Epithelial colonies in vitro elongate through collective effects

Epithelial tissues of the developing embryos elongate by different mechanisms, such as neighbor exchange, cell elongation, and oriented cell division. Since autonomous tissue self-organization is influenced by external cues such as morphogen gradients or neighboring tissues, it is difficult to distinguish intrinsic from directed tissue behavior. The mesoscopic processes leading to the different mechanisms remain elusive. Here, we study the spontaneous elongation behavior of spreading circular epithelial colonies in vitro. By quantifying deformation kinematics at multiple scales, we report that global elongation happens primarily due to cell elongations, and its direction correlates with the anisotropy of the average cell elongation. By imposing an external time-periodic stretch, the axis of this global symmetry breaking can be modified and elongation occurs primarily due to orientated neighbor exchange. These different behaviors are confirmed using a vertex model for collective cell behavior, providing a framework for understanding autonomous tissue elongation and its origins.

Automated summary

The study shows that the elongation of epithelial tissues in vitro is primarily caused by cell elongation, and the direction of elongation is correlated with the anisotropy of cell elongation. By applying an external periodic stretch, the axis of global symmetry breaking can be modified, leading to elongation primarily due to oriented neighbor exchange. A vertex model for collective cell behavior is used to confirm these different behaviors, providing a framework for understanding autonomous tissue elongation and its origins.