Ultrasmall Superparamagnetic Iron Oxide (USPIO) Mark SD Rat Adipose Derived Stem Cells In Vitro And In Vivo Study (ADSCs)

Objective:To investigate the efficacy and safety of ultrasmall superparamagnetic iron oxide (USPIO) labeling adipose derived stem cells (ADSCs) of SD rats, and the feasibility of tracing labeled cells with MR imaging was studied both in vitro and in vivo.Methods and Materials:ADSCs were incubated with culture medium containing40μg/ml USPIO and1.5ug/ml poly-1-lysine (PLL) for24h. The distribution of iron particles in cells was studied by Prussian blue staining and transmission electron microscopy(TEM). Besides, trypan-Blue stain and MTS were used to determine the cell viability and proliferation. ELISA assay was used to compare the vascular endothelial growth factor (VEGF) levels in culture medium between labeled cells and control group. In vitro, T2map and the T2*map sequence were selected to study the correlation between the number of labeled cells and MR signals (T2, T2*, R2and R2*). In vivo, SD rat model of acute myocardial infarction was established by ligating the anterior descending coronary artery(LAD). The labeled ADSCs were transplanted through both the tail vein and myocardial direct injection, then MR was performed to trace the cells. Postmortal study was carried out to observe the distribution of USPIO particles in the various organs with Prussian blue stain.Results:After incubating the cells with USPIO and PLL for24h, the percentage of labeled ADSCs reached up to99%. Iron particles inside the cells were confirmed by TEM, which mainly in lysosomes. Trypan-Blue stain showed the number of living cells was greater than95%. MTS experiments suggest that USPIO (10,20,40,80,160μg/ml) exert no significant influence on the proliferation of ADSCs. ELISA assay revealed VEGF levels in culture medium were positively correlated with the number of cells. No significant difference was found between labeled cells and the control group. MR imaging was sensitive detecting USPIO labeled cells in vitro, T2and T2*value could be quantitatively measured by T2map and T2*map sequences. In addition, linear correlations between cell numbers and R2or R2*values were discovered. Under mechanical ventilation, the SD rats model of acute myocardial infarction was successfully established by ligating anterior descending coronary artery (LAD). The signal of liver decreased after intravenous injection of labeled cells. The signal intensity in myocardium had no significant change through intravenous injection; while it decreased significantly when labeled cells were injected directly into myocardium. Prussian blue staining diplayed only a few USPIO particles in the infracted myocardium, the major part however, distributed in spleen.Conclusion:1. Using USPIO(40μg/ml) and PLL(1.5μg/ml) could safely and effectively label ADSCs2. USPIO labeling had no significant effect on VEGF secreted by ADSCs3. MRI could sensitively detect USPIO labeled cells in vitro, with a positive linear correlation between R2and R2*values and cell numbers.4. The sensitivity of detection of USPIO-labeld ADSCs in vivo by MRI was influenced by transplanted pathway.