Active nematics with deformable particles

TL;DR

This paper extends the hydrodynamic theory of active nematics to include deformable cells, revealing how cell shape changes influence tissue flows and defect dynamics in active biological tissues.

Contribution

It introduces a continuum model incorporating cell deformability into active nematic theory, highlighting the role of active stress in driving tissue-scale flows.

Findings

Deformable cells can generate sufficient active stress to induce tissue flows.

A threshold active stress leads to coexistence of elongated and isotropic cell regions.

The model predicts steady states with dynamic cell shape and flow patterns.

Abstract

The hydrodynamic theory of active nematics has been often used to describe the spatio-temporal dynamics of cell flows and motile topological defects within soft confluent tissues. Those theories, however, often rely on the assumption that tissues consist of cells with a fixed, anisotropic shape and do not resolve dynamical cell shape changes due to flow gradients. In this paper we extend the continuum theory of active nematics to include cell shape deformability. We find that circular cells in tissues must generate sufficient active stress to overcome an elastic barrier to deforming their shape in order to drive tissue-scale flows. Above this threshold the systems enter a dynamical steady-state with regions of elongated cells and strong flows coexisting with quiescent regions of isotropic cells.