Belnuc edition:15 location:Luxembourg date:7-9 May 2011
Objectives: Stem cells have gained great interest in the field of regenerative medicine due to their extended differentiation capacity. For the development of these therapeutic strategies, more knowledge on the in vivo fate of these cells has to be acquired. Therefore, stem cells can be labeled with radioactive tracer molecules, such as 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG); a positron emitting glucose-analogue which is taken up and metabolically trapped by the cells. The aim of this study is to optimize the radioactive labeling of mesenchymal stem cells (MSCs) and multipotent adult progenitor cells (MAPCs) in vitro with 18F-FDG, and to investigate the radiotoxic effects of this labeling procedure.
Material and methods: Mouse MSCs and rat MAPCs were used. 18F-FDG uptake kinetics and tracer retention following labeling were determined. Furthermore, cell viability after labeling was evaluated using alamar blue and ultrastructural properties were examined with transmission electron microscopy (TEM). Additionally, mice were injected with 18F-FDG-prelabeled MSCs and MAPCs, and stem cell biodistribution was investigated using a µPET scanner.
Results: The optimal incubation period for 18F-FDG uptake was assessed at 60 minutes by labeling kinetics experiments. Also, an early significant tracer washout could be observed, reaching a plateau afterwards. Cell viability after labeling did not show any major differences. TEM only demonstrated toxic effects after labeling with 18F-FDG for 180 minutes. In addition, in vivo µPET experiments with radiolabeled MAPCs and MSCs in mice showed a predominant accumulation of the tracer in the lungs, corroborating the intracellular localization of the tracer.
Conclusions: MSCs and MAPCs can be successfully labeled for molecular imaging purposes with 18F-FDG. Furthermore, cell viability and ultrastructure are not severely affected by cell labeling up to 120 minutes. In vivo µPET studies confirmed the intracellular location of the tracer, and the possibility of imaging injected prelabeled stem cell types in vivo.