At Howard Hughes Medical Institute (HHMI) Janelia Research Campus, a team of scientists uses a type of roundworm in studying the process of reproductive aging. Their research findings can help experts in understanding the mechanism of reproductive biological clock.
What Is a Reproductive Biological Clock?
The reproductive biological clock is a metaphor used in describing the sense of pressure many women feel to get pregnant while they are at their peak of reproductive years. Human biology dictates that the chances of pregnancy in women decrease with age, since the number of eggs and their viability diminish over time.
According to obstetrician-gynecologist Zain Al-Safi, there are two factors which cause pregnancy rates to diminish as women age. First is the decrease in the availability of eggs. Women are born with all the eggs that they will ever have in their entire lifetime, typically around one or two million. The available eggs gradually decline until the woman reaches the menopausal stage.
The quality of eggs also affects the rate of pregnancy, as the older eggs do not behave as consistently as younger ones. Each egg cell should divide just before ovulation, producing single cells with 46 chromosomes. A woman's age can affect cell division, and the egg may end up having more or less chromosomes. Most of the embryos formed this way will not implant into the uterus, resulting in miscarriage.
A woman's fertility can also be affected by other factors, such as endometriosis, uterine fibroids, and adenomyosis or exposure to treatments like chemotherapy. These conditions are also more likely to happen as women get older.
Understanding Reproductive Aging
Scientists are aware that mitochondria plays an important role in reproduction, particularly in making oocytes or unfertilized egg cells. However, the exact mechanism on how mitochondria affects reproductive aging is not well understood.
Senior group leader Meng Wang led her team in using Caenorhabditis elegans to identify a mitochondrial enzyme which regulates reproductive health. Although these tiny transparent worms seem very different from humans, they have similar reproductive lifespan which makes them a good model in investigating fertility and aging.
The researchers found that a form of the enzyme Mitochondrial Succinyl-CoA Synthetase (SCS) which produces GTP increases in oocytes as they age. Over time, this mitochondria in oocytes cluster around the cell nucleus, in a process controlled by GTP-specific SCS.
By trying to reduce the production of GTP, this clustering is prevented, and the ability of older eggs to become fertilized increases. This also increases the amount of time animals can reproduce, more than doubling the reproductive lifespan in C. elegans.
The HHMI team also revealed that age-associated changes in oocyte mitochondria are modified upon exposure to various strains of E. coli bacteria. These bacteria contain vitamin B12 which regulates GTP levels in mitochondria. As the clustering of the organelles around the nucleus is affected, it can also have an impact on reproductive aging.
The findings of the study do not only provide additional insight about the regulation of reproductive aging in mammals, including humans; it also reveals how genetic and environmental factors affect how long women can reproduce and how healthy their pregnancies could be.
RELATED ARTICLE: Time-Restricted Eating May Adversely Affect Fertility, New Study Says
Check out more news and information on Fertility in Science Times.
!['Cosmic Glitch' in Einstein's Theory of General Relativity Could Be Explained in This New Scientific Tweak [Study]](https://1721181113.rsc.cdn77.org/data/thumbs/full/53435/258/146/50/40/cosmic-glitch-in-einsteins-theory-of-general-relativity-could-be-explained-in-this-new-scientific-tweak-study.jpeg)
