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Discovery of a Previously Unknown Ear ‘Doorway’ May Lead to Breakthroughs in the Treatment of Deafness

Photo by Mark Paton on Unsplash

A team of researchers was able to successfully reestablish hearing in a group of deaf mice by combining a novel strategy to administer a gene therapy that was focused on mending inner ear hair cells with their previous success in restoring hearing in human patients. This finding was made feasible by leveraging the typical movement of fluids in the brain and then making use of “a little understood backdoor” into the cochlea. This “backdoor” allowed researchers to get access to the cochlea.

These findings demonstrate that cerebrospinal fluid transport comprises an accessible route for gene delivery to the adult inner ear and may represent an important step towards using gene therapy to restore hearing in humans, stated Maiken Nedergaard, MD, DMSc, senior study author.

The glymphatic system is the brain’s one-of-a-kind way of getting rid of waste, and it was first identified by the Nedergaard lab in 2012, which is almost a decade ago. Modern science is finally piecing together a more comprehensive understanding of the dynamics of the glymphatic system.

More Study Insights

The authors of the study also discussed an additional finding, which was that the intricate flow of fluids that is regulated by the glymphatic system extends all the way to the eyes as well as the peripheral nervous system, which includes the ear. This novel study gives an interesting chance to finally put the medication delivery capabilities of the glymphatic system to evaluation, all while also targeting a hitherto inaccessible region of the auditory system at the same time.

According to current forecasts, the number of individuals who are now living with hearing loss of any severity, from moderate to severe, will most certainly increase to around 2.5 billion by the second half of this century. The key factor that contributes to this kind of hearing impairment is the death of hair cells in the cochlea or their inability to function normally. 

How Were They Able to Reach These Findings?

The study team was successful in developing a precise description of how fluid from various areas of the brain flow via the cochlear conduit and into the inner ear by using many imaging and modeling tools. Following this step, the authors of the researchers administered an adeno-associated virus through the cisterna magna, which is a huge storehouse of cerebrospinal fluid located near the base of the skull. This virus ultimately made its way via the cochlear aqueduct and into the inner ear, where it delivered a gene therapy that expressed a protein known as vesicular glutamate transporter-3. This therapy enabled the hair cells to transfer impulses, therefore restoring hearing in adult mice who had been born deaf.

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