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[Biological characteristics and MR imaging of superparamagnetic iron oxide labeled BMSCs].

OBJECTIVE
To explore the labeling efficiency and cellular viability of rabbit BMSCs labeled with different concentrations of superparamagnetic iron oxide (SPIO) particles, and to determine the feasibility of magnetically labeled stem cells with MR imaging.


METHODS
The BMSCs were collected from iliac marrow of 10 adult rabbits (weighing 2.5-3.0 kg) and cultured. The SPIO-poly-L-lysine compound by different ratios mixed with medium, therefore, the final concentration of Fe2+ was 150 (group A), 100 (group B), 50 (group C) and 25 microg (group D) per mL, respectively, the 3rd generation BMSCs culture medium was added to lable; non-labeled cells served as a control (group E). MR imaging of cell suspensions was performed by using T1WI and T2WI sequences at a clinical 1.5 T MRI system.


RESULTS
BMSCs were efficiently labeled with SPIO, labeled SPIO particles were stained in all cytoplasms of groups A, B, C and D. With the increasing of Fe2+ concentration, blue dye particles increased. The staining result was negative in group E. The cell viability in groups A, B, C, D and E was 69.20% +/- 6.11%, 80.41% +/- 2.42%, 94.32% +/- 0.67%, 96.24% +/- 0.34% and 97.43% +/- 0.33%, respectively. There were statistically significant differences between groups A, B and groups C, D and E (P < 0.05), and between group A and group B (P < 0.05). T1WI images had no specific difference among 5 groups, T2WI images decreased significantly in groups A, B, C, decreased slightly in group D, and had little change in group E. The T2WI signal intensities of groups A, B, C, D and E were 23.37 +/- 6.21, 26.73 +/- 3.60, 29.63 +/- 2.82, 45.03 +/- 6.76 and 783.15 +/- 7.38, respectively, showing significant difference between groups A, B, C, D and group E (P < 0.05), and between groups A, B, C and group D (P < 0.05).


CONCLUSION
BMSCs can be easily and efficiently labeled by SPIO without interference on the cell viability in labeled concentration of 20-50 microg Fe2+ per mL. MRI visualization of SPIO labeled BMSCs is feasible, which may be critical for future experimental studies.