Positron Emission Tomography Imaging of Poststroke Angiogenesis

Background and Purpose-Vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) play important roles during neurovascular repair after stroke. In this study, we imaged VEGFR expression with positron emission tomography (PET) to noninvasively analyze poststroke angiogenesis. Methods-Female Sprague-Dawley rats after distal middle cerebral artery occlusion surgery were subjected to weekly MRI, F-18-FDG PET, and Cu-64-DOTA-VEGF(121) PET scans. Several control experiments were performed to confirm the VEGFR specificity of Cu-64-DOTA-VEGF(121) uptake in the stroke border zone. VEGFR, BrdU, lectin staining, and I-125-VEGF(165) autoradiography on stroke brain tissue slices were performed to validate the in vivo findings. Results-T2-weighed MRI correlated with the "cold spot" on F-18-FDG PET for rats undergoing distal middle cerebral artery occlusion surgery. The Cu-64-DOTA-VEGF(121) uptake in the stroke border zone peaked at approximate to 10 days after surgery, indicating neovascularization as confirmed by histology (VEGFR-2, BrdU, and lectin staining). VEGFR specificity of Cu-64-DOTA-VEGF(121) uptake was confirmed by significantly lower uptake of 64Cu-DOTA-VEGF(mutant) in vivo and intense I-125-VEGF(165) uptake ex vivo in the stroke border zone. No appreciable uptake of Cu-64-DOTA-VEGF(121) was observed in the brain of sham-operated rats. Conclusions-For the first time to our knowledge, we successfully evaluated the VEGFR expression kinetics noninvasively in a rat stroke model. In vivo imaging of VEGFR expression could become a significant clinical tool to plan and monitor therapies aimed at improving poststroke angiogenesis. (Stroke. 2009; 40: 270-277.)