Why can’t hearing cells regenerate? Since it seems like virtually every other cell can.
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It’s the bone inside the ear which is needed to conduct sound waves that degenerates over time that causes hearing loss.
The problem isn’t the cells, it’s the hairs. Your hearing sensors are tiny little hairs connected to nerves. For hopefully obvious reasons, you don’t want your inner ear filling with hair so they grow to the length they need to be then stop.
If you damage the hairs by exposure to sound that’s too loud, they’re broken & gone. And they don’t regrow because that ability never turned “on” in humans. Presumably there’s very little evolutionary pressure…losing your hearing in middle/late life doesn’t really impact your ability to procreate.
Edit: clarified that the inner ear hair cells aren’t hair like on your head and aren’t dead, but don’t regrow. See /u/TeeDeeArt’s comment for details.
Relatively few cells can regenerate. Our bodies crudely plug most areas of destroyed tissue with what we know as scar tissue. But a scar on your arm or whatever isn’t the same as skin (no hair, glands, or etc.) and it isn’t made of the same cells (keratinocytes, melanocytes, etc..) as much of the rest of our epidermis. Ditto for most damage elsewhere. A heart attack that kills heart cells will mean that area of the heart becomes permanently non-functional. Brain cells killed by a stroke are gone forever. Etc..
For our cells to regenerate they usually need associated stem cells. So for a topical example, COVID infections can kill our olfactory neurons. Normally, neurons don’t regenerate, but in this one case our body is configured such that we do have stem cells in the relevant tissue to allow regeneration. So the loss of smell/taste from infection is temporary until the neurons regenerate. The liver is another organ that is capable of regeneration.
Not all hearing loss is due to this. There is nerve damage, the bones – incus maleus and stapes, the eardrum itself, and thenerves that conduct the signal to the brain… Everything has to work in sync for one to be able to hear well.
Some animals can do this, and research is happening to see if this can lead to healing this type of hearing loss. https://www.audubon.org/news/how-chickens-could-inspire-new-treatments-deafness#:~:text=Scientists%20have%20long%20known%20that,ear%20responsible%20for%20interpreting%20sound.
Reversing hearing loss with regenerative therapy
MIT spinout Frequency Therapeutics’ drug candidate stimulates the growth of hair cells in the inner ear.
https://news.mit.edu/2022/frequency-therapeutics-hearing-regeneration-0329
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