Abstract: Objective To observe the effect of rat bone marrow mesenchymal stem cells(BMSCs) labeled with superparamagnetic iron oxide(SPIO) in the magnetic field on the transplantation for rat focal cerebral ischemia. Methods The rat mesenchymal stem cells was labeled with SPIO in vitro , and prussian blue staining was used to check the rate of SPIO. The viability and proliferation activity of labeled stem cells was evaluated by trypan blue staining. The cck-8 assay was performed to detect the labeled stem cell proliferation activity in the magnetic field. The middle cerebral artery occlusion (MCAO) was established in a rat model, and the neurological severity score (NSS) was used to evaluate neurological function recovery of rats at definite time following the injection of transplanted cells. The transplanted BMSCs were analyzed in recipient rat brains by Prussian blue staining. The cerebral ischemia area was observed via TTC staining. The iron content of SPIO-labeled BMSCs was analyzed by atomic absorption spectrophotometer. Results Prussian blue staining showed that the rate of BMSCs labeled superparamagnetic iron oxide was close to 100％. Trypan blue staining indicated that there was no significant difference between labeled group and control group （P>0.05）. CCK-8 assay suggest that there was no significant difference between magnetic group and control group （P>0.05）. The BMSCs of ICSM group within the brain was significantly more than the BMSCs of ICS group (P < 0.05). The ICSM group with ischemia seven days later showed better compared to the other two groups. The difference was significant ( P< 0. 05) . The brain iron content in the ICSM group was largely more than that in the ICS group (P<0.05). Conclusion External magnetic field can target delivery bone marrow mesenchymal stem cells labeled with superparamagnetic iron oxide in vitro and in vivo, and can obviously improve the transplantation of SPIO-Labeled mesenchymal stem cells.

Key words: Key words：magnetic field , bone marrow mesenchymal stem cells, superparamagnetic iron oxide , brain infarction, migration