Maternal serum angiopoietin-1 and -2 and tie-2 in early pregnancy ending in preeclampsia or intrauterine growth retardation

Maternal serum angiopoietins levels in pre-eclampsia and pregnancy outcomes

Background and Aims

Although the understanding of pre-eclampsia (PE) has improved, there is still insufficient knowledge on the exact etiology and pathophysiological mechanisms. Dysregulation of angiogenic factors has emerged as a significant contributing factor. Among these factors, angiopoietins (Ang-1 and Ang-2) have gained considerable attention due to their crucial role in regulating vascular development and endothelial function. This study explored the maternal serum levels of angiopoietins and perinatal outcomes in PE.

Methods

A case-control study involving women with PE (cases) and normotensive pregnancies (controls) was conducted at the Maternity unit of the Korle-Bu Teaching Hospital. Descriptive analysis was performed and the Mann-Whitney U test (two-sided) was used to compare maternal serum levels of angiopoietins between the cases and controls.

Results

We included 188 participants comprising 94 cases (women with PE) and 94 controls (normotensive pregnancies) with an average maternal age of 29.76 ± 5.56 and 28.43 ± 5.57 years, respectively. Maternal serum levels of Ang-2 were significantly lower among the PE cases compared to the normotensive controls (1.25 [0.90, 2.15] vs. 2.14 [1.18, 5.73] ng/mL, p = 0.001) but no significant difference in Ang-1 levels (92.61 [80.92, 114.92] vs. 99.26 [81.76, 113.12] ng/mL, p = 0.429) was observed between the groups. The Ang-1/Ang-2 ratio was significantly elevated among women with PE compared to normotensive controls (74.47 [37.69, 110.59] vs. 45.98 [16.11, 88.22] ng/mL, p = 0.014). Also, women who delivered vaginally had significantly high maternal serum levels of Ang-1 compared to women who had cesarean section delivery (107.98 ± 27.79 vs. 89.02 ± 32.62 ng/mL).

Conclusion

Maternal serum levels of Ang-2 but not Ang-1 were significantly depressed in women with PE compared to the pregnant normotensive controls. No significant associations were observed between Ang-1, Ang-2 levels, or the Ang-1/Ang-2 ratio and pregnancy outcomes such as preterm birth, birth weight, and severity of hypertension.

Influential Serum Kinases (Non-sFlt-1) and Phosphatases in Preeclampsia-Systemic Review and Metanalysis

The early identification of women with an increased risk of preeclampsia (PE) is desirable, but apart from soluble fms-like tyrosine kinase-1 (sFlt-1), few biomarkers have previously been identified as relevant for predicting preeclampsia. Since kinases and phosphatases regulate critical biological processes and previous evidence suggests a potential role of these molecules in preeclampsia, we performed this systematic review and metanalysis. The objective was to determine if there are kinases and phosphatases whose serum levels are different between women with and without PE, being relevant biomarkers of PE. We followed the recommendations of Cochrane and the Preferred Reported Items for Systematic Reviews and Metanalysis (PRISMA) to perform this study. The MESH terms preeclampsia, kinases, phosphatases, angiopoietins, soluble tyrosine protein kinase receptor (sTIE2), and cellular-mesenchymal-epithelial transition factor (c-MET) were combined to find relevant articles in the PubMed, PROSPERO, and Cochrane databases. Then, a qualitative and quantitative analysis was performed in R Studio software. From 580 abstracts identified, 37 were included in the final analysis, which comprised 24,211 pregnant women (2879 with PE and 21,332 women without PE [HP]. The pooled analysis showed that serum creatine kinase (CK) (SMD: 2.43, CI 95% 0.25-4.62) was significantly higher in PE, whereas sTIE2 and anti-angiogenic factor soluble c-Met (sMet)were significantly lower in PE than in HP (SMD: -0.23, CI95% -0.37 to -0.09; and SMD:0.24, CI95% 0.01-0.47, respectively). Adenosine monophosphate-activated protein kinase (AMPK), angiopoietin-1 (ANG-1), angiopoietin-2 (ANG-2), the ratio angiopoietin-1/angiopoietin-2, acid phosphatase, and alkaline phosphatase were not different between women with PE and HP. In summary CK, sTIE2, and c-MET are relevant biomarkers of PE. It is desirable to incorporate them into current models for PE prediction to evaluate their utility as biomarkers.

Mitochondrial dysfunction-induced high hCG associated with development of fetal growth restriction and pre-eclampsia with fetal growth restriction

Fetal growth restriction (FGR) and pre-eclampsia with fetal growth restriction (PE/FGR) are high-risk perinatal diseases that may involve high levels of human chorionic gonadotropin (hCG) and mitochondrial dysfunction. However, little is known about how these factors affect placental function. We investigated how mitochondrial dysfunction and high hCG expression affected placental function in unexplained FGR and PE/FGR. We observed elevated expression of hCGβ and growth differentiation factor 15 mRNA and protein levels in the placenta with both diseases. Likewise, antiangiogenic factors, such as Ang2, IP10, sFlt1, IL8, IL1B, and TNFα, were also upregulated at the mRNA level. In addition, the expression of COXI and COXII which encoded by mitochondrial DNA were significantly decreased in both diseases, suggesting that mitochondrial translation was impaired. Treatment with hCG increased Ang2, IP10, IL8, and TNFα mRNA levels in a dose-dependent manner via the p38 and JNK pathways. Mitochondrial translation inhibitors increased hCGβ expression through stabilization of HIF1α, and increased IL8 and TNFα mRNA expression. These results revealed that high expression of hCG due to mitochondrial translational dysfunction plays an important role in the pathogenesis of FGR and PE/FGR.

Mid trimester amniotic fluid soluble receptor tunica interna endothelial cell kinase-2 levels and risk for preeclampsia

OBJECTIVES

The purpose of this study was to determine if elevated concentration of soluble receptor tunica interna endothelial cell kinase-2 (Tie-2) in the amniotic fluid represent a risk factor for the subsequent development of preeclampsia (PE).

STUDY DESIGN

Amniotic fluid samples were collected as a part of routine clinical diagnostics from women referred to clinical care due to genetic indications. A total of 12 women with preeclampsia and 26 normotensive pregnant women were included in the study. Mean gestational age at amniocentesis was 17.92 weeks of pregnancy in preeclampsia and 17.88 in control group, respectively. Concentrations of sTie-2 in the amniotic fluid were determined by a standardized enzyme immunoassay.

RESULTS

Median concentration of Tie-2 in the amniotic fluid of PE patients was lower (median 1.109 ng/ml) compared with normotensive pregnant women (median 1.433 ng/Ml) but the difference was not statistically significant (p = 0.2973). Concentration of sTie-2 in the amniotic fluid did not significantly correlate with maternal age, gestational age at amniocentesis or delivery, as well as weight or length at birth. A difference in the gestational age at delivery in PE patients (mean 37.7 weeks) and normotensive pregnant controls (mean 39.8 weeks) was statistically significant (p = 0.0003). Birth weight and length of children delivered by PE women (mean 2863.3 g and 48.3 cm) were significantly lower compared with normal pregnancies (mean 3591.2 g and 51.4 cm, p = 0.0002 and p = 0.006, respectively).

CONCLUSION

Our results suggest that amniotic fluid concentrations of sTie-2 do not predict development of PE and that further studies on biomarkers as predictors of PE should include other angiogenic biological response modifiers.

The Angiopoietin-Tie2 axis contributes to placental vascular disruption and adverse birth outcomes in malaria in pregnancy

Background

Malaria during pregnancy is a major contributor to the global burden of adverse birth outcomes including fetal growth restriction, preterm birth, and fetal loss. Recent evidence supports a role for angiogenic dysregulation and perturbations to placental vascular development in the pathobiology of malaria in pregnancy. The Angiopoietin-Tie2 axis is critical for placental vascularization and remodeling. We hypothesized that disruption of this pathway would contribute to malaria-induced adverse birth outcomes.

Methods

Using samples from a previously conducted prospective cohort study of pregnant women in Malawi, we measured circulating levels of angiopoietin-1 (Angpt-1) and Angpt-2 by Luminex (n=1392). We used a preclinical model of malaria in pregnancy (Plasmodium berghei ANKA [PbA] in pregnant BALB/c mice), genetic disruption of Angpt-1 (Angpt1^+/− mice), and micro-CT analysis of placental vasculature to test the hypothesis that disruptions to the Angpt-Tie2 axis by malaria during pregnancy would result in aberrant placental vasculature and adverse birth outcomes.

Findings

Decreased circulating levels of Angpt-1 and an increased ratio of Angpt-2/Angpt-1 across pregnancy were associated with malaria in pregnancy. In the preclinical model, PbA infection recapitulated disruptions to the Angiopoietin-Tie2 axis resulting in reduced fetal growth and viability. Malaria decreased placental Angpt-1 and Tie2 expression and acted synergistically with reduced Angpt-1 in heterozygous dams (Angpt1^+/−), to worsen birth outcomes by impeding vascular remodeling required for placental function.

Interpretation

Collectively, these data support a mechanistic role for the Angpt-Tie2 axis in malaria in pregnancy, including a potential protective role for Angpt-1 in mitigating infection-associated adverse birth outcomes.

Funding

This work was supported by the Canadian Institutes of Health Research (CIHR), Canada Research Chair, and Toronto General Research Institute Postdoctoral Fellowship Award. The parent trial was supported by the European & Developing Countries Clinical Trials Partnership and the Malaria in Pregnancy Consortium, which was funded by the Bill & Melinda Gates Foundation. The funders had no role in design, analysis, or reporting of these studies.

Relationship between second-trimester amniotic fluid and plasma levels of angiopoietin-2 and thrombomodulin with adverse pregnancy outcome

Our objective is to investigate maternal midtrimester plasma and amniotic fluid (AF) levels of angiopoietin-2 (Ang-2) and thrombomodulin (TM), which are involved in vascular remodelling and endothelium activation, in placental disorders including foetal growth restriction (FGR) and preeclampsia (PE). This prospective multiparametric pilot study was conducted at the Perinatology Division of Trakya University in a population undergoing genetic amniocentesis. Both AF and plasma aliquots were kept in -80 °C until ELISA assay. The pregnancies were followed up until the end of gestation in terms of obstetric results. Amniotic fluid and plasma aliquots from 127 pregnancies who underwent genetic amniocentesis between 16 and 24 weeks of gestation were analysed. During the final data evaluation, 39 were excluded with various reasons. Twelve subsequently developed FGR and 11 complicated with PE. The control group (n = 65) was consisted of women delivered >37th week with an uncomplicated outcome. The midtrimester maternal Ang-2 levels in both AF and plasma and also TM levels in plasma were found to be significantly increased in pregnancies who subsequently developed FGR or PE (p< .05). The midtrimester Ang-2, which rises in both plasma and AF and the midtrimester TM, which only significantly increase in plasma compartment in PE group, as compensatory mechanism may be the precursors of placental disorders including FGR and PE.Impact StatementWhat is already known on this subject? It is known that angiopoietin-2 (Ang-2) has important role in placental angiogenesis and vascular remodelling. TM which is a receptor for Ang-2 plays a protective role in pregnancy by preventing the uteroplacental circulation from thrombosis.What do the results of this study add? The present study demonstrates that both midtrimester maternal plasma Ang-2/TM and amniotic fluid (AF) Ang-2 levels were significantly higher in PE and FGR group than uncomplicated group. Midtrimester AF TM levels were not significantly higher in PE group than the control group.What the implications are of these findings for clinical practice and/or further research? In the clinical practice, high levels of midtrimester Ang-2 and TM in plasma may be used for the prediction of FGR and PE. Although amniocentesis is not practical in the clinical use, the levels of these two markers in both AF and plasma compartments may contribute to explain the pathophysiology of FGR and PE.

Angiopoietin 2 stimulates trophoblast invasion via a mechanism associated with JNK signaling

Extravillous trophoblast cell (EVT) invasion is tightly controlled, and its dysregulation can lead to altered spiral artery remodeling and contribute to a number of different pregnancy complications. Angiopoietin-2 (Ang-2) is expressed by trophoblast cells and various cells in the decidua, and trophoblast cells express its receptor, Tie2. Ang-2 has been shown to play roles in tumor progression and metastasis but it is not known if it also regulates EVT invasion. Here, we show that both the HTR-8/SVneo cell line and primary isolates of human EVT expressed various integrins and the Tie2 receptor, and Ang-2 stimulated their migration and/or invasion. Ang-2 increased expression of matrix metalloproteinase (MMP)2 and MMP9, altered the cytoskeleton of HTR-8/SVneo cells and also induced phosphorylation of Tie2, JNK and c-Jun. Inhibition of p-JNK (using SP600125) blocked the Ang-2 induced invasion of HTR-8/SVneo cells. In addition, inhibition of Tie2 (pexmetinib) and integrin signaling (RGDS and ATN-161) also blocked Ang-2-induced invasion. In conclusion, we demonstrate that Ang-2 can stimulate EVT invasion via a mechanism associated with activation of both the Tie2 receptor and integrins, which appear to work through different pathways; Tie2 through the JNK/c-JUN pathway and integrins through an as yet unidentified pathway(s). We therefore propose that any alterations in Ang-2 expression in the decidua would lead to an imbalance in pro- and anti-invasive factors, disrupting regulation of EVT invasion and spiral artery remodeling and thereby contribute to the etiology of several complications of pregnancy.

Functional Evaluation of STOX1 (STORKHEAD-BOX PROTEIN 1) in Placentation, Preeclampsia, and Preterm Birth

Revaluation of the association of the STOX1 (STORKHEAD_BOX1 PROTEIN 1) transcription factor mutation (Y153H, C allele) with the early utero-vascular origins of placental pathology is warranted. To investigate if placental STOX1 Y153H genotype affects utero-vascular remodeling-compromised in both preterm birth and preeclampsia-we utilized extravillous trophoblast (EVT) explant and placental decidual coculture models, transfection of STOX1 wild-type and mutant plasmids into EVT-like trophoblast cell lines, and a cohort of 75 placentas from obstetric pathologies. Primary EVT and HTR8/SVneo cells carrying STOX1 Y153H secreted lower levels of IL (interleukin) 6, and IL-8, and higher CXCL16 (chemokine [C-X-C motif] ligand 16) and TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) than wild-type EVT and Swan71 cells. Media from wild-type EVT or Swan71 cells transfected with wild-type STOX1 stimulated: endothelial chemokine expression, angiogenesis, and decidual natural killer cell and monocyte migration. In contrast, Y153H EVT conditioned medium, Swan71 transfected with the Y153H plasmid, or HTR8/SVneo media had no effect. Genotyping of placental decidual cocultures demonstrated association of the placental STOX1 CC allele with failed vascular remodeling. Decidual GG NODAL R165H increased in failed cocultures carrying the placental CC alleles of STOX1. Multivariate analysis of the placental cohort showed that the STOX1 C allele correlated with premature birth, with or without severe early-onset preeclampsia, and small for gestational age babies. In conclusion, placental STOX1 Y153H is a precipitating factor in preterm birth and placental preeclampsia due to defects in early utero-placental development.

Placental expression of angiogenesis-related genes and their receptors in IUGR pregnancies: correlation with fetoplacental and maternal parameters

Objectives: Aberrations in placental vascular development compromising fetal supply of oxygen and essential nutrients can be a significant contributor to intrauterine growth restriction (IUGR). The development of placental vascular tree is under the influence of two families of growth factors, namely the vascular endothelial growth factor (VEGF) family and angiopoietin/TEK family. In this study, we have examined the expression of angiogenesis-related growth factors, mainly VEGF family and angiopoietin-TEK (endothelial-specific receptor tyrosine kinase) family genes in placentae from IUGR pregnancies uncomplicated by preeclampsia (PE) compared to normal pregnancies.Methods: Placentae from normotensive IUGR (n = 42) and appropriate for gestational age (AGA) pregnancies (n = 47) were collected and examined histologically. Clinical parameters were obtained from the medical records. Real-time quantitative PCR was performed to assess placental transcript abundance of VEGF, PGF, FLT1, ANGPT1, ANGPT2, and TEK normalized to a panel of reference genes. Associations of placental transcript abundance of the genes with maternal, placental, and neonatal parameters were tested.Results: Placental transcript abundance for VEGF (relative expression 10.81 versus 12.98, p < .001), PGF (12.14 versus 13.8, p < .001) and ANGPT2 (3.67 versus 9.55, p = .002) were significantly lower in IUGR placentae compared to AGA. The transcript level of VEGF showed significant negative correlation with birth weight (r = -0.419, p = .006), placental weight (r = -0.318, p = .040), placental length (r = -0.389, p = .011) and breadth (r = -0.308, p = .047) only in the IUGR group. Presence of histopathological features of hypoxia correlated with significantly higher transcript levels of PGF in IUGR placentae (12.6 versus 10.9, p = .046).Conclusion: The low levels of VEGF transcripts may be responsible for the impaired angiogenesis in IUGR placentae. The significance of higher relative expression of PGF in the presence of chronic hypoxia needs to be explored.

Association of Angiopoietin Dysregulation in Placental Malaria with Adverse Birth Outcomes

Malaria in pregnancy causes adverse birth outcomes due to sequestration of Plasmodium falciparum-infected erythrocytes in the placenta. Angiopoietins are critical regulators of vascular development and formation of placental villous vasculature. Angiopoietin-1 and Angiopoietin-2 concentrations were measured in peripheral and placental plasma samples from 70 malaria-infected and 216 control women using commercially available DuoSet ELISA development kit. Angiopoietins increased in placental plasma (ANG1-5833.5 pg/ml and ANG2-9580.6 pg/ml) as compared to peripheral plasma (ANG1-2293.1 pg/ml and ANG2-1198.9 pg/ml, p < 0.0001). The concentration of placental and peripheral ANG1 (6099.23 pg/ml and 2320.5 pg/ml) was significantly lower (5013.5 pg/ml, 2208.5 pg/ml), and ANG2 (9553.3 pg/ml, 1180.92 pg/ml) was significantly higher (9664.6 pg/ml, 1254.4 pg/ml) in malaria-positive cases as compared to malaria-negative (p < 0.0001). The association of dysregulated angiopoietins in malaria with adverse birth outcomes showed that the peripheral and placental ANG1 concentration was lower and ANG2 concentration was higher in low-birth-weight baby and stillbirth birth outcome as compared to normal deliveries among malaria-positive group. Therefore, ANG1 and ANG2 could be considered a biomarker for adverse outcome during malaria in pregnancy.

A Review of Angiogenic Imbalance in HIV-Infected Hypertensive Disorders of Pregnancy

PURPOSE OF REVIEW

This review provides a comprehensive insight into the angiogenic profile of hypertensive and normotensive pregnancies compromised by HIV infection. Furthermore, we evaluate the economic implementation of the sFlt-1/PlGF ratio and review the reports on therapeutic apheresis in limiting sFlt-1 production.

RECENT FINDINGS

In preeclampsia, an increased expression of sFlt-1 triggers angiogenic imbalance. Women of African ancestry have high levels of angiogenic factors than other racial groups. The sFlt-1/PlGF ratio shows promise in the early assessment of preeclampsia, while sFlt-1 apheresis restores angiogenic imbalance. Studies suggest antiretroviral therapy does not impact the angiogenic shift in preeclampsia development. The angiogenic profile in pregnant women of different races influences preeclampsia development. Despite the opposing immune response in HIV infection and preeclampsia, the HIV tat protein strongly mimics vascular endothelial growth factor (VEGF); hence, it is plausible to assume that HIV infection may ameliorate the angiogenic imbalance in preeclampsia.

Role of plasma PlGF, PDGF-AA, ANG-1, ANG-2, and the ANG-1/ANG-2 ratio as predictors of preeclampsia in a cohort of pregnant women

INTRODUCTION

Preeclampsia affects 3-5% of pregnancies worldwide and is the primary cause of maternal-fetal and neonatal mortality. Previous studies show that alterations in maternal concentrations of angiogenic factors, such as PlGF, PDGF AA, ANG-1, and ANG-2, may play fundamental roles in the pathophysiology of the disease.

OBJECTIVE

Determine whether the PlGF, PDGF AA, ANG-1, and ANG-2 are predictors of preeclampsia occurrence in a prenatal cohort study.

PATIENTS AND METHODS

This is a case-control study associated with a prospective cohort of pregnant women, with gestational ages between 20 and 25 weeks, composed of 30 pregnant women with preeclampsia (PE) and 90 healthy pregnant women (HP). The plasma concentrations of the markers were determined using the ELISA method. The comparison between the case and control groups was performed using the t test on the SAS® 9.4 software. Also, ROC curves were constructed to evaluate the predictive potential of the biomarkers.

RESULTS

Differences in the concentrations of PlGF, PDGF AA, ANG-1 and ANG-2, and the ANG-1/ANG-2 ratio were not observed between the PE and the HP groups. The predictive capacity of the biomarkers was assessed using ROC curves, in which the area under the curve for PlGF AUC = 0.55; PDGF AA AUC = 0.55; ANG-1 AUC = 0.47; ANG-2 AUC = 0.51, and the ANG-1/ANG-2 ratio AUC = 0.57.

CONCLUSION

In pregnant women, with gestational ages between 20 and 25 weeks significant differences in biomarker concentrations between groups PE and HP were not observed. The ROC curves showed that the biomarkers were ineffective as preeclampsia predictors in the analyzed cohort.

First trimester placental vascularization and angiogenetic factors are associated with adverse pregnancy outcome

BACKGROUND

Hypertensive disorders, fetal growth restriction and preterm birth are major obstetrical complications and are related to impaired placentation. Early identification of impaired placentation can advance clinical care by preventing or postpone adverse pregnancy outcome.

OBJECTIVES

Determine whether sonographic assessed placental vascular development and concomitant changes in inflammation- and/or angiogenesis-related serumproteins differ in the first trimester between uncomplicated pregnancies and pregnancies with adverse outcome.

STUDY DESIGN

This prospective longitudinal study defines adverse pregnancy outcome as conditions associated with impaired placentation; fetal growth restriction, hypertensive disorder, preterm birth and placental abruption. The vascularization index, flow index, vascularization flow index and placental volume were determined at 8, 10 and 12 weeks pregnancy from 64 women using 3D power Doppler. Serum levels were analyzed for Angiopoetin-1 and -2, Leptin, VEGF-R, VEGF, and EGF.

RESULTS

The vascularization index and vascular flow index increased in uneventful pregnancies with almost 50% between 8 and 12 weeks, resulting in a ∼50% higher vascularization index at 12 weeks compared to women with an adverse pregnancy outcome. Women with an adverse pregnancy outcome (n = 13) had significantly lower indices and placental volumes at all time points measured and these indices did not increase between 8 and 12 weeks. Reduced vascular development was associated with increased Angiopoietin-1 levels at 8 and 12 weeks and increased Leptin levels at 8 weeks.

CONCLUSIONS

Pregnancies with an adverse outcome caused by conditions associated with impaired placentation differ from uneventful pregnancies in having reduced placental vascularization accompanied by elevated circulating levels of Angiopoietin-1 and Leptin already in the first trimester.

Performance of first trimester biochemical markers and mean arterial pressure in prediction of early-onset pre-eclampsia

OBJECTIVE

To develop a predictive risk model for early-onset pre-eclampsia (EO-PE) using maternal characteristics, combined screening markers, previously reported biomarkers for PE and mean arterial pressure (MAP).

METHODS

This retrospective study was conducted at Oulu University hospital between 2006 and 2010. Maternal serum from first trimester combined screening was further analyzed for alpha fetoprotein (AFP), placental growth factor (PlGF), soluble tumor necrosis factor receptor-1 (sTNFR1), retinol binding protein-4 (RBP4), a disintegrin and metalloprotease-12 (ADAM12), soluble P-selectin (sP-selectin), follistatin like-3 (FSTL3), adiponectin, angiopoietin-2 (Ang-2) and sex hormone binding globulin (SHBG). First, the training sample set with 29 cases of EO-PE and 652 controls was developed to study whether these biomarkers separately or in combination with prior risk (maternal characteristics, first trimester pregnancy associated plasma protein-A (PAPP-A) and free beta human chorionic gonadotrophin (fβ-hCG)) could be used to predict the development of EO-PE. Second, the developed risk models were validated with a test sample set of 42 EO-PE and 141 control subjects. For the test set MAP data was also available.

RESULTS

Single marker statistically significant (ANOVA p<0.05) changes between control and EO-PE pregnancies were observed with AFP, RBP4 and sTNFR1 with both training and test sample sets. Based on the test sample set performances, the best detection rate, 47% for a 10% false positive rate, was achieved with PlGF and sTNFR1 added with prior risk and MAP.

CONCLUSION

Based on our results, the best first trimester biomarkers to predict the subsequent EO-PE were AFP, PlGF, RBP4 and sTNFR1. The risk models that performed best for the prediction of EO-PE included prior risk, MAP, sTNFR1 and AFP or PlGF or RBP4.

Expression of factors involved in the regulation of angiogenesis in the full-term human placenta: Effects of in vitro fertilization

The effects of assisted reproductive technologies (ARTs) on the safety of pregnancy and the resulting offspring remain controversial. Studies of placental functions, especially vasculogenesis and angiogenesis, in pregnancies established through ART are helpful for furthering our understanding of the safety of ART. This study compares the expression profiles of angiogenic factors in human term placentas obtained from natural (NAT) pregnancies vs. placentas obtained from pregnancies that resulted from ART. Term placentas were obtained from women who underwent an ART procedure (n=4), and these were compared with term placentas that were obtained from women who had experienced a spontaneous pregnancy (controls, n=4). An array analysis was performed using the Human Angiogenesis Antibody Array to detect 43 angiogenic factors and to identify which of these factors were differentially expressed between the two groups. The expression of six of these factors was greater in the ART group than in the NAT group. The levels of four of them, including vascular endothelial growth factor receptor-3 (VEGFR3), basic fibroblast growth factor (bFGF), interferon gamma (IFNG) and matrix metalloproteinase 1 (MMP1), were quantified using western blot analysis. These factors were examined using immunohistochemistry and microscopy in vascular endothelial cells or the cytoplasm and membranes of syncytiotrophoblast cells. Our finding that selected angiogenic factors exhibit altered expression profiles in ART placentas might be significant when evaluating ART safety.

Combination of serum angiopoietin-2 and uterine artery Doppler for prediction of preeclampsia

The aim of this study was to determine the predictive value of the combination of serum angiopoietin-2 (Ang-2) levels and uterine artery Doppler for the detection of preeclampsia in women at 16-18 weeks of gestation and to identify other pregnancy complications that could be predicted with these combined tests. Maternal serum Ang-2 levels were measured, and uterine artery Doppler was performed in 400 pregnant women. The main outcome was preeclampsia. The predictive values of this combination were calculated. Twenty-five women (6.3%) developed preeclampsia. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of uterine artery Doppler combined with serum Ang-2 levels for the prediction of preeclampsia were 24.0%, 94.4%, 22.2% and 94.9%, respectively. For the prediction of early-onset preeclampsia, the sensitivity, specificity, PPV and NPV were 57.1%, 94.1%, 14.8% and 99.2%, respectively. Patients with abnormal uterine artery Doppler and abnormal serum Ang-2 levels (above 19.5 ng ml(-1)) were at higher risk for preterm delivery (relative risk=2.7, 95% confidence interval 1.2-5.8). Our findings revealed that the combination of uterine artery Doppler and serum Ang-2 levels at 16-18 weeks of gestation can be used to predict early-onset preeclampsia but not overall preeclampsia. Thus, this combination may be a useful early second trimester screening test for the prediction of early-onset preeclampsia.

Role of the angiopoietin/Tie system in pregnancy (Review)

Angiopoietin-1 and -2 are endogenous ligands for the vascular endothelium-specific receptor tyrosine kinase Tie-2. The angiopoietin/Tie system plays a critical role in the regulation of endothelial cell survival and vascular maturation and stability. Apart from its well-established role in vascular morphogenesis, emerging data support the involvement of angiopoietins in inflammation and various malignancies. Previous studies have underlined the significance of several angiogenic factors in normal placental development. In addition, angiogenic imbalance is observed in pregnancy complications related to impaired placentation, such as preeclampsia (PE) and intrauterine growth restriction (IUGR). However, there is only limited information available on the role of the angiopoietin/Tie system in the establishment of a competent feto-maternal vascular system. In this review, we present the current knowledge regarding the role of angiopoietins in normal pregnancy and pregnancy complications.

Midtrimester maternal plasma concentrations of angiopoietin 1, angiopoietin 2, and placental growth factor in pregnant women who subsequently develop preeclampsia

OBJECTIVE

The aim of this study was to compare midtrimester maternal plasma concentrations of angiopoietin 1, angiopoietin 2, and placental growth factor between pregnant women who subsequently developed preeclampsia and those who did not.

METHODS

Midtrimester maternal plasma was collected and stored at -70℃ when genetic amniocentesis was performed. Cases included 37 samples of individual who subsequently developed preeclampsia, and matched controls were from individuals who did not develop preeclampsia. Angiopoietin 1, angiopoietin 2, and placental growth factor concentrations were measured by the enzyme-linked immunosorbent assay method and were compared using the Mann-Whitney U-test. A P-value <0.05 was considered significant.

RESULTS

In pregnant women who subsequently developed preeclampsia, midtrimester maternal plasma concentrations of angiopoietin 1 and angiopoietin 2 were significantly higher and placental growth factor concentrations were significantly lower than in women who did not develop preeclampsia (angiopoietin 1: 10.6 [3.1-19.7] vs. 7.8 [0.9-24.4] ng/mL, P=0.031; angiopoietin 2: 31.0 [4.7-81.2] vs. 18.4 [4.2-49.7] ng/mL, P<0.001; placental growth factor: 87.1 [14.2-774.3] vs. 148.8 [57.2-425.6] pg/mL, P<0.001). Within the case group who subsequently developed preeclampsia, the placental growth factor was significantly lower in those who had fetal growth restrictions than in those who did not (placental growth factor: 72.5 [14.2-774.3] vs. 140.9 [44.2-257.5] pg/mL, P=0.003).

CONCLUSION

Midtrimester maternal plasma concentrations of angiopoietin 1, angiopoietin 2, and placental growth factor may be associated with the subsequent development of preeclampsia.

Longitudinal changes in maternal soluble endoglin and angiopoietin-2 in women at risk for pre-eclampsia

OBJECTIVE

To investigate longitudinal changes in maternal plasma levels of soluble endoglin (sEng) and angiopoietin-2 (Ang-2) in pregnant women who develop pre-eclampsia (PE) and gestational hypertension (GH).

METHODS

This was a nested case-control study drawn from a larger prospective longitudinal study in singleton pregnancies identified by screening at 11 + 0 to 13 + 6 weeks' gestation as being at high-risk for PE. Blood samples were taken every 4 weeks until delivery. Values were compared in women who developed preterm PE (requiring delivery before 37 weeks), term PE, GH and those who remained normotensive.

RESULTS

A total of 471 samples were analyzed in 122 women, comprising 85 who remained normotensive, 12 who developed GH, 13 who developed term PE and 12 who developed preterm PE. In the normotensive group, there was an increase in log10 sEng levels with gestational age. In the preterm PE group, compared with the normotensive group, sEng was higher from 18 weeks onwards, and the difference increased significantly with gestational age (P < 0.001). In the GH and term PE groups, sEng did not differ significantly from that of the normotensive group (P = 0.583 and P = 0.890, respectively). The square root of Ang-2 decreased significantly with gestational age, but did not differ significantly among the different outcome groups (P = 0.571).

CONCLUSION

Maternal plasma sEng, but not Ang-2, may be a useful mid- and late-gestation biomarker for the development of PE.

Evaluation of first trimester serum soluble endothelial cell-specific tyrosine kinase receptor in normal and affected pregnancies

AIMS

To assess soluble endothelial cell-specific tyrosine kinase receptor (sTie-2) levels in the first trimester of pregnancy and its association with adverse pregnancy outcomes; and examine the predictive accuracy.

STUDY DESIGN

In this nested case-control study, serum sTie-2 levels were measured in 2616 women with singleton pregnancies attending first trimester screening in New South Wales, Australia. Multivariate logistic regression models were used to assess the association and predictive accuracy of serum sTie-2 with subsequent adverse pregnancy outcomes.

RESULTS

Median (interquartile range) sTie-2 for the total population was 19.6 ng/ml (13.6-26.4). Maternal age, weight, and smoking status significantly affected sTie-2 levels. There was no difference in serum sTie-2 between unaffected and women with adverse pregnancy outcomes. After adjusting for maternal and clinical risk factors, low sTie-2 (<25th centile) was associated with preeclampsia (Adjusted odds ratio: 1.61; 95% CI: 1.01-2.57), however, the accuracy of sTie-2 in predicting preeclampsia was not different from chance (AUC = 0.54; p = 0.08) and does not add valuable predictive information to maternal and clinical risk factors.

CONCLUSIONS

Our findings suggest that low sTie-2 levels are associated with preeclampsia, however, it does not add valuable information to clinical and maternal risk factor information in predicting preeclampsia or any other adverse pregnancy outcomes.

Pregnancy-associated plasma protein A (PAPP-A) and preeclampsia

Pregnancy-associated plasma protein A (PAPP-A) is a key regulator of insulin-like growth factor bioavailability essential for normal fetal development. In maternal blood, this protein increases with gestational age and then rapidly decreases after delivery. It is routinely used for Down syndrome screening in the first trimester of pregnancy, and its decrease compared to a normal pregnancy indicates an increased risk for both chromosomal anomalies and adverse pregnancy outcomes. It belongs to a group of biomarkers that predict later preeclampsia development, primarily early onset preeclampsia; however, it should be combined with a Doppler ultrasonography of the uterine artery (pulsatile index) and other biochemical and maternal factors to achieve a higher detection rate with an acceptable false positivity rate. Some studies have demonstrated an even more pronounced decrease of PAPP-A in the early second trimester of pregnancy in women who subsequently develop preeclampsia compared with women who do not develop preeclampsia. Conversely, during the last trimester of pregnancy, its concentration increases even more in patients with preeclampsia than in patients without. It is also detectable at very low levels in nonpregnant individuals, and a higher concentration indicates an adverse effect in patients with acute coronary syndromes or stable atherosclerotic disease and in patients with end-stage renal disease who are being treated with hemodialysis.

Angiopoietin 1 and 2 serum concentrations in first trimester of pregnancy as biomarkers of adverse pregnancy outcomes

OBJECTIVE

To assess angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and the Ang-1/Ang-2 ratio levels in the first trimester of pregnancy, their association with adverse pregnancy outcomes, and their predictive accuracy.

STUDY DESIGN

This cohort study measured serum Ang-1 and Ang-2 levels in 4785 women with singleton pregnancies attending first trimester screening in New South Wales, Australia. Multivariate logistic regression models were used to assess the association and predictive accuracy of serum biomarkers with subsequent adverse pregnancy outcomes (small for gestational age, preterm birth, preeclampsia, miscarriage >10 weeks, and stillbirth).

RESULTS

Median (interquartile range) levels for Ang-1, Ang-2, and the Ang-1/Ang-2 ratio for the total population were 19.6 ng/mL (13.6-26.4), 15.5 ng/mL (10.3-22.7), and 1.21 (0.83-1.73), respectively. Maternal age, weight, country of birth, and socioeconomic status significantly affected Ang-1, Ang-2, and the Ang-1/Ang-2 ratio levels. After adjusting for maternal and clinical risk factors, women with low Ang-2 levels (<10th percentile) and high Ang-1/Ang-2 ratio (>90th percentile) had increased risk of developing most adverse pregnancy outcomes. Compared with the Ang-1/Ang-2 ratio alone, maternal and clinical risk factors had better predictive accuracy for most adverse pregnancy outcomes. The exception was miscarriage (Ang-1/Ang-2 ratio area under receiver operating characteristic curve = 0.70; maternal risk factors = 0.58). Overall, adding the Ang-1/Ang-2 ratio to maternal risk factors did not improve the ability of the models to predict adverse pregnancy outcomes.

CONCLUSION

Our findings suggest that the Ang-1/Ang-2 ratio in first trimester is associated with most adverse pregnancy outcomes, but do not predict outcomes any better than clinical and maternal risk factor information.

Angiopoietin-2 primes infection-induced preterm delivery

Current knowledge on the participation of angiopoietin-2 (Ang-2) in the inflammatory process and on the importance of bacterial endotoxins (LPS) in the induction of preterm delivery (PTD) led us to investigate the role of Ang-2/LPS interplay in the pathogenesis of PTD. At a first stage, Ang-2 was measured at the end of the first trimester of pregnancy in the serum of 50 women who delivered prematurely; of 88 women well-matched for age and parity who delivered full-term; and of 20 non-pregnant healthy women. Ang-2 was greater in pregnant than in non-pregnant women. The time until delivery was shorter among those with Ang-2 greater than 4 ng/ml (odds ratio for delivery until week 34; p: 0.040). To further investigate the role of Ang-2 for PTD, an experimental model of PTD induced by the intraperitoneal injection of LPS in mice was used. Ang-2 was administered intraperitoneally before LPS on day 14 of pregnancy. When Ang-2 was administered before the LPS diluent, all mice delivered full-term. However, administration of Ang-2 prior LPS accelerated further the time until delivery. Sacrifice experiments showed that the effect of Ang-2 was accompanied by decrease of the penetration of Evans Blue in the embryos and by increase of its penetration in maternal tissues. In parallel, the concentration of tumour necrosis factor-alpha in the maternal circulation, in fetal tissues and in the placentas was significantly decreased. Results indicate that Ang-2 accelerated the phenomena of PTD induced by LPS. This is related with deprivation of fetal perfusion.

Placental maturity, hypertensive disorders of pregnancy and birth weight

OBJECTIVES

To compare maturity of placentas from women with hypertensive disorders with those from normotensive pregnancies and to determine the relationship between placental maturity (PM) and the diagnosis of small-for-gestational-age (SGA) in the newborns.

MATERIALS AND METHODS

We examined placental stained specimens from women with normotensive pregnancies (n = 100), diagnosis of gestational hypertension (n = 38), mild (n = 10), or severe preeclampsia (n = 34) in an optical microscope. Placental Maturity Index (PMI) was calculated as the number of vasculo-syncytial membranes (VSM) in 1 mm(2) divided by VSM thickness (µm). Hypermaturity was defined as >90th percentile of the PMI from placentas of normotensive pregnancies. Newborns were classified as SGA, adequate-for-gestational-age (AGA) or large-for-gestational-age (<10th, 10-90th, and >90th percentile from weight for gestational age reference tables, respectively).

RESULTS

PMI in preeclamptic women (taking together mild and severe preeclampsia, PMI = 43.4 ± 1.6) was significantly higher than in normotensive women (PMI = 36 ± 2, p = 0.045). Hypermaturity was more frequent (p < 0.05) in placentas from women with preeclampsia than in those from normotensive women only in preterm pregnancies (<37 weeks), but not in those at term (p = 0.41). The frequency of hypermaturity in placentas from women with gestational hypertension was not statistically different than in normotensive women. Hypermaturity was also more frequent in placentas from SGA (OR = 2.63, p < 0.05) than in AGA newborns.

CONCLUSION

The PMI was increased in preeclampsia, but not in gestational hypertension. Placental hypermaturity was also associated with the diagnosis of SGA in newborns. PM might have a role in the relationship between maternal factors and SGA.

Circulating Vascular Growth Factor (VEGF) Angiopoietin-1 (Angi-1) and Soluble Tie-2 Receptor in Pregnancy Complicated with Pre-eclampsia: A Prospective Study

BACKGROUND

Preeclampsia is a leading cause of maternal and fetal/neonatal mortality and morbidity worldwide. Although the etiology of preeclampsia (PE) is still unclear, recent studies suggest that its major phenotypes, high blood pressure and proteinuria, are due in part to the disturbed angiogenic process.

STUDY DESIGN

This study included the following groups: (1) women with normal pregnancies (n = 150), (2) patients with PE (n = 88), and (3) patients who delivered small growth for date (SGA) neonate (n = 50). Maternal serum concentrations of VEGF, Angi-1, and sTie-2 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

The median maternal serum concentration of sVEGF and sAngi-1 was lower in normal pregnant women as compared to that in PE and SGA and the differences were statistically significant (P < 0.01). In contrast, there is a significant reduction in sTie-2 levels in PE and SGA groups as compared to that in normal pregnancy group (P < 0.01). Serum VEGF and Angi-1 were significantly higher in the late onset PE subgroup as compared to that in the early onset PE (P < 0.01), but sTie-2 was not significantly different in the 2 subgroups (P > 0.05). Serum VEGF, sAngi-1, and sTie-2 were significantly higher and Tie-2 was significantly lower in the severe PE subgroup as compared to that of the milder PE subgroup (P < 0.01 for all).

CONCLUSION

Patients with PE and those with SGA fetuses have lower median serum concentrations of sTie-2 and higher sVEGF and sAngi-1 than women with normal pregnancies. These findings lend support to the hypothesis that circulating angiogenic proteins may have an important biologic role in PE.

Endovascular cooling and endothelial activation in hemorrhagic stroke patients

BACKGROUND

Little is known about endothelial activation under the influence of endovascular temperature management. This analysis was designed to measure the endothelial markers Angiopoietin-1 (Ang-1) and -2 (Ang-2) in endovascularly based prophylactic normothermia versus conventional temperature management.

METHODS

In this randomized controlled trial patients with spontaneous subarachnoid or spontaneous intracerebral hemorrhage were prospectively enrolled and randomized in two treatment arms: (a) prophylactic normothermia group with target core temperature 36.5°C using endovascular cooling, (b) active control group with conventional stepwise predefined fever management using antipyretic medication and surface cooling. Blood samples were obtained on days 1, 4, and 7. In a substudy Ang-1 and -2 were measured in 63 patients for whom samples on consecutive days were available.

RESULTS

The median total fever burden during the course of treatment was 0.0°C and 5.9°C h in the endovascular and the conventional group, respectively (P < 0.0001). Angiopoietin serum levels did not yield a statistical difference when comparing the two treatment arms. Ang-1 was significantly lowered, whereas Ang-2 levels were significantly elevated on day 4 compared to baseline levels irrespective of group allocation (P < 0.0001). The application of non-steroidal anti-inflammatory drugs (NSAIDs) was associated with significantly increased Ang-1 (P < 0.05) and lower Ang-2 levels on day 7 (P < 0.05).

CONCLUSIONS

Endovascular long-term temperature management did not alter Ang-1 and -2 levels compared to the control group indicating that the endovascular cooling technique itself does not lead to additional endothelial impairment. However, application of NSAIDs led to lower Ang-2 serum concentrations in the endovascular group.

Angiopoietin-2 is a potential mediator of endothelial barrier dysfunction following cardiopulmonary bypass

INTRODUCTION

Endothelial activation leading to vascular barrier dysfunction and organ failure is a well-recognized complication of cardiovascular surgery with cardiopulmonary bypass (CPB). The endothelial-specific angiopoietin-Tie2 ligand-receptor system has been identified as a non-redundant regulator of endothelial activation. Binding of angiopoietin-2 (Ang-2) to the Tie2 receptor antagonizes Tie2 signaling and renders the endothelial barrier responsive to pro-inflammatory cytokines. We aimed to study the time course and potential triggering factors of Ang-2 release after CPB, as well as the association of Ang-2 changes with surrogates of increased vascular permeability, organ dysfunction, and outcome.

METHODS

Serum levels of Ang-2 from 25 adult patients (140 screened) were measured before and at 0, 12, and 24h following CPB procedure by in-house immuno-luminometric assay (ILMA), and compared with indices of organ dysfunction, duration of mechanical ventilation (MV), length of stay (LOS) in the intensive care unit (ICU), and hospital mortality. The effect of Ang-2 was studied in vitro by incubating high Ang-2 patient serum with endothelial cells (EC).

RESULTS

Ang-2 levels steadily increased from 2.6 ± 2.4 ng/mL at 0 h up to 7.3 ± 4.6 ng/mL at 24h following CPB (P<0.001). The release of Ang-2 correlated with the duration of CPB, aortic cross-clamp time, and post-CPB lactate levels. Changes in Ang-2 during follow-up correlated with partial pressure of oxygen in arterial blood (PaO(2))/fraction of inspired oxygen (FiO(2)) ratio, alveolar-arterial oxygen tension difference (AaDO(2)), hemodynamics, fluid balance, and disease severity measures. Ang-2 levels at 12h predicted the duration of MV, ICU-LOS, and hospital mortality. High Ang-2 patient sera disrupted EC architecture in vitro, an effect reversed by treatment with the competitive Tie2 ligand angiopoietin-1 (Ang-1).

CONCLUSIONS

Collectively, our results suggest that Ang-2 is a putative mediator of endothelial barrier dysfunction after CPB. These findings suggest that targeting the Ang/Tie2 pathway may mitigate organ dysfunction and improve outcome in patients undergoing CPB.

Significant decrease in maternal serum concentrations of angiopoietin-1 and -2 after delivery

OBJECTIVE

To characterize the physiological distribution of angiopoietins (Ang)-1 and Ang-2 and soluble endothelial cell-specific tyrosine kinase receptor-2 (Tie-2) at term and following delivery.

DESIGN

A prospective, descriptive study.

SETTING

Helsinki University Central Hospital.

POPULATION

Twenty healthy term pregnant women undergoing elective cesarean delivery and their newborns.

METHODS

The concentrations were analysed by enzyme-linked immunosorbent assay in maternal antepartum and the first postpartum day sera, umbilical serum, amniotic fluid and maternal and newborn urine.

MAIN OUTCOME MEASURES

Concentrations of Ang-1, Ang-1 and Tie-2. Results. Concentrations of maternal serum Ang-1 and Ang-2 decreased after delivery {[median (range)]: Ang-1, from 33 (25-51) to 30 (18-49) ng/mL, p= 0.017; and Ang-2, from 5.4 (1.8-18) to 1.4 (0.7-4.6) ng/mL, p < 0.0001}, whereas Tie-2 concentrations remained stable [23 (13-41) vs. 25 (14-29) ng/mL, p= 0.107]. Compared with maternal antepartum serum, umbilical serum concentrations of Ang-1 [46 (28-59) ng/mL, p < 0.0001] and Tie-2 [45 (21-71) ng/mL, p < 0.0001] were higher and those of Ang-2 similar [5.4 (1.8-18) vs. 4.2 (2.9-6.0) ng/mL; p= 0.067]. Low concentrations of Ang-1 [1.2 (0.1-2.2) ng/mL], Ang-2 [1.1 (0.3-4.1) ng/mL] and Tie-2 [0.4 (0.08-0.9) ng/mL] were observed in amniotic fluid, but they were undetectable in newborn urine and in most of the maternal urine samples.

CONCLUSIONS

Maternal Ang-1 and Ang-2 concentrations decreased following delivery. Umbilical concentrations of Ang-1 and Tie-2 were higher than the maternal concentrations.

Airway angiopoietin-2 in ventilated very preterm infants: association with prenatal factors and neonatal outcome

OBJECTIVE

Pulmonary angiogenesis is a prerequisite for lung development. Angiopoietin-2 (Ang2) destabilizes endothelial cells through its endothelial receptor TIE-2, enabling vascular sprouting. Ang1 stabilizes new blood vessels. Soluble TIE-2 (sTIE-2) modulates these effects. We hypothesized that histological funisitis is associated with alterations of Ang2 in airways and of the systemic angiopoietin-TIE-2 homeostasis in very low birth weight (VLBW) infants, contributing to pulmonary morbidity and mortality.

METHODS

We measured Ang2 in tracheobronchial aspirate fluid (TAF) of 42 VLBW <30 weeks of gestation from day 1 through 15 and Ang1, Ang2, and sTIE-2 in umbilical cord serum of 28 infants by enzyme-linked immunosorbent assay. Histological examination distinguished three groups: funisitis, chorioamnionitis, and controls.

RESULTS

Funisitis was associated with lower Ang2 values in TAF but not with changes of Ang1, Ang2, and sTIE-2 in umbilical cord serum. Infants who developed bronchopulmonary dysplasia (BPD) or died had a persistently decreased ratio of previously measured Ang1 to Ang2 in TAF on days 1-5 and increased cord serum concentrations of sTIE-2. Moderate BPD/death was associated with an increase of Ang2 in TAF on day 10 and decreased Ang1/Ang2 ratio from day 3-15. Small for gestational age (SGA) infants had increased Ang2 in TAF on day 1-7 and a lower Ang1/Ang2 ratio on days 5-7.

CONCLUSIONS

The predominance of Ang2 in airway fluid of infants with BPD/death and SGA infants suggests a link between disrupted placental and fetal pulmonary angiogenesis. Histological funisitis with reduced Ang2 in TAF was of minor relevance for outcome in our cohort.

Decreased circulating soluble Tie2 levels in preeclampsia may result from inhibition of vascular endothelial growth factor (VEGF) signaling

OBJECTIVES

Recent studies have found dysregulation in circulating levels of a number of angiogenic factors and their soluble receptors in preeclampsia. In this study, we examined the mechanism of production of soluble Tie2 (sTie2) and its potential connection to the failure of vascular remodeling in preeclamptic pregnancies.

DESIGN/SETTING/PATIENTS

Serum samples were collected prospectively from 41 pregnant subjects at five different time points throughout pregnancy. Five of these subjects developed preeclampsia. For a second study, serum and placental samples were collected at delivery from preeclamptic and gestational age-matched controls. We examined serum sTie2 levels, and angiopoietin 1, angiopoietin 2, and Tie2 mRNA expression and localization in placental samples from the central basal plate area. We also examined the effects of vascular endothelial growth factor (VEGF) and a matrix metalloproteinase (MMP) inhibitor on proteolytic shedding of Tie2 in uterine microvascular endothelial cells.

RESULTS

Serum sTie2 levels were significantly lower in preeclamptic subjects starting at 24-28 wk of gestation and continued to be lower through the time of delivery. In culture experiments, VEGF treatment significantly increased sTie2 levels in conditioned media, whereas the MMP inhibitor completely blocked this increase, suggesting that VEGF-induced Tie2 release is MMP dependent.

CONCLUSIONS

Our data suggest, for the first time, an interaction between VEGF and Tie2 in uterine endothelial cells and a potential mechanism for the decrease in circulating sTie2 levels in preeclampsia, likely through inhibition of VEGF signaling. Further studies on VEGF-Tie2 interactions during pregnancy should provide new insights into the mechanisms underlying the failure of vascular remodeling in preeclampsia and other pregnancy complications.

Angiogenic factors and preeclampsia

Preeclampsia, a hypertensive disorder peculiar to pregnancy, is a systemic syndrome that appears to originate in the placenta and is characterized by widespread maternal endothelial dysfunction. Until recently, the molecular pathogenesis of phenotypic preeclampsia was largely unknown, but recent observations support the hypothesis that altered expression of placental anti-angiogenic factors are responsible for the clinical manifestations of the disease. Soluble Flt1 and soluble endoglin, secreted by the placenta, are increased in the maternal circulation weeks before the onset of preeclampsia. These anti-angiogenic factors produce systemic endothelial dysfunction, resulting in hypertension, proteinuria, and the other systemic manifestations of preeclampsia. The molecular basis for placental dysregulation of these pathogenic factors remains unknown, and as of 2011 the role of angiogenic proteins in early placental vascular development was starting to be explored. The data linking angiogenic factors to preeclampsia have exciting clinical implications, and likely will transform the detection and treatment of preeclampsia.