase activity, and more specifically, HDAC9 (histone deacetylase-9), and HDAC9 expression was reduced in placentas from human pregnancies affected by preeclampsia. We conclude that reduced expression of RGS2 within the placenta may mechanistically contribute to preeclampsia. More generally, this work identifies RGS2 as an HDAC9-dependent CREB-responsive gene, which may contribute to reduced RGS2 expression in placenta during preeclampsia.

Genomic Profiling of BDE-47 Effects on Human Placental Cytotrophoblasts

Despite gradual legislative efforts to phase out flame retardants (FRs) from the marketplace, polybrominated diphenyl ethers (PBDEs) are still widely detected in human maternal and fetal tissues, eg, placenta, due to their continued global application in consumer goods and inherent biological persistence. Recent studies in rodents and human placental cell lines suggest that PBDEs directly cause placental toxicity. During pregnancy, trophoblasts play key roles in uterine invasion, vascular remodeling, and anchoring of the placenta-fetal unit to the mother. Thus, to study the potential consequences of PBDE exposures on human placental development, we used an in vitro model: primary villous cytotrophoblasts (CTBs). Following exposures, the endpoints that were evaluated included cytotoxicity, function (migration, invasion), the transcriptome, and the methylome. In a concentration-dependent manner, common PBDE congeners, BDE-47 and -99, significantly reduced cell viability and increased death. Upon exposures to sub-cytotoxic concentrations (≤ 5 µM), we observed BDE-47 accumulation in CTBs with limited evidence of metabolism. At a functional level, BDE-47 hindered the ability of CTBs to migrate and invade. Transcriptomic analyses of BDE-47 effects suggested concentration-dependent changes in gene expression, involving stress pathways, eg, inflammation and lipid/cholesterol metabolism as well as processes underlying trophoblast fate, eg, differentiation, migration, and vascular morphogenesis. In parallel assessments, BDE-47 induced low-level global increases in methylation of CpG islands, including a subset that were proximal to genes with roles in cell adhesion/migration. Thus, using a primary human CTB model, we showed that PBDEs induced alterations at cellular and molecular levels, which could adversely impact placental development.

The Role of Epigenetics in Placental Development and the Etiology of Preeclampsia

In this review, we comprehensively present the function of epigenetic regulations in normal placental development as well as in a prominent disease of placental origin, preeclampsia (PE). We describe current progress concerning the impact of DNA methylation, non-coding RNA (with a special emphasis on long non-coding RNA (lncRNA) and microRNA (miRNA)) and more marginally histone post-translational modifications, in the processes leading to normal and abnormal placental function. We also explore the potential use of epigenetic marks circulating in the maternal blood flow as putative biomarkers able to prognosticate the onset of PE, as well as classifying it according to its severity. The correlation between epigenetic marks and impacts on gene expression is systematically evaluated for the different epigenetic marks analyzed.

An intron variant in the FLT1 gene increases the risk of preeclampsia in Iranian women

Background: Preeclampsia is a hypertensive disorder that affects pregnancy, mother, and fetus. Pathogenesis of preeclampsia could be associated with the angiogenesis pathways. The vascular endothelial growth factor (VEGF) family is one of the important factors for normal pregnancy and angiogenesis. Genetic variations in the gene family members may play a role in the etiology of preeclampsia. We investigated the possible association between VEGFA gene rs3025039, and VEGFR1 (FLT1) gene rs722503 polymorphisms and preeclampsia in a sample of Iranian patients. Methods: Genotyping was performed in 395 women, including, 204 pre-eclamptic pregnant women and 191 healthy normotensive pregnant women by using the PCR-RFLP method. Results: The rs722503 polymorphism was associated with preeclampsia under the dominant model (P = 0.04, OR = 1.53, 95% CI: 1.03-2.27). No significant difference was observed for the rs3025039 alleles and genotypes in the studied groups. Conclusions: Based on our study, rs722503 polymorphism in the FLT1 gene may play an important role in susceptibility to preeclampsia.

Maternal Choline Supplementation during Normal Murine Pregnancy Alters the Placental Epigenome: Results of an Exploratory Study

The placental epigenome regulates processes that affect placental and fetal development, and could be mediating some of the reported effects of maternal choline supplementation (MCS) on placental vascular development and nutrient delivery. As an extension of work previously conducted in pregnant mice, the current study sought to explore the effects of MCS on various epigenetic markers in the placenta. RNA and DNA were extracted from placentas collected on embryonic day 15.5 from pregnant mice fed a 1X or 4X choline diet, and were subjected to genome-wide sequencing procedures or mass-spectrometry-based assays to examine placental imprinted gene expression, DNA methylation patterns, and microRNA (miRNA) abundance. MCS yielded a higher (fold change = 1.63-2.25) expression of four imprinted genes (Ampd3, Tfpi2, Gatm and Aqp1) in the female placentas and a lower (fold change = 0.46-0.62) expression of three imprinted genes (Dcn, Qpct and Tnfrsf23) in the male placentas (false discovery rate (FDR) ≤ 0.05 for both sexes). Methylation in the promoter regions of these genes and global placental DNA methylation were also affected (p ≤ 0.05). Additionally, a lower (fold change = 0.3; P_unadjusted = 2.05 × 10^-4; FDR = 0.13) abundance of miR-2137 and a higher (fold change = 1.25-3.92; p < 0.05) expression of its target genes were detected in the 4X choline placentas. These data demonstrate that the placental epigenome is responsive to maternal choline intake during murine pregnancy and likely mediates some of the previously described choline-induced effects on placental and fetal outcomes.

Evaluation of DNA Damage in Experimental Preeclampsia by Comet Assay

Experimental preeclampsia induced by substitution of drinking water with 1.8% NaCl during pregnancy was associated with an increase in the level of DNA damage in fetal brain and placenta measured by DNA comet assay by 35.7 and 27.8 times, respectively, in comparison with physiological pregnancy.

Downregulation of decidual SP1 and P300 is associated with severe preeclampsia

Preeclampsia (PE) is a pregnancy-induced disorder characterized by hypertension and proteinuria after 20 weeks of gestation, affecting 5-7% of pregnancies worldwide. So far, the etiology of PE remains poorly understood. Abnormal decidualization is thought to contribute to the development of PE. SP1 belongs to the Sp/KLF superfamily and can recruit P300 to regulate the transcription of several genes. SP1 is also very important for decidualization as it enhances the expression of tissue factor. In this study, we investigated the expression of SP1 and P300 in deciduae and their relationship with PE. A total of 42 decidua samples were collected, of which 21 were from normal pregnant (NP) and 21 from severe PE. SP1 and P300 expression in deciduae and the levels of SP1 and P300 in cultured human endometrial stromal cells (hESCs) and primary hESCs during decidualization were determined. To further investigate the role of SP1 and P300 in human decidualization, RNA interference was used to silence SP1 and P300 in hESCs and primary hESCs. The following results were obtained. We found that the expressions of SP1 and P300 were reduced in decidual tissues with PE compared to those from NP. In the in vitro model of induction of decidualization, we found an increase in both SP1 and P300 levels. Silencing of SP1 and P300 resulted in abnormal decidualization and a significant reduction of decidualization markers such as insulin-like growth factor-binding protein1 and prolactin. Furthermore, the expression of vascular endothelial growth factor was also decreased upon SP1 and P300 silencing. Similar results were observed in primary hESCs. Our results suggest that SP1 and P300 play an important role during decidualization. Dysfunction of SP1 and P300 leads to impaired decidualization and might contribute to PE.

Transcriptomic difference in bovine blastocysts following vitrification and slow freezing at morula stage

Cryopreservation is known for its marked deleterious effects on embryonic health. Bovine compact morulae were vitrified or slow-frozen, and post-warm morulae were cultured to the expanded blastocyst stage. Blastocysts developed from vitrified and slow-frozen morulae were subjected to microarray analysis and compared with blastocysts developed from unfrozen control morulae for differential gene expression. Morula to blastocyst conversion rate was higher (P < 0.05) in control (72%) and vitrified (77%) than in slow-frozen (34%) morulae. Total 20 genes were upregulated and 44 genes were downregulated in blastocysts developed from vitrified morulae (fold change ≥ ± 2, P < 0.05) in comparison with blastocysts developed from control morulae. In blastocysts developed from slow-frozen morulae, 102 genes were upregulated and 63 genes were downregulated (fold change ≥ ± 1.5, P < 0.05). Blastocysts developed from vitrified morulae exhibited significant changes in gene expression mainly involving embryo implantation (PTGS2, CALB1), lipid peroxidation and reactive oxygen species generation (HSD3B1, AKR1B1, APOA1) and cell differentiation (KRT19, CLDN23). However, blastocysts developed from slow-frozen morulae showed changes in the expression of genes related to cell signaling (SPP1), cell structure and differentiation (DCLK2, JAM2 and VIM), and lipid metabolism (PLA2R1 and SMPD3). In silico comparison between blastocysts developed form vitrified and slow-frozen morulae revealed similar changes in gene expression as between blastocysts developed from vitrified and control morulae. In conclusion, blastocysts developed form vitrified morulae demonstrated better post-warming survival than blastocysts developed from slow-frozen morulae but their gene expression related to lipid metabolism, steroidogenesis, cell differentiation and placentation changed significantly (≥ 2 fold). Slow freezing method killed more morulae than vitrification but those which survived up to blastocyst stage did not express ≥ 2 fold change in their gene expression as compared with blastocysts from control morulae.

Hypoxia-Induced Activation of JAK/STAT3 Signaling Pathway Promotes Trophoblast Cell Viability and Angiogenesis in Preeclampsia

Background

To explore the effect of hypoxic preconditioning on the JAK/STAT3 signaling pathway and its effect on trophoblast cell viability and angiogenesis in preeclampsia (PE).

Material/Methods

Placental tissues from normal pregnant women and PE patients were collected to detect the expression levels of JAK and STAT3. Trophoblast cells separated from the PE patients were assigned to 4 groups. The expression levels of phosphorylated p-JAK and p-STAT3 were measured by Western blot. Cell viability, colony-forming ability, and cell apoptosis were assessed. The levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hepatocyte growth factor (HGF) were determined by enzyme-linked immunosorbent assay (ELISA).

Results

The expression levels of JAK and STAT3 were higher in the placental tissues of PE patients than in those of normal pregnant women. Compared with the blank group, in the hypoxia group the expression levels of p-JAK and p-STAT3 were increased, cell viability was promoted, the number of colonies was increased, cell apoptosis was inhibited, and the levels of VEGF, bFGF, and HGF were all elevated. However, in comparison with the hypoxia group, the expression levels of p-JAK and p-STAT3 were reduced, the cell viability was inhibited, the colonies were decreased, the levels of VEGF, bFGF, and HGF were all decreased, and cell apoptosis was promoted in the hypoxia + si-JAK group.

Conclusions

These findings indicate that hypoxic preconditioning may contribute to activation of the JAK/STAT3 signaling pathway, thus promoting trophoblast cell viability and angiogenesis in PE.

Disturbed Placental Imprinting in Preeclampsia Leads to Altered Expression of DLX5, a Human-Specific Early Trophoblast Marker

Supplemental Digital Content is available in the text.

Background:

Preeclampsia is a complex and common human-specific pregnancy syndrome associated with placental pathology. The human specificity provides both intellectual and methodological challenges, lacking a robust model system. Given the role of imprinted genes in human placentation and the vulnerability of imprinted genes to loss of imprinting changes, there has been extensive speculation, but no robust evidence, that imprinted genes are involved in preeclampsia. Our study aims to investigate whether disturbed imprinting contributes to preeclampsia.

Methods:

We first aimed to confirm that preeclampsia is a disease of the placenta by generating and analyzing genome-wide molecular data on well-characterized patient material. We performed high-throughput transcriptome analyses of multiple placenta samples from healthy controls and patients with preeclampsia. Next, we identified differentially expressed genes in preeclamptic placentas and intersected them with the list of human imprinted genes. We used bioinformatics/statistical analyses to confirm association between imprinting and preeclampsia and to predict biological processes affected in preeclampsia. Validation included epigenetic and cellular assays. In terms of human specificity, we established an in vitro invasion-differentiation trophoblast model. Our comparative phylogenetic analysis involved single-cell transcriptome data of human, macaque, and mouse preimplantation embryogenesis.

Results:

We found disturbed placental imprinting in preeclampsia and revealed potential candidates, including GATA3 and DLX5, with poorly explored imprinted status and no prior association with preeclampsia. As a result of loss of imprinting, DLX5 was upregulated in 69% of preeclamptic placentas. Levels of DLX5 correlated with classic preeclampsia markers. DLX5 is expressed in human but not in murine trophoblast. The DLX5^high phenotype resulted in reduced proliferation, increased metabolism, and endoplasmic reticulum stress-response activation in trophoblasts in vitro. The transcriptional profile of such cells mimics the transcriptome of preeclamptic placentas. Pan-mammalian comparative analysis identified DLX5 as part of the human-specific regulatory network of trophoblast differentiation.

Conclusions:

Our analysis provides evidence of a true association among disturbed imprinting, gene expression, and preeclampsia. As a result of disturbed imprinting, the upregulated DLX5 affects trophoblast proliferation. Our in vitro model might fill a vital niche in preeclampsia research. Human-specific regulatory circuitry of DLX5 might help explain certain aspects of preeclampsia.

Consensus strategy in genes prioritization and combined bioinformatics analysis for preeclampsia pathogenesis

BACKGROUND

Preeclampsia is a multifactorial disease with unknown pathogenesis. Even when recent studies explored this disease using several bioinformatics tools, the main objective was not directed to pathogenesis. Additionally, consensus prioritization was proved to be highly efficient in the recognition of genes-disease association. However, not information is available about the consensus ability to early recognize genes directly involved in pathogenesis. Therefore our aim in this study is to apply several theoretical approaches to explore preeclampsia; specifically those genes directly involved in the pathogenesis.

METHODS

We firstly evaluated the consensus between 12 prioritization strategies to early recognize pathogenic genes related to preeclampsia. A communality analysis in the protein-protein interaction network of previously selected genes was done including further enrichment analysis. The enrichment analysis includes metabolic pathways as well as gene ontology. Microarray data was also collected and used in order to confirm our results or as a strategy to weight the previously enriched pathways.

RESULTS

The consensus prioritized gene list was rationally filtered to 476 genes using several criteria. The communality analysis showed an enrichment of communities connected with VEGF-signaling pathway. This pathway is also enriched considering the microarray data. Our result point to VEGF, FLT1 and KDR as relevant pathogenic genes, as well as those connected with NO metabolism.

CONCLUSION

Our results revealed that consensus strategy improve the detection and initial enrichment of pathogenic genes, at least in preeclampsia condition. Moreover the combination of the first percent of the prioritized genes with protein-protein interaction network followed by communality analysis reduces the gene space. This approach actually identifies well known genes related with pathogenesis. However, genes like HSP90, PAK2, CD247 and others included in the first 1% of the prioritized list need to be further explored in preeclampsia pathogenesis through experimental approaches.

Emerging role for dysregulated decidualization in the genesis of preeclampsia

In normal human placentation, uterine invasion by trophoblast cells and subsequent spiral artery remodeling depend on cooperation among fetal trophoblasts and maternal decidual, myometrial, immune and vascular cells in the uterine wall. Therefore, aberrant function of anyone or several of these cell-types could theoretically impair placentation leading to the development of preeclampsia. Because trophoblast invasion and spiral artery remodeling occur during the first half of pregnancy, the molecular pathology of fetal placental and maternal decidual tissues following delivery may not be informative about the genesis of impaired placentation, which transpired months earlier. Therefore, in this review, we focus on the emerging prospective evidence supporting the concept that deficient or defective endometrial maturation in the late secretory phase and during early pregnancy, i.e., pre-decidualization and decidualization, respectively, may contribute to the genesis of preeclampsia. The first prospectively-acquired data directly supporting this concept were unexpectedly revealed in transcriptomic analyses of chorionic villous samples (CVS) obtained during the first trimester of women who developed preeclampsia 5 months later. Additional supportive evidence arose from investigations of Natural Killer cells in first trimester decidua from elective terminations of women with high resistance uterine artery indices, a surrogate for deficient trophoblast invasion. Last, circulating insulin growth factor binding protein-1, which is secreted by decidual stromal cells was decreased during early pregnancy in women who developed preeclampsia. We conclude this review by making recommendations for further prospectively-designed studies to corroborate the concept of endometrial antecedents of preeclampsia. These studies could also enable identification of women at increased risk for developing preeclampsia, unveil the molecular mechanisms of deficient or defective (pre)decidualization, and lead to preventative strategies designed to improve (pre)decidualization, thereby reducing risk for preeclampsia development.

Copy number variation profile in the placental and parental genomes of recurrent pregnancy loss families

We have previously shown an extensive load of somatic copy number variations (CNVs) in the human placental genome with the highest fraction detected in normal term pregnancies. Hereby, we hypothesized that insufficient promotion of CNVs may impair placental development and lead to recurrent pregnancy loss (RPL). RPL affects ~3% of couples aiming at childbirth and idiopathic RPL represents ~50% of cases. We analysed placental and parental CNV profiles of idiopathic RPL trios (mother-father-placenta) and duos (mother-placenta). Consistent with the hypothesis, the placental genomes of RPL cases exhibited 2-fold less CNVs compared to uncomplicated 1^st trimester pregnancies (P = 0.02). This difference mainly arose from lower number of duplications. Overall, 1^st trimester control placentas shared only 5.3% of identified CNV regions with RPL cases, whereas the respective fraction with term placentas was 35.1% (P = 1.1 × 10⁻⁹). Disruption of the genes NUP98 (embryonic stem cell development) and MTRR (folate metabolism) was detected exclusively in RPL placentas, potentially indicative to novel loci implicated in RPL. Interestingly, genes with higher overall expression were prone to deletions (>3-fold higher median expression compared to genes unaffected by CNVs, P = 6.69 × 10⁻²⁰). Additionally, large pericentromeric and subtelomeric CNVs in parental genomes emerged as a risk factor for RPL.

Placental transcriptome co-expression analysis reveals conserved regulatory programs across gestation

BACKGROUND

Mammalian development in utero is absolutely dependent on proper placental development, which is ultimately regulated by the placental genome. The regulation of the placental genome can be directly studied by exploring the underlying organisation of the placental transcriptome through a systematic analysis of gene-wise co-expression relationships.

RESULTS

In this study, we performed a comprehensive analysis of human placental co-expression using RNA sequencing and intergrated multiple transcriptome datasets spanning human gestation. We identified modules of co-expressed genes that are preserved across human gestation, and also identifed modules conserved in the mouse indicating conserved molecular networks involved in placental development and gene expression patterns more specific to late gestation. Analysis of co-expressed gene flanking sequences indicated that conserved co-expression modules in the placenta are regulated by a core set of transcription factors, including ZNF423 and EBF1. Additionally, we identified a gene co-expression module enriched for genes implicated in the pregnancy pathology preeclampsia. By using an independnet transcriptome dataset, we show that these co-expressed genes are differentially expressed in preeclampsia.

CONCLUSIONS

This study represents a comprehensive characterisation of placental co-expression and provides insight into potential transcriptional regulators that govern conserved molecular programs fundamental to placental development.

Oxidative stress and inflammation in retained placenta: a pilot study of protein and gene expression of GPX1 and NFκB

BACKGROUND

Retained placenta is associated with severe postpartum hemorrhage. Its etiology is unknown and its biochemistry has not been studied. We aimed to assess whether levels of the antioxidative enzyme Glutathione Peroxidase 1 (GPX1) and the transcription factor Nuclear Factor κβ (NFκβ), as markers of oxidative stress and inflammation, were affected in retained placentas compared to spontaneously released placentas from otherwise normal full term pregnancies.

METHODS

In a pilot study we assessed concentrations of GPX1 by ELISA and gene (mRNA) expression of GPX1, NFκβ and its inhibitor Iκβα, by quantitative real-time-PCR in periumbilical and peripheral samples from retained (n = 29) and non-retained (n = 31) placental tissue.

RESULTS

Median periumbilical GPX1 concentrations were 13.32 ng/ml in retained placentas and 17.96 ng/ml in non-retained placentas (p = 0.22), peripheral concentrations were 13.27 ng/ml and 19.09 ng/ml (p = 0.08). Retained placental tissue was more likely to have a low GPX1 protein concentration (OR 3.82, p = 0.02 for periumbilical and OR 3.95, p = 0.02 for peripheral samples). Median periumbilical GPX1 gene expressions were 1.13 for retained placentas and 0.88 for non-retained placentas (p = 0.08), peripheral expression was 1.32 and 1.18 (p = 0.46). Gene expressions of NFκβ and Iκβα were not significantly different between retained and non-retained placental tissue.

CONCLUSIONS

Women with retained placenta were more likely to have a low level of GPX1 protein concentration in placental tissue compared to women without retained placenta and retained placental tissue showed a tendency of lower median concentrations of GPX1 protein expression. This may indicate decreased antioxidative capacity as a component in this disorder but requires a larger sample to corroborate results.

An Integrative Analysis of Preeclampsia Based on the Construction of an Extended Composite Network Featuring Protein-Protein Physical Interactions and Transcriptional Relationships

Preeclampsia (PE) is a pregnancy disorder defined by hypertension and proteinuria. This disease remains a major cause of maternal and fetal morbidity and mortality. Defective placentation is generally described as being at the root of the disease. The characterization of the transcriptome signature of the preeclamptic placenta has allowed to identify differentially expressed genes (DEGs). However, we still lack a detailed knowledge on how these DEGs impact the function of the placenta. The tools of network biology offer a methodology to explore complex diseases at a systems level. In this study we performed a cross-platform meta-analysis of seven publically available gene expression datasets comparing non-pathological and preeclamptic placentas. Using the rank product algorithm we identified a total of 369 DEGs consistently modified in PE. The DEGs were used as seeds to build both an extended physical protein-protein interactions network and a transcription factors regulatory network. Topological and clustering analysis was conducted to analyze the connectivity properties of the networks. Finally both networks were merged into a composite network which presents an integrated view of the regulatory pathways involved in preeclampsia and the crosstalk between them. This network is a useful tool to explore the relationship between the DEGs and enable hypothesis generation for functional experimentation.

Comparison of Normal and Pre-Eclamptic Placental Gene Expression: A Systematic Review with Meta-Analysis

Pre-eclampsia (PE) is a serious multi-factorial disorder of human pregnancy. It is associated with changes in the expression of placental genes. Recent transcription profiling of placental genes with microarray analyses have offered better opportunities to define the molecular pathology of this disorder. However, the extent to which placental gene expression changes in PE is not fully understood. We conducted a systematic review of published PE and normal pregnancy (NP) control placental RNA microarrays to describe the similarities and differences between NP and PE placental gene expression, and examined how these differences could contribute to the molecular pathology of the disease. A total of 167 microarray samples were available for meta-analysis. We found the expression pattern of one group of genes was the same in PE and NP. The review also identified a set of genes (PE unique genes) including a subset, that were significantly (p < 0.05) down-regulated in pre-eclamptic placentae only. Using class prediction analysis, we further identified the expression of 88 genes that were highly associated with PE (p < 0.05), 10 of which (LEP, HTRA4, SPAG4, LHB, TREM1, FSTL3, CGB, INHA, PROCR, and LTF) were significant at p < 0.001. Our review also suggested that about 30% of genes currently being investigated as possibly of importance in PE placenta were not consistently and significantly affected in the PE placentae. We recommend further work to confirm the roles of the PE unique and associated genes, currently not being investigated in the molecular pathology of the disease.

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.

Unsupervised Placental Gene Expression Profiling Identifies Clinically Relevant Subclasses of Human Preeclampsia

Preeclampsia (PE) is a complex, hypertensive disorder of pregnancy, demonstrating considerable variability in maternal symptoms and fetal outcomes. Unfortunately, prior research has not accounted for this variability, resulting in a lack of robust biomarkers and effective treatments for PE. Here, we created a large (N=330) clinically relevant human placental microarray data set, consisting of 7 previously published studies and 157 highly annotated new samples from a single BioBank. Applying unsupervised clustering to this combined data set identified 3 clinically significant probable etiologies of PE: "maternal", with healthy placentas and term deliveries; "canonical", exhibiting expected clinical, ontological, and histopathologic features of PE; and "immunologic" with severe fetal growth restriction and evidence of maternal antifetal rejection. Moreover, these groups could be distinguished using a small quantitative polymerase chain reaction panel and demonstrated varying influence of maternal factors on PE development. An additional subclass of PE placentas was also revealed to form because of chromosomal abnormalities in these samples, supported by array-based comparative genomic hybridization analysis. Overall, our findings represent a new paradigm in our understanding of the origins and maternal-placental contributions to the pathology of PE. The study of PE represents a unique opportunity to access human tissue associated with a complex hypertensive disorder, and our novel approach could be applied to other hypertensive and heterogeneous human diseases.

NF-κΒ and SOD expression in preeclamptic placentas

BACKGROUND/AIM

Preeclampsia is a leading cause of maternal death in the developing world. Our aim was to quantify and compare messenger (mRNA) expression of nuclear factor-kappa beta (NF-κΒ) and superoxide dismutase (SOD) in control patients with preeclampsia and without preeclampsia with or without familial hereditary background.

MATERIALS AND METHODS

Four groups of patients were formed depending on the presence or absence of preeclampsia and presence or absence of familial history for preeclampsia. NF-κΒ and SOD were measured in human placentas by real-time quantitative polymerase chain reaction. The 2-ΔΔct analysis method was used to measure the difference in the relative expression of the target genes in each group of patients.

RESULTS

In NF-κΒ expression, there was an increase of 23.35% in the group of women with preeclampsia versus women with preeclampsia without familial history. Regarding SOD, there was a reduction of about 33.33% in the expression in women with preeclampsia with familial history versus women with preeclampsia without familial history.

CONCLUSION

Familial presence of preeclampsia could predispose to altered expression in SOD and NF-κΒ.

Expression of epigenetic machinery genes is sensitive to maternal obesity and weight loss in relation to fetal growth in mice

BACKGROUND

Maternal obesity impacts fetal growth and pregnancy outcomes. To counteract the deleterious effects of obesity on fertility and pregnancy issue, preconceptional weight loss is recommended to obese women. Whether this weight loss is beneficial/detrimental for offspring remains poorly explored. Epigenetic mechanisms could be affected by maternal weight changes, perturbing expression of key developmental genes in the placenta or fetus. Our aim was to investigate the effects of chronic maternal obesity on feto-placental growth along with the underlying epigenetic mechanisms. We also tested whether preconceptional weight loss could alleviate these effects.

RESULTS

Female mice were fed either a control diet (CTRL group), a high-fat diet (obese (OB) group), or a high-fat diet switched to a control diet 2 months before conception (weight loss (WL) group). At mating, OB females presented an obese phenotype while WL females normalized metabolic parameters. At embryonic day 18.5 (E18.5), fetuses from OB females presented fetal growth restriction (FGR; -13 %) and 28 % of the fetuses were small for gestational age (SGA). Fetuses from WL females normalized this phenotype. The expression of 60 epigenetic machinery genes and 32 metabolic genes was measured in the fetal liver, placental labyrinth, and junctional zone. We revealed 23 genes altered by maternal weight trajectories in at least one of three tissues. The fetal liver and placental labyrinth were more responsive to maternal obesity than junctional zone. One third (18/60) of the epigenetic machinery genes were differentially expressed between at least two maternal groups. Interestingly, genes involved in the histone acetylation pathway were particularly altered (13/18). In OB group, lysine acetyltransferases and Bromodomain-containing protein 2 were upregulated, while most histone deacetylases were downregulated. In WL group, the expression of only a subset of these genes was normalized.

CONCLUSIONS

This study highlights the high sensitivity of the epigenetic machinery gene expression, and particularly the histone acetylation pathway, to maternal obesity. These obesity-induced transcriptional changes could alter the placental and the hepatic epigenome, leading to FGR. Preconceptional weight loss appears beneficial to fetal growth, but some effects of previous obesity were retained in offspring phenotype.

Hypoxia-inducible miR-210 contributes to preeclampsia via targeting thrombospondin type I domain containing 7A

Preeclampsia, a relatively common pregnancy disorder, is a major contributor to maternal mortality and morbidity worldwide. An elevation in microRNA-210 (miR-210) expression in the placenta has been reported to be associated with preeclampsia. Our bioinformatic analysis showed that thrombospondin type I domain containing 7A (THSD7A) is a predicted target for miR-210. The aim of this study was to determine whether miR-210 is involved in preeclampsia through its targeting of THSD7A in human placental trophoblasts. In preeclamptic placental tissues, THSD7A levels were significantly downregulated, and were inversely correlated with the levels of miR-210. THSD7A was validated as a direct target of miR-210 using quantitative real time PCR (qRT-PCR), Western blotting, and dual luciferase assays in HTR8/SVneo cells. Transwell insert invasion assays showed that THSD7A mediated the invasion-inhibitory effect of miR-210 in HTR8/SVneo cells. Interestingly, hypoxia markedly increased miR-210 expression while suppressing THSD7A expression in a time-dependent manner in HTR8/SVneo cells. This study provides novel data on the function of THSD7A in human placental cells, and extends our knowledge of how miR-210 is involved in the development of the preeclampsia.

Epigenetics and Preeclampsia: Defining Functional Epimutations in the Preeclamptic Placenta Related to the TGF-β Pathway

Preeclampsia is a potentially fatal pregnancy disorder affecting millions of women around the globe. Dysregulation in gene and protein expression within key biological pathways controlling angiogenesis has been implicated in the development of preeclampsia. Altered CpG methylation, a type of epimutation, may underlie this pathway dysregulation. In the present study, placental tissue from preeclamptic cases and normotensive controls was analyzed for genome-wide differential CpG methylation and concomitant changes in gene expression. A set of 123 genes, representing 19.9% of all genes with altered CpG methylation, was associated with functional changes in transcript levels. Underscoring the complex relationships between CpG methylation and gene expression, here hypermethylation was never associated with gene silencing, nor was hypomethylation always associated with gene activation. Moreover, the genomic region of the CpG mark was important in predicting the relationship between CpG methylation and gene expression. The 123 genes were enriched for their involvement in the transforming growth factor beta (TGF-β) signaling pathway, a known regulator of placental trophoblast invasion and migration. This is the first study to identify CpG hypomethylation as an activator of TGF-β-associated gene expression in the preeclamptic placenta. The results suggest functional epimutations are associated with preeclampsia disease status and the identified genes may represent novel biomarkers of disease.