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PURPOSE: The use of stably integrated reporter gene imaging provides a manner to monitor the in vivo fate of engrafted cells over time in a non-invasive manner. Here, we optimized multimodal imaging (small-animal PET, Cerenkov luminescence imaging (CLI) and bioluminescence imaging (BLI)) of mesenchymal stem cells (MSCs), by means of the human sodium iodide symporter (hNIS) and firefly luciferase (Fluc) as reporters. METHODS: First, two multicistronic lentiviral vectors (LV) were generated for multimodal imaging: BLI, 124I PET/SPECT and CLI. Expression of the imaging reporter genes was validated in vitro using 99mTcO4- radioligand uptake experiments and BLI. Uptake kinetics, specificity and tracer elution were determined as well as the effect of the transduction process on the cell's differentiation capacity. MSCs expressing the LV were injected intravenously or subcutaneously and imaged using small-animal PET, CLI and BLI. RESULTS: The expression of both imaging reporter genes was functional and specific. An elution of 99mTcO4- from the cells was observed, with 31% retention after 3 h. After labeling cells with 124I in vitro, a significantly higher CLI signal was noted in hNIS expressing murine MSCs. Furthermore, it was possible to visualize cells injected intravenously using BLI or subcutaneously in mice, using 124I small-animal PET, CLI and BLI. CONCLUSIONS: This study identifies hNIS as a suitable reporter gene for molecular imaging with PET and CLI, as confirmed with BLI through the expression of Fluc. It supports the potential for a wider application of hNIS reporter gene imaging and future clinical applications. ispartof: PLOS ONE vol:9 issue:4 ispartof: location:United States status: published

Human dental pulp stem cells (HDPSC’s) is a term used for the remaining mesenchymal stem cell population in adult teeth. It has already been described that these cells exhibit odontogenic capacities when these cells are explanted into immunocompromised mice. They create a dentin-pulp like complex and in this way their use in tissue engineering and tooth regeneration seems very promising. However, there is still a lack of specific markers to identify this cell type. In this study, we investigated the immunoreactivity of HDPSC’s for metallothionein (MT), a Cystein-rich, low molecular weight protein. MT has the capacity to bind both physiological (Zn, Cu, Se,...) and xenobiotic (Cd, Hg, Ag,...) heavy metals through the thiol group of its cysteine residues. Furthermore, the immunoreactivity fot MT was tested in human pulp tissue and human bone-marrow derived mesenchymal stem cells.