Cell Shape Emerges from Motion

TL;DR

This study reveals that mobile epithelial cells in monolayers naturally exhibit a broad, positively-skewed distribution of cell shapes, which can be accurately modeled by a deformable particle model accounting for cell motion and force adaptation.

Contribution

The paper introduces a deformable particle model that explains the emergence of a broad shape parameter distribution in mobile cell monolayers, independent of initial cell shapes.

Findings

Cell shape distribution is broad and skewed in confluent monolayers.

The shape distribution is well-reproduced by the deformable particle model.

Cell shape variability arises from motion and force adaptation, not heterogeneity.

Abstract

We perform cell segmentation on images from experimental studies of confluent, mobile cells in epithelial monolayers and show that these systems possess a broad, positively-skewed shape parameter distribution $P(\mathcal{A})$, where $\mathcal{A}=p^2/4\pi a$, $p$ is the perimeter, and $a$ is area of each cell. $P(\mathcal{A})$ is peaked at a value higher than the typical shape parameter $\mathcal{A}^* \sim 1.15$ that occurs for randomly packed, static confluent cell monolayers. The distribution does not arise from a heterogeneous population of cells with different fixed $\mathcal{A}$, nor can it arise from cell shape fluctuations from strains below the elastic limit. Instead, we find that all cells in each monolayer sample $\mathcal{A}$ values that span the full shape parameter distribution. We develop a deformable particle model that allows cell perimeter to adapt to local forces during cell motion, and this model recovers $P(\mathcal{A})$ to within $5\%$ for both MDCK and HaCaT epithelial cell monolayers. These results emphasize that confluent epithelial monolayers of mobile cells generate a well-defined broad shape parameter distribution that is independent of the initial cell shapes.