Feeder-free generation and characterization of endocardial and cardiac valve cells from human pluripotent stem cells

Valvular heart disease presents a significant health burden, yet advancements in valve biology and ther-apeutics have been hindered by the lack of accessibility to human valve cells. In this study, we have devel-oped a scalable and feeder-free method to differentiate human induced pluripotent stem cells (iPSCs) into endocardial cells, which are transcriptionally and phenotypically distinct from vascular endothelial cells. These endocardial cells can be challenged to undergo endothelial-to-mesenchymal transition (EndMT), af-ter which two distinct populations emerge-one population undergoes EndMT to become valvular inter-stitial cells (VICs), while the other population reinforces their endothelial identity to become valvular endothelial cells (VECs). We then characterized these populations through bulk RNA-seq transcriptome analyses and compared our VIC and VEC populations to pseudobulk data generated from normal valve tissue of a 15-week-old human fetus. By increasing the accessibility to these cell populations, we aim to accelerate discoveries for cardiac valve biology and disease.