OC 39.3 - Receptor-bound plasminogen impacts on early platelet deposition and fibrin accumulation

Monday, June 24, 2024

10:00 – 10:15 ICT

Room: 208 A-D

Presenting Author(s)

Claire S. Whyte, PhD

PhD, Advanced Research Fellow
Aberdeen Cardiovascular & Diabetes Centre, Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen
Aberdeen, Scotland, United Kingdom

Co-Author(s)

DK

Dean Kavanagh

Assistant Professor
University of Birmingham
Birmingham, England, United Kingdom
AL

Ausra Lionikiene

Research Technician
University of Aberdeen
Aberdeen, Scotland, United Kingdom
SW

Steve P. Watson

Professor
University of Birmingham
Birmingham, England, United Kingdom
RP

Robert J. Parmer

Professor
9Department of Medicine, Veterans Administration San Diego Healthcare System and University of California
San Diego, California, United States
LM

Lindsey Miles

Professor of Cell and Molecular Biology
The Scripps Research Institute
San Diego, California, United States
Nicola J. Mutch, MSc Hons, PhD

Professor
Aberdeen Cardiovascular & Diabetes Centre, Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen
Aberdeen, Scotland, United Kingdom

Background: Platelets expose and bind plasminogen and facilitate plasmin generation. Human and murine platelets express the transmembrane lysine-dependent plasminogen receptor, Plg-RKT, which promotes retention of plasminogen on the activated platelet surface.

Aims: To determine the role of platelet Plg-RKT in dictating thrombus dynamics.

Methods: Ex vivo thrombi were formed by flowing blood from wild type (WT) or Plg-RKT-/- mice over collagen and tissue factor coated microfluidic biochips at 250 – 1000 s-1. Dylight633 (DL633)-labelled plasminogen and AlexaFluor488-fibrinogen were incorporated ± tissue plasminogen activator (tPA) and accumulation was monitored by fluorescence microscopy. Thrombosis was induced in the carotid artery using 30% FeCl3 with prior infusion of AlexaFluor647-labelled fibrinogen and DyLight488-GP1bβ antibody to label platelets. After 5 min tPA was infused. Thrombus formation was imaged for 30 min in real-time using a Zeiss Examiner upright intravital microscope equipped with spinning disk confocal. Platelet aggregation was measured after stimulation with 0.1 U/ml thrombin.

Results: An absence of Plg-RKT attenuated plasminogen accumulation in thrombi formed ex vivo at venous and arterial shear rates was reduced in Plg-RKT-/-. The rate of fibrin degradation in thrombi formed from Plg-RKT-/- mice was slower compared to WT. Thrombi formed in vivo showed similar fibrinogen accumulation in Plg-RKT-/- and WT mice. After tPA infusion, persistence and accumulation of fibrin(ogen) was enhanced in Plg-RKT-/- mice indicating reduced fibrinolytic capacity. Initial platelet deposition was significantly higher in Plg-RKT-/- mice compared to WT. In vitro platelet aggregation to thrombin was enhanced in Plg-RKT-/- mice compared to WT.

Conclusion(s): Plg-RKT facilitates plasminogen accumulation within thrombi. Interestingly, absence of Plg-RKT altered initial platelet depositions as well as fibrin accumulation. This could suggest that the presence of plasminogen acts to control developing thrombi and shape the resulting architecture.