By Amanda Gardner
MONDAY, May 17 (HealthDay News) -- Scientists have found a way to awaken dormant ovarian follicles, possibly making more eggs available for reproduction during a woman's lifespan.
In mice, the technique resulted in live pups. In humans, the technique was successful in producing mature eggs, but those eggs were not fertilized due to ethical concerns.
Assuming the procedure works as well in humans -- and Dr. George Attia, director of the division of reproductive endocrinology and infertility at the University of Miami Miller School of Medicine, believes it holds promise -- more eggs would significantly raise the odds of older or infertile women becoming pregnant.
Cancer patients who have had ovarian tissue frozen prior to chemotherapy, for instance, might benefit, Attia said. Chemotherapy can affect reproductive capabilities.
"It's long-term work to see if this method works as well in humans, although we have already seen it can activate human dormant follicles in our study," said study lead author Jing Li, a postdoctoral fellow at Stanford University Medical School. "We hope that aging women, women who have frozen ovarian tissues prior to undergoing cancer treatments, or women with premature ovarian failure could benefit from our research."
According to background information in the study, which appears in this week's online issue of the Proceedings of the National Academy of Sciences, human ovaries start with about 400,000 follicles each but only about 1,000 follicles are activated each month. The rest remain dormant. By the time of menopause, less than 1,000 follicles remain.
It's not clear why some of the follicles remain dormant, but previous research has shown that the PTEN and PI3K genes are involved.
For the new study, scientists at the Stanford University Medical School, as well as Japan and China, manipulated the PTEN and PI3K proteins to catapult the follicles of neonatal mice out of complacency. The follicles produced mature eggs, which were fertilized and then transplanted into surrogate mother mice. Those fertilized eggs resulted in 20 healthy pups capable of producing offspring themselves.
In ovarian tissue from cancer patients, inhibiting the PTEN gene succeeded in producing mature eggs, but this portion of the experiment was not carried any further. The findings do need to be replicated in non-human primates, the study authors stated.
Also, the method may be useful in endangered species and with "economically important animals." And additional eggs could also be a source of embryonic stem cells, which can have therapeutic potential, the researchers noted.
Visit the American Society for Reproductive Medicine for more on fertility issues.
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