Targeting p21-Highly Expressing Cells to Increase Lifespan and Healthspan in Old Age

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Project Summary Chronological age is the leading risk factor for most chronic diseases, frailty, and mortality worldwide. Thus, the elderly population usually has multiple chronic conditions at the same time, resulting in poor health and reduced quality of life (prolonged morbidity period) at the later stage of life. There is a big challenge to compress morbidity period and increase healthspan (lifespan with good health). In this project, we propose to examine the role of p21high senescent cells in lifespan and healthspan. We have generated and validated a new p21-Cre transgenic mouse model containing a p21 promoter driving a bicistronic message consisting of Cre fused to a tamoxifen- inducible estrogen receptor (ER) element. This model enables us to monitor, sort, kill or modulate p21high cells with aging in vivo. Our preliminary data shows that p21high and p16high cells are two distinct cell populations, and the p21-Cre mouse model targets 1.5-10% of cells in various tissues in 23-month-old mice. Monthly clearance of p21high cells in mice starting at 20 months reduces frailty index, extends lifespan, and more importantly, improves physical function at the end of life. In this proposal, we will further characterize the role and mechanisms of p21high cells in lifespan and healthspan. Our overarching hypothesis is that targeting p21high cells can extend lifespan and compress morbidity in old age. In aim 1.1, we will investigate whether clearance of p21high cells could extend lifespan and healthspan using a larger group size. We will examine potential sex difference and perform postmortem pathological analysis to examine the cause of death and disease burden. Moreover, we will follow physical function and frailty index of these mice every month from 20-month-old to the end of life to assess late life health status. In aim 1.2, we will leverage p21-Cre mouse models to sort and enrich p21high cells from 6 tissues of 23-month-old mice where we observed p21high cells (2-10%), and perform single cell RNA sequencing on these cells along with non-p21high cells. In addition, we will perform single nucleus sequencing and imaging mass cytometry. In aim 2, we will investigate the role of NF-κB pathway in p21high cells in lifespan and healthspan shortening. This project is likely to have a broad impact on aging research by gaining a comprehensive understanding of p21high cells at both functional and transcriptomic levels in vivo. Results from this project will also enable future testing of pharmacological interventions that eliminate these cells to improve lifespan and compress morbidity.