TABLE 1:

Comparison of simulation predictions and in vitro experimental observations.

Simulation predictions	In vitro experimental observations
Type of stretch
Simple elongation: Actin bundles typically (with many parameters sets) align ∼55–60° relative to direction of applied unconfined cyclic stretch (Figure 6A).	In vitro experiments utilizing unconfined cyclic stretch, both we and others report actin alignment along an axis of minimal strain, ∼55–65° relative to direction of applied stretch (Figures 4 and 5A) (Wang et al., 2001; Barron et al., 2007; Faust et al., 2011; Matsugaki et al., 2013).
Purely uniaxial stretch: Actin bundles typically (with many parameters sets) align perpendicular relative to direction of applied purely uniaxial confined cyclic stretch (Figure 6, B and C).	Others report actin realignment ∼90° relative to direction of applied cyclic strain Figure 5B) (Wang et al., 2001; Standley et al., 2002).
Equibiaxial stretch: Actin bundle orientation is not changed following exposure to equibiaxial cyclic stretch (Figure 6E).	Randomly oriented cell populations remain randomly oriented following exposure to equibiaxial cyclic stretch (Wang et al., 2001; Kaunas et al., 2006).
Magnitude of stretchDose response: For moderate and high substrate stiffness, final angle of reorientation increases (toward perpendicular) with increasing amplitude of cyclic stretch (Figure 6), until reaching perpendicular.For high substrate stiffness, amplitude of cyclic stretch affects rate of actin bundle realignment, where increasing amplitude increases rate of realignment (Supplemental Figure 2).Minimal effective dose: Significant realignment is noticeable with stretch amplitudes as low as 1% (Figure 6).	We and others show increasing cellular and actin fiber reorientation with increasing stretch amplitude (Faust et al., 2011).Rate of reorientation is affected by amplitude of cyclic stretch., where characteristic time of reorientation decreases linearly with increasing stretch amplitude (Jungbauer et al., 2008).We and others show significant realignment with stretch amplitudes as low as 1% (Faust et al., 2011), while others report minimum stretch amplitudes greater than 1% required for reorientation response (Nava et al., 2020).
Frequency of stretchRate of reorientation: For high substrate stiffness, frequency of cyclic stretch affects rate of actin bundle realignment with increasing frequency increasing rate of realignment (Figure 7A).Final angle of orientation: Frequency has no effect on final angle of orientation (Figure 7).	Rate of cellular reorientation is affected by frequency of cyclic stretch, where the characteristic time required for reorientation decreases with increasing frequency. For confluent cell cultures, characteristic time decreases exponentially (Jungbauer et al., 2008).Frequency affects final angle of orientation, where final angle of reorientation increases with increasing frequency (Jungbauer et al., 2008).
Substrate stiffnessFor low substrate stiffness, actin bundles align parallel to the direction of applied cyclic stretch (Figure 6D).	Others have reported realignment parallel to the direction of applied cyclic stretch on soft collagen substrates (Tondon and Kaunas, 2014).
Myosin motorsReducing myosin motor stall force by one order of magnitude completely eradicates actin bundle reorientation in response to cyclic stretch (Figure 8).	Blocking myosin II function through the use of blebbistatin eliminates perpendicular reorientation of cells in response to cyclic stretch (Goldyn et al., 2010; Greiner et al., 2013).