In an astonishing breakthrough, scientists have developed a drug that could potentially cure what was once thought to be permanent deafness.
The drug, codenamed LY411575, triggers the regeneration of sensory hair cells and stimulates the inner ear.
This is the first time the restoration of cells lost due to noise exposure, infection and toxic drugs has been possible.
The deafness that is often suffered by rock musicians and DJs was once thought to be irreversible.
Scientists succeeded in partially restoring hearing to mice that had been deafened by loud noise.
While the research is at an early stage, they do believe the restoration of human hearing due to noise exposure will be possible.
The tiny sensory hairs in the cochlea are vital to hearing. Sound vibrations transferred from the eardrum shake the hairs, causing nerve messages to be fired to the brain.
Without the hairs, the pathway would be blocked and hearing would be impossible.
The new method involves reprogramming inner ear cells by inhibiting a protein called Notch.
Notch signals help prevent stem cells in the cochlea from transforming into new sensory hair cells.
The drug LY411575 suppresses Notch. Mice with noise-induced hearing loss generated functioning sensory hair cells after the drug was injected into their damaged cochleas.
“We show that hair cells can be regenerated from the surrounding cells in the cochlea,” said lead researcher Dr. Albert Edge, from Harvard Medical School
“These cells, called supporting cells, transdifferentiate into hair cells after inhibition of the Notch signalling pathway, and the new hair cell generation results in a recovery of hearing in the region of the cochlea where the new hair cells appear.
“The significance of this study is that hearing loss is a huge problem affecting 250 million worldwide.”
Details of the study are reported in the journal Neuron.
“The missing hair cells had been replaced by new hair cells after the drug treatment, and analysis of their location allowed us to correlate the improvement in hearing to the areas where the hair cells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,” added Dr. Edge.
“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.
“With more research, we think that regeneration of hair cells opens the door to potential therapeutic applications in deafness.”
Vivienne Michael, chief executive of the charity Deafness Research UK, is excited about the new findings, but not jumping to any conclusions just yet.
“As always, we have to be cautious about new research findings but this US research is extremely encouraging,” she said.
“At the moment there is no way of reversing eight in 10 cases of hearing loss, including noise-induced deafness and the progressive deafness so many of us experience as we age – hearing aids are the only answer.
“These results show just how important it is to increase the investment in research into medical treatments that could prevent or reverse hearing loss and improve the quality of life for the millions of people affected.”
James Gilbert | Elite.