Observation of granulocyte function during ex vivo thrombus formation for patients with ANKRD26-associated thrombocytopenia

Abstract

ANKRD26-associated thrombocytopenia is a non-syndromic hereditary thrombocytopenia for which there are currently no formal diagnostic criteria. It is known that the probability of myeloid leukemia in patients with pathogenetic variants in the ANKRD26 gene significantly increases, however, studies of the functioning of granulocytes in this pathology have not been conducted. Aims: Analysis of the functioning of granulocytes and platelets during ex vivo thrombosis in patients with ANKRD26-associated thrombocytopenia. The study was approved by the Independent Ethics Committee of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology, and Immunology. Two patients and 10 healthy volunteers were included in the study. Intracellular signaling and platelet functional responses were observed by continuous flow cytometry. Ex vivo thrombus formation and granulocyte functioning were observed on a fluorescence microscope in parallel-plane flow chambers containing fibrillar collagen. Upon physiological activation (ADP, collagen) of patients’ platelets in vitro, there were no significant differences between the platelets of patients and healthy donors. However, the observed ex vivo size of platelet aggregates was significantly reduced in comparison with healthy donors and published data on patients with other thrombocytopenias. The observed number and activity (movement velocity) of granulocytes of patients was within normal values. However, significant morphological differences were observed for granulocytes of patients compared with granulocytes of healthy donors: there was an increased spreading of granulocytes, in particular, expressed in a large number of thin pseudopodia, as well as an increased curvature of the motion trajectories of granulocytes. Ex vivo observation of thrombus formation in patients with ANKRD26- associated thrombocytopenia, a significantly reduced thrombus size is observed with normal platelet activity and increased variability in the shape of granulocytes.