title: Imaging of mesenchymal stem cell transplant by bioluminescence and PET.
abstract: Dynamic measurements of infused stem cells generally require animal euthanasia for single-time-point determinations of engraftment. In this study, we used a triple-fusion reporter system for multimodal imaging to monitor human mesenchymal stem cell (hMSC) transplants.
  
  
  METHODS
  hMSCs were transduced with a triple-fusion reporter, fluc-mrfp-ttk (encoding firefly luciferase, monomeric red fluorescent protein, and truncated herpes simplex virus type 1 sr39 thymidine kinase) by use of a lentiviral vector. Transduced cells were assayed in vitro for the expression of each functional component of the triple-fusion reporter. Transduced and control hMSCs were compared for their potential to differentiate into bone, cartilage, and fat. hMSCs expressing the reporter were then loaded into porous, fibronectin-coated ceramic cubes and subcutaneously implanted into NOD-SCID mice along with cubes that were loaded with wild-type hMSCs and empty cubes. Mice were imaged repeatedly over 3 mo by bioluminescence imaging (BLI), and selected animals underwent CT and PET imaging.
  
  
  RESULTS
  Osteogenic, adipogenic, and chondrogenic potential assays revealed retained differentiation potentials between transduced and wild-type hMSCs. Signals from the cubes loaded with reporter-transduced hMSCs were visible by BLI over 3 mo. There was no signal from the empty or wild-type hMSC-loaded control cubes. PET data provided confirmation of the quantitative estimation of the number of cells at one spot (cube). Cubes were removed from some animals, and histologic evaluations showed bone formation in cubes loaded with either reporter-transduced or wild-type hMSCs, whereas empty controls were negative for bone formation.
  
  
  CONCLUSIONS
  The triple-fusion reporter approach resulted in a reliable method of labeling stem cells for investigation in small-animal models by use of both BLI and small-animal PET imaging. It has the potential for translation into future human studies with clinical PET.
authors.affiliation: Department of Nuclear Medicine/Radiology, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, Ohio 44106, USA.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Love
authors.forename: Fangjing
authors.initials: F
authors.lastname: Wang
authors.forename: James
authors.initials: J
authors.lastname: Dennis
authors.forename: Amad
authors.initials: A
authors.lastname: Awadallah
authors.forename: Nicolas
authors.initials: N
authors.lastname: Salem
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lin
authors.forename: Andrew
authors.initials: A
authors.lastname: Weisenberger
authors.forename: Stan
authors.initials: S
authors.lastname: Majewski
authors.forename: Stanton
authors.initials: S
authors.lastname: Gerson
authors.forename: Zhenghong
authors.initials: Z
authors.lastname: Lee
mesh_terms: D000818:Animals; D006801:Humans; D008163:Luminescent Measurements / Q000379:methods*; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000000981:diagnostic imaging* / Q000502:physiology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D049268:Positron-Emission Tomography / Q000379:methods*