It has taken decades of work, but scientists can now grow eggs to maturity outside of the ovary. It requires carefully controlling laboratory conditions including oxygen levels, hormones, proteins that simulate growth and the medium in which the eggs are cultured.
In previous studies, scientists had developed mouse eggs to produce live offspring, and had matured human eggs from a relatively late stage of development. The latest study is the first time a human egg has been developed in the lab from its earliest stage to full maturity. Still unclear is whether the resulting eggs, which reached maturity in just 22 days, compared with 5 months in the body, are normal and whether they can combine with sperm to make a healthy embryo.
The advance could safeguard the fertility of girls with cancer ahead of potentially harmful medical treatment, such as chemotherapy. Immature eggs recovered from patients’ ovarian tissue could be matured in the lab and stored for later fertilisation. Conventionally, cancer patients can have a piece of ovary removed before treatment, but reimplanting this tissue can risk reintroducing cancer. The study has also given insight into how human eggs develop at various stages, which could aid research into other infertility treatments and regenerative medicine.
But while the scientists have shown it is possible, it is very inefficient with only 10% of eggs completing their journey to maturity. Experts said it was an exciting breakthrough, but more work was needed before it could be used clinically.
Research article: Molecular Human Reproduction