Rationale: Cardiac extracellular matrix (ECM) comprises a dynamic molecular network providing structural support to heart tissue function. Understanding the impact of ECM remodeling on cardiac cells during heart failure (HF) is essential to prevent adverse ventricular remodeling and restore organ functionality in affected patients. Objective: We aimed to (i) identify consistent modifications to cardiac ECM structure and mechanics that contribute to HF and (ii) determine the underlying molecular mechanisms. Methods and Results: We first performed decellularization of human and murine ECM (dECM) and then analyzed the pathological changes occurring in dECM during HF by atomic force (AFM), two-photon microscopy, high-resolution 3D image analysis and computational fluid dynamics (CFD) simulation. We then performed molecular and functional assays in patient-derived cardiac fibroblasts (CFs) based on YAP-TEAD mechanosensing activity and collagen contraction assays. The analysis of HF dECM resulting from ischemic (IHD) or dilated cardiomyopathy (DCM), as well as from mouse infarcted tissue, identified a common pattern of modifications in their 3D topography. As compared to healthy heart, HF ECM exhibited aligned, flat and compact fiber bundles, with reduced elasticity and organizational complexity. At the molecular level, RNA sequencing of HF CFs highlighted the overrepresentation of dysregulated genes involved in ECM organization, or being connected to TGFß1, Interleukin-1, TNF-alpha and BDNF signaling pathways. Functional tests performed on HF CFs pointed at mechanosensor YAP as a key player in ECM remodeling in the diseased heart via transcriptional activation of focal adhesion assembly. Finally, in vitro experiments clarified pathological cardiac ECM prevents cell homing, thus providing further hints to identify a possible window of action for cell therapy in cardiac diseases. Conclusions: Our multi-parametric approach has highlighted repercussions of ECM remodeling on cell homing, CF activation and focal adhesion protein expression via hyper-activated YAP signaling during HF.

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