Imaging
Figure 18 0h 3h 6h
providing quantitative 3D imaging of biology in context. The 3D image is captured based on tran- sillumination of test animal from laser light excita- tion, using either two lasers (FMT1500 with exci- tation at 635 and 745nm) or four lasers (FMT2500LX with excitation at 635, 670, 745 and 790nm). Because photons in the near infrared (NIR) penetrate from 7cm to 14cm in vivo, PerkinElmer has designed a broad portfolio of imaging agents labelled in the red and NIR for use on the system. The emission signals are captured by a cooled-CCD and the data is processed using TrueQuant™ software. The algorithm, which processes 10,000 to 100,000 image data points from each scan, takes into account tissue hetero- geneity in reconstruction of the 3D image. FMT data can be co-registered with other imaging modes (MR, CT and PET) based on the fiduciary marks on the imaging cassette that holds the test animal. The combined data output extends the util- ity of the functional data obtained on the FMT. Newly added this year, the Multispecies Imaging Module (MSIM) enables the study of disease mod- els in larger animals (up to 450g). Scans of mice and rats can be done sequentially without effect on the workflow (Figure 17).
Promega (
www.promega.com), a technical leader in luciferase-based solutions for the life sciences, has continued to develop technologies for assays that can be transferred from the microplate well to the whole animal. Although the firefly luciferase pro- substrate approach has applications for in vivo pre- clinical imaging, a more recent approach involves the use of an engineered form of luciferase designed to act as a cellular biosensor. Commercialised under the trade name ‘GloSensor’, the biosensor technol- ogy has already been used to demonstrate kinetic readouts for proteins (ie GPCRs) that signal
Drug Discovery World Summer 2011 20h 4d 5d
through the second messengers, cAMP and cGMP. The technology, in brief, relies on multiple forms of genetically engineered luciferases that are inactive in the absence of analytes of interest (ie cAMP, cGMP, protease etc). In the presence of the specific analyte, the enzyme undergoes a conformational change resulting in an active molecular state and luminescent readout that is proportional to the amount of analyte present. To monitor apoptosis through the activity of caspase-3/7, Promega insert- ed a protease recognition sequence for caspase-3 into the biosensor such that in the presence of this apoptotic enzyme, the cognate protease recognition sequence is cleaved resulting in an active biosensor. Promega developed proof of concept experiments in cell-based approaches in-house and then collaborat- ed with researchers at the University of Michigan on the detection of apoptosis in vivo with the biosensor technology in murine cancer models. At the 2011 AACR Meeting, work was presented that demonstrated the use of the bioluminescent biosen- sor for imaging Caspase-3 activation in cancer cell lines and mouse models, as well as the evaluation of its usefulness for preclinical treatment efficacy stud- ies2. It also demonstrated the biosensor to be extremely sensitive in vivo by generating two mouse xenograft models. TRAIL-induced caspase 3 of glioma xenografted animals resulted in biolumines- cence activation of 100-fold in just six hours post- treatment. This study highlighted the usefulness of GloSensor for imaging cell death in real time and in kinetic mode in their preclinical mouse models (Figure 18).
Siemens Preclinical (
www.siemens.com/preclinical) offers its Inveon™ PET, SPECT and CT animal imaging systems in various configurations ranging from standalone PET and CT systems to multi- modal PET/CT, SPECT/CT and PET/SPECT/CT
67
Demonstration of an optimised bioluminescent biosensor for the detection of cell death in living animals. Representative images taken at indicated time points (0 hours through day 5, left to right) of intratibial implanted 1833 reporter cells. TRAIL treatment (8mg/kg) resulted in a 100-200 fold induction of bioluminescence activity that correlated with cell death as demonstrated by increased cleavage of Caspase-3. The high signal to noise and dynamic range of reporter activity provides a sensitive and quantitative surrogate for the evaluation of experimental therapeutics
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92