Its existence was proposed in 1995 by Dimri et al.[3] following the observation that when beta-galactosidase assays were carried out at pH 6.0, only cells in senescence state develop staining. They proposed a cytochemical assay based on production of a blue-dyed precipitate that results from the cleavage of the chromogenic substrate X-Gal, which stains blue when cleaved by galactosidase. Since then, even more specific quantitative assays were developed for its detection at pH 6.0.[4][5][6]
Today this phenomenon is explained by the overexpression and accumulation of the endogenous lysosomalbeta-galactosidase specifically in senescent cells.[7] Its expression is not required for senescence.[7] However, it remains as the most widely used biomarker for senescent and aging cells, because it is easy to detect and reliable both in situ and in vitro.[citation needed]
Yang NC, Hu ML (October 2005). "The limitations and validities of senescence associated-beta-galactosidase activity as an aging marker for human foreskin fibroblast Hs68 cells". Exp. Gerontol. 40 (10): 813–9. doi:10.1016/j.exger.2005.07.011. PMID16154306. S2CID30500511.