Preeclampsia-like symptoms induced in mice by fetoplacental expression of STOX1 are reversed by aspirin treatment

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

Targeting STOX1 in the therapy of preeclampsia

INTRODUCTION

Preeclampsia is a major pregnancy disease, explained partly by genetic predispositions. STOX1, a transcription factor discovered in 2005, was the first gene directly associated with genetic forms of the disease. Alterations of STOX1 expression as well as STOX1 variants have also been associated to Alzheimer's disease. These observations make of this gene a putative therapeutic target. Area covered: Two major isoforms (STOX1A and STOX1B) are encoded by the gene and are theoretically able to compete for the same binding site, while only the most complete (STOX1A) is supposed to be able to activate gene expression. This makes the ratio between STOX1A and STOX1B as well as their position inside the cell (nucleus or cytoplasm) crucial to understand how STOX1 functions. STOX1 appears to have multiple gene targets, especially in pathways connected to inflammation, oxidative stress, and cell cycle. Expert opinion: STOX1-directed therapies, could be directed either towards its targets (genes or pathways), or directly at STOX1. For this the addressing of STOX1 to various cell compartments could theoretically be modified; also it could be possible of altering the balance between the two isoforms, through selectively inhibiting one of them, possibly improving the outcomes in severe preeclampsia.

Noncoding RNA-regulated gain-of-function of STOX2 in Finnish pre-eclamptic families

The familial forms of early onset pre-eclampsia and related syndromes (HELLP) present with hypertension and proteinuria in the mother and growth restriction of the fetus. Genetically, these clinically similar entities are caused by different founder-dependent, placentally-expressed paralogous genes. All susceptibility genes (STOX1, lincHELLP, INO80B) identified so far are master control genes that regulate an essential trophoblast differentiation pathway, but act at different entry points. Many genes remain to be identified. Here we demonstrate that a long non-coding RNA (lncRNA) within intron 3 of the STOX2 gene on 4q35.1 acts as a permissive cis-acting regulator of alternative splicing of STOX2. When this lncRNA is mutated or absent, an alternative exon (3B) of STOX2 is included. This introduces a stop codon resulting in the deletion of a highly conserved domain of 64 amino acids in the C-terminal of the STOX2 protein. A mutation present within a regulatory region within intron 1 of STOX2 has the same effect after blocking with CRISPR technology: transcripts with exon 3B are upregulated. This proces appears related to transcriptional control by a chromatin-splicing adaptor complex as described for FGFR2. For STOX2, CHD5, coding for a chromodomain helicase DNA binding protein, qualifies as the chromatin modifier in this process.

Prediction and prevention of hypertensive disorders of pregnancy

The most common classifications of hypertensive disorders of pregnancy consist of chronic hypertension, gestational hypertension, preeclampsia (PE) and superimposed PE. A common final pathophysiology of PE is endothelial dysfunction. The most successful translational research model for explaining the cause-effect relationship in the genesis of PE is the angiogenic/angiostatic balance theory, involving soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF) and soluble endoglin (sEng). In a systematic review of articles on the prediction of early-onset PE using angiogenesis-related factors, we revealed that the prediction of early-onset PE in the first trimester is clinically possible, but the prediction of early-onset PE in the early third trimester might be ideal. In addition, an onset threshold or a serial approach appeared to be clinically useful for predicting the imminent onset of PE, with onset at <4 weeks after blood sampling in the second and early third trimesters, because the positive likelihood ratio was >10 and the positive predictive value was >20%. The National Institute for Health and Care Excellence guidelines state that the Triage PlGF testing and Elecsys immunoassay for the sFlt-1/PlGF ratio could help to exclude PE in women with suspected PE at 20-34 weeks of gestation. Until now, we have not found any effective therapies to prevent PE. However, low-dose aspirin treatment starting at ⩽16 weeks of gestation might be associated with a marked reduction in PE. In addition, early statin treatment might prevent the occurrence of PE. Currently, a clinical trial using pravastatin for the prevention of PE is ongoing.

Quantification of Gestational Changes in the Uteroplacental Vascular Tree Reveals Vessel Specific Hemodynamic Roles During Pregnancy in Mice

The purpose of this study was to establish the time course and hemodynamic significance of de novo formed and enlarged uteroplacental arteries during pregnancy. Using x-ray microcomputed tomography (n = 4–7 placentas from 2–4 dams/gestational group), uteroplacental arterial vascular dimensions were measured at individual implantation sites. Dimensions and topology were used to compute total and vessel-specific resistances and cross-sectional areas. Diameter enlargement of the uterine artery (+55% by Embryonic Day 5.5 [E5.5]) and preplacental radial arteries (+30% by E8.5) was significant only in early gestation. Formation of spiral arteries (E9.5–E11.5), maternal canals, and canal branches (E11.5–E13.5) during midgestation was followed by enlargement of these vessels such that, from E9.5 to E17.5 (near term), spiral artery resistance dropped 9-fold, and canal resistance became negligible. A 12-fold increase in terminal vessel cross-sectional area was nearly sufficient to offset known increases in flow so that blood velocity entering the exchange region was predicted to increase by only 2-fold. The calculated 47% decrease in total resistance downstream of the uterine artery, determined from vascular geometry, was in accord with prior uterine blood flow data in vivo and was due to enlarging spiral artery diameters. Interestingly, radial artery resistance was unchanged after E9.5 so that radial arteries accounted for 91% of resistance and pressure drop in the uteroplacental arterial network by E17.5. These findings led us to propose functional roles for the three morphologically defined vessel types: radial arteries to reduce pressure, spiral artery enlargement to increase flow with gestation, and maternal canal elaboration and enlargement to maintain low exit velocities into the exchange region.

Mechanisms of Endothelial Dysfunction in Hypertensive Pregnancy and Preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and could lead to maternal and fetal morbidity and mortality. Although the causative factors and pathophysiological mechanisms are unclear, endothelial dysfunction is a major hallmark of preeclampsia. Clinical tests and experimental research have suggested that generalized endotheliosis in the systemic, renal, cerebral, and hepatic circulation could decrease endothelium-derived vasodilators such as nitric oxide, prostacyclin, and hyperpolarization factor and increase vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction, hypertension, and other manifestation of preeclampsia. In search for the upstream mechanisms that could cause endothelial dysfunction, certain genetic, demographic, and environmental risk factors have been suggested to cause abnormal expression of uteroplacental integrins, cytokines, and matrix metalloproteinases, leading to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate spiral arteries remodeling, reduced uterine perfusion pressure (RUPP), and placental ischemia/hypoxia. RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic factors vascular endothelial growth factor and placental growth factor, or stimulate the release of other circulating bioactive factors such as inflammatory cytokines, hypoxia-inducible factor-1, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could then target endothelial cells and cause generalized endothelial dysfunction. Therapeutic options are currently limited, but understanding the factors involved in endothelial dysfunction could help design new approaches for prediction and management of preeclampsia.

Preeclampsia, of mice and women

Preeclampsia (PE) is a devastating disorder of pregnancy that affects up to 8% of pregnant women in the United States. The diagnosis of PE is made by the presentation of new-onset hypertension, ≥140 mmHg systolic blood pressure (BP) or ≥90 mmHg diastolic BP, and either proteinuria or another accompanying sign/symptom, such as renal insufficiency, thrombocytopenia, hepatic dysfunction, pulmonary edema, or cerebral/visual. These signs can occur suddenly and without warning. PE that presents before 34 wk of gestation is considered early onset and carries a greater risk for perinatal morbidity/mortality than late-onset PE that occurs at or after 34 wk of gestation. At this time there is no cure for PE, and the only effective treatment is delivery of the baby and placenta. If allowed to progress to eclampsia (PE with neurologic involvement), seizures will occur and possibly death through stroke. PE also carries the risk of significant fetal and neonatal morbidity/mortality in addition to long-term health risks for mother and child. Despite significant research efforts to accurately predict, diagnose, and treat PE, a cure eludes us. Elucidating the pathophysiological mechanisms that can cause PE will aid in our ability to accurately prevent, manage, and treat PE to avoid maternal and fetal losses. Intense research efforts are focused on PE, and the mouse has proven to be a useful animal model for investigating molecular mechanisms that may hold the key to unraveling the mysteries of PE in women.

Sustained Endocrine Gland-Derived Vascular Endothelial Growth Factor Levels Beyond the First Trimester of Pregnancy Display Phenotypic and Functional Changes Associated With the Pathogenesis of Pregnancy-Induced Hypertension

Pregnancy-induced hypertension diseases are classified as gestational hypertension, preeclampsia, or eclampsia. The mechanisms of their development and prediction are still to be discovered. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an angiogenic factor secreted by the placenta during the first trimester of human pregnancy that was shown to control trophoblast invasion, to be upregulated by hypoxia, and to be abnormally elevated in pathological pregnancies complicated with preeclampsia and intrauterine growth restriction. These findings suggested that sustaining EG-VEGF levels beyond the first trimester of pregnancy may contribute to pregnancy-induced hypertension. To test this hypothesis, osmotic minipumps delivering EG-VEGF were implanted subcutaneously into gravid OF1 (Oncins France 1) mice on day 11.5 post coitus, which is equivalent to the end of the first trimester of human pregnancy. Mice were euthanized at 15.5 and 18.5 days post coitus to assess (1) litter size, placental, and fetal weights; (2) placental histology and function; (3) maternal blood pressure; (4) renal histology and function; and (5) circulating soluble fms-like tyrosine kinase 1 and soluble endoglin. Increased EG-VEGF levels caused significant defects in placental organization and function. Both increased hypoxia and decreased trophoblast invasion were observed. Treated mice had elevated circulating soluble fms-like tyrosine kinase 1 and soluble endoglin and developed gestational hypertension with dysregulated maternal kidney function. EG-VEGF effect on the kidney function was secondary to its effects on the placenta as similarly treated male mice had normal kidney functions. Altogether, these data provide a strong evidence to confirm that sustained EG-VEGF beyond the first trimester of pregnancy contributes to the development of pregnancy-induced hypertension.

Tumor-homing peptides as tools for targeted delivery of payloads to the placenta

The availability of therapeutics to treat pregnancy complications is severely lacking mainly because of the risk of causing harm to the fetus. As enhancement of placental growth and function can alleviate maternal symptoms and improve fetal growth in animal models, we have developed a method for targeted delivery of payloads to the placenta. We show that the tumor-homing peptide sequences CGKRK and iRGD bind selectively to the placental surface of humans and mice and do not interfere with normal development. Peptide-coated nanoparticles intravenously injected into pregnant mice accumulated within the mouse placenta, whereas control nanoparticles exhibited reduced binding and/or fetal transfer. We used targeted liposomes to efficiently deliver cargoes of carboxyfluorescein and insulin-like growth factor 2 to the mouse placenta; the latter significantly increased mean placental weight when administered to healthy animals and significantly improved fetal weight distribution in a well-characterized model of fetal growth restriction. These data provide proof of principle for targeted delivery of drugs to the placenta and provide a novel platform for the development of placenta-specific therapeutics.

Hypoxia-inducible miR-210 contributes to preeclampsia via targeting thrombospondin type I domain containing 7A

Preeclampsia, a relatively common pregnancy disorder, is a major contributor to maternal mortality and morbidity worldwide. An elevation in microRNA-210 (miR-210) expression in the placenta has been reported to be associated with preeclampsia. Our bioinformatic analysis showed that thrombospondin type I domain containing 7A (THSD7A) is a predicted target for miR-210. The aim of this study was to determine whether miR-210 is involved in preeclampsia through its targeting of THSD7A in human placental trophoblasts. In preeclamptic placental tissues, THSD7A levels were significantly downregulated, and were inversely correlated with the levels of miR-210. THSD7A was validated as a direct target of miR-210 using quantitative real time PCR (qRT-PCR), Western blotting, and dual luciferase assays in HTR8/SVneo cells. Transwell insert invasion assays showed that THSD7A mediated the invasion-inhibitory effect of miR-210 in HTR8/SVneo cells. Interestingly, hypoxia markedly increased miR-210 expression while suppressing THSD7A expression in a time-dependent manner in HTR8/SVneo cells. This study provides novel data on the function of THSD7A in human placental cells, and extends our knowledge of how miR-210 is involved in the development of the preeclampsia.

Endothelial cell dysfunction and cardiac hypertrophy in the STOX1 model of preeclampsia

Preeclampsia is a disease of pregnancy involving systemic endothelial dysfunction. However, cardiovascular consequences of preeclampsia are difficult to analyze in humans. The objective of the present study is to evaluate the cardiovascular dysfunction induced by preeclampsia by examining the endothelium of mice suffering of severe preeclampsia induced by STOX1 overexpression. Using Next Generation Sequencing on endothelial cells of mice carrying either transgenic or control embryos, we discovered significant alterations of gene networks involved in inflammation, cell cycle, and cardiac hypertrophy. In addition, the heart of the preeclamptic mice revealed cardiac hypertrophy associated with histological anomalies. Bioinformatics comparison of the networks of modified genes in the endothelial cells of the preeclamptic mice and HUVECs exposed to plasma from preeclamptic women identified striking similarities. The cardiovascular alterations in the pregnant mice are comparable to those endured by the cardiovascular system of preeclamptic women. The STOX1 mice could help to better understand the endothelial dysfunction in the context of preeclampsia, and guide the search for efficient therapies able to protect the maternal endothelium during the disease and its aftermath.

Unravelling the theories of pre-eclampsia: are the protective pathways the new paradigm?

Pre-eclampsia is a vascular disorder of pregnancy where anti-angiogenic factors, systemic inflammation and oxidative stress predominate, but none can claim to cause pre-eclampsia. This review provides an alternative to the ‘two-stage model’ of pre-eclampsia in which abnormal spiral arteries modification leads to placental hypoxia, oxidative stress and aberrant maternal systemic inflammation. Very high maternal soluble fms-like tyrosine kinase-1 (sFlt-1 also known as sVEGFR) and very low placenta growth factor (PlGF) are unique to pre-eclampsia; however, abnormal spiral arteries and excessive inflammation are also prevalent in other placental disorders. Metaphorically speaking, pregnancy can be viewed as a car with an accelerator and brakes, where inflammation, oxidative stress and an imbalance in the angiogenic milieu act as the ‘accelerator’. The ‘braking system’ includes the protective pathways of haem oxygenase 1 (also referred as Hmox1 or HO-1) and cystathionine-γ-lyase (also known as CSE or Cth), which generate carbon monoxide (CO) and hydrogen sulphide (H₂S) respectively. The failure in these pathways (brakes) results in the pregnancy going out of control and the system crashing. Put simply, pre-eclampsia is an accelerator–brake defect disorder. CO and H₂S hold great promise because of their unique ability to suppress the anti-angiogenic factors sFlt-1 and soluble endoglin as well as to promote PlGF and endothelial NOS activity. The key to finding a cure lies in the identification of cheap, safe and effective drugs that induce the braking system to keep the pregnancy vehicle on track past the finishing line.

Inventory of Novel Animal Models Addressing Etiology of Preeclampsia in the Development of New Therapeutic/Intervention Opportunities

Preeclampsia is a pregnancy-related disease afflicting 3-7% of pregnancies worldwide and leads to maternal and infant morbidity and mortality. The disease is of placental origin and is commonly described as a disease of two stages. A variety of preeclampsia animal models have been proposed, but all of them have limitations in fully recapitulating the human disease. Based on the research question at hand, different or multiple models might be suitable. Multiple animal models in combination with in vitro or ex vivo studies on human placenta together offer a synergistic platform to further our understanding of the etiology of preeclampsia and potential therapeutic interventions. The described animal models of preeclampsia divide into four categories (i) spontaneous, (ii) surgically induced, (iii) pharmacologically/substance induced, and (iv) transgenic. This review aims at providing an inventory of novel models addressing etiology of the disease and or therapeutic/intervention opportunities.

Genetic, immune and vasoactive factors in the vascular dysfunction associated with hypertension in pregnancy

INTRODUCTION

Preeclampsia (PE) is a major complication of pregnancy that could lead to maternal and fetal morbidity and mortality. The pathophysiological mechanisms of PE are not completely understood, but recent research has begun to unravel some of the potential mechanisms.

AREAS COVERED

Genetic polymorphisms and altered maternal immune response may cause impaired remodeling of the spiral arteries; a potential early defect in PE. Inadequate invasion of cytotrophoblasts into the decidua leads to reduced uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia. Placental ischemia causes the release of biologically active factors such as anti-angiogenic factors, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and angiotensin II receptor autoantibodies. These vasoactive factors could cause systemic vascular endotheliosis and consequent increase in vascular resistance and blood pressure, glomerular endotheliosis causing proteinuria, cerebrovascular endotheliosis causing cerebral edema, seizures and visual disturbances, and hepatic endotheliosis, which may contribute to the manifestations of HELLP syndrome. PE-associated vascular endotheliosis causes a decrease in vasodilator mediators such as nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor, an increase in vasoconstrictors such as endothelin-1, angiotensin II and thromboxane A2, and enhanced mechanisms of vascular smooth muscle contraction such as intracellular Ca(2+), protein kinase C and Rho-kinase. Changes in matrix metalloproteinase activity and extracellular matrix cause vascular remodeling and further vasoconstriction.

EXPERT OPINION

Some of the genetic, immune and vasoactive factors involved in vascular endotheliosis could be used as biomarkers for early detection, and as potential targets for prevention and treatment of PE.

From Pre-Clinical Studies to Clinical Trials: Generation of Novel Therapies for Pregnancy Complications

Complications of pregnancy represent a significant disease burden, with both immediate and lasting consequences for mother and baby. Two key pregnancy complications, fetal growth restriction (FGR) and preeclampsia (PE), together affect around 10%–15% of all pregnancies worldwide. Despite this high incidence, there are currently no therapies available to treat these pregnancy disorders. Early delivery remains the only intervention to reduce the risk of severe maternal complications and/or stillbirth of the baby; however early delivery itself is associated with increased risk of neonatal mortality and morbidity. As such, there is a pressing need to develop new and effective treatments that can prevent or treat FGR and PE. Animal models have been essential in identifying and screening potential new therapies in this field. In this review, we address recent progress that has been made in developing therapeutic strategies for pregnancy disorders, some of which are now entering clinical trials.

The potential impact of the fetal genotype on maternal blood pressure during pregnancy

The heritability of pregnancy-induced hypertension (encompassing both gestational hypertension and preeclampsia) is around 0.47, suggesting that there is a genetic component to its development. However, the maternal genetic risk variants discovered so far only account for a small proportion of the heritability. Other genetic variants that may affect maternal blood pressure in pregnancy arise from the fetal genome, for example wild-type pregnant mice carrying offspring with Cdkn1c or Stox1 disrupted develop hypertension and proteinuria. In humans, there is a higher risk for preeclampsia in women carrying fetuses with Beckwith-Wiedemann syndrome (including those fetuses with CDKN1C mutations) and a lower risk for women carrying babies with trisomy 21. Other risk may be associated with imprinted fetal growth genes and genes that are highly expressed in the placenta such as GCM1. This article reviews the current state of knowledge linking the fetal genotype with maternal blood pressure in pregnancy.

Translational value of animal models of kidney failure

Acute kidney injury (AKI) and chronic kidney disease (CKD) are associated with decreased renal function and increased mortality risk, while the therapeutic armamentarium is unsatisfactory. The availability of adequate animal models may speed up the discovery of biomarkers for disease staging and therapy individualization as well as design and testing of novel therapeutic strategies. Some longstanding animal models have failed to result in therapeutic advances in the clinical setting, such as kidney ischemia-reperfusion injury and diabetic nephropathy models. In this regard, most models for diabetic nephropathy are unsatisfactory in that they do not evolve to renal failure. Satisfactory models for additional nephropathies are needed. These include anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, IgA nephropathy, anti-phospholipase-A2-receptor (PLA2R) membranous nephropathy and Fabry nephropathy. However, recent novel models hold promise for clinical translation. Thus, the AKI to CKD translation has been modeled, in some cases with toxins of interest for human CKD such as aristolochic acid. Genetically modified mice provide models for Alport syndrome evolving to renal failure that have resulted in clinical recommendations, polycystic kidney disease models that have provided clues for the development of tolvaptan, that was recently approved for the human disease in Japan; and animal models also contributed to target C5 with eculizumab in hemolytic uremic syndrome. Some ongoing trials explore novel concepts derived from models, such TWEAK targeting as tissue protection for lupus nephritis. We now review animal models reproducing diverse, genetic and acquired, causes of AKI and CKD evolving to kidney failure and discuss the contribution to clinical translation and prospects for the future.

Adaptive mechanisms controlling uterine spiral artery remodeling during the establishment of pregnancy

Implantation of the embryo into the uterus triggers the initiation of hemochorial placentation. The hemochorial placenta facilitates the acquisition of maternal resources required for embryo/fetal growth. Uterine spiral arteries form the nutrient supply line for the placenta and fetus. This vascular conduit undergoes gestation stage-specific remodeling directed by maternal natural killer cells and embryo-derived invasive trophoblast lineages. The placentation site, including remodeling of the uterine spiral arteries, is shaped by environmental challenges. In this review, we discuss the cellular participants controlling pregnancy-dependent uterine spiral artery remodeling and mechanisms responsible for their development and function.

Aspirin inhibits expression of sFLT1 from human cytotrophoblasts induced by hypoxia, via cyclo-oxygenase 1

INTRODUCTION

Elevated circulating soluble FLT1 (sFLT1) levels seen in preeclampsia may play a role in its development. Aspirin is recommended for prevention of preeclampsia. We hypothesized that aspirin may inhibit the production of sFlt1.

METHODS

Placentas from women with and without preeclampsia were collected. Primary cytotrophoblasts (CTBs) were cultured from normal placentas and treated with aspirin, sc-560, a COX1 inhibitor or celecoxib, a COX2 inhibitor. The expression of sFLT1, FLT1, COX1 and COX2 was studied. The effect of aspirin on sFlt1 expression was also studied in HEK293 cells and in HTR-8/SVNeo cells.

RESULTS

The expression of sFLT1 was increased in preeclamptic placentas compared to control placentas and the expression and release of sFLT1 increased in CTBs exposed to 2% O2 compared to controls. Aspirin at 3 and 12 mM concentration reduced the expression and release of sFLT1 in CTBs. Aspirin also inhibited sFlt1 expression from HTR-8/SVNeo and HEK293 cells. Sc-560, but not celecoxib, reduced sFLT1 expression and release from CTBs. Aspirin and sc-560 also reduced hypoxia-induced FLT1 mRNA expression and inhibited COX1 mRNA in CTBs.

DISCUSSION

This study confirms that sFLT1 expression is increased in preeclamptic placentas and in CTBs exposed to hypoxia. Aspirin inhibits the production sFLT1 in CTBs and in HTR-8/SVNeo. Sc-560 recapitulated the effects of aspirin on sFLT1 expression and release in CTBs suggesting that the aspirin effect may be mediated via inhibition of COX1. The study increases our understanding of the mechanisms regulating sFlt1 expression and provides a plausible explanation for the effect of aspirin to prevent preeclampsia.

Nitroso-redox balance and mitochondrial homeostasis are regulated by STOX1, a pre-eclampsia-associated gene

AIMS

Storkhead box 1 (STOX1) is a winged-helix transcription factor that is implicated in the genetic forms of a high-prevalence human gestational disease, pre-eclampsia. STOX1 overexpression confers pre-eclampsia-like transcriptomic features to trophoblastic cell lines and pre-eclampsia symptoms to pregnant mice. The aim of this work was to evaluate the impact of STOX1 on free radical equilibrium and mitochondrial function, both in vitro and in vivo.

RESULTS

Transcriptome analysis of STOX1-transgenic versus nontransgenic placentas at 16.5 days of gestation revealed alterations of mitochondria-related pathways. Placentas overexpressing STOX1 displayed altered mitochondrial mass and were severely biased toward protein nitration, indicating nitroso-redox imbalance in vivo. Trophoblast cells overexpressing STOX1 displayed an increased mitochondrial activity at 20% O2 and in hypoxia, despite reduction of the mitochondrial mass in the former. STOX1 overexpression is, therefore, associated with hyperactive mitochondria, resulting in increased free radical production. Moreover, nitric oxide (NO) production pathways were activated, resulting in peroxynitrite formation. At low oxygen pressure, STOX1 overexpression switched the free radical balance from reactive oxygen species (ROS) to reactive nitrogen species (RNS) in the placenta as well as in a trophoblast cell line.

INNOVATION

In pre-eclamptic placentas, NO interacts with ROS and generates peroxynitrite and nitrated proteins as end products. This process will deprive the maternal organism of NO, a crucial vasodilator molecule.

CONCLUSION

Our data posit STOX1 as a genetic switch in the ROS/RNS balance and suggest an explanation for elevated blood pressure in pre-eclampsia.

The prion protein family: a view from the placenta

Based on its developmental pattern of expression, early studies suggested the implication of the mammalian Prion protein PrP, a glycosylphosphatidylinositol-anchored ubiquitously expressed and evolutionary conserved glycoprotein encoded by the Prnp gene, in early embryogenesis. However, gene invalidation in several species did not result in obvious developmental abnormalities and it was only recently that it was associated in mice with intra-uterine growth retardation and placental dysfunction. A proposed explanation for this lack of easily detectable developmental-related phenotype is the existence in the genome of one or more gene (s) able to compensate for the absence of PrP. Indeed, two other members of the Prnp gene family have been recently described, Doppel and Shadoo, and the consequences of their invalidation alongside that of PrP tested in mice. No embryonic defect was observed in mice depleted for Doppel and PrP. Interestingly, the co-invalidation of PrP and Shadoo in two independent studies led to apparently conflicting observations, with no apparent consequences in one report and the observation of a developmental defect of the ectoplacental cone that leads to early embryonic lethality in the other. This short review aims at summarizing these recent, apparently conflicting data highlighting the related biological questions and associated implications in terms of animal and human health.

Advances in the pathophysiology of pre-eclampsia and related podocyte injury

Pre-eclampsia is a pregnancy-specific hypertensive disorder that may lead to serious maternal and fetal complications. It is a multisystem disease that is commonly, but not always, accompanied by proteinuria. Its cause(s) remain unknown, and delivery remains the only definitive treatment. It is increasingly recognized that many pathophysiological processes contribute to this syndrome, with different signaling pathways converging at the point of systemic endothelial dysfunction, hypertension, and proteinuria. Different animal models of pre-eclampsia have proven utility for specific aspects of pre-eclampsia research, and offer insights into pathophysiology and treatment possibilities. Therapeutic interventions that specifically target these pathways may optimize pre-eclampsia management and may improve fetal and maternal outcomes. In addition, recent findings regarding placental, endothelial, and podocyte pathophysiology in pre-eclampsia provide unique and exciting possibilities for improved diagnostic accuracy. Emerging evidence suggests that testing for urinary podocytes or their markers may facilitate the prediction and diagnosis of pre-eclampsia. In this review, we explore recent research regarding placental, endothelial, and podocyte pathophysiology. We further discuss new signaling and genetic pathways that may contribute to pre-eclampsia pathophysiology, emerging screening and diagnostic strategies, and potential targeted interventions.

(Epi)genetics of pregnancy-associated diseases

This review describes the current knowledge regarding genetics and epigenetics of pregnancy-associated diseases with placental origin. We discuss the effect on genetic linkage analyses when the fetal genotype determines the maternal phenotype. Secondly, the genes identified by genome-wide linkage studies to be associated with pre-eclampsia (ACVR2A, STOX1) and the HELLP-syndrome (LINC-HELLP) are discussed regarding their potential functions in the etiology of disease. Furthermore, susceptibility genes identified by candidate gene approaches (e.g., CORIN) are described. Next, we focus on the additional challenges that come when epigenetics also play a role in disease inheritance. We discuss the maternal transmission of the chromosome 10q22 pre-eclampsia linkage region containing the STOX1 gene and provide further evidence for the role of epigenetics in pre-eclampsia based on the cdkn1c mouse model of pre-eclampsia. Finally, we provide recommendations to unravel the genetics of pregnancy-associated diseases, specifically regarding clear definitions of patient groups and sufficient patient numbers, and the potential usefulness of (epi)genetic data in early non-invasive biomarker development.

Pathophysiology of hypertension in pre-eclampsia: a lesson in integrative physiology

Despite being one of the leading causes of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of pre-eclampsia have yet to be fully elucidated. However, it is evident that this is a complex disorder involving multiple organ systems, and by using integrative approaches, enormous progress has been made towards understanding the pathophysiology of pre-eclampsia. Growing evidence supports the concept that the placenta plays a central role in the pathogenesis of pre-eclampsia and that reduced uteroplacental perfusion, which develops as a result of abnormal cytotrophoblast invasion of spiral arterioles, triggers the cascade of events leading to the maternal disorder. Placental ischaemia leads to release of soluble placental factors, many of which are classified as anti-angiogenic or pro-inflammatory. Once these ischaemic placental factors reach the maternal circulation, they cause widespread activation and dysfunction of the maternal vascular endothelium that results in enhanced formation of endothelin-1 and superoxide, increased vascular sensitivity to angiotensin II and decreased formation of vasodilators such as nitric oxide. This review highlights these links between placental ischaemia, maternal endothelial activation and renal dysfunction in the pathogenesis of hypertension in pre-eclampsia.

Landscape of transcriptional deregulations in the preeclamptic placenta

Preeclampsia is a pregnancy disease affecting 5 to 8% of pregnant women and a leading cause of both maternal and fetal mortality and morbidity. Because of a default in the process of implantation, the placenta of preeclamptic women undergoes insufficient vascularization. This results in placental ischemia, inflammation and subsequent release of placental debris and vasoactive factors in the maternal circulation causing a systemic endothelial activation. Several microarray studies have analyzed the transcriptome of the preeclamptic placentas to identify genes which could be involved in placental dysfunction. In this study, we compared the data from publicly available microarray analyses to obtain a consensus list of modified genes. This allowed to identify consistently modified genes in the preeclamptic placenta. Of these, 67 were up-regulated and 31 down-regulated. Assuming that changes in the transcription level of co-expressed genes may result from the coordinated action of a limited number of transcription factors, we looked for over-represented putative transcription factor binding sites in the promoters of these genes. Indeed, we found that the promoters of up-regulated genes are enriched in putative binding sites for NFkB, CREB, ANRT, REEB1, SP1, and AP-2. In the promoters of down-regulated genes, the most prevalent putative binding sites are those of MZF-1, NFYA, E2F1 and MEF2A. These transcriptions factors are known to regulate specific biological pathways such as cell responses to inflammation, hypoxia, DNA damage and proliferation. We discuss here the molecular mechanisms of action of these transcription factors and how they can be related to the placental dysfunction in the context of preeclampsia.

Why preeclampsia still exists?

Preeclampsia (PE) is a deadly gestational disease affecting up to 10% of women and specific of the human species. Preeclampsia is clearly multifactorial, but the existence of a genetic basis for this disease is now clearly established by the existence of familial cases, epidemiological studies and known predisposing gene polymorphisms. PE is very common despite the fact that Darwinian pressure should have rapidly eliminated or strongly minimized the frequency of predisposing alleles. Consecutive pregnancies with the same partner decrease the risk and severity of PE. Here, we show that, due to this peculiar feature, preeclampsia predisposing-alleles can be differentially maintained according to the familial structure. Thus, we suggest that an optimal frequency of PE-predisposing alleles in human populations can be achieved as a result of a trade-off between benefits of exogamy, importance for maintaining genetic diversity and increase of the fitness owing to a stable paternal investment.