Active Fingering Instability in Tissue Spreading.

Area of Science:

• Biophysics
• Cell Biology
• Fluid Dynamics

Background:

• Epithelial tissues spread via advancing fronts, often forming fingerlike protrusions.
• These patterns resemble viscous fingering in fluids, suggesting an interfacial instability mechanism.
• The physical basis for such instability in epithelial spreading remains unclear.

Purpose of the Study:

• To analytically predict the existence and physical mechanism of an interfacial instability in epithelial tissue spreading.
• To investigate the role of active cellular forces and intercellular stresses in driving tissue front instabilities.
• To elucidate how hydrodynamic interactions influence the resulting fingering patterns.

Main Methods:

• Development of an active polar fluid model for epithelial spreading.
• Analytical prediction of tissue front instability based on the model.
• Analysis of the interplay between cellular traction, intercellular stresses, and hydrodynamic interactions.

Main Results:

• A generic instability of the epithelial tissue front is analytically predicted.
• Active cellular traction forces create a velocity gradient, destabilizing long-wavelength perturbations.
• Contractile intercellular stresses stabilize short-wavelength perturbations, while hydrodynamic interactions select the fingering pattern wavelength.

Conclusions:

• Spreading epithelia exhibit an active fingering instability driven by a simple kinematic mechanism.
• The study highlights the critical role of long-range hydrodynamic interactions in determining tissue morphology.
• The findings provide a physical explanation for fingerlike protrusions observed during epithelial tissue spreading.