Impact of Hybrid Stage 1 Palliation for Hypoplastic Left Heart Syndrome: Histopathological Findings

Single-Cell RNA Sequencing and Quantitative Proteomics Analysis Elucidate Marker Genes and Molecular Mechanisms in Hypoplastic Left Heart Patients With Heart Failure

Objective

To probe markers and molecular mechanisms of the hypoplastic left heart (HLH) by single-cell RNA sequencing (scRNA-seq) and quantitative proteomics analysis.

Methods

Following data preprocessing, scRNA-seq data of pluripotent stem cell (iPSC)-derived cardiomyocytes from one HLH patient and one control were analyzed by the Seurat package in R. Cell clusters were characterized, which was followed by a pseudotime analysis. Markers in the pseudotime analysis were utilized for functional enrichment analysis. Quantitative proteomics analysis was based on peripheral blood samples from HLH patients without heart failure (HLH-NHF), HLH patients with heart failure (HLH-HF), and healthy controls. Hub genes were identified by the intersection of pseudotime markers and differentially expressed proteins (DE-proteins), which were validated in the GSE77798 dataset, RT-qPCR, and western blot.

Results

Cardiomyocytes derived from iPSCs were clustered into mesenchymal stem cells, myocardium, and fibroblast cells. Pseudotime analysis revealed their differentiation trajectory. Markers in the three pseudotime clusters were significantly associated with distinct biological processes and pathways. Finally, three hub genes (MMP2, B2M, and COL5A1) were identified, which were highly expressed in the left (LV) and right (RV) ventricles of HLH patients compared with controls. Furthermore, higher expression levels were detected in HLH patients with or without HF than in controls.

Conclusion

Our findings elucidate marker genes and molecular mechanisms of HLH, deepening the understanding of the pathogenesis of HLH.

Coronary Arterial Abnormalities in Hypoplastic Left Heart Syndrome: Pathologic Characteristics of Archived Specimens

Palliation of patients with hypoplastic left heart syndrome remains challenging. Although coronary ischemia can be catastrophic, the prevalence and pathologies of anomalies of the coronary arteries remains unknown. We reviewed 119 specimens with the features of hypoplastic left heart syndrome, focusing our attention on the aortic root and the coronary arteries. We found 36 (30%) specimens with the combination of mitral and aortic atresia, 26 (22%) with mitral and aortic stenosis, and 57 (48%) with mitral stenosis combined with aortic atresia. In 29 specimens (24%), the coronary arteries were not located in the center of any sinuses, while in 24 specimens (21%) at least 1 coronary artery was located very proximal to a raphe or commissure, with potential for obstruction. The specimens with combined stenosis were more likely to have eccentric positions of the coronary arteries (11 specimens, 42%), compared to the 3 specimens with combined atresia (9%, P = 0.009). The specimens with combined stenosis were also more likely to have positioning at risk for obstruction (9 specimens, 35%), compared to those with combined atresia (3 specimens, 9%, P = 0.05). Coronary arterial fistulous communications were found in 11 specimens (9%), significantly more frequently in specimens with mitral stenosis and aortic atresia (9 specimens, 16%, P = 0.041). The origins of the coronary arteries in patients with hypoplastic left heart syndrome place them at potential risk for ischemia, with fistulous communications being a particular risk in those with mitral stenosis combined with aortic atresia.