Objective:To explore the proper concentration of superparamagnetic iron oxide (SPIO) labeling bone marrow mesechymal stem cells and the biological influence of different labeling concentrations

and to evaluate the characteristics of magnetic resonance imaging by a 1.5 T MR scanner. Methods:BMSCs (5th)were incubated with different concentrations of SPIO particles. The location

distribution and the labeling ratio of SPIO particles in cells were observed. At an optimal concentration

samples of SPIO-labeled and unlabeled MSCs suspension in agar were imaged by MRI with T1WI

T2WI and T2*WI. and the signal intensity were measured and statistically analyzed.Results:Labeled SPIO particles were stained in cytoplasm. BMSCs were efficiently labeled (97% to 100%)in culture at 24 hours and particle concentrations(25 to 50μg Fe/ml medium). Compared with unlabeled cells

BMSCs loaded with SPIO had similar viabilitv and proliferation profiles at this proper range of labeling concentration. SPIO labeling caused a stronger low signal attenuation effect in T1WI、T2WI andT2*WI. Conclusion:BMSCs can be easily and efficiently labeled by SPIO without interference on the cell viability and proliferation

MRI visualization of SPIO-labeled MSCs is feasible

which provrdes basis for future in vivo studies.