If true, finding could lead to new fertility treatments

By Tina Hesman Saey

Web edition: December 13, 2012
Print edition: December 29, 2012; Vol.182 #13 (p. 23)

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Credit: Courtesy of Katsuhiko Hayashi/Kyoto Univ.

2012 SCIENCE NEWS TOP 25: 8

For more than 50 years the matter had been considered settled: A woman grows all the eggs she will ever have before she is even born. But a study published this year, and then contested, suggests that this long-accepted fact may not be true.

Stem cells in the ovaries of both women and mice replenish egg supplies throughout adulthood (SN: 4/7/12, p. 8), reported a team led by Jonathan Tilly, a reproductive and developmental biologist at Massachusetts General Hospital. With aging, the stem cells’ capacity to make eggs diminishes, eventually petering out at menopause, Tilly says.

Many people hailed the news because it raises the possibility of growing eggs in laboratory dishes for use in fertility treatments. That possibility came a bit closer to reality when Japanese scientists announced that they had grown viable mouse egg cells (some shown above), or oocytes, in the lab from embryonic stem cells and from reprogrammed stem cells (SN: 11/3/12, p. 14).

Tilly says harnessing the stem cells he and his team found may not only be a boon for those with fertility problems, but also might help delay menopause.

But a follow-up study called Tilly’s results into question. Kui Liu of the University of Gothenburg in Sweden and colleagues reported that they had found ovarian cells that might be mistaken for stem cells but produce no eggs (SN Online: 7/9/12). Other scientists familiar with Tilly’s work say that the Swedish group isolated a different type of cell, and failed to find the stem cells.

Some scientists doubt that stem cells, even though probably real, would actively produce oocytes in the body. Evelyn Telfer of the University of Edinburgh has worked with Tilly’s stem cells and says that she thinks the cells may spring into action if the ovary is damaged, but otherwise sit quietly.

While the scientific debate continues, Tilly has formed a start-up company, OvaScience, that is using his work on egg precursor cells to develop treatments for infertility.

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