Acceleration of permeability barrier recovery by exposure of skin to 10-30 kHz sound

Background Previous reports show that ultrasound can influence human brain electrical activity and systemic hormone levels in various parts of the body, other than the ear, so there may be an unknown ultrasound-responsive system in humans. Objectives In the present study, we examined the effects of sound on skin permeability barrier homeostasis. Methods We broke the skin barrier of hairless mice by tape stripping, and then exposed the skin to sound for 1 h to evaluate the effect on barrier recovery rate. Results Exposure of skin to sound at frequencies of 10, 20 and 30 kHz for 1 h accelerated barrier recovery, and 20 kHz sound induced the fastest recovery. Application of 5 kHz sound had no effect on barrier recovery rate. Significant acceleration was observed even when the sound source was located 3 cm away from the skin surface. The recovery rate depended on the sound pressure. An electron-microscopic study indicated that lamellar body secretion between stratum corneum and stratum granulosum was increased by exposure to sound at 20 kHz. Conclusions These results suggest that epidermal keratinocytes might be influenced by ultrasound in a manner that results in modulation of epidermal permeability barrier homeostasis.