Tissue fusion over non-adhering surfaces

TL;DR

This study demonstrates that tissue monolayers can close non-adherent areas via purse-string contraction, with active fluctuations playing a crucial role, and presents a stochastic model to describe this process.

Contribution

It provides the first systematic evidence that purse-string closure can occur over large non-adherent areas and introduces a quantitative model incorporating tissue fluctuations.

Findings

Monolayers can close large non-adherent areas via purse-string mechanism.

Active epithelial fluctuations are essential for purse-string closure.

A stochastic model accurately describes the dynamics of tissue fusion.

Abstract

Tissue fusion eliminates physical voids in a tissue to form a continuous structure and is central to many processes in development and repair. Fusion events in vivo, particularly in embryonic development, often involve the purse-string contraction of a pluricellular actomyosin cable at the free edge. However in vitro, adhesion of the cells to their substrate favors a closure mechanism mediated by lamellipodial protrusions, which has prevented a systematic study of the purse-string mechanism. Here, we show that monolayers can cover well-controlled mesoscopic non-adherent areas much larger than a cell size by purse-string closure and that active epithelial fluctuations are required for this process. We have formulated a simple stochastic model that includes purse-string contractility, tissue fluctuations and effective friction to qualitatively and quantitatively account for the dynamics of closure. Our data suggest that, in vivo, tissue fusion adapts to the local environment by coordinating lamellipodial protrusions and purse-string contractions.