OC 77.3 - Platelet factor XIII-A regulates platelet function and promotes clot retraction and stability

Wednesday, July 13, 2022

10:45 AM – 11:00 AM

Location: ExCel Center, ICC Capital Suite Room 17

Presentation Format: In-Person

Presenting Author(s)

Joanne Mitchell, PhD

Postdoctoral Research Fellow
University of Birmingham
Birmingham, England, United Kingdom

Co-Author(s)

GL

Gemma Little

PhD Student
University of Reading
READING, England, United Kingdom
AB

Alex Bye

Research Fellow
St Georges University London
London, England, United Kingdom
Amanda J. Unsworth, DPhil

Senior Lecturer
Manchester Metropolitan University
Manchester, England, United Kingdom
RG

Renato Gaspar

Postdoctoral Research associate
University of Reading
Reading, England, United Kingdom
NK

Neline Kriek

Postdoctoral Research Assistant
University of Reading
READING, England, United Kingdom
TS

Tanya Sage

Research Technician
University of Reading
READING, England, United Kingdom
AS

Alexander Stainer

Postdoctoral Research associate
University of Reading
Reading, England, United Kingdom
DS

Dayo Sangowawa

student
University of Reading
Reading, England, United Kingdom
Nicola Curry, MD, FRCP, FRCPath

Associate Professor
Oxford University Hospitals NHS Foundation Trust
Oxford, England, United Kingdom
Susan Shapiro, MD, PhD

Consultant Hematologist
Oxford University Hospitals National Health Service Foundation Trust, Oxford, UK
Oxford, England, United Kingdom
MD

Michael Desborough

consultant haematologist
Oxford University Hospitals NHS Foundation Trust
Oxford, England, United Kingdom
Claire S. Whyte, PhD

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

Jonathan M. Gibbins, PhD

Professor
Institute for Cardiovascular and Metabolic Research, School of Biological sciences, University of Reading, Reading, UK
Reading, England, United Kingdom
Nicola J. J. Mutch, PhD

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

Chris Jones

Associate Professor
Reading School of Biological Sciences, University of Reading, Whiteknights, Reading, United Kingdom
Reading, England, United Kingdom

Background: Platelet factor XIII-A (FXIII-A) is externalised upon platelet activation and is functional in cross-linking extracellular fibrin to stabilise thrombi against fibrinolysis. FXIII-A is abundant inside platelets and has many intracellular substrates, suggesting it may be involved in platelet function.

Aims: Determine the role platelet FXIII-A plays in platelet function.

Methods: Platelets were isolated from FXIII-deficient patients and normal donors and assessed using confocal microscopy and flow cytometry. Clots or thrombi under flow were formed from FXIII-depleted plasma with normal healthy or FXIII-deficient platelets. FXIII was inhibited using a cell-permeable transglutaminase inhibitor (TGI).

Results: FXIII-deficient platelets contained no detectable FXIII-A and were not functional in stabilising FXIII-depleted thrombus lysis, compared to the stabilising effect achieved by healthy platelets confirming platelet FXIII-A protects thrombi against fibrinolysis.
Retraction of FXIII-depleted plasma clots was reduced in the presence of FXIII-deficient platelets and platelets with TGI, compared to untreated healthy platelets (P < 0.05) indicating platelet FXIII-A plays roles in driving clot retraction.
Fibrinogen binding to FXIII-deficient platelets and platelets treated with TGI (P < 0.0001) was reduced when compared to untreated normal platelets, and FXIII-deficient platelets had reduced sensitivity to CRP-XL and TRAP6 stimulation, suggesting FXIII-A may be involved in the signalling processes that regulate platelet activation. Furthermore, FXIII-A activity co-localized with the platelet cytoskeleton, suggesting FXIII-A may participate cross-link actin.
Platelet spreading on collagen (P < 0.01) and fibrinogen (P < 0.05) was attenuated in TGI treated and FXIII-deficient platelets compared to normal platelets. In line with this, FXIII-deficient platelets and TGI-treated normal platelets had reduced adherence to fibrinogen and formed smaller thrombi on fibrinogen under flow.

Conclusion(s): Fibrinogen binding, spreading, platelet sensitivity to agonists and clot retraction are attenuated in TGI treated and FXIII-deficient platelets. These data suggest platelet FXIII-A is actively involved in these processes, possibly by mediating intracellular cytoskeletal rearrangement.