Microarray-based identification of differentially expressed genes in hypoxic term human trophoblasts and in placental villi of pregnancies with growth restricted fetuses

Transcriptomic profiling in hypoxia-induced trophoblast cells for preeclampsia

This study aimed to identify the expression profile of mRNAs and analyze the associated pathways in hypoxia-induced trophoblast cells to understand the effect of hypoxia on the pathophysiology of preeclampsia (PE). We downloaded two gene expression datasets (GSE47187 and GSE60432) from the Gene Expression Omnibus (GEO) datasets to identify altered transcriptomes. GEO2R, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction (PPI) networks were used to reveal the functional roles and regulatory networks of the differentially expressed genes (DEGs). In total, 224 DEGs (91 upregulated and 133 downregulated) were identified, and the "HIF-1 signaling pathway" was activated in placentas from patients with PE. We validated the expression levels of five proteins in the plasma of NP and PE patients during early or late pregnancy using western blotting. In primary trophoblast cells cultured under hypoxic conditions, 754 DEGs were identified, including 362 upregulated and 392 downregulated genes. These DEGs were associated with the "HIF-1signaling pathway," "response to hypoxia," and several glucose metabolism pathways. In addition, a PPI network was constructed, and an important module, including 18 hub genes, was identified. Finally, we validated 18 hub genes using qRT-PCR. Furthermore, we performed microarray profiling of hypoxia-treated HTR8/SVneo cells (immortalized human first-trimester extravillous trophoblast cells) to validate the DEGs and pathways identified in hypoxia-induced primary trophoblast cells. Our results stress the differential expression profiles of mRNAs in hypoxia-induced trophoblast cells, which provide potential pathophysiological mechanisms for preeclampsia.

N-myc downstream regulated gene 1 (ndrg1) functions as a molecular switch for cellular adaptation to hypoxia

Lack of oxygen (hypoxia and anoxia) is detrimental to cell function and survival and underlies many disease conditions. Hence, metazoans have evolved mechanisms to adapt to low oxygen. One such mechanism, metabolic suppression, decreases the cellular demand for oxygen by downregulating ATP-demanding processes. However, the molecular mechanisms underlying this adaptation are poorly understood. Here, we report on the role of ndrg1a in hypoxia adaptation of the anoxia-tolerant zebrafish embryo. ndrg1a is expressed in the kidney and ionocytes, cell types that use large amounts of ATP to maintain ion homeostasis. ndrg1a mutants are viable and develop normally when raised under normal oxygen. However, their survival and kidney function is reduced relative to WT embryos following exposure to prolonged anoxia. We further demonstrate that Ndrg1a binds to the energy-demanding sodium-potassium ATPase (NKA) pump under anoxia and is required for its degradation, which may preserve ATP in the kidney and ionocytes and contribute to energy homeostasis. Lastly, we show that sodium azide treatment, which increases lactate levels under normoxia, is sufficient to trigger NKA degradation in an Ndrg1a-dependent manner. These findings support a model whereby Ndrg1a is essential for hypoxia adaptation and functions downstream of lactate signaling to induce NKA degradation, a process known to conserve cellular energy.

Prenatal health behaviours as predictors of human placental lactogen levels

Placental lactogen (hPL) is a key hormone of pregnancy responsible for inducing maternal adaptations critical for a successful pregnancy. Low levels of placental lactogen have been associated with lower birth weight as well as symptoms of maternal depression and anxiety. Lower placental lactogen has been reported in women with higher body mass index (BMI) but it is unclear whether prenatal health behaviours predict hPL levels or if hPL is associated with infant weight outcomes. This study utilised data from the longitudinal Grown in Wales cohort, based in South Wales. Participants were recruited at the pre-surgical appointment for an elective caesarean section. This study incorporates data from recruitment, post-delivery and a 12 month follow-up. Measures of maternal serum hPL were available for 248 participants. Analysis included unadjusted and adjusted linear and binary regression. Unadjusted, prenatal smoking and a Health Conscious dietary pattern were associated with hPL levels, however this was lost on adjustment for BMI at booking, Welsh Index of Multiple Deprivation (WIMD) score and placental weight. When stratified by maternal BMI at booking, a Health Conscious dietary pattern remained associated with increased hPL levels in women with a healthy BMI (p=.024, B=.59. 95% CI=.08,1.11) following adjustment for WIMD score and placental weight. When adjusted for a wide range of confounders, maternal hPL was also associated with increased custom birthweight centiles (CBWC) (p=.014, B=1.64. 95% CI=.33,2.94) and increased odds of large for gestational age deliveries (p=<.001, Exp(B)=1.42. 95% CI=1.17,1.72). This study identified that consuming a Health Conscious dietary pattern in pregnancy was associated with increased hPL, within women of a healthy BMI. Moreover, higher hPL levels were associated with increased CBWC and increased odds of delivering a large for gestational age infant. This improves the current limited evidence surrounding the nature of hPL in these areas.

The Oncogenic Signaling Disruptor, NDRG1: Molecular and Cellular Mechanisms of Activity

NDRG1 is an oncogenic signaling disruptor that plays a key role in multiple cancers, including aggressive pancreatic tumors. Recent studies have indicated a role for NDRG1 in the inhibition of multiple tyrosine kinases, including EGFR, c-Met, HER2 and HER3, etc. The mechanism of activity of NDRG1 remains unclear, but to impart some of its functions, NDRG1 binds directly to key effector molecules that play roles in tumor suppression, e.g., MIG6. More recent studies indicate that NDRG1s-inducing drugs, such as novel di-2-pyridylketone thiosemicarbazones, not only inhibit tumor growth and metastasis but also fibrous desmoplasia, which leads to chemotherapeutic resistance. The Casitas B-lineage lymphoma (c-Cbl) protein may be regulated by NDRG1, and is a crucial E3 ligase that regulates various protein tyrosine and receptor tyrosine kinases, primarily via ubiquitination. The c-Cbl protein can act as a tumor suppressor by promoting the degradation of receptor tyrosine kinases. In contrast, c-Cbl can also promote tumor development by acting as a docking protein to mediate the oncogenic c-Met/Crk/JNK and PI3K/AKT pathways. This review hypothesizes that NDRG1 could inhibit the oncogenic function of c-Cbl, which may be another mechanism of its tumor-suppressive effects.

RNA Network Interactions During Differentiation of Human Trophoblasts

In the human placenta, two trophoblast cell layers separate the maternal blood from the villous basement membrane and fetal capillary endothelial cells. The inner layer, which is complete early in pregnancy and later becomes discontinuous, comprises the proliferative mononuclear cytotrophoblasts, which fuse together and differentiate to form the outer layer of multinucleated syncytiotrophoblasts. Because the syncytiotrophoblasts are responsible for key maternal-fetal exchange functions, tight regulation of this differentiation process is critical for the proper development and the functional role of the placenta. The molecular mechanisms regulating the fusion and differentiation of trophoblasts during human pregnancy remain poorly understood. To decipher the interactions of non-coding RNAs (ncRNAs) in this process, we exposed cultured primary human trophoblasts to standard in vitro differentiation conditions or to conditions known to hinder this differentiation process, namely exposure to hypoxia (O₂ < 1%) or to the addition of dimethyl sulfoxide (DMSO, 1.5%) to the culture medium. Using next generation sequencing technology, we analyzed the differential expression of trophoblastic lncRNAs, miRNAs, and mRNAs that are concordantly modulated by both hypoxia and DMSO. Additionally, we developed a model to construct a lncRNA-miRNA-mRNA co-expression network and inferred the functions of lncRNAs and miRNAs via indirect gene ontology analysis. This study improves our knowledge of the interactions between ncRNAs and mRNAs during trophoblast differentiation and identifies key biological processes that may be impaired in common gestational diseases, such as fetal growth restriction or preeclampsia.

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.

A Comparative Transcriptomic Analysis of Human Placental Trophoblasts in Response to Pathogenic and Probiotic Enterococcus faecalis Interaction

With the ability to cross placental barriers in their hosts, strains of Gram-positive Enterococcus faecalis can exhibit either beneficial or harmful properties. However, the mechanisms underlying these effects have yet to be determined. A comparative transcriptomic analysis of human placental trophoblasts in response to pathogenic or probiotic E. faecalis was performed in order to investigate the molecular basis of different traits. Results indicated that both E. faecalis Symbioflor 1 and V583 could pass through the placental barrier in vitro with similar levels of invasion ability. In total, 2353 (1369 upregulated and 984 downregulated) and 2351 (1233 upregulated and 1118 downregulated) DEGs were identified in Symbioflor 1 and V583, respectively. Furthermore, 1074 (671 upregulated and 403 downregulated) and 1072 (535 upregulated and 537 downregulated) DEGs were only identified in Symbioflor 1 and V583 treatment groups, respectively. KEGG analysis showed that 6 and 9 signaling pathways were associated with interactions between Symbioflor 1 and V583. GO analysis revealed that these DEGs were mainly related to cellular and metabolic processes and biological regulation. However, 28 and 44 DEGs were classified into terms associated with placental and embryonic development in Symbioflor 1 and V583 treatment groups, respectively. Notably, 9 and 25 unique DEGs were identified only in Symbioflor 1 and V583 treatment groups, respectively. A large proportion of transcriptional responses differed when compared between pathogenic and probiotic E. faecalis interaction, and several unique DEGs and signal pathways were identified in the two different groups. These data enhance our understanding of how different traits can be affected by pathogenic and probiotic E. faecalis and the mechanisms underlying these effects.

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.

Low serum placental lactogen at term is associated with postnatal symptoms of depression and anxiety in women delivering female infants

BACKGROUND

Placental endocrine insufficiency may increase the risk of depression and anxiety during pregnancy and/or after birth. This study investigated the association between serum human placental lactogen (hPL) and measures of perinatal mental health, accounting for selective serotonin-reuptake inhibitor (SSRI) usage.

METHOD

Caucasian women with singleton, term pregnancies recruited at their pre-surgical appointment prior to an elective caesarean section (ELCS) were studied. Serum hPL levels were measured by ELISA in maternal blood collected at the pre-surgical appointment. Depression and anxiety scores were derived from Edinburgh Postnatal Depression Scale (EPDS) and the trait subscale of the State-Trait Anxiety Inventory (STAI) questionnaires completed at recruitment and three postnatal time points. Data was analysed by unadjusted and adjusted multiple linear regression.

RESULTS

In adjusted linear regressions, term maternal serum hPL levels were negatively associated with postnatal EPDS and STAI score ten weeks postnatal for mothers who had girls (B= -.367, p = .022, 95% CI -.679, -.056; and B= -.776, p = .030, 95% CI -1.475, -.077 respectively). Excluding women prescribed SSRIs strengthened the relationship at 10 weeks and uncovered an earlier association between hPL and mood scores within one week of delivery (EPDS B= -.357, p = .041, 95 % CI -.698, -.015; and STAI B= -.737, p = .027, 95 % CI -1.387, -.086). In mothers who had boys, there were no associations between hPL and mood scores at any time point.

CONCLUSION

Low hPL at term associated with postnatal depression and anxiety symptoms exclusively in mothers of girls. Insufficiency in hPL may contribute to maternal mood symptoms.

The placental programming hypothesis: Placental endocrine insufficiency and the co-occurrence of low birth weight and maternal mood disorders

Polypeptide hormones and steroid hormones, either expressed by the placenta or dependant on the placenta for their synthesis, are key to driving adaptations in the mother during pregnancy that support growth in utero. These adaptations include changes in maternal behaviour that take place in pregnancy and after the birth to ensure that offspring receive appropriate care and nutrition. Placentally-derived hormones implicated in the programming of maternal caregiving in rodents include prolactin-related hormones and steroid hormones. Neuromodulators produced by the placenta may act directly on the fetus to support brain development. A number of imprinted genes function antagonistically in the placenta to regulate the development of key placental endocrine lineages expressing these hormones. Gain-in-expression of the normally maternally expressed gene Phlda2 or loss-of-function of the normally paternally expressed gene Peg3 results in fewer endocrine cells in the placenta, and pups are born low birth weight. Importantly, wild type dams carrying these genetically altered pups display alterations in their behaviour with decreased focus on nurturing (Phlda2) or heightened anxiety (Peg3). These same genes may regulate placental hormones in human pregnancies, with the potential to influence birth weight and maternal mood. Consequently, the aberrant expression of imprinted genes in the placenta may underlie the reported co-occurrence of low birth weight with maternal prenatal depression.

Sex-Specific Effects of Nanoparticle-Encapsulated MitoQ (nMitoQ) Delivery to the Placenta in a Rat Model of Fetal Hypoxia

Pregnancy complications associated with chronic fetal hypoxia have been linked to the development of adult cardiovascular disease in the offspring. Prenatal hypoxia has been shown to increase placental oxidative stress and impair placental function in a sex-specific manner, thereby affecting fetal development. As oxidative stress is central to placental dysfunction, we developed a placenta-targeted treatment strategy using the antioxidant MitoQ encapsulated into nanoparticles (nMitoQ) to reduce placental oxidative/nitrosative stress and improve placental function without direct drug exposure to the fetus in order to avoid off-target effects during development. We hypothesized that, in a rat model of prenatal hypoxia, nMitoQ prevents hypoxia-induced placental oxidative/nitrosative stress, promotes angiogenesis, improves placental morphology, and ultimately improves fetal oxygenation. Additionally, we assessed whether there were sex differences in the effectiveness of nMitoQ treatment. Pregnant rats were intravenously injected with saline or nMitoQ (100 μl of 125 μM) on gestational day (GD) 15 and exposed to either normoxia (21% O2) or hypoxia (11% O2) from GD15 to 21. On GD21, placentae from both sexes were collected for detection of superoxide, nitrotyrosine, nitric oxide, CD31 (endothelial cell marker), and fetal blood spaces, Vegfa and Igf2 mRNA expression in the placental labyrinth zone. Prenatal hypoxia decreased male fetal weight, which was not changed by nMitoQ treatment; however, placental efficiency (fetal/placental weight ratio) decreased by hypoxia and was increased by nMitoQ in both males and females. nMitoQ treatment reduced the prenatal hypoxia-induced increase in placental superoxide levels in both male and female placentae but improved oxygenation in only female placentae. Nitrotyrosine levels were increased in hypoxic female placentae and were reduced by nMitoQ. Prenatal hypoxia reduced placental Vegfa and Igf2 expression in both sexes, while nMitoQ increased Vegfa and Igf2 expression only in hypoxic female placentae. In summary, our study suggests that nMitoQ treatment could be pursued as a potential preventative strategy against placental oxidative stress and programming of adult cardiovascular disease in offspring exposed to hypoxia in utero. However, sex differences need to be taken into account when developing therapeutic strategies to improve fetal development in complicated pregnancies, as nMitoQ treatment was more effective in placentae from females than males.

PLIN2 Is Essential for Trophoblastic Lipid Droplet Accumulation and Cell Survival During Hypoxia

Trophoblast hypoxia and injury, key components of placental dysfunction, are associated with fetal growth restriction and other complications of pregnancy. Accumulation of lipid droplets has been found in hypoxic nonplacental cells. Unique to pregnancy, lipid accumulation in the placenta might perturb lipid transport to the fetus. We tested the hypothesis that hypoxia leads to accumulation of lipid droplets in human trophoblasts and that trophoblastic PLIN proteins play a key role in this process. We found that hypoxia promotes the accumulation of lipid droplets in primary human trophoblasts. A similar accretion of lipid droplets was found in placental villi in vivo from pregnancies complicated by fetal growth restriction. In both situations, these changes were associated with an increased level of cellular triglycerides. Exposure of trophoblasts to hypoxia led to reduced fatty acid efflux and oxidation with no change in fatty acid uptake or synthesis. We further found that hypoxia markedly stimulated PLIN2 mRNA synthesis and protein expression, which colocalized to lipid droplets. Knockdown of PLIN2, but not PLIN3, enhanced trophoblast apoptotic death, and overexpression of PLIN2 promoted cell viability. Collectively, our data indicate that hypoxia enhances trophoblastic lipid retention in the form of lipid droplets and that PLIN2 plays a key role in this process and in trophoblast defense against apoptotic death. These findings also imply that this protective mechanism may lead to diminished trafficking of lipids to the developing fetus.

Hypoxia and Placental Development

Hemochorial placentation is orchestrated through highly regulated temporal and spatial decisions governing the fate of trophoblast stem/progenitor cells. Trophoblast cell acquisition of specializations facilitating invasion and uterine spiral artery remodeling is a labile process, sensitive to the environment, and represents a process that is vulnerable to dysmorphogenesis in pathologic states. Hypoxia is a signal guiding placental development, and molecular mechanisms directing cellular adaptations to low oxygen tension are integral to trophoblast cell differentiation and placentation. Hypoxia can also be used as an experimental tool to investigate regulatory processes controlling hemochorial placentation. These developmental processes are conserved in mouse, rat, and human placentation. Consequently, elements of these developmental events can be modeled and hypotheses tested in trophoblast stem cells and in genetically manipulated rodents. Hypoxia is also a consequence of a failed placenta, yielding pathologies that can adversely affect maternal adjustments to pregnancy, fetal health, and susceptibility to adult disease. The capacity of the placenta for adaptation to environmental challenges highlights the importance of its plasticity in safeguarding a healthy pregnancy. Birth Defects Research 109:1309-1329, 2017.© 2017 Wiley Periodicals, Inc.

RNA-Seq identifies genes whose proteins are transformative in the differentiation of cytotrophoblast to syncytiotrophoblast, in human primary villous and BeWo trophoblasts

The fusion of villous cytotrophoblasts into the multinucleated syncytiotrophoblast is critical for the essential functions of the mammalian placenta. Using RNA-Seq gene expression and quantitative protein expression, we identified genes and their cognate proteins which are coordinately up- or down-regulated in two cellular models of cytotrophoblast to syncytiotrophoblast development, human primary villous and human BeWo cytotrophoblasts. These include hCGβ, TREML2, PAM, CRIP2, INHA, FLRG, SERPINF1, C17orf96, KRT17 and SAA1. These findings provide avenues for further understanding the mechanisms underlying mammalian placental synctiotrophoblast development.

Placental dysfunction is associated with altered microRNA expression in pregnant women with low folate status

SCOPE

Low maternal folate status during pregnancy increases the risk of delivering small for gestational age (SGA) infants, but the mechanistic link between maternal folate status, SGA, and placental dysfunction is unknown. microRNAs (miRNAs) are altered in pregnancy pathologies and by folate in other systems. We hypothesized that low maternal folate status causes placental dysfunction, mediated by altered miRNA expression.

METHODS AND RESULTS

A prospective observational study recruited pregnant adolescents and assessed third trimester folate status and placental function. miRNA array, QPCR, and bioinformatics identified placental miRNAs and target genes. Low maternal folate status is associated with higher incidence of SGA infants (28% versus 13%, p < 0.05) and placental dysfunction, including elevated trophoblast proliferation and apoptosis (p < 0.001), reduced amino acid transport (p < 0.01), and altered placental hormones (pregnancy-associated plasma protein A, progesterone, and human placental lactogen). miR-222-3p, miR-141-3p, and miR-34b-5p were upregulated by low folate status (p < 0.05). Bioinformatics predicted a gene network regulating cell turnover. Quantitative PCR demonstrated that key genes in this network (zinc finger E-box binding homeobox 2, v-myc myelocytomatosis viral oncogene homolog (avian), and cyclin-dependent kinase 6) were reduced (p < 0.05) in placentas with low maternal folate status.

CONCLUSION

This study supports that placental dysfunction contributes to impaired fetal growth in women with low folate status and suggests altered placental expression of folate-sensitive miRNAs and target genes as a mechanistic link.

Provocative ideas on human placental biology: A prerequisite for prevention and treatment of neonatal health challenges

A 2-day invite-only meeting on generating "Provocative Ideas on human placental research" was organized on 1-2 December 2015 at the Translational Health Science and Technology Institute, Faridabad. This meeting was sponsored by Department of Biotechnology, Ministry of Science and Technology, Govt. of India. The objectives of this meeting were the critical evaluation of placental physiology and its development. Special emphasis was placed on understanding the consequences and implications of placental development in sustenance of pregnancy and in pregnancy-associated complications such as preeclampsia, intrauterine growth restriction, and preterm birth. This meeting brought together experienced as well as novice clinicians and biologists who have a keen interest in the field of placental biology, including development of new technologies and methods for evaluating the role of placenta in predicting pregnancy outcomes. The meeting primarily focused on (i) high-throughput "-omics" approaches, (ii) maternal nutrition and placental function, (iii) placental infection and inflammation, (iv) real-time evaluation of placental development: tools for placental research, and (v) epidemiologic relevance of placental-based research. Unanimous consensus emerged among the participants to carry out additional work focused on these areas. In this article, we summarize the talks and review the published literature on the above-mentioned niches. As a direct outcome of this meeting, a request for applications has been announced by the Department of Biotechnology, Government of India, for pursuing research in this vital but understudied domain.

Increased NDRG1 expression attenuate trophoblast invasion through ERK/MMP-9 pathway in preeclampsia

OBJECTIVE

The aim of this study was to investigate the expression of N-myc downstream-regulated gene1(NDRG1)in the placentas of pregnancies complicated with early-onset and late-onset preeclampsia (PE) and its underlying mechanism on the pathophysiology of PE.

METHODS

The expressions of NDRG-1 in placentas of pregnancies complicated with early-onset PE and late-onset PE were detected using immunohistochemistry, western blot assays and fluorescence quantitative PCR. The expressions of MMP-2, MMP-9 and ERK1/2 protein were detected by western blot analysis and cell invasion assay was performed using transwell chambers in NDRG1 silenced JEG-3 cells.

RESULTS

Compared with the normal term pregnancies, the expression of both NDRG1 mRNA and protein were significantly high in placentas from PE, and the expression of NDRG1 in early-onset PE was higher than that in late-onset PE. In NDRG1-silenced JEG-3 cells, MMP-2, MMP-9 and phosphorylation of ERK1/2 protein increased obviously and the number of cells that penetrated the membrane increased.

CONCLUSION

Upregulation of NDRG1 is associated with impaired trophoblast invasion in PE by inhibition ERK/MMP-2 and MMP-9 Pathway.

Maternal prenatal depression is associated with decreased placental expression of the imprinted gene PEG3

BACKGROUND

Maternal prenatal stress during pregnancy is associated with fetal growth restriction and adverse neurodevelopmental outcomes, which may be mediated by impaired placental function. Imprinted genes control fetal growth, placental development, adult behaviour (including maternal behaviour) and placental lactogen production. This study examined whether maternal prenatal depression was associated with aberrant placental expression of the imprinted genes paternally expressed gene 3 (PEG3), paternally expressed gene 10 (PEG10), pleckstrin homology-like domain family a member 2 (PHLDA2) and cyclin-dependent kinase inhibitor 1C (CDKN1C), and resulting impaired placental human placental lactogen (hPL) expression.

METHOD

A diagnosis of depression during pregnancy was recorded from Manchester cohort participants' medical notes (n = 75). Queen Charlotte's (n = 40) and My Baby and Me study (MBAM) (n = 81) cohort participants completed the Edinburgh Postnatal Depression Scale self-rating psychometric questionnaire. Villous trophoblast tissue samples were analysed for gene expression.

RESULTS

In a pilot study, diagnosed depression during pregnancy was associated with a significant reduction in placental PEG3 expression (41%, p = 0.02). In two further independent cohorts, the Queen Charlotte's and MBAM cohorts, placental PEG3 expression was also inversely associated with maternal depression scores, an association that was significant in male but not female placentas. Finally, hPL expression was significantly decreased in women with clinically diagnosed depression (44%, p < 0.05) and in those with high depression scores (31% and 21%, respectively).

CONCLUSIONS

This study provides the first evidence that maternal prenatal depression is associated with changes in the placental expression of PEG3, co-incident with decreased expression of hPL. This aberrant placental gene expression could provide a possible mechanistic explanation for the co-occurrence of maternal depression, fetal growth restriction, impaired maternal behaviour and poorer offspring outcomes.

A Role for the Placenta in Programming Maternal Mood and Childhood Behavioural Disorders

Substantial data demonstrate that the early-life environment, including in utero, plays a key role in later life disease. In particular, maternal stress during pregnancy has been linked to adverse behavioural and emotional outcomes in children. Data from human cohort studies and experimental animal models suggest that modulation of the developing epigenome in the foetus by maternal stress may contribute to the foetal programming of disease. Here, we summarise insights gained from recent studies that may advance our understanding of the role of the placenta in mediating the association between maternal mood disorders and offspring outcomes. First, the placenta provides a record of exposures during pregnancy, as indicated by changes in the placental trancriptome and epigenome. Second, prenatal maternal mood may alter placental function to adversely impact foetal and child development. Finally, we discuss the less well established but interesting possibility that altered placental function, more specifically changes in placental hormones, may adversely affect maternal mood and later maternal behaviour, which can also have consequence for offspring well-being.

Placental Underperfusion in a Rat Model of Intrauterine Growth Restriction Induced by a Reduced Plasma Volume Expansion

Lower maternal plasma volume expansion was found in idiopathic intrauterine growth restriction (IUGR) but the link remains to be elucidated. An animal model of IUGR was developed by giving a low-sodium diet to rats over the last week of gestation. This treatment prevents full expansion of maternal circulating volume and the increase in uterine artery diameter, leading to reduced placental weight compared to normal gestation. We aimed to verify whether this is associated with reduced remodeling of uteroplacental circulation and placental hypoxia. Dams were divided into two groups: IUGR group and normal-fed controls. Blood velocity waveforms in the main uterine artery were obtained by Doppler sonography on days 14, 18 and 21 of pregnancy. On day 22 (term = 23 days), rats were sacrificed and placentas and uterine radial arteries were collected. Diameter and myogenic response of uterine arteries supplying placentas were determined while expression of hypoxia-modulated genes (HIF-1α, VEGFA and VEGFR2), apoptotic enzyme (Caspase -3 and -9) and glycogen cells clusters were measured in control and IUGR term-placentas. In the IUGR group, impaired blood velocity in the main uterine artery along with increased resistance index was observed without alteration in umbilical artery blood velocity. Radial uterine artery diameter was reduced while myogenic response was increased. IUGR placentas displayed increased expression of hypoxia markers without change in the caspases and increased glycogen cells in the junctional zone. The present data suggest that reduced placental and fetal growth in our IUGR model may be mediated, in part, through reduced maternal uteroplacental blood flow and increased placental hypoxia.

Placental expression of imprinted genes varies with sampling site and mode of delivery

Imprinted genes, which are monoallelically expressed by virtue of an epigenetic process initiated in the germline, are known to play key roles in regulating fetal growth and placental development. Numerous studies are investigating the expression of these imprinted genes in the human placenta in relation to common complications of pregnancy such as fetal growth restriction and preeclampsia. This study aimed to determine whether placental sampling protocols or other factors such as fetal sex, gestational age and mode of delivery may influence the expression of imprinted genes predicted to regulate placental signalling.

METHODS

Term placentas were collected from Caucasian women delivering at University Hospital of Wales or Royal Gwent Hospital within two hours of delivery. Expression of the imprinted genes PHLDA2, CDKN1C, PEG3 and PEG10 was assayed by quantitative real time PCR. Intraplacental gene expression was analysed (N = 5). Placental gene expression was compared between male (N = 11) and female (N = 11) infants, early term (N = 8) and late term (N = 10) deliveries and between labouring (N = 13) and non-labouring (N = 21) participants.

RESULTS

The paternally expressed imprinted genes PEG3 and PEG10 were resilient to differences in sampling site, fetal sex, term gestational age and mode of delivery. The maternally expressed imprinted gene CDKN1C was elevated over 2-fold (p < 0.001) in placenta from labouring deliveries compared with elective caesarean sections. In addition, the maternally expressed imprinted gene PHLDA2 was elevated by 1.8 fold (p = 0.01) in samples taken at the distal edge of the placenta compared to the cord insertion site.

CONCLUSION

These findings support the reinterpretation of existing data sets on these genes in relation to complications of pregnancy and further reinforce the importance of optimising and unifying placental collection protocols for future studies.

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.

Loss of inherited genomic imprints in mice leads to severe disruption in placental lipid metabolism

INTRODUCTION

Monoallelic expression of imprinted genes is necessary for placental development and normal fetal growth. Differentially methylated domains (DMDs) largely determine the parental-specific monoallelic expression of imprinted genes. Maternally derived DNA (cytosine-5-) -methyltransferase 1o (DNMT1o) maintains DMDs during the eight-cell stage of development. DNMT1o-deficient mouse placentas have a generalized disruption of genomic imprints. Previous studies have demonstrated that DNMT1o deficiency alters placental morphology and broadens the embryonic weight distribution in late gestation. Lipids are critical for fetal growth. Thus, we assessed the impact of disrupted imprinting on placental lipids.

METHODS

Lipids were quantified from DNMT1o-deficient mouse placentas and embryos at E17.5 using a modified Folch method. Expression of select genes critical for lipid metabolism was quantified with RT-qPCR. Mitochondrial morphology was assessed by TEM and mitochondrial aconitase and cytoplasmic citrate concentrations quantified. DMD methylation was determined by EpiTYPER.

RESULTS

We found that DNMT1o deficiency is associated with increased placental triacylglycerol levels. Neither fetal triacylglycerol concentrations nor expression of select genes that mediate placental lipid transport were different from wild type. Placental triacylglycerol accumulation was associated with impaired beta-oxidation and abnormal citrate metabolism with decreased mitochondrial aconitase activity and increased cytoplasmic citrate concentrations. Loss of methylation at the MEST DMD was strongly associated with placental triacylglycerol accumulation.

DISCUSSION

A generalized disruption of genomic imprints leads to triacylglycerol accumulation and abnormal mitochondrial function. This could stem directly from a loss of methylation at a given DMD, such as MEST, or represent a consequence of abnormal placental development.

The assembly of miRNA-mRNA-protein regulatory networks using high-throughput expression data

MOTIVATION

Inference of gene regulatory networks from high throughput measurement of gene and protein expression is particularly attractive because it allows the simultaneous discovery of interactive molecular signals for numerous genes and proteins at a relatively low cost.

RESULTS

We developed two score-based local causal learning algorithms that utilized the Markov blanket search to identify direct regulators of target mRNAs and proteins. These two algorithms were specifically designed for integrated high throughput RNA and protein data. Simulation study showed that these algorithms outperformed other state-of-the-art gene regulatory network learning algorithms. We also generated integrated miRNA, mRNA, and protein expression data based on high throughput analysis of primary trophoblasts, derived from term human placenta and cultured under standard or hypoxic conditions. We applied the new algorithms to these data and identified gene regulatory networks for a set of trophoblastic proteins found to be differentially expressed under the specified culture conditions.

Abnormal oxidative stress responses in fibroblasts from preeclampsia infants

Background

Signs of severe oxidative stress are evident in term placentae of infants born to mothers with preeclampsia (PE), but it is unclear whether this is a cause or consequence of the disease. Here fibroblast lines were established from umbilical cords (UC) delivered by mothers who had experienced early onset PE and from controls with the goal of converting these primary cells to induced pluripotent stem cells and ultimately trophoblast. Contrary to expectations, the oxidative stress responses of these non-placental cells from PE infants were more severe than those from controls.

Methods and Findings

Three features suggested that UC-derived fibroblasts from PE infants responded less well to oxidative stressors than controls: 1) While all UC provided outgrowths in 4% O₂, success was significantly lower for PE cords in 20% O₂; 2) PE lines established in 4% O₂ proliferated more slowly than controls when switched to 20% O₂; 3) PE lines were more susceptible to the pro-oxidants diethylmaleate and tert-butylhydroquinone than control lines, but, unlike controls, were not protected by glutathione. Transcriptome profiling revealed only a few genes differentially regulated between PE lines and controls in 4% O₂ conditions. However, a more severely stressed phenotype than controls, particularly in the unfolded protein response, was evident when PE lines were switched suddenly to 20% O₂, thus confirming the greater sensitivity of the PE fibroblasts to acute changes in oxidative stress.

Conclusions

UC fibroblasts derived from PE infants are intrinsically less able to respond to acute oxidative stress than controls, and this phenotype is retained over many cell doublings. Whether the basis of this vulnerability is genetic or epigenetic and how it pertains to trophoblast development remains unclear, but this finding may provide a clue to the basis of the early onset, usually severe, form of PE.

Cell fusion mediates dramatic alterations in the actin cytoskeleton, focal adhesions, and E-cadherin in trophoblastic cells

The syncytiotrophoblast of the human placenta is a unique epithelia structure with millions of nuclei sharing a common cytoplasm. The syncytiotrophoblast forms by cell-cell fusion of cytotrophoblasts (CTB), the mononuclear precursor cells. The trophoblastic BeWo cell line has been used as a surrogate for CTB since they can be induced to fuse, and subsequently display numerous syncytiotrophoblast differentiation markers following syncytial formation. In this study, we have focused on alterations in the cell-adhesion molecule E-cadherin, actin cytoskeleton, and focal adhesions following BeWo cell fusion, since these entities may be interrelated. There was a dramatic reorganization of the distribution of E-cadherin as well as a reduction in the amount of E-cadherin following cell fusion. Reorganization of the actin cytoskeleton was also observed, which was associated with a change in the globular actin (G-actin)/filamentous actin (F-actin) ratio. Concomitantly, the morphology of focal adhesions was altered, but this occurred without a corresponding change in the levels of focal adhesion marker proteins. Thus, extensive remodeling of the actin cytoskeleton and focal adhesions accompanies cell fusion and differentiation and appears related to alterations in E-cadherin in trophoblastic cells.

NDRG1 deficiency attenuates fetal growth and the intrauterine response to hypoxic injury

Intrauterine mammalian development depends on the preservation of placental function. The expression of the protein N-myc downstream-regulated gene 1 (NDRG1) is increased in placentas of human pregnancies affected by fetal growth restriction and in hypoxic primary human trophoblasts, where NDRG1 attenuates cell injury. We sought to assess the function of placental NDRG1 in vivo and tested the hypothesis that NDRG1 deficiency in the mouse embryo impairs placental function and consequently intrauterine growth. We found that Ndrg1 knock-out embryos were growth restricted in comparison to wild-type or heterozygous counterparts. Furthermore, hypoxia reduced the survival of female, but not male, knock-out embryos. Ndrg1 deletion caused significant alterations in placental gene expression, with a marked reduction in transcription of several lipoproteins in the placental labyrinth. These transcriptional changes were associated with reduced fetal:maternal serum cholesterol ratio exclusively in hypoxic female embryos. Collectively, our findings indicate that NDRG1 promotes fetal growth and regulates the metabolic response to intrauterine hypoxic injury in a sexually dichotomous manner.

Molecular functions of the iron-regulated metastasis suppressor, NDRG1, and its potential as a molecular target for cancer therapy

N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.

The expression and localization of N-myc downstream-regulated gene 1 in human trophoblasts

The protein N-Myc downstream-regulated gene 1 (NDRG1) is implicated in the regulation of cell proliferation, differentiation, and cellular stress response. NDRG1 is expressed in primary human trophoblasts, where it promotes cell viability and resistance to hypoxic injury. The mechanism of action of NDRG1 remains unknown. To gain further insight into the intracellular action of NDRG1, we analyzed the expression pattern and cellular localization of endogenous NDRG1 and transfected Myc-tagged NDRG1 in human trophoblasts exposed to diverse injuries. In standard conditions, NDRG1 was diffusely expressed in the cytoplasm at a low level. Hypoxia or the hypoxia mimetic cobalt chloride, but not serum deprivation, ultraviolet (UV) light, or ionizing radiation, induced the expression of NDRG1 in human trophoblasts and the redistribution of NDRG1 into the nucleus and cytoplasmic membranes associated with the endoplasmic reticulum (ER) and microtubules. Mutation of the phosphopantetheine attachment site (PPAS) within NDRG1 abrogated this pattern of redistribution. Our results shed new light on the impact of cell injury on NDRG1 expression patterns, and suggest that the PPAS domain plays a key role in NDRG1’s subcellular distribution.

Homeobox gene transforming growth factor β-induced factor-1 (TGIF-1) is a regulator of villous trophoblast differentiation and its expression is increased in human idiopathic fetal growth restriction

Abnormal trophoblast function is associated with human fetal growth restriction (FGR). Targeted disruption of homeobox gene transforming growth β-induced factor (TGIF-1) results in placental dysfunction in the mouse. The role of human TGIF-1 in placental cell function is unknown. The aims of this study were to determine the expression of TGIF-1 in human idiopathic FGR-affected placentae compared with gestation-matched controls (GMC), to elucidate the functional role of TGIF-1 in trophoblasts and to identify its downstream targets. Real-time PCR and immunoblotting revealed that TGIF-1 mRNA and protein expression was significantly increased in FGR-affected placentae compared with GMC (n = 25 in each group P < 0.05). Immunoreactive TGIF-1 was localized to the villous cytotrophoblasts, syncytiotrophoblast, microvascular endothelial cells and in scattered stromal cells in both FGR and GMC. TGIF-1 inactivation in BeWo cells using two independent siRNA resulted in significantly decreased mRNA and protein of trophoblast differentiation markers, human chorionic gonadotrophin (CGB/hCG), syncytin and 3β-hydroxysteroid dehydrogenase/3β-honest significant difference expression. Our data demonstrate that homeobox gene TGIF-1 is a potential up-stream regulator of trophoblast differentiation and the altered TGIF-1 expression may contribute to aberrant villous trophoblast differentiation in FGR.

EG-VEGF controls placental growth and survival in normal and pathological pregnancies: case of fetal growth restriction (FGR)

Identifiable causes of fetal growth restriction (FGR) account for 30 % of cases, but the remainders are idiopathic and are frequently associated with placental dysfunction. We have shown that the angiogenic factor endocrine gland-derived VEGF (EG-VEGF) and its receptors, prokineticin receptor 1 (PROKR1) and 2, (1) are abundantly expressed in human placenta, (2) are up-regulated by hypoxia, (3) control trophoblast invasion, and that EG-VEGF circulating levels are the highest during the first trimester of pregnancy, the period of important placental growth. These findings suggest that EG-VEGF/PROKR1 and 2 might be involved in normal and FGR placental development. To test this hypothesis, we used placental explants, primary trophoblast cultures, and placental and serum samples collected from FGR and age-matched control women. Our results show that (1) EG-VEGF increases trophoblast proliferation ([(3)H]-thymidine incorporation and Ki67-staining) via the homeobox-gene, HLX (2) the proliferative effect involves PROKR1 but not PROKR2, (3) EG-VEGF does not affect syncytium formation (measurement of syncytin 1 and 2 and β hCG production) (4) EG-VEGF increases the vascularization of the placental villi and insures their survival, (5) EG-VEGF, PROKR1, and PROKR2 mRNA and protein levels are significantly elevated in FGR placentas, and (6) EG-VEGF circulating levels are significantly higher in FGR patients. Altogether, our results identify EG-VEGF as a new placental growth factor acting during the first trimester of pregnancy, established its mechanism of action, and provide evidence for its deregulation in FGR. We propose that EG-VEGF/PROKR1 and 2 increases occur in FGR as a compensatory mechanism to insure proper pregnancy progress.

Hypoxia alters the epigenetic profile in cultured human placental trophoblasts

The mechanisms by which the placenta adapts to exogenous stimuli to create a stable and healthy environment for the growing fetus are not well known. Low oxygen tension influences placental function, and is associated with preeclampsia, a condition displaying altered development of placental trophoblast. We hypothesized that oxygen tension affects villous trophoblast by modulation of gene expression through DNA methylation. We used the Infinium HumanMethylation450 BeadChip array to compare the DNA methylation profile of primary cultures of human cytotrophoblasts and syncytiotrophoblasts under < 1%, 8% and 20% oxygen levels. We found no effect of oxygen tension on average DNA methylation for either cell phenotype, but a set of loci became hypermethylated in cytotrophoblasts exposed for 24 h to < 1% oxygen, as compared with those exposed to 8% or 20% oxygen. Hypermethylation with low oxygen tension was independently confirmed by bisulfite-pyrosequencing in a subset of functionally relevant genes including CD59, CFB, GRAM3 and ZNF217. Intriguingly, 70 out of the 147 CpGs that became hypermethylated in < 1% oxygen overlapped with CpG sites that became hypomethylated upon differentiation of cytotrophoblasts into syncytiotrophoblasts. Furthermore, the preponderance of altered sites was located at AP-1 binding sites. We suggest that AP-1 expression is triggered by hypoxia and interacts with DNA methyltransferases (DNMTs) to target methylation at specific sites in the genome, thus causing suppression of the associated genes that are responsible for differentiation of villous cytotrophoblast to syncytiotrophoblast.

The dysfunctional placenta epigenome: causes and consequences

The placenta is a fetal–maternal endocrine organ responsible for ensuring proper fetal development throughout pregnancy. Adverse insults to the intrauterine environment often lead to expression level changes in placental genes, many of which are epigenetically regulated by DNA methylation, histone modifications and ncRNA interference. These epigenetic alterations may cause placental dysfunction, resulting in offspring of low birthweight owing to adverse pregnancy complications such as intrauterine growth restriction. Numerous epidemiological studies have shown a strong correlation between low birthweight and increased risk of developing metabolic diseases and neurological imbalances in adulthood, and in subsequent generations, indicating that epigenetic regulation of gene expression can be propagated stably with long-term effects on health. This article provides an overview of the various environmental factors capable of inducing detrimental changes to the placental epigenome, as well as the corresponding mechanisms that prime the offspring for onset of disease later in life.

The role of homeobox genes in the development of placental insufficiency

Intrauterine growth restriction (IUGR) is an adverse pregnancy outcome associated with significant perinatal and pediatric morbidity and mortality, and an increased risk of chronic disease later in adult life. While a number of maternal, fetal and environmental factors are known causes of IUGR, the majority of IUGR cases are of unknown cause. These IUGR cases are frequently associated with placental insufficiency, possibly as a result of placental maldevelopment. Understanding the molecular mechanisms of abnormal placental development in IUGR associated with placental insufficiency is therefore of increasing importance. Here, we review our understanding of transcriptional control of normal placental development as well as human IUGR associated with placental insufficiency. We also assess the potential for understanding transcriptional control as a means for revealing new molecular targets for the detection, diagnosis and clinical management of IUGR associated with placental insufficiency.

The expression profile of C19MC microRNAs in primary human trophoblast cells and exosomes

The largest gene cluster of human microRNAs (miRNAs), the chromosome 19 miRNA cluster (C19MC), is exclusively expressed in the placenta and in undifferentiated cells. The precise expression pattern and function of C19MC members are unknown. We sought to profile the relative expression of C19MC miRNAs in primary human trophoblast (PHT) cells and exosomes. Using high-throughput profiling, confirmed by PCR, we found that C19MC miRNAs are among the most abundant miRNAs in term human trophoblasts. Hypoxic stress selectively reduced miR-520c-3p expression at certain time-points with no effect on other C19MC miRNAs. Similarly, differentiation in vitro had a negligible effect on C19MC miRNAs. We found that C19MC miRNAs are the predominant miRNA species expressed in exosomes released from PHT, resembling the profile of trophoblastic cellular miRNA. Predictably, we detected the similar levels of circulating C19MC miRNAs in the serum of healthy pregnant women at term and in women with pregnancies complicated by fetal growth restriction. Our data define the relative expression levels of C19MC miRNAs in trophoblasts and exosomes, and suggest that C19MC miRNAs function in placental-maternal signaling.

The expression and function of fatty acid transport protein-2 and -4 in the murine placenta

Background

The uptake and trans-placental trafficking of fatty acids from the maternal blood into the fetal circulation are essential for embryonic development, and involve several families of proteins. Fatty acid transport proteins (FATPs) uniquely transport fatty acids into cells. We surmised that placental FATPs are germane for fetal growth, and are regulated during hypoxic stress, which is associated with reduced fat supply to the fetus.

Methodology/Principal Findings

Using cultured primary term human trophoblasts we found that FATP2, FATP4 and FATP6 were highly expressed in trophoblasts. Hypoxia enhanced the expression of trophoblastic FATP2 and reduced the expression of FATP4, with no change in FATP6. We also found that Fatp2 and Fatp4 are expressed in the mouse amnion and placenta, respectively. Mice deficient in Fatp2 or Fatp4 did not deviate from normal Mendelian distribution, with both embryos and placentas exhibiting normal weight and morphology, triglyceride content, and expression of genes related to fatty acid mobilization.

Conclusions/Significance

We conclude that even though hypoxia regulates the expression of FATP2 and FATP4 in human trophoblasts, mouse Fatp2 and Fatp4 are not essential for intrauterine fetal growth.

The timing and duration of hypoxia determine gene expression patterns in cultured human trophoblasts

OBJECTIVE

Exposure of cultured trophoblasts to hypoxia is commonly used to interrogate the molecular mechanisms underlying placental hypoxic injury. We examined the effect of levels, durations, and patterns of hypoxia on gene expression patterns in primary human trophoblasts.

STUDY DESIGN

We exposed primary term human trophoblasts to either standard culture conditions (O(2) = 20%) or to static or alternating levels of oxygen (O(2) = 8%, or O(2) = 0%) either early or late in culture, and analyzed the expression of 34 genes that are known to be regulated in placentas from pregnancies complicated by fetal growth restriction (FGR).

RESULTS

Using multidimensional scale analysis, Euclidean distance, and hierarchical clustering, we found that gene expression patterns in cells exposed to O(2) = 8% were similar to patterns observed in O(2) = 20%, but more distant from patterns in O(2) = 0%. Alternating atmospheric oxygen (8% vs. 0%) yielded intermediate results. Changes in oxygen levels over a longer period had a greater effect on gene expression than short-term changes. Gene expression patterns in cultured trophoblasts did not fully capture expression patterns observed in biopsies from FGR placentas vs. control.

CONCLUSIONS

The level, duration, and patterns of hypoxia are critical in determining trophoblast gene expression, and therefore germane for analysis of trophoblast hypoxic injury.

Comparative gene expression profiling of placentas from patients with severe pre-eclampsia and unexplained fetal growth restriction

BACKGROUND

It has been well documented that pre-eclampsia and unexplained fetal growth restriction (FGR) have a common etiological background, but little is known about their linkage at the molecular level. The aim of this study was to further investigate the mechanisms underlying pre-eclampsia and unexplained FGR.

METHODS

We analyzed differentially expressed genes in placental tissue from severe pre-eclamptic pregnancies (n = 8) and normotensive pregnancies with or (n = 8) without FGR (n = 8) using a microarray method.

RESULTS

A subset of the FGR samples showed a high correlation coefficient overall in the microarray data from the pre-eclampsia samples. Many genes that are known to be up-regulated in pre-eclampsia are also up-regulated in FGR, including the anti-angiogenic factors, FLT1 and ENG, believed to be associated with the onset of maternal symptoms of pre-eclampsia. A total of 62 genes were found to be differentially expressed in both disorders. However, gene set enrichment analysis for these differentially expressed genes further revealed higher expression of TP53-downstream genes in pre-eclampsia compared with FGR. TP53-downstream apoptosis-related genes, such as BCL6 and BAX, were found to be significantly more up-regulated in pre-eclampsia than in FGR, although the caspases are expressed at equivalent levels.

CONCLUSIONS

Our current data indicate a common pathophysiology for FGR and pre-eclampsia, leading to an up-regulation of placental anti-angiogenic factors. However, our findings also suggest that it may possibly be the excretion of these factors into the maternal circulation through the TP53-mediated early-stage apoptosis of trophoblasts that leads to the maternal symptoms of pre-eclampsia.

Identification of maternally regulated fetal gene networks in the placenta with a novel embryo transfer system in mice

The mechanisms for provisioning maternal resources to offspring in placental mammals involve complex interactions between maternally regulated and fetally regulated gene networks in the placenta, a tissue that is derived from the zygote and therefore of fetal origin. Here we describe a novel use of an embryo transfer system in mice to identify gene networks in the placenta that are regulated by the mother. Mouse embryos from the same strain of inbred mice were transferred into a surrogate mother either of the same strain or from a different strain, allowing maternal and fetal effects on the placenta to be separated. After correction for sex and litter size, maternal strain overrode fetal strain as the key determinant of fetal weight (P < 0.0001). Computational filtering of the placental transcriptome revealed a group of 81 genes whose expression was solely dependent on the maternal strain [P < 0.05, false discovery rate (FDR) < 0.10]. Network analysis of this group of genes yielded highest statistical significance for pathways involved in the regulation of cell growth (such as insulin-like growth factors) as well as those involved in regulating lipid metabolism [such as the low-density lipoprotein receptor-related protein 1 (LRP1), LDL, and HDL], both of which are known to play a role in fetal development. This novel technique may be generally applied to identify regulatory networks involved in maternal-fetal interaction and eventually help identify molecular targets in disorders of fetal growth.

The role of placental homeobox genes in human fetal growth restriction

Fetal growth restriction (FGR) is an adverse pregnancy outcome associated with significant perinatal and paediatric morbidity and mortality, and an increased risk of chronic disease later in adult life. One of the key causes of adverse pregnancy outcome is fetal growth restriction (FGR). While a number of maternal, fetal, and environmental factors are known causes of FGR, the majority of FGR cases remain idiopathic. These idiopathic FGR pregnancies are frequently associated with placental insufficiency, possibly as a result of placental maldevelopment. Understanding the molecular mechanisms of abnormal placental development in idiopathic FGR is, therefore, of increasing importance. Here, we review our understanding of transcriptional control of normal placental development and abnormal placental development associated with human idiopathic FGR. We also assess the potential for understanding transcriptional control as a means for revealing new molecular targets for the detection, diagnosis, and clinical management of idiopathic FGR.

Diagnosis and management of fetal growth restriction

Fetal growth restriction (FGR) remains a leading contributor to perinatal mortality and morbidity and metabolic syndrome in later life. Recent advances in ultrasound and Doppler have elucidated several mechanisms in the evolution of the disease. However, consistent classification and characterization regarding the severity of FGR is lacking. There is no cure, and management is reliant on a structured antenatal surveillance program with timely intervention. Hitherto, the time to deliver is an enigma. In this paper, the challenges in the diagnosis and management of FGR are discussed. The biophysical profile, Doppler, biochemical and molecular technologies that may refine management are reviewed. Finally, a model pathway for the clinical management of pregnancies complicated by FGR is presented.

Late-gestational systemic hypoxia leads to a similar early gene response in mouse placenta and developing brain

Late-gestational intrauterine hypoxia represents a well-known risk factor of acquired perinatal brain injury. Cell type and age-specific sensitivity of hypoxia-responsive genes to low-oxygen partial pressure is to be considered in the screening for early indicators of fetoplacental tissue hypoxia. To identify early hypoxia-induced alterations in gene expression during late-gestational hypoxia (6% O2, 6 h; gestational day 20) we compared primary mouse placenta and brain transcriptomes using high-density oligonucleotide microarrays. Upregulation of candidate marker genes for hypoxia was confirmed by quantitative RT-PCR and immunohistochemistry. Both developing brain and placenta were highly responsive to systemic hypoxia at the level of gene expression involving hypoxia-inducible transcription factor (HIF)-dependent genes and immediate early genes (IEG) (Fos, Jun, Egr1, Bhlhb2), apoptosis-promoting factors (Bnip3, Dusp1, Ier3) that were all upregulated, and genes modulating RNA binding and translation (Rbm3, Thap2, Lig4, Rbm12b) that mainly were downregulated. Functional activity of the HIF system was obvious from elevated expression of various known HIF target genes (Adm, Vegf, Hk2, Pdk1, Bnip3, Ier3, Dusp-1), indicating immediate availability among early response to acute hypoxia. In addition, genes not yet described as being hypoxia related were identified that are involved in angiogenesis/cell differentiation (Gna13, Gab2), mRNA processing, and embryonic development. RT-PCR of placenta and brain tissues confirmed upregulation of selected HIF target genes and IEG. These data indicate that the early hypoxia-induced genomic response of the placenta mirrors that of developing brain in a temporally parallel manner. Our observations implicate future diagnostic options to identify fetal and cerebral tissue hypoxia.

CTGF expression is up-regulated by PROK1 in early pregnancy and influences HTR-8/Svneo cell adhesion and network formation

BACKGROUND

Prokineticin-1 (PROK1) and connective tissue growth factor (CTGF) are expressed in human endometrium and first-trimester decidua and have individually been proposed to have roles in implantation and placentation. We have recently demonstrated that CTGF may be a target gene for PROK1 in gene array analysis of a prokineticin receptor-1 stably transfected Ishikawa endometrial epithelial cell line (PROKR1-Ishikawa). The first aim of the study was to determine the effect of PROK1 on CTGF expression in PROKR1-Ishikawa cells and first-trimester decidua samples. Secondly, the effect of CTGF on trophoblast-derived HTR-8/SVneo cell adhesion and network formation was investigated.

METHODS AND RESULTS

Real-time qPCR showed that CTGF expression is elevated in first-trimester decidua compared with non-pregnant endometrium. In decidua, CTGF co-localized with PROKR1 to the glandular epithelium and a subset of stromal cells. PROK1 increased CTGF mRNA and protein expression in PROKR1-Ishikawa cells and first-trimester human decidua (8–12 weeks gestation). Knock down of endogenous PROK1 using micro RNA constructs targeted at PROK1, resulted in decreased expression of CTGF mRNA and protein in decidua. Inhibitors of specific cell signalling molecules demonstrated that PROK1 regulates CTGF expression via the Gq, phospholipase C (PLC), cSrc, epidermal growth factor receptor (EGFR), mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) kinase pathway activation. Treatment of trophoblast-derived HTR-8/Svneo cells with 1 µg/ml CTGF significantly increased adhesion to collagen IV, and differentiation of the cells into tube-like structures in matrigel.

CONCLUSIONS

CTGF expression in early pregnancy decidua is regulated by PROK1, via activation of the Gq, PLC, cSrc, EGFR, MAPK/ERK kinase pathway. CTGF in turn may contribute to the regulation of trophoblast conversion of maternal spiral arteries.

Periodontal pathogen Aggregatibacter actinomycetemcomitans LPS induces mitochondria-dependent-apoptosis in human placental trophoblasts

OBJECTIVE

Increasing evidence suggests an association between periodontal disease and low birthweight (LBW); however the underlying molecular mechanisms are yet to be fully elucidated. In this study, we performed a microarray analysis to observe the human placental trophoblast-like BeWo cells response to lipopolysaccharide (LPS) from periodontopathogen Aggregatibacter actinomycetemcomitans (Aa), in order to investigate the molecular basis of mechanisms for periodontitis-associated LBW. In vivo pregnant rats were also used to confirm the in vitro results.

STUDY DESIGN

The effects of Aa-LPS on cultured human placental trophoblast-like BeWo cells were studied using a DNA microarray, Ingenuity Pathway Analysis, real-time PCR and poly-caspase staining. The in vivo effects of Aa-LPS in pregnant rats were examined using TUNEL assays.

RESULTS

In BeWo cells, Aa-LPS increased levels of cytochrome c, caspase 2, caspase 3, caspase 9 and BCL2-antagonist/killer 1 mRNA, decreased those of B-cell CLL/lymphoma 2, BCL2-like 1 and catalase mRNA and increased poly-caspase activity, all of which are consistent with activation of the mitochondria-dependent apoptotic pathway. TUNEL assays confirmed the increased incidence of apoptosis in placentas of Aa-LPS-treated rats (p < 0.001).

CONCLUSION

Aa-LPS induces apoptosis in human trophoblasts via the mitochondria-dependent pathway, and this effect may contribute to the pathogenesis of periodontitis-associated LBW.

The N-myc downstream regulated gene (NDRG) family: diverse functions, multiple applications

The N-myc downstream regulated gene (NDRG) family of proteins consists of 4 members, NDRG1-4, which are well conserved through evolution. The first member to be discovered and responsible for the family name was NDRG1, because its expression is repressed by the proto-oncogenes MYCN and MYC. All family members are characterized by an α/β hydrolase-fold motif; however, the precise molecular and cellular function of these family members has not been fully elucidated. Although the exact function of NDRG family members has not been clearly elucidated, emerging evidence suggests that mutations in these genes are associated with diverse neurological and electrophysiological syndromes. In addition, aberrant expression as well as tumor suppressor and oncogenic functions affecting key hallmarks of carcinogenesis such as cell proliferation, differentiation, migration, invasion, and stress response have been reported for several of the NDRG proteins. In this review, we summarize the current literature on the NDRG family members concerning their structure, origin, and tissue distribution. In addition, we review the current knowledge regarding the regulation and signaling of the NDRG family members in development and normal physiology. Finally, their role in disease and potential clinical applications (their role as detection or prognostic markers) are discussed.