Figure 1.

SA-β-gal activity in compound-treated wells compared with activity at 2 days results in the identification of false-positive senescent inducers. Images of cultured human iPSC-derived astrocytes. Untreated control well (left column) fixed on day-2 postplating (the same day that compounds were added to wells). Well treated with 40 μM acetaminophen (included in the library as a negative control for NT) for 24 h and fixed on Day-7 postplating. Staining for SA-β-gal activity (top) and with DAPI (middle) reveals that the number of SA-β-gal+ astrocytes (arrows) has increased substantially over 5 days (postacetaminophen treatment). However, acetaminophen had the second lowest %SA (18.6) of any compound tested, demonstrating that comparing day-2 untreated with toxin-treated at day-7 results in false-positives.