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5 July 2006
Teaching Old Ovaries New Tricks 
Researchers from Australia have found that despite their age, female mice have a renewable egg supply in their ovaries. The finding, detailed in the journal Reproduction, could have broad implications for women's fertility treatments. The discovery has sparked controversy among biologists as it challenges the theory - held for more than 50 years - that female mammals are born with only a finite number of oocytes (eggs). In the mammalian ovary, oocytes develop within ovarian follicles. In humans, the eggs are believed to die off from late in fetal life, after birth and into adult life. When egg numbers decline towards zero, females can no longer reproduce - a condition known as menopause. The researchers, Jock Findlay and Jeff Kerr, found that the total number of eggs in young and normal healthy adult female mice does not decline over time, and that the overall egg number is maintained for longer than previously thought. Findlay and Kerr speculate that mice might have a source of renewable oocytes. "The mechanism behind renewable oocytes is still unknown," Findlay said. "Although other scientists have suggested that the new eggs come from stem cells in the bone marrow or the ovary, we really don't know and further experimentation is needed to find out." Kerr stressed that the phenomenon of egg regeneration in mice did not necessarily mean the same happened in humans. "But the mechanism could provide direction for ovarian stem cell research and help women with fertility conditions," he said. Source: Research Australia
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