Stem Cells Regrow Crucial Hearing Cells in Mice

Maggie Fox, Health and Science Editor, May 13, 2010

Hearing loss is a significant problem. According to the National Institute on Deafness and Other Communication Disorders 15 percent of Americans between 20 and 69, or 26 million people, have high frequency hearing loss caused by noise. Antibiotics and genetic disorders have also been identified as causative factors.

Recently a study led by Dr. Kazuo Oshima of Stanford University in California demonstrated that it is possible to generate the cells in the ear that are responsible for hearing from two types of mouse stem cells. By treating embryonic stem cells or a similar type of stem cell generated from the skin called "induced pluripotent stem cells", with a mixture of small molecules and proteins, the scientists where able to produce hair cells. These cells are covered with bristles called stereocilia which recognize sound waves and as they bend in response to the sound waves chemical channels open, which create an electrical signal that can be carried to the brain. Although it is dogma that once the hair cells are damaged, they cannot be replaced, some studies do suggest that adult stem cells are involved in repair after injury (Lang et al. Contribution of bone marrow hematopoietic stem cells to adult mouse inner ear: mesenchymal cells and fibrocytes. J Comp Neurol. 2006 May 10;496(2):187-201).

Oshima's team believes the current finding has several implications. In a telephone interview he stated "What we are thinking is to get human iPS cells from hearing loss patients and just try to re-make the disorder in the petri dish." He continued "This could be used to screen drugs that might cause the cells to regenerate, or to activate hibernating stem cells in the ear, he said. It may also be possible to grow the cells and inject them into the ear, but no one has developed a technique for doing this."

When asked about the future of these experiments, Dr. Oshima commented "The next step is to try using human iPS cells, but it has not worked so far".

As a third-party assessment of the findings, Dr. David Corey, a professor of neurobiology at Harvard University in Massachusetts commented that "This gives us real hope that there might be some kind of therapy for regenerating hair cells," but on a negative note he continued "It could take a decade or more, but it's a possibility."