Using a mouse model of gum disease, researchers have uncovered a potential role for a newly discovered bacterium, according to a study in the May issue of Cell and Host Microbe. A similar bacterium in humans might be responsible for the inflammation and bone loss associated with gum disease.
Researchers at the University of Michigan identified a bacterium normally present in mouse oral flora that they named NI1060. This bacterium is associated with the development of a mouse model of periodontitis. The researchers discovered that NI1060 accumulated at sites where gum tissue was damaged and triggered a protein in the oral cavity that activates bone-destroying cells. Under normal circumstances, this protein, Nod1, fights harmful bacteria in the body.
"Nod1 is a part of our protective mechanisms against bacterial infection," said corresponding author Noahiro Inohara, Ph.D., research associate professor at the University of Michigan Health System, Ann Arbor. "It helps us to fight infection by recruiting neutrophils, blood cells that act as bacterial killers. It also removes harmful bacteria during infection. However, in the case of periodontitis, accumulation of NI1060 stimulates Nod1 to trigger neutrophils and osteoclasts, which are cells that destroy bone in the oral cavity."
Researchers also found that while Nod1 regulates the immune system’s response to NI1060, it does not cause NI1060 to accumulate at diseased gingival sites.
"The findings from this study underscore the connection between beneficial and harmful bacteria that normally reside in the oral cavity, how a harmful bacterium causes the disease, and how an at-risk patient might respond to such bacteria," said study co-author Dr. William Giannobile, professor of dentistry, and chair, Department of Periodontics and Oral Medicine at the University of Michigan School of Dentistry.
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