Using a neodymium magnet to target delivery of ferumoxide-labeled human neural stem cells in a rat model of focal cerebral ischemia.

Efficiency of targeted delivery of stem cells via transplantation by intravenous injection is limited because of rapid clearance. Thus, more effective, newer methods are required. We hypothesized that combining the use of ferumoxide labeling and magnetic fields could enhance targeted delivery of stem cells. The effects of a magnetic field on proliferation, viability, and differentiation of human neural stem cells (NSCs) were determined in culture, and the results indicated that the difference between control and cultures exposed to a magnetic field were insignificant. To assess migration in vitro, ferumoxide-labeled cells were seeded into a culture dish that had a neodymium magnet below its center, and the labeled NSCs were found to aggregate above the magnet. To investigate targeted delivery of NSCs in vivo, rats were separated into three groups: ischemia only (IO), ischemia with injection of ferumoxide-labeled cells (IC), and ischemia with injection of labeled cells and magnet exposure (ICM). Twenty-four hours after middle cerebral artery occlusion (MCAo), labeled human NSCs were injected into the tail vein. Seven days after MCAo, ICM rats had a larger number and greater distribution of Prussian blue-positive NSCs as compared with controls. In addition, infarct volume in ICM rats was significantly reduced. Our study suggests that this use of a magnetic field may be useful for improving the efficacy of targeted migration of stem cells in stem-based cell therapy in ischemic brain injury.