Magnetic Resonance Imaging of Stem Cell Transplantation in Injured Mouse Spinal Cord

BACKGROUND: Several types of cell-mediated treatments have been studied in order to establish their potential usefulness in promoting neural tissue regeneration and repair after spinal cord injury (SCI). We recently isolated a subclass of mouse neural progenitors, capable of surviving a powerful ischemia insult, and their differentiation yield mostly neurons compared to regular neural stem cells (NSCs). One of the main difficulties in analyzing the effects of transplanted cells during the time is the distribution evaluation of injected cells and their target organ localization. MATERIALS AND METHODS: We labeled NSCs with Iron Oxide paramagnetic nanoparticles (Endorem®), stem cell features and differentiation capabilities of iron-labeled cells were investigated by immunofluorescence. Iron-labeled cells were injected in tail vein and their distribution was tracked by Magnetic Resonance Imaging (MRI) and demonstrated histochemically. RESULTS AND DISCUSSION: We observed that the increase in number of iron-positive cells during the labeling procedure was proportional to the iron concentration in the medium. A higher labeling was observed when Protamine sulfate (PrS) was used as carries. Stem cell features and differentiation capabilities were unaffected by iron-labelling. MRI visualization showed that labeled NSCs were accumulated at the lesion site, differently no labeling was detected in the injured cord when free iron nanoparticles or dead labeled cells were administered. Moreover, labeled NSCs promoted hind limb recovery of function through the experimental period. CONCLUSIONS: Our study shows that NSCs can be efficiently labeled with dextran-coated paramagnetic nanoparticleswithout significant alteration of their physiological and functional features. MRI may result useful in the study of stem cell localization at the lesion site in murine models of SCI.