Physical exercise positively affects activation and differentiation in vitro of satellite cells from skeletal muscles of sarcopenic mice

Ageing is associated with a progressive loss of muscle mass, strength and function: this condition is known as sarcopenia and represents an important risk factor for physical disability in elderly. The mechanisms leading to sarcopenia are still largely unknown and no specific therapy is presently available to counteract its onset or progress. Many studies have stressed the importance of physical exercise as an effective approach to prevent/limit the age-related muscle mass loss. We evaluated the effects of physical exercise on the activation and differentiation potential of cultured satellite-cell-derived myoblasts obtained from quadriceps muscles of old exercised, old sedentary and adult sedentary (control) mice. Cytochemical and immunocytochemical techniques were applied at light and transmission electron microscopy. Our results demonstrated that: a) physical exercise induces an increase in number of activated satellite cells; b) myoblasts from exercised muscles show morphological features quite similar to myoblasts from adult subjects, whereas myoblasts from non exercised muscles exhibit nuclear and cytoplasmic alterations suggestive of a reduced metabolic activity; c) myotubes differentiated from myoblasts of exercised muscles resemble the myotubes from adult myoblasts, whereas myotubes from non exercised muscles show marked structural alterations, especially in the cytoskeletal apparatus.