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November 18, 2019
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 Monell Chemical Senses Center

Guardians of the Gums: Special Sensory Cells Protect Us Against Bad Oral Bacteria

Specialized chemical-sensing cells throughout the body are always on the look-out for germs and other harmful substances. When they detect pathogens, the immune system is called into action for protection. In the last several years, scientists have found these cells, known as solitary chemosensory cells (SCCs), in the gut, sinuses, airways, and many other tissues.

Guardians of the Gums

Recently, researchers from the Monell Chemical Senses Center and their colleagues added another location to this list: the gums, where SCCs protect the mouth by standing guard against infections that damage soft tissue and destroy the bone that supports the teeth. 

Monell Center Director and President Robert Margolskee, MD, PhD and cell physiologist Marco Tizzano, PhD, along with colleagues from Sichuan University, found that bitter taste receptors on SCCs detect byproducts from harmful bacteria and trigger immune cells to control the amount and type of bacteria in the mouth. They reported the findings of this animal study in the scholarly journal Nature Communications.

“These sensory cells may provide a new approach for personalized treatment of periodontitis by harnessing a person’s own innate immune system to regulate their oral microbiome,” said Margolskee. Periodontitis is a serious gum disorder induced by an imbalance in the bacteria and other microorganisms of the mouth, also known as the oral microbiome. Gum disease is the sixth-most prevalent infectious disease and the most common cause of tooth loss worldwide. 

Genetically manipulating the SCCs to become non-functional led to an overgrowth of pathogenic oral bacteria and periodontitis. On the other hand, stimulating the bitter taste receptors in SCCs promoted the production of anti-microbial molecules.  

“Our study adds to a growing list of tissues we now know contain SCCs and indicates that the common molecular pathways in gum SCCs are involved in the regulation of bacteria in the mouth,” said Tizzano. 

Normally, SCCs express several types of taste receptors along with a critical receptor coupling protein called gustducin. Removing gustducin from the SCCs led to a more damaging set of microbes in the mouth of transgenic mice used in the study, suggesting that the lack of gustducin impairs the SCCs’ sentinel functions. Interestingly, the oral bacterial composition of the gustducin-deficient mice began to differ from normal mice even before any loss of bone in the gums, implying changes in the oral microbiome could signal gum disease before it became difficult or impossible to reverse. 

From this animal study, and unpublished work in humans, the team expects that gum SCCs in humans play a similar role in regulating the make-up of the oral microbiome, noted coauthor Xin Zheng, a dental science researcher from the National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology. Given that genetic differences in taste receptors are commonly detected in people and that bitter taste receptors on SCCs are vital to the oral immune response, it may be possible to use a taste test for a dental chair-side screening of patients who may be more susceptible to oral infectious diseases. 

This work was supported by the National Institute on Deafness and Other Communication Disorders, the National Natural Science Foundation of China, the National Science Foundation, and institutional funds from the Monell Center.

For more on this research, head to the Monell Center.
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