Ultrasound-guided Intracardiac Injection of Human Mesenchymal Stem Cells to Increase Homing to the Intestine for Use in Murine Models of Experimental Inflammatory Bowel Diseases

The overall goal of this procedure is to use ultrasound-guided intracardiac human bone marrow derived mesenchymal stem cell or HMSC injection in a mouse model of experimental crohn's disease, to observe HMSC homing to the intestine. This method can help answer the key questions in the inflammatory bowel disease field, about the need for increased localisations of HMSC to small intestine during inflammation. The main advantage of this technique is that it facilitates a high HMSC delivery success rate with minimal mouse mobility and mortality.

Generally, individuals new to this method can have trouble because multiple variables, they can affect the procedure outcome. Requiring a lot of trainee understanding of human mesenchymal stem cell biology. Demonstrating the procedures will be Paola Menghini, a post doc from our laboratory.

In a specific pathogen free facility, set up the mouse echocardiogram ultrasound imaging system protocol and initialize the 30 megahertz transducer. Next, confirm the appropriate level of sedation by toe pinch and apply ointment to the animal's eyes. Use depilatory cream to remove the hair over the thorax and place the animal on the 37 degree celsius imaging table in the supine position.

Tape the limbs to prevent movement during the procedure and disinfect the exposed skin of the thorax with 10%povidone iodine and 70%ethanol. Apply a thick layer of 37 degree celsius ultrasound gel to the skin and mount the transducer in the holder, adjusting the position of the transducer until the left ventricle is clearly visible in the field of view. Next, gently re-suspend 2 x 10 to the sixth transduced human mesenchymal stem cells in 150 microliters of sterile PBS to generate a homogenous cell suspension and load the cells into a one milliliter syringe equipped with a 28 gauge needle.

Inject less than 150 microliters of cell suspension per mouse to avoid a volume overload and death. Secure the syringe in a syringe holder. Then, advance the syringe towards the mouse thorax using the ultrasound guidance to adjust the needle trajectory as necessary and penetrate the needle tip through the intercostal space into the left ventricle.

Adequate visualization of the needle on the ultrasonographic image is critical for ensuring a proper trajectory and insertion of the needle into the left ventricle, a successful injection and the avoidance of cardiac dampening and death. The tip should be clearly visible within the left ventricle and proper placement can be further confirmed by fresh arterial blood outflow into the syringe. Apply a gentle pressure to the plunger to slowly inject the HMSC suspension over a period of two minutes.

When all the cells have been injected, gently withdraw the needle and place the animal in a clean cage on a preheated pad with monitoring until full recovery. 24 hours after the injection, initialize the bioluminescence imaging system and open a new study in the in-vivo imaging software. To set the imaging parameters in the control panel, click the sequence set up.

In the imaging mode, select luminescent and photograph. Set the exposure times from 0.5 seconds to 10 minutes, the bidding to medium and the f/stop to one. Set the excitation filter to block, the emission filter to open and the field of view to see for two mice.

Then click on the acquisition control panel to add the sequence set up to the image wizard. Next, inject the first mouse with 300 microliters of d-luciferin. Apply ointment to the animals'eyes and transfer the mouse to the in-vivo imaging chamber.

10 minutes after the d-luciferin injection, click acquire, to begin the image acquisition. After all the mice have been imaged, harvest the whole gastrointestinal tract, mesenteric lymph nodes, lungs, spleen and liver from each animal. Then image the organs as just demonstrated, for whole animal bioluminescence imaging.

HMSC can be transduced with the triple reporter at a high efficiency preserving the stem cell properties and allowing their visualization in real time by bioluminescence imaging. Ex-vivo analysis of the intracardiac delivered stem cells, confirms that this root of administration facilitates HMSC homing to the inflamed small intestines of the experimental crohn's disease mice. HMSC is injected into control, inflammation free animals however, do not accumulate in the small intestine.

Once mastered, this technique can be completed in less than 15 minutes per mouse if it is performed properly. While attempting this procedure, it's important to remember to use the ultrasound image to adjust the needle trajectory. A poor technique and an incorrect trajectory can lead to cardiac tamponade from hemorrhagic pericardial effusion and death.

Following this procedure, other methods like histology and 3D studio microscopy can be performed to answer additional questions such as, does an increased homing of HMSC to the small intestine augment that therapeutic efficacy. This technique will allow researchers in the field of experimental IBD to explore all their mouse models like TNF trajectory, can be injected with HMSCs to enhance homing to the small intestine. After watching this video, you should have a good understanding of how to perform ultrasound guided intracardiac injection of HMSC in mice and of how to use bioluminescent imaging to analyze a bad distribution and homing.

Don't forget that working with human MSCs can be hazardous and that precautions such as, using gloves and a face mask with a shield, should always be taken while performing this procedure.