We describe here stenosis in the inferior vena cava as a murine model of deep vein thrombosis. This model recapitulates blood flow restriction, one of the major triggers of venous thrombosis in humans.
The overall goal of this surgical procedure is to create a stenosis of the inferior vena cava to mimic blood flow distortion for the initiation of deep vein thrombosis. This method can help to answer key questions in the venous thrombosis field about the mechanisms of deep vein thrombosis initiation. The main advantage of this technique is that it simulates blood flow disturbance, a key mechanism of thrombosis initiation in the veins.
Visual demonstration of this method is critical as separating the inferior vena cava from the aorta and making the hole between these tissues are difficult to explain verbally. Begin by shaving the abdomen of a eight to 12 week old anesthetized 19 to 25 gram mouse and place the mouse in the supine position on a heating pad. Use a sterile cotton bud to disinfect the exposed skin three times with antibacterial solution.
Confirm the appropriate level of sedation by a lack of response to toe pinch and cover the mouse with a sterile drape with a hole over the surgical site. Under a dissecting microscope, make an incision along the abdominal midline, starting 1.5 centimeters below the sternum and use cotton buds to exteriorize the intestines to the left side of the animal. Cover the intestinal tissue with sterile gauze soaked in 37 degrees Celsius saline.
Place tissue retractors to expand the incision and locate the inferior vena cava, or IVC, and its side branches caudal to the left renal vein. Using forceps, pull up on the fat tissue surrounding the side branches, then use a second forceps to tunnel beneath the branch. And ligate all of the side branches as close to the IVC as possible with 7-0 inert prolene sutures.
Holding the surrounding tissues with forceps, pull the IVC up and left to produce tension in the small area between the IVC and the aorta, precisely between the IVC and the left renal vein. Insert a second pair of forceps between the aorta and the IVC and open and close the forceps no more then three to five times to make a hole. It is very important to make the hole precisely at the point where the IVC converges with the left renal vein.
Using the left hand, place a two centimeter piece of 7-0 inert prolene suture into the left side of the peritoneal cavity, close to the IVC, and pull the IVC up and left again. Insert the second forceps into the hole between the aorta and the IVC so that the tips appear on the other side of the IVC and pull the suture back through the hole. Make a loose provisional knot and place a 30 gauge needle spacer, bent into a hook, into the knot.
After tightening the knot, remove the spacer and use a cotton bud to return the intestines to the peritoneal cavity. Using continuous loops, close the peritoneum with a 6-0 VICRYL suture and close the skin with metal staples. Subcutaneously inject the mouse with 0.5 milliliters of 37 degrees Celsius glucosaline.
Then, place the mouse into an individual cage in a 25 degree Celsius chamber containing food and gel water with monitoring until full recovery. The induction of stenosis in the IVC initiates a distortion and stagnation of the blood flow resulting in the development of a thrombus that is structurally similar to the deep vein thrombi observed in humans and that is easily visualized macroscopically. In addition, elevated D-dimer, a product of fibrin degradation, is observed in the plasma in this IVC stenosis model, indicating the presence of an active thrombotic process similar to that seen in humans.
Although most of the experimental animals produced thrombi in this model, one major disadvantage is the variability within the size of the thrombi observed between animals. Once mastered, this technique can be completed in 15 minutes if it is performed properly. After its development, this technique paved the way for researchers in the field of venous thrombosis to explore the mechanisms of DVT in a mouse model.
