Re-entrant dynamics in cell collectives under activity tuning

Determine whether dense cell collectives at fixed packing fraction exhibit non-intuitive dynamical behavior, including re-entrant dynamics, when activity is tuned (for example, by varying the persistence time of self-propulsion), analogous to the behavior observed in assemblies of rigid self-propelled particles.

Background

In dense assemblies of rigid self-propelled particles, tuning the activity at constant density can lead to non-intuitive dynamical phenomena such as re-entrant behavior. Whether analogous behavior occurs in living or model cell collectives has been unclear because biological systems generally lack a straightforward knob to systematically tune activity without simultaneously altering other complicating factors such as division, apoptosis, or adhesion.

The paper introduces a synthetic model system of deformable, self-propelled cell-mimics that permits controlled tuning of activity and explores collective dynamics near confluence. The authors highlight that prior to such controllable systems, it was unknown if similar re-entrant physics manifests in cell collectives when activity is varied at fixed density.

References

Even for the simpler case of rigid self-propelled particles, tuning the activity at constant density results in non-intuitive behavior, such as re-entrant dynamics , and it is unknown whether similar physics is at play in cell collectives, since, here, the means to tune activity systematically are not available.

— A shape-driven reentrant jamming transition in confluent monolayers of synthetic cell-mimics  (2401.13437 - Arora et al., 2024) in Introduction, paragraph 3 (preceding the subsection 'Making deformable cell-mimics with tunable activity')

Although the precise location of the glass transition remains yet to be determined, these results suggest that cell activity, represented by self-propulsion in the present model, is a dominant factor controlling the vitrification of dense HeLa cell collectives.

— Dense HeLa cell monolayers remain liquid-like despite strong crowding  (2609.18768 - Pal et al., 16 Sep 2026) in Discussion section