Thromb Haemost 2020; 120(06): 977-993
DOI: 10.1055/s-0040-1710012
Cellular Hemostasis and Platelets
Georg Thieme Verlag KG Stuttgart · New York

Glycoprotein VI is not a Functional Platelet Receptor for Fibrin Formed in Plasma or Blood

Danmei Zhang
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
,
Mariam Ebrahim
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
,
Kristin Adler
2  AdvanceCOR GmbH, Munich, Germany
,
Xavier Blanchet
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
,
Janina Jamasbi
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
,
Remco T. A. Megens
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
,
Kerstin Uhland
2  AdvanceCOR GmbH, Munich, Germany
,
Martin Ungerer
2  AdvanceCOR GmbH, Munich, Germany
,
Götz Münch
2  AdvanceCOR GmbH, Munich, Germany
,
Hans Deckmyn
3  Laboratory for Thrombosis Research, KU Leuven Campus Kulak, Kortrijk, Belgium
,
Christian Weber
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
4  DZHK (German Centre for Cardiovascular Research), Partner Site Munich Heart Alliance, Munich, Germany
5  Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
,
Natalie Elia
6  Department of Life Sciences, BGU (Ben Gurion University), Beer-Sheva, Israel
,
Reinhard Lorenz
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
,
Wolfgang Siess
1  Institute for Prevention of Cardiovascular Diseases, LMU (Ludwig-Maximilians University), Munich, Germany
4  DZHK (German Centre for Cardiovascular Research), Partner Site Munich Heart Alliance, Munich, Germany
› Author Affiliations
Funding The study was supported by grants from the Bayerische Forschungsstiftung (AZ 1145–14), the Deutsche Forschungsgemeinschaft (SFB1123/Z01 and SFB1123/B08) and the August-Lenz foundation.
Further Information

Publication History

30 October 2019

13 March 2020

Publication Date:
03 June 2020 (online)

Abstract

Glycoprotein VI (GPVI), a platelet collagen receptor, is crucial in mediating atherothrombosis. Besides collagen, injured plaques expose tissue factor (TF) that triggers fibrin formation. Previous studies reported that GPVI also is a platelet receptor for fibrinogen and fibrin. We studied the effect of anti-GPVI antibodies and inhibitors of GPVI signaling kinases (Syk and Btk) on platelet adhesion and aggregate formation onto immobilized fibrinogen and different types of fibrin under arterial flow conditions. Fibrin was prepared from isolated fibrinogen (“pure fibrin”), recombinant fibrinogen (“recombinant fibrin”), or generated more physiologically from endogenous fibrinogen in plasma (“plasma fibrin”) or by exposing TF-coated surfaces to flowing blood (“blood fibrin”). Inhibition of GPVI and Syk did not inhibit platelet adhesion and aggregate formation onto fibrinogen. In contrast anti-GPVI antibodies, inhibitors of Syk and Btk and the anti-GPIb antibody 6B4 inhibited platelet aggregate formation onto pure and recombinant fibrin. However, inhibition of GPVI and GPVI signaling did not significantly reduce platelet coverage of plasma fibrin and blood fibrin. Plasma fibrin contained many proteins incorporated during clot formation. Advanced optical imaging revealed plasma fibrin as a spongiform cushion with thicker, knotty, and long fibers and little activation of adhering platelets. Albumin intercalated in plasma fibrin fibers left only little space for platelet attachment. Pure fibrin was different showing a dense mesh of thin fibers with strongly activated platelets. We conclude that fibrin formed in plasma and blood contains plasma proteins shielding GPVI-activating epitopes. Our findings do not support a role of GPVI for platelet activation by physiologic fibrin.

The review process for this paper was fully handled by Gregory Y. H. Lip, Editor-in-Chief.


Supplementary Material