The research, led by scientists at the University of Cambridge, found that exposure of fetuses to chronic hypoxia (low oxygen levels) during development led to them having advanced aging of the ovary and fewer eggs available.
Hypoxia in the uterus can be caused by several factors, including smoking, pre-eclampsia, maternal obesity, and life at high altitudes. The condition is already known to have potential long-term effects on the health of offspring, including increased risk of heart disease. However, this study, published in The FASEB Journal, is the first time it has been shown to affect fertility.
To investigate the effects of hypoxia, researchers at the University of Cambridge's Metabolic Research Laboratories placed pregnant rats at reduced oxygen levels (13%, compared to 21% found in the air) from the sixth to the 20th day of pregnancy. . They then examined the reproductive tract of their female pups at four months of age.
Mice are a useful model for studying pregnancy. As a mammal, their bodies and the underlying biology share some important similarities with those of humans. However, their gestation period and life cycles are much shorter than those of humans, making them an ideal animal model for studying pregnancy and fetal development.
When the team examined the pups, they found a decrease in the number of ovarian follicles in the reproductive tract. Females are born with a fixed number of follicles, each with the potential to turn into an egg. In humans, women usually spend all their eggs by age 50 when they enter menopause.
The researchers also looked at the length of the telomeres in the ovarian tissue of the pups. Telomeres are found at the end of the chromosomes and prevent the chromosome from deteriorating – they are often compared to the plastic that seals the end of the laces. As we age, telomeres become shorter and shorter, and therefore their length can be used as a proxy for measuring aging. The researchers found that the telomeres in the ovarian tissue of puppies exposed to hypoxia were shorter than in unexposed pups.
"It's as if low oxygen levels make the woman's ovarian tissue age faster," says Catherine Aiken of the University of Cambridge. "Biologically, the tissue looks older and the female runs out of eggs – in other words, it becomes infertile – at a younger age."
Although the research was conducted on rats, Dr. Aiken says there are many reasons to hope that the findings can be translated to humans, as previous studies on hypoxia during pregnancy in relation to other conditions such as heart disease have shown to be relevant . humans.
While women are advised not to smoke during pregnancy, other causes of hypoxia, such as pre-eclampsia and life at high altitudes, are out of their control. However, says Dr. Aiken, her team's research findings may be helpful for women who were exposed to low levels of oxygen during their mother's pregnancy.
"Now that we have seen a link between hypoxia and fertility problems in rats, we know what to look for in women," she says. "If it turns out to be true for them, then at-risk women will be able to act: having children earlier or looking for assisted reproduction, such as IVF, there should be no reason for these women not to have children. .
Dr. Aiken is also involved in research into whether anti-oxidant medication can help undo any damage caused by hypoxia.
This article has been republished from materials provided by the University of Cambridge. Note: Material may have been edited for length and content. For more information, please contact the cited source.
Aiken, CE et al. Chronic gestational hypoxia accelerates ovarian aging and decreases ovarian reserve in next-generation adult rats. FASEB; March 27, 2019; DOI: 101096 / f.201802772R.