Research Highlights: Dynamics on Curved Surfaces

Epithelial tissues in the body are rarely flat — yet most theoretical models of the unjamming transition (UJT) have assumed planar geometry. We lift this restriction by embedding a vertex model on a spherical surface, and find that curvature itself is a powerful driver of tissue fluidization: higher curvature lowers the energy barriers to cellular rearrangement, promoting cell intercalation, mobility, and self-diffusivity. A striking consequence is that small epithelial structures are naturally malleable and migratory, while larger ones become progressively more rigid — a curvature-driven rigidity that emerges purely from geometry. This work introduces an extended phase diagram in which cell shape, motility, and tissue curvature jointly determine whether an epithelial layer flows or stays put, establishing curvature-induced unjamming as a fundamentally new mechanism for epithelial plasticity with direct relevance to wound healing, development, and regeneration.

Using human lung alveolospheres as a model system, we show that cells collectively sense the curvature of their environment — and that this sensing has real consequences for tissue organization and fluidity. As curvature increases, cell motion becomes less coordinated, with hexagonal solid-like clusters giving way to fluid-like regions that enhance overall tissue mobility. During alveolosphere growth, cells also exhibit a striking packing transition: with stiffer nuclei surrounded by more deformable cell bodies, increasing the nucleus-to-cell size ratio drives an organization from disordered, gas-like arrangements toward hexagonal packing. Curvature and nuclear geometry thus emerge as unexpected regulators of tissue state, with likely implications for organ development and maturation. (In collaboration with Prof. Ming Guo, MIT)