Platelet activation and endogenous thrombin potential in pre-eclampsia

High Levels of Triggering Receptor Expressed in Myeloid Cells-Like Transcript-1 Positive, but Not Glycoprotein 1b+, Microparticles Are Associated With Poor Outcomes in Acute Respiratory Distress Syndrome

OBJECTIVES

To identify triggering receptor expressed in myeloid cells-like transcript-1 positive (TLT-1+) microparticles (MPs) and evaluate if their presence is associated with clinical outcomes and/or disease severity in acute respiratory distress syndrome (ARDS).

DESIGN

Retrospective cohort study.

SETTING

ARDS Network clinical trials.

PATIENTS

A total of 564 patients were diagnosed with ARDS.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Using flow cytometry, we demonstrated the presence of TLT-1+ platelet-derived microparticles (PMP) that bind fibrinogen in plasma samples from fresh donors. We retrospectively quantified TLT-1, glycoprotein (Gp) 1b, or αIIbβIIIa immunopositive microparticles in plasma samples from patients with ARDS enrolled in the ARMA, KARMA, and LARMA (Studies 01 and 03 lower versus higher tidal volume, ketoconazole treatment, and lisofylline treatment Clincial Trials) ARDS Network clinical trials and evaluated the relationship between these measures and clinical outcomes. No associations were found between Gp1b+ MPs and clinical outcomes for any of the cohorts. When stratified by quartile, associations were found for survival, ventilation-free breathing, and thrombocytopenia with αIIbβIIIa+ and TLT-1+ MPs (χ2p < 0.001). Notably, 63 of 64 patients in this study who failed to achieve unassisted breathing had TLT+ PMP in the 75th percentile. In all three cohorts, patients whose TLT+ MP counts were higher than the median had higher Acute Physiology and Chronic Health Evaluation III scores, were more likely to present with thrombocytopenia and were 3.7 times (p < 0.001) more likely to die than patients with lower TLT+ PMP after adjusting for other risk factors.

CONCLUSIONS

Although both αIIbβIIIa+ and TLT+ microparticles (αIIbβIIIa, TLT-1) were associated with mortality, TLT-1+ MPs demonstrated stronger correlations with Acute Physiology and Chronic Health Evaluation III scores, unassisted breathing, and multiple system organ failure. These findings warrant further exploration of the mechanistic role of TLT-1+ PMP in ARDS or acute lung injury progression.

Platelet indices and angiogenesis markers in hypertensive disorders of pregnancy

INTRODUCTION

Activated platelets exert a key role in the pathogenesis of preeclampsia (PE). There is evidence of distinctive patterns of platelet indices in PE in comparison to healthy pregnancies, therefore these indices can be potential tools for PE detection, risk stratification, and management. Considering the vascular aspects of its pathophysiology, PE is characterized by the increased levels of soluble FMS-like tyrosine kinase-1 (sFlt-1) an antiangiogenic factor, and reduced placental growth factor (PlGF), a proangiogenic factor. This study aimed to assess the platelet indices in hypertensive disorders of pregnancy (HDP) and its correlation with angiogenesis-related biomarkers.

METHODS

The groups for the study were: control (n = 114); gestational hypertension; (n = 112), and PE (n = 42). The platelet indices included were platelet counts (PLT-I and PLT-F), mean platelet volume (MPV), platelet distribution width (PDW), plateletcrit (PCT), platelet large cell ratio (P-LCR), and immature platelet fraction (IPF# and IPF%). Serum levels of sFlt-1 and PlGF were assessed.

RESULTS

PLT-I, PLT-F, and PCT% were lower in PE, while MPV, PDW, P-LCR, IPF%, and IPF# were increased. The parameter MPV presented the best performance for the discrimination of PE. There was a moderate positive correlation between sFlt-1 levels and MPV, PDW, and P-LCR.

CONCLUSION

Platelet indices can be potentially applied as additional tools for the diagnosis and management of HDP. Activated platelets may act as an extra source of sFlt-1 in PE.

Hemostasis in Pre-Eclamptic Women and Their Offspring: Current Knowledge and Hemostasis Assessment with Viscoelastic Tests

Pre-eclampsia (PE) is a placenta-mediated disease and remains a major cause of maternal and neonatal mortality and morbidity. As PE develops, normal pregnancy's hypercoagulable balance is disrupted, leading to platelet hyperactivation, excessive pathological hypercoagulability, and perturbed fibrinolysis. This narrative review aims to summarize the current knowledge regarding hemostasis in PE compared with healthy gestation and the potential effects of maternal PE on neonatal hemostasis. Finally, it aims to discuss hemostasis assessments for normal pregnancies and PE, emphasizing the role of viscoelastic tests, namely, thromboelastography (TEG) and thromboelastometry (ROTEM), for monitoring PE-associated hemostatic alterations. The use of TEG/ROTEM for assessing the hemostatic profile of PE women has been little considered, even though conventional coagulation tests (CCTs) have not helped to monitor hemostasis in this population. Compared with normal pregnancy, TEG/ROTEM in PE reveals an excessive hypercoagulability analogous with the severity of the disease, characterized by higher-stability fibrin clots. The TEG/ROTEM parameters can reflect PE severity and may be used for monitoring and as predictive markers for the disease.

Increased contact activated endogenous thrombin potential in pregnant women with preeclampsia

Preeclampsia is a worldwide contributor to maternal and fetal morbidity and mortality. Women with preeclampsia are in a hyper-coagulable state with increased risk of thromboembolic disease later in life compared with normal pregnant women. The contact system (CAS) in plasma can mediate thrombin generation and is an important contributor to thrombus growth, but the activation of CAS during pregnancy complicated by preeclampsia is not yet elucidated, and CAS may play a role in the pathophysiology of preeclampsia. Therefore, the aim of the study is to address thrombin generation, and in particular, the capacity of the CAS-mediated pathway in patients with preeclampsia compared with pregnant controls. One hundred and seventeen women with preeclampsia and matched controls were included. The project was registered at www.clinicaltrials.gov as NCT04825145. CAS and tissue factor induced thrombin generation, proteins C and S, antithrombin, and histidine-rich glycoprotein (HRG) were assessed. Women with preeclampsia had significantly increased CAS and tissue factor-induced endogenous thrombin potential (ETP), and HRG compared with controls, P  = 0.022, P  = 0.024, and P  = 0.02, respectively. The concentrations of protein C and antithrombin were significantly reduced in the preeclampsia group, P  = 0.024 and P  < 0.0001, respectively. No significant difference in the concentration of protein S was detected, P  = 0.06. This study demonstrates a significant increased CAS-induced ETP and an overall decrease of important regulators of coagulation in women with preeclampsia compared with controls. These aspects can contribute to the hyper-coagulable state characterizing preeclampsia.

Women with severe postpartum hemorrhage have a decreased endogenous thrombin potential before delivery

BACKGROUND

Severe postpartum hemorrhage (PPH), defined as a blood loss ≥1000 mL, is associated with maternal morbidity and mortality.

OBJECTIVES

We aimed at characterizing coagulation properties of predelivery plasmas from pregnant women with thrombin generation assay and hemostatic biomarkers (plasminogen activator inhibitor-1, tissue factor [TF], and thrombomodulin).

METHODS

A nested case-control study was conducted within the "Study of Biological Determinants of Bleeding Postpartum," a French prospective cohort study, in order to compare women with severe PPH (cases) and controls matched for age, body mass index, term, and mode of delivery. Plasma was collected at entry in the delivery room, and blood loss was measured objectively. The predelivery endogenous thrombin generation potential (ETP) was measured in plasma using calibrated automated thrombinography and low TF concentration. Hemostatic biomarkers were measured using ELISA kits.

RESULTS

A total of 142 women (71 cases and 71 controls) were investigated. There was no difference in the median lag phase, thrombin peak, and time to peak between cases and controls. However, median predelivery ETP was lower in cases than in controls (2170 vs 2408 nM.min, P < .0001), independently of mode of delivery and PPH etiology. Median plasminogen activator inhibitor-1 and TF levels were higher in cases compared with controls (107.4 vs 68.1 ng/mL, P = .0003; 34.4 vs 27.4 pg/mL, P = .007), whereas thrombomodulin levels did not differ between the 2 groups.

CONCLUSION

Among thrombin generation assay parameters, predelivery ETP levels may have a predictive value for severe PPH.

Overexpression of facilitative glucose transporter-3 and membrane procoagulation in maternal platelets of preeclamptic pregnancy

BACKGROUND

Preeclampsia (PE) is a hypertensive disorder during pregnancy that results in significant adverse maternal and neonatal outcomes. Platelet activation is present in PE and contributes to the thrombo-hemorrhagic states of the disorder. However, the mechanisms that initiate and/or sustain platelet activation in PE are ill-defined.

OBJECTIVES

We aimed to characterise this mechanism and the procoagulant potentials of platelets in PE.

METHODS

In this quantitative observational study, we analyzed platelet procoagulant membrane dynamics in patients with PE (n = 21) compared with age-matched normotensive pregnancies (n = 20), gestational hypertension (n = 10), and non-pregnant female controls (n = 19). We analyzed fluorescently labeled indicators of platelet activation, bioenergetics, and procoagulation (phosphatidylserine exposure and thrombin generation), coupled with high-resolution imaging and thrombelastography. We then validated our findings using flow cytometry, immunoassays, classical pharmacology, and convolutional neural network analysis.

RESULTS

PE platelets showed significant ultra-structural remodeling, are more extensively preactivated than in healthy pregnancies and can circulate as microaggregates. Preactivated platelets of PE externalized phosphatidylserine and thrombin formed on the platelet membranes. Platelets' expression of facilitative glucose transporter-1 increased in all pregnant groups. However, PE platelets additionally overexpress glucose transporter-3 to enhance glucose uptake and sustain activation and secretion events. Although preeclampsia platelets exposed to subendothelial collagen showed incremental activation, the absolute hemostatic response to collagen was diminished, and likely contributed to greater blood loss perioperatively.

CONCLUSIONS

We revealed 2 bioenergetic mediators in the mechanism of sustained platelet procoagulation in preeclampsia. Although glucose transporter-1 and glucose transporter-3 remain elusive antiprocoagulant targets, they may be sensitive monitors of PE onset and progression.

Perturbations in kinetics of the thrombin generation assay identify women at risk of preeclampsia in the first trimester and provide the rationale for a preventive approach

BACKGROUND

Activation of the coagulation system and increased thrombin generation have been implicated in the pathophysiology of preeclampsia, and this rationale supports the administration of low-molecular-weight heparin to prevent this syndrome in patients at risk. Yet, randomized trials of this prophylactic measure have yielded contradictory results. A possible explanation is that only a subset of patients with preeclampsia have excessive thrombin generation and would benefit from the administration of low-molecular-weight heparin. Therefore, the key questions are whether and when patients who subsequently develop preeclampsia present evidence of abnormal thrombin generation.

OBJECTIVE

This study aimed to determine (1) the kinetics of thrombin generation throughout gestation in women with a normal pregnancy and in those with early and late preeclampsia, and (2) the diagnostic performance of in vivo thrombin generation parameters to predict the development of preeclampsia.

STUDY DESIGN

This retrospective, nested case-control study was based on a prospective longitudinal cohort of singleton gestations. Cases comprised women who developed preeclampsia (n=49), and controls consisted of patients with a normal pregnancy (n=45). Preeclampsia was classified into early-onset (n=24) and late-onset (n=25). Longitudinal changes in the parameters of the thrombin generation assay (lag time, time to peak thrombin concentration, peak thrombin concentration, endogenous thrombin generation, and velocity index) throughout gestation were compared between the study groups, and normal pregnancy percentiles were derived from the control group. We tested whether a single parameter or a combination of parameters, derived from the kinetics of thrombin generation, could identify patients who subsequently developed preeclampsia. Time-related parameters <10th percentile were considered short, and concentration-related parameters >90th percentile were considered high.

RESULTS

(1) Patients who developed preeclampsia (early- and late-onset) had abnormal thrombin generation kinetics as early as 8 to 16 weeks of pregnancy; (2) patients with a combination of a short lag time and high peak thrombin concentration at 8 to 16 weeks of pregnancy had an odds ratio of 43.87 for the subsequent development of preeclampsia (area under the curve, 0.79; sensitivity, 56.8%; specificity, 92.7%; positive likelihood ratio, 7.76); (3) at 16 to 22 weeks of gestation, patients with a combination of a short lag time and a high velocity index had an odds ratio of 16 for the subsequent development of preeclampsia (area under the curve, 0.78; sensitivity, 62.2%; specificity, 92.5%; positive likelihood ratio, 8.29).

CONCLUSION

During early pregnancy, the thrombin generation assay can identify the subset of patients at a greater risk for the development of preeclampsia owing to accelerated and enhanced production of thrombin. This observation provides a rationale for testing the efficacy of low-molecular-weight heparin in this subset of patients. We propose that future research on the efficacy of low-molecular-weight heparin and other interventions targeting the coagulation system to prevent preeclampsia should be focused on patients with abnormal kinetics of thrombin generation.

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.

Platelet protease activated receptor 4 (PAR 4) receptor genotype is associated with an increased risk of preterm birth

BACKGROUND

Platelet protease activated receptor-4 (PAR4) Thr120 is a common genetic variant associated with increased platelet activity. Increased platelet activity is implicated in the pathogenesis of preeclampsia and preterm birth.

OBJECTIVE

Compare the rate of preeclampsia and preterm birth in pregnant individuals homozygous for PAR4 Thr120 variant vs not.

STUDY DESIGN

This is a prospective cohort study of patients who delivered November 2020-July 2021. Maternal blood collected on admission for PAR4 genotyping. The primary outcome was the rate of preeclampsia/gestational hypertension in those with Thr/Thr genotype compared with Ala/Thr or Ala/Ala. Secondary outcomes included rates of preterm birth and placental pathology.

RESULTS

Three hundred and twenty singletons were included and 52 (16.3%) were PAR4 Thr/Thr. Those PAR4 Thr/Thr were more likely to be Black (67.3% vs 29.5%, p < .001), younger (28 ± 6 vs 31 ± 6, p = .004), and have higher body mass index (35.2 ± 6.8 vs 33.1 ± 7.4, p = .047). There was no difference in preeclampsia/gestational hypertension (19.2% vs 22.8%, p = .705). Those Thr/Thr had a significantly higher rate of preterm birth (15.4% vs 3.7%, adjusted odds ratio [aOR] 4.04 [1.47-11.10], p = .007), indicated preterm birth because of fetal growth restriction or preeclampsia (5.8% vs 0.4%, aOR 10.03 [1.48-67.87], p = .02), spontaneous preterm birth (7.7% vs 2.2%, aOR 4.81 [1.27-18.27], p = .02), and placental intervillous thrombosis (18.5% vs 7.9%, aOR 4.12 [1.14-14.92], p = .03).

CONCLUSION

Platelet receptor PAR4 Thr120 is a common variant associated with an increased risk of placental vascular pathology and preterm birth in homozygous individuals. Although a cohort study cannot establish causation, this strong association warrants further exploration.

Risk stratification for pregnancy-associated venous thromboembolism: Potential role for global coagulation assays

Risk assessment for venous thromboembolism in pregnancy and the puerperium is currently limited to stratifying clinical surrogate risk factors without high-quality evidence. While the absolute risk of pregnancy-associated venous thromboembolism is low for the vast majority of women, associated morbidity and mortality remains significant. As guidelines for thromboprophylaxis vary widely, some women may be under- or over-anticoagulated, contributing to poor outcomes. New global coagulation assays provide a holistic view of coagulation and may have the potential to detect hypercoagulability in pregnancy, unlike clinically available coagulation assays. However, there are major technical challenges to overcome before global coagulation assays can be realistically proposed as an adjunct to risk assessment for pregnancy-associated venous thromboembolism. This review summarises the literature and controversies in the prediction and prevention of pregnancy-associated venous thromboembolism and outlines the new tools in haematology that may assist in our future understanding of hypercoagulability in pregnancy.

Immature Platelet Fraction and Thrombin Generation: Preeclampsia Biomarkers

Preeclampsia, a human pregnancy syndrome, is characterized by elevated blood pressure and proteinuria after the 20th week of gestation. Its etiology remains unknown, and its pathophysiological mechanisms are related to placental hypoperfusion, endothelial dysfunction, inflammation, and coagulation cascade activation. Recently, the role of the complement system has been considered. This syndrome is one of the main causes of maternal and fetal mortality and morbidity. This article discusses the hypothesis of preeclampsia being triggered by the occurrence of inadequate implantation of the syncytiotrophoblast, associated with bleeding during the first stage of pregnancy and with augmented thrombin generation. Thrombin activates platelets, increasing the release of antiangiogenic factors and activating the complement system, inducing the membrane attack complex (C5b9). Immature platelet fraction and thrombin generation may be possible blood biomarkers to help the early diagnosis of preeclampsia.

Preliminary Interpretations of Epigenetic Profiling of Cord Blood in Preeclampsia

Preeclampsia (PE) is characterized by new-onset hypertension after 20 weeks of pregnancy and results in high maternal and fetal mortality worldwide. It has been reported that PE is associated with abnormalities in the umbilical cord and cord blood. However, previous studies were focused primarily on the transcriptomics level, while the underlying gene regulatory landscapes are still unclear. Thus, we performed the Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) using the umbilical cord blood samples collected from a patient with superimposed PE and three healthy donors to uncover the chromatin accessibility changes attributed to PE. We have identified genes associated with immunomodulation and hypoxia response that have higher chromatin accessibility close to their transcription start sites. Motif analysis indicated that the GATA family transcription factor binding was enriched in PE and may play an essential regulatory role in the disease progression. Overall, our findings provide an overview of gene regulatory programs and the corresponding downstream pathways associated with PE that may influence the placenta function and fetal growth.

Triggering receptor expressed on myeloid cells (TREM) like transcript-1 (TLT-1) reveals platelet activation in preeclampsia

Triggering receptor expressed on myeloid cells (TREM) like transcript-1 (TLT-1) is a membrane protein receptor found in α-granules of megakaryocytes and platelets. Upon platelet activation TLT-1 is rapidly relocated to the surface of platelets. In plasma, a soluble form of TLT-1 (sTLT-1) is present. Plasma levels of sTLT-1 are significantly elevated in thrombotic diseases. In the present study, we investigated to whether TLT-1 reflects platelet activation in pregnant women with preeclampsia. We studied 30 preeclamptic patients who were matched with 30 normotensive pregnant women and 30 non-pregnant controls. Basal TLT-1, P-selectin, and CD63 expressions on platelets were analyzed with the use of flow-cytometry (FCM). Platelet reactivity was induced by thrombin receptor activation peptide and determined by FCM. Plasma concentrations of sTLT-1 and soluble P-selectin (sP-selectin) were measured by an enzyme-linked immunosorbent assay. Results show that basal platelet expression of TLT-1, P-selectin and CD63 were increased in women with preeclampsia (PE) compared with normotensive pregnant women (NP). Platelets from PE women and NP women were more responsive compared to from nonpregnant women controls (NC), and which was demonstrated by increased expression of TLT-1, P-selectin, and CD63 upon stimulation in vitro. Plasma concentration of sTLT-1 was greater in PE women compared to NP women and NC women. Plasma sP-selectin level was higher in pregnant women than in nonpregnant women, but there were no significant differences between PE and NP women. In summary, our results revealed that platelet activation is prominent in preeclampsia, TLT-1 reflects platelet activation and may be a useful indicator for preeclampsia.

Endothelial Cell Activation and Thrombin Generation Assessment for the Risk of Severe Early Onset Preeclampsia. the ROADMAP-EOP Study

Background

The ROADMAP-EOP study aimed to identify clinically relevant biomarkers of hypercoagulability for the identification of pregnant women at risk of early onset preeclampsia worsening.

Methods

The ROADMAP-EOP observational single center retrospective case–control study was conducted in Greece (Centre for Human Reproduction, Genesis Athens Clinic, Athens, Greece) from July 2020 to July and enrolled pregnant women diagnosed with EOP stratified in mild EOP group (n = 34) and severe EOP group (n = 15) as well as women with uncomplicated pregnancy (control group; n = 35). All women were assessed with thromboelastometry (ROTEM®), Calibrated Automated Thrombogram®, tissue factor activity (TFa), procoagulant phospholipid dependentclotting time (Procoag-PPL®), Proteins S (PS), TFPI, D-dimer, antithrombin (AT), thrombomodulin (TM), fibrinogen, prothrombin time (PT) and activated partial thromboplastin time (aPTT). The primary study end-point was severe earlyonset preeclampsia. Principal component analysis (PCA) was performed.

Results

The PCA analysis showed that a score composed of the lag-time, ttPeak and Procoag-PPL accurately predicted severe EOP (sensitivity 71.4%, specificity 61.8%, and AUC of the ROC analysis 0.953).

Conclusion

The pilot ROADMAP-EOP shows that activation of endothelial cells and blood hypercoagulability are driven events in the worsening of EOP. Among a large panel of biomarkers and coagulation assays, thrombingeneration test and procoagulant phospholipid dependent clotting time emerged as clinically relevant for the evaluation of the risk of severe EOP. This methodology for the development of a new clinic-biological risk assessment model for prompt identification of pregnant women at risk of severe EOP must be validated in a large multi-centerprospective study.

Phosphatidylserine Exposing Extracellular Vesicles in Pre-eclamptic Patients

Background: Pre-eclampsia (P-EC) is associated with systemic inflammation, endothelial dysfunction and hypercoagulability. The role of extracellular vesicles (EVs) in coagulation disturbances affecting the development and severity of P-EC remains elusive. We aimed to evaluate the concentration of EVs expressing phosphatidylserine (PS) and specific markers in relation to the thrombin and fibrin formation as well as fibrin clot properties, in pregnant women with P-EC in comparison to healthy pregnant women of similar gestational age.

Methods: Blood samples of 30 pregnant women diagnosed with P-EC were collected on the morning following admission to hospital and after delivery (mean duration 5 days). The concentration of the PS-exposing EVs (PS+ EVs) from platelets (CD42a⁺, endothelial cells (CD62E⁺), and PS+ EVs expressing tissue factor (TF) and vascular cell adhesion molecule 1 (VCAM-1) were measured by flow cytometry. Further phenotyping of EVs also included expression of PlGF. Markers of maternal haemostasis were correlated with EVs concentration in plasma.

Results: Preeclamptic pregnancy was associated with significantly higher plasma levels of PS+ CD42a⁺ EVs and PS+ VCAM-1⁺ EVs in comparison with normotensive pregnancy. P-EC patients after delivery had markedly elevated concentration of PS+ CD42a⁺ EVs, CD62E⁺ EVs, TF⁺ EVs, and VCAM-1⁺ EVs compared to those before delivery. Inverse correlation was observed between EVs concentrations (PS+, PS+ TF⁺, and PlGF⁺) and parameters of overall haemostatic potential (OHP) and fibrin formation, while PS+ VCAM-1⁺ EVs directly correlated with FVIII activity in plasma.

Conclusion: Increased levels of PS+ EVs subpopulations in P-EC and their association with global haemostatic parameters, as well as with fibrin clot properties may suggest EVs involvement in intravascular fibrin deposition leading to subsequent microcirculation disorders.

Release of α-granule contents during platelet activation

Upon activation, platelets release a plethora of factors which help to mediate their dynamic functions in hemostasis, inflammation, wound healing, tumor metastasis and angiogenesis. The majority of these bioactive molecules are released from α-granules, which are unique to platelets, and contain an incredibly diverse repertoire of cargo including; integral membrane proteins, pro-coagulant molecules, chemokines, mitogenic, growth and angiogenic factors, adhesion proteins, and microbicidal proteins. Clinically, activation of circulating platelets has increasingly been associated with various disease states. Biomarkers indicating the level of platelet activation in patients can therefore be useful tools to evaluate risk factors to predict future complications and determine treatment strategies or evaluate antiplatelet therapy. The irreversible nature of α-granule secretion makes it ideally suited as a marker of platelet activation. This review outlines the release and contents of platelet α-granules, as well as the membrane bound, and soluble α-granule cargo proteins that can be used as biomarkers of platelet activation.

Platelet-derived extracellular vesicles may contribute to the hypercoagulable state in preeclampsia

It has previously been shown that preeclampsia is associated with disturbed hemostasis and that extracellular vesicles (EVs) play important role in the regulation of hemostatic homeostasis. Thus, we hypothesized that the altered procoagulant characteristics of circulating platelet-derived EVs may contribute to the disturbed hemostasis in preeclampsia. Using multicolor flow cytometry, we have analyzed both tissue factor expressing procoagulant EVs and platelet-derived EV subpopulations derived from resting and activated thrombocytes by examining them in plasma samples of preeclamptic patients and pregnancy-matched healthy individuals. Compared to pregnancy-matched healthy individuals in preeclamptic patients a significantly (p < 0.05) higher ratio of Annexin-V positive activated platelets and a higher number of CD142⁺ tissue factor bearing procoagulant EVs were found, whereas the absolute amount of circulating CD41a⁺ platelet-derived EVs and CD62P⁺/CD41a⁺ EVs produced by activated thrombocytes was significantly lower in the plasma of preeclamptic women. In the plasma samples, there was no significant difference in the amount of CD63⁺ platelet-derived EVs. We propose that increased platelet activation and tissue factor expression of platelet derived extracellular vesicles may contribute to the hypercoagulable state observed in preeclampsia.

The association of antenatal D-dimer and fibrinogen with postpartum hemorrhage and intrauterine growth restriction in preeclampsia

BACKGROUND

D-dimer and fibrinogen were verified to be altered in preeclampsia. This study was to evaluate the associations of D-dimer and fibrinogen plasma levels with postpartum hemorrhage or intrauterine growth restriction in preeclamptic women.

METHODS

This was a retrospective study that recruited 278 preeclamptic women with singleton pregnancy from January 2016 to December 2019. Patients were allocated into five groups: mild preeclampsia (mPE) (n=68), mild preeclampsia with postpartum hemorrhage (mPE+PPH) (n=13), severe preeclampsia (sPE) (n=112), severe preeclampsia with postpartum hemorrhage (sPE+PPH) (n=17) and severe preeclampsia with intrauterine growth restriction (sPE+IUGR) (n=68). The antenatal D-dimer and fibrinogen plasma levels were analyzed among the groups. Logistic regression was used to determine the correlation between serum indexes and PPH or IUGR in preeclampsia.

RESULTS

The antenatal D-dimer plasma levels were significantly higher in the sPE+PPH group than that in the sPE group (2.02 μg/ml versus 1.37 μg/ml, P = 0.001), but there was no difference in fibrinogen. Elevated D-dimer was associated with PPH among severe preeclamptic women (adjusted odds ratio (aOR) [95% CI]: 3.093 [1.527-6.264], P = 0.002). No differences in D-dimer and fibrinogen were found between the mPE and mPE+PPH groups or between the sPE and sPE+IUGR groups.

CONCLUSIONS

Elevated antenatal plasma D-dimer level may be associated with postpartum hemorrhage in severe preeclampsia, but not with intrauterine growth restriction. Future prospective clinical trials are needed to investigate the predictive value of D-dimer in postpartum hemorrhage in severe preeclampsia.

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.

Pregnancy induced TMA in severe preeclampsia results from complement-mediated thromboinflammation

Preeclampsia is a multifactorial vascular disease unique to human pregnancy. While genetic and antiangiogenic factors are important contributors to preeclampsia susceptibility, recent studies have shown that dysregulation and/or over-activation of the complement system has an integral role in disease etiology. Furthermore, the role of the coagulation cascade may be underappreciated in the development of the disease. Traditionally, for research purposes, the pool of preeclampsia cases has been divided into non-severe and severe disease depending on the onset and severity of the symptoms. However, of particular interest are a small but important minority of cases that present with symptoms likening to those of hemolysis, elevated liver enzymes and low platelets syndrome, atypical hemolytic uremic syndrome, or thrombotic thrombocytopenic purpura, all thrombotic microangiopathy (TMA) diseases, with the hallmark mechanisms of endothelial dysfunction and aberrant activation of complement and coagulation cascades. We therefore propose a third class, severe TMA-like preeclampsia to be included in the categorization of preeclampsia patients. Identifying these patients would target research, diagnostic differentiation, and novel treatment options to the subclass of patients with life-threatening disease that are most likely to benefit from next-generation drug development.

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.

Assessing maternal clotting function with novel global coagulation assays: A prospective pilot study

INTRODUCTION

Women are at higher risk of venous thromboembolism (VTE) during pregnancy and the puerperium. Global coagulation assays (GCAs), including thromboelastography (TEG), thrombin generation using the calibrated automated thrombogram (CAT) and fibrin generation using the overall haemostatic potential assay (OHP), provide a more comprehensive assessment of the coagulation process than conventional coagulation assays. We aimed to evaluate the ability of these GCAs to analyse the coagulability among pregnant women of varying VTE risk profile.

METHODS

Women undergoing term elective caesarean delivery provided a single predelivery blood sample for conventional and novel coagulation testing (TEG, CAT and OHP). Data from 47 healthy nonpregnant women aged 18-45 years were used as controls.

RESULTS

Sixty women with term singleton pregnancies were included. Samples from pregnant women were hypercoagulable on most GCA parameters compared to nonpregnant controls, demonstrating increased maximum amplitude (clot strength) (71.5 vs 60.6 mm, P < .001) on whole blood TEG and increased endogenous thrombin potential (1895.22 vs 1399.33 nmol/L·min, P < .001) and overall coagulation potential (fibrin generation) (57.58 vs 36.21 units, P < .001) on platelet-poor plasma. Pregnant women with booking BMI ≥ 30 kg/m² had significantly higher maximum amplitude compared to pregnant women of normal BMI (18.5-25 kg/m² ) (73.2 vs 66.1 mm, P < .001).

CONCLUSIONS

Global coagulation assays reliably detect the physiological hypercoagulability of pregnancy. Thromboelastography in particular appears to correlate with obesity in the pregnant population. GCAs may be potential adjuncts to risk factor-based criteria to guide VTE thromboprophylaxis during pregnancy and the puerperium.

Platelet activation and placenta-mediated adverse pregnancy outcomes: an ancillary study to the Effects of Aspirin in Gestation and Reproduction trial

BACKGROUND

Platelet activation may play a role in the pathophysiology of placenta-mediated obstetrical complications, as evidenced by the efficacy of aspirin in preventing preeclampsia, but published data regarding the relationship between biomarkers for platelet activation and adverse obstetrical outcomes are sparse. In particular, it is unknown whether prepregnancy biomarkers of platelet activation are associated with adverse pregnancy outcomes.

OBJECTIVE

This study aimed to determine the following: (1) whether maternal plasma concentrations of platelet factor 4 are associated with risk of placenta-mediated adverse obstetrical outcomes, and (2) whether these associations are modified by low-dose aspirin.

STUDY DESIGN

This ancillary study included measurement of platelet factor 4 among 1185 of 1228 women of reproductive age enrolled in the Effects of Aspirin in Gestation and Reproduction trial with available plasma samples, with relevant outcomes assessed among 584 women with pregnancies lasting at least 20 weeks' gestation. We measured platelet factor 4 in plasma samples obtained at the prepregnancy study visit (before randomization to low-dose aspirin or placebo), 12 weeks' gestation, and 28 weeks' gestation. The primary outcome was a composite of hypertensive disorders of pregnancy, placental abruption, and small-for-gestational-age infant. We estimated the relative risks (RRs) and 95% confidence intervals (CIs) for the association between platelet factor 4 and the composite and individual outcomes at each time point using log-binomial regression that was weighted to account for potential selection bias and adjusted for age, body mass index, education, income, and smoking. To evaluate the potential effect modification of aspirin, we stratified the analyses by aspirin treatment assignment.

RESULTS

During follow-up, 95 women experienced the composite adverse obstetrical outcome, with 57 cases of hypertensive disorders of pregnancy, 35 of small for gestational age, and 6 of placental abruption. Overall, prepregnancy platelet factor 4 was positively associated with the composite outcome (third tertile vs first tertile; relative risk, 2.36; 95% confidence interval, 1.38-4.03) and with hypertensive disorders of pregnancy (third tertile vs first tertile; relative risk, 2.14; 95% confidence interval, 1.08-4.23). In analyses stratified by treatment group, associations were stronger in the placebo group (third tertile vs first tertile; relative risk, 3.36; 95% confidence interval, 1.42-7.93) than in the aspirin group (third tertile vs first tertile; relative risk, 1.78; 95% confidence interval, 0.90-3.50).

CONCLUSION

High concentrations of platelet factor 4 before pregnancy are associated with increased risk of placenta-mediated adverse pregnancy outcomes, particularly for hypertensive disorders of pregnancy. Aspirin may mitigate the increased risk of these outcomes among women with higher plasma concentrations of preconception platelet factor 4, but low-dose aspirin nonresponders may require higher doses of aspirin or alternate therapies to achieve obstetrical risk reduction.

Late first trimester circulating microparticle proteins predict the risk of preeclampsia < 35 weeks and suggest phenotypic differences among affected cases

We hypothesize that first trimester circulating micro particle (CMP) proteins will define preeclampsia risk while identifying clusters of disease subtypes among cases. We performed a nested case–control analysis among women with and without preeclampsia. Cases diagnosed < 34 weeks’ gestation were matched to controls. Plasma CMPs were isolated via size exclusion chromatography and analyzed using global proteome profiling based on HRAM mass spectrometry. Logistic models then determined feature selection with best performing models determined by cross-validation. K-means clustering examined cases for phenotypic subtypes and biological pathway enrichment was examined. Our results indicated that the proteins distinguishing cases from controls were enriched in biological pathways involved in blood coagulation, hemostasis and tissue repair. A panel consisting of C1RL, GP1BA, VTNC, and ZA2G demonstrated the best distinguishing performance (AUC of 0.79). Among the cases of preeclampsia, two phenotypic sub clusters distinguished cases; one enriched for platelet degranulation and blood coagulation pathways and the other for complement and immune response-associated pathways (corrected p < 0.001). Significantly, the second of the two clusters demonstrated lower gestational age at delivery (p = 0.049), increased protein excretion (p = 0.01), more extreme laboratory derangement (p < 0.0001) and marginally increased diastolic pressure (p = 0.09). We conclude that CMP-associated proteins at 12 weeks’ gestation predict the overall risk of developing early preeclampsia and indicate distinct subtypes of pathophysiology and clinical morbidity.

Evaluation of global haemostatic assays and fibrin structure in patients with pre-eclampsia

INTRODUCTION

Haemostatic balance shifted towards hypercoagulability in normal pregnancy is even more pronounced in pre-eclampsia (P-EC). The aim of this study was to analyse haemostatic disturbances and fibrin clot properties in women with pre-eclampsia and to investigate their association with maternal and foetal outcomes.

METHODS

Forty-six pregnant women diagnosed with pre-eclampsia were included in the study, with blood sampling done on the morning following admission to hospital, as well as after delivery (mean duration 4.8 days). Two global haemostatic assays-endogenous thrombin potential (ETP) and assay of overall haemostatic potential (OHP)-were employed, including fibrin clot turbidity measurements and scanning electron microscopy (SEM) of representative samples.

RESULTS

Three thrombin generation parameters (ETP, t_lag and peak height) and OHP were significantly increased in pre-eclampsia compared with controls, whereas overall fibrinolytic potential (OFP-determined as a parameter of the OHP assay) had significantly lower values. Clot lysis time was significantly prolonged in patients with pre-eclampsia. In the pre-eclamptic group after delivery, we observed a significant elevation in the peak height and a reduction in the time to peak and OFP compared with values before delivery. Pre-eclamptic patients with renal complications had significantly higher values for ETP, peak height and D-dimer. Turbidity measurements and SEM revealed dense fibrin structure in patients with pre-eclampsia.

CONCLUSION

Patients with pre-eclampsia have enhanced coagulation and impaired fibrinolysis before, and even after, delivery. In particular, the presence of multi-organ dysfunction, such as renal dysfunction, may be associated with increased thrombin generation in pre-eclampsia.

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.

Platelet RNA modules point to coronary calcification in asymptomatic women with former preeclampsia

BACKGROUND AND AIMS

Women who develop preeclampsia during pregnancy are at a higher risk for developing cardiovascular disease. As platelets are affected by preeclampsia, we set out to identify whether platelets carry information in their transcriptome on cardiovascular risk in women with former preeclampsia.

METHODS

Platelets were isolated from asymptomatic women with previous preeclampsia, who underwent screening with coronary computed tomography angiography. Platelet RNA was isolated and used to construct gene networks using an unbiased approach. Platelet gene modules assembled from the network were related to risk factors and clinical traits of these women, including coronary artery calcium scores (CACS).

RESULTS

We found multiple gene modules which correlated with CACS (correlation coefficients: 0.44 to 0.59, p = 0.05 to 0.007). The genes from two clinically relevant modules were expressed at a higher level in the group with calcifications (p = 3.9 × 10^-10 and 0.02) and enriched for platelet-related gene-sets such as platelet activation. The first of these modules was also enriched (p_permutation = 0.0546) for genes mapped to known coronary artery disease susceptibility loci. Additional unbiased network analyses in platelet RNA of patients with overt cardiovascular disease underlined the importance of the identified modules for disease by high preservation. (p = 1.6 × 10^-9 to 1.7 × 10^-47).

CONCLUSIONS

We found platelet RNA modules that correlated with CACS in asymptomatic women with previous preeclampsia. Whether or not platelets directly contribute to this disease trajectory, or reflect the underlying plaque substrate remains to be determined, but enrichment for coronary artery disease susceptibility genes emphasizes the importance for the disease.

Hypertensive disorders of pregnancy are associated with an inflammatory state: evidence from hematological findings and cytokine levels

Background

Abnormalities of blood cell counts and of cytokine profiles in women with hypertensive disorders of pregnancy (HDP) have been reported in several studies. Although their cause-effect relationships to HDP are not yet clear, detecting and monitoring these alterations can be of use for prognosis and management of HDP. This study aimed to determine hematological, coagulation and cytokine profiles in hypertensive as compared to normotensive pregnancy and to identify correlations between these profiles.

Methods

This was a hospital-based comparative cross-sectional study conducted from September 2017 to February 2018. There were two groups: the comparison group consisted of 77 normotensive pregnant women attending the antenatal clinic of Muhimbili National Hospital (MNH); the index group consisted of 76 hypertensive pregnant women admitted to the maternity block of the same hospital. Hematological and cytokine parameters were compared between the hypertensive and the normotensive group. We analyzed the data using Student’s independent t-test when the data were normally distributed; and the Mann–Whitney U-test when the data were not normally distributed. Kruskal Wallis with Dunn’s multiple comparison tests was run for subgroup analysis and correlation studies were done using Spearman ranking.

Results

Hemoglobin levels were slightly but significantly lower, (P < 0.01) in women with HDP compared to normotensive (N) women; the same was true for platelet counts (P < 0.001). The red cell distribution width (RDW) was slightly but significantly higher in HDP than in N. Neutrophil counts and Interleukin 6 (IL-6) levels were significantly (P < 0.001) higher in HDP than in N; and within HDP IL-6 levels increased with increasing severity of HDP. A novel remarkable finding was that eosinophil counts, normal in N, were lower and lower with increasing severity of HDP, to the point that they were nearly absent in women with eclampsia.

Conclusion

There are significant changes in hematological, cytokine and coagulation parameters in pregnant women with hypertensive disorders compared to normotensive pregnant women. The picture that emerges is that of an inflammatory state associated with hypertensive disorders of pregnancy.

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.

The ability of thromboelastography parameters to predict severe pre-eclampsia when measured during early pregnancy

OBJECTIVE

To examine the predictive value of thromboelastography parameters during early pregnancy as potential markers of severe pre-eclampsia during late pregnancy.

METHODS

An observational retrospective case-control study was conducted among pregnant women who attended a single hospital in Shanghai, China, between July 1, 2016, and February 31, 2018. Data were obtained from medical records and a structured questionnaire completed by the participants. Thromboelastography parameters included time r; time k; α angle; maximum amplitude; clot lysis at 60 minutes; and coagulation index. Other risk factors for severe pre-eclampsia were also assessed.

RESULTS

The pre-eclampsia and control groups comprised 46 and 138 women, respectively. Women with a coagulation index below zero at 13-20 weeks experienced an increased risk of severe pre-eclampsia (odds ratio [OR] 31.72, 95% confidence interval [CI] 11.28-89.24; P<0.001). Other risk factors for severe pre-eclampsia were family history of hypertension (OR 3.79, 95% CI 1.21-11.48; P=0.017) and pre-pregnancy body mass index (OR 2.83, 95% CI 1.14-7.36; P=0.023).

CONCLUSION

Coagulation index determined by thromboelastography was an early marker for severe pre-eclampsia.

No effect of tranexamic acid on platelet function and thrombin generation (ETAPlaT) in postpartum haemorrhage: a randomised placebo-controlled trial

Background: Postpartum hemorrhage (PPH) is a leading cause of maternal mortality and morbidity. The WOMAN trial showed that tranexamic acid (TXA) reduces death due to bleeding in women with PPH. To determine whether TXA has pro-thrombotic effects in women with PPH, we measured endogenous thrombin potential (ETP), coagulation factors V, VIII, von Willebrand (vW), fibrinogen, D-Dimers and platelet function. Methods: We conducted a sub-study within the WOMAN trial, an international randomized, parallel-group, double blind, placebo-controlled trial. Women with primary PPH were randomly allocated to receive 1 gram of tranexamic acid or matching placebo. Baseline blood samples were collected just prior to the first dose and a follow up sample was collected 30±15 minutes afterwards. We compared before and after changes in coagulation parameters between treatment groups using repeated measurement ANOVA. Change in ETP was the primary outcome. We did an intention-to-treat analysis using ANCOVA with adjustment for baseline and the time interval between the blood samples. Findings: A total of 187 patients were randomized to receive TXA (n=93) or matching placebo (n=94). Six patients were excluded due to incomplete data. The reduction in ETP from baseline to follow up was 43.2 nM*min (95%CI, -16.6 to 103.1) in the TXA group and 4.6 nM*min (95%CI, -51.4 to 60.6) in the placebo group. The difference was not statistically significant (95%CI, -42.9 to 120). There were no significant effects of TXA treatment on any other parameters (ADPtest, TRAPtest, coagulation factors activity, fibrinogen levels, D-Dimer level). Conclusion: We found no evidence that tranexamic acid treatment for PPH has substantial pro-coagulant effects. However, larger studies are needed to confirm or refute more modest effects. Trial registration: ISRCTN76912190 (initially registered 10/12/2008, WOMAN-ETAPlat included on 28/10/2013) and NCT00872469 (initially registered 31/03/2009, WOMAN-ETAPlat included on 28/10/2013).

Increased circulating microparticles in women with preeclampsia

INTRODUCTION

Preeclampsia (PE) is associated with hypercoagulability, endothelial dysfunction and inflammation, which generate microparticles (MPs). Therefore, MPs may be important for PE.

METHODS

We established a verified MP measurement procedure to detect MPs in nonpregnant women (n = 25), healthy pregnant women (n = 29) and PE women (n = 73) and compared their MP levels.

RESULTS

Microparticles prepared from platelets (PMPs), endothelial cells (EMPs) and leucocytes (LMPs) were confirmed by transmission electron microscopy and were analysed by our established flow cytofluorimetric approach, which showed good specificity for determining the cell origin and level of MPs. The levels of total MPs (tMPs) and PMPs in the healthy pregnant group were significantly higher than those in the nonpregnant group (158.78 vs 93.00 and 45.04 vs 17.41, P = .004 and P = .007, respectively) but were not significantly different from those of the PE group. However, EMPs and LMPs were significantly higher in the PE group than in the healthy pregnant group (14.62 vs 11.48 and 8.94 vs 5.03, P = .015 and P < .001, respectively). Furthermore, the area under the receiver operating characteristic curves (AUC) for EMPs, LMPs and the combined sum of EMPs and LMPs were 0.661, 0.746 and 0.718, respectively (P < . 05); at their optimal cut-off values, the sensitivities were 50.68%, 87.67% and 46.58%, respectively, and the specificities were 80.77%, 58.33% and 95.65%, respectively.

CONCLUSION

Determining the MP level, especially that of EMPs and LMPs, by a specificity-verified method may reflect the endothelial dysfunction and inflammation involved in PE pathogenesis.

Elevated plasma TFPI activity causes attenuated TF-dependent thrombin generation in early onset preeclampsia

Early onset preeclampsia (EOP) is a pregnancy-specific proinflammatory disorder that is characterised by competing thrombotic and bleeding risks. It was the aim of this study to characterise thrombin generation, a major determinant of thrombotic and bleeding risk, in order to better understand the haemostatic balance in patients with EOP. Patients with EOP were recruited at the Rotunda Hospital, Dublin. Twenty-six cases of EOP were recruited over a 21-month period, out of 15,299 deliveries at the Rotunda. Blood samples were collected into sodium citrate plus corn trypsin inhibitor anticoagulated vacutainers, platelet-poor plasma was prepared, and calibrated automated thrombography was used to assess thrombin generation. Results were compared to age and sex-matched non-pregnant controls (n=13) and age-and gestation-matched pregnant controls (n=20). The rate and extent of thrombin generation triggered by low-dose tissue factor (TF) was significantly reduced in patients with EOP compared to pregnant controls, most significantly in cases of severe EOP. EOP patients displayed a trend towards an increased response to endogenous activated protein C and thrombomodulin relative to pregnant controls. Plasma tissue factor pathway inhibitor (TFPI) activity was increased in EOP patients. Inhibition of TFPI abolished the attenuation of thrombin generation stimulated by low-dose TF. In conclusion, patients with EOP are characterised by an attenuated coagulation response characterised by reduced thrombin generation stimulated by low-dose TF and elevated plasma TFPI activity. These changes in coagulation may modulate thrombotic risk and bleeding risk in patients with EOP.

The pattern and magnitude of "in vivo thrombin generation" differ in women with preeclampsia and in those with SGA fetuses without preeclampsia

OBJECTIVE

We aimed to determine the differences in the pattern and magnitude of thrombin generation between patients with preeclampsia (PE) and those with a small-for-gestational-age (SGA) fetus.

METHODS

This cross-sectional study included women in the following groups: (1) normal pregnancy (NP) (n = 49); (2) PE (n = 56); and (3) SGA (n = 28). Maternal plasma thrombin generation (TGA) was measured, calculating: (a) lag time (LT); (b) velocity index (VI); (c) peak thrombin concentration (PTC); (d) time-to-peak thrombin concentration (TPTC); and (e) endogenous thrombin potential (ETP).

RESULTS

(1) The median TPTC, VI, and ETP differed among the groups (p = .001, p = .006, p < .0001); 2) the median ETP was higher in the PE than in the NP (p < .0001) and SGA (p = .02) groups; 3) patients with SGA had a shorter median TPTC and a higher median VI than the NP (p = .002, p = .012) and PE (p < .0001, p = .006) groups.

CONCLUSIONS

(1) Patients with PE had higher in vivo thrombin generation than women with NP and those with an SGA fetus; (2) the difference in TGA patterns between PE and SGA suggests that the latter group had faster TGA, while patients with PE had a longer reaction, generating more thrombin. This observation is important for the identification of a subset of patients who might benefit from low molecular-weight heparin.

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.

Statistical analysis plan for the WOMAN-ETAPlaT study: Effect of tranexamic acid on platelet function and thrombin generation

Background. Postpartum haemorrhage (PPH) is a potentially life-threatening complication for women, and the leading cause of maternal mortality. Tranexamic acid (TXA) is an antifibrinolytic used worldwide to treat uterine haemorrhage and to reduce blood loss in general surgery. TXA may have effects on thrombin generation, platelet function and coagulation factors as a result of its inhibition on the plasmin. Methods. WOMAN ETAPlaT is a sub-study of the World Maternal Antifibrinolitic trial (WOMAN trial). All adult women clinically diagnosed with PPH after a vaginal delivery or caesarean section, are eligible for inclusion in the study. Blood samples will be collected at the baseline and 30 minutes after the first dose of study treatment is given. Platelet function will be evaluated in whole blood immediately after sampling with Multiplate® tests (ADPtest and TRAPtest). Thrombin generation, fibrinogen, D-dimer, and coagulation factors vW, V and VIII will be analysed using platelet poor plasma. Results. Recruitment to WOMAN ETAPlaT started on 04 November 2013 and closed on 13 January 2015, during this time  188 patients were recruited. The final participant follow-up was completed on 04 March 2015. This article introduces the statistical analysis plan for the study, without reference to unblinded data.   Conclusion. The data from this study will provide evidence for the effect of TXA on thrombin generation, platelet function and coagulation factors in women with PPH. Trial registration: ClinicalTrials.gov Identifier: NCT00872469; ISRCTN76912190

Statistical analysis plan for the WOMAN-ETAPlaT study: Effect of tranexamic acid on platelet function and thrombin generation

Background. Postpartum haemorrhage (PPH) is a potentially life-threatening complication for women, and the leading cause of maternal mortality. Tranexamic acid (TXA) is an antifibrinolytic used worldwide to treat uterine haemorrhage and to reduce blood loss in general surgery. TXA may have effects on thrombin generation, platelet function and coagulation factors as a result of its inhibition on the plasmin.

Methods. WOMAN ETAPlaT is a sub-study of the World Maternal Antifibrinolitic trial (WOMAN trial). All adult women clinically diagnosed with PPH after a vaginal delivery or caesarean section, are eligible for inclusion in the study. Blood samples will be collected at the baseline and 30 minutes after the first dose of study treatment is given. Platelet function will be evaluated in whole blood immediately after sampling with Multiplate® tests (ADPtest and TRAPtest). Thrombin generation, fibrinogen, D-dimer, and coagulation factors vW, V and VIII will be analysed using platelet poor plasma.

Results. Recruitment to WOMAN ETAPlaT started on 04 November 2013 and closed on 13 January 2015, during this time  188 patients were recruited. The final participant follow-up was completed on 04 March 2015. This article introduces the statistical analysis plan for the study, without reference to unblinded data.  

Conclusion. The data from this study will provide evidence for the effect of TXA on thrombin generation, platelet function and coagulation factors in women with PPH.

Trial registration: ClinicalTrials.gov Identifier: NCT00872469; ISRCTN76912190

Maternal extracellular vesicles and platelets promote preeclampsia via inflammasome activation in trophoblasts

Preeclampsia (PE) is a placenta-induced inflammatory disease associated with maternal and fetal morbidity and mortality. The mechanisms underlying PE remain enigmatic and delivery of the placenta is the only known remedy. PE is associated with coagulation and platelet activation and increased extracellular vesicle (EV) formation. However, thrombotic occlusion of the placental vascular bed is rarely observed and the mechanistic relevance of EV and platelet activation remains unknown. Here we show that EVs induce a thromboinflammatory response specifically in the placenta. Following EV injection, activated platelets accumulate particularly within the placental vascular bed. EVs cause adenosine triphosphate (ATP) release from platelets and inflammasome activation within trophoblast cells through purinergic signaling. Inflammasome activation in trophoblast cells triggers a PE-like phenotype, characterized by pregnancy failure, elevated blood pressure, increased plasma soluble fms-like tyrosine kinase 1, and renal dysfunction. Intriguingly, genetic inhibition of inflammasome activation specifically in the placenta, pharmacological inhibition of inflammasome or purinergic signaling, or genetic inhibition of maternal platelet activation abolishes the PE-like phenotype. Inflammasome activation in trophoblast cells of women with preeclampsia corroborates the translational relevance of these findings. These results strongly suggest that EVs cause placental sterile inflammation and PE through activation of maternal platelets and purinergic inflammasome activation in trophoblast cells, uncovering a novel thromboinflammatory mechanism at the maternal-embryonic interface.

Update of syncytiotrophoblast derived extracellular vesicles in normal pregnancy and preeclampsia

The release of extracellular vesicles (EV) by the syncytiotrophoblast (STB) may be an important mechanism by which the placenta signals to the mother. STB derived EV (STBEV) are comprised predominantly of exosomes (50-150nm) and microvesicles (100-1000nm) that contain bioactive mediators such as proteins, nucleic acids and lipids. They, along with larger syncytial nuclear aggregates are released by the STB into the maternal circulation throughout gestation in normal pregnancy where they appear to have an immunoregulatory role, inhibiting T cell and NK cell responses. In pre-eclampsia (PE) STBEV are released in significantly increased numbers and have pro-inflammatory, anti-angiogenic and procoagulant activity, implicating them in the maternal systemic inflammation, endothelial dysfunction and activation of the clotting system which typifies the disorder. Research has focused on understanding the biological significance of STBEV by measuring their size and repertoire of molecules carried and how they differ in normal pregnancy and PE, using techniques such as Nanoparticle Tracking Analysis, flow cytometry and mass spectrometry. We have also found alterations in STBEV surface glycans associated with PE. The goal is to better understand the role STBEV play in normal pregnancy and PE and whether they are potential biomarkers of placental pathology and therapeutic targets in PE.

Plasma markers of endothelial dysfunction in patients with hypertensive disorders of pregnancy: a pilot study in a South Indian population

OBJECTIVES

To assess the plasma markers of endothelial dysfunction: VonWillebrand factor (vWF), Platelet derived microparticles (PMPs), and Endothelin-1 (ET-1) in various types of hypertensive disorders of pregnancy and correlate with the pregnancy outcome.

METHODS

Plasma levels of vWF, PMPs and ET-1 were analyzed by ELISA kits in gestational hypertension (GH), late onset preeclampsia (LOPE), early onset preeclampsia (EOPE), eclampsia (E) and control pregnant women (CPW) during third trimester. The gestational age at the time of delivery (GA) and birthweight (BW) of the baby also were measured.

RESULTS

The GA and the BW of the baby were found to be significantly lower in EOPE and eclampsia compared to CPW, GH and LOPE. The circulating levels of markers of endothelial dysfunction: vWF, PMPs and ET-1 were significantly higher in EOPE and Eclampsia compared to CPW, GH. Also a negative correlation was observed between vWF levels with pregnancy outcome; GA and BW.

CONCLUSIONS

A generalized endothelial dysfunction and poor birth outcomes were observed in hypertensive disorders of pregnancy. There is a spectrum of biochemical derangements related to endothelial dysfunction in GH, EOPE, LOPE and E in that order.

Elevated venous thromboembolism risk in preeclampsia: molecular mechanisms and clinical impact

Venous thromboembolism (VTE) remains a leading cause of maternal death and morbidity in the developed world. Strategies for prevention of VTE in pregnancy have been the subject of recent guidelines and consensus statements. These guidelines recommend thrombosis prevention in women who have risk factors associated with an elevated VTE risk. Preeclampsia is characterized by maternal hypertension and proteinuria developing after 20 weeks gestation, complicating up to 7% of pregnancies and is associated with a massive annual morbidity and mortality burden. Women with preeclampsia have been shown to be at increased risk of VTE with studies to date suggesting that this risk may be up to 5-fold greater than the risk of pregnancy-associated VTE in the general population. Despite the fact that preeclampsia is so common and potentially devastating, our understanding of its pathogenesis and potential therapeutic strategies remain poor. In addition, the mechanisms underlying the prothrombotic phenotype in preeclampsia are also poorly characterized although a number of potential mechanisms have been postulated. Derangements of platelet and endothelial activation and impairment of endogenous anti-coagulant pathways have been reported and may contribute to the observed VTE risk. Recently, evidence for the role of neutrophil extracellular traps (NETs) and cell-free DNA in the pathogenesis of VTE has emerged and some evidence exists to suggest that this may be of relevance in preeclampsia. Future studies aimed at understanding the diagnostic and potential therapeutic relevance of this procoagulant state are likely to be of enormous clinical benefit for pregnant women affected with this potentially devastating condition.

Early severe preeclampsia with marked platelet dysfunction in association with essential thrombocytemia: case report and discussion

Essential thrombocytemia--a classic myeloproliferative neoplasm characterized by persistent thrombocytosis--may associate both thrombotic and hemorrhagic events, as well as platelet dysfunction. Of all myeloproliferative neoplasms, essential thrombocytemia is more likely to be associated with pregnancy, because of a higher comparative incidence in younger patients. This association significantly increases the risk of pregnancy loss and of various pregnancy complications. We present a case of early severe preeclampsia with a critical and unusual evolution and life-threatening complications.

Helicobacter pylori, Chlamydiae pneumoniae and trachomatis as probable etiological agents of preeclampsia

OBJECTIVES

The aim of this study was to evaluate the evidence for Helicobacter pylori, Chlamydiae pneumoniae and trachomatis to act as a probable etiology for preeclampsia (PE), together with estimating the prevalence of such infections in pregnant women with PE.

METHODS

We performed a prospective study in Mansoura University Hospitals, Egypt, for detecting H. pylori infection by estimating H. pylori IgG and IgM, in addition to detection of Chlamydiae infections by PCR in 90 pregnant women with PE and 90 normotensive pregnant women of the same age and body mass index who were studied as control.

RESULTS

The prevalence of H. pylori infection in preeclamptic pregnant women was 54.4% with a statistically significant association to PE. The prevalence of C. pneumonia was 27.8% whereas that of C. trachomatis was 4.44%. The infected preeclamptic cases showed high levels of leucocytes besides elevated C-reactive protein concentrations.

CONCLUSION

Helicobacter pylori was found to act as a cofactor in the development of PE. Occurrence of C. trachomatis was low in pregnant women in our community; however, it showed that it may act as a cofactor in PE, whereas C. pneumoniae was attributed to have no role in PE pathogenesis until supported by further studies.