A Visual Approach for Inducing Dolichoectasia in Mice to Model Large Vessel-Mediated Cerebrovascular Dysfunction

The scope of our research is the model dolichoectasia in a transgenic mouse model to see the maximum impact that vascular changes have on Alzheimer's disease pathology. We are able to show that a single dose of elastase injection into the cisterna magna of mice is able to cause dilatation up to three months. Not much is known about individuals who suffer from both vascular dementia and Alzheimer disease.

We hope to bridge this gap by causing vascular changes in these transgenic mouse model to try and understand the pathogenesis of this form of mixed dementia. Previous studies were able to show that dilatation lasts up to two weeks. In our study, we showed that dilatation lasts up to three months with a low mortality during our surgical procedure.

Successful dilatation of large blood vessel in a transgenic mouse model provides us with the opportunity to test drugs to prevent or improve vascular changes in Alzheimer's disease. To begin, place an anesthetized mouse on a fresh surgical drape. Apply ophthalmic ointment to the animal's eye to prevent dryness.

Then inject metacam followed by 0.5 mL of saline subcutaneously into the mouse. Shave the neck of the mouse at the base of the occipital bone and wipe down the surface with sterile PBS. Transfer the mouse to the stereotaxic frame in the prone position.

Place the nose bar from the stereotaxic frame on top of the mouse to provide stability and ensure the upper teeth are fastened. Position the animal head at a 120 degree angle from the body to elevate and distend the nape. Next, using sterile gauze, clean the surgical site three times with Betadine scrub and 70%ethanol.

Then wipe once with Betadine solution. Using a scalpel, make a small 1 cm incision. Carefully run the scalpel along the midline to cut through the muscles.

Using forceps, gently pull the muscles apart to the left and the right, then load the Hamilton syringe with 2.5 L of elastase, avoiding air bubbles. Slowly insert the syringe with the bevel facing upward into the center of the cisterna magna. After puncturing, carefully withdraw the bevel to facilitate the release of a small amount of cerebral spinal fluid or CSF.

Next, reinsert the bevel to the puncture site and slowly inject elastase or a vehicle into the cistern magna, leaving the needle in place for one minute to prevent elastase leakage. After removing the bevel, close the incision site with a non-absorbable surgical suture and turn off the anesthetic. Remove the animal from the stereotaxic frame and place it on a 37 C heat pad until the mouse recovers.

To begin, place the anesthetized mouse on an absorbent pad or diaper. Pinch the mouse toe to confirm the ceased reflexes. Using surgical tape, secure all limbs with the chest cavity facing upward.

Employing tweezers and scissors, carefully open the chest cavity to expose the heart. Insert a 23-gauge blunt needle into the left ventricle of the heart for perfusion. Then mix 5 mL of silicone rubber compound solution with 5 mL of the diluent in a 50 mL tube.

Using a hose linked 23-gauge blunt needle, inject 10 mL of the mixed compound into the heart. Next day using fine tweezers, gently remove the skull of the mouse and place the extracted brain in 4%paraformaldehyde at room temperature. After a 24-hour incubation, wash the brain three times in PBS and store it in 30%sucrose at 4 C.Pictographs of brains illustrated the enlargement of the basilar artery and increased tortuosity around the circle of Willis following elastase injection compared with the PBS control group.

Compared to the control group treated with PBS, a significant blood vessel dilation was observed following a single elastase injection into the cisterna magna of three-month-old mice, which sustained for three months.