Circulating Angiogenic Factors in the Pathogenesis and Prediction of Preeclampsia

Control of soluble fms-like tyrosine-1 (sFlt-1) production response to placental ischemia/hypoxia: role of tumor necrosis factor-α

Although abnormal soluble fms-like tyrosine kinase-1 (sFlt-1) production is thought to be an important factor in the pathogenesis of preeclampsia (PE), the mechanisms that regulate the production of sFlt-1 during PE are unclear. While our laboratory has shown tumor necrosis factor-α (TNF-α) and sFlt-1 to be elevated in pregnant rats in response to placental ischemia, the importance of TNF-α in the regulation of sFlt-1 production is unknown. Therefore, the purpose of this study was to determine the role of TNF-α in mediating the increase in sFlt-1 in response to placental ischemia or hypoxia. Reductions in uterine perfusion pressure in pregnant rats significantly increased plasma levels of sFlt-1 and tended to increase TNF-α, an effect markedly attenuated by pretreatment with a TNF-α inhibitor etanercept (0.4 mg/kg). To further assess chronic interactions between TNF-α and sFlt-1, we examined a chronic effect of TNF-α infusion (50 ng/day) into normal pregnant rats to increase plasma sFlt-1 levels, as well as the effects of acute hypoxia on placental sFlt-1 production in the absence and presence of TNF-α blockade. Placental explants exposed to hypoxic conditions had enhanced TNF-α levels versus normoxic conditions, as well as increased sFlt-1 production. Pretreatment of placental explants with etanercept (15 μM) significantly reduced TNF-α levels in response to hypoxia but did not attenuate sFlt-1 production. These data suggest that while TNF-α may not play an important role in stimulating sFlt-1 production in response to acute hypoxia, a more chronic hypoxia, or placental ischemia may be an important stimulus for enhanced sFlt-l production.

Angiogenic factors in preeclampsia and related disorders

During fetal development, the human placenta undergoes high levels of both angiogenesis and vasculogenesis. Additionally, the developing placenta undergoes a process of vascular mimicry (referred to as pseudovasculogenesis) as cytotrophoblasts convert from an epithelial to an endothelial phenotype. The initiation, maturation, and maintenance of the placental vasculature are of critical importance. Failure to do so can lead to adverse obstetric outcomes such as preeclampsia and/or intrauterine growth restriction (IUGR). Furthermore, the foundation of many aspects of adult health is laid in utero. In this context, normal placental function is not only critical for normal fetal development but can also permanently influence long-term health and disease. Understanding the mechanisms that regulate placental vasculogenesis and angiogenesis is therefore of critical importance. This chapter will focus on placental vascular development with a particular emphasis on the role of angiogenic factors in the pathogenesis of the maternal syndrome of preeclampsia and related disorders.

Exercise training attenuates placental ischemia-induced hypertension and angiogenic imbalance in the rat

An imbalance between proangiogenic (vascular endothelial growth factor) and antiangiogenic (soluble fms-like tyrosine kinase 1) factors plays an important role in hypertension associated with reduced uteroplacental perfusion (RUPP). Exercise has been shown to stimulate proangiogenic factors, such as vascular endothelial growth factor, in both the pregnant and nonpregnant state; thus, we hypothesized that exercise training would attenuate both angiogenic imbalance and hypertension attributed to RUPP. Four groups of animals were studied, RUPP and normal pregnant controls and normal pregnant and RUPP+exercise training. Exercise training attenuated RUPP-induced hypertension (P<0.05), decreased soluble fms-like tyrosine kinase 1 (P<0.05), increased VEGF (P<0.05), and elevated the soluble fms-like tyrosine kinase 1:vascular endothelial growth factor ratio. The positive effects of exercise on angiogenic balance in the RUPP rats were confirmed by restoration (P<0.05) of the RUPP-induced decrease in endothelial tube formation in human umbilical vascular endothelial cells treated with serum from each of the experimental groups. Placental prolyl hydroxylase 1 was increased (P<0.05) in RUPP+exercise training rats. Decreased trolox equivalent antioxidant capacity in the placenta, amniotic fluid, and kidney of the RUPP rats was reversed by exercise. RUPP-induced increase in renal thiobarbituric acid reactive species was attenuated by exercise. The present data show that exercise training before and during pregnancy attenuates placental ischemia-induced hypertension, angiogenic imbalance, and oxidative stress in the RUPP rat and reveals that increased prolyl hydroxylase 1 is associated with decreased soluble fms-like tyrosine kinase 1, thus revealing several potential pathways for exercise training to mitigate the effects of placental ischemia-induced hypertension. Lastly, the present study demonstrates that exercise training may be a useful approach to attenuate the development of placental ischemia-induced hypertension during pregnancy.

Hypertensive disorders of pregnancy: preventative-, immediate- and long-term management

The hypertensive disorders of pregnancy are common and continue to be significant contributors to maternal and perinatal mortality and morbidity, both globally and in the UK. This review aims to describe the recent developments in the understanding of the pathophysiology of the disease processes, potential strategies for identification of women at high risk, and current and future therapeutic strategies for the treatment and prevention of hypertension in pregnancy. Women who experience adverse pregnancy outcomes are also at increased risk of premature cardiovascular disease, and potential therapeutic strategies to minimize their risk profile are discussed.

Effects of angiogenic factors, antagonists, and podocyte injury on development of proteinuria in preeclampsia

Proteinuria is universal to all patients with preeclampsia. We examined the urinary podocytes in women with preeclampsia (n = 14), gestational hypertension (n = 14), and normal pregnancy. Maternal serum and urinary concentrations of vascular endothelial growth factor (VEGF), placental growth factor (PlGF), and the antiangiogenic factor soluble fms-like tyrosine kinase 1 (sFlt-1) were detected. These concentrations were used to evaluate the urinary excretion of podocytes and the alteration of angiogenic factors and to assess their relationships to proteinuria in preeclampsia. Our studies suggest that the urinary podocyte number and angiogenic factors are correlated with random urine albumin/creatinine ratio and blood pressure. Receiver-operating characteristic (ROC) curves of serum and urinary PlGF and the PlGF/sFlt-1 ratio as well as the presence of podocyturia confirmed their usefulness in distinguishing preeclamptic and normotensive pregnant women. In addition, combinations of serum or urinary PlGF or podocyturia tests in parallel or in series provided the best clue for identifying patients with preeclampsia. We considered that the dysregulation of angiogenic factors and its subsequent podocyte injury may contribute to the mechanism of proteinuria development in preeclampsia.

Comparison of angiogenic and anti-angiogenic factors in maternal and umbilical cord blood in early- and late-onset pre-eclampsia

PURPOSE

The aim of this study was to compare maternal and umbilical cord serum levels of the angiogenic and anti-angiogenic factors in early- and late-onset pre-eclamptic pregnancies as well as in normal pregnancies, which might have significant importance in the etiology of pre-eclampsia.

MATERIALS AND METHODS

This prospective case-control study was carried out with pre-eclamptic (early-onset, ≤ 34 weeks and late-onset, >34 weeks) and normal pregnant women. VEGF, PIGF, sFlt-1 and sEng levels in maternal and umbilical cord serum were measured before delivery and the findings were compared.

RESULTS

The study was conducted with 15 early- and 15 late-onset pre-eclampsia patients, and 17 patients with normal pregnancies. It was found that sEng levels were higher in the umbilical cord serum in the early-onset and in the maternal serum in the late-onset pre-eclampsia group than the control group (p < 0.05). No significant difference in any factor was observed between the early- and late-onset pre-eclampsia groups.

CONCLUSION

In this study, the results showed that angiogenic and anti-angiogenic factor levels in maternal serum and umbilical cord serum may not be related to the time of onset of pre-eclampsia.

Agonistic autoantibodies to the angiotensin II type I receptor cause pathophysiologic characteristics of preeclampsia

BACKGROUND

Preeclampsia (PE), new-onset hypertension with proteinuria during pregnancy, is associated with increased reactive oxygen species, the vasoactive peptide endothelin-1 (ET-1), T and B lymphocytes, soluble antiangiogenic factors sFlt-1 and sEndoglin (sFlt-1 and sEng), and agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA).

OBJECTIVES

One important area of investigation for our laboratory was to determine what role AT1-AA plays in the pathophysiology associated with PE.

METHODS

To achieve this goal, we examined the effect of AT1-AA suppression on hypertension in response to placental ischemia as well as the effect of AT1-AA on increased blood pressure, ET-1, reactive oxygen species, and sFlt-1 in normal pregnant rats (NP).

RESULTS

We demonstrated reductions in uterine perfusion pressure (RUPP) to be a stimulus for AT1-AA during pregnancy. We utilized the technique of B-cell depletion to suppress circulating AT1-AA in RUPP rats and found that AT1-AA suppression in RUPP rats was associated with lower blood pressure and ET-1 activation. To determine a role for AT1-AA to mediate hypertension during pregnancy, we infused purified rat AT1-AA (1:50) into NP rats, and analyzed blood pressure and soluble factors. We consistently found that AT1-AA infused rats had significantly increased AT1-AA and blood pressure above NP rats. This hypertension was associated with significantly increased ET-1 in renal cortices (11-fold) and placenta (4-fold), and there was an approximately 2- to 3-fold increase in placental oxidative stress. Furthermore, antiangiogenic factors sFlt-1 and sEng were significantly increased in the AT1-AA induced hypertensive group compared with the NP controls.

CONCLUSIONS

Collectively, these data indicated an important role for AT1-AA stimulated in response to placental ischemia that caused hypertension during pregnancy.

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.

First trimester serum angiogenic/anti-angiogenic status in twin pregnancies: relationship with assisted reproduction technology

BACKGROUND

The risk of pre-eclampsia (PE) increases in twin pregnancies, especially when assisted reproduction technologies (ART) are used. The aim of this study was to assess angiogenic/anti-angiogenic factors in maternal serum in the first trimester of twin pregnancies and establish if the mode of conception influences angiogenic status.

METHODS

This prospective study enrolled women with twin (n = 61) and singleton (n = 50) pregnancies. Dichorionic twin pregnancies were divided into two groups according to their mode of conception. Singleton pregnancies were used as the control group. Soluble fms-like tyrosine kinase (sFlt-1), free placental growth factor (PlGF) and soluble endoglin (sEng) concentrations were measured in the first trimester maternal serum.

RESULTS

In the first trimester, women with twin pregnancies had higher serum concentrations of the anti-angiogenic factor sFlt-1 than that with singleton pregnancies (3924 ± 250 versus 2426 ± 162 pg/ml, respectively; P < 0.001). Maternal serum PlGF concentrations were lower in singleton pregnancies than those in twin pregnancies (37 ± 3.7 versus 59 ± 5.6, respectively; P < 0.001). Serum concentrations of sFlt-1 were higher in twin pregnancies conceived by ART than those in spontaneous twin pregnancies (4313 ± 389 versus 3522 ± 300 pg/ml, respectively; P < 0.05). No differences between groups were observed for sEng.

CONCLUSIONS

In the first trimester, twin pregnancies conceived using ART showed a heightened anti-angiogenic status that could explain the increased risk of PE in these cases.

L-arginine supplementation abolishes the blood pressure and endothelin response to chronic increases in plasma sFlt-1 in pregnant rats

While soluble fms-like tyrosine kinase-1 (sFlt-1) and endothelin-1 (ET-1) have been implicated in the pathogenesis of preeclampsia (PE), the mechanisms whereby increased sFlt-1 leads to enhanced ET-1 production and hypertension remain unclear. It is well documented that nitric oxide (NO) production is reduced in PE; however, whether a reduction in NO synthesis plays a role in increasing ET-1 and blood pressure in response to chronic increases in plasma sFlt-1 remains unclear. The purpose of this study was to determine the role of reduced NO synthesis in the increase in blood pressure and ET-1 in response to sFlt-1 in pregnant rats. sFlt-1 was infused into normal pregnant (NP) Sprague-Dawley rats (3.7 μg·kg(-1)·day(-1) for 6 days beginning on day 13 of gestation) treated with the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (100 mg/l for 4 days) or supplemented with 2% L-Arg (in drinking water for 6 days beginning on day 15 of gestation). Infusion of sFlt-1 into NP rats significantly elevated mean arterial pressure compared with control NP rats: 116 ± 2 vs. 103 ± 1 mmHg (P < 0.05). NO synthase inhibition had no effect on the blood pressure response in sFlt-1 hypertensive pregnant rats (121 ± 3 vs. 116 ± 2 mmHg), while it significantly increased mean arterial pressure in NP rats (128 ± 4 mmHg, P < 0.05). In addition, NO production was reduced ∼70% in isolated glomeruli from sFlt-1 hypertensive pregnant rats compared with NP rats (P < 0.05). Furthermore, prepro-ET-1 in the renal cortex was increased ∼3.5-fold in sFlt-1 hypertensive pregnant rats compared with NP rats. Supplementation with L-Arg decreased the sFlt-1 hypertension (109 ± 3 mmHg, P < 0.05) but had no effect on the blood pressure response in NP rats (109 ± 3 mmHg) and abolished the enhanced sFlt-1-induced renal cortical prepro-ET expression. In conclusion, a reduction in NO synthesis may play an important role in the enhanced ET-1 production in response to sFlt-1 hypertension in pregnant rats.

Stability of first trimester placental growth factor in serum and whole blood

BACKGROUND

Placental growth factor (PlGF) is a proposed first-trimester screening marker for pre-eclampsia. This study investigates the stability of PlGF in serum and whole blood at typical routine storage temperatures.

METHODS

Serum pools were stored at refrigerator temperature, room temperature or 30 °C for up to 30 days, or exposed to up to six freeze-thaw cycles. Whole blood was stored at room temperature or 30 °C for up to 6 days. PlGF was quantified using a DELFIA Xpress analyser.

RESULTS

Placental growth factor levels increased over time, seemingly because of the dissociation of PlGF bound to a soluble binding protein, sFlt-1. Increase was slow in serum at refrigerator temperature, remaining stable (less than 10% change from start point) for at least 30 days. At room temperature PlGF was stable for 3.3 days and at 30 °C for 1 day. Serum PlGF remained stable for at least six freeze-thaw cycles. In whole blood, instability was worse, being stable for only 19.4 h at room temperature and just 3.3 h at 30 °C.

CONCLUSION

Routine screening of sample handling requires careful monitoring. However, no extra precautions need to be taken when PlGF is used for pre-eclampsia screening run alongside existing first trimester aneuploidy screening programs that include hCGβ.

A single rapid point-of-care placental growth factor determination as an aid in the diagnosis of preeclampsia

OBJECTIVES

To evaluate the clinical performance of a rapid point-of-care test, Triage PLGF (Alere, San Diego) in the diagnosis of preeclampsia.

STUDY DESIGN

For the reference range 2212 plasma samples were collected from 595 subjects with normotensive pregnancies, between week 17 of gestation and delivery. In the case-control part, two cohorts of women with preeclampsia (80 women) were matched for maternal age, gestational age (GA) at sampling and parity with normotensive women who delivered at 37weeks or more.

RESULTS

The areas under the receiver operating characteristic curves (GA<35weeks) were 1.0 and 0.994 (cohort 1 and 2, respectively). The clinical sensitivity of the Triage PLGF test for the pooled GA range of 21⩽GA<35, using a GA dependent cut-off, was 1.0 for both cohorts with specificities of 1.0 and 0.940.

CONCLUSIONS

The Triage PLGF test distinguishes well between preterm pregnancies with and without preeclampsia.

Chemokines plasma levels in preterm newborns of preeclamptic mothers

Information on leukocyte activation in newborn infants of preeclamptic mothers is scarce. IL-8 and GRO-α are the main pro-inflammatory cytokines involved in leukocyte activation. The objective was to evaluate IL-8 and GRO-α plasma levels in preterm newborns infants of preeclamptic mothers. Newborns with gestational age<36 weeks and birth weight<2000 g were included and divided: non-preeclamptic (n=64) and preeclamptic groups (n=55). Exclusion criteria were major congenital malformations, inborn errors of metabolism or chromosomal anomalies, congenital infections, death in delivery room, and maternal chronic hypertension without preeclampsia. IL-8 and GRO-α were measured by enzyme immunoassay in the first 48 h. Groups were similar in birth weight, gestational age, Apgar scores at 5 min, sepsis, RDS, mechanical ventilation, TPN, NEC, intraventricular hemorrhage and death. The preeclamptic group had more neutropenia, SGA, cesarean section, and less rupture of membranes>18 h. IL-8 was higher in the non-preeclamptic [157.1 pg/mL (86.4-261.3) and 26.54 pg/mL (3.6-87.2) p<0.001]. GRO-α levels were similar in both groups [229.5 pg/mL (116.6-321.3) and 185.5 pg/mL (63.9-306.7) p=0.236]. After multiple regression analysis only absence of preeclampsia was associated with high IL-8 levels. Our data suggest that leukocyte activation may be impaired in infants of preeclamptic mothers.

C-reactive protein levels in early pregnancy, fetal growth patterns, and the risk for neonatal complications: the Generation R Study

OBJECTIVE

We sought to examine the associations of maternal C-reactive protein (CRP) levels with fetal growth and the risks of neonatal complications.

STUDY DESIGN

CRP levels were measured in early pregnancy in 6016 women. Main outcome measures were fetal growth in each trimester and neonatal complications.

RESULTS

As compared to the reference group (CRP levels<5 mg/L), elevated maternal CRP levels (≥25 mg/L) were associated with lower estimated fetal weight in third trimester and lower weight at birth (differences: -29 g, 95% confidence interval [CI], -58 to 0 and -128 g, 95% CI, -195 to -60, respectively). Elevated maternal CRP levels were also associated with an increased risk of a small size for gestational age in the offspring (adjusted odds ratio, 2.94; 95% CI, 1.61-5.36).

CONCLUSION

Maternal CRP levels in early pregnancy are associated with fetal growth restriction and increased risks of neonatal complications.

Maternal iNOS genetic polymorphisms and hypertensive disorders of pregnancy

Increased expression and activity of inducible nitric oxide synthase (iNOS) may contribute to the pathogenesis of pre-eclampsia (PE) and gestational hypertension (GH). However, no previous study has examined whether genetic polymorphisms in the iNOS gene are associated with PE or GH. We examined whether two functional, clinically relevant iNOS genetic polymorphisms (the C(-1026)A polymorphism, rs2779249, in the promoter region, and the G2087A polymorphism, rs2297518, in exon 16) are associated with GH or with PE. We studied 565 pregnant women: 212 healthy pregnant (HP), 166 pregnant with GH and 187 pregnant with PE. Genotypes were determined by real-time PCR, using the Taqman allele discrimination assay. The PHASE 2.1 program was used to estimate haplotype distributions in the three study groups. We found no significant association between the C(-1026)A polymorphism and PE or GH (P>0.05). However, we found the GA genotype and the A allele for the G2087A polymorphism at higher frequency in PE, but not in GH, compared with HP (P<0.05). The haplotype analysis showed no significant intergroup differences (P>0.05). These findings suggest that iNOS genetic variants may affect the susceptibility to PE, but not to GH.

Levels of soluble fms-like tyrosine kinase one in first trimester and outcomes of pregnancy: a systematic review

Angiogenic factors are involved in formation of new blood vessels required for placental development and function; and critical for fetal growth and development. Soluble fms-like tyrosine kinase 1(sFlt-1) is an anti-angiogenic protein that inhibits formation of new blood vessels resulting in potential pregnancy complications. The objective of this study was to undertake a systematic review to assess levels of sFlt-1 in early pregnancy and association with adverse pregnancy outcomes. PubMed and Medline databases and reference lists were searched up to July 2010. Inclusion criteria were pregnant women, blood sample taken during first trimester and assessment/reporting of sFlt-1 concentrations and subsequent pregnancy complications. Twelve relevant studies were identified of 71 to 668 women. No pooling of results was undertaken due to variation in sFlt-1 concentrations (range, 166-6,349 pg/ml amongst controls), samples used (serum, plasma), different summary statistics (mean, median, odds ratio) and outcome definitions applied. Levels of sFlt-1 were generally higher among women who developed preeclampsia (11 studies) or gestational hypertension (two studies), but not significantly different to normotensive women in most studies. There was no consistent pattern in association between sFlt-1 concentrations and fetal growth restriction (4 studies); and levels were non-significantly higher for women with postpartum bleeding (1 study) and significantly lower for stillbirths (1 study).This review found no clear evidence of an association between sFlt-1 levels in first trimester and adverse pregnancy outcomes. However, findings were affected by methodological, biological and testing variations between studies; highlighting the need for consistent testing of new biomarkers and reporting of outcome measures.

Silica and titanium dioxide nanoparticles cause pregnancy complications in mice

The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.

The role of serum markers and uterine artery Doppler in identifying at-risk pregnancies

Measures of placental dysfunction, including maternal serum analytes and Doppler studies, have been linked to adverse pregnancy outcomes, although the predictive ability of any single one is poor. Improved knowledge of the multifactorial nature of many of the adverse outcomes of pregnancy has sparked interest in the use of multi-parameter models that combine maternal serum analytes with measures of placental structure and blood flow. The combination of various first-trimester and second-trimester analytes and uterine artery Doppler screening show promise as potential screening tools, but large prospective studies are needed to further define their role in clinical practice.

Complement activation and pregnancy failure

Pregnancy represents a physiologic condition where maternal immune system tolerates the semi-allogenic fetus. The fetal tissues are directly exposed to the maternal blood with potential attacks from maternal immune system, including the activation of complement cascade. Small amounts, of both early and late components, of complement are physiologically found in the placenta, maybe in relation to the vascular remodeling process. A significant increase of complement activation was associated with different pathologic pregnancy outcomes, namely pre-eclampsia, recurrent spontaneous abortions, intra-uterine growth retardation, and anti-phospholipid syndrome (APS). In some, but not in all, mice models of APS, complement activation plays a major role in pregnancy loss, with a massive accumulation of C3 in the placenta, while C3 deficient mice didn't show fetal resorption. Basing on these findings, anti-phospholipid antibodies and complement activation (via C3a, C5a, and MAC) may cooperate in triggering a local inflammatory process, eventually leading to placental thrombosis, hypoxia, and neutrophil infiltration. However, histological analysis of human placenta tissues from APS women shows small rather than widespread inflammation. In a similar manner, complement activation can be detected in human APS placentas but without any relationship with pregnancy outcome and therapy. Further studies are necessary to investigate whether complement activation and inflammatory processes found in animal models are really taking place in APS.

Circulating angiogenic and antiangiogenic factors in women with eclampsia

OBJECTIVE

The objective of the study was to determine whether eclampsia has a different circulating profile of angiogenic (placental growth factor [PlGF]) and antiangiogenic factors (soluble vascular endothelial growth factor receptor-1 [sVEGFR-1] and soluble endoglin [sEng]) from severe preeclampsia.

STUDY DESIGN

This cross-sectional study included pregnant women in the following groups: (1) normal pregnancy (n = 40); (2) severe preeclampsia (n = 40); and (3) eclampsia (n = 20). Maternal serum PlGF, sVEGFR-1, and sEng concentrations were determined using an enzyme-linked immunosorbent assay.

RESULTS

The study results included the following: (1) the median concentration of sVEGFR-1 and sEng was higher and of PlGF was lower in severe preeclampsia or eclampsia than in normal pregnancy (P < .001 for all); and (2) the median concentrations of these 3 analytes did not differ significantly between patients with severe preeclampsia and those with eclampsia.

CONCLUSION

Eclampsia is associated with higher maternal circulating concentrations of sVEGFR-1 and sEng and lower concentrations of PlGF than normal pregnancy but with similar concentrations to severe preeclampsia. These findings suggest that eclampsia shares a common pathogenic pathway as severe preeclampsia.

Role of reactive oxygen species during hypertension in response to chronic antiangiogenic factor (sFlt-1) excess in pregnant rats

BACKGROUND

Preeclampsia is associated with increased levels of reactive oxygen species (ROS) and the antiangiogenic factor, soluble fms-like tyrosine kinase-1 (sFlt-1). Moreover, recent studies have indicated that chronic sFlt-1 excess causes hypertension in pregnant animals. The purpose of this study was to evaluate the role of ROS in mediating sFlt-1-induced hypertension in the pregnant rat.

METHODS

Mean arterial pressure (MAP), and plasma sFlt-1 and tissue ROS levels were measured in the following groups: (i) pregnant controls; (ii) sFlt-1-treated pregnant rats; (iii) Tempol-treated pregnant rats; (iv) sFlt-1- and Tempol-treated pregnant rats.

RESULTS

MAP increased from 104 ± 2 mm Hg in pregnant control rats to 118 ± 3 mm Hg (P = 0.002) in sFlt-1-infused rats. Basal and nicotinamide adenine dinucleotide phosphate (NADPH)-stimulated levels of tissue ROS were increased in response to excess sFlt-1 during pregnancy. Pretreatment with Tempol attenuated oxidative stress and hypertension in response to sFlt-1.

CONCLUSIONS

ROS play an important role in mediating hypertension in response to chronic sFlt-1 excess during pregnancy.

Prenatal stretching exercise and autonomic responses: preliminary data and a model for reducing preeclampsia

PURPOSE

Preeclampsia is a leading cause of perinatal mortality and morbidity, and it increases maternal risk for future cardiovascular disease. The purpose of the study was to explore the relationships among stretching exercise, autonomic cardiac response, and the development of preeclampsia.

DESIGN

Secondary data analysis.

METHODS

Heart rate and pulse pressure were longitudinally examined in this secondary data analysis among women who engaged in stretching exercise daily from 18 weeks of gestation to the end of pregnancy compared with women who did walking exercise daily during the same time period. A total of 124 women were randomized to either stretching (n=60) or walking (n=64) in the parent study.

FINDINGS

Heart rates in the stretching group were consistently lower than those in the walking group.

CONCLUSIONS

Based on the results of this secondary data analyses, a physiologic framework for possible beneficial effects of stretching exercise by enhancing autonomic responses on reducing risks for preeclampsia is proposed and discussed.

CLINICAL RELEVANCE

If the protective effect is established, stretching exercise can be translated into nursing intervention for prenatal care.

Regulation of sFlt-1 and VEGF secretion by adenosine under hypoxic conditions in rat placental villous explants

The role of adenosine in the regulation of cardiovascular function has long been acknowledged, but only recently has its importance in angiogenesis been appreciated, most notably, through its direct regulation of the proangiogenic growth factor, VEGF. Recent work has established that proangiogenic and antiangiogenic factors, specifically VEGF and and the soluble VEGF receptor fms-like tyrosine kinase-1 (sFlt-1), are directly influenced by hypoxia in placental ischemia. While adenosine has been reported to be an important regulator of VEGF in vascular tissue, the importance of adenosine in regulating VEGF and sFlt-1 in placental tissue is unclear. Here, we have investigated the role of adenosine in the secretion of VEGF and the antiangiogenic protein sFlt-1 in placental villous explants. Under normoxic conditions (6% oxygen), the nonspecific adenosine receptor antagonist, 8-sulphophenyltheophylline (8-SPT) had no effect on either VEGF (P = 0.38) or sFlt-1 (P = 0.56) secretion. However, under hypoxic conditions (1% oxygen), 8-SPT attenuated the increase in the secretion of both VEGF and sFlt-1 (P < 0.05 and P < 0.005, respectively). Exogenous and the adenosine transporter inhibitor dipyridamole (which increases extracellular levels of adenosine) showed differential effects under normoxic conditions: sFlt-1 levels in media increased significantly (P < 0.05), whereas VEGF was unaffected (P = 0.67 and P = 0.19, respectively). These data indicate that extracellular adenosine can regulate VEGF and sFlt-1 secretion in the hypoxic placenta and could, therefore, control the balance of these competing angiogenic factors in diseases characterized by placental ischemia.

Relation between maternal angiogenic factors and utero-placental resistance in normal first- and second-trimester pregnancies

OBJECTIVE

Soluble endoglin (sEng) is a novel antiangiogenic protein and elevated sEng concentrations in maternal circulation are closely related to preeclampsia and HELLP syndrome. As the perfusion of the uterine arteries as well as the dynamics of angiogenic factors between first and second trimester have prognostic value regarding pregnancy outcome, it was the aim of this study to investigate the relation between maternal angiogenic factors and uterine Doppler parameters.

STUDY DESIGN

The longitudinal study includes 50 normal pregnancies. Pulsatility index (PI) of the uterine arteries was detected by Doppler ultrasound in first and second trimester. In parallel, maternal sEng and soluble fms-like tyrosine kinase 1 (sFlt1) concentration was measured using ELISA.

RESULTS

In the first trimester, the sEng concentrations were 4.92 ± 1.36 ng/mL and the uterine PI was 1.14 ± 0.28. In the second trimester, the maternal sEng concentration decreased significantly to 3.99 ± 0.63 ng/mL (p < 0.05) which was associated by a decrease of the uterine PI to 0.78 ± 0.15 (p < 0.001). Soluble fms-like tyrosine kinase 1 concentrations did not differ significantly between first and second trimester (423 ± 333 vs. 444 ± 291 pg/mL). There was a significant negative correlation between sEng and uterine resistance in the second trimester (r = -0.416; p < 0.001).

CONCLUSIONS

In normal pregnancy, parallel to the fall of utero-placental resistance, there is a physiological decline of the maternal sEng concentration between first and second trimester. In second trimester, there is a negative correlation between sEng and uterine Doppler parameters.

The effect of immune factors, tumor necrosis factor-alpha, and agonistic autoantibodies to the angiotensin II type I receptor on soluble fms-like tyrosine-1 and soluble endoglin production in response to hypertension during pregnancy

BACKGROUND

Preeclampsia is considered a disease of immunological origin associated with abnormalities in inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), and activated lymphocytes secreting autoantibodies to the angiotensin II receptor (AT1-AA). Recent studies have also demonstrated that an imbalance of angiogenic factors, soluble fms-like tyrosine kinase (sFlt-1), and sEndoglin, exists in preeclampsia; however, the mechanisms that initiate their overproduction are unclear.

METHODS

To determine the role of immune regulation of these factors, circulating and placental sFlt-1 and/or sEndoglin was examined from pregnant rats chronically treated with TNF-alpha or AT1-AA. On day 19 of gestation blood pressure was analyzed and serum and tissues were collected. Placental villous explants were excised and cultured on matrigel coated inserts for 24 h and sFlt-1 and sEndoglin was measured from media.

RESULTS

In response to TNF-alpha-induced hypertension, sFlt-1 increased from 180 +/- 5 to 2,907 +/- 412 pg/ml. sFlt-1 was also increased from cultured placental explants of TNF-alpha induced hypertensive pregnant rats (n = 12) (2,544 +/- 1,132 pg/ml) vs. explants from normal pregnant (NP) rats (n = 12) (2,189 +/- 586 pg/ml) where as sEng was undetectable. Circulating sFlt-1 increased from 245 +/- 38 to 3,920 +/- 798 pg/ml in response to AT1-AA induced hypertension. sFlt-1 levels were higher (3,400 +/- 350 vs. 2,480 +/- 900 pg/ml) in placental explants from AT1-AA infused rats (n = 12) than NP rats (n = 7). In addition, sEndoglin increased from 30 +/- 2.7 to 44 +/- 3.3 pg/ml (P < 0.047) in AT1-AA infused rats but was undetectable in the media of the placental explants.

CONCLUSIONS

These data suggest that immune factors may serve as an important stimulus for both sFlt-1 and sEndoglin production in response to placental ischemia.

First-trimester assessment of placenta function and the prediction of preeclampsia and intrauterine growth restriction

Preeclampsia and intrauterine growth restriction (IUGR) are major contributors to perinatal mortality and morbidity worldwide. Both are characterized by impaired trophoblastic invasion of the maternal spiral arteries and their conversion from narrow muscular vessels to wide non-muscular channels. Despite improvement in the understanding of the pathophysiology of these conditions, ability to accurately identify pregnant woman who will develop them is limited. This greatly impairs the development and testing of preventive interventions. While different measures of placental dysfunction have been associated with increased risk for adverse pregnancy outcomes, the ability of any single one to accurately predict these outcomes is poor. Developing predictive tests is further challenged by difficulty in the timing of the measurements, as both the structural and biochemical characteristics of the placenta change with increasing gestational age. The ideal screening test would accurately predict the development of adverse pregnancy outcomes early enough to provide a window for preventive interventions. Improvement in ultrasound technology provides potentially useful novel tools for evaluating placental structure, but measurements need to be standardized in order to be useful. Maternal serum analyte screening is a noninvasive test of placental biochemical function, but present serum marker alone is not sufficiently accurate to suggest its routine use in clinical practice. The use of first trimester biochemical markers in combination with uterine artery Doppler screening is promising as a potential screening tool. Prospective longitudinal studies using standardized methodology are necessary to further evaluate the choice of parameters and strategies of combination to achieve the best predictive models.

Lipid levels including oxidized LDL in women with history of preeclampsia

Preeclampsia (PE), a leading cause of maternal and perinatal morbidity and mortality worldwide, is a hypertensive disorder of unknown aetiology characterized by proteinuria, coagulation abnormalities and different systemic manifestations. Since there are no studies regarding the evaluation of oxidized LDL (oxLDL) in women with a history of PE, we focused on the evaluation of lipid profile and oxLDL plasma concentration several years after pregnancy to see if these women have any modifications in these parameters that may be linked to the risk of cardiovascular disease (CVD) in the future. Ninety women with a history of PE and 60 controls in a median interval of 6 years after pregnancy were recruited. Plasma oxLDL levels were measured using a two-site enzyme immunoassay. Concentration of cholesterol, triglycerides (TG), HDL-cholesterol (HDLc) and LDL-cholesterol (LDLc) were measured by automated enzymatic assays. To evaluate apoA and apoB levels automated immunoturbidimetric assays were used. In the group of women with a history of PE, gestational age at delivery was significantly earlier in comparison with the control group, whereas birth weight was significantly lower and there were more caesarean sections. Systolic and diastolic blood pressures were significantly higher in women with a history of PE than in the control group. Significantly higher obesity anthropometric markers (BMI and waist-to-hip ratio) were found in women with a history of PE. As consistent with other authors' findings, blood pressure was higher in these women, but lipid profile did not seem to play a role in the increased risk of cardiovascular disease.

Dysregulated complement activation as a common pathway of injury in preeclampsia and other pregnancy complications

The complement system protects the host against invading organisms, initiates inflammation and dispose of immune complexes and the products of inflammatory injury. The complement system provides an important link between the innate and adaptive immune systems. Experimental observations suggest that increased complement activation causes and/or perpetuates inflammation during pregnancy. Recent studies suggest a link between complement activation and preeclampsia. Excessive activation or insufficient regulation of complement recruits leukocytes and unleashes potent inflammatory and anti-angiogenic mediators associated with placental insufficiency and maternal endothelial dysfunction characteristic of preeclampsia. We review the animal and human studies that link complement activation and pathogenic events in preeclampsia, present evidence that activation of the complement system is associated with the development of preeclampsia and provides new targets to prevent its complications.

Multicenter evaluation of the first automated Elecsys sFlt-1 and PlGF assays in normal pregnancies and preeclampsia

OBJECTIVES

Performance evaluation of Elecsys sFlt-1 and PlGF assays.

DESIGN AND METHODS

Within-, between-run, total imprecision, functional sensitivity, inter-laboratory comparison, method comparison and lot-to-lot reproducibility were evaluated.

RESULTS

Within- and between-run CVs were below 4% for sFlt-1 >60 and PlGF > 20 pg/mL. Total imprecision CVs were below 4.3%. Functional sensitivity was < 5 pg/mL. Inter-laboratory CVs were <5%. Elecsys correlated well with Quantikine VEGF-R1 (r=0.960) and PlGF (r=0.968). Lot-to-lot comparisons yielded highly correlated results (r>0.999). In healthy pregnancies, the median levels of sFlt-1 remained constant in first (1107 pg/mL) and second trimesters (1437 pg/mL) but increased in the third trimester (2395 pg/mL), while median PlGF levels increased in the first (30 pg/mL) and second trimesters (279 pg/mL) and peaked at 29 to 32 weeks (626 pg/mL) and decreased thereafter (340 pg/mL). The sFlt-1/PlGF ratio is highest in the first trimester (median: 28) but remained constant in the second (median: 4.7) and third trimesters (median: 5.1). In PE/HELPP samples matched for gestational age the sFlt-1 levels were significantly higher (6894-34,624 pg/mL), whereas PlGF levels were lower (9.2-80 pg/mL) and the median sFlt-1/PlGF ratio is much higher (461; range: 121-2614) than in apparently healthy pregnancies (3.6; range: 0.3-105).

CONCLUSION

The new Roche Elecsys sFlt-1 and PlGF immunoassay showed excellent precision and reliability. There was a clear difference in the Elecsys sFlt-1/PlGF ratio between samples obtained from women with apparently normal pregnancy at the time of blood collection and those diagnosed with PE/HELLP at the same age of gestation.

Change in amniotic fluid levels of multiple anti-angiogenic proteins before development of preeclampsia and intrauterine growth restriction

CONTEXT

The cause of preeclampsia remains unknown. Excessive antiangiogenic proteins have been proposed to play a pathogenic role in preeclampsia.

OBJECTIVE

Our objective was to determine the differences in soluble endoglin (sEndoglin), soluble fms-like tyrosine kinase receptor-1 (sFLT1), leptin, adiponectin, and endothelin 1 concentrations between normal and preeclampsia amniotic fluid (AF). Such results may help us understand the pathophysiology of preeclampsia.

METHODS

We performed a nested case-control study. Seventy-one women with preeclampsia were matched to 71 normotensive controls. The preeclamptic women were broken into two subgroups according to the association with fetal intrauterine growth restriction (IUGR). AF concentrations of sEndoglin, sFLT1, leptin, adiponectin, and endothelin 1 were measured by ELISA. Receiver-operating characteristics curve analysis was used to compare the discriminative values of these potential biomarkers. Functional network analysis was performed using MetaCore to reveal the common functions of the interacting proteins.

RESULTS

Increased AF concentrations of sFLT1, sEndoglin, endothelin 1, and leptin were found in women who later developed preeclampsia. sFLT1, sEndoglin, leptin, and adiponectin were significantly higher in the preeclampsia with IUGR than those without IUGR. Leptin has the largest area under the curve (0.753). Network analysis revealed that elevated amniotic proteins are involved in the inflammatory process of the human placenta.

CONCLUSIONS

Significant elevation of leptin can be detected in AF 2 months earlier than the appearance of symptoms; thus, it may be used as a predictive marker for preeclampsia. The increase of these antiangiogenic proteins supports the roles of inflammation and oxidative stress in pathogenesis of preeclampsia.

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

OBJECTIVES

To determine the gene expression profile in chorionic villous samples (CVS) of women destined to develop preeclampsia.

METHOD

cDNA microarray technology was employed. Ten singleton fetuses of women who subsequently developed preeclampsia where compared with a pool of 50 controls. The mRNA expression of some of the genes previously found to be up- or down-regulated were validated by RT-PCR in peripheral blood from 23 pregnant women at term affected with preeclampsia and 23 controls.

RESULTS

Altered expression was found among several genes including those involved in invasion of human trophoblasts (Titin), in inflammatory stress (Lactotransferrin), endothelial aberration (Claudin 6), angiogenesis (Vasohibin 1), blood pressure control (Adducin 1). Also the peripheral blood from preeclampsia patients showed significant differences for all the genes studied.

CONCLUSION

CVS show an aberrant gene profile prior to preeclampsia onset that may be predictive of the disease.

An automated method for the determination of the sFlt-1/PIGF ratio in the assessment of preeclampsia

OBJECTIVE

The angiogenic and antiangiogenic factors soluble fms-like tyrosine kinase (sFlt)-1 and placental growth factor (PIGF) have been implicated in the mechanisms of disease responsible for preeclampsia (PE). Moreover, it has been proposed that the concentrations of these markers in maternal serum/plasma may have predictive value. This study evaluates a newly developed Elecsys (Roche, Penzberg, Germany) assay for sFlt-1 and PIGF and tests the value of the sFlt-1/PIGF ratio in the assessment of PE.

STUDY DESIGN

This multicenter case-control study included 351 patients: 71 patients with PE and 280 gestational age-matched control subjects from 5 European study centers. A total of 595 serum samples were measured for sFlt-1 and PIGF using an automated platform.

RESULTS

Maternal serum concentrations of sFlt-1 and PIGF significantly separated healthy women and women with PE. The sFlt-1/PIGF ratio had an area under the receiver operating characteristic curve of 0.95. The best performance was obtained in the identification of early-onset PE (area under the receiver operating characteristic curve of 0.97).

CONCLUSION

Measurement of sFlt-1 and PIGF and calculation of sFlt-1/PIGF ratio can be performed quickly and in a platform available in clinical laboratories. This is a substantial step forward in bringing the determination of these analytes to clinical practice in obstetrics. We propose that sFlt-1, PIGF, and sFlt-1/PIGF ratio may be of value in the prediction of PE and in the differential diagnosis of patients with atypical presentations of PE, and perhaps in the differential diagnosis of women with chronic hypertension suspected to develop superimposed PE.

Angiogenic dysfunction in molar pregnancy

OBJECTIVE

Molar pregnancy is associated with very early-onset preeclampsia. Since excessive circulating antiangiogenic factors may play a pathogenic role in preeclampsia, we hypothesized that molar placentas produce more antiangiogenic proteins than normal placentas.

STUDY DESIGN

This retrospective case-control study used a semiquantitative immunohistochemical technique to compare histologic sections of molar placentas to normal controls. Tissue slides were treated with 2 antisera: one recognized the antiangiogenic markers fms-like tyrosine kinase receptor 1 (Flt1) and its soluble form (sFlt1), while the other recognized vascular endothelial marker CD31. Stain intensity was graded from 1+ (strong focal staining) to 4+ (91-100% staining).

RESULTS

Molar placentas (n = 19) showed significantly more staining than controls (n = 16) for Flt/sFlt1 (P < .0001).

CONCLUSION

There was a significant difference in Flt1/sFlt1 immunostaining intensity when molar placentas were compared to controls. This supports a hypothesis that the phenotype of preeclampsia in molar pregnancy may result from trophoblasts overproducing at least 1 antiangiogenic protein.