Figure 2. Accumulation of cells with short telomeres with aging. In old individuals, the accumulation of apoptotic/sencescent cells with critically short telomeres as well as the loss of the regenerative potential of the stem cell pools as a consequence of telomere shortening, compromise tissue function and tissue regenerative capacity, contributing to organism aging. For this reason, the frequency of short telomeres, rather than the mean TL, is determinant for telomere dysfunction, and, consequently, for cell and tissue dysfunction. This fact points out the importance of measuring the frequency of short telomeres rather than the mean telomere length.