OC 66.5 - Mitochondrial dysfunction in platelets from patients with JAK2 V617F essential thrombocythemia and polycythemia vera underlies thrombo-hemorrhagic complications

Tuesday, July 12, 2022

3:45 PM – 4:00 PM

Location: ExCel Center, ICC Capital Suite Room 10&11

Presentation Format: In-Person

Co-Author(s)

OE

Orlando Esparza, MD

Instructor
University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States
BM

Brandon McMahon

Associate Professor
Division of Hematology, University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States
GH

Giovanny Hernandez

Professional Research Assistant
Department of Pediatrics Hematology/Oncology and Bone Marrow Transplantation, University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States
DL

Dennis Le

Professional Research Assistant
Department of Pediatrics Hematology/Oncology and Bone Marrow Transplantation, University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States
MK

Marguerite Kelher

Research Instructor
Department of Surgery, University of Colorado Anschutz Medical Campus/Vitalant Research Institute
Aurora, Colorado, United States
TN

Travis Nemkov

Assistant Professor
Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States
AD

Angelo D'Alessandro

Associate Professor
Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States
JL

Jose Lopez

Professor
Division of Hematology, University of Washington/Bloodworks NW Research Institute
Seattle, Washington, United States

Presenting Author(s)

PD

Pavel Davizon-Castillo

Assistant Professor
Department of Pediatrics Hematology/Oncology and Bone Marrow Transplantation, Hemophilia and Thrombosis Center, University of Colorado Anschutz Medical Campus
Aurora, Colorado, United States

Background: Myeloproliferative neoplasms are a group of pro-inflammatory clonal hematopoietic disorders. Patients with JAK2 V617F essential thrombocythemia (ET) and polycythemia vera (PV) experience thrombo-hemorrhagic events. We have previously identified that platelets from patients with ET/PV exhibit dysmorphic mitochondria. In light of these changes, we hypothesize that platelet metabolism and function are altered.

Aims: We sought to identify and characterize the metabolic and functional alterations of platelets from patients with JAK2 V617F ET/PV.

Methods: Platelets from sex and age-matched healthy controls and individuals with ET/PV were studied. Platelet activation, calcium mobilization and mitochondrial polarization were determined by flow cytometry. Thrombus formation under flow was measured with the Total Thrombus-formation Analysis System analyzer. Platelet bioenergetics were studied with the Seahorse extracellular flux analyzer. Semi-quantitative metabolomics was performed using the Vanquish UHPLC system. Clot retraction analysis was calculated by weight of extruded serum.

Results: ET/PV platelets demonstrated elevated cytoplasmic calcium under resting conditions and after stimulation with thrombin (Figure 1A). ET/PV platelets displayed greater membrane depolarization when compared to healthy controls (p=0.03). ET/PV platelets also exhibited decreased basal respiration and ATP-linked respiration (Figure 1B) and reduced ADP and ATP pools (Figure 1C). Functionally, ET/PV platelets exposed more procoagulant phosphatidylserine on the outer membrane leaflet and, under arterial flow conditions, formed thrombi faster (Figure 2A-B). Despite the accelerated clot formation, platelet contraction was significantly decreased in ET/PV platelets (p=0.04).

Conclusion(s): We show that JAK2 V617F ET/PV platelets have dysfunctional mitochondria (i.e., perturbed calcium flux and loss of mitochondrial membrane potential), leading to defective energy production. Energy-demanding processes such as maintaining plasma membrane phospholipid polarity and clot retraction may be disrupted in ET/PV platelets leading to a procoagulant phenotype, accelerated thrombus formation, and an unstable clot. Our findings may explain why patients with ET/PV are at an increased risk for thrombo-hemorrhagic complications.