In vivo MR tracking of magnetically labeled mesenchymal stem cells in rat liver after intrasplenic transplantation

Objective: To evaluate the 1.5-T magnetic resonance imaging system to depict and track in vivo of magnetically labeled bone mesenchymal stem cells (BMSCs) in rat liver after intrasplenic transplantation. Methods: Rat BMSCs were isolated, purified, expanded and then incubated with home synthesized Fe2O3-PLL. Prussian blue stain was performed for showing intracellular irons. Acute liver damage was induced by subcutaneous injection of carbon tetrachloride in 12 recipient rats. The cells allotransplantation was performed by intrasplenic injection with magnetically labeled (experimental group, n=6) or unlabeled BMSCs (control group, n=6). Serial MRI were performed before and 3 hours, 3, 7, 14 days after transplantation. Signal-to-noise ratio (SNR) of liver on T2*-weighted MR imaging obtained before and after injection were measured and compared. MR imaging findings were compared histologically with histology. Results: Rats BMSCs could be effectively labeled and the labeling efficiency was almost 100%. Iron-containing intracytoplasmatic vesicles could be observed clearly with prussian blue staining. SNR of rat livers in experimental group and control group before and 3 hours, 3, 7, 14 days after transplantation were 19.53±2.30, 3.28±1.06, 7.34±2.10, 10.25±3.96, 15.50±3.73; 20.20±4.35, 21.20±4.43, 19.13±2.80, 21.43±5.45, 19.07±4.80, respectively. SNR decreased significantly in the experimental group liver 3 hours, 3, 7 days after injection of BMSCs (Dunnett test, P<0.05), and returned gradually at approximately day 14 to that of rat livers before injection (Dunnett test, P>0.05). In control group, SNR demonstrated no significant differences among different time points (ANOVA, P>0.05). Results of histological analysis confirmed homing of labeled BMSCs in liver, primarily distributing in areas around centrolobular vein. Conclusion: The BMSCs can be effectively labeled with Fe2O3-PLL. 1.5-T MR imaging can monitor in vivo of magnetically labeled BMSCs in liver after intrasplenic transplantation. It potentially opens a new area of investigation for delivering stem cells. (authors)