Application of ⁶⁸Ga‐ and ¹⁷⁷Lu‐Labeled FAP Inhibitor in Evaluation and Treatment of Cardiac Fibrosis After Myocardial Infarction

Figures

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  FIGURE 1. Dynamic 68Ga‐FAPI‐04 PET/CT scanning. (A) Dynamic PET/CT images of rats at 7 days after MI (axial and coronal sections). Black and white circles at 10 min after tracer injection indicate regions of interest of infarcts and remote myocardium, respectively. H: heart; Li: liver. (B) 68Ga‐FAPI‐04 uptake in infarcted and remote non‐infarcted myocardium overtime (n = 3). (C) PET image‐based infarct‐to‐remote tracer uptake ratio over time (n = 3).

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  FIGURE 2. 68Ga‐FAPI‐04 PET/CT imaging at different time points. (A) Static axial PET/CT images of the same MI rat at 1, 3, 7, 14, and 28 days after coronary ligation. Black and white circles at 7 days after coronary ligation indicate regions of interest of infarcted and remote myocardium, respectively. Dashed lines represent demarcation between surgical wound and heart. (B) Tracer uptake in infarcted and remote myocardium at different time points (n = 3). (C) PET image‐based infarct‐to‐remote tracer uptake ratio over time (n = 3). (D) In vivo 68Ga‐FAPI‐04 PET/CT and corresponding ex vivo MRI images in another MI rat. Infarcted area illustrated in MRI image was consistent with the region of tracer accumulation in PET/CT.

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  FIGURE 3. Blocking experiments: (A) Axial PET/CT images from non‐blocked, blocked, and sham‐operated rats at 7 days after surgical operation. (B) Masson's and HE staining of parallel sections. Infarct areas in pathological sections are indicated by black arrows. (C) PET image‐based infarct‐to‐remote tracer uptake ratio (n = 5, *p < 0.05). (D) Quantitative analysis of fibrotic area based on Masson's staining (n = 5, ns = no significant difference).

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  FIGURE 4. Echocardiographic analysis. (A) Measurement of LVEF in vehicle controls (n = 7) and MI rats injected with 177Lu‐FAPI‐04 (n = 7 for 0.2 MBq/g group and n = 10 for 0.4 MBq/g group). LVEF in rats in the 0.4 MBq/g group exhibited an increasing trend 14 days post‐MI. (B) Timeline of following experiment for 177Lu‐FAPI, vehicle, and sham groups. (C) Representative echocardiography images of rats in the 177Lu‐FAPI group and vehicle group at 28 days after coronary ligation. (D) Echocardiographic analyses of LVEF, LVFS, LVEDV, and LVEDD at 7, 14, 21, and 28 days after MI (n = 11 for 177Lu‐FAPI group, n = 9 for vehicle group, and n = 9 for sham group). 177Lu‐FAPI‐04 was injected at 7 days post‐MI. There were no significant differences in cardiac function parameters among the three groups before coronary ligation, and no statistically significant difference in cardiac function parameters between the 177Lu‐FAPI and vehicle groups before 177Lu‐FAPI‐04 treatment. IF, Immunofluorescence; MRI, magnetic resonance imaging; LVEF, left ventricular ejection fraction; LVFS, left ventricular fractional shortening; LVEDV, left ventricular end‐diastolic volume; LVEDD, left ventricular end diastolic…

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  FIGURE 5. Assessment of the fibrotic area. (A) Representative Masson's staining of serial heart sections from apex to base at 28 days post‐MI. (B) Quantification of fibrotic area at 28 days after MI (n = 4 for vehicle group and n = 6 for 177Lu‐FAPI group). (C) Enumeration of infarct segments in MRI images (n = 5) (*p < 0.05).

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  FIGURE 6. Pathological analysis of cardiac tissue. (A) Representative IHC images of FAP at 7 days post‐MI. Insets 1 and 2 show higher magnifications of infarct and remote normal myocardium, respectively. (B) Quantification of FAP+ cell area in infarct zone and remote normal myocardium at 7 days post‐MI (n = 5). (C) IF staining of α‐SMA, periostin, and vimentin in 177Lu‐FAPI, vehicle, and sham groups at 7 days after 177Lu‐FAPI‐04 injection (14 days post‐MI). Protein levels of α‐SMA, periostin, and vimentin levels were quantified and presented as fold change compared with sham‐operated rats. Sham group: Sham‐operated rats treated with normal saline (n = 5). Vehicle group: MI rats treated with normal saline (n = 5). 177Lu‐FAPI group: MI rats treated with 177Lu‐FAPI‐04 (n = 5). (ns = no significant difference, *p < 0.05).

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  FIGURE 7. Detection of apoptotic proteins. (A–C) IF images of caspase‐3, Bax, and Bcl‐2 in different groups at 7 days post‐MI and corresponding quantitative analysis. (D) Apoptotic protein expression in 177Lu‐FAPI and vehicle groups over time. Sham group: Sham‐operated rats treated with normal saline (n = 5). Vehicle group: MI rats treated with normal saline (n = 12). 177Lu‐FAPI group: MI rats treated with 177Lu‐FAPI‐04 (n = 12) (*p < 0.05).

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  FIGURE 8. Radiopharmaceutical uptake and biochemical analysis. (A) 177Lu‐FAPI‐04 uptake at 3 and 24 h post‐drug injection (n = 3). (B–E) Biochemical analysis of 177Lu‐FAPI, vehicle, and sham groups (n = 3). ALB, albumin; ALT, alanine aminotransferase; BUN, blood urea nitrogen; CR, creatinine.