Age-dependent imbalance of the antioxidative system in human satellite cells.

The mature myofibres of human skeletal muscle are surrounded by a type of adult stem cell, known as the satellite cell, which lies outside the sarcolemma but within the basal lamina. These cells remain quiescent until external stimuli trigger their re-entry into the cell cycle. In humans, ageing is characterised by a progressive loss of muscle mass and strength (sarcopenia) associated with a decline in functional ability. One of the possible causes of this decline in muscle performance is a decrease in the antioxidative capacity of skeletal muscle, resulting in an abnormal accumulation of the reactive oxygen species (ROS) critical for cell life. The present study shows that: (i) the antioxidant activity of Catalase and Gluthatione transferase in satellite cells derived from the elderly is drastically reduced compared to that in cells isolated from young individuals; (ii) cell membrane fluidity is considerably different between the two age groups; and (iii) basal [Ca2+]i levels in satellite cells increase significantly in an age-dependent manner. In view of the data obtained, we hypothesise that the destabilising oxidative damage that occurs during ageing in skeletal muscle also affects quiescent satellite cells, which spend their life in close anatomic and functional contact with adult fibres. This status is derived from a decrease in the antioxidative capacity, and may negatively affect the ageing satellite cells ability to repair muscle.