A density-independent reentrant jamming transition in confluent monolayers of synthetic cell-mimics

In assemblies of rigid particles, increasing the packing fraction can drive the transition from a fluid-like to a jammed solid-like state. However, in crucial biological processes such as wound healing, this dynamic arrest occurs while maintaining confluence, with the packing fraction remaining unity. This remarkable feature of cell monolayers is possible because cells are deformable objects and the constraining effects of high density are easier to overcome via changes in the cell shape. Furthermore, recent experimental and theoretical studies suggest that cell shape fluctuations, discarded as experimental noise until now, correlate with dynamics. In this study, we design and assemble a monolayer of synthetic cell-mimics. Our investigation revealed a density-independent re-entrant jamming transition driven by the shape of cells, on increasing activity. We observe that cell shape variability in our synthetic system mimics those seen in confluent cell monolayers and are mutually constrained and follow the same universal scaling as that observed in confluent epithelia. However, we have identified a deviation from this scaling behaviour for the fast-moving cells, which exhibit suppressed shape variability. Our simulations attribute this reduced shape variability to a temporary confinement effect imposed by slower neighbouring cells. Our synthetic model system allows precise manipulation of both activity and deformability and facilitates a direct comparison with theoretical and numerical predictions.