The team of researchers found that stem cells in the mouth can accelerate the healing of various tissues after illness or injury.
Microbes that are constantly in the oral cavity and get there with food expose the mucous membrane of the mouth constant attacks. However, it heals quickly and in most cases without scarring.
Studies have confirmed that tissue damage in the mouth heals faster than skin damage. Scientists studied the oral stem cells in order to understand how tissues recover from injuries so quickly even under the constant influence of germs and mechanical interference during chewing.
Stem cells live in many types of adult tissue, including the mucous membrane in the mouth, called the oral epithelium. These stem cells can divide throughout life to replace damaged or diseased cells. Despite this unique feature, oral stem cells are not well understood.
A group of scientists from the University of North Carolina at Chapel Hill (UNC-CH) led by Drs. Kevin Byrd and Scott Williams Hill studied stem cells of the oral epithelium in normal conditions and in response to stress.
The study was supported by the NIH’s National Institute of Dental and Craniofacial Research (NIDCR), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and National Cancer Institute (NCI). The results were published in Cell Stem Cell on December 5, 2019.
Scientists marked and tracked oral epithelial stem cells in mice and compared cell behavior in different tissues of the oral cavity. The experiments revealed a new type of stem cell in the hard palate. These so-called ” slow-cycling” cells divide infrequently and are located in certain areas on the ridges of the hard palate.
Then, scientists studied the response of stem cells to various levels of stressful physical effects. In response to a small puncture wound in the hard palate of mice, slow-cycling cells began to rapidly divide and migrate to the damage zone to restore tissue. Feeding mice with soft food (compared to a regular diet with hard granules) caused the opposite reaction: stem cells shared less frequently.
By analyzing the RNA sequences of cells, scientists identified the Lrig1 gene, which showed high activity (expression) in the slow-cycling stem cells. LRIG1 expression decreased near wounds in the hard palate and increased in response to a soft diet. These findings suggest that LRIG1 plays an important role in slowing cell division under conditions of low stress. As a confirmation of the obtained data, scientists demonstrated that genetically modified mice with non-functioning Lrig1 observed increased division of stem cells.
“Overall, the results indicate that oral epithelial stem cells in the hard palate are sensitive to both genes and the environment, responding quickly to daily challenges such as eating and to higher-stress events like injury”, – Byrd says. “This knowledge could help scientists better understand how we get oral cancer, which is rare in the hard palate. It could also inform efforts to improve wound healing and tissue repair throughout the body.”
The study emphasizes not only the unique abilities of oral stem cells compared to similar tissues such as the skin, but also how these cells can become models for understanding rare diseases.