PB0346 - Inhibition of PI3KC2alpha selectively reduces platelet recruitment after vascular injury while preserving thrombus architecture

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Pia Larsson, PhD

Postdoctoral Research Fellow
Monash University
Melbourne, Victoria, Australia

Co-Author(s)

Natasha M. Setiabakti, MD

PhD Student
Monash University
Melbourne, Victoria, Australia
VT

Volga Tarlac

Senior Research Assistant
Australian Centre for Blood Diseases, Monash University
Melbourne, Victoria, Australia
AM

Abigail McGovern

PhD Student
Department of Anatomy and Developmental Biology, Monash University
Melbourne, Victoria, Australia
JN

Juan Nunez-Iglesias

Senior Research Fellow
Anatomy and Developmental Biology, Monash University
Melbourne, Victoria, Australia
KT

Kjersti Tunströmer

Senior Research Engineer
University of Linkoping
Linkoping, Ostergotlands Lan, Sweden
JH

Justin R. Hamilton

Group Leader
Australian Centre for Blood Diseases, Monash University
Melbourne, Victoria, Australia
NB

Niklas Boknäs, MD, PhD

Consultant, Hematology
Region Östergötland
Linkoping, Ostergotlands Lan, Sweden

Background: We have recently examined the class II PI3-Kinase enzyme PI3KC2alpha (C2a) as a potential therapeutic target for antithrombotic therapy. Interestingly, despite being anti-thrombotic in whole blood flow assays in vitro and in vivo, we have failed to detect any effect of C2a deletion on platelet function or traditional readouts of platelet activation. Thus, the mechanism by which C2a inhibition inhibits thrombosis is still unknown.

Aims: To investigate the effects of pharmacological C2a inhibition on thrombus formation in vivo.

Methods: We combined a novel intravital microscopy thrombosis model with automatized segmentation and tracking algorithms to track the positions, activation states and movements of a large number of platelets during thrombus formation. Labelled donor platelets were injected into recipient mice treated with our novel C2a inhibitor MIPS-21335, or vehicle. 4D confocal imaging of thrombus formation was performed for 10 min after laser injuries to mesenteric veins. A neural network trained for platelet segmentation was used to analyse the resulting time-lapse data.

Results: Our analysis revealed no significant effects of MIPS-21335 treatment on the acute early phase of thrombus build-up in vivo. However, starting at 3 min after injury there was a significant reduction of new platelets being recruited to the thrombus, specifically to the outer lateral parts that experience elevated shear gradients. Total platelet numbers, packing density and stability in the injury zone were not affected by C2a inhibition indicating that this treatment did not affect the structural integrity of the thrombus core.

Conclusion(s): Pharmacological inhibition of PI3KC2alpha maintains the structure and stability of the developing thrombus core while selectively reducing platelet accumulation to the outer parts of the thrombus. Thus PI3KC2alpha appears to be a promising anti-thrombotic target that can potentially show selectivity against pathological expansion of a thrombus while maintaining its haemostatic function.