TUESDAY, Oct. 28, 2003 (HealthDayNews) -- A new way of using embryonic stem cells to grow hair cells that populate the inner ear may lead the way to new drug and surgical methods to treat progressive hearing loss, researchers report.
Deterioration of hair cells in the inner ear, leading to deafness, is a common problem, says lead researcher Stefan Heller, an assistant professor of otology and laryngology at Harvard Medical School.
Degeneration of inner ear hair cells can result from birth defects, wear and tear of the years, side effects from drugs, and aging.
These hair cells do not regenerate themselves, Heller adds. So far, people have not found a way to create hair cells, he notes. "We thought that it may be possible to create these cells from embryonic stem cells," Heller says.
Heller and his colleagues exposed embryonic stem cells from mice to a number of growth factors known to affect inner ear development. Once these cells had differentiated into hair cells, they transplanted them into the ears of chicken embryos.
Once in the chicken embryos, these cells became part of the inner ear and expressed genes and proteins of adult hair cells and they grew as existing hair cells would, according to the report in this week's issue of the Proceedings of the National Academy of Sciences.
"This gives us for the first time the option to create hair cells in the millions to do biochemical research," Heller says. "For example, we can use these cells to screen drugs that may make it possible to stimulate regeneration of hair cells. These drugs may be useful in restoring hearing."
The same research team had published a paper in the October issue of Nature Medicine, in which they show that stem cells from mice can differentiate into inner ear hair cells.
This finding may lead to the ability to transplant differentiated hair stem cells into human ears. However, this would require major improvements in surgical techniques beyond those currently in use, which destroy parts of the inner ear, Heller says.
"Our findings open a new avenue of research," he says. "We have moved the research from animals to the culture dish, where we can see drug reactions more easily. This is the most immediate benefit."
"In the long run this research may stimulate clinicians to start thinking about how to deliver cells or drugs safely to the inner ear," Heller adds.
Yehoash Raphael, an associate professor of otolaryngology at the University of Michigan Medical School, comments that "Heller's work constitutes important progress. Heller and his group demonstrate that mammalian embryonic stem cells can be manipulated to differentiate as hair cell progenitors and acquire many features of hair cells."
Raphael cautions, however, that what is true for chicken embryos isn't necessarily so for humans. "The leap from the chick embryo to the mature mammalian ear is not a trivial one," he says.
Raphael adds that both gene therapy and stem cell therapy "are promising advances for biological treatment of deafness. It is possible that a combination of the two technologies will get us closer to treatment of hearing loss."
More information
Get a primer on stem cells from the National Institutes Health , and learn about hearing loss from the National Institute on Deafness and other Communication Disorders.
