Modeling the congenital heart condition of pulmonary atresia with intact ventricular septum using human induced pluripotent stem cells

Abstract

Congenital heart disease (CHD) is the most common birth defect, affecting about 1% of live births. Pulmonary atresia with intact ventricular septum (PAIVS) is a cyanotic congenital cardiac malformation characterized by an atretic pulmonary outflow and varying degrees of tricuspid valvar and right ventricular hypoplasia. Its genetic basis is ill-defined. Furthermore, despite surgical and/or catheter interventions, right ventricular dysfunction remains an important long-term concern. To gain novel insights of this malformation, blood samples from 4 PAIVS patients and 2 healthy subjects were collected and episomally reprogrammed into human induced pluripotent stem cells (hiPSCs), followed by systematic characterization of single-cell transcriptomes and functional assessment of the patient and control-specific hiPSCs, their derived ventricular cardiomyocytes (vCMs), as well as 2D and 3D engineered cardiac constructs. Comparison of the single-cell transcriptomes of hiPSCs of patients with those of healthy subjects showed the TGF beta signaling pathway as the top under-represented pathway, with the left/right asymmetry genes LEFTY1, LEFTY2 and NODAL being significantly downregulated, suggesting their involvement in the development of the disease. Single-cell transcriptomic analysis of hiPSC-vCMs showed the cardiac muscle contraction pathway as the top under-represented pathway, with significant downregulation of key contractile proteins including MYL2, TPM2. This finding corroborates with results from functional assays showing a decrease in developed forces in human ventricular cardiac tissue strips (hvCTS) fabricated from the PAIVS hiPSC-vCMs when compared to their normal counterparts. Characterization of the action potential profile of human ventricular cardiac anisotropic sheets (hvCAS) fabricated from PAIVS hiPSC-vCMs revealed no significant difference from control. Taken together, our findings provide new evidence that cardiomyocytes in PAIVS patients have intrinsic defects in their contractile function independent of secondary anatomical alterations. Further systematic analyses would enable us to understand this congenital cardiac malformation from the developmental and functional perspectives and identify bona fide underlying basis of the condition.