Intermittent Hypoxia Mimicking Sleep Apnea Induces Systemic and Tissue Specific Epigenetic Changes and p16-Mediated...

Obstructive Sleep Apnea (OSA) is a pervasive cardiovascular risk factor linked to accelerated aging and systemic inflammation. Intermittent hypoxia (IH)-a hallmark of OSA-induces cardiovascular decline, yet the underlying tissue-specific and systemic epigenetic mechanisms and the role of cellular senescence in the pathophysiology of OSA and associated cardiovascular disease (CVD) remain poorly understood.

C57BL/6J male mice were exposed to IH or room air (RA) for durations ranging from 7 to 210 days. Genome-wide DNA methylation profiling was conducted on left cardiac ventricle and peripheral blood mononuclear cells (PBMCs) samples. Differentially methylated positions (DMP; q<0.05) were identified between IH and RA groups and the impact of IH duration was studied using regression models. Epigenetic age acceleration (EAA) was calculated using a multi-tissue epigenetic clock. Furthermore, p16-reporter and targeted ablation mouse models (p16-Cre^ERT2-DTR-tdTomato) were utilized to assess the role of p16^Ink4a-mediated senescence in IH-induced vascular dysfunction.

Chronic IH exposures significantly increased systolic and diastolic blood pressure and altered endothelial function. Epigenetic analysis identified 5,747 and 1,307 DMLs in the left cardiac ventricle and PBMCs, respectively, with minimal overlap between tissues (n=163, p=8.03 × 10^-8; Fisher's Exact Test), indicating a highly tissue-specific epigenetic response. Both tissues exhibited an early peak in EAA at 7 days of exposure, differing in the trajectory in longer exposures. Pathway analysis linked these epigenetic changes to cardiac dysfunction and cellular senescence, specifically highlighting Cdkn2a gene, which encodes the p16 protein, a marker of cellular senescence. Immunofluorescence confirmed increased p16 expression in aortic endothelial cells following IH. Remarkably, systemic ablation of p16-expressing cells (i.e., p16^high cells), reversed IH-induced hypertension and restored coronary flow reserve to control levels.

IH induces duration-dependent, tissue-specific epigenetic dysregulation and accelerated biological aging. Our findings provide initial evidence that p16^Ink4a-mediated cellular senescence is a primary driver of OSA-induced cardiovascular morbidity and that targeting the senescent endothelium can revert vascular dysfunction, thereby establishing a novel mechanistic framework for cellular senescence as a therapeutic target in OSA.