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Updated: Aug 25, 2026

Flow Cytometry Analysis of Tissue Factor Expression in Human Platelets
Published on: November 22, 2024
Activated platelets stimulate tissue factor expression in smooth muscle cells
Plinio Cirillo1, Paolo Golino, Paolo Calabrò
1Division of Cardiology, University of Naples Federico II, Naples, Italy.
Unlabelled:
Tissue factor (TF)-induced activation of the coagulation plays a key role in the pathophysiology of acute coronary syndromes. Because TF represents the initial trigger of the coagulation cascade, its expression in the arterial wall is tightly regulated.
Objective:
To determine whether and which soluble mediators released during platelet activation may upregulate TF expression in smooth muscle cells (SMCs).
Methods And Results:
Rabbit SMCs were challenged with collagen-activated platelets and their effects on TF mRNA transcription and protein expression were evaluated at different time points (30 min, 1, 2, 4, 8, 12 and 24 h) by RT-PCR, immunofluorescence and a two-stage colorimetric assay. A progressive increase in TF mRNA, peaking at 2 h, was evident in SMCs stimulated with activated platelets with respect to baseline. The increase in TF mRNA expression was associated with a parallel increase in TF protein, as demonstrated by immunofluorescence and by colorimetric assay. In a different set of experiments, selected platelet-derived soluble mediators were shown to induce TF mRNA expression.
Conclusions:
Activated platelets upregulate TF, via release of several soluble mediators, in a cell population widely expressed in the vessel wall and in atherosclerotic plaques, such as SMCs. This phenomenon might play an important role in sustaining thrombus formation in vivo.
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