The purpose of this study was to determine the feasibility of a new positron emission tomography (PET) imaging approach using an 18F-labelled αvβ3 integrin antagonist (18F-Galacto-RGD) to monitor the integrin expression after myocardial infarction.
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.
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 αvβ3 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.
Regional 18F-Galacto-RGD accumulation suggests up-regulation of αvβ3 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.