A Simple Device to Rapidly Prepare Whole Mounts of the Mouse Intestine

The overall goal of this procedure is to prepare whole mounds of the mouse, small intestine and colon. This is accomplished by first removing, rinsing and blotting the colon and small intestine. In the second step, the colon and small intestine are laid out.

The seum is removed and the small intestine is divided into thirds. A rod is then threaded through the three tissue segments and the segments are sectioned for scoring. In the final step, the rods are gently rolled to flatten the segments of small intestine and the tissues are Swiss rolled for further downstream analysis, ultimately, histology and or immunohistochemistry can be performed to characterize the intestinal tumor genesis.

The main advantage of this technique of existing methods like offset is that this procedure is far quicker and it use much better preparations. This procedure uses a device consisting of the base that has high elevated strips at each end with grooves to take the rods and the lid. After harvesting the small intestine and colon from an adult mouse, hold the mesentery with curved forceps and gently pull the tissue away from the intestine To remove it, place a Gilson type pipette tip cut at the wider end onto a 10 or 20 milliliter lure fitting plastic syringe, and rinse the intestines with cold PBS.

After the tissue has been washed, lay out the small bowel and colon on a paper towel and use scissors to divide the small bowel into three equal sections. Make several very small cuts in the intestinal segments to drain the fluid. Then place another paper towel over the intestines and gently run a finger over the segments to squeeze out the remaining fluid.

Next, blot the preparations dry and gently. Insert stainless steel rods soaked in PBS into the tissues using a pencil. Create labels for the segments, including the autopsy date, experimental code, and animal identification number.

Place the labels in the base of the device. Then insert the rods and intestines into the slots at the base of the device. Taking care that the proximal end of the segments are positioned in a standardized way near the labels.

Now place the top piece of the device over the base and use the angled bars to guide a scalpel blade longitudinally through the segments to keep the tissue in place. During the sectioning, carefully hold the segments with a finger so that they do not move with a knife. After all of the sections have been made, remove the top of the device and use a piece of stiff card to carefully remove the filter paper and the tissues.

Using a gloved fingertip dipped in PBS slightly wet the segments. Gently roll the rod side to side to open up the gut and to spread the tissue flat. The sections will adhere to the filter paper.

After visually examining the preparations for any gross lesions, transfer the filter paper to a shallow bath of fixative. When the tissues are fixed, transfer them into 70%ethanol for storage until further downstream analysis. For example, to make a Swiss roll, remove the intestinal segments from the filter paper and roll the tissue around a cocktail stick.

Then secure the tissue and process the sample for further histological processing. The use of this device generates the production of far better quality preparations, which make subsequent analysis and quantification much easier. Polyps are easy to identify under a stereo microscope with side illumination of the tissue by a cold light source.

It is helpful to mark the card with pencil marks when a polyp is observed for later discussion or quality control. The tissue can also be bulk stained to identify the aberrant crypt or mucin depleted foci. The location of the lesions can be scored on a positional basis by creating several grids of known sizes on the computer and printing the grids on a piece of acetate.

The grids that fit the length of the sections can then be used to score the events of interest. Once scored, whole sections can be rolled into a Swiss roll for histological sectioning, which can then be used to score micro polyps. Once master, this technique can be completed in this sample minutes if it is performed properly.