Epicardial-derived cells secrete extracellular vesicles that modulate gene expression in the cardiac response to ischemia-reperfusion injury [BW mRNAseq]

The epicardium is an essential regulator of cardiac development, homeostasis, and injury. While advanced 3D human cardiac tissue models now facilitate physiologically relevant exploration of epicardial–myocardial interactions, the composition and impacts of epicardial cell-secreted extracellular vesicles (EVs) in regulating cardiac physiology remain incompletely understood. Here we harnessed an “Epicardial Biowire” platform integrating human epicardial cells with functional myocardium, applying transcriptomics to reveal enriched vesicle transport in engineered tissues containing epicardial cells. Profiling epicardial-EVs identified key miRNAs in their cargo and indicated considerable conservation of miRNA cargo through stimulated epithelial‐to‐mesenchymal transition. Supplementation of epicardial-EVs to engineered tissues undergoing simulated ischemia–reperfusion injury (IRI) influenced gene expression associated with reduction of extracellular matrix remodeling, fibroblast modulation, and suppression of cell-ECM interactions. Correlation of EV‐miRNAs with mRNA targets highlighted implications of miR‐30d‐5p, miR‐9‐5p, miR‐16‐5p, and the let‐7 family, supporting a potential role for epicardial-EVs and their miRNA cargo in moderating deleterious fibrotic activation and matrix remodelling during myocardial injury in vitro. Collectively, these findings expand our understanding of epicardial-EV composition and function, highlighting epicardial signalling as a promising avenue to direct cardiac repair and inspiring the design of future EV‐based therapeutics.