Biological clock may carry on ticking
Female mice can produce new eggs into adulthood and are not born with a limited number as previously thought, say U.S. scientists.
Researchers at Harvard Medical School have therefore questioned the common view that the number of female eggs was fixed at birth and declined with age.
If scientists can show the same holds true in humans, it would transform our view on how ovaries form, function and fail. It could also pave the way for methods to maintain, prolong and restore female fertility.
The researchers published their results in today's issue of the journal Nature.
Reproductive biologist Associate Professor Jonathan Tilly was one of the team to discover mice cells that regenerated and maintained the function of the ovaries.
"If these cells are indeed proven to exist in humans this opens up numerous possibilities, for example preserving fertility in cancer patients post therapy by stem cell transplantation and postponing the natural time of menopause," he said.
Isolating, storing and then transplanting the cells could potentially enable cancer patients whose ovaries have been damaged by treatment to have children.
Women could also bypass the decline in fertility they normally experience in their 30s and 40s.
"These cells can be transplanted back into a woman's own ovaries and essentially regrow her ovaries," he said.
Tilly's team discovered the mouse cells after measuring the number of healthy and dying follicles, or sacs in which the eggs mature, in mice throughout their lives.
Despite a high rate of follicle loss, the female mice had healthy eggs longer than the scientists had expected, which led them to suspect that the ovary could make new follicles and eggs.
Tilly and his colleagues are now trying to identify the specific characteristics of the unique cells, thought to be stem cells within the ovary, to determine if they exist in humans.
"Once that is done, and we feel with every confidence that it will be done, you can almost envision immediate application because it is the patient's own cells," he said
Dr Marian Damewood, the president of the American Society for Reproductive Medicine, said if scientists could postpone ovarian failure in humans it could be the most significant advance in reproductive medicine since the advent of in vitro fertilisation more than 25 years ago.
"This is very exciting work," Damewood said. "If subsequent research confirms this finding, it will force us to re-examine what we had considered a fundamental fact in reproductive biology."