IADR Abstract Archives
Can the Masseter Muscle Progressive Muscle Atrophy Due to Aging?
Objectives: There is a problem regarding the medical economy of the increasing long-term care required by the elderly in Japan. It is conceivable that sarcopenia(muscle weakening) in limb muscles is the beginning of aging-related problems that require long-term care. The association between sarcopenia and mastication function was reported in J. Gerontology, it is thought that sarcopenia of the mastication muscle and decreased mastication function are related. This study investigated aging-related changes in masseter muscles from a morphological and immunohistochemical standpoint with the objective of determining the influence of muscle atrophy on the mastication function.
Methods: This study used SAMP8(senescence-accelerated mouse prone 8) at the ages of 12 week(youth),40 weeks (old age),55 weeks (the late stage of old age).The assessment method included body weights, muscle wet weights, the means of muscle fiber cross-sectional areas (MCSA)and immunohistochemical observation (the percentage of constituent MyHC-IIa，MyHC-IIb). Tukey’s test was used as a post-hoc analysis of variance for a comparison between the SAMP8 age groups.
Results: The mean of MCSA decreased from12 weeks to 40 weeks and from 12 weeks to 55 weeks. Immunohistochemical staining results showed that the percentage of constituent MyHC-IIa increased from 12 weeks to 55 weeks. Furthermore, the percentage of constituent MyHC-IIb decreased from 12 weeks to 55 weeks and 40 weeks to 55 weeks.
Conclusions: It has been reported that MCSA is proportional to muscle strength, Additionally, it was suggested that muscle atrophy of the SAMP8 masseter muscle occurs by 40 weeks. It is conceivable that changes in the percentage of constituent MyHC-IIa and MyHC- IIb may occur in the contraction characteristics of the masseter muscle much like they do those in the leg muscles. Additionally, it was suggested that these changes have an effect on mastication function.
Methods: This study used SAMP8(senescence-accelerated mouse prone 8) at the ages of 12 week(youth),40 weeks (old age),55 weeks (the late stage of old age).The assessment method included body weights, muscle wet weights, the means of muscle fiber cross-sectional areas (MCSA)and immunohistochemical observation (the percentage of constituent MyHC-IIa，MyHC-IIb). Tukey’s test was used as a post-hoc analysis of variance for a comparison between the SAMP8 age groups.
Results: The mean of MCSA decreased from12 weeks to 40 weeks and from 12 weeks to 55 weeks. Immunohistochemical staining results showed that the percentage of constituent MyHC-IIa increased from 12 weeks to 55 weeks. Furthermore, the percentage of constituent MyHC-IIb decreased from 12 weeks to 55 weeks and 40 weeks to 55 weeks.
Conclusions: It has been reported that MCSA is proportional to muscle strength, Additionally, it was suggested that muscle atrophy of the SAMP8 masseter muscle occurs by 40 weeks. It is conceivable that changes in the percentage of constituent MyHC-IIa and MyHC- IIb may occur in the contraction characteristics of the masseter muscle much like they do those in the leg muscles. Additionally, it was suggested that these changes have an effect on mastication function.