Human and mouse platelet transcriptomes and proteomes for phenotyping 3474 genes with hemostatic and platelet traits.

The hemostatic process relies on platelet and coagulation activation, with additional roles of red blood cells and the vessel wall. By systematic screening of databases for gene-linked information on hemostasis, we collected phenotypic profiles of 3474 orthologous human and mouse genes regarding bleeding, arterial thrombosis, thrombophilia, platelet traits, coagulation, and erythrocytes. Comparisons showed that defects in 252 mouse genes led to increased bleeding combined with platelet dysfunction or thrombocytopenia, in addition to 150 human orthologs that are registered for familial bleeding disorders, based on panel sequencing.

Extended Modelling of Molecular Calcium Signalling in Platelets by Combined Recurrent Neural Network and Partial Least Squares Analyses.

Platelets play critical roles in haemostasis and thrombosis. The platelet activation process is driven by agonist-induced rises in cytosolic [Ca], where the patterns of Ca responses are still incompletely understood. In this study, we developed a number of techniques to model the [Ca] curves of platelets from a single blood donor.

Deleting ACC1 in platelets alters phospholipidome and reduces platelet activation and thrombosis in mice.

This study uncovers the pivotal role of acetyl-CoA carboxylase 1 (ACC1) in regulating platelet lipid composition, bioenergetics, activation, and thrombus formation, as demonstrated using a targeted GPIbα-Cre+/- mouse model. By comparing platelet-specific ACC1 knockout mice (pKO; GPIbα-Cre+/- x ACC1flx/flx) with both GPIbα-Cre+/- and ACC1flx/flx control groups, we showed that ACC1 deficiency profoundly reshaped the platelet phospholipidome. Specifically, ACC1 deletion led to decreased levels of arachidonic acid-containing phosphatidylethanolamine plasmalogens, thereby limiting thromboxane A2 synthesis, dense granule secretion, and platelet activation upon agonist stimulation.

Elevated levels of (active) von Willebrand factor during anticoagulation are associated with early recurrence of venous thromboembolism.

Background: Venous thromboembolism (VTE) can recur shortly after stopping anticoagulation, highlighting the need for reliable biomarkers to identify high-risk patients during treatment.

Objectives: To determine whether platelet and endothelial markers predict VTE recurrence.

Methods: We used data and samples from the randomized controlled VISTA trial (2011-2015), which included patients with unprovoked VTE who were treated with vitamin K antagonists for 6 months.

Length of ischemia duration is associated with fibrin film coverage of acute myocardial infarction thrombi.

Background: Coronary artery disease plaque rupture leads to occlusive thrombosis, causing acute myocardial infarction requiring immediate life-saving treatment. The blood clot is supported by a mesh of fibrin fibers that are generated through the polymerization of fibrin. We recently showed that fibrin also produces a film on the surface of blood clots.

Primary hemostasis in children with cirrhosis prior to liver transplantation: key roles of liver disease severity, von Willebrand factor, and platelet count.

Background: Thrombocytopenia is common in pediatric patients with cirrhosis, but the extent and relevance of functional platelet defects remain unclear.

Objectives: This proof-of-principle study aimed to characterize platelet properties in cirrhotic children before living-donor liver transplantation using state-of-the-art platelet-based assays, hypothesizing that primary hemostasis in this group is well preserved.

Methods: From January 2022 to July 2023, pediatric cirrhotic patients were prospectively enrolled 1 day before liver transplantation.

Enhancing hemostasis potency in hemophilia with a small interfering ribonucleic acid targeting protein S.

Background: One hemophilia treatment concept focuses on rebalancing coagulation and anticoagulation to restore normal blood clotting. Targeting the coagulation regulator, protein S (PS), in hemophilia shows promise to increase the generation of thrombin, a critical enzyme in the clotting process.

Objectives: This study aimed to: (1) assess whether inhibiting PS increases thrombin generation (TG) in plasma from individuals with hemophilia A (HA) and B (HB); and (2) develop a hepatocyte-targeted PS small interfering RNA (siRNA) therapy using N-acetylgalactosamine conjugation to restore hemostasis in hemophilia without increasing thromboembolic risks.

Role of inflammation and haemostasis on aetiology and prognosis in young patients with ischaemic stroke: study protocol of the Observational Dutch Young Symptomatic StrokE study-EXTended (ODYSSEY-nEXT) - a multicentre prospective cohort study.

Introduction: The cause of ischaemic stroke at a young age remains unknown in 30% of cases, highlighting the need to identify hidden causes and risk factors in young patients. Transient and chronic risk factors may interact with the inflammatory and haemostatic systems, potentially driving key mechanisms in the pathogenesis. The 'Observational Dutch Young StrokE study-Extended' (ODYSSEY-nEXT) aims to enhance our understanding of these complex interactions through detailed phenotyping of the immune and haemostatic system and explore their relationship with long-term prognosis.

Age- and sex-dependency of thrombin generation parameters in the general Italian population: the Moli-sani study.

Background: Recent developments have made the thrombin generation (TG) test accessible to the clinical laboratory. Therefore, the clinical interpretation of TG parameters has become of increasing interest, and reference values are required. Age and sex have been shown to affect TG parameters, but no consensus has been reached on the subject.

Patients with cirrhosis have a disbalance between coagulation and fibrinolysis resulting in a prothrombotic phenotype.

Background: Patients with cirrhosis develop multiple hemostatic alterations. Although fibrinolysis is also affected by liver disease, studies have produced conflicting results, highlighting the need for a reliable fibrinolysis assay. Assessing the kinetics of plasmin generation (PG) is a new method to study the fibrinolytic state of cirrhosis patients.

Toward standardization and a concerted vision for platelet proteomics research: communication from the SSC of the ISTH.

Over the past 3 decades, omics technologies have revolutionized our understanding of platelet molecular content and organization, enabling the systematic analyses of platelet physiology. Among these approaches, proteomics has been especially significant in discovering as well as validating molecular mechanisms of platelet function in health and disease. However, several conceptual and practical challenges continue to limit the full utility of platelet proteomics tools and data.

A rapid whole-blood adenosine triphosphate secretion test can be used to exclude platelet-dense granule deficiency.

Background: Delta storage pool disease (δ-SPD) is a rare platelet function disorder (PFD) characterized by a deficiency of dense granules or defective granule secretion, leading to bleeding diathesis. Diagnostics of δ-SPD are difficult and lack standardization, leading to underestimation of its prevalence. Current diagnostic methods are based on granule content assays or lumi-aggregometry, which have limited availability.

High Prevalence of Acquired Platelet Secretion Defects in Multiple Myeloma.

Thrombocytopenia at admission predicts mortality in multiple myeloma (MM) and might link to disease progression. Although thrombocytopenia is known to be associated with MM, a possible thrombopathy is clinically less known. We conducted a case-control study comparing platelet responses of MM patients to controls via flow cytometry, integrin αIIbβ3 activation and P-selectin exposure, and a bioluminescent assay, ATP release.

Platelet activation and signaling in thrombus formation.

In thrombosis and hemostasis, the formation of a platelet-fibrin thrombus or clot is a highly controlled process that varies, depending on the pathological context. Major signaling pathways in platelets are well established. However, studies with genetically modified mice have identified the contribution of hundreds of additional platelet-expressed proteins in arterial thrombus formation and bleeding.

No correlation between thrombin generation and emicizumab levels: implications for monitoring emicizumab therapy.

Background: Emicizumab, a bispecific antibody that mimics factor (F)VIII, has significantly improved hemophilia A management. Although emicizumab levels can be measured, tools for estimating the hemostatic efficacy of emicizumab are lacking. Thrombin generation (TG) assays can distinguish bleeding phenotypes in persons with hemophilia A on FVIII prophylaxis and may also be used during emicizumab therapy.

Middle-throughput LC-MS-based Platelet Proteomics with Minute Sample Amounts Using Semiautomated Positive Pressure FASP in 384-Well Format.

Comprehensive characterization of platelets requires various functional assays and analytical techniques, including omics disciplines, each demanding a separate aliquot of the given sample. Consequently, sample material for each assay is often highly limited, necessitating the downscaling of methods to work with just a few micrograms of platelet protein.Here, we present a novel sample preparation platform for proteomics analysis using only 3 μg of purified platelet protein, corresponding to 2 × 10 platelets, which can be obtained from approximately 2 to 8 μL of blood from a healthy individual (1.

Fibrin film on clots is increased by hematocrit but reduced by inflammation: implications for platelets and fibrinolysis.

Background: Blood clot formation, triggered by vascular injury, is crucial for hemostasis and thrombosis. Blood clots are composed mainly of fibrin fibers, platelets, and red blood cells (RBCs). Recent studies show that clot surfaces also develop a fibrin film, which provides protection against wound infection and retains components such as RBCs within the clot.

Interpreting high levels of unfolded Von Willebrand Factor in patients with the antiphospholipid syndrome.

Introduction: Unfolded Von Willebrand Factor (VWF) is increased in thrombotic pathologies such as myocardial infarction. Unfolded VWF mediates the binding of platelets without the need for collagen. β-glycoprotein I (β-GPI) is a natural inhibitor of the platelet-VWF interaction.

Thrombomodulin is a stronger indicator of combined oral contraceptives-induced activated protein C pathway resistance in the thrombin generation test than activated protein C.

Background: The mechanism by which combined oral contraceptives (COCs) lead to hypercoagulation is not fully understood, although activated protein C (APC) pathway resistance has been implicated. APC and thrombomodulin (TM) tend to be considered as interchangeable reagents, even though their biological action in coagulation is different. However, it remains unclear which reagent is better suited for the detection of APC pathway resistance.

Low thrombin inactivation capacity is associated with an increased risk of recurrent ischemic events after ischemic stroke at a young age.

Background: Patients with ischemic stroke at a young age (18-50 years) have an increased long-term risk of recurrent ischemic events. Hypercoagulability may contribute to this high risk.

Objectives: To investigate the associations between in vivo and ex vivo hemostatic parameters and recurrent ischemic events after an ischemic stroke or transient ischemic attack (TIA) at a young age.

Impaired whole blood thrombin generation is associated with procedure-related bleeding in acutely decompensated cirrhosis.

Background & Aims: The clinical utility of thrombomodulin-modified thrombin generation (TM-TG) in cirrhosis is uncertain. We conducted a prospective study to evaluate the prognostic value of TM-TG in cirrhosis.

Methods: Patients were recruited during outpatient clinics (compensated and stable decompensated cirrhosis) or if admitted to our inpatient service (acutely decompensated cirrhosis).

Functionally distinct anticoagulant mechanisms of endothelial cells.

Antithrombin and tissue factor pathway inhibitor (TFPI) provide different anticoagulant mechanisms. Having established a potent anticoagulant role of cultured human umbilical vein endothelial cells in vessel-on-a-chip microfluidic models, we now investigated how these cells modulated thrombin generation under stasis through antithrombin and TFPI pathways. We observed that endothelial monolayers in 96 well-plates strongly delayed and suppressed the thrombin generation process induced by tissue factor, regardless of the presence of whole blood, platelet-rich plasma or platelet-free plasma.

An update on laboratory detection and interpretation of antiphospholipid antibodies for diagnosis of antiphospholipid syndrome: guidance from the ISTH-SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies.

Antiphospholipid syndrome (APS) diagnosis is dependent on the accurate detection and interpretation of antiphospholipid antibodies (aPL). Lupus anticoagulant (LA), anticardiolipin antibodies (aCL), and anti-beta2 glycoprotein I antibodies (aβ2GPI) remain the cornerstone of the laboratory part of APS diagnosis. In the 2023 American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) APS classification criteria, the type of laboratory parameters remain essentially unchanged compared with the updated Sapporo classification criteria, and aCL and aβ2GPI measurement are still restricted to enzyme-linked immunosorbent assays (ELISAs) with moderate and high titer aPL thresholds defined as 40 and 80 Units, respectively, and a cutoff calculated by the 99th percentile has been abandoned.