In previous blogs, we discuss some of the currently available techniques in oncofertility, including sperm banking for men and ovarian tissue cryopreservation (OTC) for women. As one of the newer techniques, OTC allows women to have their ovaries removed, cryopreserved, and then reimplanted later. This is an advantage over older techniques because ovarian removal takes a few short hours and women can start cancer treatment immediately after fertility preservation.
However, ovarian tissue cryopreservation may not be appropriate for women with pelvic or blood-born cancers because reimplanting the ovary may also reintroduce the cancer. Scientists at the Oncofertility Consortium and elsewhere are trying to develop additional fertility preservation techniques and a recent article in the Proceeds of the National Academy of Sciences describes an advance in that field. A group at Stanford University was investigating the role of a molecule called PTEN, which regulates cell division and growth, when they discovered that PTEN might prevent the development of cells within an ovary.
This group found that when PTEN was inhibited with a drug, primordial mouse oocytes (immature eggs) began to develop in culture. The oocytes were then reimplanted in a female mouse and treated with hormones that are known to stimulate further egg development. Mature oocytes were then removed and fertilized with in vitro fertilization (IVF). These embryos were then implanted into female mice and produced more than 20 mouse pups.
The Stanford study, lead by Aaron J.W. Hsueh, PhD, indicates that PTEN inhibition is important for an oocyte to mature into an egg ready for fertilization. Armed with this information, scientists may be able to mature primordial oocytes from cryopreserved ovaries of fertility preservation patients and grow them to maturation. Once a cancer survivor is ready to have a biological child, the mature egg can be fertilized through IVF and the resulting embryo transferred into the woman’s uterus, with no risk of reintroducing the cancer. While in vitro maturation, as this technique is called, is still being explored, it may someday provide childbearing options for women who preserved their fertility.