Ventricular assist device unloading reverses microvascular senescence in single ventricle disease.

Individuals with hypoplastic left heart syndrome (HLHS) have an underdeveloped left ventricle and require surgery to reconfigure blood flow for survival. Here we profiled the HLHS right-ventricular microenvironment by single-nucleus RNA sequencing and spatial transcriptomics at birth (before heart failure), after surgery with heart failure and after ventricular assist device (VAD) unloading (reduced hypoxia and volume overload). We show that HLHS cardiomyocytes, both within the heart and when derived from induced pluripotent stem cells, are intrinsically senescent. The HLHS myocardium contained a senescent microvascular niche with endothelial cells, pericytes and YAP-high fibroblasts, consistent with hypoxic and mechanical stress. This senescent niche is similar to adult myocardial infarction but not pediatric dilated cardiomyopathy with heart failure, pointing to a prominent role of hypoxia in senescence. The microvascular senescent niche was improved by VAD, providing insight into the potential to reverse cardiac cell states that lead to heart failure.