title: Optimization of multimodal imaging of mesenchymal stem cells using the human sodium iodide symporter for PET and Cerenkov luminescence imaging.
abstract: OBJECTIVE
  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.
authors.affiliation: Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
authors.forename: Esther
authors.initials: E
authors.lastname: Wolfs
authors.affiliation: Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
authors.forename: Bryan
authors.initials: B
authors.lastname: Holvoet
authors.affiliation: Laboratory of Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium, and Leuven Viral Vector Core, KU Leuven, Leuven, Belgium.
authors.forename: Rik
authors.initials: R
authors.lastname: Gijsbers
authors.affiliation: Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
authors.forename: Cindy
authors.initials: C
authors.lastname: Casteels
authors.affiliation: Skeletal Biology and Engineering Research Center, Department of development and regeneration, KU Leuven, Leuven, Belgium.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Roberts
authors.affiliation: Lab of Histology, Department of morphology, Biomedical Research Institute, Universiteit Hasselt, Hasselt, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Struys
authors.affiliation: Laboratory of Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium, and Leuven Viral Vector Core, KU Leuven, Leuven, Belgium.
authors.forename: Michael
authors.initials: M
authors.lastname: Maris
authors.affiliation: Laboratory of Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium, and Leuven Viral Vector Core, KU Leuven, Leuven, Belgium.
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Ibrahimi
authors.affiliation: Laboratory of Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium, and Leuven Viral Vector Core, KU Leuven, Leuven, Belgium.
authors.forename: Zeger
authors.initials: Z
authors.lastname: Debyser
authors.affiliation: Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Van Laere
authors.affiliation: Stem Cell Institute Leuven, Department of development and regeneration, KU Leuven, Leuven, Belgium.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Verfaillie
authors.affiliation: Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Deroose
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D017930:Genes, Reporter / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D007457:Iodine Radioisotopes; D016086:Lentivirus / Q000235:genetics; D049449:Luminescence; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D064847:Multimodal Imaging / Q000379:methods*; D061848:Optical Imaging / Q000379:methods*; D020648:Peptide Elongation Factor 1 / Q000235:genetics; D049268:Positron-Emission Tomography / Q000379:methods*; D011691:Puromycin / Q000494:pharmacology; D027981:Symporters / Q000235:genetics*; D000099209:Sodium-Iodide Symporters
chemical_list: D007457:Iodine Radioisotopes; D020648:Peptide Elongation Factor 1; D011691:Puromycin; D027981:Symporters; D000099209:Sodium-Iodide Symporters
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