Regenerative medicine for the inner ear: Summary

There are more than 400,000 deaf or highly hearing-impaired people in Japan. In fact, one out of 1,000 newborns is deaf. Therefore, recovering the hearing ability of the deaf has always been one of the most important priorities in the field of otolaryngology. Sensorineural hearing loss (SNHL) is very difficult to restore, especially in cases with severe hearing disturbance. The possible therapeutic strategies for treatment of SNHL are summarized below. In early-phase cochlear damage, it is crucial to rescue auditory cells from cell death and promote self-repair and cell activity. Induction of transdifferentiation (e.g., induction of transdifferentiation from supporting cells to cochlear hair cells) is the next useful strategy, or an alternative approach is to induce proliferation. Several challenging studies manipulating cell cycle regulators to regenerate inner ear hair cells have previously been attempted. However, if no cell sources remain in the inner ear, cell transplantation then becomes the only choice to restore cell growth through regeneration. Using bionic materials is another remaining possible alternative approach. Worthy of mention is a device (microimplant)-without battery and extracorporeal equipment-that has recently been developed.