Ultrastructure of Mitochondria in Skeletal Muscle Weakened by Sarcopenia during Aging

The processes of progressive decrease in muscle mass and weakening of mitochondrial function that occur during aging in skeletal muscles remain poorly understood as does, above all, the cause-and-effect relationship between the ultrastructure of mitochondria and atrophic processes in skeletal muscles. An ultrastructural study of the features of the internal structural organization of mitochondria during aging of skeletal muscle was carried out on representatives of rapidly aging mammalian species (Wistar rats, OXYS, mice) and representatives of long-lived species: the naked mole rat (Heterocephalus glaber) and human. Previously unknown, age-related structural changes in the internal organization of skeletal muscle mitochondria in OXYS rats at the age of 24 months are shown: the appearance in each mitochondria of local areas of altered arrangement of cristae in the form of stellate structures, as well as the presence of extremely large structural formations, apparently the result of destructive processes in mitochondria, as well as the appearance of mitochondria that are abnormal in size and internal ultrastructure. It was shown that structural changes in mice at the age of 10 months and naked mole rats at the age of 11 years were multidirectional. If disturbances in the normal ultrastructure in mice affected not only mitochondria but also muscle fibers and the sarcoplasmic reticulum, then not only no pathological changes are observed in mole rats but also, on the contrary, the powerfully developed structure of mitochondria indicates the functional activity of these organelles. For the first time, the ultrastructure of mitochondria in human skeletal muscle at the age of 68–81 and 25–28 years was compared using biopsy material. In elderly patients, the phenomenon of mitochondrial proliferation is shown: a compensatory structural response to mitochondrial dysfunction. Mitochondria are small, with a small number of cristae. In young people, the ultrastructure of mitochondria corresponded to classical ideas about the features of the structural organization of skeletal muscle mitochondria. Literary ideas about the possible role of autophagy in the development of aging processes are considered.