Microarray analysis of trophoblast differentiation: gene expression reprogramming in key gene function categories

Pro-angiogenic effects of pregnancy-specific glycoproteins in endothelial and extravillous trophoblast cells

We previously reported that binding to heparan sulfate (HS) is required for the ability of the placentally secreted pregnancy-specific glycoprotein 1 (PSG1) to induce endothelial tubulogenesis. PSG1 is composed of four immunoglobulin-like domains but which domains of the protein bind to HS remains unknown. To analyze the interaction of PSG1 with HS, we generated several recombinant proteins, including the individual domains, chimeric proteins between two PSG1 domains, and mutants. Using flow cytometric and surface plasmon resonance studies, we determined that the B2 domain of PSG1 binds to HS and that the positively charged amino acids encompassed between amino acids 43-59 are required for this interaction. Furthermore, we showed that the B2 domain of PSG1 is required for the increase in the formation of tubes by endothelial cells (EC) including a human endometrial EC line and two extravillous trophoblast (EVT) cell lines and for the pro-angiogenic activity of PSG1 observed in an aortic ring assay. PSG1 enhanced the migration of ECs while it increased the expression of matrix metalloproteinase-2 in EVTs, indicating that the pro-angiogenic effect of PSG1 on these two cell types may be mediated by different mechanisms. Despite differences in amino acid sequence, we observed that all human PSGs bound to HS proteoglycans and confirmed that at least two other members of the family, PSG6 and PSG9, induce tube formation. These findings contribute to a better understanding of the pro-angiogenic activity of human PSGs and strongly suggest conservation of this function among all PSG family members.

Omics Approaches to Study Formation and Function of Human Placental Syncytiotrophoblast

Proper development of the placenta is vital for pregnancy success. The placenta regulates exchange of nutrients and gases between maternal and fetal blood and produces hormones essential to maintain pregnancy. The placental cell lineage primarily responsible for performing these functions is a multinucleated entity called syncytiotrophoblast. Syncytiotrophoblast is continuously replenished throughout pregnancy by fusion of underlying progenitor cells called cytotrophoblasts. Dysregulated syncytiotrophoblast formation disrupts the integrity of the placental exchange surface, which can be detrimental to maternal and fetal health. Moreover, various factors produced by syncytiotrophoblast enter into maternal circulation, where they profoundly impact maternal physiology and are promising diagnostic indicators of pregnancy health. Despite the multifunctional importance of syncytiotrophoblast for pregnancy success, there is still much to learn about how its formation is regulated in normal and diseased states. ‘Omics’ approaches are gaining traction in many fields to provide a more holistic perspective of cell, tissue, and organ function. Herein, we review human syncytiotrophoblast development and current model systems used for its study, discuss how ‘omics’ strategies have been used to provide multidimensional insights into its formation and function, and highlight limitations of current platforms as well as consider future avenues for exploration.

Identifying biomarkers for predicting successful embryo implantation: applying single to multi-OMICs to improve reproductive outcomes

BACKGROUND

Successful embryo implantation is a complex process that requires the coordination of a series of events, involving both the embryo and the maternal endometrium. Key to this process is the intricate cascade of molecular mechanisms regulated by endocrine, paracrine and autocrine modulators of embryonic and maternal origin. Despite significant progress in ART, implantation failure still affects numerous infertile couples worldwide and fewer than 10% of embryos successfully implant. Improved selection of both the viable embryos and the optimal endometrial phenotype for transfer remains crucial to enhancing implantation chances. However, both classical morphological embryo selection and new strategies incorporated into clinical practice, such as embryonic genetic analysis, morphokinetics or ultrasound endometrial dating, remain insufficient to predict successful implantation. Additionally, no techniques are widely applied to analyse molecular signals involved in the embryo-uterine interaction. More reliable biological markers to predict embryo and uterine reproductive competence are needed to improve pregnancy outcomes. Recent years have seen a trend towards 'omics' methods, which enable the assessment of complete endometrial and embryonic molecular profiles during implantation. Omics have advanced our knowledge of the implantation process, identifying potential but rarely implemented biomarkers of successful implantation.

OBJECTIVE AND RATIONALE

Differences between the findings of published omics studies, and perhaps because embryonic and endometrial molecular signatures were often not investigated jointly, have prevented firm conclusions being reached. A timely review summarizing omics studies on the molecular determinants of human implantation in both the embryo and the endometrium will help facilitate integrative and reliable omics approaches to enhance ART outcomes.

SEARCH METHODS

In order to provide a comprehensive review of the literature published up to September 2019, Medline databases were searched using keywords pertaining to omics, including 'transcriptome', 'proteome', 'secretome', 'metabolome' and 'expression profiles', combined with terms related to implantation, such as 'endometrial receptivity', 'embryo viability' and 'embryo implantation'. No language restrictions were imposed. References from articles were also used for additional literature.

OUTCOMES

Here we provide a complete summary of the major achievements in human implantation research supplied by omics approaches, highlighting their potential to improve reproductive outcomes while fully elucidating the implantation mechanism. The review highlights the existence of discrepancies among the postulated biomarkers from studies on embryo viability or endometrial receptivity, even using the same omic analysis.

WIDER IMPLICATIONS

Despite the huge amount of biomarker information provided by omics, we still do not have enough evidence to link data from all omics with an implantation outcome. However, in the foreseeable future, application of minimally or non-invasive omics tools, together with a more integrative interpretation of uniformly collected data, will help to overcome the difficulties for clinical implementation of omics tools. Omics assays of the embryo and endometrium are being proposed or already being used as diagnostic tools for personalised single-embryo transfer in the most favourable endometrial environment, avoiding the risk of multiple pregnancies and ensuring better pregnancy rates.

Placenta-Specific Genes, Their Regulation During Villous Trophoblast Differentiation and Dysregulation in Preterm Preeclampsia

The human placenta maintains pregnancy and supports the developing fetus by providing nutrition, gas-waste exchange, hormonal regulation, and an immunological barrier from the maternal immune system. The villous syncytiotrophoblast carries most of these functions and provides the interface between the maternal and fetal circulatory systems. The syncytiotrophoblast is generated by the biochemical and morphological differentiation of underlying cytotrophoblast progenitor cells. The dysfunction of the villous trophoblast development is implicated in placenta-mediated pregnancy complications. Herein, we describe gene modules and clusters involved in the dynamic differentiation of villous cytotrophoblasts into the syncytiotrophoblast. During this process, the immune defense functions are first established, followed by structural and metabolic changes, and then by peptide hormone synthesis. We describe key transcription regulatory molecules that regulate gene modules involved in placental functions. Based on transcriptomic evidence, we infer how villous trophoblast differentiation and functions are dysregulated in preterm preeclampsia, a life-threatening placenta-mediated obstetrical syndrome for the mother and fetus. In the conclusion, we uncover the blueprint for villous trophoblast development and its impairment in preterm preeclampsia, which may aid in the future development of non-invasive biomarkers for placental functions and early identification of women at risk for preterm preeclampsia as well as other placenta-mediated pregnancy complications.

Human Trophoblast Differentiation Is Associated With Profound Gene Regulatory and Epigenetic Changes

Defective placental implantation and vascularization with accompanying hypoxia contribute to preeclampsia (PE), a leading cause of maternal and neonatal morbidity and mortality. Genetic and epigenetic mechanisms underlying differentiation of proliferative cytotrophoblasts (CytTs) to multinucleated syncytiotrophoblast (SynT) are incompletely defined. The SynT performs key functions in nutrient and gas exchange, hormone production, and protection of the fetus from rejection by the maternal immune system. In this study, we used chromatin immunoprecipitation sequencing of midgestation human trophoblasts before CytT and after SynT differentiation in primary culture to analyze changes in binding of RNA polymerase II (Pol II) and of active and repressive histone marks during SynT differentiation. Our findings reveal that increased Pol II binding to promoters of a subset of genes during trophoblast differentiation was closely correlated with active histone marks. This gene set was enriched in those controlling immune response and immune modulation, including interferon-induced tetratricopeptide repeat and placenta-specific glycoprotein gene family members. By contrast, genes downregulated during SynT differentiation included proinflammatory transcription factors ERG1, cFOS, and cJUN, as well as members of the NR4A orphan nuclear receptor subfamily, NUR77, NURR1, and NOR1. Downregulation of proinflammatory transcription factors upon SynT differentiation was associated with decreased promoter enrichment of endogenous H3K27Ac and H3K9Ac and enhanced binding of H3K9me3 and histone deacetylase 1. However, promoter enrichment of H3K27me3 was low in both CytT and SynT and was not altered with changes in gene expression. These findings provide important insight into mechanisms underlying human trophoblast differentiation and may identify therapeutic targets for placental disorders, such as PE.

Gene expression patterns associated with human placental trophoblast differentiation

Cell fusion is a hallmark of placental trophoblast cell differentiation and the mature syncytiotrophoblasts play essential roles for fetal-maternal exchange and production of pregnancy-related hormones. Using a well-established in vitro trophoblast differentiation model, we performed a microarray analysis on mRNA expression in trophoblast and syncytiotrophoblast cell cultures. Dramatic changes in gene expression patterns were detected during trophoblast differentiation. Real-time PCR analysis confirmed the reliability of the microarray data. As many as 3524 novel and known genes have been found to be up- or down-regulated for >2-fold. A number of cell cycle regulator including CDC6, CDC20, Cyclins B2, L1 and E2, were down-regulated in the syncytiotrophoblast, providing a mechanism for the loss of mitotic activity during trophoblast differentiation. Further characterization on the identified genes may lead to better understanding of placental patho-physiology in obstetric diseases such as preeclampsia.

Down-regulation of PDK4 is Critical for the Switch of Carbohydrate Catabolism during Syncytialization of Human Placental Trophoblasts

Pyruvate dehydrogenase kinase (PDK) is known as a gatekeeper directing the carbon flux into glycolysis via inhibition of the pyruvate dehydrogenase complex. During syncytialization of placental trophoblasts, both ATP production and oxygen consumption are increased to meet enhanced energetic demands by syntiotrophoblasts. We hypothesized that down-regulation of PDK expression may play a central role in the switch from glycolysis to oxidative phosphorylation (OXPHOS) during syncytialization. By using primary human trophoblasts, we demonstrated that PDK4 was the dominating PDK isoform in human cytotrophoblasts, and its abundance was substantially decreased upon syncytialization, which was accompanied by decreases in lactate production and increases in ATP production. Knock-down of PDK4 expression reduced lactate production and increased ATP production, while over-expression of PDK4 increased lactate production and decreased ATP production, indicating that down-regulation of PDK4 is key to the shift from glycolysis to OXPHOS during syncytialization. Moreover, human chorionic gonadotropin (hCG)/cAMP/PKA pathway was demonstrated to be involved in the down-regulation of PDK4 expression upon syncytialization. Taken together, our findings disclosed that down-regulation of PDK4 is critical for the metabolic shift from glycolysis to OXPHOS during syncytialization, which may be a prerequisite for the proper implementation of syncytiotrophoblast functions.

Placental transcriptomes in the common aneuploidies reveal critical regions on the trisomic chromosomes and genome-wide effects

OBJECTIVE

Chromosomal aberrations are frequently associated with birth defects and pregnancy losses. Trisomy 13, Trisomy 18 and Trisomy 21 are the most common, clinically relevant fetal aneusomies. This study used a transcriptomics approach to identify the molecular signatures at the maternal-fetal interface in each aneuploidy.

METHODS

We profiled placental gene expression (13-22 weeks) in T13 (n = 4), T18 (n = 4) and T21 (n = 8), and in euploid pregnancies (n = 4).

RESULTS

We found differentially expressed transcripts (≥2-fold) in T21 (n = 160), T18 (n = 80) and T13 (n = 125). The majority were upregulated and most of the misexpressed genes were not located on the relevant trisomic chromosome, suggesting genome-wide dysregulation. A smaller number of the differentially expressed transcripts were encoded on the trisomic chromosome, suggesting gene dosage. In T21, <10% of the genes were transcribed from the Down syndrome critical region (21q21-22), which contributes to the clinical phenotype. In T13, 15% of the upregulated genes were on the affected chromosome (13q11-14), and in T18, the percentage increased to 24% (18q11-22 region).

CONCLUSION

The trisomic placental (and possibly fetal) phenotypes are driven by the combined effects of genome-wide phenomena and increased gene dosage from the trisomic chromosome. © 2016 John Wiley & Sons, Ltd.

Transcriptomic signatures of villous cytotrophoblast and syncytiotrophoblast in term human placenta

During pregnancy, the placenta ensures multiple functions, which are directly involved in the initiation, fetal growth and outcome of gestation. The placental tissue involved in maternal-fetal exchanges and in synthesis of pregnancy hormones is the mononucleated villous cytotrophoblast (VCT) which aggregates and fuses to form and renew the syncytiotrophoblast (ST). Knowledge of the gene expression pattern specific to this endocrine and exchanges tissue of human placenta is of major importance to understand functions of this heterogeneous and complex tissue. Therefore, we undertook a global analysis of the gene expression profiles of primary cultured-VCT (n = 6) and in vitro-differentiated-ST (n = 5) in comparison with whole term placental tissue from which mononucleated VCT were isolated. A total of 880 differentially expressed genes (DEG) were observed between VCT/ST compared to whole placenta, and a total of 37 and 137 genes were significantly up and down-regulated, respectively, in VCT compared to ST. The 37 VCT-genes were involved in cellular processes (assembly, organization, and maintenance), whereas the 137 ST-genes were associated with lipid metabolism and cell morphology. In silico, all networks were linked to 3 transcriptional regulators (PPARγ, RARα and NR2F1) which are known to be essential for trophoblast differentiation. A subset of six DEG was validated by RT-qPCR and four by immunohistochemistry. To conclude, recognition of these pathways is fundamental to increase our understanding of the molecular basis of human trophoblast differentiation. The present study provides for the first time a gene expression signature of the VCT and ST compared to their originated term human placental tissue.

Scrutinising the regulators of syncytialization and their expression in pregnancy-related conditions

The placenta is important for the success of gestation and foetal development. In fact, this specialized pregnancy organ is essential for foetal nourishment, support, and protection. In the placenta, there are different cell populations, including four subtypes of trophoblasts. Cytotrophoblasts fuse and differentiate into the multinucleated syncytiotrophoblast (syncytialization). Syncytialization is a hallmark of placentation and is highly regulated by numerous molecules with distinct roles. Placentas from pregnancies complicated by preeclampsia, intrauterine growth restriction or trisomy 21 have been associated with a defective syncytialization and an altered expression of its modulators. This work proposes to review the molecules that promote or inhibit both fusion and biochemical differentiation of cytotrophoblasts. Moreover, it will also analyse the syncytialization modulators abnormally expressed in pathological placentas, highlighting the molecules that may contribute to the aetiology of these diseases.

ETS1 induces human trophoblast differentiation

A possible role for the transcription factor v-ets avian erythroblastosis virus E26 oncogene homolog 1 (ETS1) in human trophoblast cell differentiation was examined using a highly enriched fraction of human mononuclear cytotrophoblast cells (CTBs) that differentiate spontaneously in vitro to a multinucleated syncytiotrophoblast cell (STB) phenotype. ETS1 mRNA and protein levels were abundant in freshly isolated CTBs and decreased as the cells differentiated. Silencing of ETS1 expression in freshly prepared CTBs markedly attenuated syncytialization, as demonstrated by desmoplakin staining, and blocked the induction of syncytin, the transcription factor activator protein-2α, placental lactogen, and other STB-specific genes. Conversely, overexpression of ETS1 in primary trophoblast cells induced STB marker gene mRNAs and transactivated each of the gene proximal promoters. Taken together, these findings strongly suggest a critical role for ETS1 in the induction of human villus CTB differentiation. The effect of ETS1 on syncytialization likely results, at least in part, from inhibition of syncytin expression, whereas the induction of STB marker genes likely results in part from transactivation by activator protein-2α.

Activation of villous trophoblastic p38 and ERK1/2 signaling pathways in preterm preeclampsia and HELLP syndrome

Preterm preeclampsia is associated with the failure of trophoblast invasion, placental hypoxic/ischemic injury and the release of toxic substances, which promote the terminal pathway of preeclampsia. In term preeclampsia, factors yet unknown trigger the placenta to induce the terminal pathway. The contribution of the villous trophoblast to these pathologic events has not been fully elucidated. Here we aimed to study how stress and signaling pathways influence trophoblastic functions in various subforms of preeclampsia. Tissue microarrays (TMAs) were constructed from placentas obtained from pregnant women in the following groups: 1-2) preterm preeclampsia with (n = 8) or without (n = 7) HELLP syndrome; 3) late-onset preeclampsia (n = 8); 4-5) preterm (n = 5) and term (n = 9) controls. TMA slides were stained for phosphorylated Akt-1, ERK1/2, JNK, and p38 kinases, and trophoblastic immunostainings were semi-quantitatively evaluated. BeWo cells were kept in various stress conditions, and the expression of FLT1, GCM1, LEP, and PGF was profiled by qRT-PCR, while Akt-1, ERK1/2, JNK, and p38 kinase activities were measured with phospho-kinase immunoassays. We found that: 1) Placental LEP and FLT1 expression was up-regulated in preterm preeclampsia with or without HELLP syndrome compared to controls; 2) Mean pp38 immunoscore was higher in preterm preeclampsia, especially in cases with HELLP syndrome, than in controls. 3) Mean pERK1/2 immunoscore was higher in preterm preeclampsia with HELLP syndrome than in controls. 4) In BeWo cells, ischemia up-regulated LEP expression, and it increased JNK and decreased ERK1/2 activity. 5) Hypoxia up-regulated FLT1 and down-regulated PGF expression, and it increased ERK1/2, JNK and p38 activity. 6) IL-1β treatment down-regulated PGF expression, and it increased JNK and p38 activity. 7) The p38 signaling pathway had the most impact on LEP, FLT1 and PGF expression. In conclusion, hypoxic and ischemic stress, along with unknown factors, activates trophoblastic p38 signaling, which has a key role in villous trophoblastic functional changes in preterm preeclampsia. The activation of ERK1/2 signaling may induce additional trophoblastic functional changes in HELLP syndrome, while distinct mechanisms may promote late-onset preeclampsia.

Evolutionary origins of the placental expression of chromosome 19 cluster galectins and their complex dysregulation in preeclampsia

INTRODUCTION

The dysregulation of maternal-fetal immune tolerance is one of the proposed mechanisms leading to preeclampsia. Galectins are key regulator proteins of the immune response in vertebrates and maternal-fetal immune tolerance in eutherian mammals. Previously we found that three genes in a Chr19 cluster encoding for human placental galectin-13 (PP13), galectin-14 and galectin-16 emerged during primate evolution and may confer immune tolerance to the semi-allogeneic fetus.

MATERIALS AND METHODS

This study involved various methodologies for gene and protein expression profiling, genomic DNA methylation analyses, functional assays on differentiating trophoblasts including gene silencing, luciferase reporter and methylation assays. These methods were applied on placental specimens, umbilical cord blood cells, primary trophoblasts and BeWo cells. Genomic DNA sequences were analyzed for transposable elements, transcription factor binding sites and evolutionary conservation.

RESULTS AND DISCUSSION

The villous trophoblastic expression of Chr19 cluster galectin genes is developmentally regulated by DNA methylation and induced by key transcription factors of villous placental development during trophoblast fusion and differentiation. This latter mechanism arose via the co-option of binding sites for these transcription factors through promoter evolution and the insertion of an anthropoid-specific L1PREC2 transposable element into the 5' untranslated region of an ancestral gene followed by gene duplication events. Among placental Chr19 cluster galectin genes, the expression of LGALS13 and LGALS14 is down-regulated in preterm severe preeclampsia associated with SGA. We reveal that this phenomenon is partly originated from the dysregulated expression of key transcription factors controlling trophoblastic functions and galectin gene expression. In addition, the differential DNA methylation of these genes was also observed in preterm preeclampsia irrespective of SGA.

CONCLUSIONS

These findings reveal the evolutionary origins of the placental expression of Chr19 cluster galectins. The complex dysregulation of these genes in preeclampsia may alter immune tolerance mechanisms at the maternal-fetal interface.

Placental Protein 13 (PP13) - A Placental Immunoregulatory Galectin Protecting Pregnancy

Galectins are glycan-binding proteins that regulate innate and adaptive immune responses, and some confer maternal-fetal immune tolerance in eutherian mammals. A chromosome 19 cluster of galectins has emerged in anthropoid primates, species with deep placentation and long gestation. Three of the five human cluster galectins are solely expressed in the placenta, where they may confer additional immunoregulatory functions to enable deep placentation. One of these is galectin-13, also known as Placental Protein 13 (PP13). It has a "jelly-roll" fold, carbohydrate-recognition domain and sugar-binding preference resembling other mammalian galectins. PP13 is predominantly expressed by the syncytiotrophoblast and released from the placenta into the maternal circulation. Its ability to induce apoptosis of activated T cells in vitro, and to divert and kill T cells as well as macrophages in the maternal decidua in situ, suggests important immune functions. Indeed, mutations in the promoter and an exon of LGALS13 presumably leading to altered or non-functional protein expression are associated with a higher frequency of preeclampsia and other obstetrical syndromes, which involve immune dysregulation. Moreover, decreased placental expression of PP13 and its low concentrations in first trimester maternal sera are associated with elevated risk of preeclampsia. Indeed, PP13 turned to be a good early biomarker to assess maternal risk for the subsequent development of pregnancy complications caused by impaired placentation. Due to the ischemic placental stress in preterm preeclampsia, there is increased trophoblastic shedding of PP13 immunopositive microvesicles starting in the second trimester, which leads to high maternal blood PP13 concentrations. Our meta-analysis suggests that this phenomenon may enable the potential use of PP13 in directing patient management near to or at the time of delivery. Recent findings on the beneficial effects of PP13 on decreasing blood pressure due to vasodilatation in pregnant animals suggest its therapeutic potential in preeclampsia.

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.

Changes of placental syndecan-1 expression in preeclampsia and HELLP syndrome

Preeclampsia is characterized by maternal systemic anti-angiogenic and pro-inflammatory states. Syndecan-1 is a cell surface proteoglycan expressed by the syncytiotrophoblast, which plays an important role in angiogenesis and resolution of inflammation. Our aim was to examine placental syndecan-1 expression in preeclampsia with or without hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. Placentas were obtained from women in the following groups: (1) late-onset preeclampsia (n = 8); (2) early-onset preeclampsia without (n = 7) and (3) with HELLP syndrome (n = 8); (4) preterm controls (n = 5); and (5) term controls (n = 9). Tissue microarrays (TMAs) were constructed from paraffin-embedded placentas. TMA slides were immunostained for syndecan-1 and evaluated using microscopy, virtual microscopy, and semi-automated image analysis. Maternal sera from patients with preeclampsia (n = 49) and controls (n = 32) were immunoassayed for syndecan-1. BeWo cells were treated with Forskolin or Latrunculin B or kept in ischemic conditions. SDC1 expression and syndecan-1 production were investigated with qRT-PCR, confocal microscopy, and immunoassays. Syndecan-1 was localized to the syncytiotrophoblast apical membrane in normal placentas. Syndecan-1 immunoscores were higher in late-onset preeclampsia (p = 0.0001) and early-onset preeclampsia with or without HELLP syndrome (p = 0.02 for both) than in controls. Maternal serum syndecan-1 concentration was lower in preeclampsia (median, 673 ng/ml; interquartile range, 459-1,161 ng/ml) than in controls (1,158 ng/ml; 622-1,480 ng/ml). SDC1 expression and syndecan-1 immunostainings in BeWo cells and syndecan-1 concentrations in supernatants increased during cell differentiation. Disruption of the actin cytoskeleton with Latrunculin B decreased syndecan-1 release, while ischemic conditions increased it. Syncytiotrophoblastic syndecan-1 expression depends on the differentiation of villous trophoblasts, and trophoblastic syndecan-1 release is decreased in preeclampsia and HELLP syndrome. This phenomenon may be related to the disturbed syncytiotrophoblastic cortical actin cytoskeleton and associated with maternal anti-angiogenic and pro-inflammatory states in these syndromes.

iPcc: a novel feature extraction method for accurate disease class discovery and prediction

Gene expression profiling has gradually become a routine procedure for disease diagnosis and classification. In the past decade, many computational methods have been proposed, resulting in great improvements on various levels, including feature selection and algorithms for classification and clustering. In this study, we present iPcc, a novel method from the feature extraction perspective to further propel gene expression profiling technologies from bench to bedside. We define ‘correlation feature space’ for samples based on the gene expression profiles by iterative employment of Pearson’s correlation coefficient. Numerical experiments on both simulated and real gene expression data sets demonstrate that iPcc can greatly highlight the latent patterns underlying noisy gene expression data and thus greatly improve the robustness and accuracy of the algorithms currently available for disease diagnosis and classification based on gene expression profiles.

PSG gene expression is up-regulated by lysine acetylation involving histone and nonhistone proteins

Background

Lysine acetylation is an important post-translational modification that plays a central role in eukaryotic transcriptional activation by modifying chromatin and transcription-related factors. Human pregnancy-specific glycoproteins (PSG) are the major secreted placental proteins expressed by the syncytiotrophoblast at the end of pregnancy and represent early markers of cytotrophoblast differentiation. Low PSG levels are associated with complicated pregnancies, thus highlighting the importance of studying the mechanisms that control their expression. Despite several transcription factors having been implicated as key regulators of PSG gene family expression; the role of protein acetylation has not been explored.

Methodology/Principal Findings

Here, we explored the role of acetylation on PSG gene expression in the human placental-derived JEG-3 cell line. Pharmacological inhibition of histone deacetylases (HDACs) up-regulated PSG protein and mRNA expression levels, and augmented the amount of acetylated histone H3 associated with PSG 5′regulatory regions. Moreover, PSG5 promoter activation mediated by Sp1 and KLF6, via the core promoter element motif (CPE, −147/−140), was markedly enhanced in the presence of the HDAC inhibitor trichostatin A (TSA). This effect correlated with an increase in Sp1 acetylation and KLF6 nuclear localization as revealed by immunoprecipitation and subcellular fractionation assays. The co-activators PCAF, p300, and CBP enhanced Sp1-dependent PSG5 promoter activation through their histone acetylase (HAT) function. Instead, p300 and CBP acetyltransferase domain was dispensable for sustaining co-activation of PSG5 promoter by KLF6.

Conclusions/Significance

Results are consistent with a regulatory role of lysine acetylation on PSG expression through a relaxed chromatin state and an increase in the transcriptional activity of Sp1 and KLF6 following an augmented Sp1 acetylation and KLF6 nuclear localization.

Abnormal expression of transcription factor activator protein-2α in pathologic placentas

Recent studies from our laboratory have indicated that the transcription factor activator protein-2α plays a critical role in the differentiation of human villous cytotrophoblast cells to syncytiotrophoblast cells. However, little is known about the expression of activator protein-2α in placentas from pathologic pregnancies. This study compares the expression of activator protein-2α in placentas from high-risk pregnancies to gestational age-matched controls. Paracentral sections from grossly unremarkable areas of 10 placentas from each group of pregnancies complicated by mild preeclampsia, severe preeclampsia, diabetes mellitus, chronic hypertension, and fetal growth restriction and 10 control cases of placentas from normal pregnancies matched for gestational age were double immunostained for activator protein-2α and E-cadherin. The total numbers of cytotrophoblast cells and syncytiotrophoblast nuclei and the numbers of activator protein-2α-positive and activator protein-2α-negative nuclei in both of these cell types were counted by 2 pathologists blinded to disease status, in 10 representative×40 high-power fields for each placenta. Abnormal placental maturation in most of pathologic pregnancies was evidenced by a 1.5- to 1.7-fold lower expression ratio of syncytiotrophoblast cell to cytotrophoblast cell. Activator protein-2α in syncytiotrophoblast cells was lower in mild preeclampsia, diabetes mellitus, hypertension, and fetal growth restriction (P<.0001 in each instance) and was higher by 2-fold in severe preeclampsia, although this increase was not statistically significant (P=.3). Because activator protein-2α has been shown to be critical for villous cytotrophoblast cell differentiation, our findings suggest that abnormalities in the activator protein-2α cascade of transcription factors and/or signaling molecules may contribute to the pathogenesis of the abnormal maturation in placentas in certain types of high-risk pregnancies. The different pattern of activator protein-2α expression in mild and severe preeclampsia clearly suggests that these conditions may have 2 independent pathogenic mechanisms.

In-vitro effects of the antimicrobial peptide Ala8,13,18-magainin II amide on isolated human first trimester villous trophoblast cells

BACKGROUND

Research on antimicrobial cationic peptides (AMPs) has gained pace toward using their potential to replace conventional antibiotics. These peptides preferentially interact with negatively charged membrane lipids typically seen in bacteria and thereby lead to membrane perturbations and membrane dysfunction. However, one possible disadvantage of AMP drugs is their potential for toxicity, especially to those cells which display externalization of negatively charged moieties to the outer leaflet of the plasma membrane during the process of syncytialization. Human placental villous trophoblast is one such cell type. Indeed, intra-vaginal administration of an antimicrobial cationic peptide Ala8,13,18-magainin II amide (AMA) which is a synthetic analogue of magainin 2 derived from Xenopus frog has been observed to result in inhibition of pregnancy establishment in monkeys. However, only little is known about the cellular behavior of early placental cytotrophoblasts (CTB) in the presence of cationic antimicrobial peptides. It is believed that suitable cell culture approaches using AMA as a representative alpha-helical AMP may yield tangible knowledge in this regard.

METHODS

Immunocytochemical (ICC) analyses using confocal microscopy (n = 6 for each treatment sub-group) and Western blot (WB) method (n = 5 for each treatment sub-group) of CTB differentiation based on synthesis of beta-hCG and hPL, and apoptosis based on apoptosis-associated cytokeratin 18 neo-epitope (CK18f) were performed for CTB isolated from human first trimester placental villi and grown in serum-free primary culture for 24 h, 48 h and 96 h on rat-tail collagen with and without AMA (1000 ng/ml). Moreover, secretion of beta-hCG and hPL into conditioned media from isolated CTB grown in vitro for 24 h, 48 h and 96 h (n = 6/each sub-group) with and without AMA was examined using enzyme immunoassays. Furthermore, TUNEL assay, and cell viability based on LDH leakage into medium (n = 6/each sub-group) were assessed to examine the phenomenon of cell death with time and administration of AMA.

RESULTS

CTB in serum-free primary culture showed increased (P < 0.05) level of synthesis and secretion of beta-hCG and hPL with time, and higher (P < 0.05) level of cellular cytokeratin 18 neo-epitope and number of TUNEL-positive cells, and LDH activity in conditioned medium at 96 h of culture. Exposure of CTB to AMA resulted in lower (P < 0.05) level of synthesis and secretion of beta-hCG and hPL, as well as, an increase (P < 0.05) of cellular cytokeratin 18 neo-epitope and number of TUNEL-positive cells, and LDH activity in conditioned medium at 96 h as compared to the control treatment.

CONCLUSIONS

Administration of AMA resulted in attenuation of differentiation, enhancement in apoptosis and loss of viability in early placental villi trophoblast cells in primary culture. Thus, it appears that administration of alpha-helical AMP may adversely affect the process of placentation and pregnancy outcome.

Nuclear matrix association: switching to the invasive cytotrophoblast

Abnormal trophoblast invasion is associated with the most common and most severe complications of human pregnancy. The biology of invasion, as well as the etiology of abnormal invasion remains poorly understood. The aim of this study was to characterize the transcriptome of the HTR-8/SVneo human cytotrophoblast cell line which displays well characterized invasive and non-invasive behavior, and to correlate the activity of the transcriptome with nuclear matrix attachment and cell phenotype. Comparison of the invasive to non-invasive HTR transcriptomes was unremarkable. In contrast, comparison of the MARs on chromosomes 14-18 revealed an increased number of MARs associated with the invasive phenotype. These attachment areas were more likely to be associated with silent rather than actively transcribed genes. This study supports the view that nuclear matrix attachment may play an important role in cytotrophoblast invasion by ensuring specific silencing that facilitates invasion.

Involvement of transcription factor NR2F2 in human trophoblast differentiation

Background

During the in vitro differentiation of human villous cytotrophoblast (CTB) cells to a syncytiotrophoblast (STB) phenotype, mRNA levels for the nuclear hormone receptor NR2F2 (ARP-1, COUP-TFII) increase rapidly, reaching a peak at day 1 of differentiation that is 8.8-fold greater than that in undifferentiated CTB cells. To examine whether NR2F2 is involved in the regulation of villous CTB cell differentiation, studies were performed to determine whether NR2F2 regulates the expression of TFAP2A (AP-2α), a transcription factor that is critical for the terminal differentiation of these cells to a STB phenotype.

Methodology/Primary Findings

Overexpression of NR2F2 in primary cultures of human CTB cells and JEG-3 human choriocarcinoma cells induced dose-dependent increases in TFAP2A promoter activity. Conversely, siRNA mediated silencing of the NR2F2 gene in villous CTB undergoing spontaneous differentiation blocked the induction of the mRNAs for TFAP2A and several STB cell specific marker genes, including human placental lactogen (hPL), pregnancy specific glycoprotein 1 (PSG1) and corticotropin releasing hormone (CRH) by 51–59%. The induction of TFAP2A promoter activity by NR2F2 was potentiated by the nuclear hormone receptors retinoic acid receptor alpha (RARA) and retinoid X receptor alpha (RXRA).

Conclusions/Significance

Taken together, these results strongly suggest that NR2F2 is involved in villous CTB cell differentiation and that NR2F2 acts, at least in part, by directly activating TFAP2A gene expression and by potentiating the transactivation of TFAP2A by RARA and RXRA.

Expression and transcriptional regulation of individual pregnancy-specific glycoprotein genes in differentiating trophoblast cells

Human pregnancy-specific glycoproteins (PSGs), encoded by eleven highly conserved genes, are the major placental polypeptides. Low PSG levels in maternal circulation have been associated with complicated pregnancies. However, expression of each PSG gene and their regulation during cytotrophoblast cell differentiation remain poorly explored. Herein, we analyze the expression of five PSG genes and demonstrate that they are almost undetectable in undifferentiated trophoblast, but are all transcribed in differentiated cells. Among them, PSG1, PSG3 and PSG5 genes achieve high mRNA levels while PSG7 and PSG9 are poorly expressed. In addition, total PSG proteins and transcripts markedly increase during trophoblast differentiation, preceding morphological syncytialization and betahCG expression. The 5' regulatory region contributes to the transcriptional control of PSG gene induction in trophoblast cells undergoing differentiation. This responsive region in PSG3 maps within a 130 bp promoter sequence, which overlaps the transcription start site and requires a functional Retinoic Acid Responsive Element (RARE) and a GA-binding protein (GABP) consensus site for basal and differentiation-dependent promoter activity, respectively. Present findings provide novel data for understanding the control of PSG gene expression and demonstrate that their proteins and transcripts represent early markers of trophoblast differentiation.

Gene expression in the placenta: maternal stress and epigenetic responses

Successful placental development is crucial for optimal growth, development, maturation and survival of the embryo/fetus into adulthood. Numerous epidemiologic and experimental studies have demonstrated the profound influence of intrauterine environment on life, and the diseases to which one is subject as an adult. For the most part, these invidious influences, whether maternal hypoxia, protein or caloric deficiency or excess, and others, represent types of maternal stress. In the present review, we examine certain aspects of gene expression in the placenta as a consequence of maternal stressors. To examine these issues in a controlled manner, and in a species in which the genome has been sequenced, most of these reported studies have been performed in the mouse. Although each individual maternal stress is characterized by up- or down-regulation of specific genes in the placenta, functional analysis reveals some patterns of gene expression common to the several forms of stress. Of critical importance, these genes include those involved in DNA methylation and histone modification, cell cycle regulation, and related global pathways of great relevance to epigenesis and the developmental origins of adult health and disease.

Hyperglycemia perturbs biochemical networks in human trophoblast BeWo cells

Determining the effects of hyperglycemia on gene expression in placental trophoblast is important to gain a better understanding of how diabetes adversely affects pregnancy. In this study, we examined whether exposure to high glucose during forskolin-induced differentiation affects gene expression in differentiated trophoblasts. Human trophoblast BeWo cells were differentiated under low glucose (LG: 11 mM) or high glucose (HG: 25 mM) conditions. Gene expression was analyzed using a GeneChip system and the obtained data were analyzed using Ingenuity Pathways Analysis. In HG conditions, there were marked alterations in gene expression in differentiated BeWo cells compared with LG conditions. In particular, BeWo cells responded to HG with major changes in the expression levels of cell cycle- and metabolism-related genes. We selected the aromatase gene for further investigation of the molecular mechanisms. Mannitol or 3-O-methylglucose did not mimic the expression changes caused by HG, indicating that the effect of glucose was not due to a difference in osmotic pressure, and that glucose metabolism plays an essential role in inducing the HG effects. Cotreatment with N-acetylcysteine reduced the effect of HG on aromatase gene expression, suggesting that hyperglycemia may perturb biochemical networks because of the elevation of oxidative stress. Overall, our results will aid further understanding of the effect of diabetes on the regulation of trophoblast differentiation and function.

Gelatinase (MMP-2 and -9) expression profiles during gestation in the bovine endometrium

BACKGROUND

Various molecules participate in implantation and maintaining endometrial function during gestation. The remodeling of endometrial matrices is a necessary process in the coordination of gestational progress. Matrix-metalloproteinases (MMPs) like gelatinases (MMP-2 and -9) and collagenase (MMP-1) are considered to play important roles in this process. We examined MMP-2 and -9 expression using zymography, in situ hybridization, real-time PCR, and microarray analysis to clarify their roles in the bovine endometrium during gestation.

METHODS

Endometria, placentomes, and fetal membranes were collected from Japanese black cows that were killed on day 15 to 252 of gestation or during their estrous cycle. The gene expression of MMP-related molecules (mainly MMP-2 and -9) was examined using a custom-made microarray, real-time RT-PCR, and in-situ hybridization. Gelatinase activity was detected by zymography and film in situ zymography.

RESULTS

Both gelatinases were expressed in the endometrium and fetal tissues throughout gestation. MMP-2 gene expression declined with the progress of gestation, but its intensity was maintained at a high level during the peri-implantation period and increased in late gestation. The expression level of MMP-9 was stably maintained, but was relatively low compared to that of MMP-2. These gene expression patterns matched those detected by zymography for the proteins. Microarray analysis suggested that the functions of MMP-2 during implantation and the last part of gestation are closely related with those of other molecules such as tissue inhibitors of metalloproteinase (TIMP)-2, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) 1, membrane type 1 (MT1)-MMP, and extracellular matrix metalloproteinase inducer (EMMPRIN).

CONCLUSION

We detected MMP-2 and -9 gene expression in the bovine endometrium and placentome throughout gestation. These data suggest that MMP-2 is one of the main endometrial remodeling factors for implantation and pre-partum in cattle. In cows, as is the case in humans and rodents, gelatinases participate in endometrial remodeling, and their activities depend on the balance of activators and inhibitors; i.e., TIMP, MT-MMP, EMMPRIN, MMP-2, MMP-9, and so on.

Gene expression profiling reveals putative HOXA10 downstream targets in the periimplantation mouse uterus

HOXA10 encodes a transcription factor required for endometrial receptivity and embryo implantation. The objective of this study was to identify and to characterize those molecular markers regulated by HOXA10 expression. The authors have identified putative HOXA10 target genes identified by microarray analysis employing a murine model of transient HOXA10 expression during the anticipated implantation window. Microarray analysis identified 40 statistically significant genes regulated by HOXA10 overexpression of which 31 genes were downregulated greater than 2-fold over control and 9 genes were upregulated. Cellular ontogenies of differentially expressed genes include cell adhesion molecules, signal transduction factors, and metabolic regulators. Semiquantitative real-time reverse transcriptase polymerase chain reaction confirmed regulation of selected candidate genes. Examples included clusterin (Clu), phoshoglycerate 3-dehydrogenase (3-Pgdh), and tumor-associated calcium signal transducer 2 (Tacstd2). Elucidation of these pathways will allow further characterization of the molecular mechanisms governing endometrial development, which also may function to enhance uterine receptivity.

Gene expression profiling during Forskolin induced differentiation of BeWo cells by differential display RT-PCR

The differentiation of cytotrophoblasts into syncytiotrophoblasts in the placenta has been employed as a model to investigate stage specific expression as well as regulation of genes during this process. While the cytotrophoblasts are highly invasive and proliferative with relatively less capacity to synthesize pregnancy related proteins, the multinucleated syncytiotrophoblasts are non-proliferative and non-invasive. However, syncytiotrophoblasts are the site of synthesis of a variety of protein, peptide and steroid hormones as well as several growth factors. Both the freshly isolated cytotrophoblasts from human placenta as well as the BeWo cell, a choriocarcinoma cell line model which retain several characteristic of cytotrophoblasts has been employed by us to study regulation of differentiation. In the present study, we have employed the differential display RT-PCR analysis (DD-RT-PCR) to evaluate gene expression changes during Forskolin induced in vitro differentiation of BeWo cells. We have identified several genes which are differentially expressed during differentiation and the differential expression of 10 transcripts was confirmed by Northern blot analysis. Based on the identity of the transcripts an attempt has been made to relate the known function of the gene products, to changes observed during differentiation. Of the several transcripts, one of the transcripts, namely Secretory Leukocyte Protease Inhibitor (SLPI) which is known to have multiple functions was found to increase 15-fold in the syntiotrophoblast.

Epigenetic activation of the human growth hormone gene cluster during placental cytotrophoblast differentiation

The hGH cluster contains a single human pituitary growth hormone gene (hGH-N) and four placenta-specific paralogs. Activation of the cluster in both tissues depends on 5' remote regulatory elements. The pituitary-specific locus control elements DNase I-hypersensitive site I (HSI) and HSII, located 14.5 kb 5' of the cluster (position -14.5), establish a continuous domain of histone acetylation that extends to and activates hGH-N in the pituitary gland. In contrast, histone modifications in placental chromatin are restricted to the more 5'-remote HSV-HSIII region (kb -28 to -32) and to the placentally expressed genes in the cluster, with minimal modification between these two regions. These data predict distinct modes of hGH cluster gene activation in the pituitary and placenta. Here we used cell culture models to track structural changes at the hGH locus through placental-gene activation. The data revealed that this process was initiated in primary cytotrophoblasts by histone H3K4 di- and trimethylation and H4 acetylation restricted to HSV and to the individual placental-gene repeat (PGR) units within the cluster. Later stages of transcriptional induction were accompanied by enhancement and extension of these modifications and by robust H3 acetylation at HSV, at HSIII, and throughout the placental-gene regions. These data suggested that elements restricted to HSIII-HSV regions and each individual PGR might be sufficient for activation of the hCS genes. This model was tested by comparing hCS transgene expression in the placentas of mouse embryos carrying a full hGH cluster to that in placentas in which the HSIII-HSV region was directly linked to the individual hCS-A PGR unit. The findings indicate that the HSIII-HSV region and the PGR units, although targeted for initial chromatin structural modifications, are insufficient to activate gene expression and that this process is dependent on additional, as-yet-unidentified chromatin determinants.

RXRalpha regulates the pregnancy-specific glycoprotein 5 gene transcription through a functional retinoic acid responsive element

Human pregnancy-specific glycoproteins (PSG) are major placental polypeptides encoded by eleven highly conserved genes expressed by the syncytiotrophoblast. The minimal promoter region of all PSG genes contains a putative Retinoic Acid Responsive Element (RARE) though the ability of retinoids to regulate PSG gene expression has not been established. Retinoid signaling pathway plays a key role for overall placenta biology and is essential for trophoblast differentiation. In this work, we investigated the participation of the RARE motif in the regulation of PSG5 gene transcription by retinoic acid and its receptors. The minimal promoter region of PSG5 gene was activated by RXRalpha but not by RARalpha, in a ligand-dependent manner. The RARE sequence of PSG5 gene promoter was recognized by endogenous RXRalpha present in placental nuclear extracts as well as by RXRalpha either over expressed in cultured non-placental cells or in vitro translated. Mutations at specific nucleotides within the RARE motif abrogated both RXRalpha DNA binding and transcriptional activation of PSG5 promoter mediated by RXRalpha. Moreover, endogenous PSG expression was significantly induced in trophoblast-derived Jeg-3 cells upon 9-cis retinoic acid treatment. Interestingly, the induction level was higher following methotrexate-induced differentiation of Jeg-3 cells to syncytiotrophoblast-like structures. Altogether, these data provide the first evidences demonstrating that transcriptional activity of PSG5 gene is responsive to an external signal involving the retinoids-RXRalpha axis through a conserved RARE motif shared by all PSG gene family members.

Cytomegalovirus infection of human syncytiotrophoblast cells strongly interferes with expression of genes involved in placental differentiation and tissue integrity

The principle route of acquisition of cytomegalovirus (CMV) for the fetus is believed to be via the placenta. We subjected purified cytotrophoblast cells obtained from full-term placentas to CMV infection and examined placental gene expression using microarray analyses. Cytotrophoblast cells purified from term placentas differentiated in vitro into a multinucleated syncytium that could be productively infected with CMV, with peak virus titers of approximately 10 plaque-forming units (PFU)/mL identified in supernatants at late time points postinoculation. Infected syncytiotrophoblast cells expressed CMV-specific transcripts and proteins, as demonstrated by Northern blot and immunofluorescence assays. Microarray analyses revealed that CMV infection strongly and reproducibly altered trophoblast gene expression, elevating expression of mitotic cell cycle genes, and repressing expression of genes associated with trophoblast differentiation, particularly those associated with formation and stabilization of the extracellular matrix. We conclude that purified, differentiated syncytiotrophoblasts are permissive for CMV replication. Infection of these cells induces significant perturbations in trophoblast transcription. An improved understanding of the molecular events that occur during CMV infection of trophoblasts could provide insights into interventions that might prevent or minimize congenital transmission.

Analysis of uteroplacental-specific molecules and their functions during implantation and placentation in the bovine

In cattle, the mechanisms underlying implantation and placental development are still unclear. Synepitheliochorial placentation in cattle is noninvasive, and thus generates limited interest in terms of degradation and remodeling of endometrial tissues. The overall purpose of this study was three-fold: (1) to examine the gene circuitry around the implantation window, (2) to understand development of the placenta during the peri-implantation period by using a uteroplacental cDNA microarray, and (3) to study the roles of molecules involved in endometrial remodeling. Bovine trophoblastic binucleate cell-specific molecules, such as pregnancy-associated glycoproteins (PAGs), placental lactogen (PL), and prolactin-related proteins (PRPs), were markedly expressed in binucleate cells (BNCs) around implantation. The expression of PRP-1 was specific to the caruncular (CAR) area of the gravid uterine horn. Gelatinases (MMP-2 and -9) in association with heparanase may be central to endometrial remodeling. In situ hybridization analyses of PAGs, PRPs, PL, and heparanase suggested that BNCs expressed these molecules simultaneously. Future studies will further investigate the specific roles of these molecules in placentogenesis. The uteroplacental cDNA microarray presented cascades of molecular signatures not only for the endometrium but also for the intricate dialogue at the level of the feto-maternal interface in cattle. Placentome morphogenesis potentially parallels the dynamic multigenic circuitry and regulates the cell cycle in the endometrium. The roles of BNCs and their secreted molecules remain an enigma, particularly with regard to the adhesion process and endometrial remodeling, which is the focus of this study.

Gene expression profiling of the human maternal-fetal interface reveals dramatic changes between midgestation and term

Human placentation entails the remarkable integration of fetal and maternal cells into a single functional unit. In the basal plate region (the maternal-fetal interface) of the placenta, fetal cytotrophoblasts from the placenta invade the uterus and remodel the resident vasculature and avoid maternal immune rejection. Knowing the molecular bases for these unique cell-cell interactions is important for understanding how this specialized region functions during normal pregnancy with implications for tumor biology and transplantation immunology. Therefore, we undertook a global analysis of the gene expression profiles at the maternal-fetal interface. Basal plate biopsy specimens were obtained from 36 placentas (14-40 wk) at the conclusion of normal pregnancies. RNA was isolated, processed, and hybridized to HG-U133A&B Affymetrix GeneChips. Surprisingly, there was little change in gene expression during the 14- to 24-wk interval. In contrast, 418 genes were differentially expressed at term (37-40 wk) as compared with midgestation (14-24 wk). Subsequent analyses using quantitative PCR and immunolocalization approaches validated a portion of these results. Many of the differentially expressed genes are known in other contexts to be involved in differentiation, motility, transcription, immunity, angiogenesis, extracellular matrix dissolution, or lipid metabolism. One sixth were nonannotated or encoded hypothetical proteins. Modeling based on structural homology revealed potential functions for 31 of these proteins. These data provide a reference set for understanding the molecular components of the dialogue taking place between maternal and fetal cells in the basal plate as well as for future comparisons of alterations in this region that occur in obstetric complications.

Carcinoembryonic Antigen and Related Molecules in Normal and Transformed Trophoblast

Carcinoembryonic antigen (CEA, CD66e) and CEA-related cell adhesion molecules (CEACAMs) are important mediators in remodeling of diverse human tissues, and modulators of cell proliferation and differentiation. Expression by normal and transformed trophoblast of gestational trophoblastic diseases (GTDs), isolated cytotrophoblast and choriocarcinoma cell lines is presented here. Immunocyto/histochemistry of normal placenta (n=9), invasive mole (n=8), choriocarcinoma (n=7), a placental site trophoblastic tumor, cytotrophoblast in primary culture and JAr and JEG-3 cells was performed using polyclonal anti-CEA and specific monoclonal anti-CEA antibodies. Data were analyzed and scored using Mann-Whitney Test. CEA and CEA-related molecules were identified by Western blot and immunoaffinity chromatography in JAr and JEG-3 cells and extracts of 1st and 3rd trimester of pregnancy tissue and cytotrophoblast cell lysates. CEA is expressed throughout pregnancy, in first trimester predominantly in syncytiotrophoblast, but also in villous cytotrophoblast and extravillous trophoblast. Data presented here demonstrate that CEA is significantly increased in transformed trophoblast of GTDs (p<0.05). Both cytotrophoblast in primary culture and choriocarcinoma cell lines express CEA, with staining of granular deposits in JAr and cell membrane in JEG-3. The results suggest that CEA (CD66e) and other CEA-related protein(s) could be involved in trophoblast differentiation.

Gene expression and maintenance of pregnancy in bovine: roles of trophoblastic binucleate cell-specific molecules

Cell to cell interaction plays a pivotal role in the regulation of placentogenesis and exchange of stage-specific developmental signals between the fetal and maternal units. Specifically, these interactions are paramount for programmed fetal growth, maternal adaptation to pregnancy and coordination of parturition. However, little is known about the precise regulation of placentation and maintenance of gestation in cattle. Therefore, the aim of the present study was to decipher the complex networks of cell communication to gain an insight into the multifaceted developmental process and understand the profound consequences of flawed communication. In the ruminant, the binucleate cell plays a central role in forming the structures and secretions at the fetomaternal interface that are crucial in establishing and maintaining pregnancy. Herein, we summarise differences in the abundance of specific RNA transcripts in the bovine cotyledon and caruncle using global gene expression profiling and further investigate the relationship of mRNA abundance for selected pregnancy-specific genes of interest (identified from microarray studies) that are localised exclusively to the binucleate cell, such as placental lactogen, prolactin-related proteins and pregnancy-associated glycoproteins. The results suggest that a well-orchestrated transcriptional command from binucleate cells is pivotal to the establishment and progression of pregnancy in cattle.

Biomarkers of ovulation, endometrial receptivity, fertilisation, implantation and early pregnancy progression

Increasing interest in early preconception and periconception exposures and human developmental outcomes has led to studies that monitor subjects from before conception to gestation, birth and childhood. Monitoring ovulation, endometrial receptivity, fertilisation, implantation and gestation requires the non-invasive collection of biological information and samples, and the measurement of biochemical and biological markers (biomarkers) that are associated with the aforementioned physiological events. This paper describes some of the key features of biomarkers needed for epidemiological studies, identifies some existing and potential biomarkers and available measurement devices, and suggests some directions for identification and development of new biomarkers that might be employed in longitudinal studies involving the analysis of female reproductive function and of embryonic development.

Microarray analysis of BeWo and JEG3 trophoblast cell lines: identification of differentially expressed transcripts

Trophoblast cell lines are important research tools used as a surrogate for primary trophoblast cells in the study of placental function. Because the cellular origins of transformed trophoblasts are likely to be diverse, it would be of value to understand the unique and shared phenotypes of the cells on a global scale. We have compared two widely used cell lines, BeWo and JEG3, by microarray analysis in order to identify differentially expressed genes. Results indicated that approximately 2700 genes were differentially expressed between the cell lines, with principal differences observed in the biological processes of response to stress, cell adhesion, signal transduction, and protein and nucleobase metabolisms. These data suggest that BeWo and JEG3 cell lines, and perhaps other trophoblast cell lines, are sufficiently dissimilar from each other such that they will be differentially suited for specific experimental paradigms.

Gene expression patterns in the developing murine placenta

OBJECTIVE

Successful placental development is crucial for optimal growth, maturation, and survival of the embryo/fetus. To examine genetic aspects of placental development, we investigated gene expression patterns in the murine placenta at embryonic day 10.5 (E10.5), E12.5, E15.5, and E17.5.

METHODS

By use of the Affymetrix MU74A array (Affymetrix, Santa Clara, CA), we measured expression levels for 12,473 probe sets. Using pairwise analysis we selected 622 probe sets, corresponding to 599 genes, that were up- or down-regulated by more than fourfold between time points E10.5 and E12.5, E12.5 and E15.5, E15.5 and E17.5. We analyzed and functionally annotated those genes regulated during development.

RESULTS

In comparing E10.5 to E12.5 we found that angiogenesis and fatty acid metabolism and transport related genes were up-regulated at E10.5, while genes involved in hormonal control and ribosomal proteins were up-regulated at E12.5. When comparing E12.5 to E15.5 we noted that genes involved in the cell cycle and RNA metabolism were strongly up-regulated at E12.5, while genes involved in cellular transport were up-regulated at E15.5. Finally, when comparing E15.5 to E17.5, we found genes related to cell cycle control, genes expressed in the nucleus and involved in RNA metabolism were up-regulated at E17.5.

CONCLUSION

Microarray analysis has allowed us to describe gene expression patterns and profiles in the developing mouse placenta. Further analysis has demonstrated that several functional classes are up- and down-regulated at specific time points in placental development. These changes may have significant implications for placental development in the human.

The use of needle biopsy for assessment of placental gene expression

OBJECTIVE

The purpose of this study was to test the hypothesis that placental samples that are obtained by needle aspiration ex vivo are useful for the determination of villus gene expression.

STUDY DESIGN

Placental biopsy was performed with a spinal needle after uncomplicated deliveries. Villi were inspected microscopically, and RNA was extracted and analyzed with capillary electrophoresis. Gene expression was determined with quantitative polymerase chain reaction.

RESULTS

We obtained more placental villous fragments per aspiration using a 20-gauge needle (5.2 +/- 1.8 fragments) than with a 22-gauge needle (3.3 +/- 1.6 fragments; P < .01). RNA quality was adequate, based on the 28S and 18S recombinant RNA bands, with a mean 260/280 ratio of 1.88. The amount of extracted RNA correlated with the number of villous fragments per aspirate. Importantly, the expression of NDRG1 and hPL, both markedly altered in hypoxia, was consistent between villi that were obtained by either needle or standard biopsy.

CONCLUSION

Placental samples that are obtained by ex vivo needle aspiration are useful for the extraction of RNA and for the determination of villous gene expression.

Preeclampsia: increased expression of soluble ADAM 12

Preeclampsia is a multisystemic pregnancy-associated disease affecting about 3-7% of pregnancies worldwide and is still a principal cause of fetal and maternal morbidity and mortality. To identify potential markers, we have compared gene expression profiles from control and preeclamptic placental tissues taken at various age-matched gestational stages using complementary DNA microarray analysis. Besides previously identified preeclampsia-associated genes, novel differentially expressed transcripts were found. The soluble form of the disintegrin metalloprotease ADAM 12 (a disintegrin and metalloproteinase 12; meltrin-alpha) represented the most upregulated transcript. This was confirmed by in situ hybridization of sections of preeclamptic placentas and by serum protein analysis of preeclamptic pregnant women. Thus, ADAM 12 could serve as an early biomarker for preeclampsia that may be of predictive and/or functional significance.

The correlation between sampling site and gene expression in the term human placenta

Using oligonucleotide microarrays we recently identified a set of transcripts that were up-regulated in hypoxic human trophoblasts. To test the hypothesis that expression of hypoxia-related placental transcripts depends on sampling site we analyzed nine different sites from term human placentas (n=6), obtained after uncomplicated pregnancies. These sites spanned the placental center to the lateral border and the basal to the chorionic plate. Relative gene expression at each site, determined using quantitative PCR, was correlated with villous histology. The expression of vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF), the cytoskeleton proteins lamininA3 and alpha-tubulin, and the signal transduction protein Rad was enhanced in the subchorionic lateral border compared to medial basal site (1.6-2.9 fold, p<0.05). In contrast, the expression of NDRG1, adipophilin and human placental lactogen was unchanged. Enhanced villous maturation, syncytial knots and fibrin deposits were more frequent in the subchorionic placental lateral border, and correlated with up-regulation of hypoxia-related transcripts (p<0.05). The association between sample site and expression level was not observed in placentas with marginal cord insertion. The expression of hypoxia-related genes in the term human placenta is dependent on sampling site within the placental disk, likely reflecting local differences in villous perfusion.

Spontaneous differentiation of mouse embryonic stem cells in vitro: characterization by global gene expression profiles

We characterized the temporal gene expression changes during four weeks of spontaneous differentiation of mouse ES cells in a monolayer culture in order to obtain better insight into the differentiation process. The overall gene expression pattern was changed dramatically during the first two weeks of spontaneous differentiation, but stabilized after the second week. Most of the genes regulated within the first two weeks of spontaneous differentiation were genes related to development including morphogenesis, cell differentiation, embryonic development, pattern specification, mesoderm development, post-embryonic development, and blastocyst development. While most of the ectoderm lineage related genes were down-regulated, genes related to the mesoderm or endoderm lineage were up-regulated through the first week and second week, respectively. This study revealed that the development of ectoderm lineage is a recessive process during the spontaneous differentiation of mouse ES cells in monolayer culture. Our time-course characterization might provide a useful time line for directed differentiation of mouse ES cells.

Identification of Differentially Regulated Genes During Elongation and Early Implantation in the Ovine Trophoblast Using Complementary DNA Array Screening1

Following hatching, pre-elongated conceptuses undergo elongation by intense proliferation, until implantation. We investigated the changes in gene expression associated with these physiological events using human cDNA arrays containing 2370 known genes. Comparison of pre-elongated, elongated, and implanting trophoblasts allowed the determination of 313 expressed genes, 63 of which were differentially regulated. These were classified into four functional families. Pre-elongated trophoblasts were characterized by preferential expression of genes involved in protein trafficking, whereas only latter developmental stages expressed cell signaling genes and receptors. Among the 63 developmentally regulated genes, four exhibited the highest levels of expression (TMSB10, CTNNA1, NMP1, and CX3CL1). Each of these also represents a functional family and display a specific expression pattern. One of them, CX3CL1 (CX3C chemokine, also known as fractalkine), is a chemokine that seems to have potential importance in trophoblast development, and which deserves further clarification of its role in implantation.

The changes of gene expression profiles in hydatidiform mole and choriocarcinoma with hyperplasia of trophoblasts

The purpose of this study is to investigate changes of gene expression profiles in hydatidiform moles (HM) and choriocarcinoma and to explore causes of trophoblastic hyperplasia. Using cDNA microarray, 4,096 genes were analyzed in two pairs of the tissues of HM versus normal villi and in two pairs of normal primary culture trophoblasts versus JAR cell line of choriocarcinoma. The expressions of two genes in normal villi and HM, as well as in JAR and JEG-3, were examined with the help of immunohistochemistry, immunoblot, and reverse transcriptase-polymerase chain reaction in order to confirm the findings of cDNA microarray. Twenty-four genes were upregulated and 65 genes were downregulated in all HM. Four hundred thirty-three genes were upregulated and 380 genes were downregulated in JAR. Forty-six genes were upregulated in both HM and choriocarcinoma, whereas 13 genes were downregulated. Genes associated with the inhibition of cell proliferation were significantly downregulated, whereas genes associated with cell proliferation, malignant transformation, metastasis, and drug resistance were upregulated. Thymidine kinase-1 (TK-1) and small subunit ribonucleotide reductase (RRM-2) were overexpressed in HM, JAR, and JEG-3. The expressions of TK-1 and RRM-2 in moles were positively correlated with proliferative index of trophoblasts. Our results suggest that altered expression of genes exist in HM and choriocarcinoma. Trophoblastic hyperplasia may be involved in the overexpression of DNA synthetic enzymes.

An analysis using DNA microarray of the time course of gene expression during syncytialization of a human placental cell line (BeWo)

Placental trophoblast syncytialization is a unique biological process. We have studied the time course of this process using DNA microarray in a cell model of syncytialization (the cytotrophoblast cell line BeWo following increased intracellular cAMP by forskolin). Total RNA was extracted from BeWo cells and labelled-cRNA target was then hybridized to a specific oligonucleotide probe set containing probes to over 12?000 human transcripts. Detectable levels of signal were found on average for 44 per cent of the total number of genes assayed. The correlation coefficient for the level of expression of independent replicates was #10878;0.99. The mRNA expression profile of specific genes analysed by microarray correlated quantitatively well with that analysed by reverse transcription-polymerase chain reaction and with protein secretion. In the absence of forskolin there are relatively few changes in gene expression (reaching a threshold of two fold); in the presence of forskolin there are a substantial number of changes. By clustering the patterns of altered gene expression at least ten groups could be extracted. Seven of these clusters involved increased gene expression and three decreased expression. Each cluster has been categorized by gene ontology (confining the analysis to genes with 'known' function). Among the genes with increased expression following forskolin treatment were many required for cellular communication (such as placental specific peptide hormones) and metabolism (such as cholesterol side chain cleavage enzyme). Several genes known to be involved in cell adhesion and fusion have markedly changed expression levels very early following forskolin exposure, thus preceding morphological fusion of BeWo cells. Further analysis of this data and expression profiling in general will be able to contribute to understanding the functional basis for the formation of the placental syncytiotrophoblast.

cDNA microarray analysis of bovine embryo gene expression profiles during the pre-implantation period

Background

After fertilization, embryo development involves differentiation, as well as development of the fetal body and extra-embryonic tissues until the moment of implantation. During this period various cellular and molecular changes take place with a genetic origin, e.g. the elongation of embryonic tissues, cell-cell contact between the mother and the embryo and placentation. To identify genetic profiles and search for new candidate molecules involved during this period, embryonic gene expression was analyzed with a custom designed utero-placental complementary DNA (cDNA) microarray.

Methods

Bovine embryos on days 7, 14 and 21, extra-embryonic membranes on day 28 and fetuses on days 28 were collected to represent early embryo, elongating embryo, pre-implantation embryo, post-implantation extra-embryonic membrane and fetus, respectively. Gene expression at these different time points was analyzed using our cDNA microarray. Two clustering algorithms such as k-means and hierarchical clustering methods identified the expression patterns of differentially expressed genes across pre-implantation period. Novel candidate genes were confirmed by real-time RT-PCR.

Results

In total, 1,773 individual genes were analyzed by complete k-means clustering. Comparison of day 7 and day 14 revealed most genes increased during this period, and a small number of genes exhibiting altered expression decreased as gestation progressed. Clustering analysis demonstrated that trophoblast-cell-specific molecules such as placental lactogens (PLs), prolactin-related proteins (PRPs), interferon-tau, and adhesion molecules apparently all play pivotal roles in the preparation needed for implantation, since their expression was remarkably enhanced during the pre-implantation period. The hierarchical clustering analysis and RT-PCR data revealed new functional roles for certain known genes (dickkopf-1, NPM, etc) as well as novel candidate genes (AW464053, AW465434, AW462349, AW485575) related to already established trophoblast-specific genes such as PLs and PRPs.

Conclusions

A large number of genes in extra-embryonic membrane increased up to implantation and these profiles provide information fundamental to an understanding of extra-embryonic membrane differentiation and development. Genes in significant expression suggest novel molecules in trophoblast differentiation.