Endogenous Sheet-Averaged Tension Within a Large Epithelial Cell Colony.

Area of Science:

• Cell biology
• Biophysics
• Developmental biology

Background:

• Epithelial cells form 2D sheets crucial for tissue development and homeostasis.
• Intrasheet tension drives tissue shape changes but is often studied during directed migration.
• Forces in non-migrating, symmetric epithelial colonies remain poorly understood.

Purpose of the Study:

• To investigate endogenous forces within large, symmetric epithelial cell colonies.
• To quantify colony-level sheet forces in the absence of directional migration.
• To determine if these forces exhibit directional variations.

Main Methods:

• Utilized the traction force imbalance method (TFIM).
• Combined traction force microscopy with physical force balance principles.
• Analyzed large, circular epithelial cell colonies with symmetric boundaries.

Main Results:

• Successfully determined colony-level endogenous sheet forces at the midline.
• Observed significant variations in sheet force with orientation (max-min difference comparable to average).
• Found that while midline force is tensile, shear components vary considerably with orientation.

Conclusions:

• Unperturbed epithelial colonies with symmetric boundaries exhibit directional variations in endogenous sheet tension.
• Significant directional variations in shear forces also exist at the colony level.
• These findings clarify the nature of epithelial cell-generated forces in non-migrating collectives.