Endothelial and Hematopoietic Tissue Factor Are Unnecessary in Two Mouse Models of Hemostasis and Thrombosis

Endothelial and hematopoietic tissue factor are unnecessary in two mouse models of hemostasis and thrombosis

Tissue Factor (TF), in combination with Factor VII, activates the extrinsic coagulation pathway leading to thrombin generation and clot formation. TF is expressed by epithelial, smooth muscle and perivascular cells; in addition endothelial and hematopoietic cells can express TF, especially in response to inflammatory stimuli. Despite extensive studies the exact cellular source of TF during clot initiation and propagation has not yet been clearly identified, and the importance of endothelial or hematopoietic TF in hemostasis and thrombosis is unknown. To address the latter, we measured bleeding time and arterial thrombus formation in TF flox/flox: Tie-2p/e Cre conditional mice, in which endothelial and circulating TF expression is absent. We observed that TF deficiency in the endothelial and hematopoietic compartment was not associated with defective hemostasis. In a FeCl3- induced carotid injury model, in contrast to PAR4 null mice, clotting in TF conditional mice did not significantly differ from that of wild type littermates. This study suggests that TF derived from endothelial or blood cells is not necessary for hemostasis and thrombosis in the models studied.

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