A Mouse Abdominal Aortic Aneurysm Model by Periadventitial Calcium Chloride and Elastase Infiltration

This study presents a protocol for establishing a mouse abdominal aortic aneurysm model using calcium chloride and elastase, which can be used to investigate the pathophysiological mechanism under abdominal aortic aneurysm. Our protocol combines advantages of periadventitial PPE and calcium chloride infiltration, which is a safe, stable, and reproducible mouse triple A model, demonstrating a high incidence rate of triple A, significant of abdominal aorta and pathophysiological changes resembling those observed in human triple A.In future, our research team is committed to dedicated engagement in clinical and basic research pertaining to and peripheral artery disease with a particular focus on the pathogenesis of these foundations and the development of therapeutic approaches. To begin, place the anesthetized mouse in a supine position on the heating pad.

After shaving and disinfection, place the mouse under the stereo microscope. Using scissors, make a longitudinal incision of approximately two to 2.5 centimeters along the midline of the abdomen. Enter the peritoneal cavity through the linea alba using the transabdominal approach.

Place a retractor to expose the peritoneal cavity. Pack the intestines and colon into the right half of the abdomen using normal saline-soaked gauze. Perform blunt separation of connective and adipose tissue adjacent to the infrarenal abdominal aorta and inferior vena cava, using forceps and cotton swabs.

Gently dissect the abdominal aorta and expose the gap between the abdominal aorta and the overlying psoas major. Insert the sterilized cotton pad strips into the gap without damaging the lumbar artery or vein. Place the cotton balls soaked in 0.9 molar calcium chloride on the adventitia of the abdominal aorta.

After 15 minutes, remove the cotton ball. Dilute the elastase to two milligrams per milliliter with double distilled water. Using an insulin syringe, apply 50 microliters of diluted elastase to the infrarenal segment of the abdominal aorta.

Wrap the cotton pad strips to cover the abdominal aorta and inferior vena cava. Cover the abdominal cavity during the process of infiltration with sterilized gauze. After 15 minutes, carefully remove the gauze and cotton pad strips, move the intestines and colon back to their original positions.

Cover the treated aorta with the mesentery and moisten the intestines with 0.9%saline to prevent adhesion. Using a 6/O non-absorbable polypropylene suture, close the muscle layer and skin. Place the mouse on the heating pad of the rodent ultrasound machine.

Apply ultrasonic couplant to the abdomen and measure the maximum diameter of the aneurysm and the diameter of the normal segment of the abdominal aorta. In an Excel sheet, calculate the increased percentage of the infrarenal abdominal aorta. After the examination, use a napkin to wipe off the remaining ultrasonic couplant and place the mouse on the heating pad until fully recovered.

In the PPE plus calcium chloride, 91.67%of mice developed abdominal aortic aneurysm at 21 days after surgery, whereas no aneurysm formation was observed in the sham group. The average maximum internal diameter of the infrarenal abdominal aorta was significantly larger in the PPE plus calcium chloride group compared to the sham group. The average maximum external diameter of the infrarenal abdominal aorta was significantly larger in the PPE plus calcium chloride group compared to the sham group.

Histological examination revealed thickening of the aortic wall, inflammatory cell infiltration, extracellular matrix degradation, collagen fiber deposition, and elastic fiber breakdown in the PPE plus calcium chloride group compared to the sham group.