Defect-mediated morphologies in growing cell colonies

TL;DR

This study models how topological defect dynamics influence the shape and morphology of growing cell colonies, revealing the role of cell division, substrate friction, and defect-interface interactions in morphological regulation.

Contribution

It introduces a theoretical framework using active gel equations to connect defect dynamics with colony shape changes during growth.

Findings

Friction drives colonies toward more isotropic shapes.

Defects interact with the interface within a specific vorticity length scale.

Cells reorient parallel to the interface due to active stresses.

Abstract

Morphological trends in growing colonies of living cells are at the core of physiological and evolutionary processes. Using active gel equations, which include cell division, we show that shape changes during the growth can be regulated by the dynamics of topological defects in the orientation of cells. The friction between the dividing cells and underlying substrate drives anisotropic colony shapes toward more isotropic morphologies, by mediating the number density and velocity of topological defects. We show that the defects interact with the interface at a specific interaction range, set by the vorticity length scale of flows within the colony, and that the cells predominantly reorient parallel to the interface due to division-induced active stresses.