BACKGROUND:Resovist,a superparamagnetic iron oxide,can be used to label neural stem cells(NSCs).Magnetic resonance tracking of superparamagnetic iron oxide-labeled NSCs is a non-invasive technique to track transplanted NSCs following focal cerebral ischemia.OBJECTIVE:To observe survival and migration of transplanted NSCs in a rat model of focal ischemia/reperfusion using magnetic resonance imaging(MRI).DESIGN,TIME AND SETTING:An in vitro,in vivo,tracking study was performed at the Basic Laboratory of Harbin Medical University and the Room of MRI,Second Affiliated Hospital of Harbin Medical University,China from December 2006 to December 2009.MATERIALS:Resovist(Schering,Germany) and Achieva 1.5TMR imaging system(Philips,Amsterdam,the Netherlands) were utilized in the present study.METHODS:NSCs were harvested from brain tissues of neonatal Sprague Dawley rats and were labeled with Resovist(11.2 μg/mL and 5 × 105 cells/mL).A total of 15 adult,Sprague Dawley rats were randomly assigned to model(n = 9) and control(n = 6) groups.All rats were utilized to establish models of middle cerebral artery occlusion.Rats in the model group were subjected to Resovist-labeled NSCs transplantation by injection of cell suspension into both ventricles(5 μL/ventricle).Rats in the control group were treated with an equal volume of physiological saline.MAIN OUTCOME MEASURES:Immunocytochemistry,transmission electron microscopy,and Prussian blue staining were employed to observe whether cells phagocytized iron particles.In addition,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to measure viability and differentiation of NSCs labeled by various concentrations of Resovist.MRI was used to trace survival and migration of Resovist-labeled NSCs.RESULTS:Following Resovist and NSCs co-incubation,Prussian blue staining revealed iron particles in cells.In addition,staining was observed in daughter cells following cell division under transmission electron microscopy.A significant difference in viability and differentiation of NSCs in vitro labeled by various Resovist concentrations(2.8-11.2 μg/mL) was not detected(P > 0.05).Resovist(> 22.4 μg/mL) decreased cell viability and differentiation(P < 0.05).In vivo MRI of Resovist-labeled NSCs(11.2 μg/mL) revealed low signals.However,cells migrated towards the ischemic focus over time.CONCLUSION:Resovist,a magnetic probe,successfully labeled NSCs.MRI was successfully used to trace magnetic-labeled NSCs in vivo and allowed observation of cell survival and migration following transplantation. BACKGROUND: Resovist, a superparamagnetic iron oxide, can be used to label neural stem cells (NSCs). Magnetic resonance tracking of superparamagnetic iron oxide-labeled NSCs is a non-invasive technique to track transplanted NSCs following focal cerebral ischemia. OBJECTIVE: To observe survival and migration of transplanted NSCs in a rat model of focal ischemia / reperfusion using magnetic resonance imaging (MRI). DESIGN, TIME AND SETTING: An in vitro, in vivo, tracking study was performed at the Basic Laboratory of Harbin Medical University and the Room of MRI, Second Affiliated Hospital of Harbin Medical University, China from December 2006 to December 2009. MLS: Resovist (Schering, Germany) and Achieva 1.5 TMR imaging system (Philips, Amsterdam, the Netherlands) were utilized in the present study. METHODS : NSCs were harvested from brain tissues of neonatal Sprague Dawley rats and were labeled with Resovist (11.2 μg / mL and 5 × 10 5 cells / mL). A total of 15 adult, Sprague Dawley rats were randomly assigned t O models (n = 9) and control (n = 6) groups. All rats were utilized to establish models of middle cerebral artery occlusion. Rats in the model group were subjected to Resovist-labeled NSCs transplantation by injection of cell suspension into both ventricles (5 μL / ventricle). Rats in the control group were treated with an equal volume of physiological saline. MAIN OUTCOME MEASURES: Immunocytochemistry, transmission electron microscopy, and Prussian blue staining were employed to observe whether cells phagocytized iron particles. In addition, 3 - (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide assay was used to measure viability and differentiation of NSCs labeled by various concentrations of Resovist. MRI was used to trace survival and migration of Resovist-labeled NSCs. RESULTS: Following Resovist and NSCs co-incubation, Prussian blue staining revealed iron particles in cells. In addition, staining was observed in daughter cells following cell division under transmission electron microscopy. ignificant difference in viability and differentiation of NSCs in vitro labeled by various Resovist concentrations (2.8-11.2 μg / mL) was not detected (P> 0.05) .Resovist (> 22.4 μg / mL) decreased cell viability and differentiation . In vivo MRI of Resovist-labeled NSCs (11.2 μg / mL) revealed low signals. Despite, cells migrated towards the ischemic focus over time. CONCLUSION: Resovist, a magnetic probe, successfully labeled NSCs.MRI was successfully used to trace magnetic- labeled NSCs in vivo and allowed observation of cell survival and migration following transplantation.