Actin Filament and Cell Orientation Align with Surface Acoustic Wave Propagation and Cell Migration in Vibration-Enhanced Wound Healing

Surface acoustic wave (SAW) stimulation has been reported to increase in vitro wound healing by about a factor of 2, which is a promising observation in the field of biophysics. However, its underlying cellular mechanisms are not yet sufficiently understood for potential therapeutic applications. We here aim to unravel the mechanisms of vibration-enhanced wound healing by studying the behavior of the actin cytoskeleton, nuclei, mechanosensitive proteins and cell orientation under SAW stimulation. We show that cells exhibit a SAW-independent anisotropy of actin filaments and nuclei in the migration direction which becomes more pronounced under SAW stimulation. Our data reveal a higher filament alignment along the wave's propagation axis and show that spatiotemporal factors like the proximity to the wound edge and the state of the healing process additionally change actin and nuclei orientation behavior. While the mechanosensitive proteins MRTF and Notch undergo SAW-independent activation in our setup, YAP activity was elevated only in single leader cells under SAW stimulation. Finally, we further corroborate the here found SAW-induced filament alignment by showing that SAW treatment also leads to faster cell orientations in migration direction in the wound monolayer. These results strongly imply that the mechanic vibration alters the actin cytoskeleton, leading to a more directed and therefore accelerated cell migration in SAW-stimulated wound healing. These findings deepen our understanding of the underlying mechanotransduction processes of the SAW stimulation effect and could facilitate the establishment of surface acoustic waves in therapeutics.