Biological & Soft Matter Seminar: From Contraction Waves to Active Resistance to Rupture – Extreme Epithelial Dynamics in Placozoa

Abstract:

Recently we reported our discovery of fast contraction dynamics in the epithelium of the basal animal Trichoplax Adhaerens (Placozoa). This not well-known model system has extreme advantages, being the simplest known living animal, made of mono-layered epithelia, practically in 2D. We image the animal tissue in vivo, using high resolution tracking microscopy. We observe and quantify phenomena like: dynamic stiffness, extreme strains, cell shapes and sizes, and spatio-temporal activity patterns, including contraction waves. Following these observations, I present a model of tissues as sheets of excitable/oscillatory cells. The model can explain the dynamic contraction patterns we see, but it also predicts excitation in response to stress and dynamic resistance to rupture by elimination of stress and strain localizations. In the talk I will present both the experimental observations and the model results. This model of “Active Cohesion” may have implications on any epithelial tissue, on possible manufacturing of synthetic active materials, and on models of evolution of multicellularity.