For the first time, scientists have grown human eggs to full maturity in a lab, in a move that could open the doors to new fertility treatments.

This monumental feat was achieved by scientists at the University of Edinburgh in Scotland. Their research is published in the journal Molecular Human Reproduction. A similar venture has previously been achieved with mouse eggs, even using the lab-grown eggs to create live mice offspring. However, even after decades of work, researchers have always struggled with replicating the research with human cells.

The lab-grown human eggs start off life, so to speak, as immature egg cells that were removed from ovarian tissue at their earliest stage of development. Scientists then cultured the immature egg cells in a multi-stage process over a few weeks, sensitively controlling the fine balance of oxygen, hormones, and necessary proteins. This process matured the immature egg cells to the same stage “normal” eggs would be when released from the ovaries.

In theory, this means the eggs would be ready for fertilization and creating life.

Women are born with immature eggs that only develop after puberty. If a girl undergoes chemotherapy, their immature eggs can be damaged, leading them to face infertility issues later on in life. This breakthrough could help tackle that.

“Until now the freezing of ovarian tissue prior to chemotherapy for certain malignancies has required subsequent re-implantation after the disease is in remission," Professor Adam Balen of Leeds Centre for Reproductive Medicine, who was not involved in the study, explained in a statement. "[H]owever this is only feasible if there is no risk of reintroducing the disease that required the sterilising chemotherapy in the first place.” 

The research widens our understanding of the mechanisms of human egg development, also shedding light on to why this process can sometimes go wrong and lead to other problems with fertility.

Independent experts in the field are praising this “impressive” and “exciting" research, but warn it is still in its early days. For one thing, just nine out of 48 eggs completed their journey to full maturity. Additionally, there were problems seen with the polar body, the part of the egg that carries away half of the eggs genetic material, ready for it to be “mixed” with the sperm's half. In the lab-grown eggs, the polar bodies appeared strangely large, perhaps hinting at a problem. Nevertheless, this study appears to be very promising stuff.

“The technology remains at an early stage, and much more work is needed to make sure that the technique is safe and optimised before we ascertain whether these eggs remain normal during the process, and can be fertilised to form embryos that could lead to healthy babies," added Dr Ali Abbara, Senior Clinical Lecturer in Endocrinology at Imperial College London.

“Still, this early data suggests that this may well be feasible in the future.”