Researchers presented at the Fertility 2026 conference in Edinburgh, Scotland, evidence that the reduction of a specific protein contributes to egg deterioration with age in women. The study, not yet peer-reviewed, suggests restoring this protein could improve egg quality in in vitro fertilizations. Experts view the work as a promising step, though it won't resolve all infertility cases.
Scientists are advancing in understanding the decline in female fertility with age, a central mystery in human reproduction. Presented at the Fertility 2026 conference in Edinburgh, the study led by Melina Schuh from the Max Planck Institute and Agata Zielinska, co-founder of Ovo Labs, identified the drop in Shugoshin protein levels as a key factor. This protein, whose Japanese name means 'guardian spirit,' protects cohesion proteins that hold chromosomes together in eggs.
Women are born with a lifetime stock of oocytes, about 7 million in the fetus and 1 million at birth, which remain paused for decades until ovulation. During this wait, paired chromosome copies can separate prematurely, leading to aneuploidy — wrong number of chromosomes —, the main cause of infertility and IVF failures. 'This creates huge problems at the chromosomal level, because they kind of wait for years in humans, which is insane in a way,' explains Paula Cohen, director of the Center for Reproductive Sciences at Cornell University.
In experiments with mouse and human cells, restoring Shugoshin via messenger RNA increased eggs with intact chromosomes from about half to nearly three-quarters. 'If you want to develop strategies to improve egg quality and create clinical ways to really help couples conceive, you need to understand what's going wrong at the molecular level,' says Zielinska.
Independent scientists, like Michael Lampson from the University of Pennsylvania, note that prior focus was on cohesin proteins, but protecting the remaining ones makes sense. Binyam Mogessie from Yale observes partial recovery and plans drug tests. Cohen warns it won't solve everything: 'This won't solve the problem for everyone... but we're much further along than just 10 years ago.' Ovo Labs plans a clinical trial to test the intervention in IVF, while another study in Nature Aging simulates aging in mouse eggs to probe failures.
