Reduction of Cardiac Fibrosis by Interference With YAP-Dependent Transactivation

Conversion of cardiospheres derived primitive cardiac stromal cells into myofibroblasts is typically associated with hypoxia conditions, metabolic insults, and/or inflammation, all of which are predisposing factors to cardiac fibrosis and heart failure. We hypothesized that this conversion could be also mediated by response of these cells to mechanical cues through activation of the Hippo transcriptional pathway. The objective of the present study was to assess the role of cellular/nuclear straining forces acting in myofibroblast differentiation of cardiospheres derived primitive cardiac stromal cells under the control of YAP transcription factor and to validate this finding using a pharmacological agent that interferes with the interactions of the YAP/TAZ complex with their cognate transcription factors TEADs, under high-strain and pro-fibrotic stimulation. We employed high content imaging, 2D/3D culture, atomic force microscopy mapping and molecular methods to prove the role of cell/nuclear straining in YAP-dependent fibrotic programming in a mouse model of ischemia-dependent cardiac fibrosis and in human-derived primitive cardiospheres derived primitive cardiac stromal cells . We also tested treatment of cells with Verteporfin, a drug known to prevent the association of the YAP/TAZ complex with their cognate transcription factors TEADs. Results suggested that pharmacologically targeting the YAP-dependent pathway overrides the pro-fibrotic activation of cardiospheres derived primitive cardiac stromal cells by mechanical cues in vitro, and that this occurs even in the presence of pro-fibrotic signaling mediated by TGF-β1. In vivo administration of Verteporfin in mice with permanent cardiac ischemia reduced significantly fibrosis and morphometric remodeling but did not improve cardiac performance. Our study indicates that preventing molecular translation of mechanical cues in cardiospheres derived primitive cardiac stromal cells reduces the impact of cardiac maladaptive remodeling with a positive effect on fibrosis. A total of 24 samples has been analyzed from 6 independent cultured cSt-Cs stimulated or not with TGF beta, verterporfin or a combination of the two. Samples were analysed for differentially expressed genes according to a paired-sample design between treated and untreated (control) cSt-Cs.