Infinite eggs?

The ovaries of adult mice contain egg-generating germ cells, scientists revealed at the European Society for Human Reproduction and Embryology's annual conference. The results have prompted hopes of a treatment for women with few eggs, such as those treated for cancer or nearing menopause.

The discovery had been published in a March edition of Nature, but many scientists remained unconvinced, as the research team were unable to isolate the egg-producing cells. Jonathan Tilly, who led the researchers, told the conference that they have since extracted 150 to 200 of these cells from a single mouse ovary. Genetic markers displayed by these cells identify them as the type of cells capable of producing eggs.

The researchers, a combined team from Harvard Medical School and Massachusetts General Hospital, also found a gene that controls the activity of the germ cells. Mice with this gene removed had 40 per cent more egg-nourishing follicles by the time they reached adulthood. A molecule called GSA-8 can be used to regulate the gene; prepubescent mice injected with the drug had nearly double the number of follicles when they reached puberty.

Other animals, including fruit flies, birds and fish, are known to maintain their egg-producing ability throughout life. If this faculty is found in humans, it will be something of a paradigm shift for those in the field of human reproduction, who have long believed women are born with a finite supply of eggs. Tilly believes the results make sense from an evolutionary perspective, posing the question: 'Why would Mother Nature put all her eggs in one basket when they would just sit there and accumulate DNA-related damage?'