Topological Defects in Cell Monolayers Guided by Topography

Many types of cells display long-range alignment like nematic liquid crystals (LCs), and have topological defects. These defects are characterized by their topological charge, the number of rotations of the alignment around the defect. In 2D cell culturing, only +/- 1/2 defects are typically observed, although other defects exist in living systems. Topological defects in cell layers have been associated with increase in cell apoptosis [1] and clustering [2]. We induce alignment of cells via contact guidance into formations that impose arbitrary topological charges. We survey multiple cell types (EpH-4 and 3T6) to characterize their alignment, density, and dynamics near defects of various topological charges, and define LC parameters such as defect core sizes and elastic constants. We observe a large change in density of fibroblasts (3T6) near the topological defects , where our tunable confinement allows us to identify the isotropic defect cores.
[1] TB Saw et al. Nature 544, 212 (2017)
[2] K Kawaguchi et al. Nature 545, 327 (2017)