Reversing Deafness With Gene Therapy

Reversing progressive deafness is one of the many plausible goals for the field of regenerative medicine, and scientists have in recent years demonstrated a way to spur creation of hair cells in the ear through a form of gene therapy. Any method that can reliably generate new hair cells has the potential to reverse the common forms of deafness caused by loss of those cells, such as through damage or aging. Here's a popular science article on this latest advance:

Raphael's team first gave the guinea pigs antibiotics which destroyed their inner-ear hair cells. They then apparently repaired the damage by injecting them with genetically engineered adenoviruses. ... The therapy promotes the regrowth of crucial hair cells in the cochlea, the part of the inner ear which registers sound. After treatment, the researchers used sensory electrodes around the animals' heads to show that the auditory nerves of treated - but not untreated - animals were now registering sound. ... The experiment worked beyond expectation. "The recovery of hair cells brought the treated ears to between 50% and 80% of their original hearing thresholds," says Raphael. Even more surprising, the team found that the hair cells were created from cells lining the scala media which - according to biological orthodoxy - should not be able to turn into other cells.

And here is the paper:

To restore hearing, it is necessary to generate new functional hair cells. One potential way to regenerate hair cells is to induce a phenotypic transdifferentiation of nonsensory cells that remain in the deaf cochlea. Here we report that Atoh1, a gene also known as Math1 encoding a basic helix-loop-helix transcription factor and key regulator of hair cell development, induces regeneration of hair cells and substantially improves hearing thresholds in the mature deaf inner ear after delivery to nonsensory cells through adenovectors.

You'll notice that this is another application of transdifferentiation, an approach that changes a cell from one type directly to another type without going through the now standard process of first generating pluripotent cells, then differentiating them into the desired cell type. Thus transdifferentiation might prove to be a useful tool for in-situ biological repairs that require a small population of specific cells to be replaced or regenerated, such as the dopamine neurons lost in Parkinson's disease, for example, or beta cells in the pancreas.


Feb 2005? Any more current updates on this idea?

Posted by: Patrick at November 28th, 2011 7:06 PM

@Patrick: I finally fail to check the date on an article - how annoying. I probably posted on this research back when it was first published, funnily enough.

Here is this review paper, however, from 2009:

"Therapies for the protection and regeneration of auditory hair cells are of great interest given the significant monetary and lifestyle impact of hearing loss. The past decade has seen tremendous advances in the use of adenoviral vectors to achieve these aims. Preliminary data demonstrated the functional capacity of this technique as adenoviral-induced expression of neurotrophic and growth factors protected hair cells and spiral ganglion neurons from ototoxic insults. Subsequent efforts confirmed the feasibility of adenoviral transfection of cells in the auditory neuroepithelium via cochleostomy into the scala media. Most recently, efforts have focused on regeneration of depleted hair cells. Mammalian hearing loss is generally considered a permanent insult as the auditory epithelium lacks a basal layer capable of producing new hair cells. Recently, the transcription factor Atoh1 has been found to play a critical role in hair cell differentiation. Adenoviral-mediated overexpression of Atoh1 in culture and in vivo have shown the ability to regenerate auditory and vestibular hair cells by causing transdifferentiation of neighboring epithelial-supporting cells. Functional recovery of both the auditory and vestibular systems has been documented following adenoviral induced Atoh1 overexpression."

Which doesn't say much more - so I'm guessing this thread of research is running slowly.

Posted by: Reason at November 28th, 2011 7:50 PM

Of tangential interest, and along the lines of the pro aging trance, I'm aware that some among the deaf community view attempts to cure deafness as a form of cultural genocide, and are hardly timid in expressing this view:

That this is absurd is obvious to most people, because most people were not born deaf. Oh that it were the same with aging. The kind of thinking that is plainly lunacy in one instance holds the entire world captive in another.

Posted by: Ben at November 28th, 2011 10:03 PM

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