Published ahead of print on February 13, 2008
doi: 10.3174/ajnr.A0863
Noninvasive Molecular Neuroimaging Using Reporter Genes: Part II, Experimental, Current, and Future Applications
T.F. Massouda,b,
A. Singha and
S.S. Gambhirb,c
a Department of Radiology, Section of Neuroradiology, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK
b Molecular Imaging Program at Stanford, Bio-X Program, Stanford University School of Medicine, Stanford, Calif
c Departments of Radiology and Bioengineering, Bio-X Program, Stanford University School of Medicine, Stanford, Calif
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Fig 1. The localization of the bioluminescence imaging signal intensity reflects the anatomic site of injection. A, Bioluminescence imaging scans 14 days after injection of 293T cells transduced with a lentiviral construct encoding enhanced green fluorescent protein (EGFP) and Fluc separated by the internal ribosome entry site (I) of the encephalomyocarditis virus (LV-EGFP-I-Fluc) showing a focus that is located above the injection site: caudal to the eyes and on the left side of the head for the left striatum (L Str), caudal to the eyes and on the right side for the right striatum (R Str), between the eyes for the olfactory bulb (OB), near the caudal edge of the skull for the substantia nigra (SN), and intermediate between R Str and SN for the globus pallidus (GP). These sites correspond to the expected locations on the basis of the injection coordinates. B, Ex vivo bioluminescence images of 1-mm-thick coronal sections show the localization of the signal intensity at the site of injection. The sections are numbered in the anteroposterior direction from the bulbus olfactorius1 to the cerebellum.8 C, Immunohistochemistry for EGFP confirms the site of injection. (Reprinted by permission from Macmillan Publishers: Deroose et al. Mol. Therapy 2006;14:423–31, copyright 2006).
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Fig 2. Time course of bioluminescence imaging (BLI) signal intensity after lentiviral (LV) transduction of mouse brain. A, Long-term evolution of the BLI signal intensity in a group of mice (n = 10) injected with 17-ng p24 of LV-Fluc and in a group injected with 8.4-ng p24 control vector (LV-enhanced green fluorescent protein [EGFP], n = 4). After a peak at days 8 to 14, the signal intensity declines during the first month to 16% of the maximum value at day 37 and then remains constant at 17.5 ± 2.3% of the maximum value from days 42 to 365. A linear regression line is drawn from days 37 to 365 (R2 = 0.027) for LV-Fluc and for all time points for LV-EGFP (R2 = 0.041). B, BLI of a representative animal shows an initial rise in signal intensity at week (W) 1 followed by a decrease and thereafter a stabilization of the signal intensity. The control animal shown represents the highest signal intensity seen in a control animal. GFP indicates green fluorescent protein; D, day; p, photons. (Reprinted by permission from Macmillan Publishers: Deroose et al. Mol. Therapy 2006;14:423–31, copyright 2006)
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Fig 3. Brain injury results in activation of TGF-β responsive genes and the Smad-binding element (SBE)-firefly luciferase (luc) reporter. Two SBE-luc mice with similar basal levels of bioluminescence were lesioned with a needle stab to the right hemisphere or were left untreated (control), and bioluminescence was recorded 1 hour later. To highlight the increase in signal intensity in the lesioned mouse, the color scale was adjusted to leave the basal Fluc expression in the control mouse uncolored (<200 photons[p]/s/mm2/sr). (Copyright 2005, The American Association of Immunologists)
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Fig 4. Simultaneous in vivo biphotonic monitoring of pneumococcal meningitis and the accompanying neuronal injury in live transgenic mice. Streptococcus pneumoniae engineered for bioluminescence (lux) was used for direct visualization of disease progression. Host response was monitored in transgenic mice containing an inducible firefly luciferase (Fluc) reporter gene under transcriptional control of the mouse glial fibrillary acidic protein (GFAP) promoter. On the basis of the different spectra of light emission and substrate requirements for Fluc and luc, it is possible to monitor separately the 2 reporters by using a highly sensitive in vivo imaging system. In vivo (A and D) and ex vivo (B, C, E, and F) images of brains from transgenic mice with meningitis were obtained at 19 hours postinfection. A, B, and C show lux imaging and D, E, and F show Fluc imaging. Dorsal and ventral views of an ex vivo brain show the bacterial and GFAP signals individually. Much of the bacterial signal intensity comes from discrete patches, whereas GFAP is induced in the entire brain and there are different intensities of the bioluminescence signal intensity in certain regions of the brain. Note the strong bacterial signal intensity immediately surrounding the inoculation site in the anterior right frontal lobe. (Reprinted by permission from the American Society for Microbiology)
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