Human ear cells vital for hearing have for the first time been created in the lab, and could eventually yield new treatments for hearing loss.

Such cells have been created before from mice, but the new cells will reveal more about how human hearing works.

“We believe these are the first from humans,” says Marcelo Rivolta of the University of Sheffield, UK and head of the team presenting its findings on Monday in Oxford at a conference on stem cells.

“Stem cell therapy for hearing loss is still some years away, but this research is incredibly promising and opens up exciting possibilities,” says Ralph Holme, director of biomedical research at the UK Royal National Institute for Deaf People, which co-funded the research with Deafness Research UK.


The team grew the cells from cochlear stem cells they’d isolated from fetuses following abortions, with the full consent of the women involved.

Timing is everything

Rivolta explained that such stem cells only exist for a short time, 9 to 11 weeks into a pregnancy, and then cease to be produced thereafter.

“That’s why deafness is permanent, because we don’t have the stem cells to replace damaged cells in the ear,” says Rivolta, whose team’s results will appear in the May issue of the journal Stem Cells.

“So we went to the fetal cochlea just before the fetal cells started to mature and differentiate into other cells,” he explained.

From the extracted material, Rivolta’s team successfully isolated human fetal auditory stem cells and grew them in the lab.

After exposing the cells to various recipes of nutrients and growth factors, the team found one cocktail that changed the stem cells into human auditory hair-like cells. When mature, these grow fine hairs that bend in response to sound energy, generating electrical signals.

A second recipe turned the stem cells into auditory neurons, the cells which receive signals from the hair cells and transmit them to the brain, which translates the messages into recognisable sound.

Noise damage

Hair cells are especially delicate, but once they’re lost through damaging exposure to excessive noise, for example, they’re irreplaceable, limiting the scope for treatment.

Now that these two types of cells can be made in the lab, researchers can study how they grow and work, and devise new ways to regenerate or repair them.

They can also use the cells to screen for drugs and chemicals that cause hearing loss by damaging them.

“These cells are for us a model system,” says Rivolta. “They are as we can get to human development, so by studying them we can learn how to handle them, and how they function.”

Although the hair cells created don’t have the trademark hairs, they are otherwise identical to hair cells in shape, in electrical activity and in the molecules they carry on their surfaces. Rivolta is confident that with further research, they can be produced with the accompanying hairs.

And to avoid having to obtain material from fetuses in future, the team have begun a project to try and make the required ear cells from embryonic stem cells (ESCs), the cells from embryos capable of developing into all 200 tissues of the body.

“We can take the information we now have to ESCs, to see if we can produce firstly auditory stem cells, then hair cells and auditory neurons,” he told New Scientist.

“It demonstrates that what our group has found in mice is generally applicable to humans, which is certainly another step in the direction of learning to control hair cell generation from a renewable source,” says Stefan Heller of Stanford University in California, and head of a team which in 2003 produced hair cells in mice.

“Being able to do this with human cells is an advantage and the strength of this study,” says Heller, “but this does not mean that a cure for hearing loss is around the corner, unfortunately.”