Blood flow controls coagulation onset via the positive feedback of factor VII activation by factor Xa
1 National Research Center for Hematology, 4a Novyi Zykovskii pr., Moscow 125167, Russia
2 Albert Eye Research Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
3 Center for Theoretical Problems of Physicochemical Pharmacology, 4 Kosygina str., Moscow 119991, Russia
4 Department of Physics, Moscow State University, 1 Vorobyevy gory, Moscow 119991, Russia
BMC Systems Biology 2010, 4:5 doi:10.1186/1752-0509-4-5Published: 26 January 2010
Blood coagulation is a complex network of biochemical reactions, which is peculiar in that it is time- and space-dependent, and has to function in the presence of rapid flow. Recent experimental reports suggest that flow plays a significant role in its regulation. The objective of this study was to use systems biology techniques to investigate this regulation and to identify mechanisms creating a flow-dependent switch in the coagulation onset.
Using a detailed mechanism-driven model of tissue factor (TF)-initiated thrombus formation in a two-dimensional channel we demonstrate that blood flow can regulate clotting onset in the model in a threshold-like manner, in agreement with existing experimental evidence. Sensitivity analysis reveals that this is achieved due to a combination of the positive feedback of TF-bound factor VII activation by activated factor X (Xa) and effective removal of factor Xa by flow from the activating patch depriving the feedback of "ignition". The level of this trigger (i.e. coagulation sensitivity to flow) is controlled by the activity of tissue factor pathway inhibitor.
This mechanism explains the difference between red and white thrombi observed in vivo at different shear rates. It can be speculated that this is a special switch protecting vascular system from uncontrolled formation and spreading of active coagulation factors in vessels with rapidly flowing blood.