Inner Ear Hair Cell Regeneration — Maybe We Can Know More

Whoops again, I'm newer here.

 

The current way of measurement is definitely outdated.They always take your age into account and say it's normal for your age to no hear certain tone frequencies.Yet they can't tell the difference between hearing damage and age related hearing loss.You have to be really hard of hearing before they consider hearing loss.

 

Isn't that sort of what they are trying to achieve with neurotrophins? From the article you posted:
"Eye and Ear researchers have shown in animal models that, under some conditions, connections between the sensory cells and the auditory nerve can be successfully restored using growth factors, such as neurotrophins."

 

For 15 years many tinnitus-hyperacusis-hearing impaired forumers hazarded this guess, at last an evidence is scientifically shown now.

 

I am pretty sure it is the spiral ganglion.
Is it like this?: hair cell>>neuron in spiral ganglion>>fibres>>
First step is damage of neurons in spiral ganglion. Next step loosing connections. (hidden hearing loss)
Next step dying of hair cells. (hearing loss shows on audiogram)
That is my very basic understanding.

 

So is this discovery bad or good for us?

 

Well I think it's good

As I understand Liberman knows what to inject and how to identify people that shows the problem he wants to solve. I think he is getting quite close and he'll probably need to do some safety research now.

 

From what I read, his treatment only helps very very acute hearing loss (within 24 hours of exposure)

 

Last year he said “Hidden hearing loss may soon be treatable by injection through the eardrum of gels that slowly release neurotrophins to restore synapses months or years after a noise insult.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4227045/

But maybe I misunderstand

 

No, Liberman says:
“Hidden hearing loss may soon be treatable by injection through the eardrum of gels that slowly release neurotrophins to restore synapses months or years after a noise insult.”

But we actually don't know anything for certain yet.

 

That would be awesome!! Again, I'd be happy with just making sure my current hearing doesn't get any worse.

 

The nerve fibers extend off of the spiral ganglion neurons. It's hard to say which sort of hair cell they extend off to, but I've read that a single nerve fiber can extend to only one outer hair cell and then multiple other nerve fibers can extend out to multiple inner hair cells. But then again, there are two different types of spiral ganglion neurons. Afferent and Efferent. There's a lot more to be explained, but I gave a little summary of it.

So the stage of damage can look like this: Loud noise over a brief period of time = immediate disconnection of nerve fibers synapses from the specific sensory hair cells they were associated with -> after a certain amount of time the fibers will retract back into the spiral ganglion neuron they were associated with -> if not treated with neurotrophic factors, the end result will be the retraction and even death of those spiral ganglion nuerons // On a side note, the users who have grown into their older years and have had noticeable ringing for years upon years makes me question that last part. There's gotta be more to it.

 

I still do not understand how than people can benefit from cochlear implants? If I am not mistaken, for cochlear implants hair cell are not needed. The cochlear implant excites the spiral ganglion neurons. How else can we get signals from the implant into our brains?
I understand that people that have been hard of hearing for a long, long time (perhaps even decades) can still benefit from a cochlear implant.
I wonder if there is information on the internet as to when you are eligible for a cochlear implant or when it will not work.

 

A question that I wonder too!

 

By any chance are there any informations about decibel recovery after neurotrophic factors treatments in those preclinical stages ? I ask because there are many persons with decibel threshold loss, even you with no dramatic decibel loss can feel a lack of power and sparkle from what i understood. Agreed for the regeneration from the processing zones i.e spiral ganglions neurons and the fiber synapses, but what about the microphone i.e the hair cells which are a kind of front door receiving air waves ? Would it mean that therapies would need two targets (either one or both) according to everyone's different kind and proportion of damages ?

 

I search the internet for 30 minutes and could not find any indication that there is a time limit.
The auditory nerve get signals from the implant. So, no hair cells needed.
Amazing technique.

 

@Aaron123, great find!

I wonder if this will further elucidate the difference between age-related hearing loss in which tinnitus never develops and acute hearing loss with associated tinnitus. I've always wondered why a 13 year old can hear better than a 30 year old, yet the 30 year old doesn't have tinnitus.

Perhaps it is because when hair cells "naturally" die, the connection to the nerve isn't damaged as well. On the other hand, with loud noise exposure, the connection is damaged as well as the hair cell. This might be a clue into tinnitus.

 

there arer 2 types of hearing cells + diference it total defness

 

I've read lots of Libermanns publishings and I believe he has found the cause,it's right in front of us!

In one of his latest publishings he said something along the lines of this....

"We have observed auditory nerve synaptic damage in patients whose haircells may still be intact,this would show a normal audiogram but it does not show if damage has occurred clearly.We have observed(and this is the important part)that haircells can die where as their synaptic connections remain in their terminals after haircell death,we have also noticed that haircells can survive but their underlying neuron have disconnected from its terminal"

Now this isn't a direct quote but to me it explains everything!We have often wondered why do those with normal hearing loss not experience T?Well according to Libermann these connections that underly it can still be intact even though the haircell it's connected to is dead but he believes that when these connections are lost that people will develop T and H.
For people without T and H but hearing loss the haircells are dead but the synapse connecting to it is still intact hence why they experience no T.For those of us with normal hearing our haircells are alive and well but our underlying neurons have been damaged,and for those who experience hearing loss and T it's a combination of both of these things.Libermann has cracked it,I know he has!It all makes perfect sense now.

 

This makes total sense to me.
Thats why "inner ear hair cell regeneration" wouldnt work for us
But...Neurotrophic factors or steam cells would do it!
im not an expert but i believe this could be easier than regrow ear hair cells since its... not "natural"
and repair or reconnect something sound more... likely to happen ?
i dont know...

 

Could you provide a citation for a paper where Liberman discusses hair cell death with intact ribbon synapses? I would like to read the paper.

 

It actually says it in the very publishing you posted here Aaron,he states that haircells can die but the underlying synapses can remain intact regardless of haircell loss.He also states that these synapses can be damaged and it's connecting haircell can still be alive and well.To me at least that is a major clue as to why there is multiple T scenarios,T but no hearing loss,hearing loss and T,hearing loss and no T,no hearing loss but T and H etc etc.

I'm 99% certain that these synapses are responsible for T and H,I may be wrong but it's starting to look like the fog is being lifted.

 

Actually I'm wrong it's not in the one you posted its in the link Joyce Cohen showed me,few minutes Aaron and I'll post it here for you,I'll tag your name so your notified.

 

This would make total sense in my case.

I just wonder in what scenario the hair cell can die whilst the synapse/nerve fiber remains intact. I might have guessed it would just be due to old age but it's still more common to see hidden hearing loss (synapse/ SGN damage ) in old people before you see an impact on there audiogram (hair cell damage). Perhaps its possible that people with hearing loss and no T are losing the nerve fibers but they are just dead rather than damaged? If that makes any sense.

Also, if Liberman is right about this, is this not more or less of a break through? Now knowing the cause of most peoples T.

 

I must have missed it. Could you point to the specific quote - which article, page, etc?

Thanks.

 

Apparently these synapses can die from noise age and toxins and are much more susceptible to damage than haircells are.These synapses in most cases get damaged long before the haircell does.

 

My god my head is spinning from all these links I've been on,it turns out Aaron that one of those statements was indeed on the link you posted but I know there's another link where they go into more detail about haircells being dead but the underlying synapses can remain intact,I'm gonna keep reading through them until I find it,here's where they touch on the subject of where the synapses die but the haircell remains....

 

What I do not understand that dead hair cells remain. In the body, dead cells are always taken away. I forgot the name of this process.
I also read that when someone gets a cochlear implant, remaining hair cells get damaged. So no residual hearing remains. That is why in order to be eligible for a cochlear implant you need to be profoundly deaf.

 

I don't know what it's called either or what actually happens the cells once they're dead,I'm not at all educated on that to even contemplate giving an answer.But what I gathered from this is that haircells can die and leave behind perfectly fine underlying synapse which to me at least explains hearing loss with no T.Its also possible to lose nearly all these synapses but still have a healthy connecting haircell which might explain perfect audiograms but still have T and H.

 

I'm kind of screwed with hearing loss + T + H. I'd have to get new hair cells and new synapses to get brand new ears.

If you lost a lot of hair cells, can you still hope to get rid of T with synapses regeneration ?