A groundbreaking experimental form of in vitro fertilisation (IVF) has successfully led to the birth of healthy lambs by maturing highly immature eggs in a laboratory setting. This marks the first time such an approach has been demonstrated in a large animal, offering significant promise for improving human fertility treatments and increasing IVF success rates. The research, presented by Professor Helen Picton from the University of Leeds, UK, at the European Society of Human Reproduction and Embryology conference in London on 7 July, suggests a potential paradigm shift in fertility care.
Standard IVF typically involves a course of daily injections over one to two weeks to stimulate the ovaries, aiming to produce around 10 mature eggs. Of these, generally six to eight are successfully fertilised in a lab. However, the overall live birth rate from standard IVF remains relatively low, at approximately 20 per cent. This new research focuses on harnessing the vast reserve of immature eggs women are born with, which number in the hundreds of thousands to over a million, but decline throughout life.
In the study, Professor Picton and her team collected dozens of follicles containing immature eggs from sheep. These follicles were then treated with a carefully formulated cocktail of reproductive hormones, including follicle-stimulating hormone, and growth factors. This method successfully coaxed about 60 per cent of the immature eggs to develop into mature ones. Approximately 30 per cent of these matured eggs were then successfully fertilised to create embryos. These embryos were implanted into 18 ewes, leading to the birth of a female lamb in early 2024, followed by four more lambs this year. Notably, the initial female lamb born also went on to have two lambs this year, demonstrating the viability of the offspring.
Experts, such as Stine Kristensen from Copenhagen University Hospital in Denmark, who was not involved in the research, have hailed this as a major breakthrough, particularly noting that sheep reproduction closely mirrors that of humans, more so than mice where similar successes were achieved over 30 years ago. While the technique is unlikely to become a routine first-line treatment due to its more invasive nature compared to standard IVF, it holds immense potential for specific patient groups.
Professor Picton highlighted that women whose ovaries have suffered damage from cancer treatment could significantly benefit. Currently, fertility preservation for these patients often involves removing and freezing ovarian tissue, which is then re-transplanted. However, this carries a risk of reintroducing cancer cells. Collecting immature eggs, as demonstrated in this study, would circumvent this risk, as cancer typically affects only the surrounding tissue and not the immature eggs themselves. The next crucial step involves exploring whether human eggs can be successfully fertilised using this approach, with studies expected in the coming years. If successful, small human trials could follow, though ethical approval for such research could take five to ten years to ensure the benefits outweigh any potential risks to future parents or children.