TGFβ-Dependent Epithelial-Mesenchymal Plasticity in Immortalized Human Atrial Epicardial Cells: An mRNA Profiling...

The adult mammalian heart exhibits limited regenerative capacity. Although the epicardium contributes to cardiac injury responses and remodeling, expandable adult human in vitro models for investigating epicardial activation and epithelial-to-mesenchymal (EMT)-associated cellular responses remain limited. Here, we isolated human epicardium-derived cells from the adult heart auricle, expressing WT1⁺/MSLN⁺/CRIP1⁺ and generated an expandable immortalized epicardium-derived cell (iEPDC) population, allowing the investigation of intercellular dynamics upon EMT activation. TGFβ signaling was modulated using SB431542 or TGFβ3. Morphological, immunocytochemical, transcriptomic and functional analyses were performed to investigate treatment-dependent responses. SB431542-treated iEPDCs displayed epithelial-like characteristics and elevated WT1, MSLN and CRIP1 expression, with CRIP1 detected at both transcript and protein levels. TGFβ3-treated cells expressed the mesenchymal markers VIM and CD105 and exhibited spindle-shaped morphology, increased migratory behavior and upregulation of mesenchymal- and remodeling-associated markers. Transcriptomic analyses revealed distinct treatment-dependent profiles, enrichment of 'focal adhesion', 'ECM-receptor interaction' and cytoskeleton-associated pathways in TGFβ3-treated iEPDCs and intermediate transcriptional characteristics in untreated cells. Together, these findings establish adult iEPDCs as an expandable in vitro model for investigating TGFβ-dependent epicardial activation and EMT-associated processes in the adult human heart. Furthermore, the integration of phenotypic, transcriptomic and functional findings revealed the treatment-responsive plasticity of adult human iEPDCs, supporting future studies of injury-associated epicardial activation.