Monitoring transplanted human mesenchymal stem cells in rat and rabbit bladders using molecular magnetic resonance imaging.

AIMS This study investigated whether superparamagnetic iron oxide (SPIO)-labeled human mesenchymal stem cells (hMSCs) may be monitored non-invasively by in vivo magnetic resonance (MR) imaging with conventional 1.5-T system examinations in the bladders of rats and rabbits. METHODS SPIO were transferred to hMSCs, using GenePORTER. After SPIO-labeled hMSCs were transplanted into the animal bladders, serial T2-weighted MR images and histological examinations were performed over a 4-week period. RESULTS hMSCs loaded with SPIO, compared to unlabeled cells, showed similar viability. SPIO-labeled hMSCs underwent normal chondrogenic, adipogenic, and osteogenic differentiation. For SPIO-labeled hMSCs concentrations that were greater than 1x10(5), in vitro MR images showed a decrease in signal intensity. MR signal intensity at the areas of SPIO-labeled hMSCs in rat and rabbit bladders were decreased and confined locally. After injection of SPIO-labeled hMSCs into the bladder, MR imaging demonstrated that hMSCs could be seen for at least 12 weeks post-injection. The presence of iron was confirmed with Prussian blue staining in histological sections. CONCLUSIONS Our findings suggest that hMSCs in animal bladders can be monitored non-invasively with conventional MR imaging.