One Reason for Women’s Declining Fertility with Age
How worms are helping scientists understand exactly how and why a woman’s biological clock winds down.
Painful though it may be to realise it, it seems that fertility in both worms and women declines at a rate that far exceeds the onset of other aging signs. A study was reported in MLA Cell Press (2010, October 17) on work done by Coleen Murphy of Princeton University that suggested that worms’ and humans’ biological clocks may wind down over time for similar underlying reasons.
She said that “For us, what’s most important is that there are so many shared genes involved. This isn’t just about worms and how they reproduce.” Well that’s a relief, but as she freely admits that such commonalities would exist wasn’t obvious as given that reproduction in the nematode worm Caenorhabditis elegans “goes to pot” in a matter of days compared to three decades or more in humans. At least we are being compared to a worm with elegans in its name, so that’s something.
The newfound similarities suggest that studies of worms can provide a window into the ticking of our own biological clocks, and might ultimately point toward ways to preserve fertility in women who plan to delay having children. Given that more women are delaying their families due to work and economic pressures this could be extremely valuable. , the researchers say.
Before you start comparing yourself to a worm, and in my experience most women aren’t too keen on the little wrigglers, then remember there are important differences in human and worm reproduction. For one, the oocytes that are the immature egg cells are continually produced in worms, whereas humans’ total oocyte supply is present at birth. Still, both human and C. elegans females reproduce for about one-third to one-half of their lives and there are similarities in the process by which our oocytes mature.
In humans, reproductive aging takes place a decade or so before the oocyte supply runs out, suggesting that quality, not quantity, is the limiting factor. The question was whether the same is true in worms, and it appears the answer is yes.
Earlier studies found that some long-lived C. elegans mutantsalso show delayed declines in reproduction. The similarities in reproductive aging in worms and humans may allow us to use worms to study this important human problem, enabling the development of therapies to address maternal age-related birth defects and reproductive decline.
An interesting aside, given the number of ‘elderly’ mothers who have sought IVF treatment in the last few years, is that in worms whose reproductive cycle extends beyond their normal lifespan they can still produce eggs but their body has decayed to the point that they can’t actually lay the fertilized eggs. The mothers are killed as a result. The researchers said “It’s like an 80-year-old woman trying to have a baby,” and this is reminiscent of the case of the Indian woman Rajo Devi Lohan. She became the world’s oldest mother to give birth to triplets at the age of 70, but just 18 months after giving birth at the age of 70 she was revealed in June 2010 to be dying as she is too weak to recover from complications after her IVF pregnancy.