Physical resilience is a predictor of healthy aging

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Abstract Physical resilience is a predictor of healthy aging (Competitive renewal) The ability to respond to and recover from a physically stressful event is defined as physical resilience. The inherent individual variation in response to a physical stressor suggests that different stressors trigger different stress response patterns. A deeper understanding as to why some individuals maintain or regain function following an insult, while others do not, may help to characterize protective factors that can be engaged to promote resilience and healthy aging. We have developed and partially characterized three translationally relevant physical stressors in mice: acute sleep disruption (ASD), the chemotherapeutic drug cyclophosphamide (CYP), and acute cutaneous trauma (ACT), that trigger responses showing a correlation with physiological and pathological features associated with increasing age. We have shown in the first grant period that ASD, CYP, and ACT administered to middle-aged mice results in a range of responsiveness from low to high, such that mice can be categorized as resistant or susceptible and aligned with phenotypic and geropathologic parameters of aging. The hypothesis of the competitive renewal is that resilience to aging is characterized by heterogeneous response patterns unique to defined physical stressors in an age- dependent manner. Aim 1 is designed to validate physiological targets of ASD, CYP, and ACT. Responsiveness will be determined by readout assays (escape times in a learning task for ASD, neutrophil to lymphocyte ratio for CYP, and biopsy healing area for ACT) in middle aged mice as resistant or susceptible to each physical stressor. Each group of mice will then be followed to older age and aligned with phenotypic aging endpoints including assessments for memory, strength and agility. Aim 2 is designed to confirm organ- based targets of ASD, CYP, and ACT in tissues from Aim 1 mice using endpoints based on differences in geropathology lesion scores in specific organs from the two groups. Digital imaging and biostatistical paradigms for mouse PathoClock analyses will be used for evaluation of organ-specific and organ-common geropathology data. Aim 3 is designed to identify and characterize molecular pathways of ASD, CYP, and ACT in tissues from Aim 1 mice and employ RNA seq for transcriptomic pathway analysis followed by verification with nanoscale protein analytical platforms and immunohistochemistry imaging for molecular analysis of relevant pathways in stress resistant and stress susceptible mice. The data can then be aligned with data from Aims 1 and 2. Investigations into the molecular pathways utilized by cells in a particular tissue and organ in response to a physical stressor would be of merit in individuals predicted to be less resilient to aging and would have impactful significance for designing clinical studies to enhance healthy aging.