In vivo imaging of bone marrow mesenchymal stem cells transplanted into myocardium using magnetic resonance imaging: a novel method to trace the transplanted cells.

BACKGROUND: In vivo imaging of the cells transplanted into the beating heart is very important for the study of the cell's retention, migration. This study was designed to find a new labeling agent to trace and visualize the transplanted cells in vivo.
METHOD: BMMSCs were incubated with SPIO for 48 h. The labeling efficiency was tested through Prussian blue staining, the growth ability was evaluated through MTT, and the cells viability was tested through Trypan blue rejection method, the migratory ability was assessed with Costar Transwell plates. After 10 days of coronary ligation of the Chinese mini swine, the labeled or unlabeled cells were transplanted into the myocardium. The MRI was carried out immediately and 1-4 weeks, respectively. After MRI the hearts were excised, the segment in which injections were performed were thin cut and stained with hematoxylin-eosin and Prussian blue staining.
RESULTS: There were intracytoplasmatic blue particles in nearly every cell in the Prussian blue staining. SPIO had no poison effect on the cells' growth and proliferation. The cells' viability was more than 95%. The migratory ability was not affected. The injected sites containing labeled cells could all be detected through MRI and were confirmed on pathology. After 4 weeks the injected labeled cells could still be detected through MRI. The pathology showed the injected cells could survive in the MI area, and parallel in the same direction.
CONCLUSION: The cells could be efficiently and safely labeled with SPIO and the labeled cells could be reliably detected by MRI in vivo.