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    Poster Networking

    Coagulation and Natural Anticoagulants

    Poster Networking Session

    PB0589 - Human transthyretin (hTTR) amyloid fibrils induce plasma clotting by activating the intrinsic pathway of blood coagulation: implications in the pathogenesis of hTTR intracardiac thrombosis

    Monday, June 26, 2023
    18:30 – 19:30 ET
    Room: Exhibition

      Presenting Author(s)

    • Alessia Dei Rossi

      PhD student
      Dept. of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
      Padova, Veneto, Italy

      • Co-Author(s)

    • LA

      Laura Acquasaliente

      Assistant Professor
      Dept. of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
      Padova, Veneto, Italy

    • DP

      Daniele Peterle

      Post Doc
      Dept. of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
      Boston, Massachusetts, United States

    • NB

      Nicol Berti

      Student
      Dept. of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
      Padova, Veneto, Italy

    • AN

      Alessandro Negro

      Professor
      Dept. of Biomedical Sciences, University of Padua, Padua, Italy
      Padova, Veneto, Italy

    • GV

      Guglielmo Verona

      Professor
      Center for Amyloidosis, University College London, London, United Kingdom
      London, England, United Kingdom

    • JG

      Julian Gillmore

      Professor
      Center for Amyloidosis, University College London, London, United Kingdom
      London, England, United Kingdom

    • OL

      Ornella Leone

      Professor
      IRCCS University Hospital of Bologna, Bologna, Italy
      Bologna, Emilia-Romagna, Italy

    • ST

      Serena Toffanin

      PhD student
      Department of Medicine, Thrombotic and Haemorrhagic Diseases Unit, University of Padua Medical School, Padua (Italy)
      Padua, Veneto, Italy

    • RD

      Raimondo De Cristofaro, MD, PhD

      Professor, Haemostasis and Thrombosis Center Director
      1.Fondazione Policlinico Universitario A. Gemelli, IRCCS, Center for Hemorrhagic and Thrombotic Diseases and Haemophilia Center, Rome, Italy; 2. Catholic University, Translational Medicine and Surgery Department Rome, Italy
      Roma, Lazio, Italy

    • FC

      Francesco Cappelli

      Professor
      Dept. of Experimental and Clinical Medicine, University of Florence, Florence, Italy
      Florence, Toscana, Italy

    • FP

      Federico Perfetto

      Professor
      Dept. of Internal Medicine, Amyloidosis Research Center, University of Florence, Florence, Italy
      Florence, Toscana, Italy

    • Paolo Simioni, MD, PhD (he/him/his)

      Full Professor
      Department of Medicine, Thrombotic and Haemorrhagic Diseases Unit, University of Padua Medical School, Padua (Italy)
      Padua, Veneto, Italy

    • VB

      Vittorio Bellotti

      Professor
      Dept of Molecular Medicine, University of Pavia, Pavia, Italy
      Pavia, Lombardia, Italy

      • Co-Author(s)

    • VD

      Vincenzo De Filippis

      Associate Professor
      University of Padua
      Padova, Veneto, Italy

    Background: hTTR amyloidosis, from both wild-type TTR and pathogenic variants(e.g.S52P), is characterized by amyloid deposition in several organs,especially in the heart. It is associated with cardiomyopathy, intracardiac thrombosis and cerebral amyloid angiopathy. The composition of amyloid deposits is a mixture of intact hTTR and its most abundant proteolytic fragment hTTR(49-127). However, the biochemical pathways leading to intracardiac thrombosis are unknown.

    Aims: Demonstrate the ability of hTTR fibrils to induce coagulation,and establish the molecular mechanisms resulting in the activation of blood coagulation.

    Methods: Natural fibrils were isolated from autopsies of patients with genetic ATTR. Wild-type hTTR and hTTR(49-127) were obtained as recombinant species in E.coli,and allowed to fibrillate for 72h at 900rpm. Fibril-induced fibrin generation in human plasma or whole blood(WB) was monitored by turbidimetric, fluorogenic,and thromboelastometric assay. The role of each coagulation factor was established using factor-deficient plasmas or with chromogenic substrates. Binding of coagulation factors to hTTR fibrils was quantified by ELISA. Histopathological images of cardiac amyloid infiltrations were from endomyocardial biopsies of patients with thrombosis in ATTR-CM.

    Results: Histopathological investigation reveals exposure of amyloid fibrils in the heart chambers and localization of a small intracardiac thrombus nearby(Fig.1). Data obtained by assays on plasma and WB indicate that both natural and artificial hTTR fibrils similarly induce clotting. Addition of either hTTR in a non-fibrillar state or of the amorphous precipitate of ß-casein does not trigger clotting. Furthermore,amyloid fibrils induce autoactivation of the coagulation factor XII, at the initial step of the intrinsic pathway of blood coagulation cascade, and increase the efficiency of prothrombin activation by FXa of 40 times(Fig.2).

    Conclusion(s): Amyloid fibrils provide an ordered surface on which coagulation factors, especially FXII, can anchor and become activated. These mechanisms can explain the hypercoagulable state that can lead to the formation of thrombi observed in patients affected by cardiac amyloidosis and cerebral amyloid angiopathy.