Imaging of Stem Cell Recruitment to Ischemic Infarcts in a Murine Model

Background and Purpose— Neural progenitor cells (NPC) have been reported to aid in the functional recovery from stroke and hold promise as a novel treatment for a variety of neurological diseases. There is a need for imaging tools to study the in vivo migratory behavior of these cells. Methods— C17.2 NPC, stably transfected with firefly luciferase, were serially imaged through intact skull and skin by bioluminescence imaging over 2 to 3 weeks in nu/nu mice with closed-vessel middle cerebral artery infarcts, followed by contralateral intraparenchymal or intraventricular injections of NPC. Results— NPC migrated to the site of infarct from the contraleral parenchyma, crossing the midline at 7 days. In control animals without infarcts, NPC remained at the site of administration. Intraventricular cell administration resulted in a wide distribution of cells, including the site of infarct. Within the infarct area, NPC colabeled with the neuronal marker NeuN and with astroglial marker glial fibrillary acidic protein. The time course and magnitude of NPC recruitment were longitudinally compared between the treatment groups. Conclusions— NPC recruitment to infarct can be assessed noninvasively by serial in vivo imaging. Images correlate well with histological cell distributions. NPC are recruited to infarcts with both parenchymal and cerebrospinal fluid administration, but higher initial photon counts suggest that cerebrospinal fluid administration is more efficient at early infarct seeding.