Transferrin Receptor Expression in Iron Oxide–labeled Mesenchymal Stem Cells

摘要

In the August 2007 issue of Radiology, Dr Schäfer and colleagues (1) reported the upregulation of transferrin receptor (CD71) on rat mesenchymal stem cells (MSCs) labeled with superparamagnetic iron oxide (SPIO) nanoparticles. The authors should be commended for studying changes in the iron metabolism or storage to ensure safety of SPIO cell labeling. However, their results and conclusions cannot be generalized to all SPIO nanoparticles and transfection agents (TAs) used for cell labeling. nnThe authors report the upregulation of CD71 on late-passage (ie, passages 7–16) rat MSCs after labeling with ferucarbotran. Multiple passages of human and mouse MSCs are prone to genetic instability with consequent malignant transformation (2,3). Later passage (ie, passages >5) is not biologically relevant since human MSCs become senescent after 20–40 population doublings in culture (4). Human MSCs are positive for the transferrin receptor (5,6), however the authors showed no CD71 expression in control rat MSCs (see figure 3 of their article). Therefore, the upregulation of transferrin receptor in the ferucarbotran-labeled rat MSCs is not clinically relevant. Ferumoxides–protamine sulfate labeled human MSCs have an expected transient decrease in CD71 messenger RNA and protein levels when compared to unlabeled cells (6).