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UNLABELLED: We assessed the feasibility of dynamic 3-dimensional (3D) PET/CT tracking of (18)F-FDG-labeled circulating progenitor cell (CPC) therapy during intracoronary injection, using a porcine model of acute myocardial infarction (MI). METHODS: Human and porcine CPC were radiolabeled with (18)F-FDG, with variation in temperature and incubation time to determine optimal conditions. For in vivo experiments, CPC were harvested before induction of infarction (using 90-min coronary balloon occlusion). At 48 h, animals underwent cardiac MRI to assess infarct size. A balloon catheter was placed in the infarct artery at the same location as that used for induction of MI, and during dynamic 3D PET/CT 3 x 10(7) autologous (18)F-FDG progenitor cells were injected through the central lumen using either (a) 3 cycles of balloon occlusion and reperfusion or (b) high-concentration, single-bolus injection without balloon occlusion (n = 3 for both protocols). Peripheral blood was drawn at 1-min intervals during cell injection. RESULTS: Labeling efficiency was optimized by 30-min incubation at 37 degrees C (human CPC, 89.9% +/- 4.8%; porcine CPC, 91.6% +/- 6.4%). Cell-bound activity showed a nonsignificant decrease at 1 h (human, 74.3% +/- 10.7%; porcine, 77.7% +/- 12.8%; P > 0.05) and a significant decrease at 2 h (human, 62.1% +/- 8.9%; porcine, 68.6% +/- 5.4%; P = 0.009). Mean infarct size was similar for both injection protocols (16.3% +/- 3.4% and 20.6% +/- 2.7%; P > 0.05). Dynamic scanning demonstrated a sharp rise in myocardial activity during each cycle of balloon-occlusion cell delivery, with a significant fall in activity (around 80%) immediately after balloon deflation. The latter was associated with a transient spike in peripheral blood (18)F-FDG activity, consistent with the first pass of labeled cells in the systemic circulation. A single spike and gradual fall in myocardial activity was observed with high-concentration, single-bolus therapy. At 1 h, myocardial activity was 8.7% +/- 1.5% of total injected dose for balloon-occlusion delivery and 17.8% +/- 7.9% for high-concentration, single-bolus delivery (P = 0.08). CONCLUSION: Dynamic tracking during intracoronary injection of (18)F-FDG-labeled CPC is feasible and demonstrates significant cell washout from the myocardium immediately after balloon deflation. High-concentration, single-bolus therapy may be as effective as balloon-occlusion delivery. This tracking technique should facilitate development of improved delivery strategies for cardiac cell therapy.
Doyle et al. (Mon,) studied this question.