Scientists have a new theory about why a woman’s fertility declines after her mid-30s. They also suggest an approach that might help slow the process, enhancing and prolonging fertility.
The study supported by the National Institutes of Health found that as women age, their egg cells become riddled with DNA damage and die off because their DNA repair systems wear out.
Researchers found that the activity of four DNA repair genes (BRCA1, MRE11, Rad51 and ATM) declined with age.
When the research team experimentally turned off these genes in mice, the egg cells had more DNA breaks and higher death rates than did egg cells with properly working repair systems.
The new study suggests that finding ways to bolster DNA repair systems in the ovaries might lead to treatments that can improve or prolong fertility.
Defects in one of the DNA repair genes - BRCA1 - have long been linked with breast cancer, and now also appear to cause early menopause, researchers said.
In general, a woman’s ability to conceive and maintain a pregnancy is linked to the number and health of her egg cells. Before a baby girl is born, her ovaries already contain her lifetime supply of egg cells. As she enters her late 30s, the number of egg cells - and fertility - drops dramatically. By the time she reaches her early 50s, her original ovarian supply of about one million cells drops virtually to zero.
The findings appear in Science Translational Medicine.