The role of tissue factor and factor VIIa in hemostasis

Evaluation of anti-sickling effects of two varieties of Cajanus cajan (L.) Huth on sickle cell beta thalassemia

ETHNO-PHARMACOLOGICAL RELEVANCE

Globally, the prevalence of sickle cell disease is on the rise, with developing countries experiencing particularly alarming mortality rate compared to developed nations. The World Health Organization (WHO) and United Nations (UN) have acknowledged sickle cell disease as a significant global public health concern. Unfortunately, a cure for this condition is yet to be discovered, and existing allopathic treatments, while offering relief, come with serious side effects. In recent times, there has been a growing interest in exploring the potential of medicinal plants for treating sickle cell disease due to their content of secondary metabolites that may impact the disease's mechanisms. Cajanus cajan, a crucial grain legume in rain-fed agriculture in semi-arid tropics, has been traditionally used in folk medicine to manage various illnesses and is suggested to possess anti-sickling properties.

AIM OF THE STUDY

The present study investigated two varieties of C. cajan for their effectiveness in treating sickle cell beta thalassemia, a variant of sickle cell disease.

MATERIALS AND METHODS

The study was divided into four groups consisting of the untreated group (group 1), group treated with standard drug (group 2), group treated with white C. cajan (group 3) and group treated with brown C. cajan (group 4). The effects of the two variety of C. cajan were measured by polymerization test, reversibility test, osmotic fragility test, deoxygenation and beta globin synthesis test.

RESULT

The results revealed that both varieties of C. cajan demonstrated a reduction in polymerization rates, reversed sickled red blood cells, increased the oxygen affinity of Hb-S/β, elevated the Fe2+/Fe3+ ratio, and maintained the membrane stability of red blood cells. Notably, the white variety exhibited superior anti-sickling properties compared to the brown variety.

CONCLUSION

This suggests that this significant leguminous crop could be utilized for the treatment and management of sickling disorders, particularly in low-income countries where conventional treatments may be financially inaccessible to patients.

Collaborative science in action: A 20 year perspective from the Health and Environmental Sciences Institute (HESI) Cardiac Safety Committee

The Health and Environmental Sciences Institute (HESI) is a nonprofit organization dedicated to resolving global health challenges through collaborative scientific efforts across academia, regulatory authorities and the private sector. Collaborative science across non-clinical disciplines offers an important keystone to accelerate the development of safer and more effective medicines. HESI works to address complex challenges by leveraging diverse subject-matter expertise across sectors offering access to resources, data and shared knowledge. In 2008, the HESI Cardiac Safety Committee (CSC) was established to improve public health by reducing unanticipated cardiovascular (CV)-related adverse effects from pharmaceuticals or chemicals. The committee continues to significantly impact the field of CV safety by bringing together experts from across sectors to address challenges of detecting and predicting adverse cardiac outcomes. Committee members have collaborated on the organization, management and publication of prospective studies, retrospective analyses, workshops, and symposia resulting in 38 peer reviewed manuscripts. Without this collaboration these manuscripts would not have been published. Through their work, the CSC is actively addressing challenges and opportunities in detecting potential cardiac failure modes using in vivo, in vitro and in silico models, with the aim of facilitating drug development and improving study design. By examining past successes and future prospects of the CSC, this manuscript sheds light on how the consortium's multifaceted approach not only addresses current challenges in detecting potential cardiac failure modes but also paves the way for enhanced drug development and study design methodologies. Further, exploring future opportunities and challenges will focus on improving the translational predictability of nonclinical evaluations and reducing reliance on animal research in CV safety assessments.

Mechanisms of endothelial activation, hypercoagulation and thrombosis in COVID-19: a link with diabetes mellitus

Early since the onset of the COVID-19 pandemic, the medical and scientific community were aware of extra respiratory actions of SARS-CoV-2 infection. Endothelitis, hypercoagulation, and hypofibrinolysis were identified in COVID-19 patients as subsequent responses of endothelial dysfunction. Activation of the endothelial barrier may increase the severity of the disease and contribute to long-COVID syndrome and post-COVID sequelae. Besides, it may cause alterations in primary, secondary, and tertiary hemostasis. Importantly, these responses have been highly decisive in the evolution of infected patients also diagnosed with diabetes mellitus (DM), who showed previous endothelial dysfunction. In this review, we provide an overview of the potential triggers of endothelial activation related to COVID-19 and COVID-19 under diabetic milieu. Several mechanisms are induced by both the viral particle itself and by the subsequent immune-defensive response (i.e., NF-κB/NLRP3 inflammasome pathway, vasoactive peptides, cytokine storm, NETosis, activation of the complement system). Alterations in coagulation mediators such as factor VIII, fibrin, tissue factor, the von Willebrand factor: ADAMST-13 ratio, and the kallikrein-kinin or plasminogen-plasmin systems have been reported. Moreover, an imbalance of thrombotic and thrombolytic (tPA, PAI-I, fibrinogen) factors favors hypercoagulation and hypofibrinolysis. In the context of DM, these mechanisms can be exacerbated leading to higher loss of hemostasis. However, a series of therapeutic strategies targeting the activated endothelium such as specific antibodies or inhibitors against thrombin, key cytokines, factor X, complement system, the kallikrein-kinin system or NETosis, might represent new opportunities to address this hypercoagulable state present in COVID-19 and DM. Antidiabetics may also ameliorate endothelial dysfunction, inflammation, and platelet aggregation. By improving the microvascular pathology in COVID-19 and post-COVID subjects, the associated comorbidities and the risk of mortality could be reduced.

Functional hemostatic hydrogels: design based on procoagulant principles

Uncontrolled hemorrhage results in various complications and is currently the leading cause of death in the general population. Traditional hemostatic methods have drawbacks that may lead to ineffective hemostasis and even the risk of secondary injury. Therefore, there is an urgent need for more effective hemostatic techniques. Polymeric hemostatic materials, particularly hydrogels, are ideal due to their biocompatibility, flexibility, absorption, and versatility. Functional hemostatic hydrogels can enhance hemostasis by creating physical circumstances conducive to hemostasis or by directly interfering with the physiological processes of hemostasis. The procoagulant principles include increasing the concentration of localized hemostatic substances or establishing a physical barrier at the physical level and intervention in blood cells or the coagulation cascade at the physiological level. Moreover, synergistic hemostasis can combine these functions. However, some hydrogels are ineffective in promoting hemostasis or have a limited application scope. These defects have impeded the advancement of hemostatic hydrogels. To provide inspiration and resources for new designs, this review provides an overview of the procoagulant principles of hemostatic hydrogels. We also discuss the challenges in developing effective hemostatic hydrogels and provide viewpoints.

Progress in injectable hydrogels for the treatment of incompressible bleeding: an update

Uncontrollable haemorrhage from deep, noncompressible wounds remains a persistent and intractable challenge, accounting for a very high proportion of deaths in both war and disaster situations. Recently, injectable hydrogels have been increasingly studied as potential haemostatic materials, highlighting their enormous potential for the management of noncompressible haemorrhages. In this review, we summarize haemostatic mechanisms, commonly used clinical haemostatic methods, and the research progress on injectable haemostatic hydrogels. We emphasize the current status of injectable hydrogels as haemostatic materials, including their physical and chemical properties, design strategy, haemostatic mechanisms, and application in various types of wounds. We discuss the advantages and disadvantages of injectable hydrogels as haemostatic materials, as well as the opportunities and challenges involved. Finally, we propose cutting-edge research avenues to address these challenges and opportunities, including the combination of injectable hydrogels with advanced materials and innovative strategies to increase their biocompatibility and tune their degradation profile. Surface modifications for promoting cell adhesion and proliferation, as well as the delivery of growth factors or other biologics for optimal wound healing, are also suggested. We believe that this paper will inform researchers about the current status of the use of injectable haemostatic hydrogels for noncompressible haemorrhage and spark new ideas for those striving to propel this field forward.

Dimethyl fumarate and 4-octyl itaconate are anticoagulants that suppress Tissue Factor in macrophages via inhibition of Type I Interferon

Excessive inflammation-associated coagulation is a feature of infectious diseases, occurring in such conditions as bacterial sepsis and COVID-19. It can lead to disseminated intravascular coagulation, one of the leading causes of mortality worldwide. Recently, type I interferon (IFN) signaling has been shown to be required for tissue factor (TF; gene name F3) release from macrophages, a critical initiator of coagulation, providing an important mechanistic link between innate immunity and coagulation. The mechanism of release involves type I IFN-induced caspase-11 which promotes macrophage pyroptosis. Here we find that F3 is a type I IFN-stimulated gene. Furthermore, F3 induction by lipopolysaccharide (LPS) is inhibited by the anti-inflammatory agents dimethyl fumarate (DMF) and 4-octyl itaconate (4-OI). Mechanistically, inhibition of F3 by DMF and 4-OI involves suppression of Ifnb1 expression. Additionally, they block type I IFN- and caspase-11-mediated macrophage pyroptosis, and subsequent TF release. Thereby, DMF and 4-OI inhibit TF-dependent thrombin generation. In vivo, DMF and 4-OI suppress TF-dependent thrombin generation, pulmonary thromboinflammation, and lethality induced by LPS, E. coli, and S. aureus, with 4-OI additionally attenuating inflammation-associated coagulation in a model of SARS-CoV-2 infection. Our results identify the clinically approved drug DMF and the pre-clinical tool compound 4-OI as anticoagulants that inhibit TF-mediated coagulopathy via inhibition of the macrophage type I IFN-TF axis.

Impact of the COVID-19 Outbreak on the Treatment of Myocardial Infarction Patients

Purpose of review

The COVID-19 pandemic has led to an overburdened healthcare system. While an increased rate of ACS is expected due to the pro-thrombotic state of COVID patients, observed ACS incidence and admission rates were paradoxically decreased during the (first wave of the) pandemic. In this narrative review, we will discuss potential reasons for this decrease in ACS incidence. Furthermore, we will discuss ACS management during the COVID-19 pandemic, and we will discuss outcomes in ACS.

Recent findings

A reluctance to seek medical contact (in order not to further overburden the health system or due to fear of being infected with COVID-19 while in hospital) and unavailability of medical services seem to be important factors. This may have led to an increased symptom onset to first medical contact time and an increased rate of out-of-hospital cardiac arrests. A trend towards less invasive management was observed (less invasive coronary angiography in NSTEMI patients and more "fibrinolysis-first" in STEMI patients), although a large variation was observed with some centers having a relative increase in early invasive management. Patients with ACS and concomitant COVID-19 infection have worse outcomes compared to ACS patients without COVID-19 infection. All of the above led to worse clinical outcomes in patients presenting with ACS during the COVID-19 pandemic. Interestingly, staffing and hospital bed shortages led to experimentation with very early discharge (24 h after primary PCI) in low-risk STEMI patients which had a very good prognosis and resulted in significant shorter hospital duration.

Summary

During the COVID-19 pandemic, ACS incidence and admission rates were decreased, symptom onset to first medical contact time prolonged, and out-of-hospital rates increased. A trend towards less invasive management was observed. Patients presenting with ACS during the COVID-19 pandemic had a worse outcome. On the other hand, experimental very early discharge in low-risk patients may relieve the healthcare system. Such initiatives, and strategies to lower the reluctance of patients with ACS symptoms to seek medical help, are vital to improve prognosis in ACS patients in future pandemics.

Immobilization of blood coagulant factor VII on polycaprolactone membrane through polydopamine grafting

Postoperative bleeding following cardiac surgeries is still an issue that deranges the medical resources and cost. The oral and injection administrations of blood coagulation protein, Factor VII (FVII), is effective to stop the bleeding. However, its short half-life has limited the effectiveness of this treatment and frequent FVII intake may distress the patients. Instead, incorporating FVII into synthetic biodegradable polymers such as polycaprolactone (PCL) that is commonly used in drug delivery applications should provide a solution. Therefore, this study aimed to immobilize FVII on PCL membranes through a cross-linkage polydopamine (PDA) grafting as an intermediate layer. These membranes are intended to provide a solution for cardiac bleeding in coagulating blood and sealing the sutured region. The membranes were evaluated in terms of its physio-chemical properties, thermal behavior, FVII release profile and biocompatibility properties. The ATR-FTIR was used to analyze the chemical functionalities of the membranes. Further validation was done with XPS where the appearances of 0.45 ± 0.06% sulfur composition and C-S peak have confirmed the immobilization of FVII on the PCL membranes. The cross-linked FVIIs were viewed in spherical immobilization on the PCL membranes with a size range between 30 and 210 nm. The surface roughness and hydrophilicity of the membranes were enhanced with a slight shift of melting temperature. The PCL-PDA-FVII0.03 and PCL-PDA-FVII0.05 membranes, with wide area of FVII immobilization released approximately only 22% of FVII into the solution within 60 days period and, it is found that the PCL-PDA-FVIIx membranes projected the Higuchi release model with non-Fickian anomalous transport. While the cytotoxic and hemocompatibility analyses showed advance cell viability, identical coagulation time and low hemolysis ratio on the PCL-PDA-FVIIx membranes. The erythrocytes were viewed in polyhedrocyte coagulated structure under SEM visualization. These results validate the biocompatibility of the membranes and its ability to prolong blood coagulation, thus highlighting its potential application as cardiac bleeding sealant.

Crosstalk between Circulating Tumor Cells and Plasma Proteins-Impact on Coagulation and Anticoagulation

Cancer metastasis is a complex process. After their intravasation into the circulation, the cancer cells are exposed to a harsh environment of physical and biochemical hazards. Whether circulating tumor cells (CTCs) survive and escape from blood flow defines their ability to metastasize. CTCs sense their environment with surface-exposed receptors. The recognition of corresponding ligands, e.g., fibrinogen, by integrins can induce intracellular signaling processes driving CTCs' survival. Other receptors, such as tissue factor (TF), enable CTCs to induce coagulation. Cancer-associated thrombosis (CAT) is adversely connected to patients' outcome. However, cancer cells have also the ability to inhibit coagulation, e.g., through expressing thrombomodulin (TM) or heparan sulfate (HS), an activator of antithrombin (AT). To that extent, individual CTCs can interact with plasma proteins, and whether these interactions are connected to metastasis or clinical symptoms such as CAT is largely unknown. In the present review, we discuss the biological and clinical relevance of cancer-cell-expressed surface molecules and their interaction with plasma proteins. We aim to encourage future research to expand our knowledge of the CTC interactome, as this may not only yield new molecular markers improving liquid-biopsy-based diagnostics but also additional targets for better cancer therapies.

Intersection of Coagulation and Fibrinolysis by the Glycosylphosphatidylinositol (GPI)-Anchored Serine Protease Testisin

Hemostasis is a delicate balance between coagulation and fibrinolysis that regulates the formation and removal of fibrin, respectively. Positive and negative feedback loops and crosstalk between coagulation and fibrinolytic serine proteases maintain the hemostatic balance to prevent both excessive bleeding and thrombosis. Here, we identify a novel role for the glycosylphosphatidylinositol (GPI)-anchored serine protease testisin in the regulation of pericellular hemostasis. Using in vitro cell-based fibrin generation assays, we found that the expression of catalytically active testisin on the cell surface accelerates thrombin-dependent fibrin polymerization, and intriguingly, that it subsequently promotes accelerated fibrinolysis. We find that the testisin-dependent fibrin formation is inhibited by rivaroxaban, a specific inhibitor of the central prothrombin-activating serine protease factor Xa (FXa), demonstrating that cell-surface testisin acts upstream of factor X (FX) to promote fibrin formation at the cell surface. Unexpectedly, testisin was also found to accelerate fibrinolysis by stimulating the plasmin-dependent degradation of fibrin and enhancing plasmin-dependent cell invasion through polymerized fibrin. Testisin was not a direct activator of plasminogen, but it is able to induce zymogen cleavage and the activation of pro-urokinase plasminogen activator (pro-uPA), which converts plasminogen to plasmin. These data identify a new proteolytic component that can regulate pericellular hemostatic cascades at the cell surface, which has implications for angiogenesis, cancer biology, and male fertility.

Factor XIa Inhibitors in Anticoagulation Therapy: Recent Advances and Perspectives

Factor XIa (FXIa) in the intrinsic pathway of the coagulation process has been proven to be an effective and safe target for anticoagulant discovery with limited or no bleeding. Numerous small-molecule FXIa inhibitors (SMFIs) with various scaffolds have been identified in the early stages of drug discovery. They have served as the foundation for the recent discovery of additional promising SMFIs with improved potency, selectivity, and pharmacokinetic profiles, some of which have entered clinical trials for the treatment of thrombosis. After reviewing the coagulation process and structure of FXIa, this perspective discusses the rational or structure-based design, discovery, structure-activity relationships, and development of SMFIs disclosed in recent years. Strategies for identifying more selective and druggable SMFIs are provided, paving the way for the design and discovery of more useful SMFIs for anticoagulation therapy.

Von Willebrand Disease, Hemophilia, and Other Inherited Bleeding Disorders in Pregnancy

Inherited bleeding disorders, which comprise von Willebrand disease (VWD), hemophilia, other congenital clotting factor deficiencies, inherited platelet disorders, defects of fibrinolysis, and connective tissue disorders, have both maternal and fetal implications. Although mild platelet defects may actually be more prevalent, the most common diagnosed bleeding disorder among women is VWD. Other bleeding disorders, including hemophilia carriership, are much less common, but hemophilia carriers are unique in that they are at risk of giving birth to a severely affected male neonate. General guidance for maternal management of inherited bleeding disorders includes obtaining clotting factor levels in the third trimester, planning for delivery at a center with hemostasis expertise if factor levels do not meet the minimum threshold (eg, less than 0.50 international units/1 mL [50%] for von Willebrand factor, factor VIII, or factor IX), and using hemostatic agents such as factor concentrates, desmopressin, or tranexamic acid. General guidance for fetal management includes prepregnancy counseling, the option of preimplantation genetic testing for hemophilia, and consideration of delivery of potentially affected male neonates with hemophilia by cesarean delivery to reduce the risk of neonatal intracranial hemorrhage. In addition, delivery of possibly affected neonates should occur in a facility where there is newborn intensive care and pediatric hemostasis expertise. For patients with other inherited bleeding disorders, unless a severely affected neonate is anticipated, mode of delivery should be dictated by obstetric indications. Nonetheless, invasive procedures such as fetal scalp clip or operative vaginal delivery should be avoided, if possible, in any fetus potentially affected with a bleeding disorder.

Complement component C1q initiates extrinsic coagulation via the receptor for the globular head of C1q in adventitial fibroblasts and vascular smooth muscle cells

BACKGROUND

Vascular diseases are highly associated with inflammation and thrombosis. Elucidating links between these two processes may provide a clearer understanding of these diseases, allowing for the design of more effective treatments. The activation of complement component 1 (C1) is a crucial contributor to innate immunity and is associated with significant concentrations of circulating C1q. Many pathological pathways initiate when C1q interacts with gC1qR. This interaction plays a major role in inflammation observed during atherosclerosis and the initiation of intrinsic coagulation. However, the effects of C1 and the role of C1q/gC1qR on extrinsic coagulation, which is the more physiologically relevant coagulation arm, has not been studied. We hypothesized that C1q binding to gC1qR enhances the expression of tissue factor (TF) in adventitial fibroblasts and vascular smooth muscle cells, the primary TF bearing cells in the body.

METHODS

Using an enzyme-linked immunosorbent assay approach, TF expression and the role of gC1qR was observed. Cells were conditioned for 1 h with C1q or a gC1qR blocker and C1q, to assess the role of gC1qR. Additionally, cell growth characteristics were monitored to assess changes in viability and metabolic activity.

RESULTS

Our results indicate that the expression of TF increased significantly after incubation with C1q as compared with unconditioned cells. Cells conditioned with gC1qR blockers and C1q exhibited no change in TF expression when compared with cells conditioned with the blocking antibodies alone. Our results show no significant differences in metabolic activity or cell viability under these conditions.

CONCLUSIONS

This indicates that gC1qR association with C1q induces TF expression and may initiate extrinsic coagulation. Overall, this data illustrates a role for C1q in the activation of extrinsic coagulation and that gC1qR activity may link inflammation and thrombosis.

Analysis of Cerebrovascular Events after Coil Embolization of Unruptured Cerebral Aneurysms in Patients Taking Anticoagulants

Objective

Antiplatelet therapy is advised to prevent thrombotic complications during endovascular coil embolization of unruptured cerebral aneurysms. Due to multiple antithrombotic treatments, bleeding risk is a concern in patients using oral anticoagulants for existing comorbidities. We investigated the hemorrhagic and ischemic events following endovascular treatment (EVT) of unruptured cerebral aneurysms in patients taking anticoagulation and antiplatelet therapy.

Methods

Between March 2013 and February 2019, 262 patients undergoing EVT for unruptured cerebral aneurysms and having at least 6 months of postoperative follow-up data were included in this retrospective study. Patients taking oral anticoagulants and antiplatelet drugs for cerebral vascular events following EVT were compared with those taking only antiplatelet agents.

Results

Of the 262 patients, 12 (4.6%) used anticoagulants before EVT for a preexisting condition. Cerebrovascular events after coil embolization were observed in 3 patients taking both anticoagulant and antiplatelet drugs and in 14 patients taking only antiplatelet drugs (25% vs. 5.6%, respectively, p = 0.035). Vitamin K antagonist (VKA) was administered in five patients and direct oral anticoagulants (DOACs) in seven patients. Patients taking VKA experienced cerebrovascular events, whereas those taking DOACs did not (p = 0.045).

Conclusion

Our study showed that patients using oral anticoagulants and antiplatelet drugs experienced more cerebrovascular events after EVT for unruptured cerebral aneurysms. These results suggest that in patients requiring oral anticoagulants, DOACs may be more beneficial than VKA for preventing stroke occurrences after EVT.

"iPSC-derived liver organoids and inherited bleeding disorders: Potential and future perspectives"

The bleeding phenotype of hereditary coagulation disorders is caused by the low or undetectable activity of the proteins involved in hemostasis, due to a broad spectrum of genetic alterations. Most of the affected coagulation factors are produced in the liver. Therefore, two-dimensional (2D) cultures of primary human hepatocytes and recombinant overexpression of the factors in non-human cell lines have been primarily used to mimic disease pathogenesis and as a model for innovative therapeutic strategies. However, neither human nor animal cells fully represent the hepatocellular biology and do not harbor the exact genetic background of the patient. As a result, the inability of the current in vitro models in recapitulating the in vivo situation has limited the studies of these inherited coagulation disorders. Induced Pluripotent Stem Cell (iPSC) technology offers a possible solution to overcome these limitations by reprogramming patient somatic cells into an embryonic-like pluripotent state, thus giving the possibility of generating an unlimited number of liver cells needed for modeling or therapeutic purposes. By combining this potential and the recent advances in the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology, it allows for the generation of autologous and gene corrected liver cells in the form of three-dimensional (3D) liver organoids. The organoids recapitulate cellular composition and organization of the liver, providing a more physiological model to study the biology of coagulation proteins and modeling hereditary coagulation disorders. This advanced methodology can pave the way for the development of cell-based therapeutic approaches to treat inherited coagulation disorders. In this review we will explore the use of liver organoids as a state-of-the-art methodology for modeling coagulation factors disorders and the possibilities of using organoid technology to treat the disease.

Tissue Factor and COVID-19: An Update

The coronavirus 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. Infection with SARS-CoV-2 is associated with acute respiratory distress syndrome, thrombosis and a high rate of mortality. Thrombotic events increase with severity. Tissue factor (TF) expression is increased during viral and bacterial infections. This review summarizes studies that have examined TF expression in response to SARS-CoV-2 infection. SARS-CoV-2 virus and its proteins upregulate TF mRNA, protein and activity in a variety of cells, including bronchial epithelial cells, neutrophils, monocytes, macrophages, endothelial cells and adventitial fibroblasts. COVID-19 patients have increased TF expression in lungs, bronchoalveolar lavage fluid and circulating extracellular vesicles. The increase in TF was associated with coagulation activation markers, thrombosis, inflammatory markers, severity of disease and mortality. Taken together, the studies suggest that TF plays a central role in thrombosis in COVID- 19. TF may be a useful prognostic marker and therapeutic target to reduce thrombosis and inflammation.

Novel Classification of Thrombotic Disorders Based on Molecular Hemostasis and Thrombogenesis Producing Primary and Secondary Phenotypes of Thrombosis

Thrombosis, the common and deadliest disorder among human diseases, develops as a result of the intravascular hemostasis following an intravascular injury, which can be caused by a variety of trauma, non-traumatic insults or clinical illnesses. Thrombosis can occur at any location of the vascular system supplied by blood from the heart to large and smallest arterial and venous systems and may affect the function and anatomy of the organ and tissue. It more commonly occurs in the smaller circulatory system of the vascular tree such as arterioles and capillaries, and venules of the organs, especially in the brain, lungs, heart, pancreas, muscle and kidneys, and sinusoids of the liver. Thrombosis has been referred as the disease of "blood clots", which concept is incompletely defined, but represents many different hemostatic diseases from microthrombosis to fibrin clot disease, macrothrombosis, and combined micro-macrothrombosis. Thrombosis is produced following an intravascular injury via one or more combination of four different mechanisms of thrombogenesis: microthrombogenesis, fibrinogenesis, macrothrombogenesis and micro-macrothrombogenesis initiated by normal physiological hemostasis in vivo. The clinical phenotype expression of thrombosis is determined by: (1) depth of the intravascular wall injury, (2) extent of the injury affecting the vascular tree system, (3) physiological character of the involved vascular system, (4) locality of the vascular injury, and (5) underlying non-hemostatic conditions interacting with hemostasis. Recent acquisition of "two-path unifying theory" of hemostasis and "two-activation theory of the endothelium" has opened a new frontier in science of medicine by identifying the pathophysiological mechanism of different thrombotic disorders and also contributing to the better understanding of many poorly defined human diseases, including different phenotypes of stroke and cardiovascular disease, trauma, sepsis and septic shock, multiorgan dysfunction syndrome, and autoimmune disease, and others. Reviewed are the fundamentals in hemostasis, thrombogenesis and thrombosis based on hemostatic theories, and proposed is a novel classification of thrombotic disorders.

Platelet-Inspired Intravenous Nanomedicine for Injury-Targeted Direct Delivery of Thrombin to Augment Hemostasis in Coagulopathies

Severe hemorrhage associated with trauma, surgery, and congenital or drug-induced coagulopathies can be life-threatening and requires rapid hemostatic management via topical, intracavitary, or intravenous routes. For injuries that are not easily accessible externally, intravenous hemostatic approaches are needed. The clinical gold standard for this is transfusion of blood products, but due to donor dependence, specialized storage requirements, high risk of contamination, and short shelf life, blood product use faces significant challenges. Consequently, recent research efforts are being focused on designing biosynthetic intravenous hemostats, using intravenous nanoparticles and polymer systems. Here we report on the design and evaluation of thrombin-loaded injury-site-targeted lipid nanoparticles (t-TLNPs) that can specifically localize at an injury site via platelet-mimetic anchorage to the von Willebrand factor (vWF) and collagen and directly release thrombin via diffusion and phospholipase-triggered particle destabilization, which can locally augment fibrin generation from fibrinogen for hemostatic action. We evaluated t-TLNPs in vitro in human blood and plasma, where hemostatic defects were created by platelet depletion and anticoagulation. Spectrophotometric studies of fibrin generation, rotational thromboelastometry (ROTEM)-based studies of clot viscoelasticity, and BioFlux-based real-time imaging of fibrin generation under simulated vascular flow conditions confirmed that t-TLNPs can restore fibrin in hemostatic dysfunction settings. Finally, the in vivo feasibility of t-TLNPs was tested by prophylactic administration in a tail-clip model and emergency administration in a liver-laceration model in mice with induced hemostatic defects. Treatment with t-TLNPs was able to significantly reduce bleeding in both models. Our studies demonstrate an intravenous nanomedicine approach for injury-site-targeted direct delivery of thrombin to augment hemostasis.

Tissue factor in COVID-19-associated coagulopathy

Evidence of micro- and macro-thrombi in the arteries and veins of critically ill COVID-19 patients and in autopsies highlight the occurrence of COVID-19-associated coagulopathy (CAC). Clinical findings of critically ill COVID-19 patients point to various mechanisms for CAC; however, the definitive underlying cause is unclear. Multiple factors may contribute to the prothrombotic state in patients with COVID-19. Aberrant expression of tissue factor (TF), an initiator of the extrinsic coagulation pathway, leads to thrombotic complications during injury, inflammation, and infections. Clinical evidence suggests that TF-dependent coagulation activation likely plays a role in CAC. Multiple factors could trigger abnormal TF expression and coagulation activation in patients with severe COVID-19 infection. Proinflammatory cytokines that are highly elevated in COVID-19 (IL-1β, IL-6 and TNF-α) are known induce TF expression on leukocytes (e.g. monocytes, macrophages) and non-immune cells (e.g. endothelium, epithelium) in other conditions. Antiphospholipid antibodies, TF-positive extracellular vesicles, pattern recognition receptor (PRR) pathways and complement activation are all candidate factors that could trigger TF-dependent procoagulant activity. In addition, coagulation factors, such as thrombin, may further potentiate the induction of TF via protease-activated receptors on cells. In this systematic review, with other viral infections, we discuss potential mechanisms and cell-type-specific expressions of TF during SARS-CoV-2 infection and its role in the development of CAC.

Discovery of anti-stroke active substances in Guhong injection based on multi-phenotypic screening of zebrafish

Ischemic stroke is a leading cause of death worldwide, and it remains an urgent task to develop novel and alternative therapeutic strategies for the disease. We previously reported the positive effects of Guhong injection (GHI), composed of safflower extract and aceglutamide, in promoting functional recovery in ischemic stroke mice. However, the active substances and pharmacological mechanism of GHI is still elusive. Aiming to identify the active anti-stroke components in GHI, here we conducted a multi-phenotypic screening in zebrafish models of phenylhydrazine-induced thrombosis and ponatinib-induced cerebral ischemia. Peripheral and cerebral blood flow was quantified endogenously in erythrocytes fluorescence-labeled thrombosis fish, and baicalein and rutin were identified as major anti-thrombotic substances in GHI. Moreover, using a high-throughput video-tracking system, the effects of locomotion promotion of GHI and its main compounds were analyzed in cerebral ischemia model. Chlorogenic acid and gallic acid showed significant effects in preventing locomotor dyfunctions. Finally, GHI treatment greatly decreased the expression levels of coagulation factors F7 and F2, NF-κB and its mediated proinflammatory cytokines in the fish models. Molecular docking suggested strong affinities between baicalein and F7, and between active substances (baicalein, chlorogenic acid, gallic acid, and rutin) and NF-κB p65. In summary, our findings established a novel drug discovery method based on multi-phenotypic screening of zebrafish, provided endogenous evidences of GHI in preventing thrombus formation and promoting behavioral recovery after cerebral ischemia, and identified baicalein, rutin, chlorogenic acid, and gallic acid as active compounds in the management of ischemic stroke.

Innate immune signaling and immunothrombosis: New insights and therapeutic opportunities

Activation of the coagulation cascade is a critical, evolutionarily conserved mechanism that maintains hemostasis by rapidly forming blood clots in response to blood-borne infections and damaged blood vessels. Coagulation is a key component of innate immunity since it prevents bacterial dissemination and can provoke inflammation. The term immunothrombosis describes the process by which the innate immune response drives aberrant coagulation, which can result in a lethal condition termed disseminated intravascular coagulation, often seen in sepsis. In this review, we describe the recently uncovered molecular mechanisms underlying inflammasome- and STING-driven immunothrombosis induced by bacterial and viral infections, culminating in tissue factor (TF) activation and release. Current anticoagulant therapeutics, while effective, are associated with a life-threatening bleeding risk, requiring the urgent development of new treatments. Targeting immunothrombosis may provide a safer option. Thus, we highlight preclinical tools which target TF and/or block canonical (NLRP3) or noncanonical (caspase-11) inflammasome activation as well as STING-driven TF release and discuss clinically approved drugs which block key immunothrombotic processes and, therefore, may be redeployed as safer anticoagulants.

Befovacimab, an anti-tissue factor pathway inhibitor antibody: Early termination of the multiple-dose, dose-escalating Phase 2 study due to thrombosis

INTRODUCTION

Befovacimab (formerly BAY 1093884) is a fully human monoclonal antibody able to bind to tissue factor pathway inhibitor (TFPI) and developed as a non-replacement therapy for individuals with haemophilia A/B, with or without inhibitors.

AIM

To assess the safety of multiple escalating doses of befovacimab in individuals with severe haemophilia A/B with or without inhibitors.

METHODS

In this non-randomised, open-label Phase 2 study (NCT03597022), adult males with <1% factor VIII or <2% factor IX and ≥4 bleeds in the previous six months were enrolled in three dose cohorts (100/225/400 mg). Participants received befovacimab subcutaneously once weekly. The primary endpoint was safety; secondary endpoints included annualised bleeding rate (ABR) and pharmacokinetics/pharmacodynamics (PK/PD) of befovacimab.

RESULTS

A total of 24 participants (n = 8 in each dose cohort) were treated for 2-47 weeks. Patients treated with 100 mg and 225 mg doses of befovacimab demonstrated improved bleeding control compared with pre-study bleeding rates, with a dose-dependent effect. Dosing was suspended and the study prematurely terminated following three drug-related thrombotic serious adverse events (SAEs): two at the 225 mg dose and one at the 400 mg dose. These occurred in the absence of bleeding episodes or concomitant use of replacement/bypass therapies. No laboratory abnormalities were observed, and PK/PD data did not show correlation between SAE occurrence and levels of circulating befovacimab or free TFPI.

CONCLUSION

Despite favourable initial results from preclinical and clinical studies, a positive safety profile of befovacimab was not confirmed. The lack of SAE-related laboratory abnormalities or differentiating PK/PD characteristics in participants experiencing SAEs raises concerns about the predictability of thrombosis following befovacimab treatment and emphasises the need for further investigation into the therapeutic window of anti-TFPI treatment.

[Coagulation diagnostics in the clinical routine-Part 1 : Evaluation of the risk of bleeding before surgery, interventions and diagnostics in bleeding diathesis]

This article on coagulation diagnostics is published in two parts covering five common clinical scenarios for coagulation diagnostics. Part 1 deals with the diagnostics prior to invasive interventions and coagulation diagnostics to clarify a tendency to bleeding. The global parameters Quick and activated partial thromboplastin time are established for monitoring certain anticoagulants; however, they are not predictive with respect to the risk of bleeding prior to elective invasive interventions. In this context, disorders of primary hemostasis are frequent, which are insufficiently detected by the global parameters. Most clinical bleeding tendencies are due to acquired causes. These include anticoagulants and diseases which can be accompanied by tendency to bleeding. For coagulation tests preanalytical issues are essential in order to avoid false results. The interpretation should always be made in the context of the current physiological state.

The role of thrombin in haemostasis

Thrombin is a multifunctional serine protease generated in injured cells. The generation of thrombin in coagulation plays a central role in the functioning of haemostasis. The last enzyme in the coagulation cascade is thrombin, with the function of cleaving fibrinogen to fibrin, which forms the fibrin clot of a haemostatic plug. Although thrombin primarily converts fibrinogen to fibrin, it also has many other positive regulatory effects on coagulation. Thrombin has procoagulant, inflammatory, cellular proliferation and anticoagulant effects. In coagulation system, thrombin has two very distinct roles. Firstly, it acts as a procoagulant when it converts fibrinogen into an insoluble fibrin clot, activates factor (F) XIII, activates thrombin activatable fibrinolysis inhibitor (TAFI) and activates FV, FVIII and FXI. Thrombin also enhances platelet adhesion by inactivating a disintegrin and metalloprotease with thrombospondin type1 motif (ADAMTS13). However, when thrombin activates protein C, it acts as an anticoagulant. A natural anticoagulant pathway that supplies regulation of the blood coagulation system contains protein C, which is the key component. This is accomplished by the specific proteolytic inactivation of FV and FVIII. In this review, the multiple roles of thrombin in the haemostatic response to injury are studied in addition to the cofactors that determine thrombin activity and how thrombin activity is thought to be coordinated.

The role of procoagulant phospholipids on the surface of circulating blood cells in thrombosis and haemostasis

Phospholipids (PLs) are found in all cell types and are required for structural support and cell activation signalling pathways. In resting cells, PLs are asymmetrically distributed throughout the plasma membrane with native procoagulant aminophospholipids (aPLs) being actively maintained in the inner leaflet of the membrane. Upon platelet activation, aPLs rapidly externalize to the outer leaflet and are essential for supporting the coagulation cascade by providing binding sites for factors in the cell-based model. More recent work has uncovered a role for enzymatically oxidized PLs (eoxPLs) in facilitating coagulation, working in concert with native aPLs. Despite this, the role of aPLs and eoxPLs in thrombo-inflammatory conditions, such as arterial and venous thrombosis, has not been fully elucidated. In this review, we describe the biochemical structures, distribution and regulation of aPL externalization and summarize the literature on eoxPL generation in circulating blood cells. We focus on the currently understood role of these lipids in mediating coagulation reactions in vitro, in vivo and in human thrombotic disease. Finally, we highlight gaps in our understanding in how these lipids vary in health and disease, which may place them as future therapeutic targets for the management of thrombo-inflammatory conditions.

Immunothrombosis and the molecular control of tissue factor by pyroptosis: prospects for new anticoagulants

The interplay between innate immunity and coagulation after infection or injury, termed immunothrombosis, is the primary cause of disseminated intravascular coagulation (DIC), a condition that occurs in sepsis. Thrombosis associated with DIC is the leading cause of death worldwide. Interest in immunothrombosis has grown because of COVID-19, the respiratory disease caused by SARS-CoV-2, which has been termed a syndrome of dysregulated immunothrombosis. As the relatively new field of immunothrombosis expands at a rapid pace, the focus of academic and pharmacological research has shifted from generating treatments targeted at the traditional 'waterfall' model of coagulation to therapies better directed towards immune components that drive coagulopathies. Immunothrombosis can be initiated in macrophages by cleavage of the non-canonical inflammasome which contains caspase-11. This leads to release of tissue factor (TF), a membrane glycoprotein receptor that forms a high-affinity complex with coagulation factor VII/VIIa to proteolytically activate factors IX to IXa and X to Xa, generating thrombin and leading to fibrin formation and platelet activation. The mechanism involves the post-translational activation of TF, termed decryption, and release of decrypted TF via caspase-11-mediated pyroptosis. During aberrant immunothrombosis, decryption of TF leads to thromboinflammation, sepsis, and DIC. Therefore, developing therapies to target pyroptosis have emerged as an attractive concept to counteract dysregulated immunothrombosis. In this review, we detail the three mechanisms of TF control: concurrent induction of TF, caspase-11, and NLRP3 (signal 1); TF decryption, which increases its procoagulant activity (signal 2); and accelerated release of TF into the intravascular space via pyroptosis (signal 3). In this way, decryption of TF is analogous to the two signals of NLRP3 inflammasome activation, whereby induction of pro-IL-1β and NLRP3 (signal 1) is followed by activation of NLRP3 (signal 2). We describe in detail TF decryption, which involves pathogen-induced alterations in the composition of the plasma membrane and modification of key cysteines on TF, particularly at the location of the critical, allosterically regulated disulfide bond of TF in its 219-residue extracellular domain. In addition, we speculate towards the importance of identifying new therapeutics to block immunothrombotic triggering of TF, which can involve inhibition of pyroptosis to limit TF release, or the direct targeting of TF decryption using cysteine-modifying therapeutics.

Acute myocardial injury in patients with COVID-19: Possible mechanisms and clinical implications

Severe acute respiratory syndrome coronavirus 2 infection affects not only the lungs, but also the cardiovascular system, having a major impact on patients' outcomes. Myocardial injury (MI) occurs in the context of coronavirus infectious disease 2019 (COVID-19) and is associated with a higher risk of severe clinical outcome and mortality. COVID-19-related MI can have various clinical manifestations, of which the main ones are myocarditis, stress cardiomyopathy, acute coronary syndrome, and pulmonary embolism. The exact mechanisms of how MI occurs in these patients are not yet fully known. Direct injury, through direct viral myocardial invasion, and indirect injury, through interaction with angiotensin I converting enzyme 2, increased inflammation, and thrombocyte and endothelial dysfunction, could be involved in acute MI in patients with COVID-19. A better understanding of these multiple potential mechanisms may help to develop new targeted therapeutic strategies. The purpose of this review is to provide the current understanding of the potential mechanisms involved in MI induced by COVID-19 and to discuss the current progress in the therapeutic strategies.

Protective Effect of Rivaroxaban Against Amyloid Pathology and Neuroinflammation Through Inhibiting PAR-1 and PAR-2 in Alzheimer's Disease Mice

BACKGROUND

Recent studies have revealed that atrial fibrillation (AF) patients have a high risk of developing cognitive impairment, vascular dementia, and Alzheimer's disease (AD). Some reports suggest that the application of oral anticoagulant with an appropriate dose may have a preventive effect on AD. However, which oral anticoagulant drug is more appropriate for preventing AD and the underlying mechanism(s) is still unknown.

OBJECTIVE

The aim of the present study was to assess the treatment effect of rivaroxaban administration as well as investigate the roles of PAR-1 and PAR-2 in the AD + CAA mice model.

METHODS

In the present study, we compared a traditional oral anticoagulant, warfarin, and a direct oral anticoagulant (DOAC), rivaroxaban, via long-term administration to an AD with cerebral amyloid angiopathy (CAA) mice model.

RESULTS

Rivaroxaban treatment attenuated neuroinflammation, blood-brain barrier dysfunction, memory deficits, and amyloid-β deposition through PAR-1/PAR-2 inhibition in the AD + CAA mice model compared with warfarin and no-treatment groups.

CONCLUSION

The present study demonstrates that rivaroxaban can attenuate AD progress and can be a potential choice to prevent AD.

Aberrant stromal tissue factor localisation and mycolactone-driven vascular dysfunction, exacerbated by IL-1β, are linked to fibrin formation in Buruli ulcer lesions

Buruli ulcer (BU) is a neglected tropical disease caused by subcutaneous infection with Mycobacterium ulcerans and its exotoxin mycolactone. BU displays coagulative necrosis and widespread fibrin deposition in affected skin tissues. Despite this, the role of the vasculature in BU pathogenesis remains almost completely unexplored. We hypothesise that fibrin-driven ischemia can be an ‘indirect’ route to mycolactone-dependent tissue necrosis by a mechanism involving vascular dysfunction. Here, we tracked >900 vessels within contiguous tissue sections from eight BU patient biopsies. Our aim was to evaluate their vascular and coagulation biomarker phenotype and explore potential links to fibrin deposition. We also integrated this with our understanding of mycolactone’s mechanism of action at Sec61 and its impact on proteins involved in maintaining normal vascular function. Our findings showed that endothelial cell dysfunction is common in skin tissue adjacent to necrotic regions. There was little evidence of primary haemostasis, perhaps due to mycolactone-dependent depletion of endothelial von Willebrand factor. Instead, fibrin staining appeared to be linked to the extrinsic pathway activator, tissue factor (TF). There was significantly greater than expected fibrin staining around vessels that had TF staining within the stroma, and this correlated with the distance it extended from the vessel basement membrane. TF-induced fibrin deposition in these locations would require plasma proteins outside of vessels, therefore we investigated whether mycolactone could increase vascular permeability in vitro. This was indeed the case, and leakage was further exacerbated by IL-1β. Mycolactone caused the loss of endothelial adherens and tight junctions by the depletion of VE-cadherin, TIE-1, TIE-2 and JAM-C; all Sec61-dependent proteins. Taken together, our findings suggest that both vascular and lymphatic vessels in BU lesions become “leaky” during infection, due to the unique action of mycolactone, allowing TF-containing structures and plasma proteins into skin tissue, ultimately leading to local coagulopathy and tissue ischemia.

To date, the debilitating skin disease Buruli ulcer remains a public health concern and financial burden in low or middle-income countries, especially in tropical regions. Late diagnosis is frequent in remote areas, perhaps due to the painlessness of the disease. Hence patients often present with large, destructive opened ulcers leading to delayed wound closure or even lifelong disability. The infectious agent produces a toxin called mycolactone that drives the disease. We previously found evidence that the vascular system is disrupted by mycolactone in these lesions, and now we have further explored potential explanations for these findings by looking at the expression of vascular markers in BU. In a detailed analysis of patient skin punch biopsies, we identified distinct expression patterns of certain proteins and found that tissue factor, which initiates the so-called extrinsic pathway of blood clotting, is particularly important. Mycolactone is able to disrupt the barrier function of the endothelium, further aggravating the diseased phenotype, which may explain how clotting factors access the tissue. Altogether, such localised hypercoagulation in Buruli ulcer skin lesions may contribute to the development of the lesion.

Differentiation of malignant from non-malignant portal vein thrombosis in liver cirrhosis: the challenging dilemma

Background

PVT is an ultrasonographic finding in up to 8% of patients with liver cirrhosis. Once hepatocellular carcinoma has occurred as the final station in liver cirrhosis, the risk of PVT rises to 40%. Benign and malignant PVT can occur in patients with liver cirrhosis, and it is important to differentiate the nature of PVT as it has a great impact on patient’s management and outcome.

Diagnosis

Confirming portal vein thrombosis and extension by abdominal ultrasound, contrast-enhanced USG, CT, or MRI. Malignant criteria of PVT are pulsatile pattern in Doppler and heterogeneous contrast enhancement, which are especially seen at the arterial phase, neovascularity within PVT, portal vein thrombus with a diameter of > 23 mm while in benign thrombus, PV diameter does not exceed 20 mm. Visible hypervascular tumor is in close proximity to PVT.

Conclusion

It is not uncommon to find portal vein thrombosis in patients with liver cirrhosis, despite the fact that malignant variant is the most frequent, but efforts should be gathered to exclude benign PVT which may change the management of the patients dramatically.

Antibody drug conjugates in gastrointestinal cancer: From lab to clinical development

The antibody-drug conjugates (ADCs) are one the fastest growing biotherapeutics in oncology and are still in their infancy in gastrointestinal (GI) cancer for clinical applications to improve patient survival. The ADC based approach is developed with tumor specific antigen, antibody carrying cytotoxic agents to precisely target and deliver chemotherapeutics at the tumor site. To date, 11 ADCs have been approved by US-FDA, and more than 80 are in the clinical development phase for different oncological indications. However, The ADCs based therapies in GI cancers are still far from having high-efficient clinical outcomes. The limited success of these ADCs and lessons learned from the past are now being used to develop a newer generation of ADC against GI cancers. In this review, we did a comprehensive assessment of the key components of ADCs, including tumor marker, antibody, cytotoxic payload, and linkage strategy, with a focus on technical improvement and some future trends in the pipeline for clinical translation. The various preclinical and clinical ADCs used in gastrointestinal malignancies, their target, composition and bioconjugation, along with preclinical and clinical outcomes, are discussed. The emphasis is also given to new generation ADCs employing novel mAb, payload, linker, and bioconjugation methods are also included.

Modified Protocol to Enable the Study of Hemorrhage and Hematoma in a Traumatic Brain Injury Mouse Model

To date, many studies using the controlled cortical impact (CCI) mouse model of traumatic brain injury (TBI) have presented results without presenting the pathophysiology of the injury-core itself or the temporal features of hemorrhage (Hrr). This might be owing to the removal of the injury-core during the histological procedure. We therefore developed a modified protocol to preserve the injury-core. The heads of mice were obtained after perfusion and were post-fixed. The brains were then harvested, retaining the ipsilateral skull bone; these were post-fixed again and sliced using a cryocut. To validate the utility of the procedure, the temporal pattern of Hrr depending on the impacting depth was analyzed. CCI-TBI was induced at the following depths: 1.5 mm (mild Hrr), 2.5 mm (moderate Hrr), and 3.5 mm (severe Hrr). A pharmacological study was also conducted using hemodynamic agents such as warfarin (2 mg/kg) and coagulation factor VIIa (Coa-VIIa, 1 mg/kg). The current protocol enabled the visual observation of the Hrr until 7 days. Hrr peaked at 1–3 days and then decreased to the normal range on the seventh day. It expanded from the affected cortex (mild) to the periphery of the hippocampus (moderate) and the brain ventricle (severe). Pharmacological studies showed that warfarin pre-treatment produced a massively increased Hrr, concurrent with the highest mortality rate and brain injury. Coa-VIIa reduced the side effects of warfarin. Therefore, these results suggest that the current method might be suitable to conduct studies on hemorrhage, hematoma, and the injury-core in experiments using the CCI-TBI mouse model.

Changes in Maternal Platelet Physiology during Gestation and Their Interaction with Trophoblasts

Upon activation, maternal platelets provide a source of proinflammatory mediators in the intervillous space of the placenta. Therefore, platelet-derived factors may interfere with different trophoblast subtypes of the developing human placenta and might cause altered hormone secretion and placental dysfunction later on in pregnancy. Increased platelet activation, and the subsequent occurrence of placental fibrinoid deposition, are linked to placenta pathologies such as preeclampsia. The composition and release of platelet-derived factors change over gestation and provide a potential source of predicting biomarkers for the developing fetus and the mother. This review indicates possible mechanisms of platelet-trophoblast interactions and discusses the effect of increased platelet activation on placenta development.

SARS-CoV-2 and Plasma Hypercoagulability

Hypercoagulability has emerged as a prominent consequence of COVID-19. This presents challenges not only in the clinic, but also in thrombosis research. Health and safety considerations, the status of the blood and plasma supply, the infection status of individual donors, and the mechanisms by which SARS-CoV-2 activates coagulation are all of concern. In this review, we discuss these topics from the basic research perspective. As in other respiratory illnesses, blood and plasma from COVID-19 positive patients carries minimal to no risk of infection to practitioners or researchers. There are currently no special regulatory mandates directing individual donors (for research purposes), blood centers/services or vendors (for blood products for research) to test blood/plasma for SARS-CoV-2 or antibodies. We discuss current theories about how SARS-CoV-2 leads to hyper-coagulant state in severe cases of COVID-19. Our current understanding of the mechanisms behind COVID-19 associated thromboembolic events have centered around three different pathways: (1) direct activation of platelets, enhancing coagulation; (2) direct infection and indirect activation (e.g. cytokine storm) of endothelial cells by SARS-CoV-2, shifting endothelium from an anti-thrombotic to a pro-thrombotic state; and (3) direct activation of complement pathways, promoting thrombin generation. Further investigation on how SARS-CoV-2 affects thrombosis in COVID-19 patients may bring novel anti-thrombotic therapies to combat the disease.

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

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

Vitamin K antagonist use induces calcification and atherosclerotic plaque progression resulting in increased hypercoagulability

Aims

Vascular calcification is a hallmark of atherosclerotic burden and can predict the cardiovascular outcome. Vitamin K antagonists (VKA) are widely used anticoagulant drugs to treat patients at risk of arterial and venous thrombosis but are also associated with increase vascular calcification progression. We aim to unravel the paradox that VKA suppresses plasma coagulation but promotes vascular calcification and subsequent atherosclerosis-dependent coagulability of the vessel wall.

Methods and results

Apoe^−/− mice were placed on western-type diet enriched with the VKA warfarin for 18 weeks to measure atherosclerotic plaque burden, calcification, and coagulation. Patients (n = 54) displaying paroxysmal atrial fibrillation with a low cardiovascular risk, who were treated with VKA were included to measure pre-thrombotic state. Finally, primary vascular smooth muscle cells (VSMC) derived from human tissue explants were used for in vitro experiments. In Apoe^−/− mice, VKA increases both atherosclerotic plaque size and calcification. Higher plaque calcification was associated with increased plasma levels of thrombin-antithrombin and factor IXa-antithrombin complexes in mice and patients treated with VKA. Mechanistically, phenotypic switching of VSMC into synthetic VSMC promotes thrombin generation, which is enhanced in a tissue-factor (TF)-dependent manner by VSMC calcification. Moreover, calcified VSMC exposed to whole blood under flow significantly enhanced platelet deposition and TF-dependent fibrin formation.

Conclusions

Oral anticoagulation with VKA aggravates vascular calcification and atherosclerosis. VSMC phenotype differentiation impacts coagulation potential in a TF-dependent manner. VKA-induced vascular calcification increases hypercoagulability and could thereby potentially positively affect atherothrombosis.

Vitamin K - sources, physiological role, kinetics, deficiency, detection, therapeutic use, and toxicity

Vitamin K is traditionally connected with blood coagulation, since it is needed for the posttranslational modification of 7 proteins involved in this cascade. However, it is also involved in the maturation of another 11 or 12 proteins that play different roles, encompassing in particular the modulation of the calcification of connective tissues. Since this process is physiologically needed in bones, but is pathological in arteries, a great deal of research has been devoted to finding a possible link between vitamin K and the prevention of osteoporosis and cardiovascular diseases. Unfortunately, the current knowledge does not allow us to make a decisive conclusion about such a link. One possible explanation for this is the diversity of the biological activity of vitamin K, which is not a single compound but a general term covering natural plant and animal forms of vitamin K (K₁ and K₂) as well as their synthetic congeners (K₃ and K₄). Vitamin K₁ (phylloquinone) is found in several vegetables. Menaquinones (MK₄–MK₁₃, a series of compounds known as vitamin K₂) are mostly of a bacterial origin and are introduced into the human diet mainly through fermented cheeses. Current knowledge about the kinetics of different forms of vitamin K, their detection, and their toxicity are discussed in this review.

Hemostatic parameters in patients with spinal cord injury in subacute and chronic phase of the rehabilitation

Objective: The goal of this study was to measure hemostatic markers after SCI.Design: Assesing changes in coagulation and fibrynilitic system in SCI patients in different time post injury to Cross-sectional study.Setting: Rehabilitation Department of the Bydgoszcz University Hospital, Poland from 2011 to 2017.Participants: SCI patient during acute and chronic rehabilitation (N = 88).Outcome Measures: Assesing following parameters: platelet counts and levels of D-dimer, antithrombin III (ATIII), tissue factor (TF), tissue factor pathway inhibitor (TFPI) and the inflammatory marker, C-reactive protein (CRP).Interventions: Eighty-eight SCI patients were divided into three groups based on the time elapsed from injury: group I (three weeks to three months), group II (three to twelve months) and group III (more than twelve months). All patients underwent ultrasonography (US) to detect acute or chronic recanalized deep vein thrombosis (DVT). Platelet counts and levels of D-dimer, ATIII, TF, TFPI and CRP were assessed. TF and TFPI levels were measured in the control group of forty healthy individuals without SCI, the rest of the parameters were compared to laboratory norms.Results: D-dimer levels were significantly higher in group I compared to group II (P = .0002) and group III (P < .001). Group II had higher D-dimer levels than group III (P = .032). TFPI levels were higher in group II compared with group III (P = .0041) and control group (P = .000033). TF was significantly higher in all the SCI groups compared with the control group (P < .001).Conclusions: D-dimer and TF levels were still elevated twelve months after SCI. TF levels were also elevated over 12 months after inury. The results may indicate that sub-acute and even chronic SCI patients have disturbed coagulation and fibrynolitic system.

Extrahepatic portal vein thrombosis in a pregnant patient with COVID-19: a rare thrombotic event survivor

A COVID-19 infection predisposes the infected person to thrombotic events. Myocardial infarction, acute limb ischaemia, mesenteric artery thrombosis and pulmonary embolism are all well-documented complications of this infection. Here we describe a pregnant patient who presented with obstructed labour with asymptomatic COVID-19 infection and developed ascites during the postoperative period. Further work-up of the patient revealed portal hypertension due to portal vein thrombosis (PVT). As the patient was healthy before this index pregnancy, a causative link between COVID-19 and PVT cannot be ruled out. Her COVID-19 infection progressed to a moderate disease. She was managed with steroids and appropriate antibiotics for secondary bacterial peritonitis. She was finally discharged after 2.5 months of multidisciplinary treatment. This is a case of a survivor of complications due to pregnancy, COVID-19 and extrahepatic portal vein obstruction.

Critical traumatic brain injury is associated with worse coagulopathy

OBJECTIVES

As thromboelastography (TEG) becomes the standard of care in patients with hemorrhagic shock (HS), an association between concomitant traumatic brain injury (TBI) and coagulopathy by TEG parameters is not well understood and is thus investigated.

METHODS

Retrospective analysis of trauma registry data at a single level 1 trauma center of 772 patients admitted with head Abbreviated Injury Scale (AIS) score of 3 and TEG studies between 2014 and 2017. Patients were stratified to moderate-severe TBI by head AIS scores of 3 and 4 (435 patients) and critical TBI by head AIS score of 5 (328 patients). Hemorrhagic shock was defined by base deficit of 4 or shock index of 0.9. Statistical analysis with unpaired t tests compared patients with critical TBI with patients with moderate-severe TBI, and patients were grouped by presence or absence of HS. A comparison of TBI data with conventional coagulation studies was also evaluated.

RESULTS

In the setting of HS, critical TBI versus moderate-severe TBI was associated with longer R time (p = 0.004), longer K time (p < 0.05), less acute angle (p = 0.001), and lower clot strength and stability (maximum amplitude [MA]) (p = 0.01). Worse TBI did not correlate with increased fibrinolysis by clot lysis measured by the percentage decrease in amplitude at 30 minutes after MA (p = 0.3). Prothrombin time and international normalized ratio failed to demonstrate more severe coagulopathy, while partial thromboplastin time was found to correlate with severity of TBI (p = 0.01). In patients with critical TBI, the presence of HS correlated with a statistically significant worsening of all parameters (p < 0.05) except for clot lysis measured by the percentage decrease in amplitude at 30 minutes after MA (LY-30).

CONCLUSION

Thromboelastography demonstrates that, with and without hemorrhagic shock, critical TBI correlates with a significant worsening of traumatic coagulopathy in comparison with moderate/severe TBI. In HS, critical TBI correlates with impaired clot initiation, impaired clot kinetics, and impaired platelet-associated clot strength and stability versus parameters found in moderate-severe TBI. Hemorrhagic shock correlates with worse traumatic coagulopathy in all evaluated patient groups with TBI. Conventional coagulation studies underestimate TBI-associated coagulopathy. Traumatic brain injury-associated coagulopathy is not associated with fibrinolysis.

LEVEL OF EVIDENCE

Prognostic/epidemiological, level IV; prognostic/epidemiological, level III.

Effects of rivaroxaban and warfarin on the risk of gastrointestinal bleeding and intracranial hemorrhage in patients with atrial fibrillation: Systematic review and meta-analysis

To assess the risk of gastrointestinal bleeding and intracranial hemorrhage in patients with atrial fibrillation (AF) after the use of rivaroxaban or warfarin. To investigate the effects of rivaroxaban and warfarin on gastrointestinal and intracranial hemorrhage in patients with AF, we searched PubMed, Embase, and Medline from the establishment of databases up to 2020. We finally included 38 observational studies involving 1 312 609 patients for the assessment of intracranial hemorrhage, and 33 observational studies involving 1 332 956 patients for the assessment of gastrointestinal bleeding. The rates of intracranial hemorrhage were 0.55% in the rivaroxaban group versus 0.91% in the warfarin group (OR 0.59; 95% CI 0.53-0.66; p < .00001, I2 = 78%). The rates of gastrointestinal bleeding were 2.63% in patients with rivaroxaban versus 2.48% in those with warfarin (OR 1.06; 95% CI 0.96-1.17; p < .00001, I2 = 94%). Rivaroxaban could significantly reduce the risk of intracranial hemorrhage in patients with AF than warfarin, but the risk of gastrointestinal bleeding remained controversy due to no statistical significant difference. Notably, a subgroup analysis demonstrated that patients in rivaroxaban group with severe chronic renal diseases or undergoing hemodialysis exposed to less gastrointestinal hemorrhage risk than the group from warfarin.

T-Cell Molecular Modulation Responses in Atherosclerosis Anergy

Atherosclerosis continues to be a major cause of death in patients with cardiovascular diseases. The cooperative role of immunity has been recently considered in atherosclerotic plaque inflammation, especially adaptive immune response by T cells. In this review, we examine the possible role of T cells in atherosclerosis-mediated inflammation and conceivable therapeutic strategies that can ameliorate complications of atherosclerosis. The cytokines secreted by T-lymphocyte subsets, different pathophysiological profiles of microRNAs (miRs), and the growth factor/receptor axis have diverse effects on the inflammatory cycle of atherosclerosis. Manipulation of miRNA expression and prominent growth factor receptors involved in inflammatory cytokine secretion in atherosclerosis can be considered diagnostic biomarkers in the induction of anergy and blockade of atherosclerotic development. This manuscript reviews immunomodulation of T cells responses in atherosclerosis anergy.

The Efficacy and Safety of Tranexamic Acid Treatment in Orthopaedic Trauma Surgery

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Tranexamic acid (TXA) is a drug used to control hemorrhage by preventing the breakdown of fibrin.

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TXA is a cost-effective treatment for trauma patients across a variety of economic settings.

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Concerns of TXA causing thromboembolic events (TEEs) in orthopaedic trauma patients are not supported by evidence.

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TXA has been shown to reduce blood loss in hip fracture surgery.

Early Coagulopathy in Pediatric Traumatic Brain Injury: A Pediatric Acute and Critical Care Medicine Asian Network (PACCMAN) Retrospective Study

BACKGROUND

Although early coagulopathy increases mortality in adults with traumatic brain injury (TBI), less is known about pediatric TBI.

OBJECTIVE

To describe the prothrombin time (PT), activated partial thromboplastin time (APTT), and platelet levels of children with moderate to severe TBI to identify predictors of early coagulopathy and study the association with clinical outcomes.

METHODS

Using the Pediatric Acute and Critical Care Medicine Asian Network (PACCMAN) TBI retrospective cohort, we identified patients <16 yr old with a Glasgow Coma Scale (GCS) ≤13. We compared PT, APTT, platelets, and outcomes between children with isolated TBI and multiple trauma with TBI. We performed logistic regressions to identify predictors of early coagulopathy and study the association with mortality and poor functional outcomes.

RESULTS

Among 370 children analyzed, 53/370 (14.3%) died and 127/370 (34.3%) had poor functional outcomes. PT was commonly deranged in both isolated TBI (53/173, 30.6%) and multiple trauma (101/197, 51.3%). Predictors for early coagulopathy were young age (adjusted odds ratio [aOR] 0.94, 95% CI 0.88-0.99, P = .023), GCS < 8 (aOR 1.96, 95% CI 1.26-3.06, P = .003), and presence of multiple trauma (aOR 2.21, 95% confidence interval [CI] 1.37-3.60, P = .001). After adjusting for age, gender, GCS, multiple traumas, and presence of intracranial bleed, children with early coagulopathy were more likely to die (aOR 7.56, 95% CI 3.04-23.06, P < .001) and have poor functional outcomes (aOR 2.16, 95% CI 1.26-3.76, P = .006).

CONCLUSION

Early coagulopathy is common and independently associated with death and poor functional outcomes among children with TBI.

Molecular Characterization of Two Homozygous Factor VII Variants Associated with Intracranial Bleeding

Clinical parameters have been extensively studied in factor (F) VII deficiency, but the knowledge of molecular mechanisms of this disease is scarce. We report on three probands with intracranial bleeds at an early age, one of which had concomitant high titer of FVII inhibitor. The aim of the present study was to identify the causative mutations and to elucidate the underlying molecular mechanisms. All nine F7 exons were sequenced in the probands and the closest family members. A homozygous deletion in exon 1, leading to a frame shift and generation of a premature stop codon (p.C10Pfs*16), was found in proband 1. Probands 2 and 3 (siblings) were homozygous for a missense mutation in exon 8, resulting in a glycine (G) to arginine (R) substitution at amino acid 240 (p.G240R). All probands had severely reduced FVII activity (FVII:C < 1 IU/dL). Treatment consisted of recombinant FVIIa and/or plasma concentrate, and proband 1 developed a FVII inhibitor shortly after initiation of treatment. The FVII variants were overexpressed in mammalian cell lines. No FVII protein was produced in cells expressing the p.C10Pfs*16 variant, and the inhibitor development in proband 1 was likely linked to the complete absence of circulating FVII. Structural analysis suggested that the G to R substitution in FVII found in probands 2 and 3 would destabilize the protein structure, and cell studies demonstrated a defective intracellular transport and increased endoplasmic reticulum stress. The molecular mechanism underlying the p.G240R variant could be reduced secretion caused by protein destabilization and misfolding.

Potent Trivalent Inhibitors of Thrombin through Hybridization of Salivary Sulfopeptides from Hematophagous Arthropods

Blood feeding arthropods, such as leeches, ticks, flies and mosquitoes, provide a privileged source of peptidic anticoagulant molecules. These primarily operate through inhibition of the central coagulation protease thrombin by binding to the active site and either exosite I or exosite II. Herein, we describe the rational design of a novel class of trivalent thrombin inhibitors that simultaneously block both exosites as well as the active site. These engineered hybrids were synthesized using tandem diselenide-selenoester ligation (DSL) and native chemical ligation (NCL) reactions in one-pot. The most potent trivalent inhibitors possessed femtomolar inhibition constants against α-thrombin and were selective over related coagulation proteases. A lead hybrid inhibitor possessed potent anticoagulant activity, blockade of both thrombin generation and platelet aggregation in vitro and efficacy in a murine thrombosis model at 1 mg kg-1 . The rational engineering approach described here lays the foundation for the development of potent and selective inhibitors for a range of other enzymatic targets that possess multiple sites for the disruption of protein-protein interactions, in addition to an active site.

Plasmatic and cell-based enhancement by microparticles originated from platelets and endothelial cells under simulated in vitro conditions of a dilutional coagulopathy

BACKGROUND

Aggressive fluid management and other external factors may lead to hypothermia, acidosis and hemodilution (defined as Lethal Triad, LT) contributing to a trauma-induced coagulopathy (TIC) that worsens patients' outcomes. Procoagulant microparticles (MP) are crucial players at the interface of cellular and plasmatic coagulation. However, their functions remain largely unexplored. This study aimed to characterize effects of MP subtypes and concentrations on functional coagulation under in vitro simulated conditions.

METHODS

Blood from eleven volunteers were collected to simulate in vitro conditions of hemodilution (HD) and LT, respectively. HD was induced by replacing a blood volume of 33% by crystalloids and for LT, samples were further processed by reducing the temperature to 32 °C and lowering the pH to 6.8. MP were obtained either from platelet concentrates (platelet-derived MP, PDMP) or from cell culture (ECV304 cells for endothelial-derived MP, EDMP) by targeted stimulation. After introducing MP to in vitro conditions, we measured their concentration-dependent effects (1.000, 10.000 and 15.000 MP/μl blood) on coagulation compared to whole blood (WB). For each condition, coagulation was characterized by flow cytometric platelet activation and by quantification of fibrin clot propagation using Thrombodynamics® technology.

RESULTS

MP originated from platelets and endothelial cells affected blood coagulation in a concentration-dependent manner. Particularly, high PDMP quantities (10.000 and 15.000 PDMP/μl blood) significantly induced platelet activation and fibrin clot growth and size in HD conditions. In LT conditions as well, only high PDMP concentration induced platelet activation, clot growth and size. In contrast, EDMP did not induce platelet activation, but resulted in enhanced formation of spontaneous clots, irrespective of simulated condition. With increasing EDMP concentration, the time until the onset of spontaneous clotting decreased in both HD and LT conditions.

DISCUSSION

The study demonstrates an essential role of MP within the coagulation process under simulated coagulopathic conditions. PDMP affected platelets promoting clot formation likely by providing a surface enlargement. EDMP presumably affected clotting factors of the plasmatic coagulation resulting in an increased formation of spontaneous clots.

CONCLUSION

Under simulated conditions of a dilutional coagulopathy, MP from different cellular origin indicate a divergent but both procoagulant mechanism within the coagulation process.

Surface modification of polyurethane with eptifibatide-loaded degradable nanoparticles reducing risk of blood coagulation

The main purpose of the work was to develop a drug releasing coatings on the surface of medical devices exposed to blood flow, what should enable effective inhibition of blood coagulation process. As a part of the work, the process of encapsulating the anticoagulant drug eptifibatide (EPT) in poly(DL-lactic-co-glycolic acid) (PLGA) nanoparticles was developed. EPT encapsulation efficiency was 29.1 ± 2.1%, while the EPT loading percentage in the nanoparticles was 4.2 ± 0.3%. The PLGA nanoparticles were suspended in a polyanion solution (hyaluronic acid (HA)) and deposited on the surface-treated thermoplastic polyurethane (TPU) by a layer-by-layer method. As a polycation poly-L-lysine (PLL) was used. The influence of released EPT on the activation of the coagulation system was analyzed using dynamic blood tester. Performed experiments show an effective delivery of the drug to the bloodstream and low risk of platelets (membrane receptor) activation. The dynamic blood test process, including its physical phenomenon, was described using numerical methods, i.e. a finite volume cone-and-plate test model as well as non-Newtonian blood models. The values of shear stress and blood flow velocity under the fast-rotating cone were computed applying boundary conditions of cylinder wall imitating blood-nanomaterial interaction. Implementing boundary conditions as initial shear stress values of bottom cylinder wall resulted in the increase of shear stress in blood under rotating cone. The developed system combining drug eluting polymeric nanoparticles with the polyelectrolyte "layer-by-layer" coating can be easily introduced to medical implants of various shape, with the advantages of resorbable drug carriers allowing for local and controllable delivery of anti-thrombogenic drugs.