title: Tracking the fate of stem cell implants with fluorine-19 MRI.
abstract: BACKGROUND
  In this study we used cellular magnetic resonance imaging (MRI) to detect mesenchymal stem cells (MSC) labeled with a Fluorine-19 (19F) agent. 19F-MRI offers unambiguous detection and in vivo quantification of labeled cells.
  
  
  METHODS
  We investigated two common stem cell transplant mouse models: an immune competent, syngeneic transplant model and an immune compromised, xenograft transplant model. 19F labelled stem cells were implanted intramuscularly into the hindlimb of healthy mice. The transplant was then monitored for up to 17 days using 19F-MRI, after which the tissue was excised for fluorescence microscopy and immunohistochemisty.
  
  
  RESULTS
  Immediately following transplantation, 19F-MRI quantification correlated very well with the expected cell number in both models. The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model. By endpoint, only 2/7 syngeneic mice had any detectable 19F signal. In the xenograft model, all mice had detectable signal at endpoint. Fluorescence microscopy and immunohistochemistry were used to show that the 19F signal was related to the presence of bystander labeled macrophages, and not original MSC.
  
  
  CONCLUSIONS
  Our results show that 19F-MRI is an excellent tool for verifying the delivery of therapeutic cells early after transplantation. However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, University of Western Ontario, London, ON, Canada.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Gaudet
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada.
authors.forename: Emeline J
authors.initials: EJ
authors.lastname: Ribot
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Gilbert
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, University of Western Ontario, London, ON, Canada.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Foster
mesh_terms: D000818:Animals; D058948:Cell Tracking / Q000379:methods*; D004195:Disease Models, Animal; D005462:Fluorine Radioisotopes / Q000008:administration & dosage*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence / Q000379:methods
chemical_list: D005462:Fluorine Radioisotopes