David Carty

Novel biomarkers for predicting preeclampsia.

Preeclampsia is a major cause of maternal morbidity and mortality worldwide. Despite decades of research into the condition, the ability of clinicians to predict preeclampsia prior to the onset of symptoms has not improved significantly. In this review, we will examine the pathophysiology underlying preeclampsia and will look at potential biomarkers for early prediction and diagnosis. In addition, we will explore potential future areas of research into the condition.

Urinary Proteomics for Prediction of Preeclampsia

Preeclampsia is a major determinant of fetal and maternal morbidity and mortality. We used a proteomic strategy to identify urinary biomarkers that predict preeclampsia before the onset of disease. We prospectively collected urine samples from women throughout pregnancy. Samples from gestational weeks 12 to 16 (n=45), 20 (n=50), and 28 (n=18) from women who subsequently had preeclampsia develop were matched to controls (n=86, n=49, and n=17, respectively). We performed capillary electrophoresis online coupled to micro-time-of-flight mass spectrometry. Disease-specific peptide patterns were generated using support vector machine-based software. Candidate biomarkers were sequenced by liquid chromatography-tandem mass spectrometry. From comparison with nonpregnant controls, we defined a panel of 284 pregnancy-specific proteomic biomarkers. Subsequently, we developed a model of 50 biomarkers from specimens obtained at week 28 that was associated with future preeclampsia (classification factor in cases, 1.032±0.411 vs controls, −1.038±0.432; P<0.001). Classification factor increased markedly from week 12 to 16 to 28 in women who subsequently had preeclampsia develop (n=16; from −0.392±0.383 to 1.070±0.383; P<0.001) and decreased slightly in controls (n=16; from −0.647±0.437 to −1.024±0.433; P=0.043). Among the biomarkers are fibrinogen alpha chain, collagen alpha chain, and uromodulin fragments. The markers appear to predict preeclampsia at gestational week 28 with good confidence but not reliably at earlier time points (weeks 12–16 and 20). After prospective validation in other cohorts, these markers may contribute to better prediction, monitoring, and accurate diagnosis of preeclampsia.

Preeclampsia and future maternal health

Preeclampsia is a multisystem disorder that complicates 3–8% of pregnancies in the Western world, and is a major source of morbidity and mortality worldwide. Although it is a disease unique to pregnancy, evidence has mounted in recent years that preeclampsia has important implications for future maternal health, in particular cardiovascular health. In this review we examine epidemiological evidence for this relationship, and examine potential mechanisms such as insulin resistance, genetic factors and endothelial dysfunction that may explain the relationship. In addition we explore potential future avenues of research into the field, such as genomics, proteomics and metabolomics.

Clinical proteomics in obstetrics and neonatology

Clinical proteomics has been applied to the identification of biomarkers of obstetric and neonatal disease. We will discuss a number of encouraging studies that have led to potentially valid biomarkers in the context of Downs syndrome, preterm birth, amniotic infections, preeclampsia, intrauterine growth restriction and obstructive uropathies. Obtaining noninvasive biomarkers (e.g., from the maternal circulation, urine or cervicovaginal fluid) may be more feasible for obstetric diseases than for diseases of the fetus, for which invasive methods are required (e.g., amniotic fluid, fetal urine). However, studies providing validated proteomics-identified biomarkers are limited. Efforts should be made to save well-characterized samples of these invasive body fluids so that many valid biomarkers of pregnancy-related diseases will be identified in the coming years using proteomics based analysis upon adoption of ‘clinical proteomics guidelines’.

Reduced LDL-cholesterol levels in patients with coronary artery disease are paralelled by improved endothelial function: An observational study in patients from 2003 and 2007

Objective Recent guidelines recommend more aggressive lipid-lowering in secondary prevention protocols. We examined whether this resulted in improved endothelial function. Methods We studied saphenous vein specimens of patients undergoing surgical coronary revascularisation in 2007 and compared results with those of patients examined in 2003. Endothelium-dependent vasodilation was assessed by relaxation to calcium ionophore A23187, and vascular superoxide production by lucigenin enhanced chemiluminescence. Results Statin dose increased from 26 ± 16 mg/d in 2003 to 37 ± 17 mg/d in 2007 (P < 0.001), and total (4.0 ± 0.9 mmol/L vs 4.8 ± 1.0 mmol/L) and LDL-cholesterol levels (2.0 ± 0.7 mmol/L vs 3.0 ± 0.9 mmol/L) were lower in 2007 compared to 2003 (P < 0.001; n = 90 each). Endothelium-dependent vasodilation was greater in 2007 (44 ± 15%) compared to 2003 (28 ± 12%; n = 36 each; P < 0.001). Vascular superoxide derived from endothelial NO synthase (eNOS) was lower in 2007 than in 2003 (reduction by NG-nitro-l-arginine-methyl ester, 0.29 ± 0.21 nmol/(mg min) vs 0.09 ± 0.20 nmol/(mg min); P = 0.002). In linear regression analysis, LDL-cholesterol levels have been shown to be the major determinant of endothelial function in the combined 2003 and 2007 cohort. Conclusion Intensive lipid-lowering is associated with improved endothelial function and reduced superoxide production from eNOS. Further improvement in vascular function could be achieved by targeting other sources of superoxide including xanthine oxidase.

Peripheral arterial tone: assessment of microcirculatory function in pregnancy.

Objective Endothelial dysfunction is known to play a key role in the pathogenesis of preeclampsia, but the majority of methods for its detection are too invasive to be used in pregnancy. In this study we report a novel method – peripheral arterial tonometry (PAT) – for examining microcirculatory function in pregnancy. Methods One hundred and eighty women with at least two risk factors for preeclampsia were examined at gestational weeks 16 and 28; 80 women were examined at 6–9 months postnatally. Twenty-four women developed preeclampsia or pregnancy-induced hypertension (cases), 156 remained normotensive (controls). PAT was measured using fingertip pneumatic probes; after baseline recordings the study arm was occluded with a blood pressure cuff then released after 5 min, causing reactive hyperaemia. PAT recordings pre and post occlusion were used to generate the reactive hyperaemia index (RHI). Results RHI was significantly lower at gestational week 28 compared to week 16, both in cases and controls. Baseline pulse amplitude was significantly higher at week 28 compared to week 16. There was no difference in RHI at either week 16 or 28 between cases and controls. Postnatally, there was no difference in RHI between cases and controls, but baseline pulse amplitude was lower in affected women. Conclusion PAT and other methods which rely on flow-mediated dilatation for detection of endothelial dysfunction are less likely to be reliable in later pregnancy, when women are more vasodilated. PAT did not predict the development of hypertensive pregnancy complications, but demonstrated a relative peripheral vasoconstriction in affected women postnatally.

Early pregnancy soluble E-selectin concentrations and risk of preeclampsia.

Objective: Circulating biomarkers of endothelial dysfunction and inflammation are elevated in late pregnancy in women with preeclampsia. We examined plasma levels of inflammatory cytokines and adhesion molecules in early pregnancy, to assess their ability to predict preeclampsia. Methods: In a prospective longitudinal study, 2600 women with singleton pregnancies and no history of hypertension were recruited at their antenatal hospital (booking) visit at gestational week 12–16. Of these, 49 (1.9%) developed preeclampsia, whereas 74 women matched for age and BMI with uncomplicated pregnancies were selected as controls. A subset of women with risk factors for preeclampsia were sampled again at gestational weeks 16 and 28 (11 cases, 39 controls) and postnatally (six cases, 36 controls). Results: From multiplex analysis, soluble E-selectin concentrations were higher at 12–16 weeks in women who subsequently developed preeclampsia (15.1 ± 4.9 versus 12.9 ± 4.5 ng/ml, P = 0.02). At gestational week 28, E-selectin concentrations were again higher in women who went on to develop preeclampsia compared with controls (14.4 ± 5.6 versus 10.7 ± 3.5 ng/ml, P = 0.010), whereas levels were not different between the two groups in postpartum samples. Conclusion: Changes in soluble E-selectin concentration in early pregnancy may reflect underlying pathophysiological processes, potentially providing mechanistic insights into preeclampsia.

Differential expression of microRNA-206 and its target genes in preeclampsia.

Objectives: Preeclampsia is a multisystem disease that significantly contributes to maternal and foetal morbidity and mortality. In this study, we used a nonbiased microarray approach to identify novel circulating miRNAs in maternal plasma that may be associated with preeclampsia. Methods: Plasma samples were obtained at 16 and 28 weeks of gestation from 18 women who later developed preeclampsia (cases) and 18 matched women with normotensive pregnancies (controls). We studied miRNA expression profiles in plasma and subsequently confirmed miRNA and target gene expression in placenta samples. Placental samples were obtained from an independent cohort of 19 women with preeclampsia matched with 19 women with normotensive pregnancies. Results: From the microarray, we identified one miRNA that was significantly differentially expressed between cases and controls at 16 weeks of gestation and six miRNAs that were significantly differentially expressed at 28 weeks. Following qPCR validation, only one miR-206 was found to be significantly increased in 28-week samples in women who later developed preeclampsia (1.4-fold change ± 0.2). The trend for increase in miR-206 expression was mirrored within placental tissue from women with preeclampsia. In parallel, IGF-1, a target gene of miR-206, was also found to be downregulated (0.41 ± 0.04) in placental tissue from women with preeclampsia. miR-206 expression was also detectable in myometrium tissue and trophoblast cell lines. Conclusion: Our pilot study has identified miRNA-206 as a novel factor upregulated in preeclampsia within the maternal circulation and in placental tissue.

Endothelial FOS expression and pre-eclampsia

Please cite this paper as: Mackenzie RM, Sandrim VC, Carty DM, McClure JD, Freeman DJ, Dominiczak AF, McBride MW, Delles C. Endothelial FOS expression and pre‐eclampsia. BJOG 2012;119:1564–1571.

Proteomics in hypertension

Proteomics, the study of the proteins making up the proteome, has emerged in recent years as an important tool in several different fields of medical research for early disease detection, for assessment of response to treatment and for unravelling underlying pathophysiological mechanisms. Although the majority of patients with hypertension are treated in a similar manner, the causes underlying the condition are diverse, and often poorly understood. Genetic studies have implicated several different candidate genes, but it may be that examination of the ‘downstream’ products of genes, the proteins, will help to improve understanding of the link between the environmental and genetic effects that contribute towards development of hypertension. Proteomic studies can be performed quickly and reliably on several different sample types including plasma and urine, requiring minimal pre-test preparation. In this review, we will compare the different analytical platforms and technical issues involved in proteomic analysis. We will discuss existing studies of proteomics in hypertension, as well as related conditions such as renal disease, pre-eclampsia and coronary artery disease. We will also explore potential future applications of proteomics-based research, which may ultimately lead to improved population screening, monitoring of therapy and early detection of target organ damage.