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Blood, 1 February 2006, Vol. 107, No. 3, pp. 980-986. Prepublished online as a Blood First Edition Paper on September 29, 2005; DOI 10.1182/blood-2005-07-2733.
Submitted July 11, 2005
Departments of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA * Corresponding author; email: stuart-lind{at}ouhsc.edu.
Tissue factor (TF) initiates blood coagulation, but its expression in the vascular space requires a finite period of time. We hypothesized that targeting exogenous tissue factor to sites of vascular injury could lead to accelerated hemostasis. Since phosphatidylserine (PS) is exposed on activated cells at sites of vascular injury, we cloned the cDNA for a chimeric protein consisting of the extracellular domain of TF (called soluble TF or sTF) and annexin V, a human PS-binding protein. Both the sTF and annexin V domains had ligand-binding activities consistent with their native counterparts, and the chimera accelerated Factor X activation by Factor VIIa. The chimera exhibited bi-phasic effects upon blood coagulation. At low concentrations it accelerated blood coagulation, while at higher concentrations it acted as an anticoagulant . The chimera accelerated coagulation in the presence of either unfractionated or low molecular weight heparins more potently than Factor VIIa, and shortened the bleeding time of mice treated with enoxaparin. The sTF-annexin V chimera is a targeted procoagulant protein that may be useful in accelerating thrombin generation where PS is exposed to the vasculature, such as may occur at sites of vascular injury or on within the vasculature of tumors.
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