HYDRODYNAMIC INTERACTIONS/CELL DEFORMATION IN NEUTROPHIL

许多物理和生化因素共同控制炎症白细胞在微循环中的募集过程。虽然分子介质和血流动力学在白细胞粘附和外渗中的作用或多或少被单独理解，但这些因素之间复杂的非线性相互作用却鲜为人知。本项目致力于将影响白细胞招募率的多种因素，如微尺度血流动力学、白细胞变形和粘附受体的空间分布，整合到流动条件下细胞粘附的仿生实验和最先进的计算机模拟中。在Aim 1中，我们将对人类中性粒细胞进行流动粘附实验，这些中性粒细胞流经具有圆形截面和选择涂层表面的微制造分支导管，以了解其物理特性

Many physical and biochemical factors combine to control the process of inflammatory leukocyte recruitment in the microcirculation. While the roles of molecular mediators and hemodynamics on leukocyte adhesion and extravasation are more or less understood individually, the complex, nonlinear interaction between these factors is less so. This project focuses on integrating multiple factors affecting rates of leukocyte recruitment such as microscale hemodynamics, leukocyte deformation, and spatial distributions of adhesion receptors, into biomimetic experiments and state-of-the-art computer simulations of cell adhesion under flow. In Aim 1 we will conduct flow adhesion experiments with human neutrophils flowing through microfabricated branching conduits with circular cross-section and selectin-coated surfaces, to understand the physics of leukocyte margination and rolling throughout the microvascular network. These results will be compared to theoretical predictions of an improved version of multiparticle adhesive dynamics and ultimately to in vivo experiments in mouse models of inflammation. In Aim 2 we will further extend the computer simulation to consider viscoelastically deforming neutrophils and the role of cell flattening in stabilizing selectin and integrin-mediated adhesion to the endothelium. The theoretical model will be validated with micropipette experiments of neutrophil compression under various cytoskeletal modifiers, and then used to help interpret flow chamber adhesion experiments to selectin and integrin-presenting surfaces where the contact area under rolling neutrophils is measured by viewing interactions from the side. These studies will address our hypothesis that cell flattening acts to stabilize rolling adhesion and that downregulation of either neutrophil or substrate adhesion receptors can disrupt this stabilization. Finally, in Aim 3 we will use microcontact printing methods to systematically study how relative spatial distributions of selectin and integrin ligand molecules on model endothelium act to control the dynamics of leukocyte adhesion and the ultimate location of leukocyte firm arrest. The proposed work of this project will use engineering methods to integrate current knowledge of leukocyte-endothelial interactions into a more complete picture of inflammation in vivo.