Origin of yield stress and mechanical plasticity in model biological tissues

TL;DR

This paper investigates the mechanical plasticity and yield stress origins in biological tissues, revealing how tissues undergo large deformations through collective rearrangements akin to avalanches, with implications for predicting tissue stress.

Contribution

It introduces a computational and theoretical framework to understand tissue plasticity, highlighting the role of jamming transitions and collective rearrangements in large deformations.

Findings

Tissue jamming-unjamming transition varies with deformation degree.

Tissue rearrangements resemble avalanches governed by stress redistribution.

A simple model predicts tissue avalanches and mechanical stress from static images.

Abstract

During development and under normal physiological conditions, biological tissues are continuously subjected to substantial mechanical stresses. In response to large deformations cells in a tissue must undergo multicellular rearrangements in order to maintain integrity and robustness. However, how these events are connected in time and space remains unknown. Here, using computational and theoretical modeling, we studied the mechanical plasticity of epithelial monolayers under large deformations. Our results demonstrate that the jamming-unjamming (solid-fluid) transition in tissues can vary significantly depending on the degree of deformation, implying that tissues are highly unconventional materials. Using analytical modeling, we elucidate the origins of this behavior. We also demonstrate how a tissue accommodates large deformations through a collective series of rearrangements, which behave similarly to avalanches in non-living materials. We find that these tissue avalanches are governed by stress redistribution and the spatial distribution of vulnerable spots. Finally, we propose a simple and experimentally accessible framework to predict avalanches and infer tissue mechanical stress based on static images.