EDA-fibronectin defines an early molecular target for imaging cardiac remodeling

Fibrotic remodeling is a primary driver of heart failure, yet early molecular events remain difficult to detect non-invasively. Cellular fibronectin (cFN), an alternatively spliced fibronectin isoform containing the extra domain A (EDA), is rapidly induced during early tissue repair and precedes collagen deposition. This study identifies the molecular target responsible for myocardial uptake of 18 F-fluoroglucaric acid (FGA) and determines whether this tracer can report early extracellular matrix remodeling associated with cardiac injury. We employed an integrated approach combining quantitative SILAC-based proteomics, microscale thermophoresis (MST), and competitive binding assays. Using a biotinylated surrogate (BGA), tracer kinetics and target specificity were evaluated in human AC16 cardiomyocytes under ischemic and profibrotic stress. In vivo validation was performed using PET/CT imaging and biodistribution studies in murine models of cardiac injury, including isoproterenol-induced cardiomyopathy and autoimmune myocarditis. Proteomic profiling identified fibronectin as the primary interacting partner of surrogate BGA. MST revealed that FGA binds cFN with submicromolar affinity (Kd ≈ 0.42 µM), while showing substantially weaker, micromolar-range binding to plasma fibronectin (Kd ≈ 7.6 µM). In vivo, 18 F-FGA uptake was significantly elevated in damaged myocardium and strongly correlated with EDA-FN expression (r 2 = 0.92; Pearson r = 0.958, 95% CI 0.661–0.996; p = 0.0026, n = 6). Temporal analyses in cellular and tissue models indicated that cFN induction and BGA accumulation occur early in fibrogenesis, preceding significant collagen deposition. 18 F-FGA preferentially and EDA-dependently associates with cFN, a marker of early extracellular matrix activation, supporting its potential as a candidate PET probe for early cardiac remodeling. Direct characterization of the binding interface and longitudinal in vivo studies will be required to confirm detection of a pre-fibrotic state.