Newer concepts of blood coagulation

TLDR

The study aims to develop an in vitro model of blood coagulation that closely mimics in vivo conditions. The model employs an in vitro system that replicates the physiological coagulation environment. The model demonstrates that the tissue factor–factor VIIa complex initiates coagulation by activating factor IX and X, that factor Xa and IXa then drive distinct steps leading to a thrombin burst on platelets, and that thrombin can activate factor XI independently of factor XII, which further amplifies thrombin generation. Summary.

Abstract

Summary. In this report we describe an in vitro model of blood coagulation reactions that mimics as closely as possible the in vivo condition. Our model indicates that the tissue factor—factor VIIa complex initiates coagulation by activating small amounts of both factor IX and factor X in the environment of the tissue factor bearing cell. Factor Xa and factor IXa formed in the initial reaction then play very distinct roles in the subsequent interactions of the clotting mechanism leading to a burst of thrombin generation on the platelet surface. Our results also indicate that factor XI can be activated by thrombin in the absence of factor XII and that the function of factor XI is simply to enhance conversion of factor IX to factor IXa resulting in enhanced thrombin generation on the platelet surface.