Scientists grow ear hair cells

For the first time scientists have been able to grow cells that behave like the sound-sensitive hair cells found in the ears of humans and other mammals.

Little is actually known about the detailed molecular basis of the hearing process, mainly because the ear contains relatively few such cells – around 30,000 in humans for instance. Ear hair cells are also very difficult to keep alive for study once removed from the ear. This in part explains why the current results are the outcome of over 10 years of effort.

In fact hearing is the last of the human senses for which the molecular basis is unknown. That is why this is a significant breakthrough as it is in part our inability to regenerate these cells as we grow older that contributes to age-related hearing loss.

The scientists, from the Stanford University School of Medicine, modified stem cells taken from mouse embryos using a new technique that they developed as part of the study.

Close examination showed that the modified cells had all the characteristics of hair cells, growing in tufts and responding to vibrations - the key to their part in the hearing process. When subjected to vibrations the cells produced an electrical current. In the hearing process fluid in the ear vibrates in response to sound waves, and this vibration is transferred to hair cells which in turn generate electrical signals which are sent to the brain to be treated as sound.

Study leader Stefan Heller explained that the findings are significant because mammals, unlike some other animals, are unable to re-generate ear hair cells: "For some reason, we've lost this mechanism but it must still be there. Somehow we need to find ways to activate it."

The study is published in the May 2010 edition of the journal Cell.

This article was published on Fri 14 May 2010