A single injection into human eggs can significantly reduce the risk of chromosome errors that lead to miscarriage, IVF failure, and conditions such as Down's syndrome, new research has shown. The technique, which involves delivering the genetic code for a key protein, could eventually improve fertility outcomes for older women.
Presented at the European Society of Human Reproduction and Embryology conference in London on 6 July, the study was led by Dr Agata Zielinska of Ovo Labs, a biotechnology company in Germany. The research focused on aneuploidy—a condition where eggs contain too many or too few chromosomes. Aneuploidy affects 10 to 25 per cent of eggs in women in their early 30s, rising to more than 65 per cent by the late 30s.
The team found that levels of a protein called shugoshin-1 are substantially lower in older mouse and human eggs. This protein normally maintains the 'molecular glue' that holds paired chromosomes together during meiosis. When it degrades, chromosomes can separate prematurely, leading to uneven distribution. To test whether replenishing the protein could help, the researchers collected 111 immature eggs from over 30 women aged 22 to 43 who were undergoing egg banking or IVF. They injected mRNA coding for shugoshin-1 into some eggs, leaving others untreated as controls.
Results showed that premature chromosome separation occurred in 53 per cent of untreated eggs, but only 29 per cent of treated ones—a reduction of nearly half. Among eggs from nine donors over 35, aneuploidy rates fell from 65 per cent to 44 per cent, though this difference was not statistically significant due to the small sample size. In separate mouse experiments, treated eggs were successfully fertilised and produced healthy offspring with no observed side effects.
Marcos Iuri Roos Kulmann at Nilo Frantz Reproductive Medicine in Brazil, who was not involved in the study, described the findings as 'a big deal', noting it is the first therapy to show such clinical potential for correcting a major cause of IVF failure. The research is yet to be peer-reviewed, but the team plans further studies to confirm safety and efficacy before human clinical trials can begin.