title: Longitudinal monitoring of stem cell grafts in vivo using magnetic resonance imaging with inducible maga as a genetic reporter.
abstract: OBJECTIVE
  The ability to longitudinally monitor cell grafts and assess their condition is critical for the clinical translation of stem cell therapy in regenerative medicine. Developing an inducible genetic magnetic resonance imaging (MRI) reporter will enable non-invasive and longitudinal monitoring of stem cell grafts in vivo.
  
  
  METHODS
  MagA, a bacterial gene involved in the formation of iron oxide nanocrystals, was genetically modified for in vivo monitoring of cell grafts by MRI. Inducible expression of MagA was regulated by a Tet-On (Tet) switch. A mouse embryonic stem cell-line carrying Tet-MagA (mESC-MagA) was established by lentivirus transduction. The impact of expressing MagA in mESCs was evaluated via proliferation assay, cytotoxicity assay, teratoma formation, MRI, and inductively coupled plasma atomic emission spectroscopy (ICP-OES). Mice were grafted with mESCs with and without MagA (mESC-MagA and mESC-WT). The condition of cell grafts with induced "ON" and non-induced "OFF" expression of MagA was longitudinally monitored in vivo using a 7T MRI scanner. After imaging, whole brain samples were harvested for histological assessment.
  
  
  RESULTS
  Expression of MagA in mESCs resulted in significant changes in the transverse relaxation rate (R2 or 1/T2) and susceptibility weighted MRI contrast. The pluripotency of mESCs carrying MagA was not affected in vitro or in vivo. Intracranial mESC-MagA grafts generated sufficient T2 and susceptibility weighted contrast at 7T. The mESC-MagA grafts can be monitored by MRI longitudinally upon induced expression of MagA by administering doxycycline (Dox) via diet.
  
  
  CONCLUSIONS
  Our results demonstrate MagA could be used to monitor cell grafts noninvasively, longitudinally, and repetitively, enabling the assessment of cell graft conditions in vivo.
authors.affiliation: 1. Genetics and Molecular Biology Program, Emory University, Atlanta, GA, USA; ; 2. Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA; ; 3. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: In K
authors.initials: IK
authors.lastname: Cho
authors.affiliation: 3. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: Sean P
authors.initials: SP
authors.lastname: Moran
authors.affiliation: 4. Yerkes Imaging Center, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: Ramesh
authors.initials: R
authors.lastname: Paudyal
authors.affiliation: 3. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: Karolina
authors.initials: K
authors.lastname: Piotrowska-Nitsche
authors.affiliation: 3. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: Pei-Hsun
authors.initials: PH
authors.lastname: Cheng
authors.affiliation: 4. Yerkes Imaging Center, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: 5. Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Mao
authors.affiliation: 1. Genetics and Molecular Biology Program, Emory University, Atlanta, GA, USA; ; 2. Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA; ; 3. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA;
authors.forename: Anthony W S
authors.initials: AW
authors.lastname: Chan
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D058948:Cell Tracking / Q000379:methods*; D053595:Embryonic Stem Cells / Q000502:physiology / Q000637:transplantation*; D015870:Gene Expression; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D008279:Magnetic Resonance Imaging; D057507:Mice, 129 Strain; D008819:Mice, Nude; D016513:Mice, SCID; D033581:Stem Cell Transplantation / Q000009:adverse effects; D013724:Teratoma / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins
keywords: MagA; Magnetic resonance imaging; cell tracking; inducible expression; intracranial graft.; longitudinal monitoring; regenerative medicine; reporter gene; stem cell