Stem cells restore hearing in deaf gerbils; human testing few years off: study

TORONTO - Researchers have restored the ability to hear in deaf gerbils using implanted human stem cells, achieving what they call a first step in potentially overcoming some causes of hearing loss in people.

While more study is needed to ensure the technique is safe for humans, principal researcher Dr. Marcelo Rivolta of the University of Sheffield said the work shows that stem cells can indeed regenerate nerve cells needed for hearing.

"It is early days, but we believe this is a substantial step forward because what we have here is the proof of concept that we can use human stem cells derived from human embryonic stem cells to repair the ear," Rivolta said from Sheffield, England.

The researchers, who describe their work in a paper published Wednesday in the journal Nature, began by using a chemical to destroy inner-ear mechanisms to render the gerbils deaf.

Gerbils, long-tailed rodents that range in length from 15 to 30 centimetres and live three to four years, have hearing that more closely approximates that of humans, compared with laboratory rats or mice.

Rivolta's team manipulated human embryonic stem cells taken from a cell line approved for use in research to create "otic progenitor" cells.

Embryonic stem cells give rise to virtually all tissue types in the body, from the various organs to neurons to skin. Progenitor cells generated from stem cells can differentiate into specific kinds of cells in this case, cells with the same properties as hair cells and auditory neurons, both critical for sensing sound.

Hair cells, located in the spiral-shaped cochlea in the inner ear, amplify and transform sound vibrations into electrical signals, which are then relayed via the auditory nerve to the brainstem.

While the researchers were able to surgically implant otic progenitor cells to repair the auditory nerve in the gerbils, hair cells are more challenging to deal with, said Rivolta. "We don't have a very good surgical technique to deliver the cells into the specific place that we need to."

Damage to hair cells which can be caused by genetic disorders, prolonged exposure to high-decibel noise and infections like bacterial meningitis can lead to partial or profound hearing loss.

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Stem cells restore hearing in deaf gerbils; human testing few years off: study