In vivo tracking of implanted stem cells using radio-labeled transferrin scintigraphy

The possibility of monitoring stein cells in vivo with radionuclide imaging after transplantation was investigated. Based on the results of a radioligand receptors assay that human mesenchymal stein cells (hMSCs) express a high level of transferrin receptors, iodinated transferrin (I-131-Tf(Fe)(2)) was chosen as the radiotracer for imaging the cells implanted into the spinal cords of rabbits. Accumulation of radioactivity at the cell transplanted sites was assessed 16 and 24 hours post-intrathecal injection of I-131-Tf(Fe)(2). Transferrin receptors expression and Tf binding of the implanted cells were verified by immunofluorescence, and ex vivo phosphor imaging. The specificity of Tf uptake of hMSCs was proved through control experiments, i.e., replacing I-131-Tf(Fe), with I-131 labeled human serum albumin as the tracer or substituting hMSCs with phosphate buffered saline as the grafts. Despite some defects, such as the invasive administration of the tracer and the non-specificity of transferrin receptors as a marker of stem cells in this preliminary study, the technique of nuclear medicine imaging is considered to have great potential in tracking implanted cells in vivo. (C) 2004 Elsevier Inc. All rights reserved.