Sound Sensing Hair Cells Regenerated in Mice

Damage to the sound-sensing hair in the inner ear is one of the major factors contributing to hearing loss in mammals. Previously, scientists thought that these cells were irreplaceable, making hearing loose an irreversible process. However, a new study involving newborn mice shows that supporting cells in the ear can transform into hair cells.

If researchers can apply their findings to older animals, they may lead the way to hair cell replacement in human adults. This new treatment could aid people suffering from deafness due to a loss of hair cells, according to the press release announcing the findings.

The research, published in Stem Cell Reports, is the first study to show that hair cell replacement can occur, but only at very low levels.

"The finding that newborn hair cells regenerate spontaneously is novel," said senior author Dr. Albert Edge of Harvard Medical School and Massachusetts Eye and Ear Infirmary.

In earlier research, the team found that by inhibiting the Notch signaling pathway they were able to increase hair call differentiation, helping to restore hearing in mice with noise-induced deafness. In the new study, the researchers were able to block the Notch pathway in order to increase formation of new hair cells. This time the hair cells came from nearby supporting cells that express a protein called Lgr5, instead of from the remaining hair cells.

"By using an inhibitor of Notch signaling, we could push even more cells to differentiate into hair cells," said Edge. "It was surprising that the Lgr5-expressing cells were the only supporting cells that differentiated under these conditions."

The new discoveries about Lgr5-expressing cell differentiation, along with Notch inhibition research, will allow future scientists to design hair cell regeneration studies that could one day restore hearing to deaf humans.