Cardiac fibroblasts cellular anisotropy is determined by YAP-dependent cellular contractility and ECM production

Cardiac fibroblasts (CFbs) determine the topological arrangement and the anisotropy of the heart tissue, features which are essential for maintaining tissue integrity and function, primarily through the production and remodeling of the extracellular matrix (ECM). Under pathological conditions, CFbs can activate into myofibroblasts, which promote maladaptive ECM remodeling, a process which may lead to heart failure. Although the mechanosensitive Yes-Associated Protein (YAP) has been implicated in CFb activation, its role in the organization of CFbs and in their ability to deposit cardiac ECM remains unexplored. We investigated the effects of YAP genetic deletion on cardiac fibroblast phenotype and function by generating CFbs from wild-type (WT) and YAP knockout (KO) human embryonic stem cells (hESCs). We found that YAP depletion impaired CFbs differentiation by reducing the expression of cardiogenic markers. Additionally, we demonstrated that YAP expression is required for monolayer alignment of CFbs. Transcriptomic analysis further revealed that YAP is essential for the regulation of ECM- and contractility-related genes, and that its absence resulted in reduced ECM deposition, diminished anisotropy, and decreased force generation. Pharmacological inhibition of contractility closely mirrored YAP KO phenotype, suggesting that YAP regulates both monolayer organization and ECM structure through its control over contractility. These findings underscore the critical role of the mechanosensor YAP in maintaining the supracellular organization of CFbs and the mechanical integrity of cardiac tissue.