Abstract 238: Single-Cell Transcriptomic Analysis and Patient-Specific IPSCs Reveal Dysregulated Cell Cycle in Coronary Endothelial Cell in Hypoplastic Left Heart Syndrome

Abstract

Hypoplastic left heart syndrome (HLHS) is a single ventricle congenital heart disease that results in severe underdevelopment of the left ventricle, mitral valve, aortic valve, and ascending aorta. Early serial postmortem examinations also revealed a high rate of coronary anomalies in HLHS, which included multiple ventriculo-coronary arterial connections as well as thick-walled and kinked coronary arteries. A previous study showed that fetal hypoplastic left hearts had a reduced endothelial cell (EC) population and lower capillary density compared with normal hearts. However, the mechanism underlying coronary abnormalities associated with HLHS remains unknown. Thus, we generated induced pluripotent stem cells derived ECs (iPSC-ECs) from three HLHS patients and three age-matched controls. Single Cell RNA-Seq (scRNA-seq) profiling identified both endocardial (NPR3 + /CDH5 + ) and coronary endothelial populations (APLN + /CDH5 + ) from the heterogeneous iPSC-ECs. Intriguingly, a subcluster of the coronary endothelial cells (CECs) with cell cycle arrest was specifically enriched in HLHS patients. Further cell cycle analysis showed that 30.6% of the HLHS cells were trapped in the G1 phase, while the majority of the control CECs entered cell cycle normally. Additionally, the cell cycle differences between control and HLHS was only seen in CECs, not in the endocardial population. To verify our transcriptomic analysis, we applied negative cell sorting (NPR3 - /CDH5 + ) on iPSC-ECs to purify CECs (iCECs) and confirmed that HLHS iCECs showed profound reduction of cell cycle/proliferative genes ( KI67, PCNA, CCNA2, CCNB1 ) and abnormal induction of CCND2 , which is the hallmark of G1 phase. BrdU assays also indicated suppressed proliferation in HLHS iCECs. Furthermore, we profiled the transcriptome from a human heart with an underdevelopment left ventricle (ULV) at single cell resolution. When compared to the normal human heart, pathway enrichment analysis of differentially expressed genes in ULV hearts demonstrated reduced cell proliferation in the CEC subpopulation. Here, we identified that CECs from HLHS patients exerted proliferative defects that can potentially impede the development of vascular/capillary structure and cause related functional deficiencies. Reformation of the coronary defect provides a promising therapeutic strategy to prevent HLHS deterioration.