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

HLHS cardiomyocytes are intrinsically senescent, both within the heart and when derived from induced pluripotent stem cells.

• Senescence was identified in HLHS cardiomyocytes at the single-nucleus level using single-nucleus RNA sequencing (snRNA-seq).
• iPSC-derived cardiomyocytes from HLHS patients recapitulated the senescent phenotype, indicating intrinsic rather than purely environmental senescence.
• This finding was consistent across in vivo tissue and in vitro iPSC-derived models.

The HLHS right-ventricular myocardium contains a senescent microvascular niche composed of endothelial cells, pericytes, and YAP-high fibroblasts.

• The senescent microvascular niche was characterized by snRNA-seq and spatial transcriptomics profiling of the HLHS right-ventricular microenvironment.
• The niche included endothelial cells, pericytes, and a specific population of YAP-high fibroblasts.
• The composition was consistent with hypoxic and mechanical stress responses in these cell types.

The HLHS senescent microvascular niche is similar to adult myocardial infarction but distinct from pediatric dilated cardiomyopathy with heart failure.

• Comparative transcriptomic profiling showed shared senescence signatures between HLHS myocardium and adult myocardial infarction tissue.
• Pediatric dilated cardiomyopathy with heart failure did not show the same senescent niche profile.
• This distinction points to a prominent role of hypoxia, rather than heart failure per se, in driving the senescent niche in HLHS.

Ventricular assist device (VAD) unloading reversed the senescent microvascular niche in HLHS patients.

• The study profiled the HLHS right-ventricular microenvironment at three time points: at birth (before heart failure), after surgery with heart failure, and after VAD unloading.
• VAD unloading reduced hypoxia and volume overload in the HLHS myocardium.
• The microvascular senescent niche was improved following VAD treatment, suggesting reversibility of these cardiac cell states.

Single-nucleus RNA sequencing and spatial transcriptomics were used to profile the HLHS right-ventricular microenvironment across disease stages.

• Profiling was performed at birth (before heart failure), after palliative surgery with heart failure, and after VAD unloading.
• Both snRNA-seq and spatial transcriptomics were employed to characterize cell-type-specific and spatially resolved gene expression.
• The experimental design enabled longitudinal comparison of the right-ventricular microenvironment across clinical states.