Mater_Material Approaches to active tissue mechanics

Communities of epithelial cells demonstrate close intercellular communications and highly ordered coordination in their motility. In the cohort, each cells are constitutive energy-consuming agents and they generate forces and interact with others via cell-cell junctions. The force rebalancing within the population that can be invoked by various external stimuli and endogenous cellular events then leads to self-adjustment of tissue internal contractile stresses and organization, concomitant with distinct overall dynamics. To unveil the mechanisms of various tissue dynamics, it is required to understand how epithelia decode environmental inputs into mechanical principles that underpinned many vital biological processes, including homeostasis, morphogenesis, and metastasis. Thus, significant interdisciplinary efforts have recently been made towards coupling cellular milieus with the latest advent of materials science and microengineering techniques to create controllable arenas for epithelial studies. By modulating the mechanical contacts at cell/material interfaces, researchers can study aspects of in vivo epithelial dynamics and how tissues regulate mechanosensing mechanisms. In this review, we summarize the state-of-the-art material methodologies to mimic in vivo conditions and study epithelial mechanics. Especially, we discuss tissues as active materials and try to understand tissue rheological properties and active behaviors at different length scales. We further focus on the interdisciplinary study of the active, emergent mechanical properties of tissue and its complex interface with the microenvironment