Tracing type 1 diabetic Tibet miniature pig's bone marrow mesenchymal stem cells in vitro by magnetic resonance imaging

BackgroundTraditional cell-tracking methods fail to meet the needs of preclinical or clinical research. Thus, the aim of the present study was to establish a new method of double labeling bone marrow mesenchymal stem cells (BMSCs) from type 1 diabetic (T1D) minipigs with super-paramagnetic iron oxide (SPIO) and enhanced green fluorescent protein (eGFP) and tracing them using MRI in vitro. MethodsIsolated BMSCs from T1D minipigs were labeled with eGFP and different concentrations of SPIO. The effects of lentivirus (LV)-eGFP transfection and SPIO on the viability and growth curves of BMSCs were determined by Trypan blue exclusion, the 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide assay and flow cytometry. Cellular ultrastructure was evaluated by transmission electron microscopy. Magnetic resonance imaging was used to evaluate BMSCs labeled with SPIO-eGFP complexes 6 weeks after labeling. ResultsExpression of eGFP in BMSCs peaked 96h after transfection with LV-eGFP. Prussian blue staining revealed scattered blue granules in the cytoplasm of SPIO-labeled cells. Transmission electron microscopy revealed that the dense granules aggregated mainly in secondary lysosomes. On MRI, T-2*-weighted imaging was far more sensitive for SPIO-labeled BMSCs than other image sequences 3 and 6 weeks after the cells had been labeled with SPIO-eGFP. ConclusionsWe have developed a relatively simple and safe method for double labeling of BMSCs from T1D minipigs using SPIO and LV-eGFP and tracing them in vitro by MRI for 6 weeks.