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Altered Gene Expression Profile of Microvascular Endothelium in Placentas from IUGR/Preeclamptic Pregnancies

ABSTRACT: The placental microvasculature of the human fetus is essential for the efficient transfer of gases, nutrients and waste between the mother and fetus. Microvascular hypoplasia of the terminal villi is associated with the placental pathology observed in cases of severe Intra Uterine Growth Restriction (IUGR). We used novel methods to isolate a pure population of placental microvascular endothelial cells from control preterm placentas (n=3) and placenta complicated by severe IUGR (n=6) with superimposed preeclampsia (n=5). Distal placental villous tissue was collected to enrich for terminal villi. Tissue was minced, digested and placental microvascular endothelial cells (PlMEC) were positively selected using tocosylated magnetic Dynabeads labeled with Human Endothelial Antigen lectin. The purity of the PlMEC (95%) was assessed by CD31 immunocytochemistry. RNA was extracted from the PlMEC samples and also from 3 term placenta and subjected to Affymetrix microarray analysis (U133Plus2 array chips). Data from the 3 term placentas and 3 preterm PlMEC arrays was used to generate an endothelial cell specific gene profile. This profile was used to identify the endothelial genes differentially regulated in all 6 IUGR cases. BTNL9 and NTRK2 transcripts were upregulated and SAA1, GNAS and SLAMF1 transcripts were downregulated as relative to the preterm controls. These changes were validated by Real time PCR in the PlMEC samples. This novel study is the first to identify endothelial candidate genes that may play a role in the villous hypoplasia of severe IUGR. This work advances our understanding of the molecular defects in placental microvascular endothelial cells in normal and pathologic pregnancies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE25861 | GEO | 2012/04/01

SECONDARY ACCESSION(S): PRJNA135785

REPOSITORIES: GEO

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Project description:Intrauterine growth restriction (IUGR) affects up to 10% of pregnancies and often results in short- and long- term sequelae for offspring, including risk for adult cardiovascular disease (CVD). The mechanisms underlying IUGR are poorly understood, though poor blood flow and oxygen/nutrient provision to the IUGR fetus are thought to be the common endpoints of disease. Though several animal models of IUGR exist, few demonstrate later phenotypes of CVD despite a large body of evidence in humans linking IUGR and adult CVD onset. We thus hypothesized that in murine pregnancy, maternal late gestational hypoxia (LG-H) exposure resulting in IUGR would result in (1) adult phenotypes of CVD in hypoxia-exposed offspring, and (2) the placental transcriptome will demonstrate alterations that can be linked to risk of later disease. After subjecting pregnant mice to hypoxia (10.5% oxygen) from gestational day (GD) 14.5 to 18.5, we collected placentas at GD19. We examined RNA isolated from these placentas to perform RNA sequencing and analysis. Functional gene and cluster-based analysis suggest multiple changes in structural and functional genes important for placental health, with the top dysregulation involving vascular and metabolic pathways. Concordantly, a ~ 10% decrease in birthweights and ~30% decrease in litter size after LG-H (p<0.05) was observed, suggesting an environment of placental insufficiency. We also found that offspring exposed in-utero to LG-H exhibit CVD at 4 months of age, with males being worse than females, supporting developmental programming. Specifically, males exhibit increased body weight and an enlarged heart size, whereas both males and females develop hypertension, elevated abdominal fat, elevated leptin and elevated total cholesterol levels with aging. In summary, LG-H exposure in the pregnant mouse mimics human placental insufficiency related IUGR. The placentas of these exposed fetuses demonstrate a transcriptional response to the stressor of gestational hypoxia and predicts cardiovascular and metabolic effects that culminate into hypertension and adiposity with dyslipidemia.

Project description:The maternal and paternal copies of the genome are both required for mammalian development and this is primarily due to imprinted genes, those that are mono-allelically expressed based on parent-of-origin. Typically, this pattern of expression is regulated by differentially methylated regions (DMRs) that are established in the germline and maintained after fertilisation. There are a large number of germline DMRs that have not yet been associated with imprinting and their function in development is unknown. In this study, we developed a genome-wide approach to identify novel imprinted DMRs, specifically in the human placenta, and investigated the dynamics of imprinted DMRs during development in somatic and extra-embryonic tissues. DNA methylation was evaluated using the Illumina HumanMethylation450 array in 116 human tissue samples, publically available reduced representation bisulfite sequencing in the human embryo and germ cells, and targeted bisulfite sequencing in term placentas. 43 known and 101 novel imprinted DMRs were identified in the human placenta, by comparing methylation between diandric and digynic triploids and female and male gametes. 72 novel DMRs showed a pattern consistent with placental-specific imprinting and this mono-allelic methylation was entirely maternal in origin. Strikingly, these DMRs exhibited polymorphic imprinted methylation specifically in placenta. These data suggest that imprinting in human development is far more extensive and dynamic than previously reported and that the placenta preferentially maintains maternal germline-derived DNA methylation For the identification of imprinted DMRs in the placenta, chorionic villous samples from 5 diandric and 5 digynic triploids pregnancies were assayed, along with a pooled sample of complete hydatiform moles (CHM). Placental chorionic villous samples (n=63) included 29 control pregnancies delivered at term, while the remaining 34 were delivered preterm or miscarried, or had abnormal MSS results, IUGR or LOPET. The preterm births were associated with one or more of: preterm labour, premature rupture of membranes (PROM), chorioamnionitis, placental abruption, and incompetent cervix. All samples were determined to be chromosomally normal using standard karyotyping or comparative genome hybridization, as previously described (Robinson et al. 2010). Two to four independent sites were taken from each placenta and after DNA extraction from chorionic villous, the DNA was pooled before being utilized in this study. Thirty-three fetal tissues, including brain (n=8), spinal cord (n=7), muscle (n=9), and kidney (n=9) were collected from second trimester foetuses, as previously described (Price et al. 2012). Adult female whole blood samples (n=10) were collected from control women. Extra-embryonic cell types (n=19), including cord blood (embryonic), cord, amniotic membrane, chorionic membrane, 1st, 2nd and 3rd trimester trophoblast and mesenchyme, and decidua (maternal), were isolated from control placental samples.

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Altered Gene Expression Profile of Microvascular Endothelium in Placentas from IUGR/Preeclamptic Pregnancies

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