Sensory hair cells regenerated, hearing restored in mammal ear

January 9, 2013, Massachusetts Eye and Ear Infirmary
These are normal inner and outer hair cells. Credit: Neuron, Mizutari et al.

Hearing loss is a significant public health problem affecting close to 50 million people in the United States alone. Sensorineural hearing loss is the most common form and is caused by the loss of sensory hair cells in the cochlea. Hair cell loss results from a variety of factors including noise exposure, aging, toxins, infections, and certain antibiotics and anti-cancer drugs. Although hearing aids and cochlear implants can ameliorate the symptoms somewhat, there are no known treatments to restore hearing, because auditory hair cells in mammals, unlike those in birds or fish, do not regenerate once lost. Auditory hair cell replacement holds great promise as a treatment that could restore hearing after loss of hair cells.

In the Jan. 10 issue of Neuron, Massachusetts Eye and Ear and Harvard Medical School researchers demonstrate for the first time that hair cells can be regenerated in an adult mammalian ear by using a drug to stimulate resident cells to become new hair cells, resulting in partial recovery of hearing in mouse ears damaged by noise trauma. This finding holds great potential for future that may someday reverse deafness in humans.

"Hair cells are the primary for sound and are responsible for the sense of hearing," explains senior author, Dr. Albert Edge, of Harvard Medical School and Mass. Eye and Ear. "We show that hair cells can be generated in a damaged cochlea and that hair cell replacement leads to an improvement in hearing."

In the experiment, the researchers applied a drug to the cochlea of deaf mice. The drug had been selected for its ability to generate hair cells when added to stem cells isolated from the ear. It acted by inhibiting an enzyme called gamma-secretase that activates a number of . The drug applied to the cochlea inhibited a signal generated by a protein called Notch on the surface of cells that surround hair cells. These supporting cells turned into new hair cells upon treatment with the drug. Replacing hair cells improved hearing in the mice, and the improved hearing could be traced to the areas in which supporting cells had become new hair cells. "The missing hair cells had been replaced by new hair cells after the drug treatment, and analysis of their location allowed us to correlate the improvement in hearing to the areas where the hair cells were replaced," Dr. Edge said.

This image shows cochlea after damage only and after damage and replacement of hair cells. Credit: Neuron, Mizutari et al.

This is the first demonstration of hair cell regeneration in an adult mammal. "We're excited about these results because they are a step forward in the biology of regeneration and prove that mammalian hair cells have the capacity to regenerate," Dr. Edge said. "With more research, we think that regeneration of opens the door to potential therapeutic applications in deafness."

Explore further: Study shows isolation of stem cells may lead to a treatment for hearing loss

More information: "Notch Inhibition Induces Cochlear Hair Cell Regeneration and Recovery of Hearing after Acoustic Trauma." Neuron, 2013.

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3 / 5 (2) Jan 09, 2013
Thank God for Government funded research.
4 / 5 (1) Jan 09, 2013
Why do you think the government had anything to do with this?
Whydening Gyre
1 / 5 (2) Jan 09, 2013
These previous three statements define change -
1. Definitive. (from Vendicar)
2. "Yeah - but"... (from snivvy)
3. Refined definitive. (from Nathj72)

A plus (A plus Y) = (E)verything. Repeat.

MY T.O.E. I love it.
3.7 / 5 (3) Jan 09, 2013
Why do you think the government had anything to do with this?

The guy who runs the group, Albert Edge has been looking into regeneration for years all supported by your coerced tax dollars! Many NIH grants to support his group. I agree that in ~10 years, some "free market" Entrepreneur will take the 50K human years of gov. supported work in this area and turn it into a product to save me and maybe you from my inherited slowly declining hearing. Go Gov!

I never even knew I had this problem and so would never have even found let alone supported his research. But here it is just waiting for me from our collective communal efforts. High fives all around and especially to Dr. Edge who keeps on pursuing this stuff (with our, now thankful, help).

Long term research, such as is now (within another 10) going to spawn a private space industry, is never worth it in a market economy. It takes a gov. Deal with it.
5 / 5 (3) Jan 09, 2013
From the article, "Four-week-old mice were exposed free field, awake and unrestrained, in a small reverberant chamber (Wang et al., 2002). Acoustic trauma was produced by a 2 hr exposure to an 8–16 kHz octave band noise presented at 116 dB SPL."

I'm no sound expert but I imagine that would be quite painful. I glanced over the article of the team that developed the sound exposure technique as to why they were not anaesthetized but didn't really see much. I was thinking maybe it was to prevent damage to just one side of the ear (only the right ear is tested) but anyone else wager a guess?

Here's the link to that article: http://www.ncbi.n...e_28.pdf
5 / 5 (3) Jan 09, 2013
In the hearing lab I worked at the standard practice was to place essentially earbuds into the guineapigs' ears before subjecting them to 90 minutes of 110 dB sound at a variety of frequencies.

Many labs going for deafness caused by hair cell destruction treat the ears with neomycin which kills the hair cells and causes utter deafness.
5 / 5 (1) Jan 10, 2013
What is the purpose of the earbuds? I'm assuming it doesn't stop the deafness but does it help with pain? Since neomycin kills the hair cells causing deafness, what are the reasons to choose exposure to sound versus chemical treatment?
5 / 5 (1) Jan 10, 2013
Cochlear hair cell regeneration isn't new. What I'd like to know - will hairs grown with this technique be permanent, or dependent on continued drug use to remain viable? I'm wary of being forced into a lifetime of indentured servitude to pharmaceutical firms to maintain restored hearing.
4 / 5 (4) Jan 10, 2013
Fantastic! Most people have deteriorating hearing with age, even if they are not technically deaf, and now there seems to be a treatment for this..! Kudos to the researchers!
5 / 5 (1) Jan 13, 2013
Bloody Brilliant!!

I hope this technology one day can restore my partial hearing loss. In social situations I'm retarded as I can't distinguish the sound of someone speaking to me from the buzz of background noise.
3 / 5 (2) Jan 14, 2013
I've got a progressive degenerative hearing loss, I'm 24 years old and have the hearing of an 80 year old. By the time I am 50 years old I will be deaf as a bat without hearing aides. I would really like to see some kind of one time treatment to make me and my whole family (it's a genetic disorder) hear again!
Whydening Gyre
1 / 5 (2) Jan 15, 2013
Cochlear hair cell regeneration isn't new. What I'd like to know - will hairs grown with this technique be permanent, or dependent on continued drug use to remain viable? I'm wary of being forced into a lifetime of indentured servitude to pharmaceutical firms to maintain restored hearing.

I'm certain it is subject to it's own ratio of degeneration. It is also certain there will be a point of diminishing return for each successive regeneration. Or not....

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