A Rat Model of Mild Intrauterine Hypoperfusion with Microcoil Stenosis

The overall goal of this surgical intervention is to use metal microcoils, wrapped around both uterine and ovarian arteries, to induce artery stenosis for the generation of mild intrauterine hypoperfusion. This method can help answer key questions in the fetal brain injury field, such as, how does mild intrauterine hypoperfusion influence neural development later in life? The main advantage of this technique is that an entire litter of fetuses can be subjected to an equal degree of mild hypoperfusion at the same time.

On embryonic day 17, place an anesthetized, pregnant rat dam in the supine position on a sterile diaper placed on top of a heating pad. Confirm a lack of response to toe pinch and apply ointment to the animal's eyes. Remove the hair from the navel area to the pelvic arch, and use an iodine soaked gauze, soaked to disinfect the exposed skin.

Place a sterile drape over the animal with the round opening over the surgical area, and use a scalpel to make an approximately 2.5 centimeter skin incision in the lower abdomen, from the upper edge of the public bone toward the navel. Make a secondary incision through the corresponding muscle layer and place several pieces of sterile gauze around the opening of the drape. Wet the gauze with 37 degree Celsius saline and gently push both lateral sides of the abdomen until a portion of uterine horn emerges from the incision.

Using 70%ethanol-sterilized fingers, gently remove one entire uterine horn from the abdominal cavity and place the horn on the wet gauze. After removing the second uterine horn, apply 37 degree Celsius saline to keep the horns warm and place the animal under a stereo microscope. Keeping the uterus warm and wet throughout the procedure is critical.

Otherwise, many fetuses may be lost before delivery. Locate the proximal region of the main arcade of the ovarian and uterine arteries, and use forceps to separate the artery from the vein running parallel to the artery. It is essential for a successful procedure to identify the proximal portion of the main arcade of the ovarian and uterine arteries, which is small in diameter but has numerous branches to the placentas.

Place a 5 centimeter long piece of 4-0 silk suture under the artery and lift both ends of the suture with the forceps until the artery is separated from the vein. Using fine forceps, place a gold-coated steel microcoil next to the lifted artery and use the suture to rotate the artery three or four turns around the microcoil. Then, grasp the coil with the fine forceps at the wrapped end and wrap the artery around the naked end of the coil as just demonstrated.

After wrapping the three other arteries with microcoils in the same manner, gently return the uterine horn to the abdominal cavity and use interrupted single 4-0 silk sutures to individually close the muscle and skin layers. Then, allow the rat to recover in a warmed cage with monitoring until full recovery. Applying microcoils to the bilateral uterine and ovarian arteries causes a mild stenosis of the arteries and a mild decrease in blood flow to all of the placentas and fetuses.

Each fetus is then subjected to similar levels of hypoperfusion, approximately 30%from pre-stenosis level in the placenta, resulting in the consequent development of intrauterine growth-restricted pups. After its development, this technique paved the way for researchers in the field of brain injury to explore the inference of mild intrauterine hypoperfusion in a prenatal rodent.