Multicellular rosettes drive fluid-solid transition in epithelial tissues

TL;DR

This paper investigates how multicellular rosettes influence tissue mechanics, revealing a fluid-solid transition driven by rosette density and tensions, with critical phenomena akin to phase transitions.

Contribution

It introduces a generalized vertex model and effective medium theory to demonstrate the role of rosettes in tissue rigidity and elucidates the nature of rigidity transitions in biological tissues.

Findings

Rosette density controls tissue rigidity.

A second-order phase transition characterizes the fluid-solid change.

Universal critical scaling near the transition point.

Abstract

Models for confluent biological tissues often describe the network formed by cells as a triple-junction network, similar to foams. However, higher order vertices or multicellular rosettes are prevalent in developmental and {\it in vitro} processes and have been recognized as crucial in many important aspects of morphogenesis, disease, and physiology. In this work, we study the influence of rosettes on the mechanics of a confluent tissue. We find that the existence of rosettes in a tissue can greatly influence its rigidity. Using a generalized vertex model and effective medium theory we find a fluid-to-solid transition driven by rosette density and intracellular tensions. This transition exhibits several hallmarks of a second-order phase transition such as a growing correlation length and a universal critical scaling in the vicinity a critical point. Further, we elucidate the nature of rigidity transitions in dense biological tissues and other cellular structures using a generalized Maxwell constraint counting approach. This answers a long-standing puzzle of the origin of solidity in these systems.