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Regenerating sensory hair cells to restore hearing to noise-damaged ears

Scientists from Massachusetts Eye and Ear and Harvard have identified a drug that may reverse permanent deafness by triggering a regeneration of sensory hair cells in the inner ear, according to findings (subscription required) recently published in Neuron.

According to a release, 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 cellular pathways. 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.

In a recent entry on the Stanford Initiative to Cure Hearing Loss blogStefan Heller, MD, PhD, comments on the findings and how the research could pave the way to treatments for this kind of hearing loss in humans. He says:

This report is another step in the right direction and it shows that it might be possible to induce an inherent regenerative potential of cochlear supporting cells.
It will be exciting to see follow up studies of this work, particularly studies that map the time window, when this treatment is effective after the insult. Right now, it appears that the treatment only works directly after the insult. The systemic side effects of this particular kind of drugs are substantial as well, so localized treatment is probably the only feasible way. Also, the mechanisms of recovery, particularly the morphology of the recovered organ of Corti needs to be investigated in more detail.

Particularly interesting will be to find out which cells respond to the treatment and what this response looks like. All this is very important before we can make an assessment whether this strategy would be useful in the future in humans.

As the post notes, researchers at Stanford have made considerable progress towards the understanding of inner ear hair cells and hair cell regeneration. Scientists here are engaged in ongoing efforts to create biological cures for major forms of inner ear hearing loss within the foreseeable future.

Previously: Stanford researcher comments on the use of human embryonic stem cells to restore hearing, Stefan Heller discusses stem cell research on Science Friday and Growing new inner-ear cells: a step toward a cure for deafness

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