Abstract 2672: Serial in vivo Non-invasive Imaging of Intramyocardially Injected Autologous Mesenchymal Stem Cells, Modified for Transgene Expression of Positron-Emission Tomography (PET) Reporter in Porcine Myocardial Infarction
Objective. The aim of our study was to elaborate an in vivo tracking method of the intramyocardially injected msenchymal stem cells (MSCs), modified for transgene expression of trifusion protein (lentiviral vector, expressing renilla luciferase /RL/, red fluoroscein protein /RFP/ and herpes simplex truncated thymidine kinase /tTK, positron emmission tomography PET-reporter gene/) using serial PET imaging in pig myocardial infarction (MI).
Methods. Bone marrow (100 ml) was harvested from pigs immediately before induction of MI by percutaneous balloon occlusion of the LAD followed by reperfusion. The MSCs were selected and cultivated. The lentiviral vector LV-RL-RFP-tTK was inoculated into the MSCs under control of CMV promoter. The cells with the highest fluorescence intensity (after achieving appr. 50% transfection efficacy) were sorted, and tracked in vitro by PET using 9-(4-[18F]fluoro-3-hydroxymethylbutyl)-guanine (18FHBG). The transfected MSCs (at least 3 mio MSCs/ pigs) were then injected direct intramyocardially using NOGA electromagnetic guidance in pigs in 10 locations of the infarct border zone (min. 0.3 million cells/injection), followed by PET imaging 30 hours and 7 days later, after intravenous injection of 5 mCi 18FHBG.
Results. The in vitro 18FHBG uptakes of the transgene modified MSCs by PET were 10 times larger than the control JY human B-lymphoblasts and T lymphocytes. The minimum number of the cells detectable with PET was 0.2 million. MRI of the pigs revealed a mean global EF of 47+/-3.5%. PET imaging displayed diffuse distribution of the injected MSCs with high activity of the PET tracer in the anterior wall and septum at 30h, and less tracer activity in the injections sites with diffuse distribution in the pericardium and pleura indicating the wandering of the living cells at 7 days. PET imaging did not show 18FHBG accumulation in the infarcted heart of the control animals. Myocardial histology with RL and RFP staining confirmed the distribution of the injected MSCs through an elongated track around the injected area, 9 days after delivery.
Conclusion. In vivo tracking of gene-modified porcine MSCs by PET imaging is feasible and allows serial noninvasive imaging of homing and propagation of MSCs in pigs after MI.