A shape-driven reentrant jamming transition in confluent monolayers of synthetic cell-mimics

TL;DR

This study demonstrates that cell shape alone can induce a re-entrant jamming transition in synthetic cell monolayers, independent of density, highlighting the role of geometry in tissue fluidization.

Contribution

It provides experimental evidence that cell shape dynamics can drive jamming transitions without density changes, supported by synthetic cell-mimic systems.

Findings

Re-entrant jamming transition driven by cell shape

Shape variability constrained in confluent monolayers

Fast cells exhibit suppressed shape variability due to transient confinement

Abstract

Many critical biological processes, like wound healing, require confluent cell monolayers/bulk tissues to transition from a jammed solid-like to a fluid-like state. Although numerical studies anticipate changes in the cell shape alone can lead to unjamming, experimental support for this prediction is not definitive because, in living systems, fluidization due to density changes cannot be ruled out. Additionally, a cell's ability to modulate its motility only compounds difficulties since even in assemblies of rigid active particles, changing the nature of self-propulsion has non-trivial effects on the dynamics. Here, we design and assemble a monolayer of synthetic cell-mimics and examine their collective behaviour. By systematically increasing the persistence time of self-propulsion, we discovered a cell shape-driven, density-independent, re-entrant jamming transition. Notably, we observed cell shape and shape variability were mutually constrained in the confluent limit and followed the same universal scaling as that observed in confluent epithelia. Dynamical heterogeneities, however, did not conform to this scaling, with the fast cells showing suppressed shape variability, which our simulations revealed is due to a transient confinement effect of these cells by their slower neighbors. Our experiments unequivocally establish a morphodynamic link, demonstrating that geometric constraints alone can dictate epithelial jamming/unjamming.