Skeletal Muscle Activity and the Fate of Myonuclei

Abstract

Adult skeletal muscle fiber is a symplast multinuclear structure developed in ontogenesis by the fusion of the myoblasts (muscle progenitor cells). The nuclei of a muscle fiber (myonuclei) are those located at the periphery of fiber in the space between myofibrils and sarcolemma. In theory, a mass change in skeletal muscle during exercise or unloading may be associated with the altered myonuclear number, ratio of the transcription, and translation and proteolysis rates. Here we review the literature data related to the phenomenology and hypothetical mechanisms of the myonuclear number alterations during enhanced or reduced muscle contractile activity. In many cases (during severe muscle and systemic diseases and gravitational unloading), muscle atrophy is accompanied by a reduction in the amount of myonuclei. Such reduction is usually explained by the development of myonuclear apoptosis. A myonuclear number increase may be provided only by the satellite cell nuclei incorporation via cell fusion with the adjacent myofiber. It is believed that it is these cells which supply fiber with additional nuclei, providing postnatal growth, work hypertrophy, and repair processes. Here we discuss the possible mechanisms controlling satellite cell proliferation during exercise, functional unloading, and passive stretch.

Compensatory anabolic signaling in the sarcopenia of experimental chronic arthritis

“…According to our data, animals with AiA displayed signs of simultaneous muscle wasting and repair. The myonuclear expansion observed in arthritic rabbits is an anatomical marker of muscle growth and regeneration 42 . Indeed, myonuclei number has been shown to increase after sarcopenic challenge in rats 43 .…”

No-dependent signaling pathways in unloaded skeletal muscle

“…Some authors have linked increased muscle mass with the higher content of myonuclei and activation of the satellite cells in muscle (Wang et al, 2006 ; Shenkman et al, 2010 ). A decrease in NO concentration was previously reported to lower the ability of satellite cells to proliferate.…”

“…A decrease in NO concentration was previously reported to lower the ability of satellite cells to proliferate. An increase in the number of satellite cells was prevented by administration of L-NAME in stretched muscle (Shenkman et al, 2010 ). This suggests that satellite cell activation and proliferation is a NO-dependent process (Kartashkina et al, 2010 ).…”

The molecular mechanisms of probiotic strains in improving ageing bone and muscle of d ‐galactose‐induced ageing rats

“…Quantity of myonuclei are of significance as it ensures the content of nucleic acid for gene transcription, therefore the overall functionality of muscle (Shenkman et al . 2010). An elevated myonuclei signifies the impact of hypertrophy, which refers to increase in size of muscle cells, usually due to physical exercise such as weightlifting and/or training (Bruusgaard et al .…”