An unexpected tail of VEGF and PlGF in pre-eclampsia

IL-6 Polymorphism as a Predisposing Genetic Factor for Gestational Diabetes or Preeclampsia Development in Pregnancy with Obesity in Relation to VEGF and VEGFF Receptor Gene Expression Modalities

The increased prevalence of obesity worldwide has been implicated in the alarming rise of the incidence of gestational diabetes and preeclampsia, which are both considered threatening conditions for both mother and fetus. We studied gene polymorphisms of the proinflammatory cytokine Interleukin 6 (IL-6) and the gene expression levels of VEGF (vascular endothelial growth factor) and VEGF-R (endothelial growth factor receptor), all known to be involved in pregnancy complications, aiming to identify possible predisposing risk factors in pregnancies with obesity. The G allele of IL-6 was found to correspond with an increased risk for gestational diabetes and preeclampsia occurrence. Furthermore, in obese pregnant mothers with either gestational diabetes or pre-existing type 2 diabetes and those who developed preeclampsia, it was confirmed that gene expression levels of VEGF were reduced while they were increased for VEGF receptors. We conclude that the genetic profile of an obese pregnant woman shares a common background with that of a patient with pre-existing type 2 diabetes mellitus, and therefore predisposes them to complications in pregnancy.

Potential urinary biomarkers in preeclampsia: a narrative review

INTRODUCTION

Preeclampsia (PE) is a highly relevant pregnancy-related disorder. An early and accurate diagnosis is crucial to prevent major maternal and neonatal complications and mortality. Due to the association of kidney dysfunction with the pathophysiology of the disease, urine samples have the potential to provide biomarkers for PE prediction, being minimally invasive and easy to perform. Therefore, searching for novel biomarkers may improve outcomes. This narrative review aimed to summarize the scientific literature about the traditional and potential urinary biomarkers in PE and to investigate their applicability to screen and diagnose the disorder.

METHODS

A non-systematic search was performed in PubMed/MEDLINE, Scopus, and SciELO databases.

RESULTS

There is significant divergence in the literature regarding traditionally used serum markers creatinine, cystatin C, and albuminuria, accuracy in PE prediction. As for the potential renal biomarkers investigated, including vascular epithelial growth factor (VEGF), placental growth factor (PlGF), and soluble fms-like tyrosine kinase (sFlt-1), urinary levels of PlGF and sFtl-1/PlGF ratio in urine seem to be the most promising as screening tests. The assessment of the global load of misfolded proteins through urinary congophilia, podocyturia, and nephrinuria has also shown potential for screening and diagnosis. Studies regarding the use of proteomics and metabolomics have shown good accuracy, sensitivity, and specificity for predicting the development and severity of PE.

CONCLUSION

However, there are still many divergences in the literature, which requires future and more conclusive research to confirm the predictive role of urinary biomarkers in pregnant women with PE.

Reliability of Rodent and Rabbit Models in Preeclampsia Research

In vivo studies on the pathology of gestation, including preeclampsia, often use small mammals such as rabbits or rodents, i.e., mice, rats, hamsters, and guinea pigs. The key advantage of these animals is their short reproductive cycle; in addition, similar to humans, they also develop a haemochorial placenta and present a similar transformation of maternal spiral arteries. Interestingly, pregnant dams also demonstrate a similar reaction to inflammatory factors and placentally derived antiangiogenic factors, i.e., soluble fms-like tyrosine kinase 1 (sFlt-1) or soluble endoglin-1 (sEng), as preeclamptic women: all animals present an increase in blood pressure and usually proteinuria. These constitute the classical duet that allows for the recognition of preeclampsia. However, the time of initiation of maternal vessel remodelling and the depth of trophoblast invasion differs between rabbits, rodents, and humans. Unfortunately, at present, no known animal replicates a human pregnancy exactly, and hence, the use of rabbit and rodent models is restricted to the investigation of individual aspects of human gestation only. This article compares the process of placentation in rodents, rabbits, and humans, which should be considered when planning experiments on preeclampsia; these aspects might determine the success, or failure, of the study. The report also reviews the rodent and rabbit models used to investigate certain aspects of the pathomechanism of human preeclampsia, especially those related to incorrect trophoblast invasion, placental hypoxia, inflammation, or maternal endothelial dysfunction.

The association of umbilical coiling and angiogenesis markers: Impact assessment of gestational diabetes

INTRODUCTION

The purpose of this study was to determine the association between the postnatal umbilical coiling index (pUCI) and vascular endothelial growth factor A (VEGFA) and its receptor (VEGFR2) in parturients with and without gestational diabetes mellitus (GDM).

METHODS

Within 24 h following birth, the umbilical cord and pUCI of 29 newborns with GDM and 28 neonates with non-GDM parturients were prospectively examined. Real-time PCR tests were used to determine the expression levels of the VEGFA and VEGFR2 genes, measured from the umbilical cord. The Mann-Whitney and Chi-squared tests were used to compare continuous and discrete variables with and without GDM.

RESULTS

The median (IQR) of maternal age was 30 (26-34) years. There were no differences in demographic features between GDM and non-GDM parturients. While there was a marginal difference in VEGFA expression levels between the GDM and non-GDM groups (P-values = 0.07), no difference was detected for VEGFR2 (P-values = 0.75). Comparing hyper- and hypocoiling cords revealed a small difference in VEGFA levels (P-values = 0.05), but no change in VEGFR2 (P-values = 0.50). Furthermore, in both GDM and non-GDM parturients, down-regulated VEGFA was the general rule among abnormal pUCIs.

DISCUSSION

The GDM and coiling state both are associated with the amount of VEGFA expression, but neither is related to VEGFR2. Furthermore, regardless of whether the patient has GDM or not, the abnormal coiling pattern appears to be related to the VEGFA down-regulation.

Maternal Obesity and Its Associated Factors and Outcomes in Klang Valley, Malaysia: Findings from National Obstetric Registry

INTRODUCTION

Maternal obesity presents significant health risks to mothers and their fetuses. This study aimed to determine the proportion, associated factors and outcomes of maternal obesity among pregnant women in Klang Valley, Malaysia.

METHODS

A retrospective cross-sectional study was conducted between January 2018 and March 2018 using secondary data from the Malaysian National Obstetric Registry (NOR) for the year 2015. All pregnant women with first-trimester booking at 12 weeks and below that were registered with the NOR and met the inclusion and exclusion criteria were included in the study. Descriptive statistics and multiple logistic regression analysis were used. Data were analysed using SPSS version 22.0. A total of 2113 respondents were included in this study to determine the proportion, associated factors and outcomes of maternal obesity. Regarding the univariate and multivariate analyses, respondents were classified into two groups: normal and obese. The obese group comprised overweight and obese mothers. The underweight group was excluded in the subsequent analysis.

RESULTS

Out of the 2113 respondents, 7.1% were underweight, 41.7% were of normal weight, 28.6% were overweight, 15.9% were in obese class I, 4.6% were in obese class II, and 2.1% were in obese class III according to the WHO (1995) reference. However, when the MOH (2003) cutoff point was used, there was a marked increase in the proportion of respondents in the overweight categories by 2.7% and obesity class I by 12.8%. The Indian (AdjOR 2.06, 95% CI: 1.11, 3.83, p=0.021) and Malay (AdjOR 1.75, 95% CI: 1.02, 3.00, p=0.040) ethnicities, as well as both multiparity (AdjOR 1.46, 95% CI: 1.23, 1.73, p <0.001) and grand multiparity (AdjOR 2.41, 95% CI: 1.78, 3.26, p <0.001), were significantly associated with maternal obesity. There were significant association between maternal obesity with hypertensive disorder in pregnancy (p=0.025), caesarean section delivery (p=0.002) and macrosomic infant (p <0.001).

CONCLUSION

The identification of risk factors for maternal obesity is important to facilitate intervention programmes focused on improving the pregnancy outcomes for a high-risk group of women.

Reduction of serum-induced endothelial STAT3(Y705) activation is associated with preeclampsia

OBJECTIVES

Preeclampsia is associated with maternal morbidity and mortality during pregnancy, and also an increased cardiovascular disease (CVD) risk later in life. During preeclampsia, alterations in secreted placental factors leading to systemic maternal endothelial dysfunction are evident. However, little is known about the associated endothelial intracellular signaling. STAT3 is a latent cytoplasmic transcription factor involved in endothelial cell differentiation, survival, and angiogenesis. We aimed to test if preeclampsia and preeclampsia-related placental factors could alter serum-induced STAT3(Y705) activation in endothelial cells. Furthermore, if altered serum-induced endothelial STAT3 (Y705) activation is related to post-preeclamptic CVD risk.

STUDY DESIGN

HUVECs were used as a model of maternal endothelium. Experiments entailed addition of 20% human pregnancy serum as well as addition of recombinant PlGF, sFLT1 and VEGF-A_165a to the cells.

MAIN OUTCOME MEASURES

Levels of pSTAT3(Y705) related to STAT3 levels were evaluated by immunoblotting analysis.

RESULTS

Our results show that preeclamptic serum induces significantly lower STAT3(Y705) phosphorylation compared with uncomplicated pregnancy serum (P = 0.0089) in endothelial cells. Furthermore, STAT3(Y705) phosphorylation was not changed upon addition of PlGF, sFLT1, or VEGF-A_165a together with pregnancy sera compared with sera alone. Finally, sera from women with previous preeclampsia and current hypertension and carotid atherosclerotic plaques show significantly lower STAT3(Y705) phosphorylation capabilities compared with healthy women with previous uncomplicated pregnancies 8-18 years after deliveries (P = 0.029).

CONCLUSIONS

Reduction in serum-induced endothelial STAT3(Y705) activation may play an important role in the preeclampsia-associated endothelial dysfunction. Additionally, reduced endothelial STAT3(Y705) phosphorylation may contribute to increased post-preeclamptic CVD risk 8-18 years after delivery.

Midpregnancy testing for soluble fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF): An inter-assay comparison of three automated immunoassay platforms

We performed an inter-assay comparison among three immunoassay platforms for midpregnancy testing of sFlt-1, PlGF and the sFlt-1/PlGF ratio, which are established markers for pre-eclampsia. Maternal blood was collected 19-22 weeks' gestation. Raw data values were converted to multiples of the median (MoM). PlGF and sFlt-1 values among platforms were highly correlated (p < 0.001). There was significant variation in raw data values for PlGF and sFlt-1 among platforms, eliminated following conversion to MoM. When directly comparing raw data values among platforms, platform-specific reference ranges values should be used. MoM values were equivalent among platforms, allowing direct inter-assay result comparison.

Angiogenesis, Lymphangiogenesis, and the Immune Response in South African Preeclamptic Women Receiving HAART

Purpose of the review: This review highlights the role of angiogenesis, lymphangiogenesis, and immune markers in human immunodeficiency virus (HIV)-associated preeclamptic (PE) pregnancies in an attempt to unravel the mysteries underlying the duality of both conditions in South Africa. Recent findings: Studies demonstrate that HIV-infected pregnant women develop PE at a lower frequency than uninfected women. In contrast, women receiving highly active anti-retroviral therapy (HAART) are more inclined to develop PE, stemming from an imbalance of angiogenesis, lymphangiogenesis, and immune response. Summary: In view of the paradoxical effect of HIV infection on PE development, this study examines angiogenesis, lymphangiogenesis, and immune markers in the highly HIV endemic area of KwaZulu-Natal. We believe that HAART re-constitutes the immune response in PE, thereby predisposing women to PE development. This susceptibility is due to an imbalance in the angiogenic/lymphangiogenic/immune response as compared to normotensive pregnant women. Further large-scale studies are urgently required to investigate the effect of the duration of HAART on PE development.

Targeting the vascular dysfunction: Potential treatments for preeclampsia

Preeclampsia is a pregnancy-specific disorder, primarily characterized by new-onset hypertension in combination with a variety of other maternal or fetal signs. The pathophysiological mechanisms underlying the disease are still not entirely clear. Systemic maternal vascular dysfunction underlies the clinical features of preeclampsia. It is a result of oxidative stress and the actions of excessive anti-angiogenic factors, such as soluble fms-like tyrosine kinase, soluble endoglin, and activin A, released by a dysfunctional placenta. The vascular dysfunction then leads to impaired regulation and secretion of relaxation factors and an increase in sensitivity/production of constrictors. This results in a more constricted vasculature rather than the relaxed vasodilated state associated with normal pregnancy. Currently, the only effective "treatment" for preeclampsia is delivery of the placenta and therefore the baby. Often, this means a preterm delivery to save the life of the mother, with all the attendant risks and burdens associated with fetal prematurity. To lessen this burden, there is a pressing need for more effective treatments that target the maternal vascular dysfunction that underlies the hypertension. This review details the vascular effects of key drugs undergoing clinical assessment as potential treatments for women with preeclampsia.

Loss of placental growth factor ameliorates maternal hypertension and preeclampsia in mice

Preeclampsia remains a clinical challenge due to its poorly understood pathogenesis. A prevailing notion is that increased placental production of soluble fms-like tyrosine kinase-1 (sFlt-1) causes the maternal syndrome by inhibiting proangiogenic placental growth factor (PlGF) and VEGF. However, the significance of PlGF suppression in preeclampsia is uncertain. To test whether preeclampsia results from the imbalance of angiogenic factors reflected by an abnormal sFlt-1/PlGF ratio, we studied PlGF KO (Pgf-/-) mice and noted that the mice did not develop signs or sequelae of preeclampsia despite a marked elevation in circulating sFLT-1. Notably, PlGF KO mice had morphologically distinct placentas, showing an accumulation of junctional zone glycogen. We next considered the role of placental PlGF in an established model of preeclampsia (pregnant catechol-O-methyltransferase-deficient [COMT-deficient] mice) by generating mice with deletions in both the Pgf and Comt genes. Deletion of placental PlGF in the context of COMT loss resulted in a reduction in maternal blood pressure and increased placental glycogen, indicating that loss of PlGF might be protective against the development of preeclampsia. These results identify a role for PlGF in placental development and support a complex model for the pathogenesis of preeclampsia beyond an angiogenic factor imbalance.

The role of placental growth factor (PlGF) and its receptor system in retinal vascular diseases

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. Upon binding to VEGF- and neuropilin-receptor sub-types, PlGF modulates a range of neural, glial and vascular cell responses that are distinct from VEGF-A. As PlGF expression is selectively associated with pathological angiogenesis and inflammation, its blockade does not affect the healthy vasculature. PlGF actions have been extensively described in tumor biology but more recently there has been accumulating preclinical evidence that indicates that this growth factor could have an important role in retinal diseases. High levels of PlGF have been found in aqueous humor, vitreous and/or retina of patients exhibiting retinopathies, especially those with diabetic retinopathy (DR) and neovascular age-related macular degeneration (nvAMD). Expression of this growth factor seems to correlate closely with many of the key pathogenic features of early and late retinopathy in preclinical models. For example, studies using genetic modification and/or pharmacological treatment to block PlGF in the laser-induced choroidal neovascularization (CNV) model, oxygen-induced retinopathy model, as well as various murine diabetic models, have shown that PlGF deletion or inhibition can reduce neovascularization, retinal leakage, inflammation and gliosis, without affecting vascular development or inducing neuronal degeneration. Moreover, an inhibitory effect of PlGF blockade on retinal scarring in the mouse CNV model has also been recently demonstrated and was found to be unique for PlGF inhibition, as compared to various VEGF inhibition strategies. Together, these preclinical results suggest that anti-PlGF therapy might have advantages over anti-VEGF treatment, and that it may have clinical applications as a standalone treatment or in combination with anti-VEGF. Additional clinical studies are clearly needed to further elucidate the role of PlGF and its potential as a therapeutic target in ocular diseases.

Molecular determinants of microvascular dysfunction in hypertensive pregnancy and preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and often fetal intrauterine growth restriction, but the underlying mechanisms are unclear. Defective placentation and apoptosis of invasive cytotrophoblasts cause inadequate remodeling of spiral arteries, placental ischemia, and reduced uterine perfusion pressure (RUPP). RUPP causes imbalance between the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the pro-angiogenic vascular endothelial growth factor and placental growth factor, and stimulates the release of proinflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors target the vascular endothelium, smooth muscle and various components of the extracellular matrix. Generalized endotheliosis in systemic, renal, cerebral, and hepatic vessels causes decreases in endothelium-derived vasodilators such as nitric oxide, prostacyclin and hyperpolarization factor, and increases in vasoconstrictors such as endothelin-1 and thromboxane A2. Enhanced mechanisms of vascular smooth muscle contraction, such as intracellular Ca2+ , protein kinase C, and Rho-kinase cause further increases in vasoconstriction. Changes in matrix metalloproteinases and extracellular matrix cause inadequate vascular remodeling and increased arterial stiffening, leading to further increases in vascular resistance and hypertension. Therapeutic options are currently limited, but understanding the molecular determinants of microvascular dysfunction could help in the design of new approaches for the prediction and management of preeclampsia.

Evaluation of Placental VEGFA mRNA Expression in Preeclampsia: A Case Control Study

Objective

The aim of our case-control study was to determine expression of VEGFA mRNA in placentae of preeclamsia (PE) versus uncomplicated pregnancy to further clarify its differential expression in pregnancy hypertensive disorders.

Study Design

The PE group was subdivided into severe and non-severe; those with or without HELLP syndrome and placental VEGFA characteristics were compared for these cohorts. Additionally, the neonatal and maternal outcomes were recorded. The quantification of placental VEGFA was done using quantitative real-time PCR and results were expressed as fold change.

Results

Out of 42 PE cases, 23 (55%) were non-severe and 19 cases (45%) were severe PE. Out of 19 severe PE patients, 8 (42%) were HELLP syndrome (complete HELLP) and remaining 11 (58%) were non-HELLP severe PE. Compared to controls, the true fold change in PE, HELLP, non-HELLP, severe PE, non-severe PE was - 2.186, - 13.333, - 6.698, - 8.950 and 1.466, respectively.

Conclusions

Our results showed a lowered VEGFA expression in PE placentae compared to uncomplicated controls. The finding of initial increase of VEGFA in non-severe PE and subsequent marked lowering in HELLP strengthens the existing hypothesis of decompensated VEGF being a major role player in PE.

Overexpression of preeclampsia induced microRNA-26a-5p leads to proteinuria in zebrafish

So far the pathomechanism of preeclampsia in pregnancy is focussed on increased circulating levels of soluble fms-like tyrosin kinase-1 (sFLT-1) that neutralizes glomerular VEGF-A expression and prevents its signaling at the glomerular endothelium. As a result of changed glomerular VEGF-A levels endotheliosis and podocyte foot process effacement are typical morphological features of preeclampsia. Recently, microRNA-26a-5p (miR-26a-5p) was described to be also upregulated in the preeclamptic placenta. We found that miR-26a-5p targets VEGF-A expression by means of PIK3C2α in cultured human podocytes and that miR-26a-5p overexpression in zebrafish causes proteinuria, edema, glomerular endotheliosis and podocyte foot process effacement. Interestingly, recombinant zebrafish Vegf-Aa protein could rescue glomerular changes induced by miR-26a-5p. In a small pilot study, preeclamptic patients with podocyte damage identified by podocyturia, expressed significantly more urinary miR-26a-5p compared to healthy controls. Thus, functional and ultrastructural glomerular changes after miR-26a-5p overexpression can resemble the findings seen in preeclampsia and indicate a potential pathophysiological role of miR-26a-5p in addition to sFLT-1 in this disease.

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.

A computational analysis of in vivo VEGFR activation by multiple co-expressed ligands

The splice isoforms of vascular endothelial growth A (VEGF) each have different affinities for the extracellular matrix (ECM) and the coreceptor NRP1, which leads to distinct vascular phenotypes in model systems expressing only a single VEGF isoform. ECM-immobilized VEGF can bind to and activate VEGF receptor 2 (VEGFR2) directly, with a different pattern of site-specific phosphorylation than diffusible VEGF. To date, the way in which ECM binding alters the distribution of isoforms of VEGF and of the related placental growth factor (PlGF) in the body and resulting angiogenic signaling is not well-understood. Here, we extend our previous validated cell-level computational model of VEGFR2 ligation, intracellular trafficking, and site-specific phosphorylation, which captured differences in signaling by soluble and immobilized VEGF, to a multi-scale whole-body framework. This computational systems pharmacology model captures the ability of the ECM to regulate isoform-specific growth factor distribution distinctly for VEGF and PlGF, and to buffer free VEGF and PlGF levels in tissue. We show that binding of immobilized growth factor to VEGF receptors, both on endothelial cells and soluble VEGFR1, is likely important to signaling in vivo. Additionally, our model predicts that VEGF isoform-specific properties lead to distinct profiles of VEGFR1 and VEGFR2 binding and VEGFR2 site-specific phosphorylation in vivo, mediated by Neuropilin-1. These predicted signaling changes mirror those observed in murine systems expressing single VEGF isoforms. Simulations predict that, contrary to the 'ligand-shifting hypothesis,' VEGF and PlGF do not compete for receptor binding at physiological concentrations, though PlGF is predicted to slightly increase VEGFR2 phosphorylation when over-expressed by 10-fold. These results are critical to design of appropriate therapeutic strategies to control VEGF availability and signaling in regenerative medicine applications.

Serum levels of platelet endothelial cell adhesion molecule-1 (PECAM-1) and soluble vascular endothelial growth factor receptor (sVEGFR)-1 and -2 in HIV associated preeclampsia

OBJECTIVE

The angiogenic-antiangiogenic imbalance evident in preeclampsia (PE) may be used as a predictive tool to identify women likely to develop the clinical features in early pregnancy.

METHOD

This retrospective study examined normotensive pregnant (n = 38) and preeclamptic (n = 38) HIV-infected and uninfected women to quantify sVEGFR-1 and -2 and PECAM-1 levels.

RESULTS

In contrast to PECAM-1, sVEGFR-1 and -2 differed according to pregnancy type (p = 0.07; p = 0.001; p = 0.002) but not by HIV status (p = 0.68; p = 0.13; p = 0.43).

CONCLUSION

Irrespective of the HIV status, we report an upregulation of sVEGFR-1 with concomitant decline of PECAM-1 and sVEGFR-2 levels in PE compared to normotensive pregnancies.

Vascular adaptation in pregnancy and endothelial dysfunction in preeclampsia

Maternal vascular adaptation to pregnancy is critically important to expand the capacity for blood flow through the uteroplacental unit to meet the needs of the developing fetus. Failure of the maternal vasculature to properly adapt can result in hypertensive disorders of pregnancy such as preeclampsia (PE). Herein, we review the endocrinology of maternal adaptation to pregnancy and contrast this with that of PE. Our focus is specifically on those hormones that directly influence endothelial cell function and dysfunction, as endothelial cell dysfunction is a hallmark of PE. A variety of growth factors and cytokines are present in normal vascular adaptation to pregnancy. However, they have also been shown to be circulating at abnormal levels in PE pregnancies. Many of these factors promote endothelial dysfunction when present at abnormal levels by acutely inhibiting key Ca²⁺ signaling events and chronically promoting the breakdown of endothelial cell-cell contacts. Increasingly, our understanding of how the contributions of the placenta, immune cells, and the endothelium itself promote the endocrine milieu of PE is becoming clearer. We then describe in detail how the complex endocrine environment of PE affects endothelial cell function, why this has contributed to the difficulty in fully understanding and treating this disorder, and how a focus on signaling convergence points of many hormones may be a more successful treatment strategy.

The effects of sildenafil citrate on urinary podocin and nephrin mRNA expression in an L-NAME model of pre-eclampsia

We investigated the effects of sildenafil citrate (SC) on podocyturia in N ^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME) model of pre-eclampsia (PE). One hundred and twenty Sprague-Dawley rats (SDR) were divided into five groups like pregnant control (PC), early-onset PE (EOPE), late-onset PE(LOPE), early and late-onset PE with SC-treated groups [EOPE (SC); LOPE (SC)]. PE was induced in SDR by oral administration of L-NAME in drinking water for 4-8 days for EOPE and 8-14 day for LOPE. The blood pressure, urine volume and total urine protein were increased in EOPE and LOPE groups when compared to PC, and all the above parameters decreased in EOPE (SC) and LOPE (SC) groups when compared to EOPE and LOPE groups, respectively. The EOPE and LOPE groups showed an increase in urinary nephrin mRNA and podocin mRNA levels compared to PC group. Increases in serum and renal soluble fms-like tyrosine kinase-1 (sFlt-1) expression levels and decreases in renal vascular endothelial growth factor (VEGF) expression and serum placenta growth factor (PlGF) levels were observed in EOPE and LOPE groups when compared to PC group. In addition, decreases in serum and renal sFlt-1 expression levels and increases in renal VEGF expression and serum PlGF levels were observed in EOPE (SC) and LOPE (SC) groups when compared to EOPE and LOPE groups, respectively. The light microscopy showed that the renal tissue of L-NAME-treated rats had extensive glomerular damage, tubular damage and infiltration by mononuclear cells when compared to PC group. Therefore, SC ameliorated podocyturia through its effects on the antiangiogenic/angiogenic status in this animal model.

Use of serum and urinary soluble sFlt-1 and PLGF in the diagnosis of preeclampsia

OBJECTIVE

Preeclampsia (PE) is a disorder of pregnancy marked by hypertension and proteinuria with no known treatment aside from pregnancy termination. The pathogenesis of PE is poorly understood, but is thought to originate in the placenta. We assessed the value of measuring serum and urinary soluble deformylase-like tyrosine kinase receptor 1 (sFlt-1), a known target of placental factors, and placental growth factor (PLGF), a key placental signaling molecule, in the diagnosis of PE.

METHODS

Eighty patients with PE were classified as either exhibiting mild (44 cases) or severe (36 cases) symptoms of PE. Forty normal pregnant women were selected as controls. Serum and urinary PLGF and sFlt-1 levels, along with the ratio of sFlt-1 to PLGF, were compared across groups.

RESULTS

Serum and urinary sFlt-1 and sFlt-1/PLGF ratios in severe PE patients were significantly higher than those in the mild PE group, and measurements from mild PE patients were significantly higher than controls (all P values <0.01). The serum and urinary PLGF levels in severe PE patients were significantly lower than mild PE patients, and mild PE patients had significantly lower PLGF levels than controls (all P values <0.01). As expected, serum sFlt-1 and PLGF levels and ratios were highly correlated with urinary sFlt-1 and PLGF levels and ratios.

CONCLUSIONS

The severity of PE was closely correlated with these measurements, suggesting that they may be useful tools in the diagnosis and evaluation of PE.

Restoring placental growth factor-soluble fms-like tyrosine kinase-1 balance reverses vascular hyper-reactivity and hypertension in pregnancy

Preeclampsia (PE) is a pregnancy-related hypertensive disorder (HTN-Preg) with unclear mechanism. An imbalance between antiangiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) and angiogenic placental growth factor (PlGF) has been observed in PE, but the vascular targets and signaling pathways involved are unclear. We assessed the extent of sFlt-1/PlGF imbalance and vascular dysfunction in a rat model of HTN-Preg produced by reduction of uteroplacental perfusion pressure (RUPP), and tested whether inducing a comparable sFlt-1/PlGF imbalance by infusing sFlt-1 (10 μg·kg(-1)·day(-1)) in day 14 pregnant (Preg) rats cause similar increases in blood pressure (BP) and vascular reactivity. Using these guiding measurements, we then tested whether restoring sFlt-1/PlGF balance by infusing PIGF (20 μg·kg(-1)·day(-1)) in RUPP rats would improve BP and vascular function. On gestational day 19, BP was in Preg+sFlt-1 and RUPP > Preg, and in RUPP+PlGF < RUPP rats. Plasma sFlt-1/PlGF ratio was increased in Preg+sFlt-1, and RUPP and was reduced in RUPP+PlGF rats. In isolated endothelium-intact aorta, carotid, mesenteric, and renal artery, phenylephrine (Phe)- and high KCl-induced contraction was in Preg+sFlt-1 and RUPP > Preg, and in RUPP+PlGF < RUPP. The differences in vascular reactivity to Phe and KCl between groups were less apparent in vessels treated with the nitric oxide synthase (NOS) inhibitor l-NAME or guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or endothelium-denuded, suggesting changes in endothelial NO-cGMP pathway. In Phe precontracted vessels, ACh-induced relaxation was in Preg+sFlt-1 and RUPP < Preg, and in RUPP+PlGF > RUPP, and was blocked by N(ω)-nitro-l-arginine methyl ester (l-NAME) or ODQ treatment or endothelium removal. Western blots revealed that aortic total endothelial NOS (eNOS) and activated phosphorylated-eNOS were in Preg+sFlt-1 and RUPP < Preg and in RUPP+PlGF > RUPP. ACh-induced vascular nitrate/nitrite production was in Preg+sFlt-1 and RUPP < Preg, and in RUPP+PlGF > RUPP. Vascular relaxation to the exogenous NO donor sodium nitroprusside was not different among groups. Thus, a tilt in the angiogenic balance toward anti-angiogenic sFlt-1 is associated with decreased vascular relaxation and increased vasoconstriction and BP. Restoring the angiogenic/antiangiogenic balance using PlGF enhances endothelial NO-cGMP vascular relaxation and decreases vasoconstriction and BP in HTN-Preg rats and could offer a new approach in the management of PE.

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.

Human placenta-derived stromal cells decrease inflammation, placental injury and blood pressure in hypertensive pregnant mice

Pre-eclampsia, the development of hypertension and proteinuria or end-organ damage during pregnancy, is a leading cause of both maternal and fetal morbidity and mortality, and there are no effective clinical treatments for pre-eclampsia aside from delivery. The development of pre-eclampsia is characterized by maladaptation of the maternal immune system, excessive inflammation and endothelial dysfunction. We have reported that detection of extracellular RNA by the Toll-like receptors (TLRs) 3 and 7 is a key initiating signal that contributes to the development of pre-eclampsia. PLacental eXpanded (PLX-PAD) cells are human placenta-derived, mesenchymal-like, adherent stromal cells that have anti-inflammatory, proangiogenic, cytoprotective and regenerative properties, secondary to paracrine secretion of various molecules in response to environmental stimulation. We hypothesized that PLX-PAD cells would reduce the associated inflammation and tissue damage and lower blood pressure in mice with pre-eclampsia induced by TLR3 or TLR7 activation. Injection of PLX-PAD cells on gestational day 14 significantly decreased systolic blood pressure by day 17 in TLR3-induced and TLR7-induced hypertensive mice (TLR3 144-111 mmHg; TLR7 145-106 mmHg; both P<0.05), and also normalized their elevated urinary protein:creatinine ratios (TLR3 5.68-3.72; TLR7 5.57-3.84; both P<0.05). On gestational day 17, aortic endothelium-dependent relaxation responses improved significantly in TLR3-induced and TLR7-induced hypertensive mice that received PLX-PAD cells on gestational day 14 (TLR3 35-65%; TLR7 37-63%; both P<0.05). In addition, markers of systemic inflammation and placental injury, increased markedly in both groups of TLR-induced hypertensive mice, were reduced by PLX-PAD cells. Importantly, PLX-PAD cell therapy had no effects on these measures in pregnant control mice or on the fetuses. These data demonstrate that PLX-PAD cell therapy can safely reverse pre-eclampsia-like features during pregnancy and have a potential therapeutic role in pre-eclampsia treatment.

Bioactive factors in uteroplacental and systemic circulation link placental ischemia to generalized vascular dysfunction in hypertensive pregnancy and preeclampsia

Preeclampsia is a pregnancy-associated disorder characterized by hypertension, and could lead to maternal and fetal morbidity and mortality; however, the pathophysiological mechanisms involved are unclear. Predisposing demographic, genetic and environmental risk factors could cause localized abnormalities in uteroplacental cytoactive factors such as integrins, matrix metalloproteinases, cytokines and major histocompatibility complex molecules leading to decreased vascular remodeling, uteroplacental vasoconstriction, trophoblast cells apoptosis, and abnormal development of the placenta. Defective placentation and decreased trophoblast invasion of the myometrium cause reduction in uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia, an important event in preeclampsia. RUPP could stimulate the release of circulating bioactive factors such as the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin that cause imbalance with the pro-angiogenic factors vascular endothelial growth factor and placental growth factor, or cause the release of inflammatory cytokines, reactive oxygen species, hypoxia-induced factor-1 and AT1 angiotensin receptor agonistic autoantibodies. The circulating bioactive factors target endothelial cells causing generalized endotheliosis, endothelial dysfunction, decreased vasodilators such as nitric oxide and prostacyclin and increased vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction. The bioactive factors also stimulate the mechanisms of VSM contraction including Ca(2+), protein kinase C, and Rho-kinase and induce extracellular matrix remodeling leading to further vasoconstriction and hypertension. While therapeutic options are currently limited, understanding the underlying mechanisms could help design new interventions for management of preeclampsia.

The optimization of a chronic nitric oxide synthase (NOS) inhibition model of pre-eclampsia by evaluating physiological changes

OBJECTIVES

In order to address the gap in our understanding of the pathogenesis and pathophysiology of PE, we optimized the NOS inhibition animal model by comparing changes in different parameters at various time frames during pregnancy, in both early and late-onset PE.

STUDY DESIGN

120 nulliparous Sprague-Dawley rats were divided into 5 groups (n=24). A pregnant control, two groups that represented early and late-onset PE and two groups that were treated with sildenafil citrate (SC) to show reversal of the pre-eclamptic-like symptoms.

RESULTS

Our results showed that treatment with L-NAME caused significant changes in physiological parameters for both early and late-onset PE groups. There was a significant increase in systolic blood pressure (SBP) levels in the early-onset PE group (128.5±5.71 mmHg) and late-onset PE group (128.3±6.15 mmHg) on day 19 compared to the SBPs on day 0, (p<0.01). Urine excretion volumes in the early-onset PE group (13.62±3.18 mL) and in the late-onset PE (13.28±2.60 mL), compared to the pregnant control group (11.96±1.9 mL) were also increased (p<0.05). There was also an increase in total urinary protein in the early-onset PE group (0.62±0.08 g/L and the late-onset PE group (0.45±0.05 g/L), when compared to the pregnant control group (0.38±0.07) (p<0.05). We also found a decrease in fetal numbers in the PE group in comparison to the pregnant control and SC treated groups. The remission of these signs was seen after delivery of the fetuses. We also demonstrated that treatment of this syndrome with SC prevented the development of these signs.

CONCLUSIONS

The NOS inhibition model can be used for the study of the pathogenesis and pathophysiology of PE, since the pathogenic changes mimic those of early and late-PE.

Concentrations of endothelial nitric oxide synthase, angiotensin-converting enzyme, vascular endothelial growth factor and placental growth factor in maternal blood and maternal metabolic status in pregnancy complicated by hypertensive disorders

Hypertensive disorders of pregnancy (HDPs) are associated with altered maternal metabolism, impaired perinatal outcome and increased risk for remote maternal complications. The aim of our study was to analyse associations between circulating levels of angiogenic factors and markers of oxidative stress and metabolic status in women with HDP. Forty-six women in singleton pregnancies complicated by HDP and 30 healthy controls were enrolled in a prospective observational study. Serum concentrations of endothelial nitric oxide synthase (eNOS), angiotensin-converting enzyme, vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) were measured in the third trimester and correlated with maternal anthropometrics and metabolic status. We found significantly lower eNOS levels in patients with severe hypertension vs controls, a strong association between eNOS and PlGF in the study group, a significant association between maternal prepregnancy body mass index (BMI) and VEGF levels and an inverse correlation between VEGF and PlGF. Maternal prepregnancy BMI was the only independent predictor for VEGF concentrations. We noted reduced levels of PlGF and eNOS and increased VEGF levels in women with severe hypertension/preeclampsia. First, different forms of HDP are associated with different alteration patterns in concentrations of angiogenic factors and markers of oxidative stress. Second, maternal prepregnancy BMI, but not body weight, is a significant predictor for VEGF levels in late pregnancy.

Associations between insulin-like growth factor I, vascular endothelial growth factor and its soluble receptor 1 in umbilical serum and endothelial cells obtained from normotensive and preeclamptic pregnancies

The aim of this study was to investigate the associations between insulin-like growth factor I (IGF-I) with vascular endothelial growth factor (VEGF) and its soluble receptor 1 (sFlt-1) in umbilical serum and to study the effects of IGF-I upon sFlt-1 synthesis in human umbilical vein endothelial cells (HUVEC) in normotensive (NT) and preeclamptic (PE) pregnancies. As compared with the NT group, umbilical serum IGF-I and VEGF levels were lower in the PE group, while sFlt-1 concentrations were higher. Levels of sFlt-1 correlated with IGF-I in the NT group and with VEGF in the PE group. Basal concentration of sFlt-1 in HUVEC culture media was higher in the PE group. IGF-I stimulated sFlt-1 synthesis only in the NT group. In summary, umbilical serum sFlt-1 is associated with IGF-I in normotensive pregnancy and with VEGF in preeclampsia. IGF-I stimulates sFlt-1 synthesis in endothelial cells in normotensive but not in PE pregnancies.

Advances in the cellular and molecular biology of angiogenesis

Capillaries have been recognized for over a century as one of the most important components in regulating tissue oxygen transport, and their formation or angiogenesis a pivotal element of tissue remodelling during development and adaptation. Clinical interest stems from observations that both excessive and inadequate vascular growth plays a major role in human diseases, and novel developments in treatments for cancer and eye disease increasingly rely on anti-angiogenic therapies. Although the discovery of VEGF (vascular endothelial growth factor) provided the first clue for specificity of signalling in endothelial cell activation, understanding the integrative response that drives angiogenesis requires a much broader perspective. The Advances in the Cellular and Molecular Biology of Angiogenesis meeting brought together researchers at the forefront of this rapidly moving field to provide an update on current understanding, and the most recent insights into molecular and cellular mechanisms of vascular growth. The plenary lecture highlighted the integrative nature of the angiogenic process, whereas invited contributions from basic and clinician scientists described fundamental mechanisms and disease-associated issues of blood vessel formation, grouped under a number of themes to aid discussion. These articles will appeal to academic, clinical and pharmaceutical scientists interested in the molecular and cellular basis of angiogenesis, their modulation or dysfunction in human diseases, and application of these findings towards translational medicine.