Epithelial Cell Mechanobiology in Mechanically Heterogeneous Microenvironments - PROJECT SUMMARY Epithelial tissues are multilayered with varying elasticity and geometry in different layers, e.g., gut epithelium, lungs, or skin. Cells aggregate or migrate in different regions of tissues, as needed for various biological demands of disease and development, by sensing and responding to both mechanical and biochemical properties of their extracellular matrix (ECM). In wound healing, tumor invasion, and embryogenesis, epithelial leader cells generate mechanosensitive protrusions and coordinate their forces with follower cells for directed migration to fill gaps and voids in epithelial layers and tissues. This transmission of forces and mechanotransduction signaling spans across length scales, from cell-ECM adhesions, cell-cell junctions, and cytoskeletal network into the nucleus. We have shown that epithelial cells mechanosense extracellular matrix (ECM) stiffness, confinement, and fiber architecture. Building on these classic mechanobiology studies, we have also shown that epithelial cells store mechanical memory of their past environments, which informs their future migration and generates matrix memory through active remodeling of 3D collagen microenvironments. Additionally, disruption of nuclear export imparts concurrent epithelial and mesenchymal states. However, there are significant gaps in knowledge about how epithelia sense tissue defects and wounds, whether the force requirement for cell migration changes with environment topography, and how nuclear mechanosensing causes disorder in epithelia. These gaps in knowledge require novel bioengineering approaches to decouple these multivariate problems. In this MIRA program, we will study epithelial mechanosensing, response, and memory in three broad areas. First, we study how epithelial cells sense extracellular wounds of varying collagen types and matrix stiffness, and how cytoskeletal reinforcement and depth-mechanosensing overcome and heal ECM wounds. Second, we examine whether the classic force-dependent fast epithelial migration can occur with lower forces by changing ECM fiber alignment, and how spatiotemporal coordination of extracellular force transmission and intercellular mechanotransduction governs such force-effective migration. Third, we connect dysfunctions in nuclear transport and nucleocytoplasmic communication to epithelial disorder, unjamming, and migration. In these projects, we also ask whether epithelial cells remember their past extracellular stimuli and whether such memory alters their future response. These projects bring novel mechanobiology perspectives to conventional epithelial biology and could reveal new responses at different time and length scales, such as mechanical memory, depth-sensing, and epithelial transitions through nuclear mechanics. This work employs and nurtures diverse perspectives due to its inherently multidisciplinary approach in biophysics, engineering, and cell biology. Our results will highlight how the mechanically complex extracellular environments proactively regulate epithelial mechanosensing and may inform new insights and therapies for dysfunctional embryonic development, cancer, injury response, and wound healing.
