Efficient tracking of non-iron-labeled mesenchymal stem cells with serial MRI in chronic stroke rats

Background and Purpose-Although stem cell-based treatments for neurodegenerative diseases have advanced rapidly, there is currently no clinically available method to monitor the fate of transplanted cells in the brain. Methods-To use magnetic resonance imaging for tracking transplanted stem cells in the ischemic rat brain, we used the cellular labeling substance Effectene to transfect a standard contrast agent (Gd-DTPA) into immortalized human bone marrow stromal cells. Results-The transfection efficiency of this method was up to 90%, which is substantially better than pure spontaneous endocytosis or other transfection agents. In addition, cellular uptake of Gd-DTPA in vitro was maintained for > 28 days. Therefore, we could follow transplanted stem cell migration and homing into the penumbric area. Using double immunofluorescence, the transplanted cells were seen to differentiate into glial cells, neurons and vascular endothelial cells. Cortical neurochemical activity as evaluated by proton magnetic resonance spectroscopy (H-1-MRS) also increased considerably after immortalized human bone marrow stromal cell transplantation. Conclusion-This method of tracking immortalized human bone marrow stromal cells is highly efficient and allows for nontoxic labeling of cells. (Stroke. 2007;38:367-374.)