Abstract: Objective To label Flk-1+CD31-CD34- human Mesenchymal Stem Cells (hMSCs) with Superparamagnetic Iron Oxide (SPIO) and evaluate the effect of SPIO on proliferation and neural differentiation of labeled cells. Methods hMSCs were incubated with SPIO (50mg/L) and PLL (1.5mg/L) overnight(12-18 hours). Both labeled and unlabeled cells went through growth curve test，Trypan blue staining and flow cytometer to evaluate the effects of SPIO on cell proliferation，cell viability and surface markers. Immunofluorescence assay was conducted for neuron and neuroglia specific cell surface markers after neural induction protocols were used. Results Cell viability results of two groups were both more than 90% in the following 7 days. There was no significant difference on cell viability and growth curve test between two groups. The results of flow cytometer showed that both labeled and unlabeled cells expressed CD44, CD105 and Flk-1 markers, while CD31 and CD34 were negative. After neural induction, the statistical analysis of A value for all the markers showed no significant difference between the two groups. Methods: hMSCs were incubated with Feridex (50mg/L) and PLL (1.5mg/L) overnight(12-18 hours). Both labeled and unlabeled cells went through growth curve test Trypan blue staining and flow cytometer to evaluate the effects of Feridex on cell proliferation，cell viability and surface markers. Immunofluorescence assay was conducted for neuron and neuroglia specific cell surface markers after two kinds of neural induction protocols were used. Results：After incubated with Feridex and PLL overnight, the labeling rate of hMSCs could be 96％. Cell viability results of two groups were both more than 90% in the following 7 days，indicating that Feridex didn’t cause significant cell death. There was no significant difference on cell viability and growth curve test between two groups. The results of flow cytometer showed that both labeled and unlabeled cells expressed CD44, CD105 and Flk-1 markers, while CD31 and CD34 were negative. According to the two kinds of neural induction protocols, the statistical analysis of OD for all the markers showed no significant difference between the two groups. Conclusions: Incubated with Feridex(50mg/L) and PLL(1.5mg/L) overnight could effectively label hMSCs. Feridex shows no significant influence on cell viability, proliferation, cell surface markers and neural differentiation. Feridex, as MRI cellular contrast, is safe and efficient.Conclusions SPIO, as MRI cellular contrast, is safe and efficient.

Key words: Superparamagnetic Iron Oxide, Feridex, Mesenchymal Stem Cell, Stem Cell Transplantation