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Targetting folate receptor-β expressing macrophages by 18F-labelled folate PET radiotracer in rat model of myocardial infarction

List of AuthorsIqbal I, Liljenbäck H, Andriana P, Ståhle M, Virta J, Herre EA, Miner MWG, Srinivasarao M, Low PS, Knuuti J, Li XG, Roivainen A, Saraste A

Conference nameAnnual Congress of the European association of nuclear Medicine

Publication year2022

JournalEuropean Journal of Nuclear Medicine and Molecular Imaging

Book title *EANM'22

Number in series(suppl 1)

Volume number49





Aim/Introduction: After myocardial infarction (MI), local inflammatory response contributes to the repair of myocardial injury. Folate receptor-β (FR-β) is expressed on the activated macrophages at the site of inflammation. In this study, we evaluated whether FR- β-targeting positron emission tomography (PET) tracer aluminum 18F-labeled NOTA-folate (18F-FOL) can be used for the detection of inflammation after MI. 
Materials and Methods: We studied male Sprague-Dawley rats, 3 days and 7 days after permanent occlusion of the left coronary artery (LCA) (n = 5 and n = 4, respectively) or after sham-operation (n = 5 and n = 5, respectively). The rats were PET imaged with glucose-analog 18F-FDG for anatomical reference 24 hours before the PET imaging with 50 ± 5 MBq of 18F-FOL. Left ventricle (LV) was frozen and cut into short-axis cryosections for digital autoradiography and histology. The sections were stained with H&E for general histology and CD68 antibody for macrophages. 
Results: Histology confirmed the presence of MI in 5 rats at 3 days and 4 rats at 7 days after LCA occlusion. Time-activity curves showed rapid clearance of 18F-FOL from the blood pool and stable uptake in the myocardium 20 minutes post-injection. PET images showed high focal 18F-FOL uptake co-localizing with the infarcted myocardium in all rats with MI, whereas there was no uptake in non-infarcted myocardium or myocardium of sham-operated rats. Compared to sham-operated rats, the average 18F-FOL uptake was three folds higher in the infarcted area (p = 0.01) on day 3 and two folds higher on day 7 (p = 0.03) after MI. Ex-vivo autoradiography confirmed increased 18F-FOL uptake co-localizing with the CD68- positive macrophages in the infarcted area. 
Conclusion: 18F-FOL PET shows increased uptake in the infarcted myocardium in a rat model of MI. These results suggest that FR-β targeting18F-FOL PET is useful for the detection of activated macrophages after MI and may be useful for monitoring inflammatory activity in the heart after myocardial injury.

Last updated on 2023-14-03 at 10:49