Response: functionally active platelets do express tissue factor

Camera, Marina; Brambilla, Marta; Boselli, Daniela; Facchinetti, Laura; Canzano, Paola; Rossetti, Laura; Toschi, Vincenzo; Tremoli, Elena

doi:10.1182/blood-2012-02-410043

Cited by 15 publications

(13 citation statements)

References 14 publications

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“…Taken together the data clearly demonstrate that platelets from healthy dondors do not express either the reduced or oxidized forms of TF prior to or following activation. These results are in contrast to several studies by Camera and colleagues who suggested based on flow cytometry that TF is expressed by activated platelets [11, 12, 37]. These studies utilized a commercially available anti-TF antibody (American Diagnostica 4507CJ, clone VIC7) and reported that TF expression by functionally active platelets was a rapid and dynamic process.…”

Section: 4 Discussioncontrasting

confidence: 81%

Platelets do not express the oxidized or reduced forms of tissue factor

Bouchard

Gissel

Whelihan

et al. 2014

Biochimica et Biophysica Acta (BBA) - General Subjects

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Background Expression of tissue factor (TF) antigen and activity in platelets is controversial and dependent upon the laboratory and reagents used. Two forms of TF were described: an oxidized functional form and a reduced nonfunctional form that is converted to the active form through the formation of an allosteric disulfide. This study tests the hypothesis that the discrepancies regarding platelet TF expression are due to differential expression of the two forms. Methods Specific reagents that recognize both oxidized and reduced TF were used in flow cytometry of unactivated and activated platelets and western blotting of whole platelet lysates. TF-dependent activity measurements were used to confirm the results. Results Western blotting analyses of placental TF demonstrated that, in contrast to anti-TF#5, which is directed against the oxidized form of TF, a sheep anti-human TF polyclonal antibody recognizes both the reduced and oxidized forms. Flow cytometric analyses demonstrated that the sheep antibody did not react with the surface of unactivated platelets or platelets activated with thrombin receptor agonist peptide, PAR-1. This observation was confirmed using biotinylated active site-blocked factor (F)VIIa: no binding was observed. Likewise, neither form of TF was detected by western blotting of whole platelet lysates with sheep anti-hTF. Consistent with these observations, no FXa or FIXa generation by FVIIa was detected at the surface of these platelets. Similarly, no TF-related activity was observed in whole blood using thomboelastography. Conclusion and Significance Platelets from healthy donors do not express either oxidized (functional) or reduced (nonfunctional) forms of TF.

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Section: 4 Discussioncontrasting

confidence: 81%

Platelets do not express the oxidized or reduced forms of tissue factor

Bouchard

Gissel

Whelihan

et al. 2014

Biochimica et Biophysica Acta (BBA) - General Subjects

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“…This event was time-dependent with the maximal expression of TF observed 15 to 30 minutes after stimulation and was also concentration-dependent. 14,15,36,37 Moreover, in our experimental setting, we also showed that the platelet-associated TF was functionally active, being able to bind to FVIIa and to trigger FXa and thrombin generation. 37,39 We also provided the evidence, for the first time, that platelets contain the TF mRNA.…”

Section: Historical Backgroundsupporting

confidence: 62%

“…platelet-associated TF still exists. [13][14][15][16][17] In this review, we aim to summarize the existing knowledge on platelet-associated TF and to speculate on its relevance to physiology and to atherothrombosis and coronary artery disease (CAD).…”

Section: Introductionmentioning

confidence: 99%

The Role of Tissue Factor in Atherothrombosis and Coronary Artery Disease: Insights into Platelet Tissue Factor

Camera

Toschi

Brambilla

et al. 2015

Semin Thromb Hemost

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The contribution of vessel wall-derived tissue factor (TF) to atherothrombosis is well established, whereas the pathophysiological relevance of the blood-borne TF is still a matter of debate, and controversies on the presence of platelet-associated TF still exist. In the past 15 years, several studies have documented the presence of TF in human platelets, the capacity of human platelets to use TF mRNA to make de novo protein synthesis, and the increase in the percentage of TF positive platelets in pathological conditions such as coronary artery disease (CAD). The exposure of vessel wall-derived TF at the site of vascular injury would play its main role in the initiation phase, whereas the blood-borne TF carried by platelets would be involved in the propagation phase of thrombus formation. More recent data indicate that megakaryocytes are committed to release into the bloodstream a well-defined number of TF-carrying platelets, which represents only a fraction of the whole platelet population. These findings are in line with the evidence that platelets are heterogeneous in their functions and only a subset of them is involved in the hemostatic process. In this review we summarize the existing knowledge on platelet associated TF and speculate on its relevance to physiology and to atherothrombosis and CAD.

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“…The lack of coagulant TF measured by the Zymuphen MP-TF is consistent with reports that TF-bearing MPs are not present in plasma under physiologic conditions, although this is discussed. 43,44 This study was prompted by the fact that thromboembolism can occur after plasma transfusion. [21][22][23] A retrospective survey of 139,842 adult patients identified that larger plasma volume transfused together with RBCs significantly increase the occurrence of deep vein thrombosis and pulmonary embolism.…”

Section: Discussionmentioning

confidence: 99%