Mouse Abdominal Aortic Aneurysm Model Induced by Perivascular Application of Elastase

This is a standardized protocol for elastase induced abdominal aortic aneurysm, which would greatly enhance the reproducibility and the consistency of studies using this model. This technique has a consistent induction rate of abdominal aortic aneurysm. It also owns the advantage of low expenses and short operation time, which will result in stronger statistical power and the reproducibility.

You need to ensure the connective tissues covering the aorta were removed so that the elastase will have a better chance of penetration, but be careful not to damage the vessels. To begin, administer five milligrams per kilograms of carprofen subcutaneously, 30 minutes before the induction of anesthesia. Test the anesthetized mouse for the lack of toe pinch response before skin incision.

Make a 2.5 centimeter longitudinal incision on the skin, along the midline of the middle and lower abdomen. Gently pull up the underlying muscle and make a 2.5 centimeter longitudinal incision along linea alba. Use wetted cotton tipped applicators to move the intestines and stomach to the right side of the mouse, and access the abdominal cavity.

Use forceps to gently remove the connective tissue covering the abdominal aorta and inferior vena cava. Use forceps to gently dissect the backside of the abdominal aorta and inferior vena cava from the underlying muscles. Place a piece of four centimeters by four millimeters glove stripe through the backside of the abdominal aorta and inferior vena cava, and straighten the stripe.

Place the stripe approximately 0.5 centimeters away from the right renal artery. Above the stripe, place a piece of three centimeters by two millimeters cotton pad through the backside of the abdominal aorta and inferior vena cava. Then, straighten the cotton pad.

To incubate the elastase, use a pipette to drop 30 microliters of porcine pancreatic elastase onto the aorta segment above the cotton pad. Wrap the cotton pad and stripe around the aorta and inferior vena cava. Rinse a piece of 10 centimeters by 10 centimeters gauze with sterile 0.9%saline and place it on the abdomen.

After 30 minutes, remove the stripe and cotton pad with forceps. Irrigate the aorta and abdominal cavity with 500 microliters of sterile 0.9%saline. Use gauze to absorb the remaining saline.

Re-approximate the muscle layers with a running 6-0 non-absorbable monofilament suture. Then, close the skin with three to four interrupted at 6-0 non-absorbable monofilament sutures. The incidence rate of developing an abdominal aortic aneurysm on postoperative day 14 was 91.7%for female animals, while the incidence rate for male animals was 72.7%Among the 19 animals in which abdominal aortic aneurysm was developed, a 1.7 fold and 1.6 fold increase of maximum abdominal aortic diameter was observed, in females and males respectively, compared to non-surgery controls.

Representative images of the aorta from non-surgery and surgery groups on a post-operative day 14 are displayed. This technique served as a potential tool to help dissect the pathophysiology of triple A and help for the discovery of new potential therapeutic targets.