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Jaws Life – How exposure to hypoxia affects jaw cartilage growth

Researchers from Tokyo Medical and Dental University (TMDU) observed that jaw cartilage is not fully developed in neonatal mice exposed to periods of hypoxia.

TOKYO, Japan – Inhaling adequate amounts of oxygen is crucial to human life. However, certain disturbances can cause individuals to go through periods in which they are periodically exposed to low levels of oxygen, called intermittent hypoxia (IH). This is common in people with certain sleep disorders, such as obstructive sleep apnea. Although we know that IH can cause problems with neurodevelopment, it is not clear how it affects cartilage. Now, researchers at Tokyo Medical and Dental University (TMDU) have shown that IH can lead to underdeveloped jaw cartilage in mice.

In an article published in Scientific ReportsResearchers from TMDU have uncovered the inhibitory effects of IH on cell growth in the mandibular condylar cartilage, which is the cartilage at the rounded end of the jawbone. Previous work has focused primarily on how IH affects bone growth only.

Often cartilage within different parts of the body exhibits different metabolic properties. Studies have shown that cartilage in the jaw has different growth patterns and gene expression profiles compared to cartilage in the extremities, for example. Because of this, the TMDU group became interested in how IH affects both mandibular and tibial cartilage. They compared both regions to examining the growth of chondrocytes called chondrocytes. The researchers also investigated the expression levels of specific genes in the cartilage cells that could help them identify the stage of growth they were in.

“It’s very important to understand more about the effects of intermittent hypoxia because it can lead to important developmental problems,” says lead author Kochakorn Lekvijittada. “It could even be preceded by sudden infant death syndrome (SIDS) – a terrifying and tragic event that unfortunately affected many families around the world.”

To answer their questions, the researchers used newborn mice as a model system. They exposed one group of 1-week-old mice to the air with normal amounts of oxygen, while another group of mice were exposed to alternating cycles of air as the oxygen levels decreased. Then the researchers investigated the effects on jaw and tibial cartilage growth.

Lead author Professor Takashi Ono describes: “We have observed inhibitory growth of cartilage in the jaws of mice.” Interestingly, the tibial cartilage was not affected by exposure to hypoxic air.

The authors also noted decreased expression levels of two genes called TGF-and SOX9 in jaw cartilage in mice exposed to IH, while another gene called collagen X showed increased expression.

“The patterns of gene expression that we observed in the jaw cartilage in the hypoxic mice were consistent with inflation,” says Dr. Lakvigitada. This indicates that the jaw cartilage was growing in a limited way. We have not seen these patterns in the tibial cartilage. ”

The results of this study provide new insight into how exposure to periods of low oxygen levels can affect jaw cartilage growth and development with potential applications in orthopedics and the diagnosis of temporomandibular disorders. This work also provides further understanding of how cartilage varies throughout the body depending on its location.

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The article, “Intermittent hypoxia inhibits maxillary cartilage growth with reduced TGF-and SOX9 expressions in neonatal mice” was published in Scientific Reports In the DOI: 10.1038 / s41598-020-80303-3

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