New evidence that mice can renew the eggs in their ovaries has been revealed by US researchers. They have also discovered a drug that can boost the numbers of eggs in the ovaries of mice.If this is shown to also be true of humans, it will overturn decades of dogma that women are born with a finite supply of eggs. It would mean that they make new eggs constantly, rather like the way men make sperm. It would also raise the possibility of developing drugs to protect the fertility of cancer patients or even delay the menopause in healthy women.Jonathan Tilly and his team at Massachusetts General Hospital and Harvard Medical School in Boston published evidence in March suggesting the ovaries of mice contain cells that behave like germ cells - the cells that give rise to the precursors of eggs. Similar cells are found in the testes and are involved in making sperm.At that time, the team had not isolated these cells for detailed analysis – but now they have, announcing the breakthrough at the European Society for Human Reproduction and Embryology conference in Berlin on Wednesday. They harvested between 150 and 200 cells from each adult mouse ovary and found that the cells expressed genes characteristic of stem cells.
