Proliferating Nematic That Collectively Senses an Anisotropic Substrate

TL;DR

This paper investigates how proliferating elongated cells develop nematic order on anisotropic substrates, revealing a collective sensing mechanism that depends on cell density and substrate interaction, with implications for tissue growth.

Contribution

It introduces a continuum model capturing the competition between growth-driven and substrate-driven alignment in proliferating cell colonies on nematic substrates.

Findings

Global alignment occurs above a critical cell density.

The system jams at high density, halting proliferation and reorientation.

Proposed mechanisms include anisotropic traction forces and alignment perpendicular to density gradients.

Abstract

Motivated by recent experiments on growing fibroblasts, we examine the development of nematic order in a colony of elongated cells proliferating on a nematic elastomer substrate. After sparse seeding, the cells divide and grow into locally ordered, but randomly oriented, domains that then interact with each other and the substrate. Global alignment with the substrate is only achieved above a critical density, suggesting a collective mechanism for the sensing of substrate anisotropy. The system jams at high density, where both reorientation and proliferation stop. Using a continuum model of a proliferating nematic liquid crystal, we examine the competition between growth-driven alignment and substrate-driven alignment in controlling the density and structure of the final jammed state. We propose that anisotropic traction forces and the tendency of cells to align perpendicular to the direction of density gradients act in concert to provide a mechanism for collective cell alignment.