Research Paper Volume 11, Issue 3 pp 950—973

Replicative senescent human cells possess altered circadian clocks with a prolonged period and delayed peak-time

Figure 1. Replicative senescence of TIG-3 cells. Cumulative (A) and individual (B) population doubling level (PDL) of TIG-3 cells were measured. (C) Pictures of SA-β-Gal positive cells (blue) at passage25 (P25) and 39 (P39) were taken. Scale bars represent 100 μm. (D) The percentage of SA-β-Gal positive cells were quantified at different passages. (E) p21CIP1 (upper panel) and p16INK4a (bottom panel) genes expression at different passages were analyzed by qPCR. The lowest expression level was set to 1. Three independent proliferation assays were performed. n.s., not significant, *p<0.05, ***p<0.001, compared to each lowest passage for (D) and (E), by Student’s two-tailed t test.