Extension of cell life-span and telomere length in animals cloned from senescent somatic cells

The potential of cloning depends in part on whether the procedure can rever se cellular aging and restore somatic cells to a phenotypically youthful st ate. Here, we report the birth of six healthy cloned calves derived from po pulations of senescent donor somatic cells. Nuclear transfer extended the r eplicative lifespan of senescent cells (zero to four population doublings r emaining) to greater than 90 population doublings. Early population doublin g level complementary DNA-1 (EPC-1, an age-dependent gene) expression in ce lls from the cloned animals was 3.5- to 5-fold higher than that in cells fr om age-matched (5 to 10 months old) controls. Southern blot and flow cytome tric analyses indicated that the telomeres were also extended beyond those of newborn (<2 weeks old) and age-matched control animals. The ability to r egenerate animals and cells may have important implications for medicine an d the study of mammalian aging.