Umbrella Cells, Bladder Uroepithelial Cells that Exhibit Senescence Features Throughout the Mouse Lifespan, Are Not Depleted by Senolytics
Lower urinary tract dysfunction (LUTD) increases with aging. Ensuing symptoms including incontinence greatly impact quality of life, isolation, depression, and nursing home admission. The aging bladder is hypothesized to be central to this decline, however, it remains difficult to pinpoint a singular strong driver of aging-related bladder dysfunction. Many molecular and cellular changes occur with aging, contributing to decreased resilience to internal and external stressors, affecting urinary control and exacerbating LUTD. In this study, we examined whether cellular senescence, a cell fate involved in the etiology of most aging diseases, contributes to LUTD. We found that umbrella cells (UCs), luminal barrier uroepithelial cells in the bladder, show senescence features over the mouse lifespan, identifying a novel non-aging related senescent cell population. While these senescent UCs may help maintain the blood-urine barrier, a novel example of beneficial senescence, they could also contribute to the generation of urothelial cancers and LUTD (antagonistic pleiotropy). These senescent UCs were not eliminated by the senolytic combination of Dasatinib and Quercetin, thus ensuring an intact blood-brain barrier when these agents are used in humans. We also tested the effect of a high fat diet and senescent cell transplantation on bladder function and showed that both models cause similar cystometric changes as natural aging in mice, with no effect of senolytics on HFD-induced changes. These findings illustrate the heterogeneity of cellular senescence in varied tissues, highlighting the importance of considering the safety of barrier cells in the bladder and possibly elsewhere during development and testing of future senolytics. Overall design: RNAseq was done on whole mouse bladders from young (2 months), middle aged (10 months) and old (26 months) female C57BL/6 mice  and from old female mice treated with water, vehicle (60% Phosal 50 PG, 30% polyethylene glycol 400, 10% ethanol) , or D+Q (5mg/kg/day dasatinib and 50mg/kg/day quercetin)  once a month for 3 consecutive days from 21 to 26 months by oral gavage. Total RNA was extracted from whole bladders for RNAseq. 4-6 bladders per age/condition were run.