Fig. 6

Aged Sox2+ stem cells generate β-catenin-accumulating cell clusters with reduced senescence and SASP responses. a Schematic diagram of the experimental designs. Sox2^CreERT2/+;Ctnnb1^lox(ex3)/+;R26^YFP/+ and Sox2^CreERT2/+;R26^YFP/+ mice were tamoxifen induced at either 1 or 6 month of age and the anterior pituitary collected 4 weeks post induction and processed for histological and molecular analysis of YFP+ cells isolated by FACS (n = 8 mice per group). b Double immunostaining on histological sections of Sox2^CreERT2/+; Ctnnb1^lox(ex3)/+; R26^YFP/+ pituitaries revealing the presence of β-catenin-accumulating cell clusters positive for p21, but not for Ki67. Scale bar: 100 µm. c Quantitative analysis showing a significant higher Ki67 proliferation index in non-cluster cells in Sox2^CreERT2/+;Ctnnb1^lox(ex3)/+;R26^YFP/+ tumoural relative to Sox2^CreERT2/+;R26^YFP/+ control pituitaries in tamoxifen-induced mice at 1 month (black asterisk), but not at 6 months. Increased proliferation index is also observed in non-cluster cells in Sox2^CreERT2/+;Ctnnb1^lox(ex3)/+;R26^YFP/+ pituitaries of mice induced at 1 month relative to those induced at 6 months (red asterisk). d qRT-PCR analysis showing the upregulation of the WNT pathway target genes Axin2 and Lef1, as well as of several senescence and SASP factors in the Sox2^CreERT2/+;Ctnnb1^lox(ex3)/+;R26^YFP/+ mutant pituitaries relative to the Sox2^CreERT2/+; R26^YFP/+ controls. e qRT analysis showing the relative expression of several senescence and SASP factors in Sox2^CreERT2/+;Ctnnb1^lox(ex3)/+;R26^YFP/+ mice tamoxifen induced at either 1 (young) or 6 (older) months of age. The expression of several senescent and SASP factors is significantly reduced in the older compared with the young mice. Bars in c, d and e represent the mean, and error bars represent standard error of the mean (SEM) of three biological replicates. *p < 0.05, **p < 0.01, ***p < 0.001, Student’s t test