Coagulation history, Oxford 1951-53

Fibrinogen: Structure, abnormalities and laboratory assays

Fibrinogen is the primary precursor protein for the fibrin clot, which is the final target of blood clotting. It is also an acute phase reactant that can vary under physiologic and inflammatory conditions. Disorders in fibrinogen concentration and/or function have been variably linked to the risk of bleeding and/or thrombosis. Fibrinogen assays are commonly used in the management of bleeding as well as the treatment of thrombosis. This chapter examines the structure of fibrinogen, its role in hemostasis as well as in bleeding abnormalities and measurement thereof with respect to clinical management.

Russell Viper Venom: A Journey from the Bedside to the Bench and Back to the Bedside

Russell Viper Venom (RVV) is widely used as a diagnostic test for antiphospholipid syndrome (APS). But the history of how this venom came to be discovered is well known. Dr Patrick Russell is responsible for the identification of the venom during his work on snake bites in India while Dr Robert Macfarlane used it to staunch bleeding in persons with haemophilia. The ability to directly activate factor X led RVV to the laboratory diagnosis of APS. More recently, it has come back to clinical world with a potential for an engineered factor X activator from RVV to be used in the treatment of haemophilia.

The History of Factor XIII Deficiency

Despite the early discovery of factor XIII (FXIII) in 1944, the diagnosis of FXIII deficiency was not made until 1960, after all the other coagulation factor deficiencies, most likely due to the normality of routine coagulation testing in FXIII deficiency. Although the first case was detected by the clot solubility test and this test has long since been used to detect FXIII deficiency, the test is no longer recommended by experts. Over the past 60 years, knowledge about FXIII deficiency has expanded considerably, between 1992, when the first variant was identified, and 2022, 197 mutations have been reported. Almost all missense mutations have a similar effect on FXIII, leading to instability and faster degradation of mutant FXIII protein. Therapeutic options have evolved from historical fresh frozen plasma (FFP), old plasma, whole blood, and cryoprecipitate, to plasma-derived and recombinant FXIII concentrates, respectively available since 1993 and 2012. These concentrate products were respectively approved by the Food and Drug Administration in 2011 and 2013. This historical review covers various aspects of FXIII related disorders, including the discovery of the FXIII, associated disorders, molecular basis, diagnosis, and treatment of FXIII deficiency.

Pathophysiology of Coagulation and Emerging Roles for Extracellular Vesicles in Coagulation Cascades and Disorders

The notion of blood coagulation dates back to the ancient Greek civilization. However, the emergence of innovative scientific discoveries that started in the seventeenth century formulated the fundamentals of blood coagulation. Our understanding of key coagulation processes continues to evolve, as novel homeostatic and pathophysiological aspects of hemostasis are revealed. Hemostasis is a dynamic physiological process, which stops bleeding at the site of injury while maintaining normal blood flow within the body. Intrinsic and extrinsic coagulation pathways culminate in the homeostatic cessation of blood loss, through the sequential activation of the coagulation factors. Recently, the cell-based theory, which combines these two pathways, along with newly discovered mechanisms, emerged to holistically describe intricate in vivo coagulation mechanisms. The complexity of these mechanisms becomes evident in coagulation diseases such as hemophilia, Von Willebrand disease, thrombophilia, and vitamin K deficiency, in which excessive bleeding, thrombosis, or unnecessary clotting, drive the development and progression of diseases. Accumulating evidence implicates cell-derived and platelet-derived extracellular vesicles (EVs), which comprise microvesicles (MVs), exosomes, and apoptotic bodies, in the modulation of the coagulation cascade in hemostasis and thrombosis. As these EVs are associated with intercellular communication, molecular recycling, and metastatic niche creation, emerging evidence explores EVs as valuable diagnostic and therapeutic approaches in thrombotic and prothrombotic diseases.

Complement and Coagulation System Crosstalk in Synaptic and Neural Conduction in the Central and Peripheral Nervous Systems

Complement and coagulation are both key systems that defend the body from harm. They share multiple features and are similarly activated. They each play individual roles in the systemic circulation in physiology and pathophysiology, with significant crosstalk between them. Components from both systems are mapped to important structures in the central nervous system (CNS) and peripheral nervous system (PNS). Complement and coagulation participate in critical functions in neuronal development and synaptic plasticity. During pathophysiological states, complement and coagulation factors are upregulated and can modulate synaptic transmission and neuronal conduction. This review summarizes the current evidence regarding the roles of the complement system and the coagulation cascade in the CNS and PNS. Possible crosstalk between the two systems regarding neuroinflammatory-related effects on synaptic transmission and neuronal conduction is explored. Novel treatment based on the modulation of crosstalk between complement and coagulation may perhaps help to alleviate neuroinflammatory effects in diseased states of the CNS and PNS.

Thrombin: A Pivotal Player in Hemostasis and Beyond

The serine protease thrombin, a naturally derived enzyme, plays a key role in hemostasis by converting fibrinogen to fibrin and activating coagulation factor XIII whereby the fibrin clot is stabilized. Furthermore, thrombin activates platelets through protease-activated receptors on the platelet surface. Conversely, thrombin also exerts anticoagulant effects, enhancing the protein C activity while complexed with thrombomodulin. During recent years, it has become evident that thrombin has significant effects beyond hemostasis, as it contributes also to modulation of the endothelium, promotes inflammation and angiogenesis, and plays a role in tumor progression. Yet, due to the very short half-life and almost immediate inhibition in fluid phase by antithrombin, thrombin itself remains elusive, and only indirect measurement of thrombin generation is possible. This review provides a description of structure and mechanisms of action of thrombin both in physiological and pathological processes. Furthermore, it summarizes laboratory tests that measure in vivo or ex vivo thrombin generation, and presents knowledge on the value of these biomarkers in bleeding disorders, cardiopulmonary bypass surgery, and thromboembolic risk assessment in different patient populations. Finally, this review outlines further perspectives on using thrombin generation biomarkers for research purposes and in clinical practice.

Thrombin-Fibrin(ogen) Interactions, Host Defense and Risk of Thrombosis

Fibrinogen is a well-known risk factor for arterial and venous thrombosis. Its function is not restricted to clot formation, however, as it partakes in a complex interplay between thrombin, soluble plasma fibrinogen, and deposited fibrin matrices. Fibrinogen, like thrombin, participates predominantly in hemostasis to maintain vascular integrity, but executes some important pleiotropic effects: firstly, as observed in thrombin generation experiments, fibrin removes thrombin from free solution by adsorption. The adsorbed thrombin is protected from antithrombins, notably α2-macroglobulin, and remains physiologically active as it can activate factors V, VIII, and platelets. Secondly, immobilized fibrinogen or fibrin matrices activate monocytes/macrophages and neutrophils via Mac-1 interactions. Immobilized fibrin(ogen) thereby elicits a pro-inflammatory response with a reciprocal stimulating effect of the immune system on coagulation. In contrast, soluble fibrinogen prohibits recruitment of these immune cells. Thus, while fibrin matrices elicit a procoagulant response, both directly by protecting thrombin and indirectly through the immune system, high soluble fibrinogen levels might protect patients due to its immune diminutive function. The in vivo influence of the 'protective' plasma fibrinogen versus the 'pro-thrombotic' fibrin matrices on thrombosis should be explored in future research.

History of the West of Scotland Haemophilia Centre, Glasgow, 1950-2019

Over 70 years, the West of Scotland Haemophilia Centre in the UK has played a leading role in research, education and training. Its staff studied the natural history of haemophilias, their complications, and their treatment complications, pioneered the use of fibrinolytic inhibitors to reduce the risk of receiving a blood transfusion and developed national audit. Collaborations across Scotland with other haemophilia centres and the Scottish National Blood Transfusion Service progressed self-suffi ciency in NHS-produced factor concentrates, heat treatments to prevent HIV and hepatitis transmission, and finally, replacement of human by recombinant factor concentrates.

Over 50 Years of Fibrinogen Concentrate

March 2013 represented the 50th anniversary of the first license granted for a fibrinogen concentrate. In this review, we look at the history of bleeding management that led to the development of fibrinogen concentrate, discuss its current use, and consider future developments for this product.

A review of the scientific and literary accomplishments of Professor R.G. Macfarlane CBE, FRS

This article gives an account of some of the pioneer work of Professor R.G. Macfarlane CBE, FRS in haemostasis and fibrinolysis. His Cascade hypothesis, which together with the Waterfall, became the most cited of all papers on blood coagulation in the latter part of the 20th century, is described, together with its rebuttal and defence. Macfarlane had the gift of writing in elegant prose and his papers on the philosophy of science and his biographies of Lord Florey and Fleming are reviewed. The biography of Sir Alexander Fleming is a great work that deserves to be on the shelves of every library.

Optimal haemophilia care versus the reality

Haemophilia A and B are inherited bleeding disorders whose diagnosis and management is generally well established and best provided by specialists in a comprehensive care setting. Patients may be put at unnecessary risk if appropriate expertise is not sought for the management of accidents and surgery. The delivery of a high quality comprehensive service to patients with bleeding disorders depends upon defined standards and a network of haemophilia centres in the UK with similar models in other countries. In developing countries, despite a shortage or absence of treatment products, development of local expertise results in an improved outlook and reduction in mortality. Optimal care for severe haemophilia includes accurate diagnosis, early and adequate factor replacement for bleeding episodes and the provision of prophylaxis from an early age to prevent joint bleeding and the consequent arthropathy. Haemophilia treatment is expensive resulting in considerable inequity in provision of care across the world. Despite decades of experience, optimal treatment levels are not robustly defined. Transfusion-transmitted infections continue to have a significant impact on patient management. The development of inhibitory antibodies seriously complicates the management both in morbidity and cost. While gene therapy has not yet produced the hoped-for cure, new technologies will produce improved products.