Guanshu Liu^1,2, Chetan Bettegowda³, Assaf A. Gilad^2,4, Michael T McMahon^1,2, Kannie W.Y. Chan^2,4, Kenneth W. Kinzler³, Bert Vogelstein³, Jeff WM Bulte^2,4, Shibin Zhou³, and Peter CM van Zijl^1,2
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.

Valeria Righi^1,2, Melissa Starkey³, Laurence G. Rahme³, Ronald G. Tompkins⁴, and Aria A. Tzika^1,2
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.

Inema Orukari^1,2, Mike Gorelik^2,3, Joann Wang^2,3, Shashikala Galpoththawela^1,2, Heechul Kim^1,2, Douglas A Kerr⁴, Michael Levy⁵, Andre Levchenko³, Jeff Bulte^1,2, and Piotr Walczak^1,2
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.

Bistra Iordanova^1,2, and Eric T Ahrens^1,2
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.

David Z Balla¹, Sven Gottschalk¹, G Shajan¹, Sandra Ueberberg², Stephan Schneider², Rolf Pohmann¹, and Jörn Engelmann^1
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.

Daniel Jirak¹, Frantisek Saudek², Monika Dezortova¹, Peter Girman², Vit Herynek¹, Jan Kriz², Zuzana Berkova², Klara Zacharovova², Jan Peregrin¹, and Milan Hajek^1
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.

Benjamin Bay Bartelle¹, Kamila Urzula Szulc², and Daniel H Turnbull^2,3
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.

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 Gallez^1
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.

Yu-Xiang Ye¹, Thomas Christian Basse-Luesebrink¹, Paula Arias², Thomas Kampf¹, Vladimir Kocoski³, Elisabeth Bauer², Kai Hu², Valerie Jahns⁴, Peter M Jakob^1,5, Karl-Heinz Hiller^1,5, Roland Jahns², and Wolfgang Rudolf Bauer^2
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.

Anna Naumova^1,2, Vasily Yarnykh^1,2, Hans Reinecke^2,3, Charles Murry^2,3, and Chun Yuan^1,2
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.