The use of magnetic resonance cell tracking to monitor endothelial progenitor cells in a rat hindlimb ischemic model.

A water-soluble magnetic resonance imaging (MRI) contrast agent, Dextran mono-N-succinimidyl 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate-gadolinium(3+) (Dex-DOTA-Gd(3+)), was shown to enable monitoring of the anatomical migration and the survival period of transplanted stem cells for up to 1 month. Gadolinium molecules in the cells were rapidly eliminated from the site and excreted upon cell death. Endothelial progenitor cells (EPCs) transplanted into the inguinal femoral muscle of rats migrated distally through the knee in rats after hindlimb ischemia but did not migrate in non-ischemic rats. Interestingly, the survival period of transplanted EPCs was notably prolonged in the ischemic limb, indicating that EPCs are required by the ischemic tissues and that the fate of transplanted EPCs was affected by the disease. Compared to the commonly used particle type of MRI contrast agents, the system described in this study is expected to be invaluable to help clarifying the process of stem cell transplantation therapy.