Platelet Biorheology and Mechanobiology in Thrombosis and Hemostasis: Perspectives from Multiscale Computation.

Thrombosis is the pathological clot formation under abnormal hemodynamic conditions, which can result in vascular obstruction, causing ischemic strokes and myocardial infarction. Thrombus growth under moderate to low shear (<1000 s-1) relies on platelet activation and coagulation. Thrombosis at elevated high shear rates (>10,000 s-1) is predominantly driven by unactivated platelet binding and aggregating mediated by von Willebrand factor (VWF), while platelet activation and coagulation are secondary in supporting and reinforcing the thrombus. Given the molecular and cellular level information it can access, multiscale computational modeling informed by biology can provide new pathophysiological mechanisms that are otherwise not accessible experimentally, holding promise for novel first-principle-based therapeutics. In this review, we summarize the key aspects of platelet biorheology and mechanobiology, focusing on the molecular and cellular scale events and how they build up to thrombosis through platelet adhesion and aggregation in the presence or absence of platelet activation. In particular, we highlight recent advancements in multiscale modeling of platelet biorheology and mechanobiology and how they can lead to the better prediction and quantification of thrombus formation, exemplifying the exciting paradigm of digital medicine.

Abstracts of the 12th Congress of the Asian-Pacific Society of Thrombosis and Haemostasis (APSTH) 2023 "Haemostasis and Thrombosis: Bench to bedside", was held at Borneo Convention Centre Kuching (BCCK), Sarawak on 18th to 21st October 2023.

No abstract available.

A comparison between radial artery compression devices for patent hemostasis after transradial percutaneous interventions.

OBJECTIVES: Patent hemostasis (PH) is essential for preventing radial artery occlusion (RAO) after trans-radial procedures; however, it remains unclear how it should be obtained. The aim of this multicenter randomized study was to evaluate whether the use of an adjustable device (AD), inflated with a pre-determined amount of air (AoA), was more effective than a non-adjustable device (non-AD) for achieving PH, thereby reducing the incidence of RAO. METHODS: We enrolled a total of 480 patients undergoing transradial procedure at 3 Italian institutions. Before the procedure, a modified Reverse Barbeau Test (mRBT) was performed in all patients to evaluate the AoA to be eventually inflated in the AD. After the procedure, patients were randomized into 2 groups: (1) AD Group, using TR-Band (Terumo) inflated with the pre-determined AoA; and 2) non-AD Group, using RadiStop (Abbott). An RBT was performed during compression to demonstrate the achievement of PH, as well as 24 hours later to evaluate the occurrence of RAO. RESULTS: PH was more often obtained in the AD Group compared with the non-AD Group (90% vs 64%, respectively, P less than .001), with no difference in terms of bleedings. RAO occurred more often in the non-AD Group compared with the AD Group (10% vs 3%, respectively, P less than .001). Of note, mRBT was effective at guiding AD inflation and identifying high-risk patients in whom PH was more difficult to obtain. CONCLUSIONS: The use of AD, filled with a predetermined AoA, allowed PH significantly more often compared with non-AD, providing a significantly reduced incidence of RAO.

A Brief History of Hemostasis and Thrombosis at the Mayo Clinic.

Coagulation is a crucial biological mechanism in human bodies to prevent blood loss. Abnormal coagulation can cause bleeding diathesis or thrombosis, common pathologic conditions in our clinical practice. Many individuals and organizations have dedicated their efforts in the past decades to understanding the biological and pathological mechanisms of coagulation and developing laboratory testing tools and treatment options to help patients with bleeding or thrombotic conditions. Since 1926, the Mayo Clinic coagulation group has made significant contributions to the clinical and laboratory practice, basic and translational research on various hemostatic and thrombotic disorders, and the education and collaboration to share and advance our knowledge in coagulation through a highly integrated team and practice model. We would like to use this review to share our history and inspire medical professionals and trainees to join the efforts to advance our understanding of coagulation pathophysiology and improve our care for patients with coagulation disorders.

A journey to vasculopathy in systemic sclerosis: focus on haemostasis and thrombosis.

Systemic sclerosis is a multisystem connective tissue disease, characterized by endothelial autoimmune activation, along with tissue and vascular fibrosis leading to vasculopathy and to a progressive loss of angiogenesis. This condition further deranges the endothelial barrier favouring the opening of the endothelial junctions allowing the vascular leak in the surrounding tissues: this process may induce cell detachment which allows the contact between platelets and collagen present in the exposed subendothelial layer. Platelets first adhere to collagen via glycoprotein VI and then, immediately aggregate because of the release of von Willebrand factor which is a strong activator of platelet aggregation. Activated platelets exert their procoagulant activity, exposing on their membrane phospholipids and phosphatidylserine, enabling the adsorption of clotting factors ready to form thrombin which in turn drives the amplification of the coagulative cascade. An essential role in the activation of blood coagulation is the tissue factor (TF), which triggers blood coagulation. The TF is found abundantly in the subendothelial collagen and is also expressed by fibroblasts providing a haemostatic covering layer ready to activate coagulation when the endothelial injury occurs. The aim of this review is to focus the attention on the underlying mechanisms related to haemostasis and thrombosis pathophysiology which may have a relevant role in SSc as well as on a possible role of anticoagulation in this disease.

Mitochondrial gene expression is required for platelet function and blood clotting.

Platelets are anucleate blood cells that contain mitochondria and regulate blood clotting in response to injury. Mitochondria contain their own gene expression machinery that relies on nuclear-encoded factors for the biogenesis of the oxidative phosphorylation system to produce energy required for thrombosis. The autonomy of the mitochondrial gene expression machinery from the nucleus is unclear, and platelets provide a valuable model to understand its importance in anucleate cells. Here, we conditionally delete Elac2, Ptcd1, or Mtif3 in platelets, which are essential for mitochondrial gene expression at the level of RNA processing, stability, or translation, respectively. Loss of ELAC2, PTCD1, or MTIF3 leads to increased megakaryocyte ploidy, elevated circulating levels of reticulated platelets, thrombocytopenia, and consequent extended bleeding time. Impaired mitochondrial gene expression reduces agonist-induced platelet activation. Transcriptomic and proteomic analyses show that mitochondrial gene expression is required for fibrinolysis, hemostasis, and blood coagulation in response to injury.

Hemostasis without clot formation: how platelets guard the vasculature in inflammation, infection, and malignancy.

Platelets are key vascular effectors in hemostasis, with activation signals leading to fast recruitment, aggregation, and clot formation. The canonical process of hemostasis is well-characterized and shares many similarities with pathological thrombus formation. However, platelets are also crucially involved in the maintenance of vascular integrity under both steady-state and inflammatory conditions by ensuring blood vessel homeostasis and preventing microbleeds. In these settings, platelets use distinct receptors, signaling pathways, and ensuing effector functions to carry out their deeds. Instead of simply forming clots, they mainly act as individual sentinels that swiftly adapt their behavior to the local microenvironment. In this review, we summarize previously recognized and more recent studies that have elucidated how anucleate, small platelets manage to maintain vascular integrity when faced with challenges of infection, sterile inflammation, and even malignancy. We dissect how platelets are recruited to the vascular wall, how they identify sites of injury, and how they prevent hemorrhage as single cells. Furthermore, we discuss mechanisms and consequences of platelets' interaction with leukocytes and endothelial cells, the relevance of adhesion as well as signaling receptors, in particular immunoreceptor tyrosine-based activation motif receptors, and cross talk with the coagulation system. Finally, we outline how recent insights into inflammatory hemostasis and vascular integrity may aid in the development of novel therapeutic strategies to prevent hemorrhagic events and vascular dysfunction in patients who are critically ill.

Mechanisms regulating heterogeneity of hemostatic gene expression in endothelial cells.

The hemostatic system involves an array of circulating coagulation factors that work in concert with platelets and the vascular endothelium to promote clotting in a space- and time-defined manner. Despite equal systemic exposure to circulating factors, bleeding and thrombotic diseases tend to prefer specific sites, suggesting an important role for local factors. This may be provided by endothelial heterogeneity. Endothelial cells differ not only between arteries, veins, and capillaries but also between microvascular beds from different organs, which present unique organotypic morphology and functional and molecular profiles. Accordingly, regulators of hemostasis are not uniformly distributed in the vasculature. The establishment and maintenance of endothelial diversity are orchestrated at the transcriptional level. Recent transcriptomic and epigenomic studies have provided a global picture of endothelial cell heterogeneity. In this review, we discuss the organotypic differences in the hemostatic profile of endothelial cells; we focus on 2 major endothelial regulators of hemostasis, namely von Willebrand factor and thrombomodulin, to provide examples of transcriptional mechanisms that control heterogeneity; finally, we consider some of the methodological challenges and opportunities for future studies.

DYNAMICS OF INDICATORS IN PLATELET HEMOSTASIS IN POLYTRAUMA AND ENLARGED BODY MASS INDEX.

OBJECTIVE: The aim: Analyze the dynamics of indicators in platelet hemostasis in polytrauma and enlarged body mass index. PATIENTS AND METHODS: Materials and methods: A comprehensive study of hemostasis was performed in 224 sick with polytrauma and high body mass index within a month and on the 360th day. RESULTS: Results: In Group I, the aggregation time was shortened during stimulation of ristomycin by 25% from day 1 to day 3. In patients in the II group, with the addition of ADP, the presence of hyperaggregation of platelets was determined from the 1st to the 3rd day and from the 30th to the 360th (a 36% reduction in time compared to the control was determined). In patients in the III group, ADP-aggregation was reduced on the 1st day (by 34%), after which hypoaggregation was noted (from the 3rd to the 14th and on the 360th day) with an increase in the rate of approximately 33% compared to the control group, after which there was a persistent hyperaggregation from 30 to 360 day with a 25% reduction in aggregation time. CONCLUSION: Conclusions: An individual response of platelets to damage was established depending on the severity of polytrauma and increased body mass index.

Platelet protein synthesis, regulation, and post-translational modifications: mechanics and function.

Dogma had been firmly entrenched in the minds of the scientific community that the anucleate mammalian platelet was incapable of protein biosynthesis since their identification in the late 1880s. These beliefs were not challenged until the 1960s when several reports demonstrated that platelets possessed the capacity to biosynthesize proteins. Even then, many still dismissed the synthesis as trivial and unimportant for at least another two decades. Research in the field expanded after the 1980s and numerous reports have since been published that now clearly demonstrate the potential significance of platelet protein synthesis under normal, pathological, and activating conditions. It is now clear that the platelet proteome is not a static entity but can be altered slowly or rapidly in response to external signals to support physiological requirements to maintain hemostasis and other biological processes. All the necessary biological components to support protein synthesis have been identified in platelets along with post-transcriptional processing of mRNAs, regulators of translation, and post-translational modifications such as glycosylation. The last comprehensive review of the subject appeared in 2009 and much work has been conducted since that time. The current review of the field will briefly incorporate the information covered in earlier reviews and then bring the reader up to date with more recent findings.

Laboratory Testing of Hemostasis in Pregnancy: A Brief Overview.

Normal pregnancy is associated with significant physiological changes in the coagulation and fibrinolytic systems with an inclination toward a hypercoagulable state. This includes an increase in plasma levels of most clotting factors, a decrease in endogenous anticoagulants, and inhibition of fibrinolysis. Although these changes are critical in maintaining placental function and reducing postpartum hemorrhage, they may contribute to an increased risk of thromboembolism, particularly toward the end of pregnancy and during puerperium. Hemostasis parameters and the non-pregnant population reference ranges cannot be used in the assessment of bleeding or thrombotic complication risk during pregnancy, and pregnancy-specific information and reference ranges are not always available to support the interpretation of laboratory tests. This review aims to summarize the use of relevant hemostasis tests to promote evidence-based interpretation of laboratory test results as well as discuss challenges associated with testing during pregnancy.

An autologous blood-derived patch as a hemostatic agent: evidence from thromboelastography experiments and a porcine liver punch biopsy model.

Perioperative bleeding is a common complication in surgeries that increases morbidity, risk of mortality, and leads to increased socioeconomic costs. In this study we investigated a blood-derived autologous combined leukocyte, platelet, and fibrin patch as a new means of activating coagulation and maintaining hemostasis in a surgical setting. We evaluated the effects of an extract derived from the patch on the clotting of human blood in vitro, using thromboelastography (TEG). The autologous blood-derived patch activated hemostasis, seen as a reduced mean activation time compared to both non-activated controls, kaolin-activated samples, and fibrinogen/thrombin-patch-activated samples. The accelerated clotting was reproducible and did not compromise the quality or stability of the resulting blood clot. We also evaluated the patch in vivo in a porcine liver punch biopsy model. In this surgical model we saw 100% effective hemostasis and a significant reduction of the time-to-hemostasis, when compared to controls. These results were comparable to the hemostatic properties of a commercially available, xenogeneic fibrinogen/thrombin patch. Our findings suggest clinical potential for the autologous blood-derived patch as a hemostatic agent.

Blood Platelets in Infection: The Multiple Roles of the Platelet Signalling Machinery.

Platelets are classically recognized for their important role in hemostasis and thrombosis but they are also involved in many other physiological and pathophysiological processes, including infection. Platelets are among the first cells recruited to sites of inflammation and infection and they exert their antimicrobial response actively cooperating with the immune system. This review aims to summarize the current knowledge on platelet receptor interaction with different types of pathogens and the consequent modulations of innate and adaptive immune responses.

Platelets, Protean Cells with All-Around Functions and Multifaceted Pharmacological Applications.

Platelets, traditionally known for their roles in hemostasis and coagulation, are the most prevalent blood component after erythrocytes (150,000-400,000 platelets/µL in healthy humans). However, only 10,000 platelets/µL are needed for vessel wall repair and wound healing. Increased knowledge of the platelet's role in hemostasis has led to many advances in understanding that they are crucial mediators in many other physiological processes, such as innate and adaptive immunity. Due to their multiple functions, platelet dysfunction is involved not only in thrombosis, mediating myocardial infarction, stroke, and venous thromboembolism, but also in several other disorders, such as tumors, autoimmune diseases, and neurodegenerative diseases. On the other hand, thanks to their multiple functions, nowadays platelets are therapeutic targets in different pathologies, in addition to atherothrombotic diseases; they can be used as an innovative drug delivery system, and their derivatives, such as platelet lysates and platelet extracellular vesicles (pEVs), can be useful in regenerative medicine and many other fields. The protean role of platelets, from the name of Proteus, a Greek mythological divinity who could take on different shapes or aspects, is precisely the focus of this review.

Factor VII Activating Protease (FSAP) and Its Importance in Hemostasis-Part I: FSAP Structure, Synthesis and Activity Regulation: A Narrative Review.

Factor VII activating protease (FSAP) was first isolated from human plasma less than 30 years ago. Since then, many research groups have described the biological properties of this protease and its role in hemostasis and other processes in humans and other animals. With the progress of knowledge about the structure of FSAP, several of its relationships with other proteins or chemical compounds that may modulate its activity have been explained. These mutual axes are described in the present narrative review. The first part of our series of manuscripts on FSAP describes the structure of this protein and the processes leading to the enhancement and inhibition of its activities. The following parts, II and III, concern the role of FSAP in hemostasis and in the pathophysiology of human diseases, with particular emphasis on cardiovascular diseases.

Artificial cerebrospinal fluid restores aspirin-inhibited physiological hemostasis through recovery of platelet aggregation function.

BACKGROUND: Optimal hemostasis provides safety and reliability during neurosurgery which improves surgical outcomes. Previously, artificial cerebrospinal fluid (aCSF) and its component sodium bicarbonate were found to facilitate physiological hemostasis by amplifying platelet aggregation. This study aimed to verify whether aCSF amplifies platelet-dependent hemostasis in the presence of antiplatelet agents. METHODS: We prepared platelet-rich plasma (PRP) or washed platelets using aspirin (acetylsalicylic acid, (ASA)) or normal saline (NS). We evaluated samples treated with a commercially available aCSF solution or NS for amplification of aggregation, activation of integrin αIIbß3, phosphatidylserine (PS) exposure, P-selectin (CD62P) expression, and formation of microparticles (MPs). We assessed the effect of aCSF on in vivo hemostasis in the presence of ASA by measuring the tail bleeding time in ASA-or NS-injected C57BL/6 N mice. RESULTS: Compared with NS, aCSF amplified ASA-inhibited platelet aggregation by recovering platelet activation including PS exposure, MP release, CD62P expression, and integrin αIIbß3 activation. When using washed platelets, aCSF almost completely counteracted the inhibition of platelet aggregation by ASA. Prolonged bleeding time from the amputated tail of ASA-injected mice was significantly shortened by the treatment with aCSF compared to NS. Sodium bicarbonate also directly amplified ASA-inhibited platelet aggregation. CONCLUSIONS: aCSF and sodium bicarbonate facilitate physiological hemostasis through the recovery of inhibited platelet aggregation even in the presence of ASA. The utilization of aCSF in the operative field may be advantageous for facilitating hemostasis in patients with impaired platelet function and contribute to improving outcomes of neurosurgery.

Dysregulated haemostasis in thrombo-inflammatory disease.

Inflammatory disease is often associated with an increased incidence of venous thromboembolism in affected patients, although in most instances, the mechanistic basis for this increased thrombogenicity remains poorly understood. Acute infection, as exemplified by sepsis, malaria and most recently, COVID-19, drives 'immunothrombosis', where the immune defence response to capture and neutralise invading pathogens causes concurrent activation of deleterious prothrombotic cellular and biological responses. Moreover, dysregulated innate and adaptive immune responses in patients with chronic inflammatory conditions, such as inflammatory bowel disease, allergies, and neurodegenerative disorders, are now recognised to occur in parallel with activation of coagulation. In this review, we describe the detailed cellular and biochemical mechanisms that cause inflammation-driven haemostatic dysregulation, including aberrant contact pathway activation, increased tissue factor activity and release, innate immune cell activation and programmed cell death, and T cell-mediated changes in thrombus resolution. In addition, we consider how lifestyle changes increasingly associated with modern life, such as circadian rhythm disruption, chronic stress and old age, are increasingly implicated in unbalancing haemostasis. Finally, we describe the emergence of potential therapies with broad-ranging immunothrombotic functions, and how drug development in this area is challenged by our nascent understanding of the key molecular and cellular parameters that control the shared nodes of proinflammatory and procoagulant pathways. Despite the increasing recognition and understanding of the prothrombotic nature of inflammatory disease, significant challenges remain in effectively managing affected patients, and new therapeutic approaches to curtail the key pathogenic steps in immune response-driven thrombosis are urgently required.