Abstract 2946: Multimodality Monitoring of Cardiac Cell Therapy by PET and MRI
Aim: We assessed the feasibility and usefulness of reporter gene imaging for PET and iron labeling for MRI to monitor transplanted cells.
Methods and results: Human endothelial progenitor cells (EPC) were transduced with both human sodium/iodide symporter (NIS) gene using a retroviral vector and labeled with superparamagnetic iron oxides. Nude rats received an intramyocardial injection of 4 million EPC (control:n =6, labeled:n = 10). MRI and I-124 PET were performed at day1 (n = 10), 3 (4) and 7 (7) after cell transplantation. The cell injection site was visualized as a signal void by MRI and a focal I-124 accumulation by PET at day1. The normalized signal contrast (contrast-to-noise ratio; CNR) (0.8 ± 0.2 vs -0.3 ± 0.1, p<0.001) and percentage of tracer injected dose by PET (4.1 ± 1.0 vs -0.2 ± 0.4, p<0.001) were significantly higher in labeled than in non-labeled EPC. CNR remained unchanged at day3 (3.9+/-0.6) and day7 (4.4 ± 1.3). In contrast, I-124 uptake disappeared at 3d (0.42 ± 0.05) and day7 (0.33 ± 0.06). Postmortem histochemical analysis confirmed the presence of transplanted EPC at day1, but the absence of viable EPC and localization of iron particles in macrophages at day7.
Conclusions: Multimodality imaging using magnetic and genetic cell labeling allows for the simultaneous assessment of cell localization and viability early after transplantation. MRI signal looses specificity for viable transplanted cells as early as 7 days after injection most likely due to phagocytosis. Monitoring of cell viability by symporter gene techniques may be important to quantitatively assess the survival of the donor cells after transplantation.