Name: fluorescence-mediated tomography for the detection and quantification of macrophage-related murine intestinal inflammation
Uploaded: 2017-12-15T12:30:00
Description: Watch this Scientific Journal Video about Fluorescence-mediated Tomography for the Detection and Quantification of Macrophage-related Murine Intestinal Inflammation at JoVE.com

We thank Ms. Sonja Dufentester, Ms. Elke Weber, and Mrs. Klaudia Niepagenk&#228;mper for the excellent technical assistance.

All animal experiments were approved by the Landesamt f&#252;r Natur, Umwelt und Verbraucherschutz (LANUV) Nordrhein-Westfalen according to the German Animal Protection Law (Tierschutzgesetz).
1. Materials and Experimental Setup
<ol>
	<li>Animal care.
	<ol>
		<li>Use sex- and age-matched mice of any DSS-susceptible strain (e.g., C57BL/6) at 20-25 g bodyweight.</li>
		<li>Plan at least five or more mice per experimental group and house the mice according to local ani...

<ol>
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M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+5A+apolipoprotein+A-I+(apoA-I)+mimetic+peptide+ameliorates+experimental+colitis+by+regulating+monocyte+infiltration.">The 5A apolipoprotein A-I (apoA-I) mimetic peptide ameliorates experimental colitis by regulating monocyte infiltration.</a> Br J Pharmacol. 173 (18), 2780-2792 (2016).</li><li>Hansch, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+experimental+arthritis+with+near-infrared+fluorescence.">In vivo imaging of experimental arthritis with near-infrared fluorescence.</a> Arthritis Rheum. 50 (3), 961-967 (2004).</li><li>Bialkowska, A. B., Ghaleb, A. M., Nandan, M. O., Yang, V. 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J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vedolizumab+as+induction+and+maintenance+therapy+for+Crohn's+disease.">Vedolizumab as induction and maintenance therapy for Crohn's disease.</a> N Engl J Med. 369 (8), 711-721 (2013).</li><li>Vermeire, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Etrolizumab+as+induction+therapy+for+ulcerative+colitis:+a+randomised,+controlled,+phase+2+trial.">Etrolizumab as induction therapy for ulcerative colitis: a randomised, controlled, phase 2 trial.</a> Lancet. 384 (9940), 309-318 (2014).</li><li>Coskun, M., Vermeire, S., Nielsen, O. 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Although medical imaging techniques have evolved rapidly in recent years, we are still limited in our ability to detect inflammatory processes or tumors, as well as other diseases, in their earliest stages of development. However, this is crucial to understanding tumor growth, invasion, or metastases development and cellular processes in the development of inflammatory disorders and degenerative, cardiovascular and immunological diseases. While traditional imaging techniques rely on physical or physiological parameters, ...

Animal models are widely used in scientific research, and many non-invasive procedures exist to monitor disease activity and vitality, such as the quantification of body weight changes or the analysis of blood, urine, and feces. However, these are only indirect surrogate parameters that are also subject to inter-individual variability. They must frequently be complemented by post mortem analyses of tissue specimen, which prevents serial observation at repetitive time points and direct observation of physiological or pathological processes in vivo. Sophisticated small-animal imaging techniques have emerged, including cross sectional imaging, optical imaging, and endoscopy, which enables the direct visualization of these processes and also allows for repetitive analyses of the same animals1,2,3. Additionally, the possibility to repetitively monitor various states of disease in the same animal might decrease the number of animals needed, which might be desirable from an animal ethics point of view.
Several different optical imaging techniques exist for in vivo fluorescence imaging. Originally, confocal imaging was employed to study surface and subsurface fluorescent events4,5. Recently, however, tomographic systems that allow for quantitative three-dimensional tissue assessments have been developed6. This has been accomplished through the development of fluorescent probes that emit light in the near-infrared (NIR) spectrum, offering low absorption, sensitive detectors, and monochromatic light sources7. While traditional cross-sectioning imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound (US), rely mostly on physical parameters and visualize morphology, optical imaging can provide additional information on underlying molecular processes using endogenous or exogenous fluorescent probes8.
Advances in molecular biology have helped to facilitate the generation of smart and targeted fluorescent molecular probes for an increasing number of targets. For example, receptor-mediated uptake and distribution in a given target area can be visualized using carbocyanine derivative-labeled antibodies9. The abundance of available antibodies, which can be labeled to function as specific tracers in otherwise inaccessible areas of the body, provides unprecedented insights into molecular and cellular processes in models of tumorigenesis and neurodegenerative, cardiovascular, immunologic, and inflammatory diseases7.
In this study, we describe the use of fluorescence-mediated tomography in a murine model of colitis. Dextran sodium sulfate (DSS)-induced colitis is a standard chemically induced mouse model of intestinal inflammation that resembles inflammatory bowel disease (IBD)10. It is particularly useful to assess the contribution of the innate immune system to the development of gut inflammation11. Since the recruitment, activation, and infiltration of monocytes and macrophages represent crucial steps in the pathogenesis of IBD, visualization of their recruitment and the kinetics of infiltration are essential to monitoring, for example, the effect of potential therapeutic substances in a preclinical setting12. We describe the induction of DSS colitis and demonstrate the tomography-mediated characterization of macrophage infiltration into the gut mucosa using fluorescence molecular tomography for the specific visualization of the monocyte/macrophage marker F4/8013. Additionally, we illustrate auxiliary and supplemental procedures, such as antibody labelling; the experimental setup; and analysis and interpretation of the obtained images, in correlation with conventional readouts such as disease activity indices, flow cytometry and histological analysis, and immunohistochemistry. We discuss limitations of this technique and comparisons to other imaging modalities.

<table border="0" cellpadding="0" cellspacing="0" width="1601">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:469px;">Reagents</td>
			<td style="width:423px;"></td>
			<td style="width:320px;"></td>
			<td style="width:389px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Alfalfa-free diet</td>
			<td>Harlan Laboritories, Madison, USA</td>
			<td style="width:320px;">2014</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bepanthen eye ointment</td>
			<td style="width:423px;">Bayer, Leverkusen, Germany</td>
			<td style="width:320px;">80469764</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dextran sulphate sodium (DSS)</td>
			<td>TdB Consulatancy, Uppsala, Sweden</td>
			<td>DB001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Eosin</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">E 4382</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Ethylenediaminetetraacetic acid (EDTA)&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">E 9884</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Florene 100V/V</td>
			<td>Abbott, Wiesbaden, Germany</td>
			<td style="width:320px;">B506</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Haematoxylin&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">Sigma - Aldrich, Deisenhofen, Germany</td>
			<td style="width:320px;">HHS32-1L</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">O.C.T. Tissue Tek compound&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:423px;">Sakura, Zoeterwonde, Netherlands</td>
			<td style="width:320px;">4583</td>
			<td>fixative for histological analyses</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Phosphate buffered saline, PBS</td>
			<td style="width:423px;">Lonza, Verviers, Belgium</td>
			<td style="width:320px;">4629</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium Chloride 0,9%</td>
			<td>Braun, Melsungen, Germany</td>
			<td style="width:320px;">5/12211095/0411</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium bicarbonate powder</td>
			<td>Sigma Aldrich Deisenhofen, Germany</td>
			<td style="width:320px;">S5761</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Standard diet</td>
			<td>Altromin, Lage, Germany</td>
			<td style="width:320px;">1320</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tissue-Tek Cryomold</td>
			<td>Sakura, Leiden, Netherlands</td>
			<td style="width:320px;">4566</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Hemoccult (guaiac paper test)</td>
			<td>Beckmann Coulter, Germany</td>
			<td style="width:320px;">3060</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Biotin rat-anti-mouse anti-F4/80 antibody</td>
			<td>Serotec, Oxford, UK</td>
			<td style="width:320px;">MCA497B</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Biotin rat-anti-mouse anti-GR-1&#160;</td>
			<td>BD Pharmingen, Heidelberg Germany</td>
			<td>553125</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Streptavidin-Alexa546</td>
			<td>Molecular Probes, Darmstadt, Germany</td>
			<td style="width:320px;">S-11225</td>
			<td>excitation/emission maximum:&#160; 556/573nm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Anti-CD11b rat-anti-mouse antibody TC</td>
			<td>Calteg, Burlingame, USA</td>
			<td style="width:320px;">R2b06</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Purified anti-mouse F4/80 antibody</td>
			<td>BioLegend, London, UK</td>
			<td style="width:320px;">123102</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DAPI</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td style="width:320px;">D9542</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FITC-conjugated anti-Ly6C rat-anti-mouse antibody</td>
			<td>BD Pharmingen, Heidelberg, Germany</td>
			<td>553104</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FACS buffer</td>
			<td>BD Pharmingen, Heidelberg, Germany</td>
			<td style="width:320px;">342003</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Cy7 NHS Ester</td>
			<td>GE Healthcare&#160;Europe, Freiburg, Germany</td>
			<td style="width:320px;">PA17104</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">MPO ELISA</td>
			<td>Immundiagnostik AG, Bensheim, Germany</td>
			<td>K 6631B</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Cy5.5 labeled anti-mouse F4/80 antibody</td>
			<td>BioLegend, London, UK</td>
			<td>123127</td>
			<td>ready to use labelled Antibodies (alternative)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Anti-Mouse F4/80 Antigen PerCP-Cyanine5.5</td>
			<td>eBioscience, Waltham, USA</td>
			<td>45-4801-80</td>
			<td>ready to use labelled Antibodies (alternative)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DMSO (Dimethyl sulfoxide)</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>67-68-5</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Isoflurane</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>792632</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ethanol</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>64-17-5</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bovine Serum Albumins (BSA)</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>A4612</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tris Buffered Saline Solution (TBS)</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>SRE0032</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:469px;">Name</td>
			<td style="width:423px;">Company</td>
			<td style="width:320px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Equipment</td>
			<td></td>
			<td style="width:320px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FACS Calibur Flow Cytometry System</td>
			<td>BD Biosciences GmbH, Heidelberg, Germany</td>
			<td style="width:320px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FMT 2000 In Vivo Imaging System</td>
			<td>PerkinElmer Inc., Waltham, MA, USA</td>
			<td style="width:320px;">FMT2000</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">True Quant 3.1 Imaging Analysis Software</td>
			<td>PerkinElmer Inc., Waltham, MA, USA</td>
			<td style="width:320px;">included in FMT2000</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Leica DMLB Fluorescent Microscope</td>
			<td>Leica,&#160; 35578 Wetzlar, Germany&#160;</td>
			<td>DMLB</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bandelin Sonopuls HD 2070</td>
			<td>Bandelin, 12207 Berlin, Germany</td>
			<td style="width:320px;">HD 2070</td>
			<td>ultrasonic homogenizer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Disposable scalpel No 10</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>Z692395-10EA</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">Metzenbaum scissors 14cm</td>
			<td>Ehrhardt Medizinprodukte GmbH, Geislingen, Germany</td>
			<td>22398330</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">luer lock syringe 5ml</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td style="width:320px;">Z248010</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:469px;">syringe needles</td>
			<td>Sigma-Aldrich, Deisenhoffen, Germany</td>
			<td>Z192368&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Falcon Tube 50ml</td>
			<td>BD Biosciences, Erembodegem, Belgium</td>
			<td style="width:320px;">352070</td>
			<td></td>
		</tr>
	</tbody>
</table>

fluorescence-mediated tomography for the detection and quantification of macrophage-related murine intestinal inflammation

Murine models of disease are indispensable to scientific research. However, many diagnostic tools such as endoscopy or tomographic imaging are not routinely employed in animal models. Conventional experimental readouts often rely on post mortem and ex vivo analyses, which prevent intra-individual follow-up examinations and increase the number of study animals needed. Fluorescence-mediated tomography enables the non-invasive, repetitive, quantitative, three-dimensional assessment of fluorescent probes. It is highly sensitive and permits the use of molecular makers, which allows for the specific detection and characterization of distinct molecular targets. In particular, targeted probes represent an innovative tool for analyzing gene activation and protein expression in inflammation, autoimmune disease, infection, vascular disease, cell migration, tumorigenesis, etc. In this article, we provide step-by-step instructions on this sophisticated imaging technology for the in vivo detection and characterization of inflammation (i.e., F4/80-positive macrophage infiltration) in a widely used murine model of intestinal inflammation. This technique might also be used in other research areas, such as immune cell or stem cell tracking.

Assessment of Colitis:
DSS-induced colitis is a chemically induced murine model of intestinal inflammation that resembles human IBD and leads to weight loss, rectal bleeding, superficial ulceration, and mucosal damage in susceptible mice15. It is particularly useful to study the contribution of the innate immune system to the development of intestinal inflammation10</sup...

Watch this Scientific Journal Video about Fluorescence-mediated Tomography for the Detection and Quantification of Macrophage-related Murine Intestinal Inflammation at JoVE.com

Fluorescence-mediated Tomography for the Detection and Quantification of Macrophage-related Murine Intestinal Inflammation

Target-specific probes represent an innovative tool for analyzing molecular mechanisms, such as protein expression in various types of disease (e.g., inflammation, infection, and tumorigenesis). In this study, we describe a quantitative three-dimensional tomographic assessment of intestinal macrophage infiltration in a murine model of colitis using F4/80-specific fluorescence-mediated tomography.

Murine models of disease are indispensable to scientific research. However, many diagnostic tools such as endoscopy or tomographic imaging are not ...

The overall goal of this target-specific in vivo imaging approach is to visualize molecular markers of disease activity in inflammatory bowel disease. This method can help answering key questions in the field of inflammatory bowel disease, and related therapeutic research about the influence of experimental therapeutics or specific cellular events on inflammation. The main advantage of this technique is that the disease activity can be monitored longitudinally and noninvasively.Though this method can provide insight into inflammatory disorders, it can also be applied to study other diseases, such as cancer or immune-related diseases. To induce colitis, fill the drinking supply of the experimental mice with two grams of dextran sodium sulfate, or DSS, dissolved in 100 milliliters of autoclaved drinking water, estimating five milliliters of water per mouse per day. 24 hours before scanning, load the antibody cocktail of interest into a sterile syringe protected from light and inject the antibodies intravenously into the tail veins of the experimental animals.On the day of the experiment, use an electric razor to shave the fur in the abdominal region of the experimental animals to minimize light reflection and absorption. Using a tissue-mimicking phantom of defined thickness and absorption characteristics, fill the phantom with a specific volume of the antibody solution of interest and measure the fluorescence on the FMT device. Then, on a veterinary fluorescence-mediated tomography, or FMT device for small animals, click New Study and include the relevant tracers in the study description, including the imaging parameters and doses.Create study groups according to the experimental design, equipping each group with the appropriate number of animals. When the system has been calibrated for the tracer constructs, place the first anesthetized mouse in the supine position into a 42 degrees Celsius heatable examination cassette. Insert the cassette into the imaging system and select the appropriate sample from the corresponding study group.Select the administered tracer to ensure that the values of the tracer concentration are properly calculated, and acquire the fluorescence reflectance image at the appropriate wavelength for the scan. Click Acquire Image to outline the scan field and confirm that the scan field appears as an overlay on the fluorescence reflectance image. Adjust the scan field until it surrounds the region of interest, taking care to avoid error or areas of remaining fur.Depending on the image target, select a scan field resolution to set the number of image data points within the scan field. Then click Scan to begin the image acquisition at the selected wavelength. At the end of the scan, remove the animal from the cassette to allow the animal to fully recover with monitoring before returning to its cage.The FMT can then be repeated at various time points as experimentally appropriate. To analyze the acquired images, open the appropriate imaging analysis software and select the raw data for the first scan. Using the reconstruction tool, create 3D maps of the fluorescence distribution.When all of the scans have been added to the appropriate reconstruction dataset, open the first dataset of interest. All of the scans performed for the selected individual experimental animal will be shown. Select the appropriate scan and click Load.A 3D reconstruction of the tracer distribution will appear as an overlay of the initially acquired fluorescence reflectance image. Next, identify the foci of unspecific label accumulation on the reconstructed 3D maps and use the measuring tool to select the region of interest. The software will then generate a fluorescence intensity for the region of interest, as well as picomolar amount measurements of the tracer for which the scan was calibrated.In this experiment, a fluorescence conjugated antibody against murine F4/80 was employed to directly visualize the activated macrophages. A significantly elevated accumulation of fluorescent tracer was measured by fluorescence-mediated tomography in the colons of the colitic mice compared to the non-colitic control animals, indicating an increase in monocyte infiltration and differentiation into active macrophages in the colitic animals. Conversely, the application of a non-specific fluorescence conjugated IgG antibody did not illicit a detectable fluorescence response in the abdomen or intestine in either the colitic or non-colitic control group, demonstrating the specificity of the probe-target interaction of the F4/80 antibody.Ex vivo measurements of F4/80-directed tracer accumulation in explanted colons further verify the colonic origin of the in vivo detected F4/80 tracer signal accumulation. Indeed, calculated amounts of bound antibody correlate well with histologically determined numbers of infiltrating macrophages, confirming that in vivo imaging with specific tracers can be indicative of local disease activity. Once mastered, this can be performed and analyzed within a couple of minutes if it is performed properly.The preparation steps, including the production of specific antibody-based tracers, typically take two to three days. When planning an experimental procedure such as this one, it is important to include appropriate and reliable controls, both for the antibody and the animal disease model. Following this procedure, other methods, like colonoscopy, or flow cytometry can be performed to answer additional questions and to validate and quantify the data.

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Research

JoVE Journal

Medicine

Quantification of Atherosclerotic Plaque Activity and Vascular Inflammation using [18-F] Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (FDG-PET/CT)

Conventional non-invasive imaging modalities of atherosclerosis such as coronary artery calcium (CAC)1 and carotid intimal medial thickness (C-IMT)2 provide information about the burden of disease. However, despite multiple validation studies of CAC3-5, and C-IMT2,6, these modalities do not accurately assess plaque characteristics7,8, and the composition and inflammatory state of the plaque determine its stability and, therefore, the risk of clinical events9-13.
[18F]-2-fluoro-2-deoxy-D-glucose (FDG) imaging using positron-emission tomography (PET)/computed tomography (CT) has been extensively studied in oncologic metabolism14,15. Studies using animal models and immunohistochemistry in humans show that FDG-PET/CT is exquisitely sensitive for detecting macrophage activity16, an important source of cellular inflammation in vessel walls. More recently, we17,18 and others have shown that FDG-PET/CT enables highly precise, novel measurements of inflammatory activity of activity of atherosclerotic plaques in large and medium-sized arteries9,16,19,20. FDG-PET/CT studies have many advantages over other imaging modalities: 1) high contrast resolution; 2) quantification of plaque volume and metabolic activity allowing for multi-modal atherosclerotic plaque quantification; 3) dynamic, real-time, in vivo imaging; 4) minimal operator dependence. Finally, vascular inflammation detected by FDG-PET/CT has been shown to predict cardiovascular (CV) events independent of traditional risk factors21,22 and is also highly associated with overall burden of atherosclerosis23. Plaque activity by FDG-PET/CT is modulated by known beneficial CV interventions such as short term (12 week) statin therapy24 as well as longer term therapeutic lifestyle changes (16 months)25.
The current methodology for quantification of FDG uptake in atherosclerotic plaque involves measurement of the standardized uptake value (SUV) of an artery of interest and of the venous blood pool in order to calculate a target to background ratio (TBR), which is calculated by dividing the arterial SUV by the venous blood pool SUV. This method has shown to represent a stable, reproducible phenotype over time, has a high sensitivity for detection of vascular inflammation, and also has high inter-and intra-reader reliability26. Here we present our methodology for patient preparation, image acquisition, and quantification of atherosclerotic plaque activity and vascular inflammation using SUV, TBR, and a global parameter called the metabolic volumetric product (MVP). These approaches may be applied to assess vascular inflammation in various study samples of interest in a consistent fashion as we have shown in several prior publications.9,20,27,28

Quantification of Atherosclerotic Plaque Activity and Vascular Inflammation using [18-F] Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography FDG-PET/CT

There is great need to identify atherosclerosis non-invasively, and here we demonstrate how FDG-PET/CT can be used to detect and quantify atherosclerotic plaque activity and vascular inflammation.

Conventional non-invasive imaging modalities of atherosclerosis such as coronary artery calcium (CAC)1 and carotid intimal medial thickness (C-IMT)2 ...

Functional Assessment of Intestinal Motility and Gut Wall Inflammation in Rodents: Analyses in a Standardized Model of Intestinal Manipulation

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the complex cellular and molecular of intestinal pathology. Although the tunica mucosa is often the organ of interest in many inflammatory diseases, recent works demonstrated that the muscularis externa (ME) is also a highly immunocompetent organ that harbours a dense network of resident immunocytes.1,2 These works were performed within the standardized model of intestinal manipulation (IM) that leads to inflammation of the bowel wall, mainly limited to the ME. Clinically this inflammation leads to prolonged intestinal dysmotility, known as postoperative ileus (POI) which is a frequent and unavoidable complication after abdominal surgery.3 The inflammation is characterized by liberation of proinflammatory mediators such as IL-64 or IL-1&beta; or inhibitory neurotransmitters like nitric oxide (NO).5 Subsequently, tremendous numbers of immunocytes extravasate into the ME, dominated by polymorphonuclear neutrophils (PMN) and monocytes and finally maintain POI.2 Lasting for days, this intestinal paralysis leads to an increased risk of aspiration, bacterial translocation and infectious complications up to sepsis and multi organ failure and causes a high economic burden.6
In this manuscript we demonstrate the standardized model of IM and in vivo assessment of gastrointestinal transit (GIT) and colonic transit. Furthermore we demonstrate a method for separation of the ME from the tunica mucosa followed by immunological analysis, which is crucial to distinguish between the inflammatory responses in these both highly immunoactive bowel wall compartments. All analyses are easily transferable to any other research models, affecting gastrointestinal function.

Postoperative ileus (POI) is a complication of abdominal surgery leading to increased morbidity and a prolonged hospital stay. Because prophylactic or therapeutic strategies are lacking intensified research is necessary. Therefore we established a standardized and feasible mouse model to investigate the pathophysiology of POI and to study potential therapeutic options.

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the ...

Cerenkov Luminescence Imaging (CLI) for Cancer Therapy Monitoring

In molecular imaging, positron emission tomography (PET) and optical imaging (OI) are two of the most important and thus most widely used modalities1-3. PET is characterized by its excellent sensitivity and quantification ability while OI is notable for non-radiation, relative low cost, short scanning time, high throughput, and wide availability to basic researchers. However, both modalities have their shortcomings as well. PET suffers from poor spatial resolution and high cost, while OI is mostly limited to preclinical applications because of its limited tissue penetration along with prominent scattering optical signals through the thickness of living tissues.
 Recently a bridge between PET and OI has emerged with the discovery of Cerenkov Luminescence Imaging (CLI)4-6. CLI is a new imaging modality that harnesses Cerenkov Radiation (CR) to image radionuclides with OI instruments. Russian Nobel laureate Alekseyevich Cerenkov and his colleagues originally discovered CR in 1934. It is a form of electromagnetic radiation emitted when a charged particle travels at a superluminal speed in a dielectric medium7,8. The charged particle, whether positron or electron, perturbs the electromagnetic field of the medium by displacing the electrons in its atoms. After passing of the disruption photons are emitted as the displaced electrons return to the ground state. For instance, one 18F decay was estimated to produce an average of 3 photons in water5. 
 Since its emergence, CLI has been investigated for its use in a variety of preclinical applications including in vivo tumor imaging, reporter gene imaging, radiotracer development, multimodality imaging, among others4,5,9,10,11. The most important reason why CLI has enjoyed much success so far is that this new technology takes advantage of the low cost and wide availability of OI to image radionuclides, which used to be imaged only by more expensive and less available nuclear imaging modalities such as PET.
 Here, we present the method of using CLI to monitor cancer drug therapy. Our group has recently investigated this new application and validated its feasibility by a proof-of-concept study12. We demonstrated that CLI and PET exhibited excellent correlations across different tumor xenografts and imaging probes. This is consistent with the overarching principle of CR that CLI essentially visualizes the same radionuclides as PET. We selected Bevacizumab (Avastin; Genentech/Roche) as our therapeutic agent because it is a well-known angiogenesis inhibitor13,14. Maturation of this technology in the near future can be envisioned to have a significant impact on preclinical drug development, screening, as well as therapy monitoring of patients receiving treatments.

Cerenkov Luminescence Imaging CLI for Cancer Therapy Monitoring

Use of Cerenkov Luminescence Imaging (CLI) for monitoring preclinical cancer treatment is described here. This method takes advantage of Cerenkov Radiation (CR) and optical imaging (OI) to visualize radiolabeled probes and thus provides an alternative to PET in preclinical therapeutic monitoring and drug screening.

In  molecular imaging, positron emission tomography (PET) and optical imaging (OI)  are two of the most important and thus most widely used modalities1-3. ...

Murine Endoscopy for In Vivo Multimodal Imaging of Carcinogenesis and Assessment of Intestinal Wound Healing and Inflammation

Mouse models are widely used to study pathogenesis of human diseases and to evaluate diagnostic procedures as well as therapeutic interventions preclinically. However, valid assessment of pathological alterations often requires histological analysis, and when performed ex vivo, necessitates death of the animal. Therefore in conventional experimental settings, intra-individual follow-up examinations are rarely possible. Thus, development of murine endoscopy in live mice enables investigators for the first time to both directly visualize the gastrointestinal mucosa and also repeat the procedure to monitor for alterations. Numerous applications for in vivo murine endoscopy exist, including studying intestinal inflammation or wound healing, obtaining mucosal biopsies repeatedly, and to locally administer diagnostic or therapeutic agents using miniature injection catheters. Most recently, molecular imaging has extended diagnostic imaging modalities allowing specific detection of distinct target molecules using specific photoprobes. In conclusion, murine endoscopy has emerged as a novel cutting-edge technology for diagnostic experimental in vivo imaging and may significantly impact on preclinical research in various fields.

Murine Endoscopy for In Vivo Multimodal Imaging of Carcinogenesis and Assessment of Intestinal Wound Healing and Inflammation

Small animal imaging techniques allow serial diagnostic examinations and therapeutic interventions in vivo. Recently, the scope of applications has significantly widened and currently includes assessment of colonic tumor development, wound healing and monitoring of inflammation. This protocol illustrates these diverse potential applications of murine endoscopy.

Mouse models are widely used to study pathogenesis of human diseases and to evaluate diagnostic procedures as well as therapeutic interventions ...

Mouse Kidney Transplantation: Models of Allograft Rejection

Rejection of the transplanted kidney in humans is still a major cause of morbidity and mortality. The mouse model of renal transplantation closely replicates both the technical and pathological processes that occur in human renal transplantation. Although mouse models of allogeneic rejection in organs other than the kidney exist, and are more technically feasible, there is evidence that different organs elicit disparate rejection modes and dynamics, for instance the time course of rejection in cardiac and renal allograft differs significantly in certain strain combinations. This model is an attractive tool for many reasons despite its technical challenges. As inbred mouse strain haplotypes are well characterized it is possible to choose donor and recipient combinations to model acute allograft rejection by transplanting across MHC class I and II loci. Conversely by transplanting between strains with similar haplotypes a chronic process can be elicited were the allograft kidney develops interstitial fibrosis and tubular atrophy. We have modified the surgical technique to reduce operating time and improve ease of surgery, however a learning curve still needs to be overcome in order to faithfully replicate the model. This study will provide key points in the surgical procedure and aid the process of establishing this technique.

Here, we present a protocol to study the immunology of rejection. The surgical model presented reports a short operating time and a concise technique. Depending on the donor-recipient strain combination, the transplanted kidney may develop acute cellular rejection or chronic allograft damage, defined by interstitial fibrosis and tubular atrophy.

Rejection of the transplanted kidney in humans is still a major cause of morbidity and mortality. The mouse model of renal transplantation closely ...

A Murine Model of Irreversible and Reversible Unilateral Ureteric Obstruction

Obstruction of the kidney may affect native or transplanted kidneys and results in kidney injury and scarring. Presented here is a model of obstructive nephropathy induced by unilateral ureteric obstruction (UUO), which can either be irreversible (UUO) or reversible (R-UUO). In the irreversible UUO model, the ureter may be obstructed for variable periods of time in order to induce increasingly severe renal inflammation and interstitial fibrotic scarring. In the reversible R-UUO model the ureter is obstructed to induce hydronephrosis, tubular dilation and inflammation. After a suitable period of time the ureteric obstruction is then surgically reversed by anastomosis of the severed previously obstructed ureter to the bladder in order to allow complete decompression of the kidney and restoration of urinary flow to the bladder. The irreversible UUO model has been used to investigate various aspects of renal inflammation and scarring including the pathogenesis of disease and the testing of potential anti-inflammatory or anti-fibrotic therapies. The more challenging model of R-UUO has been used by some investigators and does offer significant research potential as it allows the study of inflammatory and immune processes and tissue remodeling in an injured and scarred kidney following the removal of the injurious stimulus. As a result, the R-UUO model offers investigators the opportunity to explore the resolution of kidney inflammation together with key aspects of tissue repair. These experimental models are of relevance to human disease as patients often present with obstruction of the renal tract that requires decompression and are commonly left with significant residual kidney impairment that has no current treatment options and may lead to eventual end stage kidney failure.

The murine model of irreversible unilateral ureteric obstruction (UUO) is presented together with the model of reversible UUO in which the ureteric obstruction is relieved by anastomosis of the severed ureter into the bladder. These models enable the study of renal inflammation and scarring as well as tissue remodeling.

Obstruction of the kidney may affect native or transplanted kidneys and results in kidney injury and scarring. Presented here is a model of obstructive ...

Murine Model of Intestinal Ischemia-reperfusion Injury

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, hypotension, necrotizing enterocolitis, bowel transplantation, trauma and chronic inflammation. Intestinal ischemia-reperfusion (IR) injury is a consequence of acute mesenteric ischemia, caused by inadequate blood flow through the mesenteric vessels, resulting in intestinal damage. Reperfusion following ischemia can further exacerbate damage of the intestine. The mechanisms of IR injury are complex and poorly understood. Therefore, experimental small animal models are critical for understanding the pathophysiology of IR injury and the development of novel therapies.
Here we describe a mouse model of acute intestinal IR injury that provides reproducible injury of the small intestine without mortality. This is achieved by inducing ischemia in the region of the distal ileum by temporally occluding the peripheral and terminal collateral branches of the superior mesenteric artery for 60 min using microvascular clips. Reperfusion for 1 hr, or 2 hr after injury results in reproducible injury of the intestine examined by histological analysis. Proper position of the microvascular clips is critical for the procedure. Therefore the video clip provides a detailed visual step-by-step description of this technique. This model of intestinal IR injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Here we describe the detailed procedure of intestinal ischemia-reperfusion in mice which results in reproducible injury without mortality to encourage the standardization of this technique across the field. This model of intestinal ischemia-reperfusion injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, ...

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Cardiovascular disease is the leading cause of morbidity and mortality in the world. Atherosclerotic plaques, consisting of lipid-laden macrophages and calcification, develop in the coronary arteries, aortic valve, aorta, and peripheral conduit arteries and are the hallmark of cardiovascular disease. In humans, imaging with computed tomography allows for the quantification of vascular calcification; the presence of vascular calcification is a strong predictor of future cardiovascular events. Development of novel therapies in cardiovascular disease relies critically on improving our understanding of the underlying molecular mechanisms of atherosclerosis. Advancing our knowledge of atherosclerotic mechanisms relies on murine and cell-based models. Here, a method for imaging aortic calcification and macrophage infiltration using two spectrally distinct near-infrared fluorescent imaging probes is detailed. Near-infrared fluorescent imaging allows for the ex vivo quantification of calcification and macrophage accumulation in the entire aorta and can be used to further our understanding of the mechanistic relationship between inflammation and calcification in atherosclerosis. Additionally, a method for isolating and culturing animal aortic vascular smooth muscle cells and a protocol for inducing calcification in cultured smooth muscle cells from either murine aortas or from human coronary arteries is described. This in vitro method of modeling vascular calcification can be used to identify and characterize the signaling pathways likely important for the development of vascular disease, in the hopes of discovering novel targets for therapy.

Vascular calcification is an important predictor of and contributor to human cardiovascular disease. This protocol describes methods for inducing calcification of cultured primary vascular smooth muscle cells and for quantifying calcification and macrophage burden in animal aortas using near-infrared fluorescence imaging.

Cardiovascular disease is the leading cause of morbidity and mortality in the world.  Atherosclerotic plaques, consisting of lipid-laden macrophages and ...

A Fluorescence-based Assay for Characterization and Quantification of Lipid Droplet Formation in Human Intestinal Organoids

Dietary lipids are taken up as free fatty acids (FAs) by the intestinal epithelium. These FAs are intracellularly converted into triglyceride (TG) molecules, before they are packaged into chylomicrons for transport to the lymph or into cytosolic lipid droplets (LDs) for intracellular storage. A crucial step for the formation of LDs is the catalytic activity of diacylglycerol acyltransferases (DGAT) in the final step of TG synthesis. LDs are important to buffer toxic lipid species and regulate cellular metabolism in different cell types. Since the human intestinal epithelium is regularly confronted with high concentrations of lipids, LD formation is of great importance to regulate homeostasis. Here we describe a simple assay for the characterization and quantification of LD formation (LDF) upon stimulation with the most common unsaturated fatty acid, oleic acid, in human intestinal organoids. The LDF assay is based on the LD-specific fluorescent dye LD540, which allows for quantification of LDs by confocal microscopy, fluorescent plate reader, or flow cytometry. The LDF assay can be used to characterize LD formation in human intestinal epithelial cells, or to study human (genetic) disorders that affect LD metabolism, such as DGAT1 deficiency. Furthermore, this assay can also be used in a high-throughput pipeline to test novel therapeutic compounds, which restore defects in LD formation in intestinal or other types of organoids.

This protocol describes an assay for the characterization of lipid droplet (LD) formation in human intestinal organoids upon stimulation with fatty acids. We discuss how this assay is used for quantification of LD formation, and how it can be used for high throughput screening for drugs that affect LD formation.

Dietary lipids are taken up as free fatty acids (FAs) by the intestinal epithelium. These FAs are intracellularly converted into triglyceride (TG) ...

A Murine Model of Fetal Exposure to Maternal Inflammation to Study the Effects of Acute Chorioamnionitis on Newborn Intestinal Development

Chorioamnionitis is a common precipitant of preterm birth and is associated with many of the morbidities of prematurity, including necrotizing enterocolitis (NEC). However, a mechanistic link between these two conditions remains yet to be discovered. We have adopted a murine model of chorioamnionitis involving lipopolysaccharide (LPS)-induced fetal exposure to maternal inflammation (FEMI). This model of FEMI induces a sterile maternal, placental, and fetal inflammatory cascade, which is also present in many cases of clinical chorioamnionitis. Although models exist that utilize live bacteria and more accurately mimic the pathophysiology of an ascending infection resulting in chorioamnionitis, these methods may cause indirect effects on development of the immature intestinal tract and the associated developing microbiome. Using this protocol, we have demonstrated that LPS-induced FEMI results in a dose-dependent increase in pregnancy loss and preterm birth, as well as disruption of normal intestinal development in offspring. Further, we have demonstrated that FEMI significantly increases intestinal injury and serum cytokines in offspring, while simultaneously decreasing goblet and Paneth cells, both of which provide a first line of innate immunity against intestinal inflammation. Although a similar model of LPS-induced FEMI has been used to model the association between chorioamnionitis and subsequent abnormalities of the central nervous system, to our knowledge, this protocol is the first to attempt to elucidate a mechanistic link between chorioamnionitis and later perturbations in intestinal development as a potential link between chorioamnionitis and NEC.

We developed a model of chorioamnionitis to simulate fetal exposure to maternal inflammation (FEMI) without complications of live organisms to examine the effects of FEMI on development of the offspring&#8217;s intestinal tract. This allows for study of mechanistic causes for development of intestinal injury following chorioamnionitis.