Podocyte Aging with and without Hypertension: A Comparative Study in Young and Middle-Aged Mice
Recent studies show that acute injury to non-aged podocytes induces many similarities to healthy aged podocytes, such as decreased lifespan and health-span. Like healthy aged podocytes, injury to young mouse and human podocytes can induce a senescent phenotype. This begs the question if injury to young podocytes phenocopies a healthy middle-aged podocyte, and if the pathways underlying senescence and other injury responses overlap between injured young podocytes and healthy middle-aged podocytes. To address this knowledge gap we induced hypertension, a major cause of chronic kidney disease, in young mice (4m of age~20-year-old human) and in middle-aged mice (18m of age, ~55+ year old human) with deoxycorticosterone and high salt (DOCA) and compared outcomes to non-hypertensive healthy middle-aged mice. In both healthy middle-aged mice and in young mice with hypertension, the increase in age-related senescent genes p16 and p19, along with the stress-related senescent genes p21 and p53 were similar. Bulk RNA-sequencing of podocytes showed that the senescent associated secretory phenotype and individual genes from several aging gene sets were also similar between middle-aged mice and young mice with hypertension. Of the highest enriched Hallmark pathways in middle-aged podocytes, 95% were also enriched in young mice treated with DOCA. Gene set enrichment analysis of podocytes showed that 36 genes overlapped between middle-aged mice, and young and middle-aged mice given DOCA, while 119 genes identified were “DOCA-specific”. These results suggest that hypertension in young mice induces podocyte injury and an aging/senescent phenotype that is similar to the one of podocytes from healthy middle-aged mice. Overall design: 18 months-old C57BL/6J mice were separated into two groups, (i) a treatment group of mice with Deoxycorticosterone Acetate Salt (DOCA) along with ad libitum access to saline water for 6 weeks and (ii) an untreated control group. Kidneys were removed from the mice at 19.5 months. Podocytes we isolated by MAC sorting and injury and senescence were assessed with mRNA sequencing.