Dual-modality Bioluminescence And MRI In Monitoring Mesenchymal Stem Cell Therapy In Myocardial Infarction

Objective:we utilized firefly luciferase(Fluc) and a fluorescent dye CyI(derived from Cy5) to label bone marrow-derived mesenchymal stem cell(BMSC) from SD rats, and verified its effectiveness in vitro. Then we chose rats and mice with different weight as myocardial infarction model, and injected the double-labeled BMSC in to myocardium to find the proper animal model. Finally, we conbined ultrasmall superparamagnetic iron oxide(USPIO) with Fluc to track stem cell dual-modality by optical imaging(OI) and magnetic resonance imaging(MRI) after injected in myocardial infarction model to observe its survival, proliferation and terotoma formation.Methods and materials:We diluted BMSC/Fluc which successfully transfected with Fluc into different concentrations, and detected bioluminescence imaging (BLI) in vitro. Incubated BMSCs/Fluc with CyI of different concentrations for different hours to find the optimal condition for Cyl labeling. Incubated BMSCs/Fluc with40μg/ml USPIO and1.5μg/ml poly-1-lysine (PLL) for24h. The distributions of iron particles in cells were studied by Prussian blue staining. In vivo, acute myocardial infarction models of200g,150g,100g SD rats and20-25g Bal b/c mice were established by ligating the left anterior descending coronary artery (LAD). CyI labeled BMSCs/Fluc were transplanted to myocardium by injection. BLI signals were measured1day after operation. We chose a positive model (Bal b/c mouse) for the proceeding experiments. USPIO labeled BMSCs/Fluc were transplanted to myocardial infarcted mice, BLI signals were measured in day1,3,6,9, and MRI were performed in day3. Postmortal study was carried out to observe the distribution of USPIO particles in heart by Prussian blue stain.Results:In Vitro, fluorescent signal was detected the most intensive when the incubation concentration and incubation time was1.0×10-6nd4h respectively. The signal intensities of CyI and Fluc were both increased linearly with cell number increase. In vivo, there was no CyI signal detected in rats and mice myocardial infarction model. While ex vivo fluorescent signal could be detected in all the models. BLI signal could be detected only in Bal b/c mice model, rather than rats model. After USPIO labeled BMSCs/Fluc were transplanted into mice myocardial infarction model, the intensity of BLI signal decreased consistently, which represent stem cells died gradually, and no proliferation, migration and teratoma formation was detected.Conclusions:1. CyI could effectively label BMSCs/Fluc in vitro, and could be used in ex vivo stem cell labeling;2. Fluc could be used in in vivo stem cell tracking after transplanted in Bal b/c mice myocardial infarction model;3. After USPIO labeled BMSC/Fluc transplanted into myocardium of Bal b/c mice of myocardial infarction model, BLI signal showed stem cell died gradually. And no proliferation, migration and teratoma formation is detected. Simutaneously, MRI could sensitively detect USPIO labeled cells in vivo.