Strain-rate-dependent plastic deformation and Ductile-to-Brittle transition in epithelial tissues

As epithelial tissues are ubiquitous and naturally exposed to mechanical strains at various rates in normal functioning, it is crucial to understand their rate-dependent mechanical response and fracture failure behaviors. In this study, we utilize the modified cell vertex model, which allows for cell–cell detachment transition (T4 transition), to perform uniaxial tensile tests on cell monolayers and investigate how the strain rate affects the mechanical response of epithelial tissues. We find that high strain rates lead to the embrittlement and stiffening of epithelial tissue, akin to the phenomena observed in metal materials. We further demonstrate that high strain rate facilitates the Ductile-to-Brittle transition by promoting T4 transitions while preventing T1 transitions. Therefore, we conclude that strain rate regulates the occurrence priority of T1 and T4 transitions, resulting in the embrittlement and stiffening of epithelial tissues. Our study provides new insights into the mechanical behavior of epithelial tissues under different strain rates and may have important implications for understanding tissue viscoelasticity and tissue rupture in clinical pathologies.