Strings and topological defects govern ordering kinetics in endothelial cell layers

Area of Science:

• Cell biology
• Biophysics
• Soft matter physics

Background:

• Physiological processes, including endothelial cell alignment in vasculature, rely on cell layer phase transitions.
• Understanding these transitions is key to comprehending tissue dynamics and development.

Purpose of the Study:

• To investigate the mechanism driving the transition between disordered and ordered phases in endothelial cell layers.
• To identify the role of nematic topological defects and emergent string excitations in this process.

Main Methods:

• Utilized time-resolved, large-scale imaging of endothelial cell layers.
• Employed physical modeling to analyze defect dynamics and ordering kinetics.
• Quantified the non-monotonic decrease in defect pairs and analyzed string excitations.

Main Results:

• Demonstrated that the cell layer transition is driven by the non-monotonic evolution of nematic topological defects.
• Observed the emergence of string excitations that bind defects, mediating their annihilation.
• Identified the interaction between intrinsic cell activity and alignment fields as critical for defect domain formation.

Conclusions:

• The study suggests an intermediate phase of ordering kinetics in biological matter.
• String excitations spanning multicellular scales are key to defect annihilation and ordering.
• This mechanism may regulate morphogenetic movements and in vivo tissue remodeling.