Comparing a timecourse of hESC-epicardium differentiation with single-cell adult and foetal human epicardium as part of the study: A single-cell comparison of adult and foetal human epicardium defines the age-associated changes in epicardial activity

This study is associated with the GEO accession GSE216019. Abstract from article: Re-activating quiescent adult epicardium represents a potential therapeutic approach for human cardiac regeneration. However, the exact molecular differences between inactive adult and active foetal epicardium are not known. Here, we combined foetal and adult human hearts for the first time using single-cell and single-nuclei RNA sequencing, and compared epicardial cells from both stages. We found a migratory fibroblast-like epicardial population only in the foetal heart and foetal epicardium expressed angiogenic gene programs, while the adult epicardium was solely mesothelial and immune-responsive. Furthermore, we predicted that adult hearts may still receive foetal epicardial paracrine communication, including WNT-signalling with endocardium, reinforcing the validity of regenerative strategies that administer or reactivate epicardial cells in situ. Finally, we explained graft efficacy of our human embryonic stem-cell derived epicardium model, by noting its similarity to human foetal epicardium. Overall, our study defines epicardial programs of regenerative angiogenesis absent in adult hearts, contextualises animal studies, and defines epicardial endpoints required for effective human heart regeneration. Overall design: Six time points were sampled from a 9-day hESC-epicardium differentiation for analysis of differentiation timecourse. Cells were collected on days 1, 2, 3, 4, 8, and 9 following the intermediate lateral mesoderm stage during the protocol by Iyer et al., (2015).