If you've heard deep bass, the roar of a jet engine, or rumbling thunder, you may have felt it in your body. Our cells have a variety of ways to sense mechanical forces, including those that can be caused by sound. Sound is everywhere in nature, and it is a physical force in the form of a wave, which can fluctuate and move through substances. Researchers have even been able to measure the transmission of sound through soft tissues in the human body.
While external sources like speakers can make sounds that are detected in the human body, mechanical forces like physical contact can also produce sounds in the human body. Researchers have been trying to decipher how sounds can be detected in the human body at the cellular level, and what types of physiological reactions those sounds may cause.
Scientists have now learned more about the sound environment in human tissues, which is known as body-conducted sound, and mechanobiology, in which physical forces cause biological responses. Reporting in Communications Biology, scientists have found that acoustic pressure that is emitted by sound can trigger responses at the cellular level in humans.
"To investigate the effect of sound on cellular activities, we designed a system to bathe cultured cells in acoustic waves," said corresponding study author Masahiro Kumeta of Kyoto University.
In this study, the researchers amplified and transmitted sounds through a vibration transducer that emitted acoustic pressure into dishes of cells growing in culture. One set of cells was stimulated for two hours while another was stimulated for 24 hours. The investigators used a variety of methods to assess how the cells were affected, such as microscopy, RNA sequencing that revealed the active genes at one time in the cell, and other techniques.
The work indicated that sound pressures affected the cells. Sound seemed to trigger changes in how cells that precede fat-containing adipocyte cells, known as pre-adipocytes, transformed into adipocytes. Sound could alter the states of cells or tissues, the researchers suggested.
The work also indicated that around 190 genes had reacted to the sound stimulation. Some of those genes responded to the initial two hour stimulation while others were only affected after 24 hours. The expression of some increased while others decreased. Processes that were affected included cell adhesion.
"Since sound is non-material, acoustic stimulation is a tool that is non-invasive, safe, and immediate, and will likely benefit medicine and healthcare," suggested Kumeta.
Previous work by this team is outlined in the video.
The study also identified a subcellular mechanism that transmits sounds.
Since sounds are so common in the world, the researchers noted that it is not surprising that cells would react to them physiologically. The work may also open up different methods for influencing health. Unrelated work has shown in a variety of studies that ultrasounds can affect brain cells, for example.
Sources: Kyoto University, Communications Biology