Ovarian transplant procedures involve transferring ovarian tissue to restore ovarian function, offering new possibilities for individuals facing fertility and hormonal health challenges due to medical conditions or treatments. This intervention aims to re-establish natural hormonal cycles and potentially fertility.
What is an Ovarian Transplant?
An ovarian transplant involves transferring ovarian tissue, or in rare cases, an entire ovary, from one individual to another, or more commonly, within the same individual. Its primary goal is to restore ovarian functions: hormone production and fertility. Unlike other assisted reproductive technologies like in vitro fertilization (IVF), ovarian transplantation aims to revive the natural physiological environment of the ovary. This includes resuming menstrual cycles and enabling natural conception.
The most common form is autotransplantation, where a woman’s own previously cryopreserved (frozen) ovarian tissue is re-implanted. This approach eliminates the need for immunosuppressive drugs, typically required in donor organ transplants, because the body recognizes its own tissue. The transplanted tissue, particularly the outer layer of the ovary (cortex), contains numerous immature egg cells (follicles) that can mature once re-established and revascularized.
Why Ovarian Transplants Are Performed
Ovarian transplants address compromised or failed ovarian function. Commonly, they address the impact of cancer treatments like chemotherapy and radiation therapy. These life-saving treatments can damage ovarian egg cells and hormone-producing tissues, leading to premature ovarian failure and infertility. For these patients, cryopreservation of ovarian tissue before treatment, followed by transplantation, preserves reproductive potential.
Another reason is premature ovarian insufficiency (POI), where ovaries stop functioning normally before age 40. POI can result from genetic conditions, autoimmune disorders, or unknown causes, causing hormonal deficiencies and infertility. In such cases, a fresh ovarian tissue transplant, sometimes from an identical twin, has restored both hormonal function and fertility.
It is also an important option for pre-pubertal girls with cancer, as ovarian stimulation for egg or embryo freezing is not feasible. Freezing ovarian tissue before puberty allows them to maintain fertility into adulthood. Beyond fertility, the goal is to restore hormone production to prevent menopausal symptoms and support overall health, including bone metabolism and cardiovascular well-being.
The Procedure: What to Expect
The procedure begins with harvesting ovarian tissue. This is done via minimally invasive laparoscopic surgery, where a small incision, usually near the navel, removes a portion of one ovary. The outer layer of the ovary, the cortex, which contains the majority of immature egg cells, is then separated and cut into small strips. These fragments are then cryopreserved, often using a slow-freezing protocol, and stored in liquid nitrogen for future use.
For transplantation, the cryopreserved tissue is thawed. Re-implantation can occur in various sites. The most common approach, orthotopic transplantation, grafts the tissue into the pelvic area, often onto the remaining ovary or a specially created peritoneal pocket near the fallopian tubes. This location allows for natural conception.
Alternatively, heterotopic transplantation places tissue in other accessible body sites, such as the forearm or abdominal wall. While this can restore hormone production, it typically requires in vitro fertilization for conception.
Thawed ovarian tissue strips are reconstructed, sometimes attached to a biodegradable scaffold, and then transplanted. The process is similar to skin grafting, relying on surrounding blood vessels to re-establish blood supply over several days. Recent advancements include robotic surgery, offering enhanced precision and gentle tissue handling during re-implantation. The entire process, from harvesting to re-implantation, aims to maximize the viability of ovarian follicles and promote successful restoration of ovarian function.
Restoring Function and Future Possibilities
Following a successful ovarian transplant, patients experience restored ovarian function. This includes the resumption of regular menstrual cycles, usually within 14 to 25 weeks after the procedure. The transplanted tissue begins producing essential hormones like estrogen, leading to a decrease in follicle-stimulating hormone (FSH) levels, indicating renewed endocrine activity. This hormonal restoration can alleviate symptoms associated with ovarian failure, such as hot flashes and bone density loss.
The potential for natural conception is a key outcome of orthotopic ovarian transplantation. Success rates for pregnancy vary, but studies indicate a pregnancy rate around 30-40% and a live birth rate of about 28-34% after cryopreserved ovarian tissue transplantation. Over half of pregnancies after ovarian transplant may result from natural conception, with many women preferring this route. While natural pregnancy is possible, some patients may still opt for or require in vitro fertilization to accelerate the process or if fallopian tubes are not fully functional.
The lifespan of the transplanted ovarian graft can vary, ranging from a few months to several years, with some grafts functioning for up to 10 years. Ongoing research focuses on improving graft longevity and function. Innovations include using human-derived extracellular matrices as scaffolds for the tissue and incorporating pharmacological treatments like estrogen and aspirin to enhance the healing process and graft survival. These advancements aim to expand the applicability of ovarian transplantation and further improve outcomes for individuals seeking to restore their reproductive and endocrine health.