Is beta-galactosidase staining a marker of senescence in vitro and in vivo?

Cytochemically detectable beta-galactosidase (beta-gal) at pH 6.0 has been reported to increase during the replicative senescence of fibroblast cultur es and has been used widely as a marker of cellular senescence in vivo and in vitro. In this study, we have characterized changes in senescence-associ ated (SA) beta-gal staining in early and late passage cultures, cultures es tablished from donors of different ages, virally immortalized cells, and ti ssue slices obtained from donors of different ages. The effects of differen t culture conditions were also examined, While we confirm the previous repo rt that SA beta-gal staining increased in low-density cultures of prolifera tively senescent cells, we were unable to demonstrate that it is a specific marker for aging in vitro. Cultures established from donors of different a ges stained for SA beta-gal activity as a function of in vitro replicative age, not donor age. We also failed to observe any differences in SA beta-ga l staining in skin cells in situ as a marker of aging in vivo. The level of cytochemically detectable SA beta-gal was elevated in confluent nontransfo rmed fibroblast cultures, in immortal fibroblast cultures that had reached a high cell density, and in low-density, young, normal cultures oxidatively challenged by treatment with H2O2. Although we clearly demonstrate that SA beta-gal staining in cells is increased under a variety of different condi tions, the interpretation of increased staining remains unclear, as does th e question of whether the same mechanisms are responsible for the increased SA beta-gal staining observed in senescent cells and changes observed in c ells under other conditions. (C) 2000 Academic Press.