Porcine bone marrow-derived mesenchymal stem cells (MSCs) were stably transfected with a lentiviral vector for transgene expression of the trifusion protein renilla luciferase, red fluorescent protein and herpes simplex truncated thymidine kinase (LV-RL-RFP-tTK; positron emission tomography [PET] reporter gene) for in vivo noninvasive tracking of the intramyocardially delivered MSC fate. A closed-chest, reperfused myocardial infarction was created in farm pigs. Sixteen days after myocardial infarction, LV-RL-RFP-tTK-MSCs were injected intramyocardially using electromechanical mapping guidance in the infarct border zone (n=7). PET-computed tomographic metabolic and perfusion imaging was performed after an intravenous injection of 10 mCi [18F]-FHBG and 13N-ammonia PET at 30+/-2 hours and 7 days after LV-RL-RFP-tTK-MSC treatment. Fusion imaging of the [18F]-FHBG PET-computed tomography with MRI was used to determine the myocardial location of the injected LV-RL-RFP-tTK-MSCs. Seven days after injections, [18F]-FHBG PET showed a decreased cardiac uptake with a mild increased pericardial and pleura uptake in the treated animals, which was confirmed by the measurement of luciferase activity. At 10 days, infarct size by MRI in the LV-RL-RFP-tTK-MSC-treated animals was smaller than controls (n=7) (23.3+/-1.5% versus 30.2+/-3.5%, P<0.005). The presence of the LV-RL-RFP-tTK-MSCs (5.8+/-1.1% of the injected cells) in the myocardium 10 days after intramyocardial delivery was confirmed histologically. Reporter gene imaging enables the tracking of the persistence of viable LV-RL-RFP-tTK-MSC in the peri-infarcted porcine myocardium at 10 days after delivery using clinical PET scanners.

Our purpose was to confirm the local drug delivery of a paclitaxel-eluting balloon by percutaneous intervention of single arterial segments or bifurcations of porcine coronary arteries. Eight domestic pigs were subjected to 2 x 30 s Dior balloon dilatation of the mid left anterior descending, left circumflex and proximal right coronary arteries. Bifurcation intervention was performed in six arteries. The dilated, and the distal and proximal reference segments were prepared for tissue paclitaxel concentration measurement. Tissue samples were harvested at mean 1.5, 12, 24 and 48 h after balloon dilatation and plasma samples were taken at various time points. The tissue paclitaxel concentration of the single dilated segment was at 1.5 h postdilatation 1.82+/-1.60 micromol/l, which decreased significantly to 0.73+/-0.27 (P=0.032), 0.62+/-0.34 and 0.44+/-0.31 micromol/l at 12, 24 and 48 h. The bifurcation intervention resulted in 5.10+/-1.80 micromol/l tissue paclitaxel amount in the main branch, which at 12 h had diminished to 1.41+/-1.23 micromol/l (P=0.004). The bifurcation side contained 7.00+/-4.80 micromol/l paclitaxel at 1.5 h postdilatation, which lowered to 2.72+/-0.40 micromol/l (P=0.034). The mean paclitaxel concentration of the reference segments decreased gradually from 0.84+/-0.99 to 0.34+/-0.36 micromol/l (P=0.09), 0.28+/-0.16 and 0.19+/-0.18 micromol/l tissue at 1.5, 12, 24 and 48 h postdilatation, respectively. No paclitaxel was found in the peripheral blood at any time point. Short exposure of the coronary artery to paclitaxel with a coated balloon is sufficient for the attainment of an adequate tissue concentration of paclitaxel, which is known to be efficient in inhibiting neointimal growth.