Cell Tracking & Gene Expression
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Thursday May 12th
Room 520B-F  16:00 - 18:00 Moderators: Eric Ahrens and Piotr Walczak

16:00 661.   CEST MRI for monitoring bacteriolytic tumor therapy 
Guanshu Liu1,2, Chetan Bettegowda3, Assaf A. Gilad2,4, Michael T McMahon1,2, Kannie W.Y. Chan2,4, Kenneth W. Kinzler3, Bert Vogelstein3, Jeff WM Bulte2,4, Shibin Zhou3, and Peter CM van Zijl1,2
1F.M. Kirby center, Kennedy Krieger Institute, Baltimore, MD, United States, 2Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 3Ludwig Center, Howard Hughes Medical Institute and Sidney Kimmel Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, United States,4Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Bacteriolytic therapy has recently emerged as a promising approach for cancer therapy, in which anaerobic bacteria are utilized to selectively destroy the hypoxic cores of solid tumors. To facilitate its clinical translation, we sought to develop a non-invasive MR imaging method that is capable of monitoring infection with Clostridium novyi-NT. An inherent Chemical Exchange Saturation Transfer (CEST) signal at 2.6 ppm from the water proton signal was found in cultures of this bacterium in vitro. Using this signal, we were able to detect the germination of the anaerobic bacteria in vivo.

16:12 662.   Magnetization Transfer Contrast MRI detects Pseudomonas aeruginosa bacterial infection bacterial infection a mouse burn model 
Valeria Righi1,2, Melissa Starkey3, Laurence G. Rahme3, Ronald G. Tompkins4, and Aria A. Tzika1,2
1Department of Surgery, NMR Surgical Laboratory, MGH and Shriners Burn Institute, Harvard Medical School, Boston, MA, United States, 2Department of Radiology, Athinoula A. Martinos Center of Biomedical Imaging, Boston, MA, United States, 3Department of Surgery, Molecular Surgery Laboratory, MGH and Shriners Burn Institute, Harvard Medical School, Boston, MA, United States, 4Department of Surgery, MGH and Shriners Burn Institute, Harvard Medical School, Boston, MA, United States

We report an in vivo study of GFP-tagged Magnetization Transfer Contrast (MTC) MRI in burn mouse infected with Pseudomonas aeruginosa. The goal of this methodology is to visualize bacterial infections in vivo in real time, and to study the impact of novel therapeutics on bacterial proliferation and viability within the host system. Furthermore, the expression of relevant bacterial genes can be monitored during infection by expressing GFP under the control of appropriate bacterial promoters. This approach provides a flexible, non-invasive in vivo molecular MRI imaging strategy that is dependent upon the presence and concentration of the GFP reporter.

16:24 663.   High-Efficiency Targeting of Glial Precursor Cells to Inflammatory Brain Lesions Using the VLA4-VCAM1 Cell Adhesion Pathway: Real-Time MR Monitoring of Instant Cell Engraftment 
Inema Orukari1,2, Mike Gorelik2,3, Joann Wang2,3, Shashikala Galpoththawela1,2, Heechul Kim1,2, Douglas A Kerr4, Michael Levy5, Andre Levchenko3, Jeff Bulte1,2, and Piotr Walczak1,2
1Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University, Baltimore, Maryland, United States, 2Cellular Imaging Section, Vascular Biology Program, Institute for Cell Engineerin, Johns Hopkins University, Baltimore, Maryland, United States, 3Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 4Biogen-IDEC, Cambridge, Massachusetts, United States, 5Neurology, Johns Hopkins University, Baltimore, Maryland, United States

Stem cells offer hope for treatment of incurable neurological diseases. Efficient systemic delivery of stem cells to brain lesions is an important but still not achieved goal. We evaluated a novel intra-arterial method for targeted stem cell delivery based on genetic engineering of cells to express VLA-4 while performing real-time in vivo MRI monitoring of cell engraftment. Using a microfluidics cell adhesion assay, we demonstrated that VLA-4+ cells preferentially adhered to activated VCAM1+ endothelium. Using a rat model, SPIO-labeled, VLA-4+ cells efficiently homed to activated brain endothelium with MRI being an excellent method to monitor this process in real-time.

16:36 664.   In vivo magnetic resonance imaging of ferritin-based reporter visualizes native neuroblast migration 
Bistra Iordanova1,2, and Eric T Ahrens1,2
1Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States, 2Pittsburgh NMR Center for Biomedical Research, Pittsburgh, PA, United States

Adult neurogenesis research in mammals presents a challenge as most stem cells and progenitors are located deep in opaque brain tissues. Here, we report the application of ferritin-based MRI reporter to label murine subventricular zone progenitors and visualize in vivo the endogenous neuroblast migration towards the olfactory bulb. This MRI reporter gene platform can facilitate the study of native or transplanted stem cell migration and associated neurogenic or therapeutic molecular events in live animals.

16:48 665.   In vivo visualization of pancreatic islets in the mouse 
David Z Balla1, Sven Gottschalk1, G Shajan1, Sandra Ueberberg2, Stephan Schneider2, Rolf Pohmann1, and Jörn Engelmann1
1High-Field MR Center, Max Planck Institute for biological cybernetics, Tübingen, Germany, 2Universitätsklinikum Bergmannsheil, Ruhr-Universität Bochum, Bochum, Germany

Detection of single pancreatic islets has many applications in diabetes research, but can be achieved in vivo with proton MRI only after transplantation of ex vivo labeled islets. Recently, successful visualization of islets in the excised mouse pancreas at 16.4T following i.v. injection of a novel beta-cell specific paramagnetic contrast agent was reported. Here we present the methodical optimization for in vivo experiments. Signal efficient 2D acquisition methods were considered. Best results were obtained with a two slice navigator based sequence. Single islets are visualized for the first time in vivo in mice after i.v. administration of a labeling agent.

17:00 666.   Monitoring of transplanted pancreatic islets in humans by MRI 
Daniel Jirak1, Frantisek Saudek2, Monika Dezortova1, Peter Girman2, Vit Herynek1, Jan Kriz2, Zuzana Berkova2, Klara Zacharovova2, Jan Peregrin1, and Milan Hajek1
1Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic, 2Diabetes Center, Institute for Clinical and Experimental Medicine, Prague, Czech Republic

We tracked iron-labeled pancreatic islets in type-1 diabetic recipients and quantified the islet loss in liver tissue by MR imaging during 6 months after transplantation. Hypointense islet spots and their area in the liver were counted and outlined manually. Function of transplanted islets was confirmed by C-peptide production. A dramatic loss of hypointense spots occurred in the 1st week following the transplantation. Then the number of spots and their area stabilized. Our data suggest that post-transplant MR monitoring might be of importance for assessment of the islet fate following clinical transplantation.

17:12 667.   Divalent Metal Transporter, DMT1: A Novel MRI Reporter 
Benjamin Bay Bartelle1, Kamila Urzula Szulc2, and Daniel H Turnbull2,3
1Structural Biology, Skirball Institute for Biomolecular Medicine, New York, NY, United States, 2Skirball Institute of Biomolecular Medicine, 3Radiology, New Yor University School of Medicine

Here we present a novel reporter gene which functions in concert with Mn enhanded MRI. Based on an observed correlation between DMT1 expression and endogenous Mn enhanced contrast, we characterized the protein’s effect on T1 in cells using saturation recovery based relaxometry and quantitative expression assays. We went on to ectopicly express DMT1 in the brain of a neonate mouse and image gene expression in vivo using standard MEMRI methods. These early experiments demonstrate DMT1’s robust potential as a reporter of gene expression for MRI.

17:24 668.   Electron Paramagnetic Resonance as a new sensitive tool to assess the iron content in cells and tissues for MRI cell labeling studies 
Pierre Danhier1, Geraldine Depraeter1, Sebastien Boutry2, Isabelle Mahieu2, Robert N Muller2, Pierre Sonveaux3, Caroline Bouzin3, Olivier Feron3, Philippe Leveque1, Julie Magat1, Benedicte Jordan1, and Bernard Gallez1
1Louvain Drug Research Institute, Biomedical Magnetic Resonance Research Group, University of Louvain, Brussels, Belgium, 2University of Mons, Mons, Belgium, 3Institute of Experimental and Clinical Research, University of Louvain, Brussels, Belgium

We propose here to implement Electron Paramagnetic Resonance (EPR) as a very sensitive method to quantify iron oxide concentration (in cells and tissues). Iron oxide particles exhibit an EPR spectrum, which directly reflects the number of iron oxide particles in a sample. In order to compare EPR with existing methods (Perl’s Prussian blue reaction, and fluorimetry), we labeled tumor cells (Melanoma B16F10-luc, fibrosarcoma KHT-luc) and fibroblasts (3T3) with fluorescent iron oxide particles, and defined the limit of detection of the different techniques. EPR is a fast, easy, and highly sensitive method (compared to other methods) to quantify iron oxide content after magnetic labelling.

17:36 669.   In vivo monitoring of anti-inflammatory Atorvastatin-effects in reperfused myocardial infarction using integrated cellular fluorine 19F-MRI and 1H-cardiac MRI  -permission withheld
Yu-Xiang Ye1, Thomas Christian Basse-Luesebrink1, Paula Arias2, Thomas Kampf1, Vladimir Kocoski3, Elisabeth Bauer2, Kai Hu2, Valerie Jahns4, Peter M Jakob1,5, Karl-Heinz Hiller1,5, Roland Jahns2, and Wolfgang Rudolf Bauer2
1Department for Experimental Physics 5, University of Würzburg, Würzburg, Bavaria, Germany, 2Department of Internal Medicine I, University Hospital Würzburg,3Institute for Virology & Immunobiology, 4Institute for Pharmacology and Toxicology, University of Würzburg, 5MRB Research Center, Magnetic Resonance Bavaria

In acute myocardial infarction (MI) blood monocytes play a key role in wound healing. Non-invasive imaging strategies are required to better understand and translate this knowledge into clinics. We investigated the value of integrating 19F-MRI cell trafficking with 1H-cardiac MRI to monitor an anti-inflammatory therapeutic approach of Atorgastatin in a MI rat model. The combined 19F/1H MRI found reduced myocardial monocyte infiltration and revealed a possible mechanism of action by Atorvastatin. Our platform provides a novel view on tissue injury and its innate immune response after ischemia-reperfusion, and thus contribute to gain new insights of anti-inflammatory therapy in MI.

17:48 670.   In vivo MRI Signal Features of Transgenic Grafts Overexpressing Ferritin in the Murine Myocardial Infarction Model 
Anna Naumova1,2, Vasily Yarnykh1,2, Hans Reinecke2,3, Charles Murry2,3, and Chun Yuan1,2
1Radiology, University of Washington, Seattle, WA, United States, 2Center for Cardiovascular Biology, University of Washington, Seattle, WA, United States, 3Pathology, University of Washington, Seattle, WA, United States

This study showed possibility of non-invasive visualization and quantification of transgenic C2C12 grafts overexpressing MRI gene reporter ferritin in the infarcted mouse heart. T2*-weighted gradient echo sequence was most sensitive for imaging of ferritin-tagged grafts capturing about 30% change in MRI signal intensity. Unlabeled wild-type C2C12 cells transplanted to the mouse heart did not change MRI signal intensity in T2*-weighted images. The important advantage of this approach is that the gene reporter divides with each round of cell division retaining a desired MRI contrast over the entire volume of growing grafts.