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. 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.
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.