An ovary transplant is a medical procedure designed to restore ovarian function, including hormone production and fertility. This involves transplanting ovarian tissue, typically containing immature eggs, into a recipient. The goal is to allow the transplanted tissue to re-establish its biological activity, leading to the return of natural menstrual cycles and the potential for spontaneous conception. This procedure offers a pathway for individuals who have experienced, or are at risk of, ovarian failure, to regain their reproductive and endocrine capabilities.
Medical Indications for an Ovary Transplant
Ovary transplants are considered for individuals facing medical treatments that threaten reproductive health. Chemotherapy and radiation therapy for cancer are common reasons, as these treatments can damage ovaries and lead to premature ovarian failure. For pre-pubertal girls, ovarian tissue cryopreservation and subsequent transplantation represent the only available option for fertility preservation before puberty.
The procedure also benefits patients with non-malignant conditions that risk ovarian damage. These include certain autoimmune diseases, such as systemic lupus erythematosus or inflammatory bowel disease, which may require cytotoxic therapies. Individuals with blood disorders like sickle cell anemia or thalassemia major, often undergoing bone marrow transplantation, may also be candidates. Premature ovarian insufficiency (POI), defined as ovarian function loss before age 40, is another indication, whether caused by genetic factors or other medical conditions.
The Transplant Process
The ovary transplant process begins with harvesting ovarian cortical tissue, typically through a minimally invasive laparoscopic procedure. During this surgery, a portion of the ovary, or sometimes the entire ovary, is removed. The outer layer, or cortex, of the ovary contains the primordial follicles, which house immature eggs.
Once harvested, ovarian cortical tissue is prepared for cryopreservation, a freezing technique that preserves its viability. Two common methods for cryopreservation are slow freezing and vitrification, both aiming to prevent ice crystal formation that could damage the delicate tissue. The frozen tissue strips are then stored in specialized long-term facilities until the patient is ready for transplantation.
When transplantation is desired, the cryopreserved tissue is thawed and surgically re-implanted. Autotransplantation, where the patient receives her own harvested tissue, is the most common approach. Allotransplantation, involving tissue from a donor, is far less common due to the need for lifelong immunosuppression to prevent rejection. The tissue can be placed in two main ways: orthotopic transplantation involves grafting the tissue back into the pelvic cavity, often near the remaining ovary or in its original location. Heterotopic transplantation places the tissue in other sites, such as the abdominal wall or forearm, offering easier monitoring but usually requiring assisted reproductive technologies for conception.
Post-Transplant Outcomes
Following a successful ovary transplant, the goal is the restoration of endocrine function. This involves the return of hormone secretion, leading to the resumption of regular menstrual cycles. Many patients experience the alleviation of menopausal symptoms, such as hot flashes and mood changes, as their bodies begin producing hormones like estradiol again. Ovarian function and follicular growth have been observed in 70% or more of patients who undergo ovarian tissue transplantation.
Beyond hormonal benefits, the procedure aims to restore fertility. Spontaneous pregnancies are possible after orthotopic transplantation. Studies indicate that pregnancy has been reported in about 52% of patients after ovarian tissue transplantation. Over 250 children have been born globally as a result of this procedure. Even if spontaneous pregnancy does not occur, the restored ovarian function makes assisted reproductive technologies, such as in vitro fertilization (IVF), a viable option, using eggs matured within the transplanted tissue.
Potential Complications and Considerations
A concern with ovary transplantation, particularly in cancer survivors, is the risk of reintroducing malignant cells. If cancerous cells were present in the ovarian tissue before it was harvested and cryopreserved, they could potentially survive the freezing process and lead to disease recurrence upon transplantation. This risk is considered higher for certain cancers, such as leukemia, where malignant cells are more likely to be disseminated throughout the body.
To mitigate this risk, pre-implantation analysis of the cryopreserved tissue is performed using highly sensitive techniques to detect any minimal disseminated disease. Despite these precautions, graft failure, where the transplanted tissue does not establish a sufficient blood supply or function, remains a possibility. Surgical risks, including bleeding, infection, or damage to surrounding tissues, are also present. The functional lifespan of transplanted ovarian tissue can also be limited, typically lasting for a few years, after which further transplantation may be considered if additional tissue was cryopreserved.