I suffer from progressive hearing loss so I found this article interesting.
phys.org

Regrowing hearing cells: New gene functions discovered in zebrafish offer clues for future hearing loss treatments
While humans can regularly replace certain cells, like those in our blood and gut, we cannot naturally regrow most other parts of the body. For example, when the tiny sensory hair cells in our inner ears are damaged, the result is often permanent hearing loss, deafness, or balance problems. In...