Mouse Model of Surgical Uterine Injury and Subsequent Pregnancy Outcomes

We are investigating how uterine scarring from C-sections or other procedures can result in several morbidities in subsequent pregnancies, including placenta previa, placenta accreta spectrum and infertility.

Understanding the mechanisms by which uterine injury leads to subsequent pregnancy defects has been challenging without animal models. Therefore, we have developed a new mouse model to address this research gap. This animal model of uterine injury enables researchers to study uterine wound responses and how impaired healing causes developmental defects during pregnancy. This model also provides a platform for testing interventional strategies. Our model allows researchers to study how the uterus heals, how defects arise in an injured uterus, what changes are present at the scar, and why some embryonic defects occur even in the uninjured uterine horn.

We will investigate how injuries lead to embryo implantation failure, how embryos resorb at the scar, and why only injuries during the later phases of the estrous cycle lead to defects, like embryo mispacing.

[Instructor] To begin, prepare the preoperative area. Cover an anesthetized animal with a sterile drape, exposing only the snout. Use a pair of straight or curved iris scissors to cut a two-to-three-millimeter incision in the dorsal skin, while holding the skin with fine forceps. Cut a two-to-three millimeter incision in the fascia overlaying the ovarian fat pad. Gently grip the ovarian fat pad with forceps and extract it from the fascia and skin incisions. After exposing the upper 1/3 of the uterus, gently secure the uterotubal junction with forceps. Then use a bird needle to create a small hole at the top of the uterus. Then insert the needle and carefully scrape the antimesometrial surface of the uterine horn. Continue scraping until both the endometrial and myometrial layers are fully perforated. Now, gently return the injured uterine horn to the body cavity using forceps. Suture the fascia closed with Size 4-0 suture and remove any excess suture. Close the skin incision using a clip from a skin clip applicator. A uterine wound at three days post-injury showed an open lesion with the uterine lumen visibly exposed. At one month post-injury, the uterine wound had closed with minimal visible scarring at the prior injury site. Injured uterine horns showed resorbing embryos and intrauterine bleeding, visible as darkened areas and hemorrhage. A normal implantation outcome featured a single placenta and embryo clearly separated within the uterine horn. Uterine injury resulted in close pairs of embryos with fused placenta, illustrating embryo mispacing. A mispaced embryo pair displayed one underdeveloped embryo and a normal amniotic sac, reflecting adverse developmental outcomes.