  Epithelial tissues act as barriers and, therefore, must repair themselves,
respond to environmental changes and grow without compromising their integrity.
Consequently, they exhibit complex viscoelastic rheological behavior where
constituent cells actively tune their mechanical properties to change the
overall response of the tissue, e.g., from solid-like to fluid-like. Mesoscopic
mechanical properties of epithelia are commonly modeled with the vertex model.
While previous studies have predominantly focused on the rheological properties
of the vertex model at long time scales, we systematically studied the full
dynamic range by applying small oscillatory shear and bulk deformations in both
solid-like and fluid-like phases for regular hexagonal and disordered cell
configurations. We found that the shear and bulk responses in the fluid and
solid phases can be described by standard spring-dashpot viscoelastic models.
Furthermore, the solid-fluid transition can be tuned by applying
pre-deformation to the system. Our study provides insights into the mechanisms
by which epithelia can regulate their rich rheological behavior.
