Assessment of α_vβ₃ integrin expression after myocardial infarction by positron emission tomography

Aims: The purpose of this study was to determine the feasibility of a new positron emission tomography (PET) imaging approach using an ¹⁸F-labelled α_vβ₃ integrin antagonist (¹⁸F-Galacto-RGD) to monitor the integrin expression after myocardial infarction. Methods and results: Male Wister rats were subjected to 20 min transient left coronary artery occlusion followed by reperfusion. Autoradiographic analysis and in vivo PET imaging were used to determine myocardial ¹⁸F-Galacto-RGD uptake at different time points following reperfusion. Results: PET imaging and autoradiography demonstrated no significant focal myocardial ¹⁸F-Galacto-RGD uptake in non-operated control rats and at day 1 after reperfusion. However, focal accumulation in the infarct area started at day 3 (uptake ratio = 1.91 ± 0.22 vs. remote myocardium), peaked between 1 (3.43 ± 0.57) and 3 weeks (3.43 ± 0.95), and decreased to 1.96 ± 0.40 at 6 months after reperfusion. Pretreatment with α_vβ₃ integrin antagonist c(-RGDfV-) significantly decreased tracer uptake, indicating the specificity of tracer uptake. The time course of focal tracer uptake paralleled vascular density as measured by CD31 immunohistochemical analysis. Conclusion: Regional ¹⁸F-Galacto-RGD accumulation suggests up-regulation of α_vβ₃ integrin expression after myocardial infarction, which peaks between 1 and 3 weeks and remains detectable until 6 months after reperfusion. This new PET tracer is promising for the monitoring of myocardial repair processes.