Gene expression in chorionic villous samples at 11 weeks of gestation in women who develop preeclampsia later in pregnancy: implications for screening

Human monocyte transcriptional profiling identifies IL-18 receptor accessory protein and lactoferrin as novel immune targets in hypertension

BACKGROUND AND PURPOSE

Monocytes play a critical role in hypertension. The purpose of our study was to use an unbiased approach to determine whether hypertensive individuals on conventional therapy exhibit an altered monocyte gene expression profile and to perform validation studies of selected genes to identify novel therapeutic targets for hypertension.

EXPERIMENTAL APPROACH

Next generation RNA sequencing identified differentially expressed genes in a small discovery cohort of normotensive and hypertensive individuals. Several of these genes were further investigated for association with hypertension in multiple validation cohorts using qRT-PCR, regression analysis, phenome-wide association study and case-control analysis of a missense polymorphism.

KEY RESULTS

We identified 60 genes that were significantly differentially expressed in hypertensive monocytes, many of which are related to IL-1β. Uni- and multivariate regression analyses of the expression of these genes with mean arterial pressure (MAP) revealed four genes that significantly correlated with MAP in normotensive and/or hypertensive individuals. Of these, lactoferrin (LTF), peptidoglycan recognition protein 1 and IL-18 receptor accessory protein (IL18RAP) remained significantly elevated in peripheral monocytes of hypertensive individuals in a separate validation cohort. Interestingly, IL18RAP expression associated with MAP in a cohort of African Americans. Furthermore, homozygosity for a missense single nucleotide polymorphism in LTF that decreases antimicrobial function and increases protein levels (rs1126478) was over-represented in patients with hypertension relative to controls (odds ratio 1.16).

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that monocytes exhibit enhanced pro-inflammatory gene expression in hypertensive individuals and identify IL18RAP and LTF as potential novel mediators of human hypertension.

LINKED ARTICLES

This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Peptidome analysis of amniotic fluid from pregnancies with preeclampsia

Preeclampsia (PE), a life-threatening, complicated pregnancy-associated disease, has recently become a research focus in obstetrics. However, the peptidome of the amniotic fluid in PE patients has rarely been investigated. The present study used peptidomic profiling to perform a comparative analysis of human amniotic fluid between normal and PE pregnancies. Centrifugal ultrafiltration and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was combined with isotopomeric dimethyl labels to gain a deeper understanding of the role of proteins and the peptidome in the onset of PE. Following ultrafiltration and LC-MS/MS, 352 peptides were identified. Of these, 23 peptides were observed to be significantly differentially expressed (6 downregulated and 17 upregulated; P<0.05). Using Gene Ontology and Blastp analyses, the functions and biological activities of these 23 peptides were identified and revealed to include autophagy, signal transduction, receptor activity, enzymatic activity and nucleic acid binding. In addition, a bibliographic search revealed that some of the identified peptides, including Titin, are crucial to the pathogenesis underlying PE. The present study identified 23 peptides expressed at significantly different levels in the amniotic fluid of PE and normal pregnancies. A comprehensive peptidome analysis is more efficient than a simple biomarker analysis at revealing deficiencies and improving the detection rate in diseases. These analyses therefore provide a substantial advantage in applications aimed at the discovery of disease-specific biomarkers.

Expression of Biglycan in First Trimester Chorionic Villous Sampling Placental Samples and Altered Function in Telomerase-Immortalized Microvascular Endothelial Cells

OBJECTIVE

Biglycan (BGN) has reduced expression in placentae from pregnancies complicated by fetal growth restriction (FGR). We used first trimester placental samples from pregnancies with later small for gestational age (SGA) infants as a surrogate for FGR. The functional consequences of reduced BGN and the downstream targets of BGN were determined. Furthermore, the expression of targets was validated in primary placental endothelial cells isolated from FGR or control pregnancies. APPROACH AND RESULTS: BGN expression was determined using real-time polymerase chain reaction in placental tissues collected during chorionic villous sampling performed at 10 to 12 weeks' gestation from pregnancies that had known clinical outcomes, including SGA. Short-interference RNA reduced BGN expression in telomerase-immortalized microvascular endothelial cells, and the effect on proliferation, angiogenesis, and thrombin generation was determined. An angiogenesis array identified downstream targets of BGN, and their expression in control and FGR primary placental endothelial cells was validated using real-time polymerase chain reaction. Reduced BGN expression was observed in SGA placental tissues. BGN reduction decreased network formation of telomerase-immortalized microvascular endothelial cells but did not affect thrombin generation or cellular proliferation. The array identified target genes, which were further validated: angiopoetin 4 (ANGPT4), platelet-derived growth factor receptor α (PDGFRA), tumor necrosis factor superfamily member 15 (TNFSF15), angiogenin (ANG), serpin family C member 1 (SERPIN1), angiopoietin 2 (ANGPT2), and CXC motif chemokine 12 (CXCL12) in telomerase-immortalized microvascular endothelial cells and primary placental endothelial cells obtained from control and FGR pregnancies.

CONCLUSIONS

This study reports a temporal relationship between altered placental BGN expression and subsequent development of SGA. Reduction of BGN in vascular endothelial cells leads to disrupted network formation and alterations in the expression of genes involved in angiogenesis. Therefore, differential expression of these may contribute to aberrant angiogenesis in SGA pregnancies.

Comprehensive analysis of preeclampsia-associated DNA methylation in the placenta

BACKGROUND

A small number of recent reports have suggested that altered placental DNA methylation may be associated with early onset preeclampsia. It is important that further studies be undertaken to confirm and develop these findings. We therefore undertook a systematic analysis of DNA methylation patterns in placental tissue from 24 women with preeclampsia and 24 with uncomplicated pregnancy outcome.

METHODS

We analyzed the DNA methylation status of approximately 27,000 CpG sites in placental tissues in a massively parallel fashion using an oligonucleotide microarray. Follow up analysis of DNA methylation at specific CpG loci was performed using the Epityper MassArray approach and high-throughput bisulfite sequencing.

RESULTS

Preeclampsia-specific DNA methylation changes were identified in placental tissue samples irrespective of gestational age of delivery. In addition, we identified a group of CpG sites within specific gene sequences that were only altered in early onset-preeclampsia (EOPET) although these DNA methylation changes did not correlate with altered mRNA transcription. We found evidence that fetal gender influences DNA methylation at autosomal loci but could find no clear association between DNA methylation and gestational age.

CONCLUSION

Preeclampsia is associated with altered placental DNA methylation. Fetal gender should be carefully considered during the design of future studies in which placental DNA is analyzed at the level of DNA methylation. Further large-scale analyses of preeclampsia-associated DNA methylation are necessary.

Genetic aspects of preeclampsia and the HELLP syndrome

Both preeclampsia and the HELLP syndrome have their origin in the placenta. The aim of this study is to review genetic factors involved in development of preeclampsia and the HELLP syndrome using literature search in PubMed. A familial cohort links chromosomes 2q, 5q, and 13q to preeclampsia. The chromosome 12q is coupled with the HELLP syndrome. The STOX1 gene, the ERAP1 and 2 genes, the syncytin envelope gene, and the −670 Fas receptor polymorphisms are involved in the development of preeclampsia. The ACVR2A gene on chromosome 2q22 is also implicated. The toll-like receptor-4 (TLR-4) and factor V Leiden mutation participate both in development of preeclampsia and the HELLP syndrome. Carriers of the TT and the CC genotype of the MTHFR C677T polymorphism seem to have an increased risk of the HELLP syndrome. The placental levels of VEGF mRNA are reduced both in women with preeclampsia and in women with the HELLP syndrome. The BclI polymorphism is engaged in development of the HELLP syndrome but not in development of severe preeclampsia. The ACE I/D polymorphism affects uteroplacental and umbilical artery blood flows in women with preeclampsia. In women with preeclampsia and the HELLP syndrome several genes in the placenta are deregulated. Preeclampsia and the HELLP syndrome are multiplex genetic diseases.

The Role of RNAs and microRNAs in Non-Invasive Prenatal Diagnosis

In this paper, all possible clinical applications of circulating mRNA and miRNA for non-invasive prenatal diagnosis appearing in the medical literature so far are described. Data from the literature have also been reported and commented on along with some possible future applications.

Differentially expressed genes in the pre-eclamptic placenta: a systematic review and meta-analysis

Objective

To systematically review the literature on human gene expression data of placental tissue in pre-eclampsia and to characterize a meta-signature of differentially expressed genes in order to identify novel putative diagnostic markers.

Data Sources

Medline through 11 February 2011 using MeSH terms and keywords related to placenta, gene expression and gene expression arrays; GEO database using the term “placent*”; and reference lists of eligible primary studies, without constraints.

Methods

From 1068 studies retrieved from the search, we included original publications that had performed gene expression array analyses of placental tissue in the third trimester and that reported on differentially expressed genes in pre-eclampsia versus normotensive controls. Two reviewers independently identified eligible studies, extracted descriptive and gene expression data and assessed study quality. Using a vote-counting method based on a comparative meta-profiling algorithm, we determined a meta-signature that characterizes the significant intersection of differentially expressed genes from the collection of independent gene signatures.

Results

We identified 33 eligible gene expression array studies of placental tissue in the 3^rd trimester comprising 30 datasets on mRNA expression and 4 datasets on microRNA expression. The pre-eclamptic placental meta-signature consisted of 40 annotated gene transcripts and 17 microRNAs. At least half of the mRNA transcripts encode a protein that is secreted from the cell and could potentially serve as a biomarker.

Conclusions

In addition to well-known and validated genes, we identified 14 transcripts not reported previously in relation to pre-eclampsia of which the majority is also expressed in the 1^st trimester placenta, and three encode a secreted protein.

Decreased levels of folate receptor-β and reduced numbers of fetal macrophages (Hofbauer cells) in placentas from pregnancies with severe pre-eclampsia

PROBLEM

Pre-eclampsia (PE), a pregnancy complication of unknown etiology, is a major cause of maternal and fetal mortality and morbidity. Previous studies have described placental genes that are up-regulated in expression in PE, but few studies have addressed placental gene suppression in this syndrome.

METHOD OF STUDY

Gene profiling and quantitative reverse transcription PCR (qRTPCR) analyses were used to identify genes down-regulated in placentas from women with severe preterm PE compared with gestational age-matched normotensive controls with spontaneous preterm birth (sPTB). Western blotting and immunohistochemistry were used to evaluate levels and patterns of cell type-specific protein expression in PE and sPTB group placentas.

RESULTS

Levels of macrophage marker [folate receptor (FR)-β, CD163, and CD68] mRNA and FR-β protein were significantly down-regulated in PE group placentas compared with the sPTB group. Numbers of Hofbauer cells (HBCs, fetal macrophages) and FR-β protein in these cells were reduced in PE group placentas.

CONCLUSION

Severe PE is associated with decreased placental expression of FR-β and a reduction in the number of HBCs. Reduced placental macrophage function is likely to play a key role in the pathophysiology of PE.

The amniotic fluid transcriptome: a source of novel information about human fetal development

OBJECTIVE

Amniotic fluid is a complex biological material that provides a unique window into the developing human. Residual amniotic fluid supernatant contains cell-free fetal RNA. The objective of this study was to develop an understanding of the amniotic fluid core transcriptome by analyzing the transcripts ubiquitously present in the amniotic fluid supernatant of euploid midtrimester fetuses.

METHODS

This was an in silico (computational) investigation using publicly available gene expression data previously produced by our group from 12 euploid midtrimester amniotic fluid samples. Functional analyses were performed using a web-based software analysis tool. Organ specificity was examined for each transcript using a gene expression atlas. For fetal organs not represented in the atlas, manual literature searching and the web-based software analysis tool were used to generate fetal organ-associated gene lists.

RESULTS

There were 476 well-annotated genes present in 12 of 12 amniotic fluid samples. Functional analysis identified six physiologic systems represented in the amniotic fluid core transcriptome, including musculoskeletal and nervous system development and function and embryonic and organismal development. Mammalian target of rapamycin signaling was identified as a key canonical pathway. Twenty-three highly organ-specific transcripts were identified; six of these are known to be highly expressed in the fetal brain.

CONCLUSION

Amniotic fluid cell-free fetal RNA can provide biological information on multiple fetal organ systems. The presence of fetal-brain specific transcripts in amniotic fluid suggests novel approaches to the study of developmental disorders that involve the central nervous system. The finding that the mammalian target of rapamycin signaling is enriched in midtrimester fetuses may have future applications in the study of fetal growth disorders.

Inflammatory pattern recognition receptors and their ligands: factors contributing to the pathogenesis of preeclampsia

Problem

Preeclampsia, a pregnancy-specific hypertensive syndrome, is one of the leading causes of premature births as well as fetal and maternal death. Preeclampsia lacks effective therapies because of the poor understanding of disease pathogenesis. The aim of this paper is to review molecular signaling pathways that could be responsible for the pathogenesis of preeclampsia.

Method of study

This article reviews the English-language literature for pathogenesis and pathophysiological mechanisms of preeclampsia based on genome-wide gene expression profiling and proteomic studies.

Results

We show that the expression of the genes and proteins involved in response to stress, host-pathogen interactions, immune system, inflammation, lipid metabolism, carbohydrate metabolism, growth and tissue remodeling was increased in preeclampsia. Several significant common pathways observed in preeclampsia overlap the datasets identified in TLR (Toll-like receptor)- and RAGE (receptor for advanced glycation end products)-dependent signaling pathways. Placental oxidative stress and subsequent chronic inflammation are considered to be major contributors to the development of preeclampsia.

Conclusion

This review summarizes recent advances in TLR- and RAGE-mediated signaling and the target molecules, and provides new insights into the pathogenesis of preeclampsia.