Angiogenesis is a key factor for post-ischemic repair of the infarcted myocardium. This study aims to monitor angiogenesis of infarcted myocardium with a positron emission tomography (PET) imaging agent, (18)F-alfatide II ((18)F-AlF-NOTA-E[PEG4-c(RGDfk)]2), targeting αvβ3 integrin after treatment with vascular endothelial growth factor (VEGF) gene and/or bone marrow mesenchymal stem cells (BMSCs). Sprague-Dawley (SD) rats underwent left coronary artery ligation and were randomly divided into four groups: normal saline control, Ad-VEGF, BMSCs, and Ad-VEGF + BMSCs (n = 4/group). The induced myocardial infarction (MI) was confirmed by electrocardiogram (ECG) with ST-segment elevation, and (99m)Tc-MIBI SPECT imaging showing defected myocardial perfusion. Alfatide II PET was performed to monitor angiogenesis at different time points after the therapy. The ratios of Alfatide II tracer uptake in the infarcted myocardium to normal myocardium in all four groups were analyzed. The PET results were validated by ex vivo tissue biodistribution, autoradiography, and immunofluorescence staining. At 1 week after therapy, elevated RGD peptide tracer uptake at the infarcted myocardium was observed in all four groups. The infarct to normal heart ratio of Alfatide II tracer for the three treatment groups was significantly higher than that of the control group (3.94 ± 0.20 for VEGF group, 3.77 ± 0.16 for BMSCs group and 4.86 ± 0.08 for the combination group vs. 3.01 ± 0.03 for the control group, P < 0.005, P < 0.005, P < 0.0001, respectively). The combination treatment group demonstrated higher contrast than the two single treatment groups. Similar results were also observed at 4 weeks after treatment. Autoradiography showed similar trend to that of PET results. Immunohistochemical staining showed expression of VEGF protein and the presence of adenovirus in the myocardium. The patterns of vascular density and integrin αvβ3 expression were measured by CD31 and CD61 immunostaining analysis, and were consistent with the PET results. (18)F-alfatide II PET could reflect angiogenesis of infarcted myocardium after VEGF gene and BMSCs therapy and further provide a non-invasive way of monitoring therapy response of myocardial infarction.
Keywords: Angiogenesis; Integrin αvβ3; Mesenchymal stem cell; Myocardial infarction; Myocardial perfusion imaging; PET; VEGF.