Bridging microscopic cell dynamics to nematohydrodynamics of cell monolayers

TL;DR

This paper introduces a cell-based phase-field model linking microscopic cell mechanics to large-scale nematic and hydrodynamic behaviors in cell monolayers, capturing instabilities and defect dynamics.

Contribution

It presents a minimal, analytically tractable model that reproduces key active matter instabilities and characterizes flow and defect patterns in cell tissues.

Findings

Reproduces bend and splay instabilities of active nematic tissues.

Quantifies flow and defect structures for different stress mechanisms.

Shows activity-induced heterogeneity and gap formation in monolayers.

Abstract

It is increasingly being realized that liquid-crystalline features can play an important role in the properties and dynamics of cell monolayers. Here, we present a cell-based model of cell layers, based on the phase-field formulation, that connects mechanical properties at the single cell level to large-scale nematic and hydrodynamic properties of the tissue. In particular, we present a minimal formulation that reproduces the well-known bend and splay hydrodynamic instabilities of the continuum nemato-hydrodynamic formulation of active matter, together with an analytical description of the instability threshold in terms of activity and elasticity of the cells. Furthermore, we provide a quantitative characterisation and comparison of flows and topological defects for extensile and contractile stress generation mechanisms, and demonstrate activity-induced heterogeneity and spontaneous formation of gaps within a confluent monolayer. Together, these results contribute to bridging the gap between micro-scale cell dynamics and tissue-scale collective cellular organisation.