Mechanical characterization of disordered and anisotropic cellular monolayers

Area of Science:

• * Biophysics
• * Developmental Biology
• * Materials Science

Background:

• * Cellular monolayers, like epithelia, exhibit complex mechanical behaviors.
• * Understanding tissue mechanics is crucial for developmental biology and regenerative medicine.
• * Vertex-based models offer a framework for simulating cell-cell interactions and tissue dynamics.

Purpose of the Study:

• * To model cellular monolayers using a vertex-based approach.
• * To investigate the effects of uniaxial stretching on tissue ordering and stress distribution.
• * To derive relationships between stress, strain, and strain rate for anisotropic tissue properties.

Main Methods:

• * Employed a vertex-based model to represent cells as convex polygons tiling the plane.
• * Defined global energy based on cell areas and perimeters, with dissipation through dynamic changes and neighbor exchanges.
• * Analyzed Xenopus embryo epithelium under uniaxial stretching to validate the model.

Main Results:

• * Uniaxial stretching induces spatial ordering in cellular monolayers.
• * Cells under tension align with stretch direction; cells under compression align against it.
• * Stress remains heterogeneous at the single-cell level despite tissue-level ordering.
• * Derived linearized relations for anisotropic mechanical properties and viscoelastic moduli.
• * Model predicts tunable tissue properties, balancing shear resistance and area change resistance.

Conclusions:

• * The vertex-based model accurately captures mechanical responses of epithelial tissues to stretching.
• * Tissue-level ordering and single-cell stress heterogeneity are key features of mechanically stressed epithelia.
• * The derived relationships provide a quantitative framework for characterizing anisotropic viscoelastic properties of biological tissues.
• * The model offers insights into how tissue mechanics can be tuned for specific functions.