Active T1 transitions in cellular networks.

Area of Science:

• Biophysics
• Materials Science
• Cell Biology

Background:

• Amorphous solids and biological tissues exhibit flow via neighbor exchanges (T1 rearrangements) that relax local stresses.
• Understanding the physical mechanisms driving these rearrangements is crucial for comprehending tissue dynamics.

Purpose of the Study:

• To investigate T1 rearrangements in polygonal cellular networks using an anisotropic vertex model.
• To differentiate the effects of two distinct physical realizations of active anisotropic stresses: anisotropic bond tension and anisotropic cell stress.

Main Methods:

• Utilized an anisotropic vertex model to simulate T1 rearrangements in cellular networks.
• Analyzed the patterns of T1 transitions and cell elongation under different active stress conditions.
• Employed a continuum description of the tissue as an anisotropic active material.

Main Results:

• The two types of active stress (anisotropic bond tension vs. anisotropic cell stress) produced distinct patterns of T1 transition orientation and cell elongation.
• These distinct patterns suggest that the underlying physical realization of active stress can be identified in vivo.
• Derived an energy balance equation for dynamic tissues, including internal elastic energy, mechanical work, chemical work, and heat.

Conclusions:

• Active T1 transitions can be categorized based on the physical origin of anisotropic active stresses.
• The study provides a framework for observing and distinguishing between different active stress mechanisms in living tissues.
• Defined active T1 transitions capable of performing mechanical work through chemical energy consumption.