Elimination of physiological senescent cutaneous cells in a novel p16-dependent senolytic mouse model impacts lipid metabolism in skin aging

The evidence of the correlation between cellular senescence and aging has increased in research with animal models. These models have been intentionally generated to target and regulate cellular senescent cells with the promoter activity of p16^Ink4a or p19^Arf, genes that are highly expressed in aging cells. However, the senolytic efficiency in various organs and cells from these models represents unexpected variation and diversity in some cases. We have generated a novel knock-in model, p16tdT-hDTR mice, which possess tdTomato and human diphtheria toxin receptor (hDTR) downstream of Cdkn2a, an endogenous p16^Ink4a gene. We successfully demonstrated that p16-derived tdTomato and hDTR expressions are observed in these mouse embryo fibroblasts and following treatment with diphtheria toxin (DT) eliminates those cells. Furthermore, we demonstrated the efficacy of eliminating p16-positive cells in vivo, and also observed a tendency to decrease their cutaneous SA-β-gal activity after subcutaneous DT injection into p16tdT-hDTR mice. In particular, comprehensive gene expression analysis in skin revealed that upregulated genes related to lipid metabolisms with aging exhibited remarkable expressions under the senolysis. These results clearly unveiled p16-positive senescent cells contribute to age-related changes in skin.