Single-cell epigenomic and transcriptomic analysis unveils the pivotal role of GATA5/ISL1+ fibroblasts in cardiac repair post-myocardial infarction

A comprehensive understanding of the genome-wide regulatory landscape of the cardiac tissues post-myocardial infarction (MI) is still lacking. We therefore integrated single-cell RNA sequencing (scRNA-seq) and single-cell for transposase-accessible chromatin sequencing (scATAC-seq) to elucidate the epigenetic landscape of the heart post-MI. We established MI mice through ligation of the left anterior descending coronary artery, and obtained cardiac tissues from mice at 1,3,7 and 14-day post-MI. Integrative analyses of the scRNA-seq and scATAC-seq data revealed the presence of two novel fibroblast subpopulations in the MI cardiac tissues, termed GATA-binding protein 5/ISL LIM Homeobox 1 (GATA5/ISL1) + fibroblasts and GLI family zinc finger 3 (Gli3) high fibroblasts. The GATA5/ISL1+ fibroblasts were characterized by fibroblast and cardiomyocyte signatures and were found to play a crucial role in cardiac repair post-MI. Moreover, adenoviral-mediated overexpression of GATA5 and ISL1 ameliorated cardiac function and attenuated myocardial fibrosis in the MI mice. RNA sequencing confirmed that GATA5 and ISL1 co-regulate Wnt signaling pathway to promote the transformation of fibroblasts into functional cardiomyocytes. Furthermore, analysis of the human cardiac tissues of MI patients also revealed the presence of GATA5/ISL1+ fibroblasts in the scar tissues, suggesting their crucial role in cardiac tissue repair post-MI. In addition, proteomic analyses revealed enhanced cardiac repair and development signaling in the GATA5/ISL1-overexpressing human cardiac fibroblasts. The study provides novel perspectives on the mechanisms of myocardial injury and repair at the single-cell level and indicates the potential role of GATA5 and ISL1 as therapeutic targets for MI treatment.