Performance of a panel of maternal serum markers in predicting preeclampsia at 11–15 weeks' gestation

Integrated Systems Biology Approach Identifies Novel Maternal and Placental Pathways of Preeclampsia

Preeclampsia is a disease of the mother, fetus, and placenta, and the gaps in our understanding of the complex interactions among their respective disease pathways preclude successful treatment and prevention. The placenta has a key role in the pathogenesis of the terminal pathway characterized by exaggerated maternal systemic inflammation, generalized endothelial damage, hypertension, and proteinuria. This sine qua non of preeclampsia may be triggered by distinct underlying mechanisms that occur at early stages of pregnancy and induce different phenotypes. To gain insights into these molecular pathways, we employed a systems biology approach and integrated different "omics," clinical, placental, and functional data from patients with distinct phenotypes of preeclampsia. First trimester maternal blood proteomics uncovered an altered abundance of proteins of the renin-angiotensin and immune systems, complement, and coagulation cascades in patients with term or preterm preeclampsia. Moreover, first trimester maternal blood from preterm preeclamptic patients in vitro dysregulated trophoblastic gene expression. Placental transcriptomics of women with preterm preeclampsia identified distinct gene modules associated with maternal or fetal disease. Placental "virtual" liquid biopsy showed that the dysregulation of these disease gene modules originates during the first trimester. In vitro experiments on hub transcription factors of these gene modules demonstrated that DNA hypermethylation in the regulatory region of ZNF554 leads to gene down-regulation and impaired trophoblast invasion, while BCL6 and ARNT2 up-regulation sensitizes the trophoblast to ischemia, hallmarks of preterm preeclampsia. In summary, our data suggest that there are distinct maternal and placental disease pathways, and their interaction influences the clinical presentation of preeclampsia. The activation of maternal disease pathways can be detected in all phenotypes of preeclampsia earlier and upstream of placental dysfunction, not only downstream as described before, and distinct placental disease pathways are superimposed on these maternal pathways. This is a paradigm shift, which, in agreement with epidemiological studies, warrants for the central pathologic role of preexisting maternal diseases or perturbed maternal-fetal-placental immune interactions in preeclampsia. The description of these novel pathways in the "molecular phase" of preeclampsia and the identification of their hub molecules may enable timely molecular characterization of patients with distinct preeclampsia phenotypes.

Clinical Presentation of Preeclampsia and the Diagnostic Value of Proteins and Their Methylation Products as Biomarkers in Pregnant Women with Preeclampsia and Their Newborns

Preeclampsia (PE) is a disorder which affects 1-10% of pregnant women worldwide. It is characterised by hypertension and proteinuria in the later stages of gestation and can lead to maternal and perinatal morbidity and mortality. Other than the delivery of the foetus and the removal of the placenta, to date there are no therapeutic approaches to treat or prevent PE. It is thus only possible to reduce PE-related mortality through early detection, careful monitoring, and treatment of the symptoms. For these reasons the search for noninvasive, blood-borne, or urinary biochemical markers that could be used for the screening, presymptomatic diagnosis, and prediction of the development of PE is of great urgency. So far, a number of biomarkers have been proposed for predicting PE, based on pathophysiological observations, but these have mostly proven to be unreliable and inconsistent between different studies. The clinical presentation of PE and data gathered for the biochemical markers placental growth factor (PlGF), soluble Feline McDonough Sarcoma- (fms-) like tyrosine kinase-1 (sFlt-1), asymmetric dimethylarginine (ADMA), and methyl-lysine is being reviewed with the aim of providing both a clinical and biochemical understanding of how these biomarkers might assist in the diagnosis of PE or indicate its severity.

Blood laboratory testing for early prediction of preeclampsia: chasing the finish line or at the starting blocks?

Preeclampsia (PE) affects 2-8% of pregnancies worldwide, thus representing an important cause of maternal and neonatal morbidity, up to death. Many studies have been designed to identify putative biomarkers for accurate and timely diagnosing PE, but only some of them were focused on specific and sensitive biomarkers for early prediction of this life-threatening condition. In particular, some prospective studies aimed to investigate the predictive role of circulating biomarkers before 20 weeks of gestation in the general pregnant population yielded conflicting results. This article is hence centered on results obtained in studies investigating the predictive performances of angiogenic, anti-angiogenic, inflammatory, endocrine, and epigenetic biomarkers. The available evidence suggests that angiogenic and anti-angiogenic molecules, in particular the sFlt1:PlGF ratio, may be considered the biomarkers with the best diagnostic performance in the second trimester. However, doubts remain about their use in clinical settings before the 20th gestational week. Even lower evidence is available for other biomarkers, due to the fact that some positive results have not been confirmed in ensuing investigations, whereas unresolved analytical issues still contribute to make their clinical reliability rather questionable. Differential expression of microRNAs seems also a promising evidence for early prediction of PE, but additional research and well-designed prospective studies are needed to identify and validate routine predictive tests. KEY MESSAGES Preeclampsia affects 2-8% of pregnant women worldwide, thus remaining one of the leading causes of maternal and neonatal morbidity and mortality. Several studies have investigated the predictive role of circulating biomarkers before 20th week of gestation with conflicting results. Additional research and well-designed prospective studies are needed to identify and validate predictive tests in clinical practice.

Cardiovascular Complications of Pregnancy

Pregnancy causes significant metabolic and hemodynamic changes in a woman's physiology to allow for fetal growth. The inability to adapt to these changes might result in the development of hypertensive disorders of pregnancy (hypertension, preeclampsia or eclampsia), gestational diabetes and preterm birth. Contrary to previous beliefs these complications are not limited to the pregnancy period and may leave permanent vascular and metabolic damage. There is in addition, a direct association between these disorders and increased risk of future cardiovascular disease (CVD, including hypertension, ischemic heart disease, heart failure and stroke) and diabetes mellitus. Despite abundant evidence of this association, women who present with these complications of pregnancy do not receive adequate postpartum follow up and counseling regarding their increased risk of future CVD. The postpartum period in these women represents a unique opportunity to intervene with lifestyle modifications designed to reduce the development of premature cardiovascular complications. In some cases it allows early diagnosis and treatment of chronic hypertension or diabetes mellitus. The awareness of this relationship is growing in the medical community, especially among obstetricians and primary care physicians, who play a pivotal role in detecting these complications and assuring appropriate follow up.

New directions in the prediction of pre-eclampsia

Pre-eclampsia remains an important worldwide cause of maternal and perinatal morbidity and mortality. Improved prediction of those destined to develop this condition would allow for timely initiation of prophylactic therapy, appropriate antenatal surveillance and better targeted research into preventive interventions. This paper reviews recent research into strategies for the prediction of pre-eclampsia, including the use of maternal risk factors, mean maternal arterial pressure, ultrasound parameters and biomarkers. The most promising strategies involve multiparametric approaches, which use a variety of individual parameters in combination, as has been established in first-trimester aneuploidy screening. The paper concludes with a discussion of the issues around the introduction of such testing into clinical practice.

The obstetric syndromes: clinical relevance of placental hormones

Preterm delivery, preeclampsia and intrauterine growth restriction are the major diseases of pregnancy. A key role in their pathogenesis is played by the placenta, which is the source of hormones and other important regulatory molecules providing the metabolic and endocrine homeostasis of the fetal-placental unit. Since obstetric syndromes are characterized by important maternal and neonatal morbidity and mortality worldwide, numerous efforts have been made over the years to prevent and treat them. Due to their complex pathogenesis, however, the therapy is poor and not very effective. Therefore, great emphasis is currently given to the prevention of these diseases through the identification of biochemical and biophysical markers, among which placental factors play a crucial role. The increasing knowledge of the role of placental molecules can indeed lead to the development of new therapeutic and diagnostic tools.

Can detection of late-onset PE at triage by sflt-1 or PlGF be improved by the use of additional biomarkers?

OBJECTIVE

Accurate identification of preeclampsia (PE) at triage is essential to reduce maternal and fetal morbidity and mortality. The use of maternal blood based biomarkers may facilitate the clinician's ability to assess high risk pregnancies at triage.

METHODS

A prospective cross-sectional study was performed to investigate the value of soluble fms-like tyrosine kinase-1 (sFlt-1), soluble endoglin (sEng), placental growth factor (PlGF), sP-selectin, cell-free fetal DNA and total cell-free DNA in patients with late-onset PE versus gestational age-matched controls.

RESULTS

The diagnosis of late-onset PE (n = 21) at triage was significantly improved by altered levels of sFlt-1, sEng, PlGF and cffDNA as compared with controls (n = 42). Areas under the receiver operating characteristic curves [AUC, Standard error (SE)] for predicting PE were for marker measurements prior to the first stage of labor as follows: sFlt-1 0.97 (SE 0.02), sEng 0.91 (SE 0.04), PlGF 0.95 (SE 0.04), cell-free fetal DNA (DYS 14) 0.84 (SE 0.06), total cell-free DNA (glyceraldehyde 3-phosphate dehydrogenase) 0.61 (SE 0.07), sP-selectin 0.51 (SE 0.07). The discrimination could be slightly improved by using the slt1-PlGF ratio: 0.98 (SE 0.02).

CONCLUSION

The sFlt-1 is a useful tool for the detection of late-onset PE at triage. This can be slightly improved using a sFlt-1/PIGF ratio. The addition of other biomarkers did not improve screening performance for late-onset PE.

Uterine artery Doppler and biochemical markers (PAPP-A, PIGF, sFlt-1, P-selectin, NGAL) at 11 + 0 to 13 + 6 weeks in the prediction of late (> 34 weeks) pre-eclampsia

OBJECTIVE

To determine the performance of screening for late pre-eclampsia (PE) by maternal characteristics, uterine artery Doppler and a set of biochemical markers at 11 + 0 to 13 + 6 weeks' gestation.

METHODS

Prospectively enrolled women at 11 + 0 to 13 + 6 weeks. Maternal characteristics, highest UtA pulsatility index and serum placental biomarkers including pregnancy-associated plasma protein-A, placental growth factor, soluble fms-like tyrosine kinase 1, P-selectin and neutrophil gelatinase-associated lipocalin were recorded.

RESULTS

The rate of PE was 2.5% (13/528). Four (0.8%) had severe PE. A combined screening model that included placental growth factor, soluble fms-like tyrosine kinase 1 and neutrophil gelatinase-associated lipocalin could detect 77% of PE at a 10% false-positive rate. Mean risk for mild PE was 8.8% ± 6.4, mean risk for severe PE was 38.6% ± 4.3. Mean risk for controls was 2% ± 4.1.

CONCLUSION

This combination of maternal biochemical variables in the first trimester can detect a consistent number of late PE. Further studies on a new and independent series of data could confirm the presented results.

Inhibin A, activin A, placental growth factor and uterine artery Doppler pulsatility index in the prediction of pre-eclampsia

OBJECTIVES

To evaluate whether the measurement of maternal serum inhibin A, activin A and placental growth factor (PlGF) at 12 + 0 to 16 + 0 weeks of gestation alone or in combination with second-trimester uterine artery Doppler pulsatility index (PI) is useful in predicting pre-eclampsia.

METHODS

This was a case-control study of pre-eclampsia. From pregnant women attending their first antenatal examination at 12-16 weeks we collected serum samples and stored them at - 80 °C. All patients also underwent uterine artery Doppler examination to measure the PI at 22-24 weeks' gestation. We retrieved for analysis frozen samples from women who then developed pre-eclampsia, as well as three control samples per woman, matched for gestational age and storage time. Inhibin A, activin A and PlGF were measured using an enzyme-linked immunosorbent assay (ELISA) by an examiner who was blinded to the pregnancy outcome.

RESULTS

There were 31 cases with pre-eclampsia and 93 controls. Second-trimester uterine artery PI and marker levels were expressed as multiples of the median (MoM). The uterine artery PI was increased in pregnancies with pre-eclampsia compared with controls (mean ± SD, 1.45 ± 0.31 MoM vs. 1.02 ± 0.25 MoM, P < 0.001), as were the level of inhibin A (mean ± SD, 1.57 ± 0.34 MoM vs. 1.08 ± 0.43 MoM, P < 0.001) and the level of activin A (mean ± SD, 1.68 ± 0.38 MoM vs. 1.06 ± 0.42 MoM, P < 0.001). The level of PlGF was decreased in pre-eclampsia compared with controls (mean ± SD, 0.69 ± 0.23 MoM vs. 1.00 ± 0.26 MoM, P < 0.001). Receiver-operating characteristics curves were analyzed for controls and cases and areas under the curve (AUC) were 0.796 (95% CI, 0.712-0.880, P < 0.001) for inhibin A, 0.823 (95% CI, 0.746-0.899, P < 0.001) for activin A, 0.831 (95% CI, 0.752-0.910, P < 0.001) for PlGF and 0.851 (95% CI, 0.783-0.920, P < 0.001) for uterine artery PI. The combination of activin A, inhibin A and PI using logistic regression analysis yielded an AUC of 0.907 (95% CI, 0.830-0.938, P < 0.001) with a sensitivity of 87% and a specificity of 80%. The combination of activin A, PlGF and PI gave an AUC of 0.925 (95% CI, 0.852-0.978, P < 0.001) with a sensitivity of 90% and a specificity of 80%. Combining all four markers gave an AUC of 0.941 (95% CI, 0.891-0.990, P < 0.001) with a sensitivity of 93% and a specificity of 80%.

CONCLUSION

Early second-trimester serum inhibin A, activin A, PlGF and second-trimester uterine artery Doppler PI may add further information for the prediction of pre-eclampsia. The combination of the three serum markers and uterine artery Doppler PI has the highest prediction value for pre-eclampsia.

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.

Molecular and vascular targets in the pathogenesis and management of the hypertension associated with preeclampsia

Normal pregnancy is associated with significant hemodynamic changes and vasodilation of the uterine and systemic circulation in order to meet the metabolic demands of the mother and developing fetus. Preeclampsia (PE) is one of the foremost complications of pregnancy and a major cause of maternal and fetal mortality. The pathophysiological mechanisms of PE have been elusive, but some parts of the puzzle have begun to unravel. Genetic factors such as leptin gene polymorphism, environmental and dietary factors such as Ca(2+) and vitamin D deficiency, and co-morbidities such as obesity and diabetes may increase the susceptibility of pregnant women to develop PE. An altered maternal immune response may also play a role in the development of PE. Although the pathophysiology of PE is unclear, most studies have implicated inadequate invasion of cytotrophoblasts into the uterine artery, leading to reduced uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia. Placental ischemia induces the release of biologically active factors such as growth factor inhibitors, anti-angiogenic factors, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and antibodies to vascular angiotensin II (AngII) receptor. These bioactive factors could cause vascular endotheliosis and consequent increase in vascular resistance and blood pressure, as well as glomerular endotheliosis with consequent proteinuria. The PE-associated vascular endotheliosis could be manifested as decreased vasodilator mediators such as nitric oxide, prostacyclin and hyperpolarizing factor and increased vasoconstrictor mediators such as endothelin-1, AngII and thromboxane A₂. PE could also involve enhanced mechanisms of vascular smooth muscle contraction including intracellular Ca(2+), and Ca(2+) sensitization pathways such as protein kinase C and Rho-kinase. PE-associated changes in the extracellular matrix composition and matrix metalloproteinases activity also promote vascular remodeling and further vasoconstriction in the uterine and systemic circulation. Some of these biologically active factors and vascular mediators have been proposed as biomarkers for early prediction or diagnosis of PE, and as potential targets for prevention or treatment of the disease.

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.

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.

Potential markers of preeclampsia--a review

Preeclampsia is a leading cause of maternal and fetal/neonatal mortality and morbidity worldwide. The early identification of patients with an increased risk for preeclampsia is therefore one of the most important goals in obstetrics. The availability of highly sensitive and specific physiologic and biochemical markers would allow not only the detection of patients at risk but also permit a close surveillance, an exact diagnosis, timely intervention (e.g. lung maturation), as well as simplified recruitment for future studies looking at therapeutic medications and additional prospective markers. Today, several markers may offer the potential to be used, most likely in a combinatory analysis, as predictors or diagnostic tools. We present here the current knowledge on the biology of preeclampsia and review several biochemical markers which may be used to monitor preeclampsia in a future, that, we hope, is not to distant from today.

Predicting risks of preeclampsia and small for gestational age infant by uterine artery Doppler

OBJECTIVE

To assess the value of uterine artery Doppler as a screening test for preeclampsia and/or having a small-for-gestational-age (SGA) infant in healthy pregnant women.

METHODS

Color Doppler ultrasound was used to examine both uterine arteries in 400 healthy pregnant women at 24.8 +/- 2.0 (range, 22 to 28) weeks of gestation. The mean pulsatility index of both uterine arteries was calculated and the presence of an early diastolic notch in the waveform was noted.

RESULTS

Twenty-six (6.5%) of the 400 women developed preeclampsia and/or had an SGA infant. The optimal cutoff value for the mean pulsatility index in predicting preeclampsia and/or having an SGA infant was 0.857. When using a high mean pulsatility index and/or the presence of any early diastolic notch, the detection of preeclampsia and/or having SGA infant were a sensitivity of 76.9%, a specificity of 52.9%, a positive predictive value of 10.2%, and a negative predictive value of 97.1%, respectively.

CONCLUSION

Women with an abnormal uterine artery Doppler great a considerably higher risk for developing preeclampsia and/or having an SGA infant.

Membrane protected apoptotic trophoblast microparticles contain nucleic acids: relevance to preeclampsia

Microparticles (MPs) that circulate in blood may be a source of DNA for molecular analyses, including prenatal genetic diagnoses. Because MPs are heterogeneous in nature, however, further characterization is important before use in clinical settings. One key question is whether DNA is either bound to aggregates of blood proteins and lipid micelles or intrinsically associated with MPs from dying cells. To test the latter hypothesis, we asked whether MPs derived in vitro from dying cells were similar to those in maternal plasma. JEG-3 cells model extravillous trophoblasts, which predominate during the first trimester of pregnancy when prenatal diagnosis is most relevant. MPs were derived from apoptosis and increased over 48 hours. Compared with necrotic MPs, DNA in apoptotic MPs was more fragmented and resistant to plasma DNases. Membrane-specific dyes indicated that apoptotic MPs had more membranous material, which protects nucleic acids, including RNA. Flow cytometry showed that MPs derived from dying cells displayed light scatter and DNA staining similar to MPs found in maternal plasma. Quantification of maternal MPs using characteristics defined by MPs generated in vitro revealed a significant increase of DNA(+) MPs in the plasma of women with preeclampsia compared with plasma from women with normal pregnancies. Apoptotic MPs are therefore a likely source of stable DNA that could be enriched for both early genetic diagnosis and monitoring of pathological pregnancies.

Maternal serum inhibin-A and activin-A levels in the first trimester of pregnancies developing pre-eclampsia

OBJECTIVE

To evaluate whether measurement of maternal serum inhibin-A and activin-A at 11 + 0 to 13 + 6 weeks of gestation, alone or in combination with second-trimester uterine artery pulsatility measured by Doppler velocimetry, is useful in predicting those women who will develop pre-eclampsia.

METHODS

This was a nested case-control study of pre-eclampsia cases with controls matched for gestational age and storage time for the maternal serum. Samples were collected as part of a first-trimester prenatal chromosomal anomaly screening program. Activin-A and inhibin-A were measured using a commercial enzyme-linked immunosorbent assay and the clinical outcomes were blinded to the operator. All the patients underwent uterine artery Doppler flow velocimetry to measure the mean pulsatility index at 22-24 weeks' gestation.

RESULTS

In total there were 64 cases with pre-eclampsia, with 34 delivering prior to 35 weeks of gestation. The control group included 240 cases. In the control group the levels of activin-A and inhibin-A did not change across the narrow gestational window and the median levels were 2.16 ng/mL and 231.13 pg/mL, respectively. In the pre-eclamptic group levels of activin-A and inhibin-A were significantly increased, at 2.52 ng/mL and 286.64 pg/mL (1.24 multiples of the median (MoM) and 1.17 MoM, respectively). There was no difference in the median MoM in those delivering prior to 35 weeks and those delivering later. At cut-offs of the 90(th) centile of normal, activin-A and inhibin-A levels would have identified 20% and 35%, respectively, of cases that would develop pre-eclampsia. When combined with uterine artery Doppler, activin-A measurement could have increased the detection rate from 55% to 63% and inhibin-A measurement could have increased it to 68% at a 5% false positive rate.

CONCLUSION

Although increased in the first trimester, levels of activin-A and inhibin-A are probably too low to make a significant contribution to screening for pre-eclampsia at this time.