Flow Cytometric Detection of Activated Platelets in Pregnant Women Prior to the Development of Pre-Eclampsia

Suppression of circular RNA serum and glucocorticoid-induced kinase 1 elevates antioxidant molecules and angiogenesis in trophoblast cells to attenuate preeclampsia via microRNA-508-3p to target and restrain PUM homolog 1

AIM

Preeclampsia (PE) is a pregnancy-specific syndrome characterized by hypertension and proteinuria. Recently, multiple circular RNAs (circRNAs) were considered latent clinical diagnostic markers or therapeutic targets. This study was to explore the impact of circRNA serum and glucocorticoid-induced kinase 1 (SGK1) on PE via influencing the microRNA (miR)-508-3p/PUM homolog 1 (PUM1) axis.

METHODS

Placental tissues of 34 pregnant women with PE and 34 normal pregnant women were collected to measure circRNA SGK1 (circSGK1), miR-508-3p, and PUM1. Human placental trophoblasts HTR-8/SVneo were transfected with plasmids, thereafter to observe proliferation, migration, invasion, and apoptosis, analyze antioxidant molecules Troxerutin (TXN), Glutamate-cysteine ligase catalytic subunit (GCLC), NAD (P) H-quinone oxidoreductase 1 (NQO1), and determine angiogenesis. After the construction of the PE rat model, antioxidant molecules TXN, GCLC, and NQO1, vascular-associated factor vascular endothelial growth factor A (VEGF-A), and histopathological conditions were tested. Examination of the binding of circSGK1 and miR-508-3p with PUM1 was performed.

RESULTS

Our data showed that circSGK1 expression was elevated in the placenta of patients with PE. Silenced circSGK1 or elevated miR-508-3p promoted the growth and antioxidant molecules and angiogenesis in trophoblast cells; CircSGK1 combined with miR-508-3p, and miR-508-3p targeted PUM1.

CONCLUSIONS

In summary, suppression of circSGK1 augments antioxidant molecules and angiogenesis in trophoblast cells to attenuate PE via miR-508-3p to target PUM1.

Platelet count in preeclampsia: a systematic review and meta-analysis

OBJECTIVE

Many studies have reported the association between platelets and preeclampsia. However, sample sizes were small, and their findings were inconsistent. We conducted a systematic review and meta-analysis to evaluate the association in pooled samples and in detail.

DATA SOURCES

A systematic literature search was performed using Medline, Embase, ScienceDirect, Web of Science, Cochrane Library, NICHD-DASH, LILACS, and Scopus from inception to April 22, 2022.

STUDY ELIGIBILITY CRITERIA

Observational studies comparing platelet count between women with preeclampsia and normotensive pregnant women were included.

METHODS

The mean differences with 95% confidence interval in platelet count were calculated. Heterogeneity was assessed using I2 statistics. Sensitivity and subgroup analyses were conducted. Statistical analysis was performed using RevMan 5.3 and ProMeta 3 software.

RESULTS

A total of 56 studies comprising 4892 preeclamptic and 9947 normotensive pregnant women were included. Meta-analysis showed that platelet count was significantly lower in women with preeclampsia than in normotensive controls (overall: mean difference, -32.83; 95% confidence interval, -40.13 to -25.52; P<.00001; I2=92%; mild preeclampsia: mean difference, -18.65; 95% confidence interval, -27.17 to -10.14; P<.00001; I2=84%; severe preeclampsia: mean difference, -42.61; 95% confidence interval, -57.53 to -27.68; P<.00001; I2=94%). Significantly lower platelet count was also observed in the second trimester (mean difference, -28.84; 95% confidence interval, -44.59 to -13.08; P=.0003; I2=93%), third trimester (mean difference, -40.67; 95% confidence interval, -52.14 to -29.20; P<.00001; I2=92%), and before the diagnosis of preeclampsia (mean difference, -18.81; 95% confidence interval, -29.98 to -7.64; P=.009; I2=87%), but not in the first trimester (mean difference, -15.14; 95% confidence interval, -37.71 to 7.43; P=.19; I2=71%). Overall, the pooled sensitivity and specificity of platelet count were 0.71 and 0.77, respectively. The area under the curve was 0.80.

CONCLUSION

This meta-analysis confirmed that platelet count was significantly lower in preeclamptic women, irrespective of severity and presence or absence of associated complications, even before the onset of preeclampsia and in the second trimester of pregnancy. Our findings suggest that platelet count may be a potential marker to identify and predict preeclampsia.

Preeclampsia: Platelet procoagulant membrane dynamics and critical biomarkers

A state-of-the-art lecture titled "Preeclampsia and Platelet Procoagulant Membrane Dynamics" was presented at the International Society on Thrombosis and Haemostasis (ISTH) Congress in 2022. Platelet activation is involved in the pathophysiology of preeclampsia and contributes to the prothrombotic state of the disorder. Still, it remains unclear what mechanisms initiate and sustain platelet activation in preeclampsia and how platelets drive the thrombo-hemorrhagic abnormalities in preeclampsia. Here, we highlight our findings that platelets in preeclampsia are preactivated possibly by plasma procoagulant agonist(s) and overexpress facilitative glucose transporter-3 (GLUT3) in addition to GLUT1. Preeclampsia platelets are also partially degranulated, procoagulant, and proaggregatory and can circulate as microaggregates/microthrombi. However, in response to exposed subendothelial collagen, such as in injured vessels during cesarean sections, preeclampsia platelets are unable to mount a full procoagulant response, contributing to blood loss perioperatively. The overexpression of GLUT3 or GLUT1 may be monitored alone or in combination (GLUT1/GLUT3 ratio) as a biomarker for preeclampsia onset, phenotype, and progression. Studies to further understand the mediators of the platelet activation and procoagulant membrane dynamics in preeclampsia can reveal novel drug targets and suitable alternatives to aspirin for the management of prothrombotic tendencies in preeclampsia. Finally, we summarize relevant new data on this topic presented during the 2022 ISTH Congress.

Proteomics and Metabolomics Profiling of Platelets and Plasma Mediators of Thrombo-Inflammation in Gestational Hypertension and Preeclampsia

Platelets may be pivotal mediators of the thrombotic and coagulopathic complications of preeclampsia (PE), linking inflammation and thrombosis with endothelial and vascular dysfunction. Both PE and gestational hypertension (GH) fall within the spectrum of hypertensive complications of pregnancy, with GH being a risk factor for preeclampsia. However, it is unclear what biomarkers distinguish PE from GH. Using a discovery size cohort, we aimed to characterize specific plasma and platelet thrombo-inflammatory drivers indicative of PE and differentiate PE from GH. We performed multiplex immunoassays, platelet and plasma quantitative proteomics and metabolomics of PE patients, comparing with non-pregnant (NP), healthy pregnant controls (PC) and GH participants. The expression pattern of plasma proteins and metabolites in PE/GH platelets was distinct from that of NP and PC. Whilst procoagulation in PC may be fibrinogen driven, inter-alpha-trypsin inhibitors ITIH2 and ITIH3 are likely mediators of thrombo-inflammation in GH and PE, and fibronectin and S100A8/9 may be major procoagulant agonists in PE only. Also enriched in PE were CCL1 and CCL27 plasma cytokines, and the platelet leucine-rich repeat-containing protein 27 and 42 (LRRC27/42), whose effects on platelets were explored using STRING analysis. Through protein-protein interactions analysis, we generated a new hypothesis for platelets’ contribution to the thrombo-inflammatory states of preeclampsia.

Aspirin for the prevention of pre-eclampsia in women with pre-existing diabetes: Systematic review

BACKGROUND

There is a lack of evidence for pre-eclampsia prophylaxis with aspirin in women with pre-existing diabetes mellitus (DM).

AIMS

To examine the evidence for aspirin in pre-eclampsia prophylaxis in women with pre-existing DM.

MATERIAL AND METHODS

An electronic search using Ovid MEDLINE, Embase, CinicalTrials.gov and the Cochrane CENTRAL register of controlled trials through to February 2021 was performed. Reference lists of identified studies, previous review articles, clinical practice guidelines and government reports were manually searched. Randomised controlled trials (RCTs) of aspirin vs placebo for pre-eclampsia prophylaxis were included. Articles were manually reviewed to determine if cohorts included women with DM. The systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Data from included trials were extracted independently by two authors who also independently assessed risk of bias as per the Cochrane Handbook criteria version 5.1.0. Data were analysed using Rev-Man 5.4.

RESULTS

Forty RCTs were identified, of which 11 included a confirmed subset of women with DM; however, data were insufficient for meta-analysis. Meta-analysis of 930 women with DM, from individual patient data included in a systematic review and unpublished data from one of the 11 RCTs, showed a non-significant difference in the outcome of pre-eclampsia in participants treated with aspirin compared to placebo (odds ratio 0.58; 95% CI 0.20-1.71; P = 0.33).

CONCLUSIONS

Pre-eclampsia risk reduction with aspirin prophylaxis in women with pre-existing DM may be similar to women without pre-existing DM. However, randomised data within this meta-analysis were insufficient, warranting the need for further studies within this high-risk group of women.

Prothrombotic state associated with preeclampsia

PURPOSE OF REVIEW

Preeclampsia is a common complication of pregnancy and contributes significantly to maternal and fetal morbidity and mortality. A protective hypercoagulable state is often developed during late pregnancy and can evolve into a prothrombotic state in patients with preeclampsia. The underlying mechanism of this prothrombotic transition remains poorly understood. We discuss recent progress in understanding the pathophysiology of preeclampsia and associated prothrombotic state.

RECENT FINDINGS

The hypercoagulable state developed during pregnancy is initiated by placental factors and progresses into the prothrombotic state in preeclampsia when the placenta is subjected ischemic and oxidative injuries. The cause of the preeclampsia-induced prothrombotic state is multifactorial, involving not only placental factors but also maternal conditions, which include genetic predisposition, preexisting medical conditions, and conditions acquired during pregnancy. Endotheliopathy is the primary pathology of preeclampsia and contributes to the prothrombotic state by inducing the dysregulation of coagulation, platelets, and adhesive ligands.

SUMMARY

Patients with preeclampsia often develop a severe prothrombotic state that predisposes them to life-threatening thrombosis and thromboembolism during and after pregnancy. Early recognition and treatment of this prothrombotic state can improve maternal and infant outcomes of preeclampsia patients.

Oxidative Stress and Preeclampsia-Associated Prothrombotic State

Preeclampsia (PE) is a common obstetric disease characterized by hypertension, proteinuria, and multi-system dysfunction. It endangers both maternal and fetal health. Although hemostasis is critical for preventing bleeding complications during pregnancy, delivery, and post-partum, PE patients often develop a severe prothrombotic state, potentially resulting in life-threatening thrombosis and thromboembolism. The cause of this thrombotic complication is multi-factorial, involving endothelial cells, platelets, adhesive ligands, coagulation, and fibrinolysis. Increasing evidence has shown that hemostatic cells and factors undergo oxidative modifications during the systemic inflammation found in PE patients. However, it is largely unknown how these oxidative modifications of hemostasis contribute to development of the PE-associated prothrombotic state. This knowledge gap has significantly hindered the development of predictive markers, preventive measures, and therapeutic agents to protect women during pregnancy. Here we summarize reports in the literature regarding the effects of oxidative stress and antioxidants on systemic hemostasis, with emphasis on the condition of PE.

Current update of first trimester preeclampsia screening in Asia

In consideration of high prevalence of preeclampsia, enormous studies attempted to look for strategies in early gestation. Hence, a powerful screening should be built up in first trimester. Then, Aspirin could be administrated for proper prevention. The objective of this article is reviewing the screening for preeclampsia in first trimester recently. To identify the high-risk group precisely, an effective model should be recommended to Asian population. Articles related to first trimester screening of PE in Asia from databases of PubMed, ScienceDirect and Scopus were searched for this narrative review. The criteria included randomized clinical trials, observational prospective and retrospective cohort studies, case-control studies, systematic review and meta-analysis and professional review articles. Screening models combining maternal factors, biophysical factors, ultrasound studies and biochemical factors achieved high predictive performance of preeclampsia. In Asia, the detection rate of the Fetal Medicine Foundation is superior to those of the American College of Obstetricians and Gynecologists and the National Institute for Health and Care Excellence. Consequently, this effective model from the Fetal Medicine Foundation should be continuously used for screening in first trimester for the Asian.

The role of haemostasis in placenta-mediated complications

Normal pregnancy is associated with an increasing state of activation of the haemostatic system. This activation state is excessive in women with placenta-mediated pregnancy complications (PMPCs), including preeclampsia (PE). Platelet activation plays a crucial pathophysiological role in PE. The very early activation of coagulation in the intervillous space is mandatory for placental growth and morphogenesis but its excesses and/or inadequate control may participate to the emergence of the trophoblastic phenotype of PE. Extracellular vesicles, of endothelial but also of trophoblastic origin, can favour key cellular reactions of preeclampsia, acting as proactive cofactors. The understanding of this intricate relationship between haemostasis activation and PMPCs may provide interesting keys for new pathophysiological therapeutic developments.

Maternal Platelets—Friend or Foe of the Human Placenta?

Human pregnancy relies on hemochorial placentation, including implantation of the blastocyst and deep invasion of fetal trophoblast cells into maternal uterine blood vessels, enabling direct contact of maternal blood with placental villi. Hemochorial placentation requires fast and reliable hemostasis to guarantee survival of the mother, but also for the neonates. During human pregnancy, maternal platelet count decreases gradually from first, to second, and third trimester. In addition to hemodilution, accelerated platelet sequestration and consumption in the placental circulation may contribute to a decline of platelet count throughout gestation. Local stasis, turbulences, or damage of the syncytiotrophoblast layer can activate maternal platelets within the placental intervillous space and result in formation of fibrin-type fibrinoid. Perivillous fibrinoid is a regular constituent of the normal placenta which is considered to be an important regulator of intervillous hemodynamics, as well as having a role in shaping the developing villous trees. However, exaggerated activation of platelets at the maternal-fetal interface can provoke inflammasome activation in the placental trophoblast, and enhance formation of circulating platelet-monocyte aggregates, resulting in sterile inflammation of the placenta and a systemic inflammatory response in the mother. Hence, the degree of activation determines whether maternal platelets are a friend or foe of the human placenta. Exaggerated activation of maternal platelets can either directly cause or propagate the disease process in placenta-associated pregnancy pathologies, such as preeclampsia.

Antiplatelet agents for preventing pre-eclampsia and its complications

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, low-dose aspirin in particular, might prevent or delay development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents, such as aspirin and dipyridamole, when given to women at risk of developing pre-eclampsia.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (30 March 2018), and reference lists of retrieved studies. We updated the search in September 2019 and added the results to the awaiting classification section of the review.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent were included. Studies only published in abstract format were eligible for inclusion if sufficient information was available. We would have included cluster-randomised trials in the analyses along with individually-randomised trials, if any had been identified in our search strategy. Quasi-random studies were excluded. Participants were pregnant women at risk of developing pre-eclampsia. Interventions were administration of an antiplatelet agent (such as low-dose aspirin or dipyridamole), comparisons were either placebo or no antiplatelet.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trials for inclusion and extracted data independently. For binary outcomes, we calculated risk ratio (RR) and its 95% confidence interval (CI), on an intention-to-treat basis. For this update we incorporated individual participant data (IPD) from trials with this available, alongside aggregate data (AD) from trials where it was not, in order to enable reliable subgroup analyses and inclusion of two key new outcomes. We assessed risk of bias for included studies and created a 'Summary of findings' table using GRADE.

MAIN RESULTS

Seventy-seven trials (40,249 women, and their babies) were included, although three trials (relating to 233 women) did not contribute data to the meta-analysis. Nine of the trials contributing data were large (> 1000 women recruited), accounting for 80% of women recruited. Although the trials took place in a wide range of countries, all of the nine large trials involved only women in high-income and/or upper middle-income countries. IPD were available for 36 trials (34,514 women), including all but one of the large trials. Low-dose aspirin alone was the intervention in all the large trials, and most trials overall. Dose in the large trials was 50 mg (1 trial, 1106 women), 60 mg (5 trials, 22,322 women), 75mg (1 trial, 3697 women) 100 mg (1 trial, 3294 women) and 150 mg (1 trial, 1776 women). Most studies were either low risk of bias or unclear risk of bias; and the large trials were all low risk of bas. Antiplatelet agents versus placebo/no treatment The use of antiplatelet agents reduced the risk of proteinuric pre-eclampsia by 18% (36,716 women, 60 trials, RR 0.82, 95% CI 0.77 to 0.88; high-quality evidence), number needed to treat for one women to benefit (NNTB) 61 (95% CI 45 to 92). There was a small (9%) reduction in the RR for preterm birth <37 weeks (35,212 women, 47 trials; RR 0.91, 95% CI 0.87 to 0.95, high-quality evidence), NNTB 61 (95% CI 42 to 114), and a 14% reduction infetal deaths, neonatal deaths or death before hospital discharge (35,391 babies, 52 trials; RR 0.85, 95% CI 0.76 to 0.95; high-quality evidence), NNTB 197 (95% CI 115 to 681). Antiplatelet agents slightly reduced the risk of small-for-gestational age babies (35,761 babies, 50 trials; RR 0.84, 95% CI 0.76 to 0.92; high-quality evidence), NNTB 146 (95% CI 90 to 386), and pregnancies with serious adverse outcome (a composite outcome including maternal death, baby death, pre-eclampsia, small-for-gestational age, and preterm birth) (RR 0.90, 95% CI 0.85 to 0.96; 17,382 women; 13 trials, high-quality evidence), NNTB 54 (95% CI 34 to 132). Antiplatelet agents probably slightly increase postpartum haemorrhage > 500 mL (23,769 women, 19 trials; RR 1.06, 95% CI 1.00 to 1.12; moderate-quality evidence due to clinical heterogeneity), and they probably marginally increase the risk of placental abruption, although for this outcome the evidence was downgraded due to a wide confidence interval including the possibility of no effect (30,775 women; 29 trials; RR 1.21, 95% CI 0.95 to 1.54; moderate-quality evidence). Data from two large trials which assessed children at aged 18 months (including results from over 5000 children), did not identify clear differences in development between the two groups.

AUTHORS' CONCLUSIONS

Administering low-dose aspirin to pregnant women led to small-to-moderate benefits, including reductions in pre-eclampsia (16 fewer per 1000 women treated), preterm birth (16 fewer per 1000 treated), the baby being born small-for-gestational age (seven fewer per 1000 treated) and fetal or neonatal death (five fewer per 1000 treated). Overall, administering antiplatelet agents to 1000 women led to 20 fewer pregnancies with serious adverse outcomes. The quality of evidence for all these outcomes was high. Aspirin probably slightly increased the risk of postpartum haemorrhage of more than 500 mL, however, the quality of evidence for this outcome was downgraded to moderate, due to concerns of clinical heterogeneity in measurements of blood loss. Antiplatelet agents probably marginally increase placental abruption, but the quality of the evidence was downgraded to moderate due to low event numbers and thus wide 95% CI. Overall, antiplatelet agents improved outcomes, and at these doses appear to be safe. Identifying women who are most likely to respond to low-dose aspirin would improve targeting of treatment. As almost all the women in this review were recruited to the trials after 12 weeks' gestation, it is unclear whether starting treatment before 12 weeks' would have additional benefits without any increase in adverse effects. While there was some indication that higher doses of aspirin would be more effective, further studies would be warranted to examine this.

Platelet function in preeclampsia - a systematic review and meta-analysis

Preeclampsia is a serious pregnancy-related complication. Platelets are potentially important in the pathogenesis of preeclampsia, and platelet function analyses may prove as sensitive preeclampsia biomarkers. This study aimed to systematically review and summarise the literature on platelet function markers in preeclampsia. This systematic review was conducted according to PRISMA and registered in PROSPERO. Relevant studies were identified through PubMed and Embase on 15/08/17. As platelet function markers platelet activation, platelet aggregation and platelet adhesion markers were included. If possible, relevant data were extracted for each marker to perform a meta-analysis of the mean difference between women with and without preeclampsia. All 69 included articles underwent quality rating. Some platelet activation markers, especially p-selectin and mean platelet volume (MPV), were significantly increased comparing the two groups of women, while others were not. The meta-analysis demonstrated that, overall, women with preeclampsia had significantly higher MPV than in women without preeclampsia. No significant difference was found regarding platelet aggreg`ation comparing the two groups. Platelet adhesion was investigated in noneof the included studies. In conclusion, further studies are warranted to investigate platelet activation markers future role as predictive markers in preeclampsia. MPV is suggested as the most promising biomarker for evaluating platelet function in preeclampsia.

Melatonin enhances antioxidant molecules in the placenta, reduces secretion of soluble fms-like tyrosine kinase 1 (sFLT) from primary trophoblast but does not rescue endothelial dysfunction: An evaluation of its potential to treat preeclampsia

Preeclampsia is one of the most serious complications of pregnancy. Currently there are no medical treatments. Given placental oxidative stress may be an early trigger in the pathogenesis of preeclampsia, therapies that enhance antioxidant pathways have been proposed as treatments. Melatonin is a direct free-radical scavenger and indirect antioxidant. We performed in vitro assays to assess whether melatonin 1) enhances the antioxidant response element genes (heme-oxygenase 1, (HO-1), glutamate-cysteine ligase (GCLC), NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1), thioredoxin (TXN)) or 2) alters secretion of the anti-angiogenic factors soluble fms-like tyrosine kinase-1 (sFLT) or soluble endoglin (sENG) from human primary trophoblasts, placental explants and human umbilical vein endothelial cells (HUVECs) and 3) can rescue TNF-α induced endothelial dysfunction. In primary trophoblast melatonin treatment increased expression of the antioxidant enzyme TXN. Expression of TXN, GCLC and NQO1 was upregulated in placental tissue with melatonin treatment. HUVECs treated with melatonin showed an increase in both TXN and GCLC. Melatonin did not increase HO-1 expression in any of the tissues examined. Melatonin reduced sFLT secretion from primary trophoblasts, but had no effect on sFLT or sENG secretion from placental explants or HUVECs. Melatonin did not rescue TNF-α induced VCAM-1 and ET-1 expression in endothelial cells. Our findings suggest that melatonin induces antioxidant pathways in placenta and endothelial cells. Furthermore, it may have effects in reducing sFLT secretion from trophoblast, but does not reduce endothelial dysfunction. Given it is likely to be safe in pregnancy, it may have potential as a therapeutic agent to treat or prevent preeclampsia.

Impact of haemostatic mechanisms on pathophysiology of preeclampsia

Preeclampsia (PE) is disorder of new onset hypertension and proteinuria during the second half of pregnancy. There is increasing evidence to implicate placental over-expression of tissue factor and PAR-1 in the pathophysiology of PE. Excessive activation of platelets, neutrophils and the complement system may also contribute to the placental pathology and maternal endothelial responsible for the symptoms of PE. Increased knowledge in this field may identify new therapeutic strategies for the treatment of PE.

Increased Concentration of Soluble CD40 Ligand in Preeclampsia

Preeclampsia has been associated with increased platelet activation detected before disease onset. Platelets are involved in hemostasis and also directly initiate an inflammatory response of the vessel wall. Inappropriate activation of platelets may be involved in pathogenesis in preeclampsia by promoting coagulation and thrombosis, and also as a mediator of inflammation. Platelets may release inflammatory mediators such as soluble CD40 ligand. The plasma level of soluble CD40 ligand was investigated during preeclamptic (n =20) and normal pregnancies (n = 20) to emphasize inflammatory response in preeclampsia. The mean soluble CD40 ligand levels were 1.08 ± 0.43 ng/mL in patients with preeclampsia and 0.76 ± 0.24 ng/mL in healthy pregnant women, which was statistically significant ( P = .01). To clarify whether inflammation may cause inappropriate endothelial cell activation or inappropriate endothelial cell activation may start this inflammatory response, future studies are needed in a larger study population.

S-Nitrosoglutathione improves haemodynamics in early-onset pre-eclampsia

AIMS

To determine the effects of in vivo S-nitrosoglutathione (GSNO) infusion on cardiovascular function, platelet function, proteinuria and biomarker parameters in early-onset pre-eclampsia.

METHODS

We performed an open-label dose-ranging study of GSNO in early-onset pre-eclampsia. Six women underwent GSNO infusion whilst receiving standard therapy. The dose of GSNO was increased incrementally to 100 μg min(-1) whilst maintaining blood pressure of >140/80 mmHg. Aortic augmentation index, aortic pulse wave velocity, blood pressure and maternal-fetal Doppler parameters were measured at each dose. Platelet P-selectin, protein-to-creatinine ratio and soluble anti-angiogenic factors were measured pre- and postinfusion.

RESULTS

Augmentation index fell at 30 μg min(-1) S-nitrosoglutathione (-6%, 95% confidence interval 0.6 to 13%), a dose that did not affect blood pressure. Platelet P-selectin expression was reduced [mean (interquartile range), 6.3 (4.9-7.6) vs. 4.1 (3.1-5.7)% positive, P = 0.03]. Soluble endoglin levels showed borderline reduction (P = 0.06). There was a borderline significant change in pre-to-postinfusion protein-to-creatinine ratio [mean (interquartile range), 0.37 (0.09-0.82) vs. 0.23 (0.07-0.49) g mmol(-1) , P = 0.06]. Maternal uterine and fetal Doppler pulsatility indices were unchanged.

CONCLUSIONS

In early-onset pre-eclampsia, GSNO reduces augmentation index, a biomarker of small vessel tone and pulse wave reflection, prior to affecting blood pressure. Proteinuria and platelet activation are improved at doses that affect blood pressure minimally. These effects of GSNO may be of therapeutic potential in pre-eclampsia, a condition for which no specific treatment exists. Clinical studies of GSNO in early-onset pre-eclampsia will determine whether these findings translate to improvement in maternal and/or fetal outcome.

The expression and concentration of CD40 ligand in normal pregnancy, preeclampsia, and hemolytic anemia, elevated liver enzymes and low platelet count (HELLP) syndrome

Preeclampsia has been associated with increased platelet activation detected before disease onset. Inappropriate activation of platelets may be involved in pathogenesis in preeclampsia by promoting coagulation and thrombosis and also as a mediator of inflammation. The exaggerated platelet activation and inflammation leading to endothelial damage in preeclampsia can be explained by the CD40-CD40 ligand (CD40L) system. Expression of CD40L on platelets was determined by whole-blood flow cytometry, and serum levels of soluble CD40L (sCD40L) were measured by enzyme-linked immunosorbent assay in 11 women with mild preeclampsia, 11 women with severe preeclampsia, and six women with hemolytic anemia, elevated liver enzymes and low platelet count (HELLP) syndrome compared with 13 normotensive pregnant women as a control group. The platelet surface expression of CD40L was significantly higher in women with mild and severe preeclampsia and HELLP compared with normal pregnancy group (P = 0.001; P ≤ 0.001; P = 0.003, respectively), with no significant difference being found between women with mild preeclampsia compared with HELLP and severe preeclampsia compared with HELLP (P = 0.2; P = 0.8, respectively). The serum concentration of sCD40L was significantly higher in women with mild and severe preeclampsia and HELLP compared with the normal pregnancy group (P = 0.001; P ≤ 0.001; P = 0.022, respectively), with no significant difference being found between women with mild compared with severe preeclampsia or HELLP and severe preeclampsia compared with HELLP (P = 0.7; P = 0.6; P = 0.6, respectively). In conclusion, the higher expression and concentration of CD40L in women with preeclampsia and HELLP syndrome compared with normal pregnant women may indicate an exaggerated activation of platelets and endothelial cells in the disorder.

Preeclampsia: multiple approaches for a multifactorial disease

Preeclampsia is a pregnancy-specific disorder characterized by hypertension and excess protein excretion in the urine. It is an important cause of maternal and fetal morbidity and mortality worldwide. The disease is almost exclusive to humans and delivery of the pregnancy continues to be the only effective treatment. The disorder is probably multifactorial, although most cases of preeclampsia are characterized by abnormal maternal uterine vascular remodeling by fetally derived placental trophoblast cells. Numerous in vitro and animal models have been used to study aspects of preeclampsia, the most common being models of placental oxygen dysregulation, abnormal trophoblast invasion, inappropriate maternal vascular damage and anomalous maternal-fetal immune interactions. Investigations into the pathophysiology and treatment of preeclampsia continue to move the field forward, albeit at a frustratingly slow pace. There remains a pressing need for novel approaches, new disease models and innovative investigators to effectively tackle this complex and devastating disorder.

The possible options for the prevention of preeclampsia

This review summarizes the possible options for the prevention of preeclampsia based on important factors of patomechanism. The effects of antioxidants have been described in numerous clinical researches based on the oxidative hypothesis. Another important factor is the change of nitric oxide activity. Nitric oxide donors are able to compensate the symptoms of preeclampsia. The inverse relationship between the calcium intake and gestational hypertension has been known for a long time. The calcium supplementation seems to be a good opportunity to prevent preeclampsia. With low molecular weight heparins we can intervene in the patomechanisms of preeclampsia by antithrombocyte effects, vasoactive properties and impact on throphoblast cell morphology and differentiation. Thrombocyte aggregation inhibitors were examined in number of studies because they reduced thromboxane mediated vasoconstriction and inhibited placental thrombosis. Several studies verify whether prophylaxis with low molecular weight heparins and low dose aspirin could improve pregnancy outcome in preeclampsia. Orv. Hetil., 2012, 153, 144–151.

Physiologic and pathologic changes of platelets in pregnancy

Platelets are key players in haemostasis and thrombus formation. Defects affecting platelets during pregnancy can lead to heterogeneous complications, such as thrombosis, first trimester miscarriage and postpartum haemorrhage. The incidence of complications is increased in women who have heritable platelet function disorders. Modifications of platelet count or platelet functions during normal pregnancy and preeclampsia will be summarized and the management of pregnant women with heritable platelet function disorders will be discussed.

Evidence of maternal platelet activation, excessive thrombin generation, and high amniotic fluid tissue factor immunoreactivity and functional activity in patients with fetal death

OBJECTIVE

Fetal death can lead to disseminated intravascular coagulation or fetal death syndrome. However, currently it is not clear what are the changes in the coagulation system in patients with a fetal death without the fetal death syndrome. This study was undertaken to determine: (1) whether fetal death in the absence of fetal death syndrome is associated with changes in hemostatic markers in maternal plasma and amniotic fluid; and (2) whether maternal hypertension or placental abruption are associated with further changes in the hemostatic profile of these patients.

METHODS

A cross-sectional study included the following: (1) determination of changes in markers of coagulation and platelet activation in patients with a normal pregnancy (n = 71) and patients with fetal demise (FD) without disseminated intravascular coagulation (n = 65); (2) determination of the amniotic fluid (AF)-tissue factor concentration and activity, as well as the concentrations of thrombin-antithrombin III (TAT) complexes in patients with a normal pregnancy (n = 25) and those with a FD (n = 36) who underwent amniocentesis. Plasma and AF concentrations of TAT complexes and TF (an index of thrombin generation), as well as maternal plasma concentrations of sCD40L (a marker of platelet activation), tissue factor pathway inhibitor (TFPI) and prothrombin fragments (PF) 1 + 2 (also an indicator of in vivo thrombin generation) were measured by ELISA. TF and TFPI activity were measured using chromogenic assays.

RESULTS

(1) patients with FD without hypertension had a higher median maternal plasma sCD40L concentration than normal pregnant women (P < 0.001); (2) patients with FD had a higher median maternal plasma TAT III complexes than women with a normal pregnancy (P < 0.001); (3) the median AF-TF concentration and activity were higher in the FD group than in the normal pregnancy group (P < 0.001 for both); (4) patients with preeclampsia and FD had a higher median maternal plasma immunoreactive TF concentration than both normotensive patients with FD and women with normal pregnancies (P < 0.001 and P = 0.001, respectively); (5) the median plasma TF activity was higher in patients with preeclampsia and FD than that of women with normal pregnancies (P = 0.003); (6) among patients with a FD, those with placental abruption had a higher median AF-TAT complexes concentration than those without abruption (P = 0.0004).

CONCLUSIONS

Our findings indicate that: (1) mothers with a FD have evidence of increased in vivo thrombin generation and platelet activation than women with normal pregnancies; (2) patients with a FD and hypertension had a higher degree of TF activation than those with fetal death but without hypertension; (3) the AF of women with a FD had a higher median TF concentration and activity than that of normal pregnant women. AF can be a potential source for tissue factor and it participates in the development of fetal death syndrome in patients with a retained dead fetus.

Flow Cytometric Investigation of CD40-CD40 Ligand System in Preeclampsia and Normal Pregnancy

Our aim was to investigate the CD40-CD40 ligand system in preeclamptic women. We also studied CD62P and platelet—monocyte aggregates, which have been closely linked to the CD40—CD40L system. Platelet expression of CD40L and CD62P and expression of CD40 on monocytes and platelet—monocyte aggregates were determined by flow cytometry in whole blood from 23 preeclamptic women, 23 normotensive pregnant women, and 23 nonpregnant women. The preeclamptic women showed a significant increase in CD40L and CD62P on platelets and in CD40 on monocytes when compared with normotensive pregnant women and nonpregnant women (all P < .001). There was a significant increase in platelet—monocyte aggregates in preeclamptic women (P < .001) and normotensive pregnant women (P = .003) compared with nonpregnant women. Preeclampsia is associated with activation of the CD40—CD40L system. The activation of this system may contribute to the development or maintenance of the proinflammatory and prothrombotic milieu found in preeclampsia.

Risk factor correlates of platelet and leukocyte markers assessed by flow cytometry in a population-based sample

BACKGROUND

Platelet and leukocyte products are involved in atherothrombosis. However, the determinants of platelet and leukocyte markers assessed by flow cytometry have not been documented in a population-based sample.

METHODS AND RESULTS

We performed flow cytometry on blood from participants (n=1894) in the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study. Cellular aggregates and multiple platelet and leukocyte markers, such as myeloperoxidase in granulocytes and toll-like receptor-4, CD14, and CD45 in monocytes, were quantified. Their cross-sectional associations with demographic and risk factors were assessed using multiple linear regression. Mean values of most cellular markers and aggregates were considerably higher in blacks than whites (p<0.01). There were some differences in cellular markers between men and women, but little association with age. LDL-cholesterol was associated positively with several markers (toll-like receptor-4 and myeloperoxidase in granulocytes and CD162 in lymphocytes). Cholesterol-lowering therapy tended to show opposite associations. Smokers had much higher granulocyte myeloperoxidase than nonsmokers. However, most other correlations between risk factors and cellular markers were nonsignificant.

CONCLUSIONS

Race/ethnicity, sex, and to a lesser degree LDL-cholesterol and cholesterol-lowering therapy, but few other risk factors, were correlated with markers of cellular activation in this population-based study.

HAEMODYNAMIC CONTRIBUTIONS TO THE PATHOGENESIS OF PREECLAMPSIA AND ECLAMPSIA

Current hypotheses regarding the origins of preeclampsia have focused on the “Two stage model”. This model suggests that the primary steps in the pathophysiologic sequence of preeclampsia are initiated by abnormal placentation including the classic finding of abnormal trophoblast invasion of maternal decidual spiral arteries. The second stage of the sequence includes the elaboration of a single or multiple substances from these disordered placentas which contribute to the generalized maternal systemic illness, eventually manifesting as endothelial injury, hypertension and proteinuria. Recent studies have focused on the role of pro and anti-angiogenic peptides as potential placentally derived aetiologic agents in this pathophysiologic sequence, although other placental products have been highlighted in recent research. Despite the fact that this modeling of preeclampsia has widespread support significant limitations to this hypothesis can be identified.

Anticoagulant therapy and pregnancy

Low dose aspirin therapy is one of the anticoagulant treatments used during pregnancy. Anticoagulant agents may be useful for several disorders, such as recurrent miscarriage, pre-eclampsia, fetal growth restriction and infertility. However, it is unclear whether anticoagulant therapy can increase the live birth rate in all of these cases. Recent data suggest that a low-dose aspirin and heparin combination therapy is effective in the prevention of recurrent pregnancy loss in women with antiphospholipid syndrome. Thrombogenic diseases, for example, protein C deficiency, protein S deficiency, factor XII deficiency and hyperhomocysteinemia, may cause pregnancy loss. The etiology of recurrent miscarriage is often unclear and may be multifactorial, with much controversy regarding diagnosis and treatment. Although 70% of recurrent pregnancy losses are unexplained, anticoagulant therapy is effective in maintaining pregnancy without antiphospholipid antibody syndrome. We conclude that a low-dose aspirin and heparin combination therapy can be useful for unexplained cases of recurrent pregnancy loss without antiphospholipid antibody syndrome. (Reprod Med Biol 2008; 7: 1-10).

Premature labor: a state of platelet activation?

OBJECTIVE

This study was undertaken to determine whether premature labor is associated with changes in the maternal plasma concentration of soluble CD40 ligand (sCD40L), a marker of platelet activation.

METHODS

A cross-sectional study included patients in the following groups: 1) non-pregnant (n=21); 2) normal pregnancy (n=71); 3) normal pregnancy at term with (n=67) and without labor (n=88); 4) preterm labor (PTL) with intact membranes (n=136) that was divided into the following sub-groups: 4a) PTL who delivered at term (n=49); 4b) PTL without intra-amniotic infection and/or inflammation (IAI) who delivered preterm (n=54); and 4c) PTL with IAI who delivered preterm (n=33). sCD40L concentrations were measured by ELISA.

RESULTS

The median maternal plasma sCD40L concentration was higher in pregnant than non-pregnant women (P=0.017). Patients with PTL had a higher median maternal plasma sCD40L concentration than women with normal pregnancies, regardless of the presence or absence of IAI and gestational age at delivery (P<0.001 for all comparisons). IAI was not associated with a higher median maternal plasma concentration of sCD40L.

CONCLUSIONS

Normal pregnancy is a state in which there is a physiologic increase of sCD40L. PTL was associated with an increased median maternal plasma sCD40L concentration that could not be accounted for by IAI. Thus, our findings suggest that platelet activation occurs during an episode of preterm labor.

WITHDRAWN: Antiplatelet agents for preventing and treating pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, and low dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia, and to those with established pre-eclampsia.

SEARCH STRATEGY

This review drew on the search strategy developed for the Pregnancy and Childbirth Group as a whole. The Cochrane Controlled Trials Register was also searched, The Cochrane Library 1999 Issue 1, Embase was searched from 1994-1999 and hand searches were performed of the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia, and those with pre-eclampsia before delivery. Women treated postpartum were excluded. Interventions were any comparisons of an antiplatelet agent (such as low dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Assessment of trials for inclusion in the review and extraction of data was performed independently and unblinded by two reviewers. Data were entered into the Review Manager software and double checked.

MAIN RESULTS

Forty two trials involving over 32,000 women were included in this review, with 30,563 women in the prevention trials. There is a 15% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents [32 trials with 29,331 women; relative risk (RR) 0.85, 95% confidence interval (0.78, 0.92); Number needed to treat (NNT) 89, (59, 167)]. This reduction is regardless of risk status at trial entry or whether a placebo was used, and irrespective of the dose of aspirin or gestation at randomisation.Twenty three trials (28,268 women) reported preterm delivery. There is a small (8%) reduction in the risk of delivery before 37 completed weeks [RR 0.92, (0.88, 0.97); NNT 72 (44, 200)]. Baby deaths were reported in 30 trials (30,093 women). Overall there is a 14% reduction in baby deaths in the antiplatelet group [RR 0.86, (0.75, 0.98); NNT 250 (125, >10000)]. Small for gestational age babies were reported in 25 trials (20,349 women), with no overall difference between the groups, RR 0.92, (0.84, 1.01). There were no significant differences between treatment and control groups in any other measures of outcome. Five trials compared antiplatelet agents with placebo or no antiplatelet agent for the treatment of pre-eclampsia. There are insufficient data for any firm conclusions about the possible effects of these agents when used for treatment of pre-eclampsia.

AUTHORS' CONCLUSIONS

Antiplatelet agents, in this review largely low dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment should be started, and at what dose.

Antiplatelet agents for prevention of pre-eclampsia: a meta-analysis of individual patient data

BACKGROUND

Pre-eclampsia is a major cause of mortality and morbidity during pregnancy and childbirth. Antiplatelet agents, especially low-dose aspirin, might prevent or delay pre-eclampsia, and thereby improve outcome. Our aim was to assess the use of antiplatelet agents for the primary prevention of pre-eclampsia, and to explore which women are likely to benefit most.

METHODS

We did a meta-analysis of individual patient data from 32,217 women, and their 32,819 babies, recruited to 31 randomised trials of pre-eclampsia primary prevention.

FINDINGS

For women assigned to receive antiplatelet agents rather than control, the relative risk of developing pre-eclampsia was 0.90 (95% CI 0.84-0.97), of delivering before 34 weeks was 0.90 (0.83-0.98), and of having a pregnancy with a serious adverse outcome was 0.90 (0.85-0.96). Antiplatelet agents had no significant effect on the risk of death of the fetus or baby, having a small for gestational age infant, or bleeding events for either the women or their babies. No particular subgroup of women was substantially more or less likely to benefit from antiplatelet agents than any other.

INTERPRETATION

Antiplatelet agents during pregnancy are associated with moderate but consistent reductions in the relative risk of pre-eclampsia, of birth before 34 weeks' gestation, and of having a pregnancy with a serious adverse outcome.

Antiplatelet agents for preventing pre-eclampsia and its complications

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, low-dose aspirin in particular, might prevent or delay development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents for women at risk of developing pre-eclampsia.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (July 2006), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2005, Issue 1), EMBASE (1994 to November 2005) and handsearched congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent were included. Quasi-random studies were excluded. Participants were pregnant women at risk of developing pre-eclampsia. Interventions were any comparisons of an antiplatelet agent (such as low-dose aspirin or dipyridamole) with either placebo or no antiplatelet.

DATA COLLECTION AND ANALYSIS

Two authors assessed trials for inclusion and extracted data independently.

MAIN RESULTS

Fifty-nine trials (37,560 women) are included. There is a 17% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents ((46 trials, 32,891 women, relative risk (RR) 0.83, 95% confidence interval (CI) 0.77 to 0.89), number needed to treat (NNT) 72 (52, 119)). Although there is no statistical difference in RR based on maternal risk, there is a significant increase in the absolute risk reduction of pre-eclampsia for high risk (risk difference (RD) -5.2% (-7.5, -2.9), NNT 19 (13, 34)) compared with moderate risk women (RD -0.84 (-1.37, -0.3), NNT 119 (73, 333)). Antiplatelets were associated with an 8% reduction in the relative risk of preterm birth (29 trials, 31,151 women, RR 0.92, 95% CI 0.88 to 0.97); NNT 72 (52, 119)), a 14% reduction in fetal or neonatal deaths (40 trials, 33,098 women, RR 0.86, 95% CI 0.76 to 0.98); NNT 243 (131, 1,666) and a 10% reduction in small-for-gestational age babies (36 trials, 23,638 women, RR 0.90, 95% CI0.83 to 0.98). There were no statistically significant differences between treatment and control groups for any other outcomes.

AUTHORS' CONCLUSIONS

Antiplatelet agents, largely low-dose aspirin, have moderate benefits when used for prevention of pre-eclampsia and its consequences. Further information is required to assess which women are most likely to benefit, when treatment is best started, and at what dose.

Serum-Soluble CD40 Ligand in Normal Pregnancy and in Preeclampsia

OBJECTIVE

Soluble CD40 ligand is a transmembrane protein shed from activated platelets that is involved in the activation of endothelial cells. Findings that estradiol (E2) has an inhibitory effect on inflammation and platelet function and that serum E2 levels are low in women with preeclampsia prompted us to investigate the association between soluble CD40 ligand and serum E2 levels in normal pregnancy and in preeclampsia.

METHODS

A case-control single-center design was used. The sample included 22 women with severe preeclampsia, 22 matched normotensive pregnant women, and 22 nonpregnant women. Enzyme immunoassay was used to measure soluble CD40 ligand.

RESULTS

Significantly higher levels of soluble CD40 ligand were detected in the nonpregnant women (23,767 +/- 15,637 pg/mL) and in the women with preeclampsia (21,025 +/- 45,386 pg/mL) than in the normotensive pregnant women (8,292 +/- 5,926 pg/mL) (P = .026). No significant correlation between soluble CD40 ligand levels and E2 levels was observed.

CONCLUSION

The higher levels of soluble CD40 ligand detected in women with preeclampsia may indicate an exaggerated activation of platelets and endothelial cells.

LEVEL OF EVIDENCE

II-2.

Subclinical signs of vascular damage relate to enhanced platelet responsiveness among nonpregnant formerly preeclamptic women

OBJECTIVE

In nonpregnant formerly preeclamptic women, the prevalence of occult cardiovascular abnormalities is increased. These high-risk women mildly benefit from low-dose aspirin in the prevention of recurrent disease. How this effect is mediated, either by affecting platelet or vascular function, is still unsettled. In this study, we tested the hypothesis that in these nonpregnant women, enhanced platelet responsiveness is common and related to microvascular damage.

STUDY DESIGN

At least 6 months' postpartum we evaluated in 66 formerly preeclamptic women platelet count, volume, and in vitro response to low-dose ADP (0.5 microg/mL). Peripheral levels of fibronectin (microg/mL), von Willebrand factor antigen (%), C-reactive protein (high-sensitive CRP, mg/L), urinary albumin, and protein (24-hour collection, g/mol creatinine) served as markers of vascular damage. Hemodynamic function was determined by plasma volume (iodine I 125 HSA indicator dilution method, mL/kg lean body mass), cardiac index (Doppler, mL/min/m2), blood pressure and heart rate (Dinamap [Critikon, Tampa, FL], mm Hg and beats/min, respectively). Thereafter, we subdivided these 66 women into 2 subgroups either with (n = 10, 15%) or without increased platelet responsiveness (n = 56, 85%). Both groups were compared nonparametrically.

RESULTS

Groups were comparable with respect to age, blood pressure, body mass index, parity, plasma volume, and cardiac index. Women with enhanced platelet responsiveness had higher levels of circulation fibronectin and CRP, and displayed more often albuminuria and proteinuria. In addition, even though platelet count was comparable between groups, the mean platelet volume was higher among women with enhanced platelet responsiveness.

CONCLUSION

Fifteen percent of formerly preeclamptic women had enhanced platelet responsiveness, which was associated with elevated levels of various markers for (micro) vascular damage. We speculate that in these women platelets are presensitized on a relatively dysfunctional endothelium. Although this association does not prove causality, these results may indicate a subgroup of women who benefit from low-dose aspirin in the prevention of recurrent disease in a next pregnancy.

Antiplatelet agents for prevention of pre-eclampsia and its consequences: a systematic review and individual patient data meta-analysis

BACKGROUND: There is now good evidence that antiplatelet agents (principally low dose aspirin) prevent pre-eclampsia, a leading cause of morbidity and mortality for pregnant women and their babies. A Cochrane Review identified moderate, but clinically important, reductions in the relative risks of pre-eclampsia (19%), preterm birth (7%) and perinatal mortality (16%) in women allocated antiplatelets, rather than placebo or no antiplatelet.Uncertainty remains, however, about whether some women (in terms of risk) benefit more than others, what dose of aspirin is best and when in pregnancy treatment should ideally start. Rather than undertake new trials, the best way to answer these questions is to utilise existing individual patient data from women enrolled in each trial. METHODS/DESIGN: Systematic review with meta-analysis based on individual patient data. This involves the central collection, validation and re-analysis of thoroughly checked data from individual women in all the available randomised trials.The objective is to confirm that antiplatelet agents, given during pregnancy, will reduce the incidence of pre-eclampsia. The review will then determine the size of this effect, and whether antiplatelets delay the onset of pre-eclampsia or its impact on important outcomes for women and their babies. It will also explore whether the effect of antiplatelets differs by womens' risk profile; when commenced during pregnancy; and/or by dose. DISCUSSION: The PARIS (Perinatal Antiplatelet Review of International Studies) Collaboration has been formed to undertake the review. This will be the first individual patient data review in the perinatal field. Final results should be available by 2006-7.

Platelet Activation, Sympathetic Tone, and Plasma Volume in Nulligravid Women of Reproductive Age

OBJECTIVE

Preeclampsia is associated with increased platelet activation, increased sympathetic activity, and decreased plasma volume. We sought to estimate the relationship of plasma volume, sympathetic activity, or both to platelet activation in nonpregnant nulligravid women.

METHODS

We studied 37 healthy nulligravid subjects during the follicular phase of the menstrual cycle. After intravenous access was obtained, subjects rested in the supine position for 15 minutes. Blood was drawn without venous constriction for measurement of plasma catecholamines (epinephrine and norepinephrine) and complete blood count. Antigenic markers of platelet activation, CD63 and CD61-CD14 (platelet-monocyte aggregates), were measured with flow cytometry. Plasma volume was estimated in the supine position by using Evans blue dye and is expressed in milliliters and corrected for body mass index (BMI). We compared data from the lowest plasma volume/BMI quartile with the 2 middle quartiles combined and with the upper quartile. Data are expressed as mean +/- standard deviation. P <.05 was considered significant.

RESULTS

Subjects were aged 26.5 +/- 5.0 years, BMI was 24.0 +/- 3.0 kg/m(2), and plasma volume was 2,685 +/- 429 mL. We identified no significant relationship of platelet concentration to plasma volume/BMI between quartile groups (P =.944). However, there was a significant difference between quartiles for %CD63 expression (P =.013) and for CD61/CD14 expression (P =.018), with the lowest quartile demonstrating elevated platelet activation.

CONCLUSIONS

We found evidence that enhanced platelet activation is associated with reduced plasma volume, but not with plasma catecholamine concentrations. There was no association of platelet concentration with reduced plasma volume. We speculate that elements of the clinical syndrome of preeclampsia coexist as a subclinical phenotype before pregnancy.

Antiplatelet agents for preventing pre-eclampsia and its complications

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, low-dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (September 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2003), EMBASE (1994 to 2003) and we handsearched the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi-random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia. Interventions were any comparisons of an antiplatelet agent (such as low-dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trials for inclusion in the review and extracted data. We entered data into the Review Manager software and double checked.

MAIN RESULTS

Fifty-one trials involving 36,500 women are included in this review. There is a 19% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents ((43 trials, 33,439 women; relative risk (RR) 0.81, 95% confidence interval (CI) 0.75 to 0.88); number needed to treat (NNT) 69 (51, 109)).Twenty-eight trials (31,845 women) reported preterm birth. There is a small (7%) reduction in the risk of delivery before 37 completed weeks ((RR 0.93, 95% CI 0.89 to 0.98); NNT 83 (50, 238)). Fetal or neonatal deaths were reported in 38 trials (34,010 women). Overall there is a 16% reduction in baby deaths in the antiplatelet group (RR 0.84, 95% CI 0.74 to 0.96); NNT 227 (128, 909)). Small-for-gestational age babies were reported in 32 trials (24,310 women), with an 8% reduction in risk (RR 0.92, 95% CI 0.85 to 1.00). There were no significant differences between treatment and control groups in any other measures of outcome.

REVIEWER'S CONCLUSIONS

Antiplatelet agents, in this review largely low-dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment is best started, and at what dose.

Elevated expression of integrin alpha(IIb) beta(IIIa) in drug-naïve, first-episode schizophrenic patients

BACKGROUND

Patients with schizophrenia have an increased risk over the general public of developing cardiovascular illness. It is unknown if there are functional changes in platelet surface receptors in schizophrenia. We therefore analyzed the surface expression of glycoprotein (GP)Ib, the integrin receptor alpha(IIb)beta(IIIa), CD62 (P-selectin), and CD63, and investigated platelet function in schizophrenic patients compared with healthy volunteers.

METHODS

Nineteen drug-naive, first-episode patients with a DSM IV diagnosis of paranoid schizophrenia were compared with matched healthy controls. Flow cytometry was used to assess platelet surface expression levels of GPIb, alpha(IIb)beta(IIIa), CD62, and CD63. Adenosine diphosphate-induced platelet aggregation was assayed.

RESULTS

The schizophrenic patients had a significantly (p < .0001) increased number of 68,145 +/- 8,260.1 alpha(IIb)beta(IIIa) receptors, platelet compared with 56,235 +/- 8,079.4 receptors, platelet in healthy controls.

CONCLUSIONS

Patients with schizophrenia have increased platelet expression of alpha(IIb)beta(IIIa), which may contribute to their increased risk of cardiovascular illness compared with the general population.

Flow cytometry of platelets for clinical analysis

Platelets are small, non-homogenous cells with distinctive surface features important to their essential role in hemostasis. The surface membrane is dynamic, and changes remarkably in lipid asymmetry and receptor expression on triggering of the activation process. There are also extensive and rapid intracellular changes in platelets as a result of biochemical activation through calcium fluxes, phospholipase activity, kinase activity, and phosphorylation mechanisms that lead to release of storage granule contents and generation of fast-acting prostaglandins, all in a matter of seconds after stimulation with a strong agonist. These characteristics make the platelet an interesting but difficult cell to study, and the explosion of knowledge over the last two decades has been fueled in large part by the application of flow cytometry techniques. Clinical applications of flow cytometry analysis of platelets have been pursued in individual specialized medical centers, but have not found widespread practice in clinical laboratories, mostly because of difficulties in standardization of techniques and the inherent biovariability in comparing normal to abnormal platelets. Despite these hurdles, it seems certain that flow cytometry analysis of platelets in pathological states will continue to evolve into more practical and robust procedures that will eventually become standard hematologic assays rather than specialized research tools.

Comparison of in vitro closure time (PFA-100) with whole blood electrical aggregometry and platelet surface antigen expression in healthy volunteers

It was the aim of this study to compare in vitro closure time (PFA-100), reflecting platelet-related primary hemostasis, to more platelet-specific tests like whole blood electrical aggregometry and platelet surface antigen expression in healthy volunteers. In vitro closure time was measured using a PFA-100. Platelet surface antigen expression (CD63, CD62-P, CD42b, CD36, CD31) was determined in accordance with the consensus protocol for flow-cytometric characterisation of platelet function. Platelet aggregometry was performed using a whole blood electrical aggregometer (ADP and arachidonic acid as agonists). Analysis of the obtained data revealed only a few significant correlations between the different platelet function tests used. This finding can be explained by the various aspects of platelet function being focused by these tests in different extents. Whenever platelet function is analysed, the investigator should be aware of the specific and limited evidence of the method used. For screening purposes, it may be useful to introduce a platelet function index, referring to basal platelet activity, platelet adhesion and platelet aggregation at low and high shear stress forces.

Platelet function during pregnancy: an evaluation using the PFA-100 analyser

In clinical practice, the only tests of platelet function are bleeding time and platelet number. Bleeding time lacks sensitivity and specificity but the PFA-100, an in vitro analyser of platelet function may be of value. This study aimed to evaluate any correlation between platelet number and function using the PFA-100 in pregnant women. During a 21-month period, platelet function was evaluated in whole blood as part of the pre-anaesthetic coagulation testing screen with the PFA-100 using collagen and epinephrine (PFA-EPI) or ADP (PFA-ADP) as platelet agonists. Thrombocytopenia was defined as a platelet number less than 150 G litre(-1). The patients were divided into four groups: Group I (n=110) normal pregnancy; Group II (n=38) thrombocytopenia of pregnancy; Group III (n=13) women with pre-eclampsia without thrombocytopenia; Group IV (n=19) women with pre-eclampsia and thrombocytopenia. Results are expressed as mean (SD). Platelet count was not statistically different between Groups II and IV (111.1 (23.1) vs 99.5 (28.0) G litre(-1)). PFA-EPI was statistically increased in Group II (124.0 (26.3) s), Group III (128.3 (17.9) s), and Group IV (143.6 (47.7) s) compared with normal pregnant patients (114.6 (27.3) s, P<0.05, Mann-Whitney U-test). PFA-ADP was statistically increased only in Group II compared with normal pregnant patients (90.5 (18.9) vs 80.2 (11.2) s, P<0.05). PFA values were increased above normal laboratory values in (four of 38) Group II patients and (six of 19) Group IV patients but in no patients in Group III. PFA-ADP results were correlated with platelet count only in Group IV (r=-0.74, P=0.0003). The increased PFA values and the correlation between PFA-ADP and platelet number in hypertensive thrombocytopenic women confirms that platelet function may be decreased in such patients. In patients with pregnancy-induced thrombocytopenia, platelet function may be preserved when the platelet count is as low as 60 G litre(-1).

Neonatal platelet activation in preeclampsia

Preeclampsia is associated with an increased platelet activation; however, there are few studies concerning platelet activation of the newborn. The aim of our study was to compare platelet activation in newborns of preeclamptic mothers to newborns of healthy mothers by using whole blood flow cytometry. Blood samples were obtained from 20 newborns (10 healthy controls, 10 cases of preeclampsia/HELLP [hemolysis, elevated liver enzymes, and low platelet count] syndrome) during cesarean section. Antibodies against the following antigens were used as markers for platelet activation: CD 41, CD62P, CD 63, and platelet-bound fibrinogen. In addition to the basal platelet activation, the ability of platelets to undergo activation as a result of in vitro incubation with a weak agonist (adenosine diphosphate) was evaluated. A significant difference between the groups concerning basal platelet activation could only be seen for platelet-bound fibrinogen; the control group showed a higher extent of platelet activation (16.6 +/- 11.3 vs. 6.1 +/- 4.9; p = 0.03). Incubation with adenosine diphosphate in the control group resulted in minor increases of platelet activation, which was significant only for platelet-bound fibrinogen (16.6 +/- 11.3 vs. 42.5 +/- 22.1; p = 0.02). However, the preeclamptic group showed significantly increased levels of platelet activation for all used markers after in vitro activation (CD 41: 115.6 +/- 18.2 vs. 163.2 +/- 29.6; p = 0.002; CD62P: 2.4 +/- 0.4 vs. 3.9 +/- 0.3; p < 0.001; CD 63: 2.7 +/- 0.5 vs. 3.7 +/- 0.6; p = 0.002; platelet-bound fibrinogen: 6.1 +/- 4.9 vs. 55.1 +/- 9.1; p < 0.001). Preeclampsia or HELLP syndrome is therefore associated with an increased susceptibility to neonatal platelets, even against weak activators such as adenosine diphosphate. Whether this results from peculiarities in the fetal vascular environment or maternal influences is yet uncertain.

The use of platelet density and volume measurements to estimate the severity of pre-eclampsia

BACKGROUND

This study evaluated whether it is possible to estimate the severity of pre-eclampsia through in vitro measurements of platelet and granulocyte parameters.

EXPERIMENTAL PROTOCOL

Eighteen pre-eclamptic women in the third-trimester of pregnancy and 11 women in the third-trimester of normal pregnancies were included in the study. Three to 12 months after delivery, 15 patients with pre-eclampsia and all the subjects with normal pregnancies were re-examined. Before delivery, peak platelet density was determined using a specially designed apparatus. Before and 3-12 months after delivery the following were measured: platelet counts, mean platelet volume and neutrophil and monocyte counts. Furthermore, circulating P-selectin, interleukin-6 and myeloperoxidase were determined to estimate platelet, monocyte and granulocyte activities, respectively.

RESULTS

Compared to their results after delivery, pre-eclamptic females demonstrated lower platelet counts (P < 0.001) and raised mean platelet volumes (P < 0.01). Both pre-eclamptic women (P < 0.01) and normal pregnancies (P < 0.05) demonstrated elevated soluble P-selectin at pregnancy. Then pre-eclamptic women had advanced neutrophil counts (P < 0.01) but normal pregnancies showed a similar phenomenon (P < 0.001). Interleukin-6 remained normal during pregnancy. Plasma myeloperoxidase levels were lower both in pre-eclampsia (P < 0.05) and in normal pregnancies (P < 0.001). In pre-eclampsia elevated blood pressure was related to higher mean platelet volumes (P < 0.05). Furthermore, a group of pre-eclamptic females whose platelets had disturbed density distribution displayed elevated mean platelet volumes (P < 0.01).

CONCLUSIONS

The present work demonstrates considerable platelet alterations in pre-eclampsia. We failed to show granulocyte involvement in the pathogenesis of the disease. Severe pre-eclampsia is related to elevated mean platelet volumes. The latter parameter is associated with disturbed density distribution. It appears possible to estimate disease severity from measurements of platelet density and volume.

Early detection of preeclampsia by determination of platelet aggregability

Preeclampsia is still a leading cause of maternal and fetal morbidity and mortality. There is evidence for the involvement of platelets. Therefore, we investigated the suitability of corrected whole blood impedance aggregometry as an early predictor of preeclampsia in 71 consecutive, high-risk pregnancies. According to the occurrence of preeclampsia, defined postpartum by an independent investigator, and the stage of pregnancy (early and late, cutoff: 25 weeks of gestation), four study groups were defined. Platelet aggregation data were corrected for the influence of hematocrit and platelet count by a special purpose software package. Women developing preeclampsia showed significantly higher platelet aggregation response compared to controls in early and late pregnancy. In early pregnancy, all women developing preeclampsia had aggregation responses to collagen higher than the highest responses among the controls. Hence, this test had a 100% positive predictive value of subsequent preeclampsia. Despite being significantly increased, platelet aggregability was of minor predictive value in late pregnancy. We conclude that preeclampsia is accompanied by exaggerated platelet aggregability, particularly perceptible early in the course of pregnancy. We propose collagen-induced whole blood platelet aggregation with correction for the influence of hematocrit and platelet count for early detection of preeclampsia.

Antiplatelet agents for preventing and treating pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, and low dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia, and to those with established pre-eclampsia.

SEARCH STRATEGY

This review drew on the search strategy developed for the Pregnancy and Childbirth Group as a whole. The Cochrane Controlled Trials Register was also searched, The Cochrane Library 1999 Issue 1, Embase was searched from 1994-1999 and hand searches were performed of the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia, and those with pre-eclampsia before delivery. Women treated postpartum were excluded. Interventions were any comparisons of an antiplatelet agent (such as low dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Assessment of trials for inclusion in the review and extraction of data was performed independently and unblinded by two reviewers. Data were entered into the Review Manager software and double checked.

MAIN RESULTS

Forty two trials involving over 32,000 women were included in this review, with 30,563 women in the prevention trials. There is a 15% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents [32 trials with 29,331 women; relative risk (RR) 0.85, 95% confidence interval (0.78, 0.92); Number needed to treat (NNT) 89, (59, 167)]. This reduction is regardless of risk status at trial entry or whether a placebo was used, and irrespective of the dose of asprin or gestation at randomisation. Twenty three trials (28,268 women) reported preterm delivery. There is a small (8%) reduction in the risk of delivery before 37 completed weeks [RR 0.92, (0.88, 0.97); NNT 72 (44, 200)]. Baby deaths were reported in 30 trials (30,093 women). Overall there is a 14% reduction in baby deaths in the antiplatelet group [RR 0.86, (0. 75, 0.98); NNT 250 (125, >10000)]. Small for gestational age babies were reported in 25 trials (20,349 women), with no overall difference between the groups, RR 0.92, (0.84, 1.01). There were no significant differences between treatment and control groups in any other measures of outcome. Five trials compared antiplatelet agents with placebo or no antiplatelet agent for the treatment of pre-eclampsia. There are insufficient data for any firm conclusions about the possible effects of these agents when used for treatment of pre-eclampsia.

REVIEWER'S CONCLUSIONS

Antiplatelet agents, in this review largely low dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment should be started, and at what dose.

Platelet dense granules: structure, function and implications for haemostasis

The advances that have been made over the last decade in microscopic, biochemical, molecular, and genetic techniques have led to substantial improvement in our understanding of platelet dense granule structure and function, and the implications of dense granule deficiencies for haemostasis. However, much has still to be learned. For example, what is the specific mechanism of docking and fusion that occurs during dense granule exocytosis? What are the roles of dense granule membrane proteins during exocytosis or after expression on the surface of activated platelets? Finally, how do the genetic defects identified in HPS and CHS result in the clinical phenotype of these diseases, and what does this tell us about the origin and function of the affected subcellular organelles?