99mTc-Based Imaging of Transplanted Neural Stem Cells and Progenitor Cells

Cell therapy for neurologic disorders will benefit significantly from progress in methods of noninvasively imaging cell transplants. The success of current cell therapy has varied, in part because of differences in cell sources, differences in transplantation procedures, and lack of understanding of cell fate after transplantation. Standardization of transplantation procedures will progress with noninvasive imaging. In turn, in vivo imaging will enhance our understanding of neural transplant biology and improve therapeutic outcomes. The goal of this study was to determine the effect of a (99m)Tc-based probe on neural stem and progenitor cell transplants and validate the SPECT images of the transplanted cells. METHODS: We previously developed a method to label neural stem and progenitor cells with (99m)Tc to visualize these cells in the brain with SPECT. The cells were initially labeled with a permeation peptide carrying a chelate for (99m)Tc. The proliferation and differentiation characteristics of the labeled cells were studied in tissue culture. In parallel experiments, the labeled cells were stereotactically injected into the rat brain, and the site of transplantation was verified with histochemistry and phosphorimaging. RESULTS: The accuracy of the transplant location obtained by SPECT was confirmed by comparison with phosphorimages and histologic sections of the brain. The labeling did, however, decrease the proliferative capacity of the neural stem and progenitor cells. CONCLUSION: The labeling technique described here can be used to standardize the location of cell transplants in the brain and quantify the number of transplanted cells. However, a (99m)Tc-based probe can decrease the cellular proliferation of neural progenitor cells.