Fig. 6.

The enrichment of senescent cells in ageing mouse liver is accompanied by iron accumulation and elevated ferritin. (A) Senescent cells are markedly enriched in the livers of aged mice. Percentage of senescent cells in serial histological liver sections from both young (3 month; n = 4) and aged mice (30 month; n = 4) as determined by SA-βgal activity (blue staining). (B) ICP-MS analyses demonstrated a significant increase in iron (~ 2.5-fold) in liver tissues harvested from aged mice (30 month; n = 4) when compared to liver tissues harvested from young mice (3 month; n = 4). (C) The iron-storage protein ferritin and the senescence marker p16 were significantly elevated in livers of aged mice. (i) Western blot analyses and densitometry demonstrated that ferritin and p16 expression are increased in liver tissues harvested from aged mice (30 month; n = 3) when compared to liver tissues harvested from young mice (3 month; n = 3). β-actin was detected as a loading control. (ii) Quantitative real-time PCR analysis confirmed increased p16 transcript levels in liver tissues harvested from aged mice (30 months, n = 3), when compared to liver tissues from young mice (3 months, n = 3). (D) The percentage of ferritin-enriched cells within aged livers matched the percentage of SA-βgal positive senescent cells. Serial histological liver sections from both young (n = 3) and aged mice (n = 3) were stained for either SA-βgal activity or for ferritin. Images are representative of the mean percentage of either SA-βgal activity or ferritin staining from each mouse liver, as determined by observing 4 independent fields of view at a magnification of 400X using OlyVIA viewer software (ver2.4). Statistical analysis was performed by student-t-test: significant (*p < 0.05, **p < 0.01, ***p < 0.001). Data represented as mean ± SD (n = 3).