(391f) Intra-Thrombus Transport and Local Shear Stress Distributions Modeling Based On In-Vivo Imaging with Single Platelet Resolution

Stalker, T. J., University of Pennsylvania
Brass, L. F., University of Pennsylvania
Diamond, S. L., University of Pennsylvania

The assembly of platelet deposits and fibrin polymerization results in over one million heart attacks and strokes each year in the US. Conversely, deficiencies in these processes result in bleeding risks that confront surgeons on a regular basis. In order to quantify thrombus formation and thrombus break-up, it is necessary to first measure the thrombus structure and the biological and physical factors controlling structure. Recent findings from in-vivo laser injury studies demonstrate that the structure of the thrombus is non-uniform with the porosity varying as a function of both time and space. Also, the flow field around a growing thrombus exerts forces on the cells that make up the thrombus, thereby straining the thrombus mechanically. The former phenomenon affects intra-thrombus chemo-dynamics, while the latter affects clot mechanics. Therefore, the overall objective of this work is to develop a framework for fundamental understanding of thrombogenesis and the role that both mechanical and chemical cues play in determining the thrombus structure and integrity.

In-vivo laser injury experiments in mice are performed in order to image thrombus formation and platelet activation in 3D using confocal fluorescent microscopy. Optical Doppler velocimetry is used in order to measure the centerline flow velocity in the mouse blood vessels. The rigidity of the platelet aggregates and the strength of their binding to each other are varied by blocking actin and fibrin polymerization, respectively. Porosity of the platelet aggregates is controlled by inhibiting platelet activation via blocking thrombin function or fibrin polymerization. Local stress fields within thrombi structures are calculated via flow dynamics. Inhibitors of platelet activation pathways, fibrin polymerization, and clot retraction are used in order to chemically vary the structure of the thrombus. Once the thrombus structure and the platelet activation states are measured, chemo-transport simulations are performed in order to calculate permeability, fluxes and diffusivities of the key soluble species within the thrombus.

The presented innovative multidisciplinary approach is expected to yield an enhanced fundamental understanding of how thrombus structure is affected by mechano- and chemo-perturbations. Collectively, the outcome of this work is expected to provide insight towards understanding clot generation, structure and stability relevant to thrombosis, thromboembolism and coagulopathy, ideally to reduce risks of occlusion and embolism. Moreover, it is planned to perform a similar analysis for in-vitro platelet aggregation in microfluidic chambers, as such systems provide for greater experimental control and more accessible imaging.