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The start of a reproductive revolution?
A novel technique to “rejuvenate” human eggs may dramatically improve IVF success rates in older women, scientists say.
“We have been able to achieve the first rejuvenation of a human egg in vitro. What this means is we could reduce the fraction of eggs with genetic defects,” Dr. Agata Zielinska, a co-founder and co-chief executive of Ovo Labs, which wants to commercialize the treatment, told BBC Radio 4’s Today.
“If this could then be translated to the clinic, this could potentially be the biggest improvement in IVF success rates of the last decade,” she continued.
Poor egg quality is the primary cause of IVF failure and miscarriage in older women. As women age, their eggs are more prone to chromosomal errors — this new approach seemingly reverses age-related defects.
The Ovo Labs team gave donated eggs microinjections of the protein Shugoshin 1, which protects chromosomes. Those eggs were nearly half as likely to have a defect as untreated eggs.
“Overall, we can nearly halve the number of eggs with [abnormal] chromosomes. That’s a very prominent improvement,” said Melina Schuh, a director at the Max Planck Institute for Multidisciplinary Sciences in Germany, according to The Guardian.
“Most women in their early 40s do have eggs, but nearly all of the eggs have incorrect chromosome numbers,” added Schuh, who is also a co-founder of Ovo Labs. “This was the motivation for wanting to address this problem.”
Previous research found that in women ages 20 to 32, about 1 in 5 eggs has a chromosome error.
By a woman’s mid-30s, more than half of her eggs contain too many or too few chromosomes — a leading cause of miscarriage, infertility and conditions like Down syndrome. And with each passing year, the risk of chromosomal abnormalities continues to rise.
Experts maintain that this sharp decline in egg quality accounts for the relationship between advancing age and a drop in IVF success rates.
“Currently, when it comes to female factor infertility, the only solution that’s available to most patients is trying IVF multiple times so that, cumulatively, your likelihood of success increases. What we envision is that many more women would be able to conceive within a single IVF cycle,” said Zielinska.
The method targets aneuploidy, an abnormal number of chromosomes, which stems from errors during meiosis.
Meiosis is a process that aims to ensure that the resulting zygote gets the proper number of chromosomes when the sperm fertilizes the egg.
Unfortunately, with older eggs, the proteins that form the “glue” holding the chromosome pairs can degrade over time, leading to aneuploidy.
Schun and her team found that microinjections of Shugoshin 1 into mouse and human eggs can help keep chromosome pairs together.
Eggs showing a defect decreased from 53% to 29%, and in women over 35, from 65% to 44%.
“What is really beautiful is that we identified a single protein that, with age, goes down, returned it to young levels, and it has a big effect,” said Schuh. “We are just restoring the younger situation again with this approach.”
She notes, however, that the approach would not extend fertility beyond menopause, when egg reserves run out.
The findings were presented last week at the British Fertility Conference in Edinburgh.
Schuh and her team do not anticipate safety issues and are in talks with regulators about testing their technique in clinical trial.
Experts maintain that a crucial question will be whether this improvement in egg quality translates into embryos with fewer genetic errors.
