Imaging of αβ integrin expression in experimental myocardial ischemia with [Ga]NODAGA-RGD positron emission tomography.

BACKGROUND

Radiolabeled RGD peptides detect αβ integrin expression associated with angiogenesis and extracellular matrix remodeling after myocardial infarction. We studied whether cardiac positron emission tomography (PET) with [Ga]NODAGA-RGD detects increased αβ integrin expression after induction of flow-limiting coronary stenosis in pigs, and whether αβ integrin is expressed in viable ischemic or injured myocardium.

METHODS

We studied 8 Finnish landrace pigs 13 ± 4 days after percutaneous implantation of a bottleneck stent in the proximal left anterior descending coronary artery. Antithrombotic therapy was used to prevent stent occlusion. Myocardial uptake of [Ga]NODAGA-RGD (290 ± 31 MBq) was evaluated by a 62 min dynamic PET scan. The ischemic area was defined as the regional perfusion abnormality during adenosine-induced stress by [O]water PET. Guided by triphenyltetrazolium chloride staining, tissue samples from viable and injured myocardial areas were obtained for autoradiography and histology.

RESULTS

Stent implantation resulted in a partly reversible myocardial perfusion abnormality. Compared with remote myocardium, [Ga]NODAGA-RGD PET showed increased tracer uptake in the ischemic area (ischemic-to-remote ratio 1.3 ± 0.20, p = 0.0034). Tissue samples from the injured areas, but not from the viable ischemic areas, showed higher [Ga]NODAGA-RGD uptake than the remote non-ischemic myocardium. Uptake of [Ga]NODAGA-RGD correlated with immunohistochemical detection of αβ integrin that was expressed in the injured myocardial areas.

CONCLUSIONS

Cardiac [Ga]NODAGA-RGD PET demonstrates increased myocardial αβ integrin expression after induction of flow-limiting coronary stenosis in pigs. Localization of [Ga]NODAGA-RGD uptake indicates that it reflects αβ integrin expression associated with repair of recent myocardial injury.