Flow, fluctuate and freeze: Epithelial cell sheets as soft active matter*

Epithelial cell sheets form a fundamental role in the developing embryo, and also in adult tissues including the gut and the cornea of the eye. Soft and active matter provides a theoretical and computational framework to understand the mechanics and dynamics of these tissues.
I will start by introducing the simplest useful class of models, active brownian particles (ABPs), which incorporate uncoordinated active crawling over a substrate and mechanical interactions. Using this model, I will show how the extended ’swirly’ velocity fluctuations seen in sheets on a substrate can be understood using a simple model that couples linear elasticity with disordered activity. We are able to quantitatively match experiments using in-vitro corneal epithelial cells. Adding a different source of activity, cell division and apoptosis, to such a model leads to a novel 'self-melting' dense fluid state. I will then directly apply this simple particle-based model to explain the steady-state spiral flow pattern on the mouse cornea.