Abstract
Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. To make quantitative predictions about glass transitions in tissues, we study a self-propelled Voronoi (SPV) model that simultaneously captures polarized cell motility and multi-body cell-cell interactions in a confluent tissue, where there are no gaps between cells. We demonstrate that the model exhibits a jamming transition from a solid-like state to a fluid-like state that is controlled by three parameters: the single-cell motile speed, the persistence time of single-cell tracks, and a target shape index that characterizes the competition between cell-cell adhesion and cortical tension. In contrast to traditional particulate glasses, we are able to identify an experimentally accessible structural order parameter that specifies the entire jamming surface as a function of model parameters. We demonstrate that a continuum Soft Glassy Rheology model precisely captures this transition in the limit of small persistence times, and explain how it fails in the limit of large persistence times. These results provide a framework for understanding the collective solid-to-liquid transitions that have been observed in embryonic development and cancer progression, which may be associated with Epithelial-to-Mesenchymal transition in these tissues.
Highlights
Recent experiments have revealed that cells in dense biological tissues exhibit many of the signatures of glassy materials, including caging, dynamical heterogeneities, and viscoelastic behavior [1,2,3,4,5]
Solid lines illustrate the phase transition line identified by the structural order parameter q 1⁄4 3.813 as function of v0 and p0 for a large range of Dr values. (In Appendix B 2, we demonstrate that the structural transition line q 1⁄4 3.813 matches the dynamical transition line for all studied values of Dr.) In contrast to results for particulate matter [22], this figure illustrates that the glass transition lines meet at a single point (p0 1⁄4 3.81) in the limit of vanishing cell motility, regardless of persistence
We show that a minimal model for confluent tissues with cell motility exhibits glassy dynamics at constant density
Summary
Recent experiments have revealed that cells in dense biological tissues exhibit many of the signatures of glassy materials, including caging, dynamical heterogeneities, and viscoelastic behavior [1,2,3,4,5] These dense tissues, where cells are touching one another with minimal spaces in between, are found in diverse biological processes including wound healing, embryonic development, and cancer metastasis. Over the past 20 years these phenomena have been unified by “jamming phase diagrams” [13,14] Building on these successes, researchers have recently used self-propelled particle (SPP) models to describe dense biological tissues [15,16,17,18,19,20]. A similar model was introduced by Li and Sun [33], and cellular Potts models bridge this gap [34,35], glass transitions have not been carefully studied in any of these hybrid systems
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