Using Fluorescence-Mediated Tomography to Assess Murine Intestinal Inflammation

Allow a caged mouse to consume drinking water mixed with a synthetic sulfated polysaccharide known to induce colitis, an inflammatory bowel disease.

This polysaccharide penetrates the intestinal lumen and disrupts the epithelial barrier, allowing commensal microbes to penetrate the tissue, leading to inflammation.

Monocytes infiltrate the tissue and differentiate into macrophages.

Intravenously inject fluorophore-conjugated antibodies into the tail of the mouse.

The antibodies reach the colon and bind to the target glycoprotein on macrophages, labeling the cells.

Anesthetize the mouse. Shave the abdominal fur to minimize light reflection and absorption during imaging.

Place the mouse in an examination cassette and insert it into a fluorescence-mediated tomography or FMT scanner.

Upon excitation, the fluorophore emits a fluorescence. Capture the fluorescence reflectance images to reconstruct a three-dimensional map showing the spatial distribution of the fluorophores.

An elevated fluorescence intensity indicates an increased macrophage infiltration.

To induce colitis, fill the drinking supply of the experimental mice with 2 grams of dextran sodium sulfate, or DSS, dissolved in 100 milliliters of autoclaved drinking water, estimating 5 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 study 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 air 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.