Despite the availability of assistive solutions such as egg freezing and artificial insemination, researchers are focusing on understanding the root cause of declining fertility in order to find ways to slow it down.
The study says that a woman's fertility begins to decline after the age of 32, as the rate of deterioration in egg quality accelerates significantly.
The study, conducted by researchers at Guilin University in China, analyzed data from over 15,000 embryos resulting from in vitro fertilization (IVF). The findings revealed that approximately 20% of eggs carrying chromosomal abnormalities are found in women between the ages of 20 and 32, and this percentage exceeds 50% after the mid-thirties, with the risk continuing to rise year after year. This increases the risk of miscarriage, infertility, and having children with Down syndrome as the mother's age advances.
Researchers attribute this phenomenon to a critical decline in levels of the vital protein "cohesin," which is similar to the molecular glue responsible for the cohesion and integrity of chromosomes within the egg.
As women age, its quantity decreases by up to a third in the eggs of women over forty compared to the eggs of women in their twenties.
Experiments on mice showed that more than 95% of this protein disappeared by an age equivalent to the late thirties in humans.
A deficiency in cohesin leads to premature separation of chromosomes and their movement to the wrong locations, resulting in eggs with an abnormal number of chromosomes.
Protein also plays a vital role in repairing DNA damage. Low levels of protein lead to the accumulation of damage and an increase in genetic errors, which may raise the risk of cancer and developmental problems in fetuses.
The exact reason for the decline of cohesin with age is still being investigated, but hypotheses attribute it to the erosion of its protective proteins over time, the effect of oxidative stress, and the weakening of cellular signals responsible for stabilizing it in older eggs.
Scientists are currently focusing on two key molecular pathways that have revealed their crucial role in this process:
1. The mTOR pathway: This pathway controls cell growth and cohesin binding. Research in yeast suggests that modifying this pathway can boost cohesin levels, although the effectiveness of this approach in humans remains uncertain and requires further investigation.
2. The ATM pathway: This pathway is responsible for coordinating DNA repair and helping cohesin maintain chromosome integrity. As eggs age, this pathway becomes significantly less efficient, accelerating cohesin protein loss and deepening genetic damage.
The researchers recommend studying these two pathways carefully as a step towards developing future treatments to preserve egg quality and prolong a woman's natural fertility.
