The effect of low oxygen tension on the in vitro-replicative life span of human diploid fibroblast cells and their transformed derivatives

Human diploid fibroblasts (HDF) IMR90, starting at various population doubling levels (PDL), were serially cultured under four different oxygen conditions; the conventional atmospheric 20% O₂ condition and three lower oxygen conditions (1,6, and 12% O₂). All cultures from different PDLs showed that a longer replicative life span was achieved under the lower oxygen conditions. When the starting culture PDL was between 33 and 62, the increased life span rate was constant (average 22%) at 1% O₂, but the rate decreased when the starting PDL was higher. The growth advantage under the 1% O₂ condition was also observed in the very late passages of cultures to some extent, but terminal cultures with senescent cells were not stimulated by the low oxygen condition. When cultures at an extended PDL under the 1% O₂ condition were shifted back to the 20% O₂ condition, the cells rapidly senesced. HDF from a subject with Werner syndrome, a premature aging disease, which are known to have reduced replicative potential in vitro, also showed 43% increase in life span under the lowest oxygen conditions. When SV40 large T-transformed IMR90 cells at preimmortal stages were tested, no significant growth differences were observed under different oxygen conditions, and all the cultures died out at a similar PDL. These results suggest: (1) The atmospheric 20% oxygen tension hastens HDF senescence. (2) Young cells are more resistant to oxygen tension than old cells. (3) SV40 large T transformation abolishes the oxygen effect on cellular aging.