Heat stress-induced changes in the mechanical properties of mouse outer hair cells

Overexposure to intense sound damages outer hair cells (OHCs) and causes the loss of cochlear amplification, resulting in permanent hearing loss. However, OHCs are protected from such exposure by prior sublethal conditioning. Although the protective mechanisms is thought to be based on the modification of the cell structure which reduces the mechanical damage of cells, it is not clear whether the cell structure becomes more flexible or more rigid by such modification. In this study, therefore, the mechanical properties of OHCs in mice with/without heat stress were measured by atomic force microscopy (AFM). As a result, it was found that conditioning by heat stress causes an increase of Young's modulus of OHCs in mice 3-12 h after heat stress.