Endothelial cell protein C receptor-mediated redistribution and tissue-level accumulation of factor VIIa
Article first published online: 30 OCT 2012
© 2012 International Society on Thrombosis and Haemostasis
Journal of Thrombosis and Haemostasis
Volume 10, Issue 11, pages 2383–2391, November 2012
How to Cite
CLARK, C. A., VATSYAYAN, R., HEDNER, U., ESMON, C. T., PENDURTHI, U. R. and RAO, L. V. M. (2012), Endothelial cell protein C receptor-mediated redistribution and tissue-level accumulation of factor VIIa. Journal of Thrombosis and Haemostasis, 10: 2383–2391. doi: 10.1111/j.1538-7836.2012.04917.x
- Issue published online: 30 OCT 2012
- Article first published online: 30 OCT 2012
- Accepted manuscript online: 5 SEP 2012 12:22PM EST
- Received 22 June 2012, accepted 30 August 2012
- endothelial cell protein C receptor;
- factor VIIa;
- tissue factor;
Summary. Background: Recent studies show that activated factor VII (FVIIa) binds to the endothelial cell protein C receptor (EPCR) on the vascular endothelium; however, the importance of this interaction in hemostasis or pathophysiology is unknown.
Objective: The aim of the present study was to investigate the role of the FVIIa interaction with EPCR on the endothelium in mediating FVIIa transport from the circulation to extravascular tissues.
Methods: Wild-type, EPCR-deficient or ECPR-over-expressing mice were injected with human recombinant (r)FVIIa (120 μg kg−1 body weight) via the tail vein. At varying time intervals after rFVIIa administration, blood and various tissues were collected to measure FVIIa antigen and activity levels. Tissue sections were analyzed by immunohistochemistry for FVIIa and EPCR.
Results: The data reveal that, after intravenous (i.v.) injection, rFVIIa rapidly disappears from the blood and associates with the endothelium in an EPCR-dependent manner. Immunohistochemical analyses revealed that the association of FVIIa with the endothelium was maximal at 30 min and thereafter progressively declined. The FVIIa association with the endothelium was undetectable at time points exceeding 24 h post-FVIIa administration. The levels of rFVIIa accumulated in tissue correlate with expression levels of EPCR in mice and FVIIa associated with tissues remained functionally active for periods of at least 7 days.
Conclusions: The observation that an EPCR-dependent association of FVIIa with the endothelium is most pronounced soon after rFVIIa administration and subsequently declines temporally, combined with the retention of functionally active FVIIa in tissue homogenates for extended periods, indicates that FVIIa binding to EPCR on the endothelium facilitates the transport of FVIIa from circulation to extravascular tissues where TF resides.