Adherent cells in vivo often reside on basement membranes which are thin, sheet-like specialized extracellular matrices that function as cellular anchorage sites, physical barriers, and signaling hubs. An important physical attribute of basement membranes is their three-dimensional topography due to the complex microstructural organization of their constituent proteins. This topography takes the form of an intricate network of fibers and pores with characteristic dimensions on the order of 100 nm on top of which lies a larger, micron-scale topography in the form of anisotropic undulations. Various types of engineered microstructured substrates have been developed to study the impact of topographical cues on cellular structure and function in vitro. One such system that we have been using is a substrate that consists of arrays of microgrooves that are intended to mimic the anisotropic organization of the basement membrane and on which cells can be directly cultured.

Our studies of the effect of substrate topography on cellular structure and function have focused principally on the vascular endothelium, the monolayer of cells lining the inner surfaces of all blood vessels. In medium and large arteries, chronic endothelial inflammation is a trigger for atherosclerosis, the disease that leads to heart attacks and strokes. Interestingly, atherosclerotic lesions develop preferentially in arterial regions where endothelial cells are cuboidal and randomly oriented, whereas arterial zones that are characterized by highly elongated and aligned endothelial cells remain largely spared from the disease. Therefore, understanding the relationships between endothelial cell shape/alignment and function is of fundamental interest, a question that we are tackling using topographic microgroove substrates.

In this presentation, I will discuss four aspects of endothelial cell responsiveness to microgroove substrates and highlight opportunities for computational modeling in each of these aspects. First, I will show how microgroove substrates can be used to noninvasively control endothelial cell shape and alignment and will describe our understanding of the mechanisms that underlie cell shape regulation by microgrooves. Second, I will describe dynamic live-cell recordings that demonstrate that microgrooves can orient the direction of migration of endothelial cells within monolayers and can lead to a unique pattern of collective cell migration that takes the form of antiparallel streams. Modeling the endothelial monolayer as an active fluid with the effect of the microgrooves considered as an energetic constraint on cell orientation predicts the emergence of the antiparallel streams as well as the dimensions of these streams. Third, I will show how microgrooves lead to extensive deformation of endothelial cells and their nuclei and will evoke the interesting notion of using these deformations to diagnose certain diseases that involve abnormalities in cellular and nuclear mechanical properties. Finally, I will describe the competition between microgroove-derived contact stresses on the cells’ basal surface with flow forces on the cells’ apical surface and how this competition is a key determinant of endothelial cell shape and alignment.