Kyoto, Japan -- There's a sensation that you experience -- near a plane taking off or a speaker bank at a concert -- from a sound so total that you feel it in your very being. When this happens, not only do your brain and ears perceive it, but your cells may also.
Technically speaking, sound is a simple phenomenon, consisting of compressional mechanical waves transmitted through substances, which exists universally in the non-equilibrated material world. Sound is also a vital source of environmental information for living beings, while its capacity to induce physiological responses at the cell level is only just beginning to be understood.
Following on previous work from 2018, a team of researchers at Kyoto University have been inspired by research in mechanobiology and body-conducted sound -- the sound environment in body tissues -- indicating that acoustic pressure transmitted by sound may be sufficient to induce cellular responses.
"To investigate the effect of sound on cellular activities, we designed a system to bathe cultured cells in acoustic waves," says corresponding author Masahiro Kumeta.
The team first attached a vibration transducer upside-down on a shelf. Then using a digital audio player connected to an amplifier, they sent sound signals through the transducer to a diaphragm attached to a cell culture dish. This allowed the researchers to emit acoustic pressure within the range of physiological sound to cultured cells.
Following this experiment, the researchers analyzed the effect of sound on cells using RNA-sequencing, microscopy, and other methods. Their results revealed cell-level responses to the audible range of acoustic stimulation.
In particular, the team noticed the significant effect of sound in suppressing adipocyte differentiation, the process by which preadipocytes transform into fat cells, unveiling the possibility of utilizing acoustics to control cell and tissue states.
"Since sound is non-material, acoustic stimulation is a tool that is non-invasive, safe, and immediate, and will likely benefit medicine and healthcare," says Kumeta.
The research team also identified about 190 sound-sensitive genes, noted the effect of sound in controlling cell adhesion activity, and observed the subcellular mechanism through which sound signals are transmitted.
In addition to providing compelling evidence of the perception of sound at the cell level, this study also challenges the traditional concept of sound perception by living beings, which is that it is mediated by receptive organs like the brain. It turns out that your cells respond to sounds, too.
