Stress fiber growth and remodeling determines cellular morphomechanics under uniaxial cyclic stretch.

Stress fibers in the cytoskeleton are essential in maintaining cellular shape and influence cellular adhesion and migration. Cyclic uniaxial stretching results in cellular reorientation orthogonal to the applied stretch direction. The mechanistic cues underlying changes to cellular form and function to stretch stimuli are currently underexplored. We show stretch-induced stress fiber lengthening, their realignment, and increased cortical actin in NIH 3T3 fibroblasts stretched over varied amplitudes and durations. Higher amounts of actin and stress fiber alignment were accompanied with an increase in the effective elastic modulus of cells. Microtubules did not contribute to the measured stiffness or reorientation response but were essential to the nuclear reorientation. We used a phenomenological growth and remodeling law, based on the experimental data, to model stress fiber elongation and reorientation dynamics based on a nonlinear, orthotropic, fiber-reinforced continuum representation of the cell. The model predicts the changes observed fibroblast morphology and increased cellular stiffness under uniaxial cyclic stretch which agrees with experimental results. Such studies are important in exploring the differences underlying mechanotransduction and cellular contractility under stretch.