Longitude characterization of immune-fibroblast axis following myocardial infarction via molecular imaging integrated with proteomics in minipigs.

Abstract

Targeting dynamic inflammatory-fibrotic pathways post-myocardial infarction (MI) is essential for exploring novel biomarkers to improve healing and attenuate adverse left ventricular (LV) remodeling. This study aimed to investigate the spatiotemporal dynamic pattern of immune inflammation and fibroblast activation and to map the proteomic profile of different regions over time after acute MI (AMI). In 14 minipigs model of AMI, serial ^99mTc-MIBI SPECT/CT myocardial perfusion imaging, Al¹⁸F-NOTA-FAPI-04 and ¹⁸F-FDG PET/CT imaging were performed at key time points - 7 days (acute phase), 14 days (subacute phase), and 3 months (chronic phase) post-AMI. The regional uptake of Al¹⁸F-NOTA-FAPI-04 and ¹⁸F-FDG was quantitatively assessed to evaluate the spatio-temporal dynamics of immune inflammation and fibroblast activation. Correlations between tracer uptake and cardiac outcomes were analyzed, and ex vivo histological validation was performed. Proteomic profiling of myocardial tissues from the infarct, border, and remote areas were conducted at all timepoints. Al¹⁸F-NOTA-FAPI-04⁺ (¹⁸F-FAPI⁺) and ¹⁸F-FDG⁺ areas overlaid in the infarct and border myocardium at 7 days after AMI. The uptake activity of ¹⁸F-FAPI⁺ (SUV_max 4.97 ± 1.63, 4.45 ± 1.54 and 1.12 ± 0.25) and ¹⁸F-FDG⁺ (SUV_max 4.37 ± 1.81, 3.63 ± 2.32 and 0.94 ± 0.19) areas in LV was gradually declined over time (P < 0.001; P = 0.008). Total lesion FAPI uptake (TLF) and total lesion glycolysis exhibited significantly positive correlations (r = 0.723, P < 0.001). The infarct area was correlated with TLF (r = 0.462, P = 0.012) and the border area was correlated with ¹⁸F-FDG⁺ area (r = 0.466, P = 0.016). Early Al¹⁸F-NOTA-FAPI-04 uptake was correlated with subsequent LV remodeling (r = 0.909, P = 0.032). Proteomic analysis identified distinct temporal and regional protein expression changes, highlighting early activation of immune response pathways and mitochondrial dysfunction in the infarct and border myocardium. Over time, fibroblast activity persisted in the infarct zone, while the border and remote areas exhibited adaptive metabolic shifts. This study revealed the spatio-temporal dynamic pattern of immune inflammation and fibroblast activation during the healing process following AMI. It provides a theoretical basis for future directions of molecular inflammatory combined fibroblast imaging-guided therapy post-MI.