13 | Generation of human stem cell-derived cardiac in vitro models to investigate the role of epicardial activation in adverse cardiac remodeling

Margalida Campaner Socias¹, V. Marini¹, L. Rinvenuto¹, A. Wang¹, J. Zhang¹, S. Morri¹, D. Stalkopf¹, R. Oida¹, B. Sampaio¹, M. Sampaolesi^1|2 | ¹Laboratory of Translational Cardiomyology, Stem Cell and Developmental Biology Unit, Department of Development and Regeneration, KU Leuven, Leuven, Belgium; ²Histology and Medical Embryology Unit, Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Sapienza University of Rome, Rome, Italy.

Cardiovascular diseases (CVDs) are the leading cause of mortality and morbidity worldwide. CVD progression, regardless of etiology, is often driven by adverse cardiac remodeling (ACR) events, whereby injured cardiomyocytes (CMs) are replaced with scar tissue, significantly impacting organ function and eventually leading to heart failure. The epicardium surrounds the myocardium in all vertebrate species and in zebrafish, epicardial cell (EpiC) activation drives heart regeneration after injury. While a similar process occurs in mammals, its mechanisms and link to cardiac remodeling remain poorly understood, especially in humans. This study explores the early phases of developing a 3D human induced pluripotent stem cell (hiPSC)-derived epicardial-myocardial in vitro system as a tool to investigate human epicardial activation in different injury settings. Through the infliction of a transient ischemiclike injury and the use of muscular dystrophy patient-derived hiPSCs, we have established models for acute and chronic cardiac injuries, capable of partially mimicking hallmark traits of ACR. In parallel, we optimized a differentiation protocol to obtain hiPSC-derived EpiCs. Interestingly, we identified a dysregulated gene expression profile in dystrophic EpiCs when compared to their isogenic controls, suggesting that disruptions in the DMD gene can also affect epicardial biology and its activation. Current experiments are focusing on the generation of hiPSC-derived cardiac fibroblasts (CFs) and the establishment of CM-CF coculture spheroids to obtain a more robust and biologically relevant fibrotic response. In the future, we will include the epicardial layer within myocardial injury models to explore the role of the activated epicardium in ACR events in these systems. This increasingly complex model will have the potential to enhance our understanding of human cardiac repair mechanisms for the development of effective tools to combat heart failure progression.