Awaken 'sleeping' eggs to boost fertility

By Linda Geddes Let sleeping dogs lie, but not sleeping eggs. Dormant eggs in mouse ovaries have been awoken and used to create healthy pups. If the approach works in women it could be used to boost fertility or help those who froze ovarian tissue prior to chemotherapy. Female mammals are born with millions of dormant eggs, but only a small fraction ever mature into cells with reproductive potential. One factor keeping cells in this immature state is the PTEN gene, which suppresses a signalling pathway involved in cell growth. Aaron Hsueh at Stanford University Medical School in California and his colleagues exposed mouse ovaries to a PTEN inhibitor and a molecule that stimulates the signalling pathway that PTEN inhibits. Control ovaries remained untreated. The ovaries were then transplanted back into the mice, and they received a hormone to stimulate egg development. Two weeks later, the treated ovaries contained two to six times as many mature follicles – which have the potential to release mature eggs – as the untreated ones. Twenty healthy mouse pups were born after fertilised eggs from the treated ovaries were implanted into surrogate mothers. Hsueh’s team has used a similar approach to stimulate fragments of human ovarian tissue. When these were implanted into mice, four times as many mature follicles were produced as in controls. But for ethical reasons, the eggs could not be fertilised. It’s an important proof of principle, says Evelyn Telfer of the University of Edinburgh, UK. However, she cautions that maturing the human eggs in mice makes it difficult to assess just how successful the approach would be in humans. Her team is currently using a similar approach to mature human follicles to the point where they release a mature egg – all outside the body. “We can stimulate follicle development, isolate and grow the eggs to quite an advanced stage, but we haven’t been able to fertilise them,” she says – also for ethical reasons. Telfer’s team hasn’t yet published its results. Journal Reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1001198107 More on these topics:
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