DOI: 10.25345/c5222rk5q
title: MassIVE MSV000100259 - Cardiac proteomics to assess the role of Fibroblast Growth Factor Receptor 4 (FGFR4) in regulating myocardial energetics in preclinical model of Duchenne Muscular Dystrophy
title: Cardiomyopathy is the leading cause of mortality in patients with Duchenne Muscular dystrophy (DMD), highlighting the urgent need for targeted therapeutic intervention. Clinical findings show that fibrosis is an early sign of cardiac involvement in DMD occurring before ventricular dysfunction. We identified an increase of Fibroblast Growth Factor (FGF23) expression both systemically and locally in the heart, specifically by cardiac fibroblasts, of mdx mice. Normally, FGF23 is a bone-derived hormone that regulates mineral homeostasis. Elevated FGF23 levels are linked to cardiovascular complications in heart failure and renal disease, where it contributes to cardiac dysfunction through interactions with Fibroblast Growth Factor Receptor 4 (FGFR4) on cardiomyocytes. New insights from our studies shows a direct pathogenic role of FGF23 in dystrophin-deficient cardiomyopathy. However, the exact mechanism by which FGF23 induces pathological cardiac remodeling and dysfunction in DMD is not yet fully understood. Our preliminary data suggests, FGF23 deletion in the fibroblasts preserves left ventricular function and remodeling in mdx mice post-cardiac injury. Similarly, FGFR4 deletion from cardiomyocytes improves systolic function and contractility of the dystrophic heart. Our data highlights that the activation of FGFR4 mediated through cardiac fibroblast-derived FGF23 leads to cardiac dysfunction in DMD. However, it is still crucial to identify the mechanisms downstream of FGFR4 activation contributing to structural and functional cardiac remodeling in dystrophic hearts. It is known that both impaired myocardial energetics and fibroblast contribution to fibrosis precede overt cardiac dysfunction in DMD. RNA-sequencing with KEGG pathway enrichment analysis reveals that FGF23 acts as a pathological regulator of impaired energy metabolism pathways. FGF23 deletion from fibroblasts results in transcriptional reprogramming consistent with enhanced activation of the citric acid cycle and fatty acid catabolism, while simultaneously suppressing pro-apoptotic, profibrotic, and inflammatory pathways. These changes are associated with improved cardiac function. These data provide strong evidence that FGF23 exerts pathological control over energy metabolism pathways, likely mediated through its interaction with FGFR4 in dystrophic hearts. Here, we hypothesize that cardiomyocyte FGFR4 activation plays as a key pathological modulator that disrupts myocardial energy metabolism, leading to altered oxidative phosphorylation, fatty acid metabolism, and reduced ATP production, contributing to cardiac dysfunction in DMD. Therefore, the specific aim of the proposed study is to identify the FGFR4-driven mechanisms linking myocardial energetics and dystrophin-deficient cardiac dysfunction. We will perform global proteomics with mass spectrometry to characterize the changes in myocardial energetics in cardiomyocyte-specific deleted FGFR4 mice (mdx-FGFR4cKO) and wild-type littermate controls (mdx-FGFR4wt) in collaboration with IUSM Center for Proteome Analysis core. The proposed research is highly significant because it is expected to establish a strong mechanistic link between FGFR4 and myocardial energetics and potential for identifying new therapeutics targets for treating DMD. Hearts were collected from mdx-FGFR4cKO and littermate control mice under steady-state conditions and following ISO stress-induced remodeling. Hearts were washed in ice-cold PBS to flush out blood and remove circulating blood cells that could interfere with cardiac sample preparation. The hearts were then carefully excised, and flash-frozen in liquid nitrogen for proteomics analysis. Cryo-preserved samples were delivered to the Center for Proteome Analysis.