“Scientists claim to have ‘rejuvenated’ human eggs for the first time in an advance that they predict could revolutionise IVF success rates for older women.

The groundbreaking research suggests that an age-related defect that causes genetic errors in embryos could be reversed by supplementing eggs with a crucial protein…

The decline in egg quality is the main reason IVF success rates drop steeply with female age and is why the risk of chromosome disorders such as Down’s syndrome increases with maternal age…

The latest approach targets a vulnerability in eggs linked to a process called meiosis, in which sex cells (eggs or sperm) jettison half their genetic material so they can join together to make an embryo.

In eggs, this requires 23 pairs of X-shaped chromosomes to align along a single axis in the cell. On fertilisation, the cell divides causing the chromosome pairs to be – ideally – neatly snapped down their centres to create a cell with precisely 23 single chromosomes from the mother, the rest being delivered by the sperm.

However, in older eggs the chromosome pairs tend to loosen at their midpoint, becoming slightly unstuck or detaching entirely before fertilisation. In this scenario, the X-shaped structures fail to line up properly and move around chaotically in the cell, so when the cell divides they are not snapped symmetrically. This results in an embryo with too many or too few chromosomes.

Schuh and colleagues previously found that a protein, Shugoshin 1, which appears to act as a glue for the chromosome pairs, declines with age. In the latest experiments in mouse and human eggs, they found that microinjections of Shugoshin 1 appeared to reverse the problem of chromosome pairs separating prematurely.

Using eggs donated by patients at the Bourn Hall fertility clinic in Cambridge, they found that the number showing the defect decreased from 53% in control eggs to 29% in treated eggs. When they looked only at eggs from women over 35 years of age, a similar trend was seen (65% compared with 44%), although this result was not statistically significant, which the scientists said was probably due to them only having treated nine eggs in this age range.”

From The Guardian.