In Vitro MR Imaing Of Superparamagnetic Iron Oxide Labeled Pig Mesenchymal Stem Cells

Background: Stem cell transplantation is the hot spots and front edge of investigation inmedical domain at the present stage, it has been used as the routine method in someclinical disease after the exploratory clinical trial, especially in the heart, vessel and blood,furthermore the technique has stepped to maturate. But now the commonly used method toobserve the therapeutic effect after transplant is to analyze tissue section in ex vivocondition, can we monitor the transplanted stem cells real time in vivo finally? Followingthe concept of molecular imaging, the problem troubling clinical medicine workers formany years has been solved with the greatest ease.PartⅠObjective To in vitro evaluate the labeling method of pig mesenchymal stem cells(MSCs) with superparamagnetic iron oxide (SPIO) nanoparticles, and to detect thecharacteristics by a 1.5-T MR scanner and the lowest cells quantity that can be observed.Methods MSCs were isolated from pig and incubated with SPIO particles. In order toevaluate the labeling efficiency of SPIO, the labeld cells were stained by prussian blue andobserved under fluorescent microscope. MTT growth curves were obtained at a range ofSPIO concentrations (5 to 80μg Fe per ml medium) to assess the effects of the particles oncell proliferation. Samples of SPIO-labeled and unlabeled MSCs with differentconcentration were imaged by MRI with T1Wi,T2WI and fast field echo (FFE) sequences,and the signal intensity were imaged and statistically analyzed.Rusults MSCs could be labeled with SPIO and labeling efficiency was 100%, Prussianblue staining showed numerous blue-stained iron particles in the cytoplasm. SPIO labelingcaused a stronger low signal attenuation effect in FFE and T2WI than in T1WI. The signal.intensity had significant difference between T2WI or FFE and T1WI in 1.ST MPd ofSPIO-labeled cells. At a labeling concentration of 25μg Fe per ml medium, MRIdemonstrated that 1×10~5 SPIO-labeled cells per ml medium was the lowest observable cells quantity.Conclusion MSCs can be easily and efficiently labeled by SPIO without interference onthe cell viability and proliferation, MRI visualization of SPIO-labeled MSCs is feasible inboth T2WI and FFE.PartⅡObjective To in vitro evaluate the labeling efficiency of pig mesenchymal stem cells(MSCs) with variety classes of superparamagnetic iron oxide (SPIO) nanoparticles,and to detect the different characteristics by a 1.5-T MR scanner.Methods MSCs were isolated from pig and incubated with variety classes of SPIOparticles. The labeld cells were stained by prussian blue and observed under fluorescentmicroscope. Samples of SPIO-labeled MSCs with the same 1×10~6 concentration wereimaged by MRI with TlWI, T2WI and fast field echo (FFE) sequences, and the signalintensity were imaged and statistically analyzed.Results Between the variety classes of SPIO, the labeling efficiency of the 1~#,3~# USPIOand Feridex was 100%, but the 2~# USPIO was slightly worse about 98%. The signalintensity had significant difference between the 2~#,3~# USPIO and Feridex in T2WI andFFE. However the signal intensity had no significant difference between the 1~# USPIO andFeridex in T2WI and FFE.Conclusion MSCs also can be easily labeled with USPIO that triturated ourselves,There isn't conclusive linear relationship between the labeling efficiency, the signalintensity and the particle size of iron.