Hexatic phase in a model of active biological tissues

Area of Science:

• Biophysics
• Cell Biology
• Soft Matter Physics

Background:

• Cellular tissues undergo transitions between solid and fluid states during biological processes like wound healing.
• The epithelial-to-mesenchymal transition describes a shift from a rigid to a more fluid cellular state.
• Understanding these transitions is crucial for developmental biology and regenerative medicine.

Purpose of the Study:

• To investigate the solid/fluid transition in cell tissues using a biophysical model.
• To explore the role of cell deformability, interactions, and motility in tissue phase transitions.
• To determine the mechanism and phases involved in the solid/fluid transition of cellular systems.

Main Methods:

• Utilized the self-propelled Voronoi model to simulate cell tissue behavior.
• Incorporated cell deformability, many-body interactions, and polarized motility into the model.
• Analyzed the transition by varying parameters controlling self-propelling force and mechanical rigidity.

Main Results:

• The solid/fluid transition in cell tissues was found to occur in two continuous steps.
• Observed a solid-to-hexatic transition followed by a hexatic-to-liquid transition.
• The observed transition mechanism aligns with the Kosterlitz, Thouless, Halperin, Nelson, and Young (KTHNY) scenario.

Conclusions:

• The study elucidates the phase transition dynamics of cell tissues.
• The findings suggest that the hexatic phase, previously overlooked in biology, may play a significant role in cellular processes.
• This research provides a framework for understanding tissue fluidity and its implications in biology.