Placental HIF-1 alpha, HIF-2 alpha, membrane and soluble VEGF receptor-1 proteins are not increased in normotensive pregnancies complicated by late-onset intrauterine growth restriction

Blocking lactate regulation of the Grhl2/SLC31A1 axis inhibits trophoblast cuproptosis and preeclampsia development

PURPOSE

Abnormal cell death due to superficial trophoblast dysfunction caused by placental hypoxia plays a vital role in the development of preeclampsia (PE). Lactic acid stimulates gene transcription in chromatin through lactate modification of histone lysine. Nevertheless, the content and function of lactate in PE development remains largely unclear.

METHODS

The contents of lactic acid and copper in 30 PE and 30 normal placentas were determined by kit colorimetry. Real-time quantitative fluorescent PCR (qRT-PCR) and Western blot were used to detect the expression of SLC31A1 in cells and tissues. Cell proliferation, apoptosis, and invasion were detected by cell counting kit 8 (CCK-8), MTS assay, colony formation assay, and Transwell assay. The transcriptional regulation between Grhl2 and SLC31A was verified by the luciferase reporter gene method and ChIP. The H3K18la modification level was detected by ChIP-PCR.

RESULTS

Herein, we detected increased lactic acid levels in the PE placental tissue, which inhibit the proliferation and invasion of trophoblasts. Interestingly, lactic acid increases intracellular copper content by enhancing the expression of SLC31A1, a key protein of copper ion transporters. Lentivirus knockdown of SLC31A1 blocked the lactate-induced proliferation and invasion of trophoblasts by inhibiting cell cuproptosis. Mechanically, we identified that Grhl2 mediated SLC31A1 expression through transcription and participated in SLC31A1-inhibited proliferation, invasion, and cuproptosis of trophoblasts. Furthermore, the high lactate content increased Grhl2 expression by enhancing lactate modification of histone H3K18 in the Grhl2 promoter region.

CONCLUSIONS

Blocking the lactate-regulated Grhl2/SLC31A1 axis and trophoblastic cuproptosis may be a potential approach to prevent and treat PE.

Nitroxide-HMP-Protects Human Trophoblast HTR-8/SVneo Cells from H2O2-Induced Oxidative Stress by Reducing the HIF1A Signaling Pathway

Preeclampsia (PE) is a pregnancy-specific syndrome affecting 5-7% of patients. There is no effective treatment available. Early abnormal placental development is associated with oxidative stress (OS) and a release of reactive oxygen species (ROS) in the placenta. This phenomenon leads to downstream signaling, Hypoxia Inducible Factor 1A (HIF1A) stabilization and transcription of the anti-angiogenic factors soluble fms-like tyrosine kinase 1 (sFLT1) and soluble endoglin (sEng), which are known to cause endothelial and trophoblast dysfunction and cardinal features of PE: hypertension, proteinuria and, in severe cases, eclampsia. We tested whether 3-(Hydroxymethyl)-1-oxy-2,2,5,5-tetramethylpyrrolidine (HMP)-a nitroxide-type antioxidant molecule-can reduce placental OS and mitigate PE symptoms in vitro. We induced OS in human trophoblast (HTR-8/SVneo) cells with hydrogen peroxide (H2O2) and assessed whether modulating cell redox function with HMP reduces cell injury, mitochondrial stress and HIF1A and sFLT1 production. Pre-treatment with HMP reduced mitochondrial-derived ROS production, restored LC3B expression and reduced HIF1A and sFLT1 expression in H2O2-exposed HTR-8/SVneo trophoblast cells. HMP improved the mitochondrial electron chain enzyme activity, indicating that a reduction in OS alleviates mitochondrial stress and also reduces anti-angiogenic responses. In reducing placental trophoblast OS, HMP presents a potential novel therapeutic approach for the treatment of PE. Future investigation is warranted regarding the in vivo use of HMP.

An miRNA-mRNA integrative analysis in human placentas and mice: role of the Smad2/miR-155-5p axis in the development of fetal growth restriction

Introduction: Functional disorder of the placenta is the principal cause of fetal growth restriction (FGR), usually cured with suitable clinical treatment and good nursing. However, some FGR mothers still give birth to small for gestational age (SGA) babies after treatment. The ineffectiveness of treatment in such a group of patients confused physicians of obstetrics and gynecology. Methods: In this study, we performed a microRNA-messenger RNA integrative analysis of gene expression profiles obtained from Gene Expression Omnibus. Differentially expressed genes were screened and checked using quantitative polymerase chain reaction. Target genes of significantly changed microRNA were screened and enriched for Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses. Function of the obtained microRNA-messenger RNA was evaluated using HTR-8/SVneo trophoblast cells, human umbilical vein endothelial cells, and heterozygote male mice. Result: MiR-155-5p was upregulated (p = 0.001, fold-change = 2.275) in fetal-side placentals. Among the hub genes identified as key targets for miR-155-5p in fetal reprogramming, Smad2 was downregulated (p = 0.002, fold change = 0.426) and negatively correlated with miR-155-5p expression levels (r = -0.471, p < 1.0 E - 04) in fetal-side placental tissues. The miR-155-5p mimic blocks Smad2 expression and suppresses villous trophoblast cell and endothelial cell function (proliferation, migration, and invasion), indicating a close relationship with placental development. Luciferase assays further confirmed the targeting of miR-155-5p to Smad2. Furthermore, Smad2^+/- heterozygote male mice were born small with low body weight (p = 0.0281) and fat composition (p = 0.013) in the fourth week post-natal. Discussion: We provide the first evidence of the role of the Smad2/miR-155-5p axis in the placental pathologies of FGR. Our findings elucidate the pathogenesis of FGR and provide new therapeutic targets.

Dysregulation of Oxygen Sensing/Response Pathways in Pregnancies Complicated by Idiopathic Intrauterine Growth Restriction and Early-Onset Preeclampsia

Preeclampsia (PE) and intrauterine growth restriction (IUGR) are the leading causes of maternal and fetal morbidity/mortality. The central deficit in both conditions is impaired placentation due to poor trophoblast invasion, resulting in a hypoxic milieu in which oxidative stress contributes to the pathology. We examine the factors driving the hypoxic response in severely preterm PE (n = 19) and IUGR (n = 16) placentae compared to the spontaneous preterm (SPT) controls (n = 13) using immunoblotting, RT-PCR, immunohistochemistry, proximity ligation assays, and Co-IP. Both hypoxia-inducible factor (HIF)-1α and HIF-2α are increased at the protein level and functional in pathological placentae, as target genes prolyl hydroxylase domain (PHD)2, PHD3, and soluble fms-like tyrosine kinase-1 (sFlt-1) are increased. Accumulation of HIF-α-subunits occurs in the presence of accessory molecules required for their degradation (PHD1, PHD2, and PHD3 and the E3 ligase von Hippel–Lindau (VHL)), which were equally expressed or elevated in the placental lysates of PE and IUGR. However, complex formation between VHL and HIF-α-subunits is defective. This is associated with enhanced VHL/DJ1 complex formation in both PE and IUGR. In conclusion, we establish a significant mechanism driving the maladaptive responses to hypoxia in the placentae from severe PE and IUGR, which is central to the pathogenesis of both diseases.

Adaptations of the human placenta to hypoxia: opportunities for interventions in fetal growth restriction

BACKGROUND

The placenta is the functional interface between the mother and the fetus during pregnancy, and a critical determinant of fetal growth and life-long health. In the first trimester, it develops under a low-oxygen environment, which is essential for the conceptus who has little defense against reactive oxygen species produced during oxidative metabolism. However, failure of invasive trophoblasts to sufficiently remodel uterine arteries toward dilated vessels by the end of the first trimester can lead to reduced/intermittent blood flow, persistent hypoxia and oxidative stress in the placenta with consequences for fetal growth. Fetal growth restriction (FGR) is observed in ∼10% of pregnancies and is frequently seen in association with other pregnancy complications, such as preeclampsia (PE). FGR is one of the main challenges for obstetricians and pediatricians, as smaller fetuses have greater perinatal risks of morbidity and mortality and postnatal risks of neurodevelopmental and cardio-metabolic disorders.

OBJECTIVE AND RATIONALE

The aim of this review was to examine the importance of placental responses to changing oxygen environments during abnormal pregnancy in terms of cellular, molecular and functional changes in order to highlight new therapeutic pathways, and to pinpoint approaches aimed at enhancing oxygen supply and/or mitigating oxidative stress in the placenta as a mean of optimizing fetal growth.

SEARCH METHODS

An extensive online search of peer-reviewed articles using PubMed was performed with combinations of search terms including pregnancy, placenta, trophoblast, oxygen, hypoxia, high altitude, FGR and PE (last updated in May 2020).

OUTCOMES

Trophoblast differentiation and placental establishment are governed by oxygen availability/hypoxia in early pregnancy. The placental response to late gestational hypoxia includes changes in syncytialization, mitochondrial functions, endoplasmic reticulum stress, hormone production, nutrient handling and angiogenic factor secretion. The nature of these changes depends on the extent of hypoxia, with some responses appearing adaptive and others appearing detrimental to the placental support of fetal growth. Emerging approaches that aim to increase placental oxygen supply and/or reduce the impacts of excessive oxidative stress are promising for their potential to prevent/treat FGR.

WIDER IMPLICATIONS

There are many risks and challenges of intervening during pregnancy that must be considered. The establishment of human trophoblast stem cell lines and organoids will allow further mechanistic studies of the effects of hypoxia and may lead to advanced screening of drugs for use in pregnancies complicated by placental insufficiency/hypoxia. Since no treatments are currently available, a better understanding of placental adaptations to hypoxia would help to develop therapies or repurpose drugs to optimize placental function and fetal growth, with life-long benefits to human health.

Evidence of increased hypoxia signaling in fetal liver from maternal nutrient restriction in mice

BACKGROUND

Intrauterine growth restriction (IUGR) is a pregnancy condition where fetal growth is reduced, and offspring from IUGR pregnancies are at increased risk for type II diabetes as adults. The liver is susceptible to fetal undernutrition experienced by IUGR infants and animal models of growth restriction. This study aimed to examine hepatic expression changes in a maternal nutrient restriction (MNR) mouse model of IUGR to understand fetal adaptations that influence adult metabolism.

METHODS

Liver samples of male offspring from MNR (70% of ad libitum starting at E6.5) or control pregnancies were obtained at E18.5 and differential expression was assessed by RNAseq and western blots.

RESULTS

Forty-nine differentially expressed (FDR < 0.1) transcripts were enriched in hypoxia-inducible pathways including Fkbp5 (1.6-fold change), Ccng2 (1.5-fold change), Pfkfb3 (1.5-fold change), Kdm3a (1.2-fold change), Btg2 (1.6-fold change), Vhl (1.3-fold change), and Hif-3a (1.3-fold change) (FDR < 0.1). Fkbp5, Pfkfb3, Kdm3a, and Hif-3a were confirmed by qPCR, but only HIF-2a (2.2-fold change, p = 0.002) and HIF-3a (1.3 p = 0.03) protein were significantly increased.

CONCLUSION

Although a moderate impact, these data support evidence of fetal adaptation to reduced nutrients by increased hypoxia signaling in the liver.

Assessing the sensitivity of placental growth factor and soluble fms-like tyrosine kinase 1 at 36 weeks' gestation to predict small-for-gestational-age infants or late-onset preeclampsia: a prospective nested case-control study

Background

Fetal growth restriction is a disorder of placental dysfunction with three to four-fold increased risk of stillbirth. Fetal growth restriction has pathophysiological features in common with preeclampsia. We hypothesised that angiogenesis-related factors in maternal plasma, known to predict preeclampsia, may also detect fetal growth restriction at 36 weeks’ gestation. We therefore set out to determine the diagnostic performance of soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF), and the sFlt-1:PlGF ratio, measured at 36 weeks’ gestation, in identifying women who subsequently give birth to small-for-gestational-age (SGA; birthweight <10th centile) infants. We also aimed to validate the predictive performance of the analytes for late-onset preeclampsia in a large independent, prospective cohort.

Methods

A nested 1:2 case-control study was performed including 102 cases of SGA infants and a matched group of 207 controls; and 39 cases of preeclampsia. We determined the diagnostic performance of each angiogenesis-related factor, and of their ratio, to detect SGA infants or preeclampsia, for a predetermined 10% false positive rate.

Results

Median plasma levels of PlGF at 36 weeks’ gestation were significantly lower in women who subsequently had SGA newborns (178.5 pg/ml) compared to normal birthweight controls (326.7 pg/ml, p < 0.0001). sFlt-1 was also higher among SGA cases, but this was not significant after women with concurrent preeclampsia were excluded. The sensitivity of PlGF to predict SGA infants was 28.8% for a 10% false positive rate. The sFlt-1:PlGF ratio demonstrated better sensitivity for preeclampsia than either analyte alone, detecting 69.2% of cases for a 10% false positive rate.

Conclusions

Plasma PlGF at 36 weeks’ gestation is significantly lower in women who subsequently deliver a SGA infant. While the sensitivity and specificity of PlGF currently limit clinical translation, our findings support a blood-based biomarker approach to detect late-onset fetal growth restriction. Thirty-six week sFlt-1:PlGF ratio predicts 69.2% of preeclampsia cases, and could be a useful screening test to triage antenatal surveillance.

Electronic supplementary material

The online version of this article (10.1186/s12884-018-1992-x) contains supplementary material, which is available to authorized users.

Humanin (HN) and glucose transporter 8 (GLUT8) in pregnancies complicated by intrauterine growth restriction

Background

Intrauterine growth restriction (IUGR) results from a lack of nutrients transferred to the developing fetus, particularly oxygen and glucose. Increased expression of the cytoprotective mitochondrial peptide, humanin (HN), and the glucose transporter 8, GLUT8, has been reported under conditions of hypoxic stress. However, the presence and cellular localization of HN and GLUT8 in IUGR-related placental pathology remain unexplored. Thus, we undertook this study to investigate placental expression of HN and GLUT8 in IUGR-affected versus normal pregnancies.

Results

We found 1) increased HN expression in human IUGR-affected pregnancies on the maternal aspect of the placenta (extravillous trophoblastic (EVT) cytoplasm) compared to control (i.e. appropriate for gestational age) pregnancies, and a concomitant increase in GLUT8 expression in the same compartment, 2) HN and GLUT8 showed a protein-protein interaction by co-immunoprecipitation, 3) elevated HN and GLUT8 levels in vitro under simulated hypoxia in human EVT cells, HTR8/SVneo, and 4) increased HN expression but attenuated GLUT8 expression in vitro under serum deprivation in HTR8/SVneo cells.

Conclusions

There was elevated HN expression with cytoplasmic localization to EVTs on the maternal aspect of the human placenta affected by IUGR, also associated with increased GLUT8 expression. We found that while hypoxia increased both HN and GLUT8, serum deprivation increased HN expression alone. Also, a protein-protein interaction between HN and GLUT8 suggests that their interaction may fulfill a biologic role that requires interdependency. Future investigations delineating molecular interactions between these proteins are required to fully uncover their role in IUGR-affected pregnancies.

Placental hypoxia-regulating network in relation to birth weight and ponderal index: the ENVIRONAGE Birth Cohort Study

BACKGROUND

HIF1α, miR-210 and its downstream targets ISCU, COX-10, RAD52 and PTEN are all part of the placental hypoxia-responsive network. Tight regulation of this network is required to prevent development of maternal-fetal complications such as fetal growth restriction. HIF1α expression is increased in preeclamptic placentae, but little is known about its association with birth weight in normal pregnancies.

METHODS

We measured placental levels of HIF1α, miR-20a, miR-210, ISCU, COX-10, RAD52 and PTEN in 206 mother-newborn pairs of the ENVIRONAGE birth cohort.

RESULTS

Placental HIF1α gene expression was inversely associated with the ponderal index (PI): for a doubling in placental HIF1α expression, PI decreased by 6.7% (95% confidence interval [CI] 1.3 to 12.0%, p = 0.01). Placental RAD52 expression also displayed an inverse association with PI, a doubling in gene expression was associated with a 6.2% (CI 0.2 to 12.1% p = 0.04) decrease in PI. As for birth weight, we observed a significant association with placental miR-20a expression only in boys, where a doubling in miR-20a expression is associated with a 54.2 g (CI 0.6 to 108 g, p = 0.05) increase in birth weight.

CONCLUSIONS

The decrease in fetal growth associated with expression of hypoxia-network members HIF1a, RAD52 and miR-20a indicates that this network is important in potential intrauterine insults.

Emerging role for dysregulated decidualization in the genesis of preeclampsia

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

Placental origins of adverse pregnancy outcomes: potential molecular targets: an Executive Workshop Summary of the Eunice Kennedy Shriver National Institute of Child Health and Human Development

Although much progress is being made in understanding the molecular pathways in the placenta that are involved in the pathophysiology of pregnancy-related disorders, a significant gap exists in the utilization of this information for the development of new drug therapies to improve pregnancy outcome. On March 5-6, 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health sponsored a 2-day workshop titled Placental Origins of Adverse Pregnancy Outcomes: Potential Molecular Targets to begin to address this gap. Particular emphasis was given to the identification of important molecular pathways that could serve as drug targets and the advantages and disadvantages of targeting these particular pathways. This article is a summary of the proceedings of that workshop. A broad number of topics were covered that ranged from basic placental biology to clinical trials. This included research in the basic biology of placentation, such as trophoblast migration and spiral artery remodeling, and trophoblast sensing and response to infectious and noninfectious agents. Research findings in these areas will be critical for the formulation of the development of future treatments and the development of therapies for the prevention of a number of pregnancy disorders of placental origin that include preeclampsia, fetal growth restriction, and uterine inflammation. Research was also presented that summarized ongoing clinical efforts in the United States and in Europe that has tested novel interventions for preeclampsia and fetal growth restriction, including agents such as oral arginine supplementation, sildenafil, pravastatin, gene therapy with virally delivered vascular endothelial growth factor, and oxygen supplementation therapy. Strategies were also proposed to improve fetal growth by the enhancement of nutrient transport to the fetus by modulation of their placental transporters and the targeting of placental mitochondrial dysfunction and oxidative stress to improve placental health. The roles of microRNAs and placental-derived exosomes, as well as messenger RNAs, were also discussed in the context of their use for diagnostics and as drug targets. The workshop discussed the aspect of safety and pharmacokinetic profiles of potential existing and new therapeutics that will need to be determined, especially in the context of the unique pharmacokinetic properties of pregnancy and the hurdles and pitfalls of the translation of research findings into practice. The workshop also discussed novel methods of drug delivery and targeting during pregnancy with the use of macromolecular carriers, such as nanoparticles and biopolymers, to minimize placental drug transfer and hence fetal drug exposure. In closing, a major theme that developed from the workshop was that the scientific community must change their thinking of the pregnant woman and her fetus as a vulnerable patient population for which drug development should be avoided, but rather be thought of as a deprived population in need of more effective therapeutic interventions.

Preeclampsia in twin pregnancies: association with selective intrauterine growth restriction

OBJECTIVE

To identify the association between preeclampsia (PE) and selective intrauterine growth restriction (sIUGR) in twin pregnancies.

METHODS

This was a retrospective cohort study of 1004 twin pregnancies from 2008 to 2014. We specifically compared the incidence, clinical characteristics and outcomes of PE between sIUGR and normal-growth twin pregnancies.

RESULTS

PE occurred more frequently in sIUGR pregnancies [29.0% (51/176)] than in normal-growth twin pregnancies [13.1% (99/756), p < 0.001, adjusted odds ratio 3.29]. Among sIUGR, the incidence of PE was significantly higher in dichorionic (DC) pregnancies (37.5%, 30/80) than in monochorionic (MC) pregnancies (21.9%, 21/96). The rates of onset at <32 weeks (p = 0.045) and of severe PE (p = 0.025) were higher in sIUGR pregnancies with PE. The systolic blood pressure was also higher in sIUGR pregnancies with PE (152.6 ± 11.8 mmHg) than in normal-growth pregnancies with PE (148.0 ± 8.2 mmHg) (p = 0.042). Additionally, more sIUGR pregnancies were delivered at 32-36 weeks (p = 0.001), and fewer were delivered at ≥36 weeks (p < 0.001). Moreover, the prevalence of severe neonatal asphyxia was higher in sIUGR pregnancies with PE than in normal-growth pregnancies with PE (8.8% versus 2.5%, p = 0.020).

CONCLUSIONS

sIUGR is associated with increased odds of developing severe PE in twin pregnancies, leading to poorer perinatal outcomes.

The difference of lymphocyte subsets including regulatory T-cells in umbilical cord blood between AGA neonates and SGA neonates

PURPOSE

This study aimed to compare the regulatory T cells in cord blood of appropriate for gestational age (AGA) neonates with those of small for gestational age (SGA) neonates.

MATERIALS AND METHODS

Umbilical cord blood was collected upon labor in 108 healthy full-term (between 37 and 41 gestational weeks) neonates, who were born between November 2010 and April 2012. Among them, 77 samples were obtained from AGA neonates, and 31 samples were obtained from SGA neonates. Regulatory T cells and lymphocyte subsets were determined using a flow cytometer. Student's t-test for independent samples was used to compare differences between AGA and SGA neonates.

RESULTS

Regulatory T cells in cord blood were increased in the SGA group compared with normal controls (p=0.041). However, cytotoxic T cells in cord blood were significantly decreased in the SGA group compared with normal controls (p=0.007).

CONCLUSION

This is the first study to compare the distribution of lymphocyte subsets including regulatory T cells in cord blood between AGA neonates and SGA neonates.

Intrauterine telemetry to measure mouse contractile pressure in vivo

A complex integration of molecular and electrical signals is needed to transform a quiescent uterus into a contractile organ at the end of pregnancy. Despite the discovery of key regulators of uterine contractility, this process is still not fully understood. Transgenic mice provide an ideal model in which to study parturition. Previously, the only method to study uterine contractility in the mouse was ex vivo isometric tension recordings, which are suboptimal for several reasons. The uterus must be removed from its physiological environment, a limited time course of investigation is possible, and the mice must be sacrificed. The recent development of radiometric telemetry has allowed for longitudinal, real-time measurements of in vivo intrauterine pressure in mice. Here, the implantation of an intrauterine telemeter to measure pressure changes in the mouse uterus from mid-pregnancy until delivery is described. By comparing differences in pressures between wild type and transgenic mice, the physiological impact of a gene of interest can be elucidated. This technique should expedite the development of therapeutics used to treat myometrial disorders during pregnancy, including preterm labor.

The SK3 channel promotes placental vascularization by enhancing secretion of angiogenic factors

Proper placental perfusion is essential for fetal exchange of oxygen, nutrients, and waste with the maternal circulation. Impairment of uteroplacental vascular function can lead to pregnancy complications, including preeclampsia and intrauterine growth restriction (IUGR). Potassium channels have been recognized as regulators of vascular proliferation, angiogenesis, and secretion of vasoactive factors, and their dysfunction may underlie pregnancy-related vascular diseases. Overexpression of one channel in particular, the small-conductance calcium-activated potassium channel 3 (SK3), is known to increase vascularization in mice, and mice overexpressing the SK3 channel (SK3(T/T) mice) have a high rate of fetal demise and IUGR. Here, we show that overexpression of SK3 causes fetal loss through abnormal placental vascularization. We previously reported that, at pregnancy day 14, placentas isolated from SK3(T/T) mice are smaller than those obtained from wild-type mice. In this study, histological analysis reveals that SK3(T/-) placentas at this stage have abnormal placental morphology, and microcomputed tomography shows that these placentas have significantly larger and more blood vessels than those from wild-type mice. To identify the mechanism by which these vascularization defects occur, we measured levels of vascular endothelial growth factor (VEGF), placental growth factor, and the soluble form of VEGF receptor 1 (sFlt-1), which must be tightly regulated to ensure proper placental development. Our data reveal that overexpression of SK3 alters systemic and placental ratios of the angiogenic factor VEGF to antiangiogenic factor sFlt-1 throughout pregnancy. Additionally, we observe increased expression of hypoxia-inducing factor 2α in SK3(T/-) placentas. We conclude that the SK3 channel modulates placental vascular development and fetal health by altering VEGF signaling.

Angiogenic and inflammatory biomarkers in midpregnancy and small-for-gestational-age outcomes in Tanzania

OBJECTIVE

We sought to investigate the relationship between a panel of angiogenic and inflammatory biomarkers measured in midpregnancy and small-for-gestational-age (SGA) outcomes in sub-Saharan Africa.

STUDY DESIGN

Concentrations of 18 angiogenic and inflammatory biomarkers were determined in 432 pregnant women in Dar es Salaam, Tanzania, who participated in a trial examining the effect of multivitamins on pregnancy outcomes. Infants falling below the 10th percentile of birthweight for gestational age relative to the applied growth standards were considered SGA. Multivariate binomial regression models with the log link function were used to determine the relative risk of SGA associated with increasing quartiles of each biomarker. Restricted cubic splines were used to test for nonlinearity of these associations.

RESULTS

A total of 60 participants (13.9%) gave birth to SGA infants. Compared to those in the first quartile, the risk of SGA was reduced among those in the fourth quartiles of vascular endothelial growth factor-A (adjusted risk ratio [RR], 0.38; 95% confidence interval [CI], 0.19-0.74), placental growth factor (adjusted RR, 0.28; 95% CI, 0.12-0.61), soluble fms-like tyrosine kinase-1 (adjusted RR, 0.48; 95% CI, 0.23-1.01), monocyte chemoattractant protein-1 (adjusted RR, 0.48; 95% CI, 0.25-0.92), and leptin (adjusted RR, 0.46; 95% CI, 0.22-0.96).

CONCLUSION

Our findings provide evidence of altered angiogenic and inflammatory mediators, at midpregnancy, in women who went on to deliver SGA infants.

Placental development during early pregnancy in sheep: effects of embryo origin on vascularization

Utero-placental growth and vascular development are critical for pregnancy establishment that may be altered by various factors including assisted reproductive technologies (ART), nutrition, or others, leading to compromised pregnancy. We hypothesized that placental vascularization and expression of angiogenic factors are altered early in pregnancies after transfer of embryos created using selected ART methods. Pregnancies were achieved through natural mating (NAT), or transfer of embryos from NAT (NAT-ET), or IVF or in vitro activation (IVA). Placental tissues were collected on day 22 of pregnancy. In maternal caruncles (CAR), vascular cell proliferation was less (P<0.05) for IVA than other groups. Compared with NAT, density of blood vessels was less (P<0.05) for IVF and IVA in fetal membranes (FM) and for NAT-ET, IVF, and IVA in CAR. In FM, mRNA expression was decreased (P<0.01-0.08) in NAT-ET, IVF, and IVA compared with NAT for vascular endothelial growth factor (VEGF) and its receptor FLT1, placental growth factor (PGF), neuropilin 1 (NP1) and NP2, angiopoietin 1 (ANGPT1) and ANGPT2, endothelial nitric oxide synthase 3 (NOS3), hypoxia-inducible factor 1A (HIF1A), fibroblast growth factor 2 (FGF2), and its receptor FGFR2. In CAR, mRNA expression was decreased (P<0.01-0.05) in NAT-ET, IVF, and IVA compared with NAT for VEGF, FLT1, PGF, ANGPT1, and TEK. Decreased mRNA expression for 12 of 14 angiogenic factors across FM and CAR in NAT-ET, IVF, and IVA pregnancies was associated with reduced placental vascular development, which would lead to poor placental function and compromised fetal and placental growth and development.

Placental glucose transporter 3 (GLUT3) is up-regulated in human pregnancies complicated by late-onset intrauterine growth restriction

INTRODUCTION

Transport of glucose from maternal blood across the placental trophoblastic tissue barrier is critical to sustain fetal growth. The mechanism by which GLUTs are regulated in trophoblasts in response to ischemic hypoxia encountered with intrauterine growth restriction (IUGR) has not been suitably investigated.

OBJECTIVE

To investigate placental expression of GLUT1, GLUT3 and GLUT4 and possible mechanisms of GLUT regulation in idiopathic IUGR.

METHODS

We analyzed clinical, biochemical and histological data from placentas collected from women affected by idiopathic full-term IUGR (n = 10) and gestational age-matched healthy controls (n = 10).

RESULTS

We found increased GLUT3 protein expression in the trophoblast (cytotrophoblast greater than syncytiotrophoblast) on the maternal aspect of the placenta in IUGR compared to normal placenta, but no differences in GLUT1 or GLUT4 were found. No differential methylation of the GLUT3 promoter between normal and IUGR placentas was observed. Increased GLUT3 expression was associated with an increased nuclear concentration of HIF-1α, suggesting hypoxia may play a role in the up-regulation of GLUT3.

DISCUSSION

Further studies are needed to elucidate whether increased GLUT3 expression in IUGR is a marker for defective villous maturation or an adaptive response of the trophoblast in response to chronic hypoxia.

CONCLUSIONS

Patients with IUGR have increased trophoblast expression of GLUT3, as found under the low-oxygen conditions of the first trimester.

VEGF, PIGF and HIF-1α in placentas of early- and late-onset pre-eclamptic patients

PURPOSE

The aim of this study was to compare the VEGF, PIGF, and HIF-1α levels in the placentas of early- and late-onset pre-eclamptic patients, which are thought to be important in pathophysiology of pre-eclampsia.

MATERIAL AND METHOD

Pre-eclamptic early-onset (n = 22) and late-onset (n = 24) pregnant women and a control group of healthy pregnant women (n = 22) were recruited for this case-control study. A semi-quantitative immunohistochemical analysis of VEGF, PIGF and HIF-1α was performed in cross-sections of the placentas of the subjects, after which results were compared.

RESULTS

Levels of VEGF and PIGF in the placentas of pre-eclamptic patients were found to be lower than the levels in the placentas of healthy pregnant women (p < 0.001 and p = 0.025, respectively), whereas the levels of HIF-1α were found significantly higher (p < 0.001). No difference was observed in terms of VEGF, PIGF and HIF-1α in a comparison of the early- and late-onset pre-eclampsia groups (p > 0.05).

CONCLUSION

The results of the study indicated that there is no relationship between the time of onset of pre-eclampsia and the placental changes that occur in these factors.

Conversion of peripheral blood NK cells to a decidual NK-like phenotype by a cocktail of defined factors

NK cells that populate the decidua are important regulators of normal placentation. In contrast to peripheral blood NK cells, decidual NK (dNK) cells lack cytotoxicity, secrete proangiogenic factors, and regulate trophoblast invasion. In this study we show that exposure to a combination of hypoxia, TGF-β1, and a demethylating agent results in NK cells that express killer cell Ig-like receptors, the dNK cell markers CD9 and CD49a, and a dNK pattern of chemokine receptors. These cells secrete vascular endothelial growth factor (a potent proangiogenic molecule), display reduced cytotoxicity, and promote invasion of human trophoblast cell lines. These findings have potential therapeutic applications for placental disorders associated with altered NK cell biology.

The placenta in preeclampsia

The root cause of preeclampsia is the placenta. Preeclampsia begins to abate with the delivery of the placenta and can occur in the absence of a fetus but with the presence of trophoblast tissue with hydatidiform moles. In view of this, study of the placenta should provide insight into the pathophysiology of preeclampsia. In this presentation we examine placental pathological and pathophysiological changes with preeclampsia and fetal growth restriction (FGR). It would seem that this comparison should be illuminating as both conditions are associated with similarly abnormal placentation yet only in preeclampsia is there a maternal pathophysiological syndrome. Similar insights about early and late onset preeclampsia should also be provided by such information.We report that the placental abnormalities in preeclampsia are what would be predicted in a setting of reduced perfusion and oxidative stress. However, the differences from FGR are inconsistent. The most striking differences between the two conditions are found in areas that have been the least studied. There are differences between the placental findings in early and late onset preeclampsia but whether these are qualitative, indicating different diseases, or simply quantitative differences within the same disease is difficult to determine.We attempt to decipher the true differences, seek an explanation for the disparate results and provide recommendations that we hope may help resolve these issues in future studies.

Expansion of the fetoplacental vasculature in late gestation is strain dependent in mice

How the fetoplacental arterial tree grows and expands during late gestational development is largely unknown. In this study, we quantified changes in arterial branching in the fetal exchange region of the mouse placenta during late gestation, when capillarization increases rapidly. We studied two commonly used mouse strains, CD1 and C57Bl/6 (B6), at embryonic days (E)13.5, 15.5, and 17.5. B6 mice differ from CD1 mice by exhibiting a blunted fetal weight gain in late gestation. We found that B6 capillarization and interhemal membrane thinning were reduced and placental hypoxia-inducible factor-1α and VEGF-A expression were higher than CD1 near term. Automated vascular segmentation of microcomputed tomography data sets revealed that the number of arterial vessels ≥50 μm remained constant during late gestation in both strains, despite large increases in downstream capillary volume quantified by stereology (+65% in B6 mice and +200% in CD1 mice). Arterial diameters expanded in both strains from E13.5 to E15.5; however, diameters continued to expand to E17.5 in B6 mice only. The diameter scaling coefficient at branch sites was near optimal (-3.0) and remained constant in CD1 mice, whereas it decreased, becoming abnormal, in B6 mice at term (-3.5 ± 0.2). Based on arterial tree geometry, resistance remained constant throughout late gestation (∼0.45 mmHg·s·μl(-1)) in CD1 mice, whereas it decreased by 50% in late gestation in B6 mice. Quantification of the fetoplacental vasculature revealed significant strain-dependent differences in arterial and capillary expansion in late gestation. In both strains, enlargement of the fetoplacental arterial tree occurred primarily by increased arterial diameters with no change in segment numbers in late gestation.

Humans at high altitude: hypoxia and fetal growth

High-altitude studies offer insight into the evolutionary processes and physiological mechanisms affecting the early phases of the human lifespan. Chronic hypoxia slows fetal growth and reduces the pregnancy-associated rise in uterine artery (UA) blood flow. Multigenerational vs. shorter-term high-altitude residents are protected from the altitude-associated reductions in UA flow and fetal growth. Presently unknown is whether this fetal-growth protection is due to the greater delivery or metabolism of oxygen, glucose or other substrates or to other considerations such as mechanical factors protecting fragile fetal villi, the creation of a reserve protecting against ischemia/reperfusion injury, or improved placental O(2) transfer as the result of narrowing the A-V O(2) difference and raising uterine P(v)O₂. Placental growth and development appear to be normal or modified at high altitude in ways likely to benefit diffusion. Much remains to be learned concerning the effects of chronic hypoxia on embryonic development. Further research is required for identifying the fetoplacental and maternal mechanisms responsible for transforming the maternal vasculature and regulating UA blood flow and fetal growth. Genomic as well as epigenetic studies are opening new avenues of investigation that can yield insights into the basic pathways and evolutionary processes involved.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Expression of placental FLT1 transcript variants relates to both gestational hypertensive disease and fetal growth

The recent discovery of additional alternative spliced FLT1 transcripts encoding novel soluble (s)FLT1 protein isoforms complicates both the predictive value and functional implications of sFLT1 in preeclampsia. We investigated FLT1 expression levels and splicing patterns in placentas of normotensive and preeclamptic women, and established the tissue specificity of all FLT1 transcript variants. mRNA levels of sFLT1 splice variants were determined by real-time polymerase chain reaction in 21 normal human tissues and placental biopsies from 91 normotensive and 55 preeclamptic women. Cellular localization of placental FLT1 expression was established by RNA in situ hybridization. Of all tissues investigated, placenta has by far the highest FLT1 mRNA expression level, mainly localized in the syncytiotrophoblast layer. More than 80% of placental transcripts correspond to sFLT1_v2. Compared with normotensive placenta, preeclamptic placenta has ≈3-fold higher expression of all FLT1 transcript variants (P<0.001), with a slight shift in favor of sFLT1_v1. Although to a lesser degree, transcript levels are also increased in placenta from normotensive women that deliver a small for gestational age neonate. We conclude that sFLT isoform-specific assays could potentially improve the accuracy of current sFLT1 assays for the prediction of preeclampsia. However, placental FLT1 transcript levels are increased not only in preeclampsia but also in normotensive pregnancy with a small for gestational age fetus. This may indicate a common pathway involved in the development of both conditions but complicates the use of circulating sFLT1 protein levels for the prediction or diagnosis of preeclampsia alone.

Placental development during early pregnancy in sheep: cell proliferation, global methylation, and angiogenesis in the fetal placenta

To characterize early fetal placental development, gravid uterine tissues were collected from pregnant ewes every other day from day 16 to 30 after mating. Determination of 1) cell proliferation was based on Ki67 protein immunodetection; 2) global methylation was based on 5-methyl-cytosine (5mC) expression and mRNA expression for DNA methyltransferases (DNMTs)1,3a, and3b; and 3) vascular development was based on smooth muscle cell actin immunolocalization and on mRNA expression of several factors involved in the regulation of angiogenesis in fetal membranes (FMs). Throughout early pregnancy, the labeling index (proportion of proliferating cells) was very high (21%) and did not change. Expression of 5mC and mRNA forDNMT3bdecreased, but mRNA forDNMT1and3aincreased. Blood vessels were detected in FM on days 18–30 of pregnancy, and their number per tissue area did not change. The patterns of mRNA expression for placental growth factor, vascular endothelial growth factor, and their receptorsFLT1andKDR; angiopoietins 1 and 2 and their receptorTEK; endothelial nitric oxide synthase and the NO receptorGUCY13B; and hypoxia inducing factor 1 α changed in FM during early pregnancy. These data demonstrate high cellular proliferation rates, and changes in global methylation and mRNA expression of factors involved in the regulation of DNA methylation and angiogenesis in FM during early pregnancy. This description of cellular and molecular changes in FM during early pregnancy will provide the foundation for determining the basis of altered placental development in pregnancies compromised by environmental, genetic, or other factors.

The origins and end-organ consequence of pre-eclampsia

Pre-eclampsia is a multisystem disorder with profound implications for both mother and fetus. Its origins lie in the earliest stages of pregnancy. Abnormal interactions between fetal trophoblast and maternal decidua, including the cells of the maternal immune system, lead to inadequate placental invasion and maternal vascular remodelling. However, abnormal placentation is only one step in the cascade of events that ultimately result in maternal organ dysfunction. Pre-existing maternal conditions predisposing to inflammation and vascular pathology, fetal factors, including multiple gestations and macrosomia, and environmental exposures, including infection, may contribute to the release of placental substances, including anti-angiogenic molecules, into the maternal circulation. These may act directly or indirectly upon the endothelia of end organs, including the kidney, liver and brain. The liberation of reactive oxygen species, cytokines, and microthrombi from damaged endothelia contribute further to organ damage. In studying the normal processes that occur during human placentation and early pregnancy, we will develop a greater understanding of what may go awry in pre-eclampsia. Such research will be crucial in discovering novel biomarkers for prediction of the disorder and, eventually, in finding targets for effective interventions.

High-end arteriolar resistance limits uterine artery blood flow and restricts fetal growth in preeclampsia and gestational hypertension at high altitude

The reduction in infant birth weight and increased frequency of preeclampsia (PE) in high-altitude residents have been attributed to greater placental hypoxia, smaller uterine artery (UA) diameter, and lower UA blood flow (Q(UA)). This cross-sectional case-control study determined UA, common iliac (CI), and external iliac (EI) arterial blood flow in Andeans residing at 3,600-4,100 m, who were either nonpregnant (NP, n = 23), or experiencing normotensive pregnancies (NORM; n = 155), preeclampsia (PE, n = 20), or gestational hypertension (GH, n = 12). Pregnancy enlarged UA diameter to ~0.62 cm in all groups, but indices of end-arteriolar vascular resistance were higher in PE or GH than in NORM. Q(UA) was lower in early-onset (≤34 wk) PE or GH than in NORM, but was normal in late-onset (>34 wk) illness. Left Q(UA) was consistently greater than right in NORM, but the pattern reversed in PE. Although Q(CI) and Q(EI) were higher in PE and GH than NORM, the fraction of Q(CI) distributed to the UA was reduced 2- to 3-fold. Women with early-onset PE delivered preterm, and 43% had stillborn small for gestational age (SGA) babies. Those with GH and late-onset PE delivered at term but had higher frequencies of SGA babies (GH=50%, PE=46% vs. NORM=15%, both P < 0.01). Birth weight was strongly associated with reduced Q(UA) (R(2) = 0.80, P < 0.01), as were disease severity and adverse fetal outcomes. We concluded that high end-arteriolar resistance, not smaller UA diameter, limited Q(UA) and restricted fetal growth in PE and GH. These are, to our knowledge, the first quantitative measurements of Q(UA) and pelvic blood flow in early- vs. late-onset PE in high-altitude residents.

Emerging role of relaxin in the maternal adaptations to normal pregnancy: implications for preeclampsia

Relaxin is an approximately 6-kilodalton peptide hormone secreted by the corpus luteum, and circulates in the maternal blood during pregnancy. Relaxin administration to awake, chronically instrumented, nonpregnant rats mimics the vasodilatory phenomena of pregnancy. Furthermore, immunoneutralization of relaxin or its elimination from the circulation during midterm pregnancy in awake rats prevents maternal systemic and renal vasodilation, and the increase in global arterial compliance. Human investigation, albeit limited through 2010, also reveals vasodilatory effects of relaxin in the nonpregnant condition and observations consistent with a role for relaxin in gestational renal hyperfiltration. Evidence suggests that the vasodilatory responses of relaxin are mediated by its major receptor, the relaxin/insulin-like family peptide 1 receptor, RFXP1. The molecular mechanisms of relaxin vasodilation depend on the duration of hormone exposure (ie, there are rapid and sustained vasodilatory responses). Newly emerging data support the role of Gα(i/o) protein coupling to phosphatidylinositol-3 kinase/Akt (protein kinase B)-dependent phosphorylation and activation of endothelial nitric oxide synthase in the rapid vasodilatory responses of relaxin. Sustained vasodilatory responses critically depend on vascular endothelial and placental growth factors, and increases in arterial gelatinase(s) activity. Gelatinases hydrolyze big endothelin (ET) at a gly-leu bond to form ET(1-32), which activates the endothelial ET(B)/nitric oxide vasodilatory pathway. Although the relevance of relaxin biology to preeclampsia is largely speculative at this time, there are potential tantalizing links that are discussed in the context of our current understanding of the etiology and pathophysiology of the disease.

Reduced placental prolyl hydroxylase 3 mRNA expression in pregnancies affected by fetal growth restriction

OBJECTIVE

To investigate the role of the hypoxia-inducible factor (HIF) pathway in fetal growth restriction (FGR).

DESIGN

A case-control study.

SETTING

Research laboratory and gynaecology clinic.

SAMPLE

Twenty placentas from normal pregnancies and 20 from FGR pregnancies.

METHODS

RNA extraction, cDNA synthesis, quantitative real-time polymerase chain reaction (qRT-PCR) assay, statistical analysis.

MAIN OUTCOME MEASURES

mRNA expression of HIF-1α, HIF-2α and HIF-β (ARNT), along with prolyl hydroxylase domain 3 (PHD3), which leads to proteasomal degradation of HIF-α subunits.

RESULTS

No statistically significant differences in the transcription levels of ARNT and HIF-2α were found between FGR and normal placentas. By contrast, PHD3 and HIF-1α mRNA were downregulated in FGR placentas. PHD3 mRNA expression was associated with gestational age at delivery (P = 0.008), birthweight centile (P = 0.029) and abnormal umbilical artery (UA) Doppler measurements (P = 0.034).

CONCLUSIONS

As PHD3 regulates the HIF-mediated hypoxic response in FGR, we deduce that fetal adaptation to hypoxia ranges from impaired to adequate, as observed by the gradient of PHD3 downregulation in relation to the severity of FGR.

Dysregulation of promyelocytic leukemia (PML) protein expression in preeclamptic placentae

Promyelocytic leukemia (PML) protein is a nucleoprotein that can regulate a variety of cellular stress responses. The aim of this study was to determine qualitative and quantitative changes in PML expression in preeclamptic placentae. Immunoblot, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and immunohistochemistry techniques were used to determine PML gene expression and localization in normal (n = 6) and preeclamptic (n = 6) placentae and primary cells. Promyelocytic leukemia protein was immunolocalized within nuclei of villus mesenchyme, but largely absent in trophoblast nuclei, with a trend for increased PML reactivity in preeclamptic placenta. Immunoblot analyses of nuclear extracts confirmed relative increases (approximately 3-fold) of PML expression in preeclamptic placentae (P < .05). Conversely, less PML messenger RNA (mRNA; approximately 2-fold) was detected in preeclamptic versus normal placental samples. In vitro, PML expression could be increased by hypoxia in cultured endothelial cells but not trophoblast. Increased PML protein expression in preeclamptic villi suggests it could contribute to decreased vascularity and placental growth and/or function.

Beyond oxygen: complex regulation and activity of hypoxia inducible factors in pregnancy

In the first trimester the extravillous cytotrophoblast cells occlude the uterine spiral arterioles creating a low oxygen environment early in pregnancy, which is essential for pregnancy success. Paradoxically, shallow trophoblast invasion and defective vascular remodelling of the uterine spiral arteries in the first trimester may result in impaired placental perfusion and chronic placental ischemia and hypoxia later in gestation leading to adverse pregnancy outcomes. The hypoxia inducible factors (HIFs) are key mediators of the response to low oxygen. We aimed to elucidate mechanisms of regulation of HIFs and the role these may play in the control of placental differentiation, growth and function in both normal and pathological pregnancies. The Pubmed database was consulted for identification of the most relevant published articles. Search terms used were oxygen, placenta, trophoblast, pregnancy, HIF and hypoxia. The HIFs are able to function throughout all aspects of normal and abnormal placental differentiation, growth and function; during the first trimester (physiologically low oxygen), during mid-late gestation (where there is adequate supply of blood and oxygen to the placenta) and in pathological pregnancies complicated by placental hypoxia/ischemia. During normal pregnancy HIFs may respond to complex alterations in oxygen, hormones, cytokines and growth factors to regulate placental invasion, differentiation, transport and vascularization. In the ever-changing environment created during pregnancy, the HIFs appear to act as key mediators of placental development and function and thereby are likely to be important contributors to both normal and adverse pregnancy outcomes.

Human placental adenosine receptor expression is elevated in preeclampsia and hypoxia increases expression of the A2A receptor

Placental hypoxia as a result of impaired trophoblast invasion is suggested to be involved in the pathophysiology of preeclampsia. Hypoxia is a potent stimulus for the release of adenosine, and the actions of adenosine are mediated through four adenosine receptors, A(1), A(2A), A(2B) and A(3). We investigated the presence, distribution and expression of adenosine receptor subtypes in the human placenta, the expression of the adenosine receptors in placentas from pregnancies complicated by preeclampsia, small for gestational age (SGA) infants and uncomplicated pregnancies, and the effect of hypoxia on placental adenosine receptor expression. Immunofluorescent microscopy localized A(1), A(2A), A(2B) and A(3) adenosine receptors to the syncytiotrophoblast, endothelial cells and myofibroblasts within the human placenta. Adenosine receptor protein and message expression levels were significantly higher in placentas from preeclamptic pregnancies with or without SGA infants, but not different in pregnancies with SGA infants alone. In vitro exposure of placental villous explants to hypoxia (2% oxygen) increased the expression of A(2A) adenosine receptor 50%. These data indicate that all four known adenosine receptors are expressed in the human placenta and adenosine receptor expression is significantly higher in pregnancies complicated by preeclampsia. These data are consistent with the hypothesis that differences in placental adenosine receptors may contribute to alterations in placental function in preeclampsia.

Leptin affects system A amino acid transport activity in the human placenta: evidence for STAT3 dependent mechanisms

BACKGROUND

Amino acids are important nutrients during fetal development, and the activity of placental amino acid transporters is crucial in the regulation of fetal growth. Leptin, an adipocyte- and placenta-derived hormone, has been proposed to act as a peripheral signal in reproduction in humans. Leptin is elevated during pregnancy and elevated further in pathologic pregnancies such as preeclampsia. However, the role of leptin in placental function has not been fully elucidated. We hypothesize that leptin plays a role in the regulation of placental amino acid transport by activation of the JAK-STAT pathway.

METHODS

Placental amino acid transport, specifically system A transport was studied in placental villous fragments using the amino acid analog, methylaminoisobutyric acid (MeAIB). Specific inhibitors of the JAK-STAT signal transduction pathway were used to further elucidate their role in leptin-mediated effects on amino acid transport activity. Western blotting was performed to identify STAT3 phosphorylation as a measure of leptin receptor activation.

RESULTS

Leptin significantly increased system A amino acid transporter activity by 22-42% after 1h of incubation. Leptin activated JAK-STAT signaling pathway as evidenced by STAT3 phosphorylation, and inhibition of STAT3 or JAK2 resulted in 36-45% reduction in system A amino acid transporter activity. Furthermore, blocking endogenously produced leptin also decreased system A transport by 45% comparable to STAT3 inhibition.

CONCLUSIONS

These data demonstrate that leptin stimulates system A by JAK-STAT dependent pathway in placental villous fragments. Our findings support the autocrine/paracrine role of leptin in regulating amino acid transport in the human placenta.

Altered global gene expression in first trimester placentas of women destined to develop preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-specific disorder that remains a leading cause of maternal, fetal and neonatal morbidity and mortality, and is associated with risk for future cardiovascular disease. There are no reliable predictors, specific preventative measures or treatments other than delivery. A widely held view is that the antecedents of preeclampsia lie with impaired placentation in early pregnancy. Accordingly, we hypothesized dysregulation of global gene expression in first trimester placentas of women who later manifested preeclampsia.

METHODS

Surplus chorionic villus sampling (CVS) tissues were collected at 10-12 weeks gestation in 160 patients with singleton fetuses. Four patients developed preeclampsia, and their banked CVS specimens were matched to 8 control samples from patients with unaffected pregnancies. Affymetrix HG-U133 Plus 2.0 GeneChips were utilized for microarray analysis. Naïve Bayes prediction modeling and pathway analysis were conducted. qRT-PCR examined three of the dysregulated genes.

RESULTS

Thirty-six differentially expressed genes were identified in the preeclampsia placentas. qRT-PCR verified the microarray analysis. Thirty-one genes were down-regulated. Many were related to inflammation/immunoregulation and cell motility. Decidual gene dysregulation was prominent. No evidence was found for alterations in hypoxia and oxidative stress regulated genes.

CONCLUSIONS

To our knowledge, this is the first study to show dysregulation of gene expression in the early placentas of women approximately 6 months before developing preeclampsia, thereby reinforcing a placental origin of the disorder. We hypothesize that placentation in preeclampsia is compromised in the first trimester by maternal and fetal immune dysregulation, abnormal decidualization, or both, thereby impairing trophoblast invasion. Several of the genes provide potential targets for the development of clinical biomarkers in maternal blood during the first trimester. Supplementary materials are available for this article via the publisher's online edition.

Increased myeloperoxidase in the placenta and circulation of women with preeclampsia

Myeloperoxidase (MPO) is a hemoprotein normally released from activated monocytes and neutrophils. Traditionally viewed as a microbicidal enzyme, MPO also induces low-density lipoprotein oxidation, activates metalloproteinases, and oxidatively consumes endothelium-derived NO. The elevated plasma MPO level is a risk factor for myocardial events in patients with coronary artery disease. Patients with preeclampsia display evidence of the inflammation and endothelial dysfunction associated with oxidative stress in the circulation, vasculature, and placenta. We hypothesized that MPO levels in the circulation and placental extracts from women with preeclampsia would be greater than levels in women with normal pregnancies. Placental extracts were prepared from placental villous biopsies from preeclamptic (n=27) and control (n=43) placentas. EDTA plasma samples were obtained from gestationally age-matched preeclamptic and control normal pregnancies. MPO concentrations were measured by ELISA. Immunohistochemistry was used to determine MPO localization in the placenta. MPO levels in placental extracts from women with preeclampsia were significantly higher than the levels in normal control subjects (546+/-62 versus 347+/-32 ng/mL; P=0.025). MPO was found in the floating villi and basal plate of placentas with a greater staining in the basal plates from preeclampsia placentas compared with normal pregnancies. Plasma MPO levels were 3-fold higher in patients with preeclampsia compared with normal control subjects (36.6+/-7.6 versus 11.0+/-3.1 ng/mL; P=0.003). In conclusion, MPO levels are significantly increased in the circulation and placenta of women with preeclampsia. We speculate that MPO may contribute to the oxidative damage reported in the endothelium and placenta of women with preeclampsia.

Circulating and placental endoglin concentrations in pregnancies complicated by intrauterine growth restriction and preeclampsia

Inadequate trophoblast invasion and spiral artery remodeling leading to poor placental perfusion and hypoxia are believed to underlie preeclampsia (PE) and intrauterine growth restriction (IUGR). Recent studies implicate increased circulating endoglin as a contributor to the pathogenesis of PE. The objective of this study was to determine whether placental and circulating endoglin concentrations are altered in pregnancies complicated by intrauterine growth restricted (IUGR) infants and to address the role of hypoxia on the regulation of placental endoglin. We analyzed 10 placentas each from normal pregnant (NP), PE, and IUGR subjects. Endoglin levels were 2.5-fold higher in preeclamptic placentas compared to NP (15.4+/-2.6 versus 5.7+/-1.0, p<0.01). In contrast, endoglin levels were similar in NP and IUGR placentas (5.7+/-1.0 vs 5.9+/-1.1, p=NS). Placentas from pregnancies with both PE and IUGR exhibited endoglin levels comparable to the PE group and significantly different from normotensive pregnancies with and without IUGR pregnancies (mean 14.9+/-4.0, n=9, p=0.013). Soluble endoglin concentrations in maternal plasma were comparable in NP and IUGR, but higher in women with PE (n=10 per group, p<0.05). Despite a 2-fold increase in hypoxia inducible factor, HIF-1alpha, we did not observe endoglin upregulation in NP, PE, or IUGR placental villous explants exposed to hypoxia (2% oxygen). In contrast to PE, placental or circulating endoglin is not increased in normotensive women delivering small, asymmetrically grown (IUGR) infants at term. The placentas of women with IUGR appear to be fundamentally different from PE women with respect to endoglin, despite the proposed common pathology of deficient trophoblast invasion/spiral artery remodeling and poor placental perfusion.

Preeclampsia--a pressing problem: an executive summary of a National Institute of Child Health and Human Development workshop

On September 21 and 22, 2006, the National Institute of Child Health and Human Development of the National Institutes of Health sponsored a 2-day workshop titled "Preeclampsia--A Pressing Problem." The purpose of the workshop was to bring together leaders in the field to present and discuss their diverse research areas, which ranged from basic science to clinical trials and management, and to identify scientific gaps. This article is a summary of the proceedings of that workshop. Although much progress is being made in understanding the underpinnings of preeclampsia, a number of research gaps are identified that, if filled, would hasten progress in the field. It is the overall consensus that preeclampsia is a multifactorial disease whose pathogenesis is not solely vascular, genetic, immunologic, or environmental but a complex combination of factors. In addition, a number of specific scientific gaps are identified including insufficient multidisciplinary and collaborative research, clinical trials and studies of patient management, and a lack of in-depth mechanistic research. The research community needs to focus on these gaps to better understand the disease, with the ultimate goal of preventing the disorder.