PET imaging of angiogenesis after myocardial infarction/reperfusion using a one-step labeled integrin-targeted tracer 18F-AlF-NOTA-PRGD2

Abstract

The α(v)β(3) integrin represents a potential target for noninvasive imaging of angiogenesis. The purpose of this study was to evaluate a novel one-step labeled integrin α(v)β(3)-targeting positron emission tomography (PET) probe, (18)F-AlF-NOTA-PRGD2, for angiogenesis imaging in a myocardial infarction/reperfusion (MI/R) animal model. Male Sprague-Dawley rats underwent 45-min transient left coronary artery occlusion followed by reperfusion. The myocardial infarction was confirmed by ECG, (18)F-fluorodeoxyglucose (FDG) imaging, and cardiac ultrasound. In vivo PET imaging was used to determine myocardial uptake of (18)F-AlF-NOTA-PRGD2 at different time points following reperfusion. The control peptide RAD was labeled with a similar procedure and used to confirm the specificity. Ex vivo autoradiographic analysis and CD31/CD61 double immunofluorescence staining were performed to validate the PET results. Myocardial origin of the (18)F-AlF-NOTA-PRGD2 accumulation was confirmed by (18)F-FDG and autoradiography. PET imaging demonstrated increased focal accumulation of (18)F-AlF-NOTA-PRGD2 in the infarcted area which started at day 3 (0.28 ± 0.03%ID/g, p < 0.05) and peaked between 1 and 3 weeks (0.59 ± 0.16 and 0.55 ± 0.13%ID/g, respectively). The focal accumulation decreased but still kept at a higher level than the sham group after 4 months of reperfusion (0.31 ± 0.01%ID/g, p < 0.05). Pretreatment with unlabeled arginine-glycine-aspartic acid (RGD) peptide significantly decreased tracer uptake, indicating integrin specificity of this tracer. At 1 week after MI/R, uptake of the control tracer (18)F-AlF-NOTA-RAD that does not bind to integrin, in the infarcted area, was only 0.21 ± 0.01%ID/g. Autoradiographic imaging showed the same trend of uptake in the myocardial infarction area. The time course of focal tracer uptake was consistent with the pattern of vascular density and integrin β(3) expression as measured by CD31 and CD61 immunostaining analysis. PET imaging using one-step labeled (18)F-AlF-NOTA-PRGD2 allows noninvasive visualization of ischemia/reperfusion-induced myocardial angiogenesis longitudinally. The favorable in vivo kinetics and easy production method of this integrin-targeted PET tracer facilitates its future clinical translation for lesion evaluation and therapy response monitoring in patients with occlusive cardiovascular diseases.