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Open Access
CC BY 4.0 · TH Open 2019; 03(02): e132-e145
DOI: 10.1055/s-0039-1688934
Original Article
Georg Thieme Verlag KG Stuttgart · New York

The Ratio of Factor VIIa:Tissue Factor Content within Microvesicles Determines the Differential Influence on Endothelial Cells

Yahya Madkhali
1   Department of Biomedical Sciences, University of Hull, Hull, United Kingdom
2   Department of Medical Laboratories, College of Applied Medical Sciences, Majmaah University, KSA, Al Majmaah, Saudi Arabia
,
Sophie Featherby
1   Department of Biomedical Sciences, University of Hull, Hull, United Kingdom
,
Mary E. Collier
3   Department of Cardiovascular Sciences, University of Leicester, Glenfield General Hospital, Leicester, United Kingdom
,
Anthony Maraveyas
4   Division of Cancer–Hull York Medical School, University of Hull, Hull, United Kingdom
,
John Greenman
1   Department of Biomedical Sciences, University of Hull, Hull, United Kingdom
,
Camille Ettelaie 
1   Department of Biomedical Sciences, University of Hull, Hull, United Kingdom
› Author Affiliations
Further Information

Publication History

31 December 2018

10 April 2019

Publication Date:
15 May 2019 (online)

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Abstract

Tissue factor (TF)-positive microvesicles from various sources can promote cellular proliferation or alternatively induce apoptosis, but the determining factors are unknown. In this study the hypothesis that the ratio of fVIIa:TF within microvesicles determines this outcome was examined. Microvesicles were isolated from HepG2, BxPC-3, 786-O, MDA-MB-231, and MCF-7 cell lines and microvesicle-associated fVIIa and TF antigen and activity levels were measured. Human coronary artery endothelial cells (HCAECs) were incubated with these purified microvesicles, or with combinations of fVIIa-recombinant TF, and cell proliferation/apoptosis was measured. Additionally, by expressing mCherry-PAR2 on HCAEC surface, PAR2 activation was quantified. Finally, the activation of PAR2 on HCAEC or the activities of TF and fVIIa in microvesicles were blocked prior to addition of microvesicles to cells. The purified microvesicles exhibited a range of fVIIa:TF ratios with HepG2 and 786-O cells having the highest (54:1) and lowest (10:1) ratios, respectively. The reversal from proapoptotic to proliferative was estimated to occur at a fVIIa:TF molar ratio of 15:1, but HCAEC could not be rescued at higher TF concentrations. The purified microvesicles induced HCAEC proliferation or apoptosis according to this ruling. Blocking PAR2 activation on HCAEC, or inhibiting fVIIa or TF-procoagulant function on microvesicles prevented the influence on HCAEC. Finally, incubation of HCAEC with recombinant TF resulted in increased surface exposure of fVII. The induction of cell proliferation or apoptosis by TF-positive microvesicles is dependent on the ratio of fVIIa:TF and involves the activation of PAR2. At lower TF concentrations, fVIIa can counteract the proapoptotic stimulus and induce proliferation.

Keywords

tissue factor - microvesicles - protease-activated receptor-2 - apoptosis - cell proliferation - factor VIIa

Authors' Contributions

The study was designed by Y.M., M.E.C., A.M., and C.E., and the experimental work was performed by Y.M., S.F., and C.E. The data were evaluated by Y.M., M.E.C., J.G., A.M., and C.E. and the manuscript was prepared by Y.M., J.G., and C.E.


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