Near-Infrared Fluorescence Labeling Allows Noninvasive Tracking of Bone Marrow Stromal Cells Transplanted Into Rat Infarct Brain

Abstract

Noninvasive imaging techniques would be needed to validate the therapeutic benefits of cell transplantation therapy for central nervous system disorders. To evaluate whether near-infrared (NIR)-emitting fluorescence tracer, quantum dots, would be useful to noninvasively visualize the bone marrow stromal cells (BMSC) transplanted into the infarct brain in living animals. Rat BMSCs were labeled with QD800. In vitro and in vivo conditions to visualize NIR fluorescence were precisely optimized. The QD800-labeled BMSCs were stereotactically transplanted into the ipsilateral striatum of the rats subjected to permanent middle cerebral artery occlusion 7 days after the insult. Using the NIR fluorescence imaging technique, the behaviors of BMSCs were serially visualized during the 8 weeks after transplantation. NIR fluorescence imaging could noninvasively detect the NIR fluorescence emitted from the transplanted BMSCs engrafted in the peri-infarct neocortex through the scalp up to 8 weeks after transplantation. The intensity gradually increased and reached the peak at 4 weeks. The results were supported by the findings on ex vivo NIR fluorescence imaging and histological analysis. NIR fluorescence imaging is valuable in monitoring the behaviors of donor cells in the rodent brain. The results would allow new opportunities to develop noninvasive NIR fluorescence imaging as a modality to track the BMSCs transplanted into the brain.