Of von Willebrand factor and platelets

Hemin regulates platelet clearance in hemolytic disease by binding to GPIbα

Hemolysis is associated with thrombosis and vascular dysfunction, which are the pathological components of many diseases. Hemolytic products, including hemoglobin and hemin, activate platelets (PLT). Despite its activation, the effect of hemolysis on platelet clearance remains unclear, It is critical to maintain a normal platelet count and ensure that circulating platelets are functionally viable. In this study, we used hemin, a degradation product of hemoglobin, as a potent agonist to treat platelets and simulate changes in vivo in mice. Hemin treatment induced activation and morphological changes in platelets, including an increase in intracellular Ca2+ levels, phosphatidylserine (PS) exposure, and cytoskeletal rearrangement. Fewer hemin-treated platelets were cleared by macrophages in the liver after transfusion than untreated platelets. Hemin bound to glycoprotein Ibα (GPIbα), the surface receptor in hemin-induced platelet activation and aggregation. Furthermore, hemin decreased GPIbα desialylation, as evidenced by reduced Ricinus communis agglutinin I (RCA- I) binding, which likely extended the lifetime of such platelets in vivo. These data provided new insight into the mechanisms of GPIbα-mediated platelet activation and clearance in hemolytic disease.

Bernard-Soulier syndrome caused by two novel heterozygous GP1BA gene mutations: a case report and literature review

BACKGROUND

Bernard-Soulier syndrome (BSS) is a rare inherited macrothrombocytopenia, usually autosomal recessive, which is characterized by prolonged bleeding, thrombocytopenia, and abnormally large platelets.

METHODS

For more than 6 years, we misdiagnosed a patient with BSS without an obvious bleeding tendency as having idiopathic thrombocytopenia purpura (ITP), prior to obtaining a genetic analysis. On admission, routine hematology showed a platelet count of 30 × 109/L and mean platelet volume (MPV) of 14.0 fL.

RESULTS

Whole-exome sequencing revealed two likely pathogenic heterozygous mutations (c.95_101del and c.1012del) in GP1BA. Flow cytometry analysis of platelet membrane glycoproteins indicated that the expression of GP1b was 0.28% of the normal level. Platelet aggregation tests indicated that platelet aggregation was inhibited by ristocetin- (1.7%), ADP- (14.5%), and arachidonic acid- (5.6%) induced platelet aggregation. A literature review identified reports on 53 mutations in the GP1BA gene in 253 patients, 29 mutations in the GP1BB gene in 90 patients, and 32 mutations in the GP9 gene in 114 patients.

CONCLUSION

This case report describes two novel gene mutation sites that have not been reported previously, enriching understanding of the GP1BA mutation spectrum.

Targeting Rap1b signaling cascades with CDNF: Mitigating platelet activation, plasma oxylipins and reperfusion injury in stroke

Cerebral reperfusion injury in stroke, stemming from interconnected thrombotic and inflammatory signatures, often involves platelet activation, aggregation and its interaction with various immune cells, contributing to microvascular dysfunction. However, the regulatory mechanisms behind this platelet activation and the resulting inflammation are not well understood, complicating the development of effective stroke therapies. Utilizing animal models and platelets from hemorrhagic stroke patients, our research demonstrates that human cerebral dopamine neurotrophic factor (CDNF) acts as an endogenous antagonist, mitigating platelet aggregation and associated neuroinflammation. CDNF moderates mitochondrial membrane potential, reactive oxygen species production, and intracellular calcium in activated platelets by interfering with GTP binding to Rap1b, thereby reducing Rap1b activation and downregulating the Rap1b-MAPK-PLA2 signaling pathway, which decreases release of the pro-inflammatory mediator thromboxane A2. In addition, CDNF reduces the inflammatory response in BV2 microglial cells co-cultured with activated platelets. Consistent with ex vivo findings, subcutaneous administration of CDNF in a rat model of ischemic stroke significantly reduces platelet activation, aggregation, lipid mediator production, infarct volume, and neurological deficits. In summary, our study highlights CDNF as a promising therapeutic target for mitigating platelet-induced inflammation and enhancing recovery in stroke. Harnessing the CDNF pathway may offer a novel therapeutic strategy for stroke intervention.

Low shear-induced fibrillar fibronectin: comparative analyses of morphologies and cellular effects on bovine aortic endothelial cell adhesion and proliferation

Wall shear stress (WSS) is a critical factor in vascular biology, and both high and low WSS are implicated in atherosclerosis. Fibronectin (FN) is a key extracellular matrix protein that plays an important role in cell activities. Under high shear stress, plasma FN undergoes fibrillogenesis; however, its behavior under low shear stress remains unclear. This study aimed to investigate the formation ofin vitrocell-free fibrillar FN (FFN) under low shear rate conditions and its effect on bovine aortic endothelial cell behavior. FN (500µg ml-1) was perfused through slide chambers at three flow rates (0.16 ml h-1, 0.25 ml h-1, and 0.48 ml h-1), corresponding to low shear rates of 0.35 s-1, 0.55 s-1, and 1.05 s-1, respectively, for 4 h at room temperature. The formed FN matrices were observed using fluorescence microscopy and scanning electron microscopy. Under low shear rates, distinct FN matrix structures were observed. FFN0.48 formed immense fibrils with smooth surfaces, FFN0.25 formed a matrix with a rough surface, and FFN16 exhibited nodular structures. FFN0.25 supported cell activities to a greater extent than native FN and other FFN surfaces. Our study suggests that abnormally low shear conditions impact FN structure and function and enhance the understanding of FN fibrillogenesis in vascular biology, particularly in atherosclerosis.

Activated platelets retain and protect most of their factor XIII-A cargo from proteolytic activation and degradation

ABSTRACT

Platelet factor XIII-A (FXIII-A) is a major cytoplasmic protein (∼3% of total), representing ∼50% of total circulating FXIII. However, mobilization of FXIII-A during platelet activation is not well defined. To determine mechanisms mediating the retention vs release of platelet FXIII-A, platelets from healthy humans and mice (F13a1-/-, Fga-/-, Plg-/-, Stim1fl/flPf4-Cre, and respective controls) were stimulated with thrombin, convulxin plus thrombin, or calcium ionophore (A23187), in the absence or presence of inhibitors of transglutaminase activity, messenger RNA (mRNA) translation, microtubule rearrangement, calpain, and Rho GTPase. Platelet releasates and pellets were separated by (ultra)centrifugation. FXIII-A was detected by immunoblotting and immunofluorescence microscopy. Even after strong dual agonist (convulxin plus thrombin) stimulation of human platelets, >80% platelet FXIII-A remained associated with the platelet pellet. In contrast, essentially all tissue factor pathway inhibitor, another cytoplasmic protein in platelets, was released to the supernatant. Pellet-associated FXIII-A was not due to de novo synthesis via platelet F13A1 mRNA. The proportion of platelet FXIII-A retained by vs released from activated platelets was partly dependent on STIM1 signaling, microtubule rearrangement, calpain, and RhoA activation but did not depend on the presence of fibrinogen or plasminogen. Immunofluorescence microscopy confirmed the presence of considerable FXIII-A within the activated platelets. Although released FXIII-A was cleaved to FXIII-A∗ and could be degraded by plasmin, platelet-associated FXIII-A remained uncleaved. Retention of substantial platelet-derived FXIII-A by activated platelets and its reduced susceptibility to thrombin- and plasmin-mediated proteolysis suggest platelet FXIII-A is a protected pool with biological role(s) that differs from plasma FXIII.

Unlocking the intricacies: Exploring the complex interplay between platelets and ovarian cancer

Ovarian cancer, an aggressive malignancy of the female reproductive tract, is frequently linked to an elevated risk of thrombotic events. This association is manifested by a pronounced rise in platelet counts and activation levels. Current research firmly supports the pivotal role of platelets in the oncogenic processes of ovarian cancer, influencing tumor cell proliferation and metastasis. Platelets influence these processes through direct interactions with tumor cells or by secreting cytokines and growth factors that enhance tumor growth, angiogenesis, and metastasis. This review aims to thoroughly dissect the interactions between platelets and ovarian cancer cells, emphasizing their combined role in tumor progression and associated thrombotic events. Additionally, it summarizes therapeutic strategies targeting platelet-cancer interface which show significant promise. Such approaches could not only be effective in managing the primary ovarian tumor but also play a pivotal role in preventing metastasis and attenuating thrombotic complications associated with ovarian cancer.

Bioengineered heparin: Advances in production technology

Heparin, a highly sulfated glycosaminoglycan, is considered an indispensable anticoagulant with diverse therapeutic applications and has been a mainstay in medical practice for nearly a century. Its potential extends beyond anticoagulation, showing promise in treating inflammation, cancer, and infectious diseases such as COVID-19. However, its current sourcing from animal tissues poses challenges due to variable structures and adulterations, impacting treatment efficacy and safety. Recent advancements in metabolic engineering and synthetic biology offer alternatives through bioengineered heparin production, albeit with challenges such as controlling molecular weight and sulfonation patterns. This review offers comprehensive insight into recent advancements, encompassing: (i) the metabolic engineering strategies in prokaryotic systems for heparin production; (ii) strides made in the development of bioengineered heparin; and (iii) groundbreaking approaches driving production enhancements in eukaryotic systems. Additionally, it explores the potential of recombinant Chinese hamster ovary cells in heparin synthesis, discussing recent progress, challenges, and future prospects, thereby opening up new avenues in biomedical research.

Platelets in Thrombosis and Atherosclerosis: A Double-Edged Sword

This review focuses on the dual role of platelets in atherosclerosis and thrombosis, exploring their involvement in inflammation, angiogenesis, and plaque formation, as well as their hemostatic and prothrombotic functions. Beyond their thrombotic functions, platelets engage in complex interactions with diverse cell types, influencing disease resolution and progression. The contribution of platelet degranulation helps in the formation of atheromatous plaque, whereas the reciprocal interaction with monocytes adds complexity. Alterations in platelet membrane receptors and signaling cascades contribute to advanced atherosclerosis, culminating in atherothrombotic events. Understanding these multifaceted roles of platelets will lead to the development of targeted antiplatelet strategies for effective cardiovascular disease prevention and treatment. Understanding platelet functions in atherosclerosis and atherothrombosis at different stages of disease will be critical for designing targeted treatments and medications to prevent or cure the disease Through this understanding, platelets can be targeted at specific times in the atherosclerosis process, possibly preventing the development of atherothrombosis.

Efficacy and safety of novel freeze-dried plasma products in a porcine combat casualty model

BACKGROUND

Hemorrhagic shock is well documented as a leading cause of preventable fatalities among military casualties. During military operations plasma can be transfused while waiting for whole blood. This study was conducted to assess the safety and efficacy of two new freeze-dried plasma formulations in a porcine model of traumatic hemorrhagic shock.

STUDY DESIGN AND METHODS

In the face of species-specific transfusion, transfusible blood products were derived from porcine sources. The efficacy of three lyophilized plasma (LP) formulations was evaluated: lyophilized plasma (LP), concentrated lyophilized plasma (CLP), and platelet-rich concentrated lyophilized plasma (PCLP). Pigs were subjected to multi-trauma and hemorrhagic shock. Ninety minutes post-shock induction, the animals were treated with one of the three lyophilized products. Monitoring included systolic blood pressure and cardiac output. Point-of-care and laboratory diagnostic tests were used to assess renal function, real-time hemostasis (ROTEM), and coagulation. Histological examinations of kidney, lung, and muscle tissues were conducted 4 h after shock induction.

RESULTS

CLP and PCLP significantly improved systolic blood pressure and cardiac output and positively influenced base excess, creatinine, various ROTEM, and coagulation markers compared with standard LP without histologic modification. No adverse effect was associated with the transfusion of any of the plasma products throughout the experimental procedures.

CONCLUSION

Both CLP and PCLP exhibit promising therapeutic potential for managing hemorrhagic shock in scenario where whole blood supplies are limited. However, the distinct physiological and coagulation characteristics of the swine model necessitate further investigation using humanized preclinical models to fully understand their clinical applicability and constraints.

Weibel-Palade bodies: function and role in thrombotic thrombocytopenic purpura and in diarrhea phase of STEC-hemolytic uremic syndrome

Vascular endothelial cells are equipped with numerous specialized granules called Weibel-Palade bodies (WPBs). They contain a cocktail of proteins that can be rapidly secreted (3-5 min) into the vascular lumen after an appropriate stimulus such as thrombin. These proteins are ready without synthesis. Von Willebrand factor (VWF) and P-selectin are the main constituents of WPBs. Upon stimulation, release of ultralarge VWF multimers occurs and assembles into VWF strings on the apical side of endothelium. The VWF A1 domain becomes exposed in a shear-dependent manner recruiting and activating platelets. VWF is able to recruit leukocytes via direct leukocyte binding or via the activated platelets promoting NETosis. Ultralarge VWF strings are ultimately cleaved into smaller pieces by the protease ADAMTS-13 preventing excessive platelet adhesion. Under carefully performed flowing conditions and adequate dose of Shiga toxins, the toxin induces the release of ultralarge VWF multimers from cultured endothelial cells. This basic information allows insight into the pathogenesis of thrombotic thrombocytopenic purpura (TTP) and of STEC-HUS in the diarrhea phase. In TTP, ADAMTS-13 activity is deficient and systemic aggregation of platelets will occur after a second trigger. In STEC-HUS, stimulated release of WPB components in the diarrhea phase of the disease can be presumed to be the first hit in the damage of Gb3 positive endothelial cells.

Cryptic Extensibility in von Willebrand Factor Revealed by Molecular Nanodissection

Von Willebrand factor (VWF) is a multimer with a variable number of protomers, each of which is a head-to-head dimer of two multi-domain monomers. VWF responds to shear through the unfolding and extension of distinct domains, thereby mediating platelet adhesion and aggregation to the injured blood vessel wall. VWF's C1-6 segment uncoils and then the A2 domain unfolds and extends in a hierarchical and sequential manner. However, it is unclear whether there is any reservoir of further extensibility. Here, we explored the presence of cryptic extensibility in VWF by nanodissecting individual, pre-stretched multimers with atomic force microscopy (AFM). The AFM cantilever tip was pressed into the surface and moved in a direction perpendicular to the VWF axis. It was possible to pull out protein loops from VWF, which resulted in a mean contour length gain of 217 nm. In some cases, the loop became cleaved, and a gap was present along the contour. Frequently, small nodules appeared in the loops, indicating that parts of the nanodissected VWF segment remained folded. After analyzing the nodal structure, we conclude that the cryptic extensibility lies within the C1-6 and A1-3 regions. Cryptic extensibility may play a role in maintaining VWF's functionality in extreme shear conditions.

Advances in Platelet-Dysfunction Diagnostic Technologies

The crucial role of platelets in hemostasis and their broad implications under various physiological conditions underscore the importance of accurate platelet-function testing. Platelets are key to clotting blood and healing wounds. Therefore, accurate diagnosis and management of platelet disorders are vital for patient care. This review outlines the significant advancements in platelet-function testing technologies, focusing on their working principles and the shift from traditional diagnostic methods to more innovative approaches. These improvements have deepened our understanding of platelet-related disorders and ushered in personalized treatment options. Despite challenges such as interpretation of complex data and the costs of new technologies, the potential for artificial-intelligence integration and the creation of wearable monitoring devices offers exciting future possibilities. This review underscores how these technological advances have enhanced the landscape of precision medicine and provided better diagnostic and treatment options for platelet-function disorders.

Electrochemical Monitoring in Anticoagulation Therapy

The process of blood coagulation, wherein circulating blood transforms into a clot in response to an internal or external injury, is a critical physiological mechanism. Monitoring this coagulation process is vital to ensure that blood clotting neither occurs too rapidly nor too slowly. Anticoagulants, a category of medications designed to prevent and treat blood clots, require meticulous monitoring to optimise dosage, enhance clinical outcomes, and minimise adverse effects. This review article delves into the various stages of blood coagulation, explores commonly used anticoagulants and their targets within the coagulation enzyme system, and emphasises the electrochemical methods employed in anticoagulant testing. Electrochemical sensors for anticoagulant monitoring are categorised into two types. The first type focuses on assays measuring thrombin activity via electrochemical techniques. The second type involves modified electrode surfaces that either directly measure the redox behaviours of anticoagulants or monitor the responses of standard redox probes in the presence of these drugs. This review comprehensively lists different electrode compositions and their detection and quantification limits. Additionally, it discusses the potential of employing a universal calibration plot to replace individual drug-specific calibrations. The presented insights are anticipated to significantly contribute to the sensor community's efforts in this field.

A lone spike in blood glucose can enhance the thrombo-inflammatory response in cortical venules

How transient hyperglycemia contributes to cerebro-vascular disease has been a challenge to study under controlled physiological conditions. We use amplified, ultrashort laser-pulses to physically disrupt brain-venule endothelium at targeted locations. This vessel disruption is performed in conjunction with transient hyperglycemia from a single injection of metabolically active D-glucose into healthy mice. The observed real-time responses to laser-induced disruption include rapid serum extravasation, platelet aggregation, and neutrophil recruitment. Thrombo-inflammation is pharmacologically ameliorated by a platelet inhibitor, by a scavenger of reactive oxygen species, and by a nitric oxide donor. As a control, vessel thrombo-inflammation is significantly reduced in mice injected with metabolically inert L-glucose. Venules in mice with diabetes show a similar response to laser-induced disruption and damage is reduced by restoration of normo-glycemia. Our approach provides a controlled method to probe synergies between transient metabolic and physical vascular perturbations and can reveal new aspects of brain pathophysiology.

Impact of Additional Administration of von Willebrand Factor Concentrates to Thrombocyte Transfusion in Perioperative Bleeding in Cardiac Surgery

Background

Von Willebrand factor (vWF) is an important part of blood coagulation since it binds platelets to each other and to endothelial cells. In traumatic and surgical haemorrhage, both blood cells and plasmatic factors are consumed, leading to consumption coagulopathy and fluid resuscitation. This often results in large amounts of crystalloids and blood products being infused. Additional administration of vWF complex and platelets might mitigate this problem. We hypothesize that administration of vWF concentrate additionally to platelet concentrates reduces blood loss and the amount of blood products (platelets, red blood cells [RBC], fresh frozen plasma [FFP]) administered.

Methods

We conducted a monocentric 6-year retrospective data analysis of cardiac surgery patients. Included were all patients receiving platelet concentrates within 48 h postoperatively. Patients who additionally received vWF concentrates were allocated to the intervention group and all others to the control group. Groups were compared in mixed regression models correcting for known confounders, based on nearest neighbour propensity score matching. Primary endpoints were loss of blood (day one and two) and amount of needed blood products on day one and two (platelets, RBC, FFP). Secondary endpoints were intensive care unit (ICU) and in-hospital length of stay, ICU and in-hospital mortality, and absolute difference of platelet counts before and after treatment.

Results

Of 497 patients analysed, 168 (34%) received vWF concentrates. 121 patients in both groups were considered for nearest neighbour matching. Patients receiving additional vWF were more likely to receive more blood products (RBC, FFP, platelets) in the first 24 h after surgery and had around 200 mL more blood loss at the same time.

Conclusion

In this retrospective analysis, no benefit in additional administration of vWF to platelet concentrates on perioperative blood loss, transfusion requirement (platelets, RBC, FFP), length of stay, and mortality could be found. These findings should be verified in a prospective randomized controlled clinical trial (www.clinicaltrials.gov identifier NCT04555785).

Platelets and Thrombotic Antiphospholipid Syndrome

Antiphospholipid antibody syndrome (APS) is an autoimmune disorder characterised by thrombosis and the presence of antiphospholipid antibodies (aPL): lupus anticoagulant and/or IgG/IgM anti-β2-glycoprotein I and anticardiolipin antibodies. APS carries significant morbidity for a relatively young patient population from recurrent thrombosis in any vascular bed (arterial, venous, or microvascular), often despite current standard of care, which is anticoagulation with vitamin K antagonists (VKA). Platelets have established roles in thrombosis at any site, and platelet hyperreactivity is clearly demonstrated in the pathophysiology of APS. Together with excess thrombin generation, platelet activation and aggregation are the common end result of all the pathophysiological pathways leading to thrombosis in APS. However, antiplatelet therapies play little role in APS, reserved as a possible option of low dose aspirin in addition to VKA in arterial or refractory thrombosis. This review outlines the current evidence and mechanisms for excessive platelet activation in APS, how it plays a central role in APS-related thrombosis, what evidence for antiplatelets is available in clinical outcomes studies, and potential future avenues to define how to target platelet hyperreactivity better with minimal impact on haemostasis.

Assessment of α9β1 ıntegrın as a new dıagnostıc and therapeutıc target ın Behcet's dısease

This study aimed to investigate the roles of α9β1 integrin and its ligands in Behçet's disease (BD) by examining serum levels and gene expressions. 15 healthy controls and 30 BD patients (14 active and 16 inactive) were included in the study. Serum levels of ITGA9, ITGB1, TNC, OPN, VCAM-1, VEGF, TSP1, TGM2, Emilin-1, and vWF, were measured by ELISA. Gene expressions of α9β1 (ITGA9 and ITGB1) and its ligands (TNC and SPP1) were evaluated by RT-PCR. Laboratory findings (CRP, ESR, HGB, WBC, RBC, neutrophil, lymphocyte, PLT, RDW, MPV, PCT, and HLA-B51) were obtained from the electronic database. Active BD patients had higher serum levels of α9β1 integrin and its ligands than inactive patients and healthy controls. No significant difference was observed between healthy controls and inactive patients. Gene expressions of ITGB1 and SPP1 were increased in both patient groups compared to healthy controls. ITGA9 and TNC gene expression levels were lower in the active group than in the inactive group. No noticeable differences were found in ITGB1 and SPP1 gene expressions between the patient groups. BD patients exhibited elevated CRP, ESR, WBC, neutrophil, PLT, and PCT levels, while HGB, RBC, and RDW values were lower than healthy controls. Active patients had higher CRP, ESR, WBC, neutrophil, and PLT levels. Significant positive correlations were found between CRP, ESR, WBC, neutrophil, PLT, PCT and serum levels of α9β1 integrin and its ligands. Increased release of α9β1 integrin and its ligands is associated with BD, suggesting their potential as markers for disease severity.

The interplay between adsorption and aggregation of von Willebrand factor chains in shear flows

Von Willebrand factor (VWF) is a giant extracellular glycoprotein that carries out a key adhesive function during primary hemostasis. Upon vascular injury and triggered by the shear of flowing blood, VWF establishes specific interactions with several molecular partners in order to anchor platelets to collagen on the exposed subendothelial surface. VWF also interacts with itself to form aggregates that, adsorbed on the surface, provide more anchor sites for the platelets. However, the interplay between elongation and subsequent exposure of cryptic binding sites, self-association, and adsorption on the surface remained unclear for VWF. In particular, the role of shear flow in these three processes is not well understood. In this study, we address these questions by using Brownian dynamics simulations at a coarse-grained level of resolution. We considered a system consisting of multiple VWF-like self-interacting chains that also interact with a surface under a shear flow. By a systematic analysis, we reveal that chain-chain and chain-surface interactions coexist nontrivially to modulate the spontaneous adsorption of VWF and the posterior immobilization of secondary tethered chains. Accordingly, these interactions tune VWF's extension and its propensity to form shear-assisted functional adsorbed aggregates. Our data highlight the collective behavior VWF self-interacting chains have when bound to the surface, distinct from that of isolated or flowing chains. Furthermore, we show that the extension and the exposure to solvent have a similar dependence on shear flow, at a VWF-monomer level of resolution. Overall, our results highlight the complex interplay that exists between adsorption, cohesion, and shear forces and their relevance for the adhesive hemostatic function of VWF.

Current Biomarkers for Carotid Artery Stenosis: A Comprehensive Review of the Literature

Carotid artery stenosis (CAS), an atherosclerotic disease of the carotid artery, is one of the leading causes of transient ischemic attacks (TIA) and cerebrovascular attacks (CVA). The atherogenic process of CAS affects a wide range of physiological processes, such as inflammation, endothelial cell function, smooth muscle cell migration and many more. The current gold-standard test for CAS is Doppler ultrasound; however, there is yet to be determined a strong, clinically validated biomarker in the blood that can diagnose patients with CAS and/or predict adverse outcomes in such patients. In this comprehensive literature review, we evaluated all of the current research on plasma and serum proteins that are current contenders for biomarkers for CAS. In this literature review, 36 proteins found as potential biomarkers for CAS were categorized in to the following nine categories based on protein function: (1) Inflammation and Immunity, (2) Lipid Metabolism, (3) Haemostasis, (4) Cardiovascular Markers, (5) Markers of Kidney Function, (6) Bone Health, (7) Cellular Structure, (8) Growth Factors, and (9) Hormones. This literature review is the most up-to-date and current comprehensive review of research on biomarkers of CAS, and the only review that demonstrated the several pathways that contribute to the initiation and progression of the disease. With this review, future studies can determine if any new markers, or a panel of the proteins explored in this study, may be contenders as diagnostic or prognostic markers for CAS.

The effects of coagulation factors on the risk of endometriosis: a Mendelian randomization study

BACKGROUND

Endometriosis is recognized as a complex gynecological disorder that can cause severe pain and infertility, affecting 6-10% of all reproductive-aged women. Endometriosis is a condition in which endometrial tissue, which normally lines the inside of the uterus, deposits in other tissues. The etiology and pathogenesis of endometriosis remain ambiguous. Despite debates, it is generally agreed that endometriosis is a chronic inflammatory disease, and patients with endometriosis appear to be in a hypercoagulable state. The coagulation system plays important roles in hemostasis and inflammatory responses. Therefore, the purpose of this study is to use publicly available GWAS summary statistics to examine the causal relationship between coagulation factors and the risk of endometriosis.

METHODS

To investigate the causal relationship between coagulation factors and the risk of endometriosis, a two-sample Mendelian randomization (MR) analytic framework was used. A series of quality control procedures were followed in order to select eligible instrumental variables that were strongly associated with the exposures (vWF, ADAMTS13, aPTT, FVIII, FXI, FVII, FX, ETP, PAI-1, protein C, and plasmin). Two independent cohorts of European ancestry with endometriosis GWAS summary statistics were used: UK Biobank (4354 cases and 217,500 controls) and FinnGen (8288 cases and 68,969 controls). We conducted MR analyses separately in the UK Biobank and FinnGen, followed by a meta-analysis. The Cochran's Q test, MR-Egger intercept test, and leave-one-out sensitivity analyses were used to assess the heterogeneities, horizontal pleiotropy, and stabilities of SNPs in endometriosis.

RESULTS

Our two-sample MR analysis of 11 coagulation factors in the UK Biobank suggested a reliable causal effect of genetically predicted plasma ADAMTS13 level on decreased endometriosis risk. A negative causal effect of ADAMTS13 and a positive causal effect of vWF on endometriosis were observed in the FinnGen. In the meta-analysis, the causal associations remained significant with a strong effect size. The MR analyses also identified potential causal effects of ADAMTS13 and vWF on different sub-phenotypes of endometrioses.

CONCLUSIONS

Our MR analysis based on GWAS data from large-scale population studies demonstrated the causal associations between ADAMTS13/vWF and the risk of endometriosis. These findings suggest that these coagulation factors are involved in the development of endometriosis and may represent potential therapeutic targets for the management of this complex disease.

Impact of the von Willebrand factor-ADAMTS-13 axis on the risk of future venous thromboembolism

BACKGROUND

von Willebrand factor (VWF) and its cleaving protease, ADAMTS-13, form a pivotal axis that regulates hemostasis. However, the role of the VWF-ADAMTS-13 axis in the risk of future venous thromboembolism (VTE) is unknown.

OBJECTIVES

To investigate whether plasma ADAMTS-13 levels and an imbalance with VWF levels, assessed as the VWF/ADAMTS-13 ratio, are associated with the risk of future VTE.

PATIENTS/METHODS

A population-based nested case-control study, comprising 383 incident VTE cases and 780 age- and sex-matched controls, was derived from the Tromsø study cohort (1994-2007). Antigen levels of ADAMTS-13 and VWF were measured in plasma samples obtained at cohort baseline. Odds ratios (ORs) with 95% CIs were estimated according to quartile cutoffs of ADAMTS-13 and VWF/ADAMTS-13 ratio determined in controls.

RESULTS

In age- and sex-adjusted analysis, ADAMTS-13 levels were inversely associated with the VTE risk, with an OR of 1.40 (95% CI, 0.99-1.99) for the lowest vs highest quartiles. The VWF/ADAMTS-13 ratio was linearly associated with the VTE risk (P for trend = .001), with an OR of 1.70 (95% CI, 1.19-2.43) for the highest vs lowest quartiles, and the association was particularly pronounced for unprovoked VTE (OR, 2.81; 95% CI, 1.65-4.81). The ORs were only slightly attenuated after additional adjustments for body mass index and C-reactive protein.

CONCLUSIONS

Lowered ADAMTS-13 levels and an imbalance between ADAMTS-13 and VWF levels, reflected by an increased VWF/ADAMTS-13 ratio, were associated with an increased risk of future VTE. Our findings suggest that the VWF-ADAMTS-13 axis is involved in the pathogenesis of VTE.

Development of a dual hybrid AAV vector for endothelial-targeted expression of von Willebrand factor

Von Willebrand disease (VWD), the most common inherited bleeding disorder in humans, is caused by quantitative or qualitative defects in von Willebrand factor (VWF). VWD represents a potential target for gene therapy applications, as a single treatment could potentially result in a long-term correction of the disease. In recent years, several liver-directed gene therapy approaches have been exploited for VWD, but their efficacy was generally limited by the large size of the VWF transgene and the reduced hemostatic activity of the protein produced from hepatocytes. In this context, we aimed at developing a gene therapy strategy for gene delivery into endothelial cells, the natural site of biosynthesis of VWF. We optimized an endothelial-specific dual hybrid AAV vector, in which the large VWF cDNA was put under the control of an endothelial promoter and correctly reconstituted upon cell transduction by a combination of trans-splicing and homologous recombination mechanisms. In addition, we modified the AAV vector capsid by introducing an endothelial-targeting peptide to improve the efficiency for endothelial-directed gene transfer. This vector platform allowed the reconstitution of full-length VWF transgene both in vitro in human umbilical vein endothelial cells and in vivo in VWD mice, resulting in long-term expression of VWF.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Enhancement of the haemostatic effect of platelets in the presence of high normal concentrations of von Willebrand factor for critically ill patients needing platelet transfusion-a protocol for the will-plate randomised controlled trial

INTRODUCTION

von Willebrand Factor (vWF) is a key protein mediating platelet adhesion on the surface of damaged endothelia. To the best of our knowledge, no trial exists that investigated the effect of platelet transfusion in combination with the administration of balanced vWF in severe blood loss, despite being widely used in clinical practice. The Basel Will-Plate study will investigate the impact of the timely administration of balanced vWF (1:1 vWF and FVIII) in addition to platelet transfusion on the need for blood and coagulation factor transfusion in patients admitted to the intensive care unit (ICU) who suffer from severe bleeding. The study hypothesis is based on the assumption that adding balanced vWF to platelets will reduce the overall need for transfusion of blood products compared to the transfusion of platelets alone.

METHODS AND ANALYSIS

The Will-Plate study is an investigator-initiated, single-centre, double-blinded randomised controlled clinical trial in 120 critically ill patients needing platelet transfusion. The primary outcome measure will be the number of fresh frozen plasma (FFP) and red blood cell (RBC) transfusions according to groups. Secondary outcome measures include the number of platelet concentrates transfused within the first 48 h after treatment of study medication, quantity of blood loss in the first 48 h after treatment with the study medication, length of stay in ICU and hospital, number of revision surgeries for haemorrhage control, ICU mortality, hospital mortality, 30-day mortality and 1-year mortality. Patients will be followed after 30 days and 1 year for activities of daily living and mortality assessment. The sample size was calculated to detect a 50% reduction in the number of blood products subsequently transfused within 2 days in patients with Wilate® compared to placebo.

ETHICS AND DISSEMINATION

This study has been approved by the Ethics Committee of Northwestern and Central Switzerland and will be conducted in compliance with the protocol, the current version of the Declaration of Helsinki, the ICH-GCP or ISO EN 14155 (as far as applicable) and all national legal and regulatory requirements. The study results will be presented at international conferences and published in a peer-reviewed journal.

TRIALS REGISTRATION

ClinicalTrials.gov NCT04555785.

PROTOCOL VERSION

Clinical Study Protocol Version 2, 01.11.2020. Registered on Sept. 21, 2020.

Myofibroblast specific targeting approaches to improve fibrosis treatment

Fibrosis has been shown to develop in individuals with underlying health conditions, especially chronic inflammatory diseases. Fibrosis is often diagnosed in various organs, including the liver, lungs, kidneys, heart, and skin, and has been described as excessive accumulation of extracellular matrix that can affect specific organs in the body or systemically throughout the body. Fibrosis as a chronic condition can result in organ failure and result in death of the individual. Understanding and identification of specific biomarkers associated with fibrosis has emerging potential in the development of diagnosis and targeting treatment modalities. Therefore, in this review, we will discuss multiple signaling pathways such as TGF-β, collagen, angiotensin, and cadherin and outline the chemical nature of the different signaling pathways involved in fibrogenesis as well as the mechanisms. Although it has been well established that TGF-β is the main catalyst initiating and driving multiple pathways for fibrosis, targeting TGF-β can be challenging as this molecule regulates essential functions throughout the body that help to keep the body in homeostasis. We also discuss collagen, angiotensin, and cadherins and their role in fibrosis. We comprehensively discuss the various delivery systems used to target collagen, angiotensin, and cadherins to manage fibrosis. Nevertheless, understanding the steps by which this molecule drives fibrosis development can aid in the development of specific targets of its cascading mechanism. Throughout the review, we will demonstrate the mechanism of fibrosis targeting to improve targeting delivery and therapy.

Structure and dynamics of the von Willebrand Factor C6 domain

Von Willebrand disease (VWD) is a bleeding disorder with different levels of severity. VWD-associated mutations are located in the von Willebrand factor (VWF) gene, coding for the large multidomain plasma protein VWF with essential roles in hemostasis and thrombosis. On the one hand, a variety of mutations in the C-domains of VWF are associated with increased bleeding upon vascular injury. On the other hand, VWF gain-of-function (GOF) mutations in the C4 domain have recently been identified, which induce an increased risk of myocardial infarction. Mechanistic insights into how these mutations affect the molecular behavior of VWF are scarce and holistic approaches are challenging due to the multidomain and multimeric character of this large protein. Here, we determine the structure and dynamics of the C6 domain and the single nucleotide polymorphism (SNP) variant G2705R in C6 by combining nuclear magnetic resonance spectroscopy, molecular dynamics simulations and aggregometry. Our findings indicate that this mutation mostly destabilizes VWF by leading to a more pronounced hinging between both subdomains of C6. Hemostatic parameters of variant G2705R are close to normal under static conditions, but the missense mutation results in a gain-of-function under flow conditions, due to decreased VWF stem stability. Together with the fact that two C4 variants also exhibit GOF characteristics, our data underline the importance of the VWF stem region in VWF's hemostatic activity and the risk of mutation-associated prothrombotic properties in VWF C-domain variants due to altered stem dynamics.

Polyphosphate Activates von Willebrand Factor Interaction with Glycoprotein Ib in the Absence of Factor VIII In Vitro

Polyphosphate (polyP), a phosphate polymer released by activated platelets, may modulate various stages of hemostasis by binding to blood proteins. In this context, we previously reported that polyP binds to the von Willebrand factor (VWF). One of the most significant functions of VWF is to bind to and protect the blood circulating Factor VIII (FVIII). Therefore, here, we study the role of polyP in the VWF-FVIII complex in vitro and suggest its biological significance. Surface plasmon resonance and electrophoretic mobility assays indicated that polyP binds dynamically to VWF only in the absence of FVIII. Using the VWF Ristocetin Cofactor assay, the most accepted method for studying VWF in platelet adhesion, we found that polyP activates this role of VWF only at low levels of FVIII, such as in plasmas with chemically depleted FVIII and plasmas from severe hemophilia A patients. Moreover, we demonstrated that FVIII competes with polyP in the activation of VWF. Finally, polyP also increases the binding of VWF to platelets in samples from patients with type 2 and type 3 von Willebrand disease. We propose that polyP may be used in designing new therapies to activate VWF when FVIII cannot be used.

von Willebrand factor unfolding mediates platelet deposition in a model of high-shear thrombosis

Thrombosis under high-shear conditions is mediated by the mechanosensitive blood glycoprotein von Willebrand factor (vWF). vWF unfolds in response to strong flow gradients and facilitates rapid recruitment of platelets in flowing blood. While the thrombogenic effect of vWF is well recognized, its conformational response in complex flows has largely been omitted from numerical models of thrombosis. We recently presented a continuum model for the unfolding of vWF, where we represented vWF transport and its flow-induced conformational change using convection-diffusion-reaction equations. Here, we incorporate the vWF component into our multi-constituent model of thrombosis, where the local concentration of stretched vWF amplifies the deposition rate of free-flowing platelets and reduces the shear cleaning of deposited platelets. We validate the model using three benchmarks: in vitro model of atherothrombosis, a stagnation point flow, and the PFA-100, a clinical blood test commonly used for screening for von Willebrand disease (vWD). The simulations reproduced the key aspects of vWF-mediated thrombosis observed in these experiments, such as the thrombus location, thrombus growth dynamics, and the effect of blocking platelet-vWF interactions. The PFA-100 simulations closely matched the reported occlusion times for normal blood and several hemostatic deficiencies, namely, thrombocytopenia, vWD type 1, and vWD type 3. Overall, this multi-constituent model of thrombosis enables macro-scale 3D simulations of thrombus formation in complex geometries over a wide range of shear rates and accounts for qualitative and quantitative hemostatic deficiencies in patient blood.

N-Stearoylethanolamine Inhibits Integrin-Mediated Activation, Aggregation, and Adhesion of Human Platelets

N-stearoylethanolamine (NSE), a lipid mediator that belongs to the N-acylethanolamine (NAE) family, has anti-inflammatory, antioxidant, and membranoprotective actions. In contrast to other NAEs, NSE does not interact with cannabinoid receptors. The exact mechanism of its action remains unclear. The aim of this study is to evaluate the action of NSE on activation, aggregation, and adhesion of platelets that were chosen as a model of cellular response. Aggregation of platelets was measured to analyze the action of NSE (10^-6-10^-10 M) on platelet reactivity. Changes in granularity and shape of resting platelets and platelets stimulated with ADP in the presence of NSE were monitored by flow cytometry, and platelet deganulation was monitored by spectrofluorimetry. In vivo studies were performed using obese insulin-resistant rats. Binding of fibrinogen to the GPIIb/IIIa receptor was estimated using indirect ELISA and a scanning electron microscopy (SEM). It was found that NSE inhibits the activation and aggregation of human platelets. Our results suggest that NSE may decrease the activation and subsequent aggregation of platelets induced by ristocetin, epinephrine, and low doses of ADP. NSE also reduced the binding of fibrinogen to GPIIb/IIIa on activated platelets. These effects could be explained by the inhibition of platelet activation mediated by integrin receptors: the GPIb-IX-V complex for ristocetin-induced activation and GPIIb/IIIa when epinephrine and low doses of ADP were applied. The anti-platelet effect of NSE complements its anti-inflammatory effect and allows us to prioritize studies of NSE as a potent anti-thrombotic agent. SIGNIFICANCE STATEMENT: N-stearoylethanolamine (NSE) was shown to possess inhibitory action on platelet activation, adhesion, and aggregation. The mechanism of inhibition possibly involves integrin receptors. This finding complements the known anti-inflammatory effects of NSE.

Von Willebrand Factor Multimer Analysis by Low Resolution SDS-Agarose Gel Electrophoresis

Von Willebrand factor (VWF) is a complex glycoprotein found in plasma, composed of disulfide-bond-linked multimers with apparent molecular weights between 500 kDa and 20,000 kDa. After release of VWF from storage granules, it is cleaved in flowing blood by the specific metalloproteinase ADAMTS13, resulting in a highly characteristic cleavage pattern and structure. As the structure of VWF multimers determines diagnosis of von Willebrand disease, which has different sub-types with different multimer- and cleavage patterns, VWF analysis is performed using low-resolution horizontal SDS-agarose gel electrophoresis. However, almost every laboratory uses a different protocol, and all experimental details are rarely, if at all, described. Therefore, the results from similar methods may be substantially different. Here, we present a detailed description of a validated VWF multimer method that we have developed. It has been successfully used for over more than 20 years in quality control of recombinant and plasma-derived VWF drug products, and in preclinical and clinical studies with VWF drug candidates. As most of the published methods, it enables visualization of VWF multimers separated by electrophoresis by immunostaining with a polyclonal anti-human VWF antibody followed by a secondary antibody coupled to alkaline phosphatase. VWF appears as a series of regularly spaced bands on the low and middle molecular weight range of the gel, with an unresolved zone in the high molecular weight (HMW) range, where ultra-large multimers are found. An example is shown below. This low-resolution agarose gel electrophoresis allows the determination of the number of VWF multimers with high reproducibility. Graphical abstract: Example of electrophoretic analysis of multimer structure of four batches of a recombinant VWF drug substance.

Platelet-inspired nanomedicine in hemostasis thrombosis and thromboinflammation

Platelets are anucleate cell-fragments derived predominantly from megakaryocytes in the bone marrow and released in the blood circulation, with a normal count of 150 000-40 000 per μl and a lifespan of approximately 10 days in humans. A primary role of platelets is to aid in vascular injury site-specific clot formation to stanch bleeding, termed hemostasis. Platelets render hemostasis by a complex concert of mechanisms involving platelet adhesion, activation and aggregation, coagulation amplification, and clot retraction. Additionally, platelet secretome can influence coagulation kinetics and clot morphology. Therefore, platelet defects and dysfunctions result in bleeding complications. Current treatment for such complications involve prophylactic or emergency transfusion of platelets. However, platelet transfusion logistics constantly suffer from limited donor availability, challenges in portability and storage, high bacterial contamination risks, and very short shelf life (~5 days). To address these issues, an exciting area of research is focusing on the development of microparticle- and nanoparticle-based platelet surrogate technologies that can mimic various hemostatic mechanisms of platelets. On the other hand, aberrant occurrence of the platelet mechanisms lead to the pathological manifestation of thrombosis and thromboinflammation. The treatments for this are focused on inhibiting the mechanisms or resolving the formed clots. Here, platelet-inspired technologies can provide unique platforms for disease-targeted drug delivery to achieve high therapeutic efficacy while avoiding systemic side-effects. This review will provide brief mechanistic insight into the role of platelets in hemostasis, thrombosis and thromboinflammation, and present the current state-of-art in the design of platelet-inspired nanomedicine for applications in these areas.

Lower-leg injury and knee arthroscopy have distinct effects on coagulation

Unlike knee arthroscopy, lower-leg injury is associated with increased plasma levels of factor VIII, von Willebrand factor, and D-dimer.

In both situations, coagulation is affected differently, which suggests that there are different pathways toward venous thromboembolism.

It is unknown how lower-leg injury and knee arthroscopy, both associated with venous thromboembolism (VTE), affect coagulation. To study the effect of (1) lower-leg trauma and (2) knee arthroscopy on coagulation, plasma samples of the Prevention of Thrombosis following CAST immobilization (POT-CAST, #NCT01542762) and Prevention of Thrombosis following Knee Arthroscopy (POT-KAST, #NCT01542723) trials were used, which were collected shortly after lower-leg trauma and before/after (<4 hours) knee arthroscopy. For aim 1, 1204 lower-leg injury patients were compared with preoperative samples of 1001 controls. Mean differences/ratios (if ln-retransformed because of skewedness) were adjusted for sex, age, body mass index, comorbidity, malignancy, and oral contraceptives using linear regression. For aim 2, perioperative mean changes of 715 arthroscopy patients were calculated. Plasma levels of fibrinogen, factor (F)VIII, FIX, FXI, von Willebrand Factor (VWF), and D-dimer were measured in all individuals. Parameters of underlying mechanisms (tissue factor, interleukin-6 [IL-6], myeloperoxidase DNA, cell-free DNA) were measured in random subsets. In lower-leg injury patients, coagulation parameter levels increased, especially FVIII, VWF, and D-dimer, that is, adjusted mean differences: FVIII 26.8% (95% confidence interval [CI], 23.7-29.9), FIX 13.8% (95% CI, 11.9-15.6), FXI 5.1% (95% CI, 3.3-7.0), VWF 29.8% (95% CI, 26.0-33.6), fibrinogen 32.5 mg/dL (95% CI, 25.8-39.2), and D-dimer (mean ratio) 3.3 (95% CI, 3.1-3.6). Remaining parameters were unchanged, except for increased IL-6 levels. After arthroscopy, all parameters decreased. Lower-leg trauma is associated with increased procoagulant factor levels in contrast to knee arthroscopy. This suggests that, in both situations, different pathways are involved in development of VTE.

Identification of von Willebrand factor D4 domain mutations in patients of Afro-Caribbean descent: In vitro characterization

Background

Von Willebrand disease was diagnosed in two Afro-Caribbean patients and sequencing of the VWF gene (VWF) revealed the presence of multiple variants located throughout the gene, including variants located in the D4 domain of VWF: p.(Pro2145Thrfs*5) in one patient and p.(Cys2216Phefs*9) in the other patient. Interestingly, D4 variants have not been studied often.

Objectives

Our goal was to characterize how the D4 variants p.(Pro2145Thrfs*5) and p.(Cys2216Phefs*9) influenced VWF biosynthesis/secretion and functions using in vitro assays.

Methods

Recombinant VWF (rVWF), mutant or wild-type, was produced via transient transfection of the human embryonic kidney cell line 293T. The use of different tags for the wild-type and the mutant allele allowed us to distinguish between the two forms when measuring VWF antigen in medium and cell lysates. Binding of rVWF to its ligands, collagen, factor VIII, ADAMTS13, and platelet receptors was also investigated.

Results

Homozygous expression of the p.(Cys2216Phefs*9)-rVWF mutation resulted in an almost complete intracellular retention of the protein. Heterozygous expression led to secretion of almost exclusively wild-type-rVWF, logically capable of normal interaction with the different ligands. In contrast, the p.(Pro2145Thrfs*5)-rVWF exhibited reduced binding to type III collagen and αIIbβ3 integrin compared to wild-type-rVWF.

Conclusions

We report two mutations of the D4 domains that induced combined qualitative and quantitative defects.

Variations in the Gene Expression Profile in Atherosclerotic Patients with Non-Fatal ACS. A Preliminary Study

The pathophysiology of atherosclerosis and acute coronary syndrome (ACS) is related to interactions between immune cells, endothelium, and blood platelets. An increasing number of reports confirm the link between excessive immune activation and cellular cross-talk with ACS incidence. Our genetic and proteomic analysis was performed on strictly selected atherosclerotic patients with non-fatal ACS without typical risk factors and healthy donors. Results showed changes in the gene expression levels of the various inflammatory factors derived from the peripheral blood cells that drive the over-activation of the immune system. The enhanced activation of the immune system may lead to the overexpression of the pro-inflammatory mediators, which causes self-perpetuating machinery of processes associated with thrombosis. In our preliminary study, we confirmed an altered expression of genes associated with the inflammation and overall interaction of the vascular microenvironment. Furthermore, 5 of 92 analyzed genes, CCL2, CCR2, CSF2, GZMB, and ICOS, were expressed only in patients with ACS. In conclusion, the augmented expression of the pro-inflammatory genes from the peripheral blood cells may be a crucial genetic factor leading to the occurrence of acute inflammation and thus be significant in ACS pathogenesis.

Mechanisms Underlying Dichotomous Procoagulant COAT Platelet Generation-A Conceptual Review Summarizing Current Knowledge

Procoagulant platelets are a subtype of activated platelets that sustains thrombin generation in order to consolidate the clot and stop bleeding. This aspect of platelet activation is gaining more and more recognition and interest. In fact, next to aggregating platelets, procoagulant platelets are key regulators of thrombus formation. Imbalance of both subpopulations can lead to undesired thrombotic or bleeding events. COAT platelets derive from a common pro-aggregatory phenotype in cells capable of accumulating enough cytosolic calcium to trigger specific pathways that mediate the loss of their aggregating properties and the development of new adhesive and procoagulant characteristics. Complex cascades of signaling events are involved and this may explain why an inter-individual variability exists in procoagulant potential. Nowadays, we know the key agonists and mediators underlying the generation of a procoagulant platelet response. However, we still lack insight into the actual mechanisms controlling this dichotomous pattern (i.e., procoagulant versus aggregating phenotype). In this review, we describe the phenotypic characteristics of procoagulant COAT platelets, we detail the current knowledge on the mechanisms of the procoagulant response, and discuss possible drivers of this dichotomous diversification, in particular addressing the impact of the platelet environment during in vivo thrombus formation.

Platelet Membrane: An Outstanding Factor in Cancer Metastasis

In addition to being biological barriers where the internalization or release of biomolecules is decided, cell membranes are contact structures between the interior and exterior of the cell. Here, the processes of cell signaling mediated by receptors, ions, hormones, cytokines, enzymes, growth factors, extracellular matrix (ECM), and vesicles begin. They triggering several responses from the cell membrane that include rearranging its components according to the immediate needs of the cell, for example, in the membrane of platelets, the formation of filopodia and lamellipodia as a tissue repair response. In cancer, the cancer cells must adapt to the new tumor microenvironment (TME) and acquire capacities in the cell membrane to transform their shape, such as in the case of epithelial−mesenchymal transition (EMT) in the metastatic process. The cancer cells must also attract allies in this challenging process, such as platelets, fibroblasts associated with cancer (CAF), stromal cells, adipocytes, and the extracellular matrix itself, which limits tumor growth. The platelets are enucleated cells with fairly interesting growth factors, proangiogenic factors, cytokines, mRNA, and proteins, which support the development of a tumor microenvironment and support the metastatic process. This review will discuss the different actions that platelet membranes and cancer cell membranes carry out during their relationship in the tumor microenvironment and metastasis.

Von Willebrand disease type 2M: Correlation between genotype and phenotype

BACKGROUND

An appropriate clinical diagnosis of von Willebrand disease (VWD) can be challenging because of a variable bleeding pattern and laboratory phenotype. Genotyping is a powerful diagnostic tool and may have an essential role in the diagnostic field of VWD.

OBJECTIVES

To unravel the clinical and laboratory heterogeneity of genetically confirmed VWD type 2M patients and to investigate their relationship.

METHODS

Patients with a confirmed VWD type 2M genetic variant in the A1 or A3 domain of von Willebrand factor (VWF) and normal or only slightly aberrant VWF multimers were selected from all subjects genotyped at the Radboud university medical center because of a high suspicion of VWD. Bleeding scores and laboratory results were analyzed.

RESULTS

Fifty patients had a clinically relevant genetic variant in the A1 domain. Median bleeding score was 5. Compared with the nationwide Willebrand in the Netherlands study type 2 cohort, bleeding after surgery or delivery was reported more frequently and mucocutaneous bleedings less frequently. Median VWF activity/VWF antigen (VWF:Act/VWF:Ag) ratio was 0.32, whereas VWF collagen binding activity/VWF antigen (VWF:CB/VWF:Ag) ratio was 0.80. Variants in the A3 domain were only found in two patients with low to normal VWF:Act/VWF:Ag ratios (0.45, 1.03) and low VWF:CB/VWF:Ag ratios (0.45, 0.63).

CONCLUSION

Genetically confirmed VWD type 2M patients have a relatively mild clinical phenotype, except for bleeding after surgery and delivery. Laboratory phenotype is variable and depends on the underlying genetic variant. Addition of genotyping to the current phenotypic characterization may improve diagnosis and classification of VWD.

The Impact of Age and BMI on the VWF/ADAMTS13 Axis and Simultaneous Thrombin and Plasmin Generation in Hospitalized COVID-19 Patients

Aging and obesity independently contribute toward an endothelial dysfunction that results in an imbalanced VWF to ADAMTS13 ratio. In addition, plasma thrombin and plasmin generation are elevated and reduced, respectively, with increasing age and also with increasing body mass index (BMI). The severity risk of Corona Virus Disease 2019 (COVID-19) increases in adults older than 65 and in individuals with certain pre-existing health conditions, including obesity (>30 kg/m²). The present cross-sectional study focused on an analysis of the VWF/ADAMTS13 axis, including measurements of von Willebrand factor (VWF) antigen (VWF:AG), VWF collagen binding activity (VWF:CBA), Factor VIII antigen, ADAMTS13 antigen, and ADAMTS13 activity, in addition to thrombin and plasmin generation potential, in a demographically diverse population of COVID-19 negative (−) (n = 288) and COVID-19 positive (+) (n = 543) patient plasmas collected at the time of hospital presentation. Data were analyzed as a whole, and then after dividing patients by age (<65 and ≥65) and independently by BMI [<18.5, 18.5–24.9, 25–29.9, >30 (kg/m²)]. These analyses suggest that VWF parameters (i.e., the VWF/ADAMTS13 activity ratio) and thrombin and plasmin generation differed in COVID-19 (+), as compared to COVID-19 (−) patient plasma. Further, age (≥65) more than BMI contributed to aberrant plasma indicators of endothelial coagulopathy. Based on these findings, evaluating both the VWF/ADAMTS13 axis, along with thrombin and plasmin generation, could provide insight into the extent of endothelial dysfunction as well as the plasmatic imbalance in coagulation and fibrinolysis potential, particularly for at-risk patient populations.

Factor IX(a) inhibitors: an updated patent review (2003-present)

INTRODUCTION

Anticoagulation with no bleeding complications is the current objective of drug discovery programs in the area of treating and/or preventing thromboembolism. Despite the promises of therapeutics targeting factors XI(a) and XII(a), none has been approved thus far. Clinically used thrombin- and/or factor Xa-based anticoagulants continue to be associated with a significant bleeding risk which limits their safe use in a broad range of thrombotic patients. Research findings in animals and humans indicate that it is possible to target factor IX(a) (FIX(a)) to achieve anticoagulation with a limited risk of bleeding.

AREAS COVERED

A review of patents literature has retrieved >35 patents on the development of molecules targeting FIX(a) since 2003. Small molecules, antibodies, and aptamers have been developed to target FIX(a) to potentially promote effective and safer anticoagulation. Most of these agents are in the pre-clinical development phase and few have been tested in clinical trials.

EXPERT OPINION

FIX(a) system is being considered to develop new anticoagulants with fewer bleeding complications. Our survey indicates that the number of FIX(a)-targeting agents is mediocre. The agents under development are diverse. Although additional development is essential, moving one or more of these agents to the clinic will facilitate achieving better clinical outcomes.

Gastrointestinal Bleeding in Congenital Bleeding Disorders

Gastrointestinal bleeding (GIB) is serious, intractable, and potentially life-threatening condition. There is considerable heterogeneity in GIB phenotypes among congenital bleeding disorders (CBDs), making GIB difficult to manage. Although GIB is rarely encountered in CBDs, its severity in some patients makes the need for a comprehensive and precise assessment of underlying factors and management approaches imperative. Initial evaluation of GIB begins with assessment of hematological status; GIB should be ruled out in patients with chronic anemia, and in presentations that include hematemesis, hematochezia, or melena. High-risk patients with recurrent GIB require urgent interventions such as replacement therapy for treatment of coagulation factor deficiency (CFD). However, the best management strategy for CFD-related bleeding remains controversial. While several investigations have identified CBDs as potential risk factors for GIB, research has focused on assessing the risks for individual factor deficiencies and other CBDs. This review highlights recent findings on the prevalence, management strategies, and alternative therapies of GIB related to CFDs, and platelet disorders.

Acquired von Willebrand syndrome is common in infants with systemic-to-pulmonary shunts: Retrospective case-series

BACKGROUND

Although acquired von Willebrand syndrome (aVWS) has been described in congenital heart disease before, anatomical features leading to aVWS with characteristic reduction or loss of high molecular weight von Willebrand multimers (HMWM) are not well known. This study assesses the prevalence and effects of aVWS in infants with systemic-to-pulmonary shunts (SPS).

METHODS

This retrospective single-center study analyzes diagnostic data of infants with complex congenital heart defects requiring palliation with SPS. During the study period between 12/15-01/17 fifteen consecutive patients were eligible for analysis. Results of von Willebrand factor antigen (VWF:Ag), collagen binding activity (VWF:CB) and von Willebrand factor multimer analysis were included.

RESULTS

In all 15 patients with SPS an aVWS could be found. Blood samples were collected between 5 and 257 days after shunt implantation (median 64 days). None of the patients demonstrated increased bleeding in everyday life. However, 6 out of 15 patients (40%) showed postoperative bleeding complications after SPS implantation. Following shunt excision multimeric pattern normalized in 8 of 10 (80%) patients studied.

CONCLUSIONS

This study shows that in patients undergoing SPS implantation aVWS might emerge. Pathogenesis can be explained by shear stress resulting from turbulent flow within the shunt. Knowledge of aVWS existence is important for the consideration of replacement therapy with von Willebrand factor containing products and antifibrinolytic treatment in bleeding situations. Implementation of methods for rapid aVWS detection is required to achieve differentiated hemostatic therapy and reduce the risk of complications caused by empiric replacement therapy.

PI3K Isoform Signalling in Platelets

Platelets are unique anucleated blood cells that constantly patrol the vasculature to seal and prevent injuries in a process termed haemostasis. Thereby they rapidly adhere to the subendothelial matrix and recruit further platelets, resulting in platelet aggregates. Apart from their central role in haemostasis, they also kept some of their features inherited by their evolutionary ancestor-the haemocyte, which was also involved in immune defences. Together with leukocytes, platelets fight pathogenic invaders and guide many immune processes. In addition, they rely on several signalling pathways which are also relevant to immune cells. Among these, one of the central signalling hubs is the PI3K pathway. Signalling processes in platelets are unique as they lack a nucleus and therefore transcriptional regulation is absent. As a result, PI3K subclasses fulfil distinct roles in platelets compared to other cells. In contrast to leukocytes, the central PI3K subclass in platelet signalling is PI3K class Iβ, which underlines the uniqueness of this cell type and opens new ways for potential platelet-specific pharmacologic inhibition. An overview of platelet function and signalling with emphasis on PI3K subclasses and their respective inhibitors is given in this chapter.

Detection of Sepsis in Platelets Using MicroRNAs and Membrane Antigens

The present study proposes to legitimize in sepsis a characteristic found in platelets that suffer storage lesions in blood banks, which is the increased expression of miRNA miR-320a in relation to miR-127. Under physiologically normal conditions, an inverse relationship is observed. The aim of this study was to verify whether the analysis of miR-320a and miR-127 expression in platelets could detect a decrease in their viability and function due to the presence of pathogens in the blood of patients hospitalized in the Intensive Care Unit. We also investigated the expression of membrane antigens sensitive to platelet activation. Of the 200 patients analyzed, only those who developed sepsis (140) were found to have a higher relative quantity of miR-320a than that of miR-127. This characteristic and the increased expression of membrane antigens P2Y12, CD62P, CD41, and CD61 showed a significant association (p < 0.01) with all types of sepsis evaluated in this study. Additionally, 40% of patients hospitalized for sepsis had negative results for the first cultures. We conclude that analysis of miR-127 and miR-320a expression combined with membrane antigens evaluation, in association with the available clinical and diagnostic parameters, are important tools to detect the onset of sepsis.

Staphylococcus aureus iron-regulated surface determinant B (IsdB) protein interacts with von Willebrand factor and promotes adherence to endothelial cells

Staphylococcus aureus is the cause of a spectrum of diseases in humans and animals. The molecular basis of this pathogenicity lies in the expression of a variety of virulence factors, including proteins that mediate adherence to the host plasma and extracellular matrix proteins. In this study, we discovered that the iron-regulated surface determinant B (IsdB) protein, besides being involved in iron transport and vitronectin binding, interacts with von Willebrand Factor (vWF). IsdB-expressing bacteria bound to both soluble and immobilized vWF. The binding of recombinant IsdB to vWF was blocked by heparin and reduced at high ionic strength. Furthermore, treatment with ristocetin, an allosteric agent that promotes the exposure of the A1 domain of vWF, potentiates the binding of IsdB to vWF. Both near-iron transporter motifs NEAT1 and NEAT2 of IsdB individually bound recombinant A1 domain with K_D values in the micromolar range. The binding of IsdB and adhesion of S. aureus expressing IsdB to monolayers of activated endothelial cells was significantly inhibited by a monoclonal antibody against the A1 domain and by IsdB reactive IgG from patients with staphylococcal endocarditis. This suggests the importance of IsdB in adherence of S. aureus to the endothelium colonization and as potential therapeutic target.

The Proteoglycan Biglycan Modulates Platelet Adhesion and Thrombus Formation in a GPVI-Dependent Manner

BACKGROUND

Vascular injury induces the exposure of subendothelial extracellular matrix (ECM) important to serve as substrate for platelets to adhere to the injured vessel wall to avoid massive blood loss. Different ECM proteins are known to initiate platelet adhesion and activation. In atherosclerotic mice, the small, leucine-rich proteoglycan biglycan is important for the regulation of thrombin activity via heparin cofactor II. However, nothing is known about the role of biglycan for hemostasis and thrombosis under nonatherosclerotic conditions.

METHODS

The role of biglycan for platelet adhesion and thrombus formation was investigated using a recombinant protein and biglycan knockout mice.

RESULTS

The present study identified biglycan as important ECM protein for the adhesion and activation of platelets, and the formation of three-dimensional thrombi under flow conditions. Platelet adhesion to immobilized biglycan induces the reorganization of the platelet cytoskeleton. Mechanistically, biglycan binds and activates the major collagen receptor glycoprotein (GP)VI, because reduced platelet adhesion to recombinant biglycan was observed when GPVI was blocked and enhanced tyrosine phosphorylation in a GPVI-dependent manner was observed when platelets were stimulated with biglycan. In vivo, the deficiency of biglycan resulted in reduced platelet adhesion to the injured carotid artery and prolonged bleeding times.

CONCLUSIONS

Loss of biglycan in the vessel wall of mice but not in platelets led to reduced platelet adhesion at the injured carotid artery and prolonged bleeding times, suggesting a crucial role for biglycan as ECM protein that binds and activates platelets via GPVI upon vessel injury.

Update on endothelial dysfunction in COVID-19: severe disease, long COVID-19 and pediatric characteristics

Objectives

To review current literature on the role of endothelial dysfunction in coronavirus disease-2019 (COVID-19) infection in terms of pathophysiology, laboratory features and markers, clinical phenotype in adults and children, as well as long COVID-19.

Content

We conducted a thorough assessment of the literature and critically analyzed current data, mostly utilizing the PubMed and Medline search engines to find original studies published in the previous decade.

Summary and Outlook

Accumulating evidence suggests that endothelial dysfunction may be a common denominator of severe COVID-19 in adults and children, as well as long COVID-19, implicating mutual pathophysiological pathways. This narrative review summarizes the up-to-date knowledge of endothelial dysfunction caused by COVID-19, including novel aspects of long COVID-19 and pediatric disease. This knowledge is important in order not only to understand the multisystemic attack of COVID-19, but also to improve patient management and prognosis.

Biomaterial and cellular implants:foreign surfaces where immunity and coagulation meet

Exposure of blood to a foreign surface in the form of a diagnostic or therapeutic biomaterial device or implanted cells or tissues, elicits an immediate, evolutionarily conserved thrombo-inflammatory response by the host. Primarily designed to protect against invading organisms following an injury, this innate response features instantaneous activation of several blood-borne, highly interactive and well-orchestrated cascades and cellular events that limit bleeding, destroy and eliminate the foreign substance/cells, and promote healing and a return to homeostasis via delicately balanced regenerative processes. In the setting of blood-contacting synthetic or natural biomaterials and implantation of foreign cells/tissues, innate responses are robust, albeit highly context-specific. Unfortunately, they tend to be less than adequately regulated by the host's natural anti-coagulant/anti-inflammatory pathways, thereby jeopardizing the functional integrity of the device, as well as the health of the host. Strategies to achieve biocompatibility with a sustained return to homeostasis, particularly while the device remains in situ and functional, continue to elude scientists and clinicians. In this review, some of the complex mechanisms by which biomaterials and cellular transplants provide a "hub" for activation and amplification of coagulation and immunity - thrombo-inflammation - will be discussed, with a view toward the development of innovative means of overcoming the innate challenges.