Intra-Thrombus Chemo-Transport and Local Stress Mechanics under Flow

While thrombosis and thromboembolism underlie over a million heart attacks or strokes each year, little is known about transport of proteins within platelet deposits or the signaling events that control the mechanical stability of platelet deposits. Intrathrombic transport of ADP, TXA2, or thrombin controls the thrombus growth rate. Embolism is dictated by both structural and biological factors that are established during the deposition of platelets under flow conditions. Recent evidence has indicated that the thrombus porosity varies as a function of both time and space. Therefore, the overall objective of this proposal is to develop a framework for fundamental understanding of thrombogenesis and the role that mechanical and chemical cues play in determining the thrombus structure and integrity. The 1st aim of this project is to investigate the interplay between thrombus porosity and the biochemical transport occurring within it. In-vivo mice experiments will be performed to image thrombus formation and platelet activation in 3D using fluorescent confocal microscopy. Inhibitors of platelet activation pathways, fibrin polymerization, and clot retraction will be used in order to chemically vary the structure of the thrombus. Once the thrombus structure (porosity, pore size distribution, platelet-platelet contact area per unit volume) and the platelet activation states (granule release, integrin activation, phosphatidylserine exposure) are measured, chemo-transport simulations will be performed using Lagrangian Scalar Tracking in order to calculate permeability, fluxes and diffusivities of the key soluble species within the thrombus. The 2nd aim of this project is to investigate in-vitro how the structure and integrity of a blood clot depend on mechanical interactions of platelets with their surroundings and with each other. The rigidity of the platelets and the strength of their binding to each other will be varied by blocking actin and fibrin polymerization, respectively. Porosity of the platelet aggregate will be controlled by inhibiting platelet activation via blocking thrombin function or fibrin polymerization. Local stress fields within thrombi structures will be calculated via Lattice Boltzmann Method flow dynamics. The knowledge obtained from this proposal will further the capability of controlling the thrombus structure thereby advancing blood clotting disorder treatments, regardless of whether the problem is excessive or inadequate clotting. (AHA Program: Postdoctoral Fellowship)