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Updated: May 18, 2026

In Vivo Functional Assessment of Rat Masseter Muscle Following Surgical Creation of a Volumetric Muscle Loss (VML) Injury
Published on: November 15, 2024
Age-related changes in rat genioglossus, geniohyoid and masseter muscles
Syuhei Kaneko1, Ryo-hei Iida, Takeo Suga
1Department of Geriatric Dentistry, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
Objectives:
The aim of this study was to elucidate age-related changes from adult to middle age in the contractile properties of the masseter, genioglossus and geniohyoid muscles of the rat.
Materials And Methods:
We analysed the expressions of myosin heavy chain (MyHC) mRNAs and proteins as indicators of the contractile properties in these muscles obtained from rats at 6, 12, 18 and 24 months of age using real-time PCR and SDS-PAGE.
Results:
We found no marked age-related changes in the expressions of MyHC mRNAs and proteins in rat masseter and geniohyoid muscles, suggesting that the biological ageing process does not affect contractile properties in these muscles. However, we found a decrease in the expression of MyHC IIb mRNA with ageing in the rat genioglossus muscle, suggesting that biological ageing process induces at least some fast-to-slow myofibre phenotype transition.
Conclusion:
The biological ageing process from adult to middle age appears to differentially affect different types of craniofacial muscles.
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