Large-scale synchronized temporal oscillation in epithelial collectives

Collective cell migration presents a promising field for the application of non-equilibrium physics, exposing a variety of phenomena including pattern formation, glassy dynamics, and active turbulence. The underlying physics offers a fresh viewpoint for understanding structural and functional properties of epithelia. Despite numerous studies on the spatial patterns of cell migration, the temporal dynamics have been largely overlooked. Here, we investigate the sustained expansion and contraction of cell packs emerging within epithelia, showing temporally semi-periodic velocity divergence. By extracting the phase from divergence field, we observe surprisingly large-scale oscillatory patterns that resemble bioelectrical signals reported in the heart and brain. Interestingly, the divergence phase dynamics in a developing epithelium shows density-dependent synchronization and de-synchronization behaviors, which align with the epithelial jamming transition. Furthermore using the breast cancer models, we see stronger persistence and fewer topological defects in phase evolution when cancer cells become more malignant. As we forge ahead, such temporal analysis has the potential to assess tissue developmental processes, to distinguish healthy and diseased tissues, and to provide a new perspective for histology.