A Subpopulation of ITP Patients Resembling Glanzmann Thrombasthenia Phenotype Revealed by Flow Cytometry Analysis of Platelet Intracellular Signalling

A. Martyanov^1,2,3, D.S. Morozova⁴, S.S. Uzueva³, M.A. Sorokina³, D.V. Fedorova³, P.A. Zharkov³, M.A. Panteleev^2,3,5, A.N. Sveshnikova^2,3,5

¹Institute for Biochemical Physics, Moscow, Russian Federation, ²Centre for Theoretical Problems of Physicochemical Pharmacology, Moscow, Russian Federation, ³National Medical Research Centre of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev, Moscow, Russian Federation, ⁴Lomonosov Moscow State University, Faculty of Medicine, Moscow, Russian Federation, ⁵Lomonosov Moscow State University, Faculty of Physics, Moscow, Russian Federation

Abstract Number: PB1369

Meeting: ISTH 2020 Congress

Theme: Platelet Disorders and von Willebrand Disease » Acquired Thrombocytopenias

Background: Immune thrombocytopenia (ITP) is an autoimmune condition characterized by isolated low platelet count, primarily induced by the loss of immune tolerance to the platelet glycoproteins. Different auto-antibodies may affect platelet function in addition to the platelet count. Distinguishing between the different ITP causes would facilitate the appropriate therapy selection.

Aims: Comparison of platelet calcium signalling, integrin activation and thrombus formation between ITP patients, Glanzmann thrombasthenia patients and healthy donors.

Methods: Whole hirudinated blood of healthy pediatric donors (CNT; n = 11) or pediatric patients with immune thrombocytopenia (ITP; n=36) and Glanzmann thrombastenia (GT; n=8) within 3 hours of collection was used in the experiments. Continues flow cytometry was used for characterization of calcium signalling and fibrinogen binding in quiescent platelets or in response to ADP, collagen-related peptide or TRAP. All numbers are given for ADP stimulation. Calcium levels are given in nM, fibrinogen binding is given in percentage of total integrin activation. Parallel-plate flow chambers were used for observation of thrombus formation. Numerical and statistical analysis was performed in Python 3.7.

Results: All ITP patients had increased basal platelet calcium concentrations (15±5(ITP) vs 8±5(CNT)). Clustering analysis of the flow cytometry revealed two subpopulations of ITP patients: the high fibrinogen binding (HFB) group with comparable to CNT fibrinogen binding and higher calcium mobilization (154±27 (HFB) vs 92±22(CNT)), and the low fibrinogen binding (LFB) group with lower fibrinogen binding (8±5 (LFB) vs 16±3(CNT)). GT platelets had calcium mobilization (81±23), fibrinogen-binding (5.1±0.3) and thrombus growth comparable to LFB. Two computational models of platelet intracellular signalling leading to integrin activation for HFB and LFB were developed.

Conclusions: The group of ITP patients with GT-like phenotype was revealed. This group is characterized by low integrin activation, high quiescent platelet calcium and thrombus growth impairment. The systems-biology analysis suggested weakened integrin activation for this population.

To cite this abstract in AMA style:

Martyanov A, Morozova DS, Uzueva SS, Sorokina MA, Fedorova DV, Zharkov PA, Panteleev MA, Sveshnikova AN. A Subpopulation of ITP Patients Resembling Glanzmann Thrombasthenia Phenotype Revealed by Flow Cytometry Analysis of Platelet Intracellular Signalling [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/a-subpopulation-of-itp-patients-resembling-glanzmann-thrombasthenia-phenotype-revealed-by-flow-cytometry-analysis-of-platelet-intracellular-signalling/. Accessed January 27, 2022.

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