Yasuko Matsumura

Engineered heart tissues (EHTs) have been used in cardiovascular research for nearly three decades, addressing limitations of animal models and oversimplified two-dimensional single-cell systems in recapitulating cardiac (patho) physiology. Recently, epicardium-integrated EHTs have gained attention as therapeutic tools for remuscularizing the failing heart. The epicardium, the outermost mesothelial layer of the heart, plays a crucial role in cardiac development and disease by serving as a source of progenitor cells and by providing essential paracrine signalling. Hutchinson–Gilford progeria syndrome (HGPS) is a laminopathy caused by a point mutation in the LMNA gene, leading to expression of progerin and resulting in premature aging with a severe cardiovascular phenotype. We developed an epicardium-integrated EHT model to enable more physiologically relevant in vitro modelling of HGPS. Epicardial cells were incorporated into the EHTs and maintained in long-term culture. Cellular differentiation, progerin expression, transcriptomic changes, and functional responses to electrical pacing were assessed over time. Epicardial cells were observed to differentiate into cardiac fibroblasts and vascular smooth muscle cells, enabling incorporation of key non-myocyte populations relevant to HGPS pathology. The epicardium-integrated EHTs exhibited progerin expression and developed hallmarks of HGPS within 60 d of culture. Gene set enrichment analysis revealed upregulation of pathways associated with atherosclerosis, apoptosis, fibrosis, and oxidative stress, which are processes linked to both HGPS and physiological aging. Additionally, a culture time-dependent decline in the contractile response of EHTs to pacing was observed. In conclusion, our epicardium-integrated EHT model recapitulates key molecular, cellular, and functional features of HGPS-associated CVD. This platform provides a promising tool for investigating HGPS disease mechanisms and evaluating therapeutic strategies and may be adaptable for modelling other CVDs and regenerative applications.

Reactivating the human epicardium post-cardiac injury holds promise for cardiac tissue regeneration. Despite successful differentiation protocols yielding pure, self-renewing epicardial cells from induced pluripotent stem cells (iPSCs), these cells maintain an embryonic, proliferative state, impeding adult epicardial reactivation investigation. We introduce an optimized method that employs mammalian target of rapamycin (mTOR) signaling inhibition in embryonic epicardium, inducing a quiescent state that enhances multi-step epicardial maturation. This yields functionally mature epicardium, valuable for modeling adult epicardial reactivation. Furthermore, we assess cardiac organoids with cardiomyocytes and mature epicardium, probing molecular mechanisms governing epicardial quiescence during cardiac maturation. Our results highlight iPSC-derived mature epicardium’s potential in investigating adult epicardial reactivation, pivotal for effective cardiac regeneration. Additionally, the cardiac organoid model offers insight into intricate cardiomyocyte-epicardium interactions in cardiac development and regeneration.