title: In vivo mesenchymal stem cell tracking with PET using the dopamine type 2 receptor and 18F-fallypride.
abstract: Human mesenchymal stem cells (hMSCs) represent a promising treatment approach for tissue repair and regeneration. However, little is known about the underlying mechanisms and the fate of the transplanted cells. The objective of the presented work was to determine the feasibility of PET imaging and in vivo monitoring after transplantation of dopamine type 2 receptor-expressing cells.
  
  
  METHODS
  An hMSC line constitutively expressing a mutant of the dopamine type 2 receptor (D2R80A) was generated by lentiviral gene transfer. D2R80A messenger RNA expression was confirmed by reverse transcriptase-polymerase chain reaction. Localization of the transmembrane protein was analyzed by confocal fluorescence microscopy. The stem cell character of transduced hMSCs was investigated by adipogenic and osteogenic differentiation. Migration capacity was assessed by scratch assays in time-lapse imaging. In vitro specific binding of ligands was tested by fluorescence-activated cell sorting analysis and by radioligand assay using (18)F-fallypride. Imaging of D2R80A overexpressing hMSC transplanted into athymic rats was performed by PET using (18)F-fallypride.
  
  
  RESULTS
  hMSCs showed long-term overexpression of D2R80A. As expected, the fluorescence signal suggested the primary localization of the protein in the membrane of the transduced cells. hMSC and D2R80A retained their stem cell character demonstrated by their osteogenic and adipogenic differentiation capacity and their proliferation and migration behavior. For in vitro hMSCs, at least 90% expressed the D2R80A transgene and hMSC-D2R80A showed specific binding of (18)F-fallypride. In vivo, a specific signal was detected at the transplantation site up to 7 d by PET.
  
  
  CONCLUSIONS
  The mutant of the dopamine type 2 receptor (D2R80A) is a potent reporter to detect hMSCs by PET in vivo.
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and.
authors.forename: Veronika
authors.initials: V
authors.lastname: Schönitzer
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and florian.haasters@med.uni-muenchen.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Haasters
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Käsbauer
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and.
authors.forename: Veronika
authors.initials: V
authors.lastname: Ulrich
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Erik
authors.initials: E
authors.lastname: Mille
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Franz Josef
authors.initials: FJ
authors.lastname: Gildehaus
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Janette
authors.initials: J
authors.lastname: Carlsen
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Manuela
authors.initials: M
authors.lastname: Pape
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Roswitha
authors.initials: R
authors.lastname: Beck
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Delker
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Böning
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and.
authors.forename: Wolf
authors.initials: W
authors.lastname: Mutschler
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Böcker
authors.affiliation: Department of Surgery, Experimental Surgery, and Regenerative Medicine, Ludwig-Maximilians-University Munich, Munich, Germany; and.
authors.forename: Matthias
authors.initials: M
authors.lastname: Schieker
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Bartenstein
mesh_terms: D000818:Animals; D001549:Benzamides; D058948:Cell Tracking; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000000981:diagnostic imaging* / Q000378:metabolism; D009154:Mutation; D049268:Positron-Emission Tomography; D011759:Pyrrolidines; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D019076:Transgenes / Q000235:genetics
chemical_list: D001549:Benzamides; C581293:DRD2 protein, human; C094948:N-((1-allyl-2-pyrrolidinyl)methyl)-5-(3-fluoropropyl)-2,3-dimethoxybenzamide; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2
keywords: cell tracking; dopamine 2 receptor; in vivo imaging; mesenchymal stem cells; positron emission tomography