Preeclampsia, a disease of the maternal endothelium: the role of antiangiogenic factors and implications for later cardiovascular disease

Characterisation of syncytiotrophoblast vesicles in normal pregnancy and pre-eclampsia: expression of Flt-1 and endoglin

Background

The placental syncytiotrophoblast releases micro and nanovesicles (STBM), into the maternal circulation in normal pregnancy and in increased amounts in pre-eclampsia (PE), which have proinflammatory and antiangiogenic activity and are implicated in PE pathophysiology. Better characterisation of STBM is essential to understand their role in PE.

Methods and Results

STBM prepared by placental lobe dual perfusion (pSTBM) and mechanical disruption (mSTBM) were analysed by four colour flow cytometry (4CFC), nanoparticle tracking analysis (NTA) and Western blotting to determine vesicle size, purity and Flt-1 and endoglin (Eng) expression. Biological activity of STBM associated Flt-1 and endoglin was assessed by the ability of VEGF, PlGF and TGFβ to bind to mSTBM and inhibit mSTBM induced endothelial monolayer disruption. STBM content was consistently high (∼87–95%) across the different preparations. However, surface antigen intensities differed, with significantly lower placental alkaline phosphatase (P<0.05) and Eng (P<0.05) expression on mSTBM, and Flt-1 (P<0.05) expression on pSTBM. For PE placenta derived preparations, pSTBM contained lower Eng positive STBM (P<0.05) and mSTBM Eng expression was increased (P<0.05). Western blotting revealed increased Flt-1/sFlt-1 (P<0.02) and decreased placental alkaline phosphatase (P = 0.0002) content of PE placenta pSTBM. Using NTA, perfused PE placentas released significantly larger MV (P<0.001). Finally, VEGF, PlGF and TGFβ bound to mSTBM at physiologically relevant concentrations and inhibited mSTBM induced endothelial disruption (P<0.05-P<0.001).

Conclusions

This study has found differences in physical and antigenic characteristics of normal and PE placenta STBM preparations produced by placental perfusion or mechanical disruption. We have also demonstrated that large quantities of biologically active STBM associated endoglin and Flt-1/sFlt-1 could contribute to the increased circulating levels measured in PE patients and add to the perturbation of the maternal vascular endothelium, normally attributed to non-membrane bound sFlt-1 and sEndoglin.

Testosterone alters maternal vascular adaptations: role of the endothelial NO system

Sex steroid hormones estradiol and progesterone play an important role in vascular adaptations during pregnancy. However, little is known about the role of androgens. Plasma testosterone (T) levels are elevated in preeclampsia, mothers with polycystic ovary, and pregnant African American women, who have endothelial dysfunction and develop gestational hypertension. We tested whether increased T alters vascular adaptations during pregnancy and whether these alterations depend on endothelium-derived factors, such as prostacyclin, endothelium-derived hyperpolarizing factor, and NO. Pregnant Sprague Dawley rats were injected with vehicle (n=12) or T propionate [0.5 mg/Kg per day from gestation day 15-19; n=12] to increase plasma T levels 2-fold, similar to that observed in preeclampsia. Telemetric blood pressures and endothelium-dependent vascular reactivity were assessed with wire-myograph system. Phospho-endothelial NO synthase and total endothelial NO synthase were examined in mesenteric arteries. Mean arterial pressures were significantly higher starting from gestation day19 until delivery in T-treated dams. Endothelium-dependent relaxation responses to acetylcholine were significantly lower in mesenteric arteries of T-treated dams (pD(2) [-log EC(50)]=7.05±0.06; E(max)=89.4±1.89) compared with controls (pD(2)=7.38±0.04; E(max)=99.9±0.97). Further assessment of endothelial factors showed NO-mediated relaxations were blunted in T-treated mesenteric arteries (E(max)=42.26±5.95) compared with controls (E(max)=76.49±5.06); however, prostacyclin- and endothelium-derived hyperpolarizing factor-mediated relaxations were unaffected. Relaxation to sodium nitroprusside was unaffected with T-treatment. Phosphorylations of endothelial NO synthase at Ser(1177) were decreased and at Thr(495) increased in T-treated mesenteric arteries without changes in total endothelial NO synthase levels. In conclusion, increased maternal T, at concentrations relevant to abnormal clinical conditions, cause hypertension associated with blunting of NO-mediated vasodilation. T may induce the increased vascular resistance associated with pregnancy-induced hypertension.

PLAC4 is upregulated in severe early onset preeclampsia and upregulated with syncytialisation but not hypoxia

INTRODUCTION

Severe early onset preeclampsia is one of the most serious complications of pregnancy. Placental specific 4 (PLAC4) is very highly expressed in placenta relative to all other tissues. Recently in a biomarker screening study, we found PLAC4 mRNA was significantly upregulated in maternal whole blood and placenta obtained from cases of severe preeclampsia. Intriguingly however, very little is known about its expression or functional role in either normal pregnancy or pregnancies complicated by preeclampsia.

METHODS

The objective of this study was to characterize the protein expression and localization of PLAC4 in severe early onset preeclamptic placenta. Given so little of the biology of PLAC4 is known, we also examined whether the expression of PLAC4 alters with syncytialisation or placental hypoxia.

RESULTS

We found PLAC4 protein expression was significantly (p < 0.05) upregulated in severe early onset preeclamptic placentas (n = 24) compared to gestationally matched preterm controls (n = 12). PLAC4 protein was specifically localized to the syncytiotrophoblast of preterm, preeclamptic and term placentas. Functional analysis of PLAC4 mRNA and protein expression revealed a significant (p < 0.05) increase with syncytialisation of BeWo cells. However, exposure of either syncytialised BeWo cells or primary term placental explants to hypoxia (1% oxygen) did not alter the expression of either PLAC4 mRNA or protein.

CONCLUSION

In conclusion, we have found PLAC4 is significantly upregulated in association with severe preterm preeclampsia. Furthermore, it is upregulated with syncytialisation, but not hypoxia. It is possible PLAC4 may have a role in the pathogenesis of preeclampsia, and its biology merits further investigation.

Delayed visual recovery in pregnancy-associated thrombotic thrombocytopenic purpura with bilateral serous retinal detachment

BACKGROUND

To present a pregnancy-associated thrombotic thrombocytopenic purpura (TTP) patient with bilateral serous retinal detachment (SRD).

METHODS

Case report.

RESULTS

A 28-year-old nulliparous woman with 31 weeks gestation was presented to the local hospital with preeclampsia, hemolytic anemia, thrombocytopenia and bilateral blurry vision. Funduscopic examination showed bilateral macular SRD. Within the first month after delivery of a live female baby via cesarean section (at 32 weeks gestation), the patient experienced a recurrent course of hemolytic anemia and thrombocytopenia, and was then transferred to our hospital. On admission, her best corrected visual acuity (BCVA) was 0.1 OU; optical coherence tomography (OCT) confirmed the presence of bilateral macular SRD; electroretinography (ERG) examination showed diminished rod responses with reduced a and b waves in cone and mixed rod-cone responses. She was ultimately diagnosed with TTP and was treated systemically with fresh frozen plasma, rituximab, prednisone and cyclophosphamide. Despite persistent visual disturbances, she was discharged 1 month after admission with stabilization of systemic manifestations. At her first follow-up visit 6 months after discharge, surprisingly, her BCVA had improved to 1.0 OU; fundus examination and OCT confirmed the complete resolution of bilateral macular SRD and ERG revealed subnormal (right) and normal (left) electrophysiological responses. We believe that in this case, the clinical context (pregnancy) in which TTP developed, the unreported ERG characteristics and the unexpected delayed visual recovery are worth reporting.

CONCLUSIONS

TTP should be considered as a potential differential diagnosis in patients with pregnancy-associated SRD. Appropriate systemic treatment might be mandatory for visual recovery.

Pregnancy-onset habitual snoring, gestational hypertension, and preeclampsia: prospective cohort study

OBJECTIVE

This study aimed to prospectively examine the impact of chronic vs pregnancy-onset habitual snoring on gestational hypertension, preeclampsia, and gestational diabetes.

STUDY DESIGN

Third-trimester pregnant women were recruited from a large, tertiary medical center from March 2007 through December 2010 and screened for the presence and duration of habitual snoring, as a known marker for sleep-disordered breathing. Clinical diagnoses of gestational hypertension, preeclampsia, and gestational diabetes were obtained.

RESULTS

Of 1719 pregnant women, 34% reported snoring, with 25% reporting pregnancy-onset snoring. After adjusting for confounders, pregnancy-onset, but not chronic, snoring was independently associated with gestational hypertension (odds ratio, 2.36; 95% confidence interval, 1.48-3.77; P < .001) and preeclampsia (odds ratio, 1.59; 95% confidence interval, 1.06-2.37; P = .024) but not gestational diabetes.

CONCLUSION

New-onset snoring during pregnancy is a strong risk factor for gestational hypertension and preeclampsia. In view of the significant morbidity and health care costs associated with hypertensive diseases of pregnancy, simple screening of pregnant women may have clinical utility.

Neutrophil NETs in reproduction: from infertility to preeclampsia and the possibility of fetal loss

The intention of this review is to provide an overview of the potential role of neutrophil extracellular traps (NETs) in mammalian reproduction. Neutrophil NETs appear to be involved in various stages of the reproductive cycle, starting with fertility and possibly ending with fetal loss. The first suggestion that NETs may play a role in pregnancy-related disorders was in preeclampsia, where vast numbers were detected in the intervillous space of affected placentae. The induction of NETosis involved an auto-inflammatory component, mediated by the increased release of placental micro-debris in preeclampsia. This report was the first indicating that NETs may be associated with a human pathology not involving infection. Subsequently, NETs have since then been implicated in bovine or equine infertility, in that semen may become entrapped in the female reproductive tract during their passage to the oocyte. In this instance interesting species-specific differences are apparent, in that equine sperm evade entrapment via expression of a DNAse-like molecule, whereas highly motile bovine sperm, once free from seminal plasma (SP) that promotes interaction with neutrophils, appear impervious to NETs entrapment. Although still in the realm of speculation it is plausible that NETs may be involved in recurrent fetal loss mediated by anti-phospholipid antibodies, or perhaps even in fetal abortion triggered by infections with microorganisms such as L. monocytogenes or B. abortus.

miR-16 inhibits the proliferation and angiogenesis-regulating potential of mesenchymal stem cells in severe pre-eclampsia

Pre-eclampsia is thought to be a systemic disease of maternal endothelial cell dysfunctions. miRNAs regulate various basic biological functions in cells, including stem cells. Mesenchymal stem cells exist in almost all tissues and are the key cellular source for tissue repair and regeneration. Our aims are to investigate whether miRNAs regulate MSCs in fetal-maternal interfaces to influence the pathogenesis of pre-eclampsia. The differential expression of miRNAs in decidua-derived mesenchymal stem cells of all patients with severe pre-eclampsia (n = 20) and normal groups (n = 20) was first screened by microarray analysis and validated by quantitative real-time PCR analysis. The integrated bioinformatics analysis showed that miR-16 showed the highest number of connections in the miRNA GO network and the miRNA gene network. Moreover, over-expressed miR-16 inhibited the proliferation and migration of decidua-derived mesenchymal stem cells and induced cell-cycle arrest by targeting cyclin E1. Interestingly, over-expression of miR-16 by decidua-derived mesenchymal stem cells reduced the ability of human umbilical vein endothelial cells to form blood vessels and reduced the migration of trophoblast cells. Furthermore, decidua-derived mesenchymal stem cell-expressed endothelial growth factor VEGF-A was involved in migration of trophoblast cells and human umbilical vein endothelial cells as well as tube and network formation. Importantly, the levels of cyclin E1 and VEGF-A were negatively correlated with the level of miR-16 expression in decidua-derived mesenchymal stem cells from the patients with severe pre-eclampsia. Together, these data suggest that the alteration of miR-16 expression in decidua-derived mesenchymal stem cells may be involved in the development of pre-eclampsia.

Cytochrome P450 subfamily 2J polypeptide 2 expression and circulating epoxyeicosatrienoic metabolites in preeclampsia

BACKGROUND

Preeclampsia is a multisystem disorder of pregnancy, originating in the placenta. Cytochrome P450 (CYP)-dependent eicosanoids regulate vascular function, inflammation, and angiogenesis, which are mechanistically important in preeclampsia.

METHODS AND RESULTS

We performed microarray screening of placenta and decidua (maternal placenta) from 25 preeclamptic women and 23 control subjects. The CYP subfamily 2J polypeptide 2 (CYP2J2) was upregulated in preeclamptic placenta and decidua. Reverse-transcription polymerase chain reaction confirmed the upregulation, and immunohistochemistry localized CYP2J2 in trophoblastic villi and deciduas at 12 weeks and term. The CYP2J2 metabolites, 5,6-epoxyeicosatrienoic acid (EET), 14,15-EET, and the corresponding dihydroxyeicosatrienoic acids, were elevated in preeclamptic women compared with controls in the latter two thirds of pregnancy and after delivery. Stimulating a trophoblast-derived cell line with the preeclampsia-associated cytokine tumor necrosis factor-α enhanced CYP2J2 gene and protein expression. In 2 independent rat models of preeclampsia, reduced uterine-perfusion rat and the transgenic angiotensin II rat, we observed elevated EET, dihydroxyeicosatrienoic acid, and preeclamptic features that were ameliorated by the CYP epoxygenase inhibitor N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MsPPOH). Uterine arterial rings of these rats also dilated in response to MsPPOH. Furthermore, 5,6-EET could be metabolized to a thromboxane analog. In a bioassay, 5,6-EET increased the beating rate of neonatal cardiomyocytes. Blocking thromboxane synthesis reversed that finding and also normalized large-conductance calcium-activated potassium channel activity.

CONCLUSIONS

Our data implicate CYP2J2 in the pathogenesis of preeclampsia and as a potential candidate for the disturbed uteroplacental remodeling, leading to hypertension and endothelial dysfunction.

Oxysterol-induced soluble endoglin release and its involvement in hypertension

BACKGROUND

Ischemia in the placenta is considered the base of the pathogenesis of preeclampsia, a pregnancy-specific syndrome in which soluble endoglin (sEng) is a prognostic marker and plays a pathogenic role. Here, we investigated the effects of hypoxia and the downstream pathways in the release of sEng.

METHODS AND RESULTS

Under hypoxic conditions, the trophoblast-like cell line JAR showed an increase in sEng parallel to an elevated formation of reactive oxygen species. Because reactive oxygen species are related to the formation of oxysterols, we assessed the effect of 22-(R)-hydroxycholesterol, a natural ligand of the liver X receptor (LXR), and the LXR synthetic agonist T0901317. Treatment of JAR cells or human placental explants with 22-(R)-hydroxycholesterol or T0901317 resulted in a clear increase in sEng that was dependent on LXR. These LXR agonists induced an increased matrix metalloproteinase-14 expression and activity and a significant reduction of its endogenous inhibitor, tissue inhibitor of metalloproteinase-3. In addition, mice treated with LXR agonists underwent an increase in the plasma sEng levels, concomitant with an increase in arterial pressure. Moreover, transgenic mice overexpressing sEng displayed high blood pressure. Finally, administration of an endoglin peptide containing the consensus matrix metalloproteinase-14 cleavage site G-L prevented the oxysterol-dependent increase in arterial pressure and sEng levels in mice.

CONCLUSIONS

These studies provide a clue to the involvement of the LXR pathway in sEng release and its pathogenic role in vascular disorders such as preeclampsia.

Plasma concentrations of soluble endoglin versus standard evaluation in patients with suspected preeclampsia

Background

The purpose of this study was to compare plasma soluble endoglin (sEng) levels with standard clinical evaluation or plasma levels of other angiogenic proteins [soluble fms-like tyrosine kinase 1 (sFlt1) and placental growth factor (PlGF)] in predicting short-term adverse maternal and perinatal outcomes in women with suspected preeclampsia presenting prior to 34 weeks.

Methods and Findings

Data from all women presenting at <34 weeks for evaluation of preeclampsia with singleton pregnancies (July 2009−October 2010) were included in this analysis and sEng levels were measured at presentation. Data was analyzed for 170 triage encounters and presented as median {25−75^th centile}. Thirty-three percent of patients (56 of 170) experienced an adverse outcome. sEng levels (ng/ml) were significantly elevated in patients who subsequently experienced adverse outcomes compared to those who did not (32.3 {18.1, 55.8} vs 4.8 {3.2, 8.6}, p<0.0001). At a 10% false positive rate, sEng had higher detection rates of adverse outcomes than the combination of highest systolic blood pressure, proteinuria and abnormal laboratory tests (80.4 {70.0, 90.8} vs 63.8 {51.4, 76.2}, respectively). Subjects in the highest quartile of sEng were more likely to deliver early compared to those in the lowest quartile (HR: 14.96 95% CI: 8.73−25.62, p<0.0001). Natural log transformed sEng correlated positively with log sFlt1 levels (r = 0.87) and inversely with log PlGF levels (r = −0.79) (p<0.0001 for both). Plasma sEng had comparable area under the curve for prediction of adverse outcomes as measurement of sFlt1/PlGF ratio (0.88 {0.81, 0.95} for sEng versus 0.89 {0.83, 0.95} for sFlt1/PlGF ratio, p = 0.74).

Conclusions

In women with suspected preeclampsia presenting prior to 34 weeks of gestation, sEng performs better than standard clinical evaluation in detecting adverse maternal and fetal outcomes occurring within two weeks of presentation. Soluble endoglin was strongly correlated with sFlt1 and PlGF levels, suggesting common pathogenic pathways leading to preeclampsia.

Endothelial endoglin is involved in inflammation: role in leukocyte adhesion and transmigration

Human endoglin is an RGD-containing transmembrane glycoprotein identified in vascular endothelial cells. Although endoglin is essential for angiogenesis and its expression is up-regulated in inflammation and at sites of leukocyte extravasation, its role in leukocyte trafficking is unknown. This function was tested in endoglin heterozygous mice (Eng(+/-)) and their wild-type siblings Eng(+/+) treated with carrageenan or LPS as inflammatory agents. Both stimuli showed that inflammation-induced leukocyte transendothelial migration to peritoneum or lungs was significantly lower in Eng(+/-) than in Eng(+/+) mice. Leukocyte transmigration through cell monolayers of endoglin transfectants was clearly enhanced in the presence of endoglin. Coating transwells with the RGD-containing extracellular domain of endoglin, enhanced leukocyte transmigration, and this increased motility was inhibited by soluble endoglin. Leukocytes stimulated with CXCL12, a chemokine involved in inflammation, strongly adhered to endoglin-coated plates and to endoglin-expressing endothelial cells. This endoglin-dependent adhesion was abolished by soluble endoglin, RGD peptides, the anti-integrin α5β1 inhibitory antibody LIA1/2 and the chemokine receptor inhibitor AMD3100. These results demonstrate for the first time that endothelial endoglin interacts with leukocyte integrin α5β1 via its RGD motif, and this adhesion process is stimulated by the inflammatory chemokine CXCL12, suggesting a regulatory role for endoglin in transendothelial leukocyte trafficking.

Complement in pregnancy: a delicate balance

The complement system is a key component of innate host defence that, under normal conditions, is responsible for the opsonization and destruction of potential pathogens. However, inappropriate or excessive activation of complement can have a detrimental effect on the host and has been implicated in the pathophysiology of numerous disease states. Recently, there has been increasing evidence for a role of the complement system and, in particular, the potent pro-inflammatory anaphylatoxin complement component 5a (C5a) in both normal and complicated pregnancy. The following review describes the results of in vitro, animal, and human clinical studies investigating the role of the complement system in healthy pregnancy, recurrent miscarriage, preterm birth, and preeclampsia.

Endothelial dysfunction. An important mediator in the pathophysiology of hypertension during pre-eclampsia

Pre-eclampsia is defined as new onset hypertension with proteinuria during pregnancy. It affects approximately 5% of pregnancies in the US with a subset of those progressing into more severe forms of the disease, known as HELLP or eclampsia. Pre-eclampsia is associated with intrauterine growth restriction, chronic immune activation and multi-organ endothelial dysfunction thus contributing to the clinically visible elevation in maternal blood pressure. The end result is increased infant and maternal morbidity and mortality thereby contributing to the gross health care expenditure nationwide. Although the underlying cause of this disease is still unknown, the most well accepted hypothesis is that placental ischemia/hypoxia results from inadequate uteroplacental vascular remodeling, which leads to a decrease in placental blood flow. The ischemic placenta releases factors such as the soluble VEGF receptor-1 (sFlt-1), the angiotensin II type-1 receptor autoantibody (AT1-AA), and cytokines such as TNF-α and Interleukin 6 which cause maternal endothelial dysfunction characterized by elevated circulating endothelin (ET-1), reactive oxygen species (ROS), and enhanced vascular sensitivity to angiotensinII. These factors act in concert to decrease renal function and cause hypertension during pregnancy. Understanding the link between placental ischemia, endothelial dysfunction and hypertension during pregnancy will lend to better prediction, prevention and treatment strategies for women and children stricken by this devastating disease.

Preeclampsia 2012

Preeclampsia is a common complication of pregnancy associated with high maternal morbidity and mortality and intrauterine fetal growth restriction. There is extensive evidence that the reduction of uteroplacental blood flow in this syndrome results from the toxic combination of hypoxia, imbalance of angiogenic and antiangiogenic factors, inflammation, and deranged immunity. Women treated for preeclampsia also have an increased risk for cardiovascular and renal disease. At present it is unclear if the increased cardiovascular and renal disease risks are due to residual and or progressive effects of endothelial damage from the preeclampsia or from shared risk factors between preeclampsia and cardiac disease. Moreover, it appears that endothelin-1 signaling may play a central role in the hypertension associated with preeclampsia. In this paper, we discuss emerging data on the pathogenesis of preeclampsia and review therapeutic options.

MMP-15 is upregulated in preeclampsia, but does not cleave endoglin to produce soluble endoglin

Preeclampsia is a major pregnancy complication, characterized by severe endothelial dysfunction, hypertension and maternal end-organ damage. Soluble endoglin is an anti-angiogenic protein released from placenta and thought to play a central role in causing the endothelial dysfunction and maternal organ injury seen in severe preeclampsia. We recently reported MMP-14 was the protease producing placentally-derived soluble endoglin by cleaving full-length endoglin present on the syncytiotrophoblast surface. This find identifies a specific drug target for severe preeclampsia; interfering with MMP-14 mediated cleavage of endoglin could decrease soluble endoglin production, ameliorating clinical disease. However, experimental MMP-14 inhibition alone only partially repressed soluble endoglin production, implying other proteases might have a role in producing soluble endoglin. Here we investigated whether MMP-15–phylogenetically the closest MMP relative to MMP-14 with 66% sequence similarity–also cleaves endoglin to produce soluble endoglin. MMP-15 was localized to the syncytiotrophoblast layer of the placenta, the same site where endoglin was localized. Interestingly, it was significantly (p = 0.03) up-regulated in placentas from severe early-onset preeclamptic pregnancies (n = 8) compared to gestationally matched preterm controls (n = 8). However, siRNA knockdown of MMP-15 yielded no significant decrease of soluble endoglin production from either HUVECs or syncytialised BeWo cells in vitro. Importantly, concurrent siRNA knockdown of both MMP-14 and MMP-15 in HUVECS did not yield further decrease in soluble endoglin production compared to MMP-14 siRNA alone. We conclude MMP-15 is up-regulated in preeclampsia, but does not cleave endoglin to produce soluble endoglin.

Hypertension in pregnancy

Hypertension in pregnancy is diagnosed on systolic blood pressure greater than or equal to 140 mm Hg and/or diastolic greater than or equal to 90 mm Hg. The classification systems separate chronic and gestational hypertension from preeclampsia. Significant uncertainty regarding optimal management is reflected in the differing major international society recommendations. Blood pressure treatment is designed to minimize maternal end-organ damage. Methyldopa, labetalol, hydralazine, and nifedipine are oral options; angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists are contraindicated. Women with preeclampsia should be closely monitored and receive intravenous magnesium sulfate.

Preeclampsia up-regulates angiogenesis-associated microRNA (i.e., miR-17, -20a, and -20b) that target ephrin-B2 and EPHB4 in human placenta

CONTEXT

Placental angiogenesis contributes to the pathogenesis of preeclampsia (PE) that affects 5-8% of all human pregnancies. MicroRNA (miRNA) are a class of noncoding 21- to 25-nucleotide RNA that negatively regulate gene expression posttranscriptionly.

OBJECTIVE

The aim of this study was to test the hypothesis that miRNA are differentially expressed in healthy term and PE placentas and a subclass of angiogenesis-associated miRNA are increased by PE.

DESIGN

Total miRNA were extracted from villous placental tissues from healthy term and severe preeclamptic pregnancies. Differential miRNA expression was analyzed by microarray and real-time quantitative PCR. Angiogenesis-associated miRNA were analyzed by target prediction databases. In situ hybridization was used to localize miRNA. Target verification was performed by transfection of miRNA precursors or antagomirs into endothelial and BeWo cells and luciferase reporter assays.

RESULTS

Three highly expressed miRNA (miR-17, -20a, and -20b) were found significantly increased in PE compared with healthy term placentas (n = 10 per group). They target on the same group of genes important for angiogenesis. miR-20b was expressed primarily in villous syncytiotrophoblasts in term placenta. Overexpression or inhibition of miR-20b differentially regulated mRNA expression of those genes in endothelial vs. trophoblast cells. Luciferase reporter assay showed that miR-20b targets EPHB4 and ephrin-B2 that have been shown to be critical for early human placental development. Placental ephrin-B2 mRNA was significantly down-regulated in PE compared with normotensive pregnancies.

CONCLUSION

miR-17, miR-20a, and miR-20b are differentially regulated in human placentas by PE. They regulate EPHB4 and ephrin-B2 expression in trophoblast and endothelial cells via the same "seed" sequence, suggesting their roles in early placental development.

Maternal and cord steroid sex hormones, angiogenic factors, and insulin-like growth factor axis in African-American preeclamptic and uncomplicated pregnancies

BACKGROUND

A history of a preeclamptic pregnancy has been associated with subsequent increased risk of cardiovascular disease in the mother and decreased risk of breast cancer in both the mother and offspring. The concentrations of steroid sex hormones, angiogenic factors, and other proteins during pregnancy are important components of the in utero environment and may mediate the association of preeclampsia with later health outcomes. This study sought to compare an extensive profile of biological markers in both maternal and umbilical cord samples in preeclamptic and uncomplicated pregnancies of a predominantly African-American population.

METHODS

Steroid sex hormones, angiogenic factors, and components of the insulin-like growth factor axis were measured in maternal and umbilical cord sera from 48 pregnancies complicated by preeclampsia and 43 uncomplicated pregnancies. Regression models estimated the associations of these markers with preeclampsia, after adjusting for maternal and gestational age.

RESULTS

Concentrations of androgens (testosterone p = 0.06 and androstenedione p = 0.08) and the anti-angiogenic factors soluble fms-like kinase 1 (p = 0.004) and soluble endoglin (p = 0.004) were higher in the maternal circulation of women diagnosed with preeclampsia. These findings also were noted when the analyses were restricted to only African-American participants (77% of overall study population). Furthermore, among African-Americans, cord insulin-like growth factor-1 was lower in preeclamptic pregnancies than in controls.

CONCLUSIONS

The associations of maternal androgens and anti-angiogenic factors with preeclampsia are consistent with prior reports from predominantly Caucasian populations. Alterations in these analytes as well as other maternal and fetal biomarkers in preeclampsia could mediate the associations of preeclampsia with later health consequences.

The promise of angiogenic markers for the early diagnosis and prediction of preeclampsia

BACKGROUND

An imbalance in circulating factors that regulate blood vessel formation and health, referred to as angiogenic factors, plays a central role in the pathogenesis of preeclampsia.

CONTENT

Several studies have demonstrated a strong association between altered circulating angiogenic factors and preeclampsia. These factors include circulating antiangiogenic proteins such as soluble fms-like tyrosine kinase 1 and soluble endoglin and proangiogenic protein such as placental growth factor. Abnormalities in these circulating angiogenic factors are not only present during clinical disease, but also antedate clinical signs and symptoms by several weeks. These alterations are particularly prominent in patients who present with preeclamptic signs and symptoms prematurely and/or in patients with severe preeclampsia. The availability of automated platforms for the rapid measurement of circulating angiogenic proteins in blood samples has now allowed researchers and clinicians to evaluate the utility of these assays in the diagnosis of the disease, in the stratification of patients in clinical trials, or in the monitoring of therapies. In this review we highlight the various studies that have been performed, with a focus on large validation studies.

SUMMARY

Measurement of circulating angiogenic proteins for the diagnosis and prediction of preeclampsia is still at an early stage but is rapidly evolving. Standardization across the various automated platforms and prospective studies that demonstrate clinical utility are needed.

Differential expression of Vegfr-2 and its soluble form in preeclampsia

Background

Several studies have suggested that the main features of preeclampsia (PE) are consequences of endothelial dysfunction related to excess circulating anti-angiogenic factors, most notably, soluble sVEGFR-1 (also known as sFlt-1) and soluble endoglin (sEng), as well as to decreased PlGF. Recently, soluble VEGF type 2 receptor (sVEGFR-2) has emerged as a crucial regulator of lymphangiogenesis. To date, however, there is a paucity of information on the changes of VEGFR-2 that occur during the clinical onset of PE. Therefore, the aim of our study was to characterize the plasma levels of VEGFR-2 in PE patients and to perform VEGFR-2 immunolocalization in placenta.

Methodology/Principal findings

By ELISA, we observed that the VEGFR-2 plasma levels were reduced during PE compared with normal gestational age matched pregnancies, whereas the VEGFR-1 and Eng plasma levels were increased. The dramatic drop in the VEGFR-1 levels shortly after delivery confirmed its placental origin. In contrast, the plasma levels of Eng and VEGFR-2 decreased only moderately during the early postpartum period. An RT-PCR analysis showed that the relative levels of VEGFR-1, sVEGFR-1 and Eng mRNA were increased in the placentas of women with severe PE. The relative levels of VEGFR-2 mRNA as well as expressing cells, were similar in both groups. We also made the novel finding that a recently described alternatively spliced VEGFR-2 mRNA variant was present at lower relative levels in the preeclamptic placentas.

Conclusions/Significance

Our results indicate that the plasma levels of anti-angiogenic factors, particularly VEGFR-1 and VEGFR-2, behave in different ways after delivery. The rapid decrease in plasma VEGFR-1 levels appears to be a consequence of the delivery of the placenta. The persistent circulating levels of VEGFR-2 suggest a maternal endothelial origin of this peptide. The decreased VEGFR-2 plasma levels in preeclamptic women may serve as a marker of endothelial dysfunction.

Effects of SAC on oxidative stress and NO availability in placenta: potential benefits to preeclampsia

Preeclampsia (PE) is a major cause of fetal growth restriction and perinatal mortality, which involves oxidative stress and vasodilator signaling disorder. S-allyl-L-cysteine (SAC) is one of the most abundant compounds in garlic extracts, and possesses several biological activities. This research was designed to investigate the protective effects of SAC against H(2)O(2)-induced oxidative insults, as well as the effects on NO/cGMP signaling pathway in placenta. We used TEV-1 cells and placental explants to detect the effects of SAC. TEV-1 cells and human placental explants were separately exposed to SAC, H(2)O(2), or a combination of H(2)O(2) and SAC. Intracellular ROS was detected by flow cytometry; the NO level was detected by an NO metabolites (NOx) assay; the cGMP level was simultaneously measured by the method of radioimmunoassay; the expression of eNOS in TEV-1 cells was measured by immunochemistry and Western blot. Our findings showed that H(2)O(2) treatment increased ROS productions in TEV-1 cells and significantly decreased cGMP and NO level either in TEV-1 cells or explants compared to the control groups (p < 0.05). The expression of eNOS in TEV-1 cells also significantly decreased in H(2)O(2) treated group compared to the control group (p < 0.05). Co-treatment of H(2)O(2) and SAC significantly decreased ROS productions, and increased NO, cGMP and eNOS level compared to the H(2)O(2) treated alone groups (p < 0.05), which were all reverted back to near control levels. Further more, SAC treatment increased NO and cGMP level of TEV-1 cells and explants in a dose-dependent manner even at non-oxidative stress status (p < 0.05). However, when the TEV-1 cells were cultured in the presence of NOS inhibitor (L-NAME) and NO donor (SNP), additional SAC treatment still significantly increased the NO level in comparison with SAC non-treated group (p < 0.05). In conclusion, these results demonstrate that ROS (H(2)O(2)-mediated) can induce insults to NO/cGMP pathway, while SAC could antagonize this insult. And SAC also possesses the ability to increase NO and cGMP level at non-oxidative stress status in TEV-1 cells and placenta explants. SAC is therefore hypothesized to be a potential drug for PE treatment.

Hemodynamic, vascular, and reproductive impact of FMS-like tyrosine kinase 1 (FLT1) blockade on the uteroplacental circulation during normal mouse pregnancy

To investigate the role of FMS-like tyrosine kinase 1 (FLT1, also known as VEGFR1) signaling during pregnancy, mice were injected with anti-FLT1 neutralizing antibody (Ab) beginning on Gestational Day 8 or 12 and every other day thereafter until Day 18; vehicle-only injected mice served as controls. Uterine artery blood flow was measured with ultrasound on Days 13 and 18, and morphometric measurements of the uterine arcade were carried out on Day 19 to provide a measure of gestational vascular remodeling; reproductive performance was evaluated by determining litter size, resorption rates, and pup and placental weights. Ab injections beginning on Day 8 or Day 12 resulted in significant reductions of uterine artery peak systolic and diastolic flows at Days 13 and 18. In addition, normal reproductive function was compromised, as evidenced by a significant reduction in average number of viable pups along with enhanced resorption rates. Reproductive performance was also significantly compromised in this group, although less severely. There was no evidence of a reduction in main uterine artery diameters, though arterial distensibility was reduced, and the diameter of the main uterine vein was significantly smaller in the Ab-injected mice. Significant reductions in main uterine artery and segmental artery length were also noted. Placental and pup weights were similar in all the groups. FLT1 inhibition during murine pregnancy impaired blood flow to the fetal-placental unit, compromised several indices of vascular remodeling, reduced fecundity, and increased fetal reabsorptions. The effects of FLT1 inhibition are most pronounced when targeted during early pregnancy.

Atrial Remodeling in Pregnant Hypertensive Women: Comparison between Chronic and Gestational Hypertension

OBJECTIVES

Left atrial (LA) enlargement is a common finding in hypertensive patients (pts), however little information is available on LA changes during pregnancy. The present study evaluated LA size and function in pregnant women with hypertension.

METHODS

Patients population included 30 women with chronic hypertension and 30 patients with gestational hypertension. A control group of 16 normotensive pregnant women was selected. Serial echocardiography was performed at 12 and 24 week of gestation in chronic hypertension and at 24 week in gestational hypertension and after delivery. LA diameters and volumes were measured and compared. LA conduit volume, passive and active emptying volumes were calculated. Patients were divided in 2 groups according to max LAV Index > 32 ml/m(2) at 24 week of gestation.

RESULTS

Patients with chronic hypertension showed higher LA diameters (42 ± 2.0 vs. 36.5 ± 1.8; p<0.001) and LA volumes (maximal volume 45.5 ± 4.0 vs. 38.1 ± 7.3; p<0.001) compared with patients with gestational hypertension. The median value of max LAVI was 32 + 6.2 ml/m(2) in chronic and 26 + 5 ml/m(2) in gestational hypertension (p<0.01). During follow-up patients with max LAVI > 32 ml/m(2) had more clinical complications evaluated as increase of therapy, fluid retention that need diuretic and hospitalization.

CONCLUSION

Patients with chronic hypertension showed a more marked increased of LA volumes compared to gestational hypertension due to a remodeling of atrial shape as effect of chronic overload. Patients with more dilated LA volumes developed a greater number of clinical complications suggesting that a dilated LA could be a parameter of hemodynamic instability.

MMP-14 is expressed in preeclamptic placentas and mediates release of soluble endoglin

Soluble endoglin is an anti-angiogenic protein that is released from the placenta and contributes to both maternal endothelial dysfunction and the clinical features of severe preeclampsia. The mechanism through which soluble endoglin is released from the placenta is currently unknown; however, recent work in colorectal cancer identified matrix metalloproteinase 14 (MMP-14) as the cleavage protease of endoglin. To determine whether this is also the mechanism responsible for soluble endoglin release in preeclampsia, we investigated the expression of MMP-14 within the placenta and the effects of its inhibition on soluble endoglin release. Placentas were obtained from severe, early onset preeclamptic pregnancies (n = 8) and gestationally matched preterm controls (n = 8). MMP-14 was predominately localized to the syncytiotrophoblast. Results from a proximity ligation assay showed protein interactions between endogenous MMP-14 and endoglin within the preeclamptic placenta. To demonstrate that this interaction produces soluble endoglin, we treated trophoblastic BeWo cells with either a broad-spectrum MMP inhibitor (GM6001) or MMP-14 siRNA. Both treatments produced a decrease in soluble endoglin (P ≤ 0.05). Treatment of mice bearing BeWo xenografts with GM6001 decreased circulating soluble endoglin levels in mouse serum (P ≤ 0.05). These findings indicate that MMP-14 is the likely cleavage protease of endoglin in the setting of preeclampsia. This approach provides a novel method for the development of potential therapeutics to reduce circulating soluble endoglin and ameliorate the clinical features of severe preeclampsia.

Transcriptionally active syncytial aggregates in the maternal circulation may contribute to circulating soluble fms-like tyrosine kinase 1 in preeclampsia

The cardinal manifestations of the pregnancy-specific disorder preeclampsia, new-onset hypertension, and proteinuria that resolve with placental delivery have been linked to an extracellular protein made by the placenta, soluble fms-like tyrosine kinase 1 (sFlt1), that injures the maternal vasculature. However, the mechanisms by which sFlt1, which is heavily matrix bound, gain access to the systemic circulation remain unclear. Here we report that the preeclamptic placenta's outermost layer, the syncytiotrophoblast, forms abundant "knots" that are enriched with sFlt1 protein. These syncytial knots easily detach from the syncytiotrophoblast, resulting in free, multinucleated aggregates (50-150 μm diameter) that are loaded with sFlt1 protein and mRNA, are metabolically active, and are capable of de novo gene transcription and translation. At least 25% of the measurable sFlt1 in the third-trimester maternal plasma is bound to circulating placental microparticles. We conclude that detachment of syncytial knots from the placenta results in free, transcriptionally active syncytial aggregates that represent an autonomous source of sFlt1 delivery into the maternal circulation. The process of syncytial knot formation, shedding of syncytial aggregates, and appearance of placental microparticles in the maternal circulation appears to be greatly accelerated in preeclampsia and may contribute to the maternal vascular injury that characterizes this disorder.

Increased Myogenic Reactivity of Uterine Arteries from Pregnant Rats with Reduced Uterine Perfusion Pressure

The etiology of preeclampsia remains unknown. However, a contributing factor to this hypertensive disease of pregnancy is a reduction in uterine perfusion pressure resulting in placental ischemia. Uterine arteries may be a major regulator of this process through changes in vascular reactivity and localized blood flow. The reduced uterine perfusion pressure (RUPP) pregnant rat is an established animal model of preeclampsia pathology. Pregnant Sprague Dawley rats were used for this investigation and subjected to RUPP or SHAM surgery on Day 14 of gestation. On Day 21 of gestation, animals were terminated and resistance-caliber uterine arteries were harvested and mounted on a pressurized arteriograph to examine myogenic reactivity, agonist induced vasodilation (methacholine and VEGF), and vasoconstriction (phenylephrine and U-46619). Resistance-caliber uterine arteries from RUPP animals exhibited increased myogenic reactivity and decreased vasodilation (methacholine and VEGF) compared to SHAM uterine arteries (p<0.05). Phenylephrine and U-46619 induced constriction was similar in uterine arteries between RUPP and SHAM rats. These results suggest that resistancecaliber uterine arteries from RUPP pregnant rats are altered to reflect a more constrictive phenotype which may play a role in the development of maternal hypertension demonstrated in these animals and thereby potentially in preeclampsia.

Review: The feto-placental unit, pregnancy pathology and impact on long term maternal health

Pregnancy induces a number of alterations to maternal physiology to accommodate the increased demands made by the developing fetus and placenta. These alterations appear at least in part to be driven by products derived from the feto-placental unit, including microchimeric cells, as well as placental exosomes and microparticles, inducing changes to maternal physiology both during pregnancy and beyond. Further, increasing evidence suggests that some of these alterations are dependent on the sex of the fetus. Pre-eclampsia and asthma represent two common pregnancy complications that have provided valuable insight into how the feto-placental unit influences maternal physiology in a sex-specific manner. Pregnancy-induced alterations in maternal physiology may expose pre-existing subclinical pathologies and provide insight into future maternal health and disease. While most pregnancy-induced alterations to the maternal system are reversed following delivery, some can persist after parturition leading to cardiovascular, metabolic and autoimmune disease and increased risk of early mortality.

Is heparin a placental anticoagulant in high-risk pregnancies?

Randomized control trials show beneficial effects of heparin in high-risk pregnancies to prevent preeclampsia and intrauterine growth restriction. However, the lack of placental pathology data in these trials challenges the assumption that heparin is a placental anticoagulant. Recent data show that placental infarction is probably associated with abnormalities in development of the placenta, characterized by poor maternal perfusion and an abnormal villous trophoblast compartment in contact with maternal blood, than with maternal thrombophilia. At-risk pregnancies may therefore be predicted by noninvasive prenatal testing of placental function in mid-pregnancy. Heparin has diverse cellular functions that include direct actions on the trophoblast. Dissecting the non-anticoagulant actions of heparin may indicate novel and safer therapeutic targets to prevent the major placental complications of pregnancy.