Systems Biology of Coagulation Initiation: Kinetics of Thrombin Generation in Resting and Activated Human Blood

Abstract

Blood function defines bleeding and clotting risks and dictates approaches for clinical intervention. Independent of adding exogenous tissue factor (TF), human blood treated in vitro with corn trypsin inhibitor (CTI, to block Factor XIIa) will generate thrombin after an initiation time (Ti) of 1 to 2 hours (depending on donor), while activation of platelets with the GPVI-activator convulxin reduces Ti to ∼20 minutes. Since current kinetic models fail to generate thrombin in the absence of added TF, we implemented a Platelet-Plasma ODE model accounting for: the Hockin-Mann protease reaction network, thrombin-dependent display of platelet phosphatidylserine, VIIa function on activated platelets, XIIa and XIa generation and function, competitive thrombin substrates (fluorogenic detector and fibrinogen), and thrombin consumption during fibrin polymerization. The kinetic model consisting of 76 ordinary differential equations (76 species, 57 reactions, 105 kinetic parameters) predicted the clotting of resting and convulxin-activated human blood as well as predicted Ti of human blood under 50 different initial conditions that titrated increasing levels of TF, Xa, Va, XIa, IXa, and VIIa. Experiments with combined anti-XI and anti-XII antibodies prevented thrombin production, demonstrating that a leak of XIIa past saturating amounts of CTI (and not “blood-borne TF” alone) was responsible for in vitro initiation without added TF. Clotting was not blocked by antibodies used individually against TF, VII/VIIa, P-selectin, GPIb, protein disulfide isomerase, cathepsin G, nor blocked by the ribosome inhibitor puromycin, the Clk1 kinase inhibitor Tg003, or inhibited VIIa (VIIai). This is the first model to predict the observed behavior of CTI-treated human blood, either resting or stimulated with platelet activators. CTI-treated human blood will clot in vitro due to the combined activity of XIIa and XIa, a process enhanced by platelet activators and which proceeds in the absence of any evidence for kinetically significant blood borne tissue factor.

Multiscale prediction of patient-specific platelet function under flow

“…38 Our results indicate that cAMP elevation is more effective than COX-1 or P2Y 1 inhibition under these conditions. The multiscale and patient-specific modeling presented here extends earlier modeling efforts of platelet function and/or coagulation 20,21,[39][40][41][42] by including a highly robust description of intracellular platelet signaling through GPVI, P2Y 1 , TP, and IP. To our knowledge, our NN/multiscale model is the first such approach to make donor-specific predictions of platelet function under flow in the presence of both released ADP and thromboxane and pharmacologic modulators of clinical relevance.…”

A Short Review of Advances in the Modelling of Blood Rheology and Clot Formation

“…While some new models in blood rheology (notably the ones in [18,20,23]) have appeared, the thrust of development is in simulation of such models in the complex geometries of the vasculature/medical devices through which blood flows. With regard to clot formation, the acceptance of in silico tests for the generation of hypotheses by an influential section of the biochemical community (see Mann [51]) has meant increasingly comprehensive single-scale models of coagulation (notably the ones in [36,37]). Simultaneously, with our understanding of in vivo coagulation evolving from the "cascade" model into a 'three-stage multi-scale process made functional by flow', multi-scale models of coagulation have been developed (notably the ones in [40,41,48]), simulated in the presence of flow, and their predictions verified with experimental hypotheses.…”

“…Luan et al [35] used a single scale heterogeneous model to show that mathematically-determined points of fragility coincided with clinical data, and thus advocated the use of such models for determining therapeutic targets. Chatterjee et al [36] extended the model of [30] and developed a single-scale pseudo-homogeneous model that captured the clot initiation that occurred in blood even when treated with corn trypsin inhibitor (Corn trypsin inhibitor is used to block the contact pathway of coagulation). Susree and Anand [37] combined elements of the models in [30,32,34] to come up with a single scale pseudo-homogeneous model which showed that inhibition of platelet activation by other platelets had a much more significant effect on thrombin production than inhibition of platelet activation by thrombin.…”

Dynamic Modeling of the Human Coagulation Cascade Using Reduced Order Effective Kinetic Models

“…Mechanistic ODE coagulation models from our laboratory [23,24] were built upon the earlier studies of Jones and Mann [25], Hockin et al [26], and later Butenas et al [27] who developed and then subsequently refined highly mechanistic coagulation models. Other laboratories have also expanded upon Hockin et al for example by exploring the intrinsic pathway, the role of stochastic fluctuations in coagulation [28], and the dynamics of thrombin mediated clot formation [29] and fibrinolysis [30]. Other aspects of coagulation have also been modeled, such as platelet biochemistry [31], multi-scale models of clot formation [32,33], and transport inside clots [34].…”