Thrombin-initiated platelet activation in vivo is vWF independent during thrombus formation in a laser injury model
Christophe Dubois, Laurence Panicot-Dubois, Justin F. Gainor, Barbara C. Furie, Bruce Furie
Christophe Dubois, Laurence Panicot-Dubois, Justin F. Gainor, Barbara C. Furie, Bruce Furie
View: Text | PDF
Research Article Hematology

Thrombin-initiated platelet activation in vivo is vWF independent during thrombus formation in a laser injury model

Abstract

Adhesion of platelets to an injured vessel wall and platelet activation are critical events in the formation of a thrombus. Of the agonists involved in platelet activation, thrombin, collagen, and vWF are known to induce in vitro calcium mobilization in platelets. Using a calcium-sensitive fluorochrome and digital multichannel intravital microscopy to image unstimulated and stimulated platelets, calcium mobilization was monitored as a reporter of platelet activation (as distinct from platelet accumulation) during thrombus formation in live mice. In the absence of vWF, platelet activation was normal, but platelet adherence and aggregation were attenuated during thrombus formation following laser-induced injury in the cremaster muscle microcirculation. In WT mice treated with lepirudin, platelet activation was blocked, and platelet adherence and aggregation were inhibited. The kinetics of platelet activation and platelet accumulation were similar in FcRγ–/– mice lacking glycoprotein VI (GPVI), GPVI-depleted mice, and WT mice. Our results indicate that the tissue factor–mediated pathway of thrombin generation, but not the collagen-induced GPVI-mediated pathway, is the major pathway leading to platelet activation after laser-induced injury under the conditions employed. In the tissue factor–mediated pathway, vWF plays a role in platelet accumulation during thrombus formation but is not required for platelet activation in vivo.

Authors

Christophe Dubois, Laurence Panicot-Dubois, Justin F. Gainor, Barbara C. Furie, Bruce Furie

×

Figure 3

Platelet accumulation during thrombus formation after vessel wall injury in WT and vWF–/– mice.

Options: View larger image (or click on image) Download as PowerPoint
Platelet accumulation during thrombus formation after vessel wall injury...
Platelets were labeled with anti-mouse CD41 Fab fragments conjugated to Alexa Fluor 647. (A) The median integrated platelet fluorescence (y axis) for 43 thrombi in 4 WT mice and for 39 thrombi in 4 vWF–/– mice is presented versus time after vessel wall injury. (B) The distribution of the time to reach maximal size for each thrombus in WT mice and in vWF–/– mice. No significant difference was observed by the Wilcoxon rank sum test. (C) The distribution of the integrated platelet fluorescence for each thrombus in WT and vWF–/– mice at maximal size. WT thrombi were significantly larger than vWF–/– thrombi by the Wilcoxon rank sum test (P < 0.001). (D) The quartile distribution of the maximal integrated platelet fluorescence for each thrombus in WT and vWF–/– mice. Forty-three thrombi in WT mice and 39 thrombi in vWF–/– mice were ranked, and the percentage of thrombi of each genotype was determined independently in each quartile of the rank order. Black bars, WT mice; white bars, vWF–/– mice.