There are more than 275 million people that have moderate to profound hearing loss, and many are caused by a breach in the connection between the inner ear and the brain. Researchers have discovered that a key component in repairing the auditory nerve is human embryonic stem cells.

The scientists published their findings in the journal Nature. They have been able to establish a proof of concept by using human embryonic stem cells to repair the damaged ears of gerbils.

Stem cells were differentiated into auditory nerve cells before, but this is the first instance of a successful transplantation into animals. It’s a pivotal step that will undoubtedly spur on more research.

Marcelo Rivolta, a stem-cell biologist at the University of Sheffield, UK, has spent the last decade developing ways to differentiate human embryonic stem cells into auditory neurons and the inner-ear hair cells, which translate sound into electrical signals.

The cells were transplanted into gerbils that had been treated with ouabain, a chemical which damages auditory nerves but not the hair cells. 10 weeks after the procedure, the transplanted cells had grown projections that formed connections to the brain stem. Testing has shown that many of the animals could hear much fainter sounds after transplantation, with an improvement of their overall hearing of 46%.

Since there are many ways that ears and the sense of hearing can be damaged, it remains unclear how many people would benefit from this kind of treatment; but stem cells could broaden the reach of existing therapies.

[via Nature]