title: Thrombin and fibrinogen γ' impact clot structure by marked effects on intrafibrillar structure and protofibril packing.
abstract: Previous studies have shown effects of thrombin and fibrinogen γ' on clot structure. However, structural information was obtained using electron microscopy, which requires sample dehydration. Our aim was to investigate the role of thrombin and fibrinogen γ' in modulating fibrin structure under fully hydrated conditions. Fibrin fibers were studied using turbidimetry, atomic force microscopy, electron microscopy, and magnetic tweezers in purified and plasma solutions. Increased thrombin induced a pronounced decrease in average protofibril content per fiber, with a relatively minor decrease in fiber size, leading to the formation of less compact fiber structures. Atomic force microscopy under fully hydrated conditions confirmed that fiber diameter was only marginally decreased. Decreased protofibril content of the fibers produced by high thrombin resulted in weakened clot architecture as analyzed by magnetic tweezers in purified systems and by thromboelastometry in plasma and whole blood. Fibers produced with fibrinogen γ' showed reduced protofibril packing over a range of thrombin concentrations. High-magnification electron microscopy demonstrated reduced protofibril packing in γ' fibers and unraveling of fibers into separate protofibrils. Decreased protofibril packing was confirmed in plasma for high thrombin concentrations and fibrinogen-deficient plasma reconstituted with γ' fibrinogen. These findings demonstrate that, in fully hydrated conditions, thrombin and fibrinogen γ' have dramatic effects on protofibril content and that protein density within fibers correlates with strength of the fibrin network. We conclude that regulation of protofibril content of fibers is an important mechanism by which thrombin and fibrinogen γ' modulate fibrin clot structure and strength.
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and Molecular and Nanoscale Physics group, School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom; and.
authors.forename: Marco M
authors.initials: MM
authors.lastname: Domingues
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Fraser L
authors.initials: FL
authors.lastname: Macrae
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Cédric
authors.initials: C
authors.lastname: Duval
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Helen R
authors.initials: HR
authors.lastname: McPherson
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Katherine I
authors.initials: KI
authors.lastname: Bridge
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Ramzi A
authors.initials: RA
authors.lastname: Ajjan
authors.affiliation: Department of Cardiovascular Science, Faculty of Medicine, Dentistry, and Health, University of Sheffield, Sheffield, United Kingdom.
authors.forename: Victoria C
authors.initials: VC
authors.lastname: Ridger
authors.affiliation: Molecular and Nanoscale Physics group, School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom; and.
authors.forename: Simon D
authors.initials: SD
authors.lastname: Connell
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Helen
authors.initials: H
authors.lastname: Philippou
authors.affiliation: Thrombosis and Tissue Repair Group, Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine and Multidisciplinary Cardiovascular Research Centre, Faculty of Medicine and Health, and.
authors.forename: Robert A S
authors.initials: RA
authors.lastname: Ariëns
mesh_terms: D001777:Blood Coagulation; D001809:Blood Viscosity; D015241:Fibrinogens, Abnormal / Q000378:metabolism* / Q000648:ultrastructure*; D006801:Humans; D018625:Microscopy, Atomic Force; D009391:Nephelometry and Turbidimetry; D013917:Thrombin / Q000378:metabolism* / Q000648:ultrastructure*; D013927:Thrombosis / Q000378:metabolism
chemical_list: D015241:Fibrinogens, Abnormal; C527521:fibrinogen gamma'; D013917:Thrombin