Researchers find reserve cells in nose

Examiner ^ | 05.09.07 | Karl B. Hille

[Coleus]

Old paint cans, dry cleaner solvents, new car smell and other toxic chemicals you might catch a whiff of do more than warn you of danger — they can kill the cells in your nose that raise the alarm. Johns Hopkins University researchers identified a backup supply of stem cells that can repair the most severe damage to nerves responsible for the sense of smell. These “reservists” normally lie around and do nothing, but when neighboring cells die, they jump into action. A report on the discovery is available on Nature Neuroscience’s Web site.

“We’re particularly interested in the nerve cells in your nose because they continually turn over,” said lead author Randall Reed, professor of neuroscience at Johns Hopkins. “These stem cells act like the Army Reserves of our nose, supporting a class of active-duty stem cells that help repair normal wear and tear. They don’t come in until things are really bad.” The process is most similar to the regrowth of skin tissue, he said, which also comes under constant assault from the environment. Reed’s team discovered that newly grown smell cells in mice with damaged olfactory tissue grew from horizontal basal cells (HBCs), a population of cells not previously known for repair abilities, according to the article.

“We were stunned because HBCs normally don’t grow much or do anything,” Reed said. “And the most surprising thing is that HBCs can grow into both nerves and non-nerve cells; they do so by generating the other active type of nasal stem cell.” When only the olfactory nerve cells are killed, the HBCs did nothing to repair the damaged cells but allowed the previously known stem cells to do all the repair work, the report said.

The sense of smell is crucial for feeding, mating and survival, Reed said. “The HBCs act as a fail-safe to ensure continued function of the sense of smell.” The findings raise interesting questions, he said, such as what triggers HBCs into action and whether similar cells exist in other nerve tissue such as the brain. The Howard Hughes Medical Institute and the National Institutes of Health funded the research. Cheuk Leung and Pierre Coulombe, also of Johns Hopkins, contributed to the article.