Ovarian Autotransplant in the Domestic Sheep: A Translational Model for Novel Organ Preservation Technologies

Presenter: Stone Van Slooten, University of Minnesota-Experimental Surgical Services

Introduction: For girls afflicted with cancer, oncofertility is often a secondary, but important concern. Advancements in the field of organ preservation may make the ability to harvest, preserve, and later transplant ovaries following a course of gonadotoxic treatment, such as chemotherapy, a promising option for these patients. As such, in vivo animal models are necessary to test novel organ preservation technologies prior to clinical use. In preparation of the testing and evaluation of such technologies, we sought to develop a reproducible approach for ovarian autotransplantation in the domestic sheep model.

Methods: Seven adult, non-pregnant ewes of domestic breed were selected for surgery. On day of surgery, animals underwent multimodal sedation using ketamine (10 mg/kg, IM) and propofol (4 mg/kg, IV), intubation with an appropriate-size endotracheal tube, and were placed on mechanical ventilation with isoflurane inhaled anesthetic (3%) in the operating room. Surgical access was gained via midline laparotomy. The left ovary was located, and its ovarian pedicle dissected away from the surrounding tissue. A section of non-tortuous ovarian vasculature was chosen for transverse arteriotomy and venotomy. Once removed from the abdomen, the harvested ovary’s artery was catheterized under microscope visualization and flushed with cold lactated ringers. The right ovary was then explanted in the same manner as before. The left ovary was re-implanted via anastomosis of the ovarian artery and vein to the contralateral remaining segment of the right ovarian artery and vein. Upon completion of the anastomoses, the incision site was closed, animals were weaned from anesthesia, and were transferred to postoperative housing and recovered. Pain was managed through the combination of extended-release buprenorphine administered approximately 18-24 hours before surgical induction (0.27 mg/kg, SQ) and Carprofen administered upon arrival to post-operative housing following surgery (4 mg/kg, SQ). Transplanted ovary graft viability and function were monitored postoperatively using serum progesterone analysis and noninvasive imaging (Computed tomography; CT).

Results: All seven animals survived the ovarian autotransplant procedure. Three animals died prior to scheduled endpoint: one due to repeat herniation of the innermost abdominal wall layer, another due to uroabdomen that formed as a result of damage to ureters during implant procedure, and one due to factors unrelated to the surgical procedure or transplanted graft. Three of four in life animals are beyond 20 weeks post-transplant at time of submission; detectable progesterone levels were observed in all three animals (>0.15ng/dL). Six of seven animals received a 30-day postoperative arterial phase contrast CT scan; patency of vasculature distal to the site of anastomoses was confirmed and the ovarian graft appeared to be receiving blood flow for these six animals.

Conclusion: This study developed a robust framework for ovarian autotransplant in a large animal model. Throughout the initial stages of this study, refinements were made to address the surgical challenges present. The results of this study indicate successful transplanted ovarian graft function in adult sheep. These techniques and results can be implemented in future studies that wish to test novel ovarian preservation techniques.