Collective motility and mechanical waves in cell clusters.

Area of Science:

• Cellular mechanics
• Biophysics
• Developmental biology

Background:

• Epithelial cell clusters exhibit complex collective behaviors on substrates.
• Mechanical signals are crucial for organizing these cellular movements.
• Several experimental observations lack comprehensive mechanical explanations.

Purpose of the Study:

• To formulate a mechanical model explaining observed behaviors of collectively moving epithelial cell clusters.
• To investigate the role of mechanical signals and cell-substrate interactions.
• To provide a unified framework for understanding phenomena like tensile strains, traction patterns, and density waves.

Main Methods:

• Developed a mechanical model incorporating a molecular clutch mechanism to simulate cell-substrate and cell-cell interactions.
• Modeled 'stalling' of cell contraction due to external forces, differentiating between active and passive cells.
• Included contact inhibition of locomotion in the model.

Main Results:

• The model explains tensile internal strains in expanding cell clusters, even with proliferation.
• It accounts for traction forces being concentrated at the cluster edges.
• The model predicts the existence of density waves and describes the transition in annular cell clusters between expansion and rotation.

Conclusions:

• A mechanical model based on the molecular clutch concept can explain diverse experimental observations in collective epithelial cell migration.
• The model highlights the interplay between active cell contractility, passive responses to external forces, and cell-cell/cell-substrate adhesion.
• This framework offers testable predictions for future experimental validation.