p16 Cellular Senescence and Vascular Dysfunction in Sleep Apnea - PROJECT SUMMARY/ABSTRACT Obstructive Sleep Apnea (OSA) is the most severe form of Sleep-Disordered-Breathing (SDB), and is extremely prevalent, affecting nearly a billion adults worldwide. OSA-associated morbidities affect virtually all organ systems via activation and propagation of oxidative stress and systemic inflammatory pathways, de facto mimicking accelerated biological aging. In particular, OSA is widely recognized as an independent cardiovascular risk factor, associated with incident obesity, atherosclerosis, hypertension (HTN), endothelial dysfunction, arrhythmias, stroke, coronary artery disease (CAD) and heart failure. Both epidemiologic and intervention-based studies have provided conclusive evidence indicating a causative link between OSA and cardiovascular morbidity. However, the physiological and molecular mechanisms of OSA-induced vascular senescence leading to vascular dysfunction remain to be elucidated. The cyclin dependent kinase inhibitor 2A (CDNK2A), also known as p16, is a protein that slows cell division, and its upregulation is a hallmark of cellular senescence in both mice and humans. Recently, selective elimination of cells highly expressing the p16 protein (commonly referred to as p16high cells) was shown to improve and reverse aging-associated diseases. Whether targeting vascular senescence can improve vascular outcomes in OSA has not been investigated yet. In this project, it is hypothesized that chronic exposures to Intermittent Hypoxia (IH) and Sleep Fragmentation (SF), two main features of OSA that can be reproduced in mouse models, will induce accelerated vascular senescence in mice manifesting as vascular dysfunction. As a corollary, it is proposed that eliminating p16high cells may reverse or attenuate IH- and SF-mediated vascular deficits. Three different transgenic mouse models will be used: i) containing a p16 reporter, ii) enabling systemic ablation of p16high cells, and iii) enabling the specific ablation of p16high vascular endothelial cells (vECs). These models will be exposed to IH, SF and the combination of both (IH+SF), to investigate the phenotypic effects and molecular mechanisms of OSA-induced cardiovascular senescence, and their reversibility through selective elimination of senescent cells in the vasculature. Physiological and cardiovascular changes will be assessed at predetermined time points. By studying DNA methylation profiles at each time points, it will be determined whether such exposures will induce an acceleration in the biological age compared with the chronological age. This is referred to as “Epigenetic Age Acceleration” and constitutes a novel approach for quantifying aging at systemic and tissue-specific level. Furthermore, by studying whole genome DNA methylation and RNA profiles in tissues, isolated vECs and primary vECs cultures, the pathways, and molecular networks responsible of the OSA-induced vascular senescence and function will be investigated. This project will create a novel and innovative framework in OSA, by mechanistically demonstrating the impact of cellular senescence on OSA-induced cardiovascular dysfunction and providing a potential actionable target for therapeutic development.
