Figure 3. Influence of Selenium on replicative senescence. (A) Cumulative population doubling corresponds to the sum of population doubling over subculture passages until the last passage with holoclones. The percent increase is calculated as (KT Cumulative PD/KC Cumulative PD) x100 (KT: treated keratinocytes; KC: control keratinocytes). CFE was calculated at each passage over replicative life span where keratinocytes are still able to produce holoclones. (B) Example of colony morphology corresponding to the last cumulative PD/passages with holoclones. (Scale bar = 1cm) (C) Representative morphology of supplemented keratinocytes (small, cohesive and cobblestone keratinocytes) or control keratinocytes (senescence-associated phenotype with differentiated cells) at a late passage. Representative photographs are shown (scale bar=500 µm; n=3 donors).