On the regenerative capacity of human skeletal muscle.

The proliferative capacity of organotypic muscle stem cells, the satellite cells, from nine healthy human donors aged between 2 and 78 years was investigated. There was a loss in proliferative capacity with age, but the oldest donors (76, 78 years) would still be able to replace their musculature several times. Depending on frequency of desmin-positive (i.e., myogenic) cells during prolonged expansion, myoblast cultures could be designated as stable or unstable. There was a weak correlation between mean telomere lengths (estimated by flow-FISH) and remaining mean population doublings until senescence. A bimodal distribution of mean telomere lengths was apparent in both stable and unstable myoblast cultures and could be assigned to populations of differently sized cells. Furthermore, due to the presence of nonmyogenic cells with longer telomeres, unstable cultures tended to show an increasing rather than decreasing mean telomeric length on expansion. Bimodal distributions in myoblast cultures could be due to hitherto undefined myoblast populations.