Women's ovaries can grow new eggs, study claims

Scientists say they have evidence that new eggs can grow in adult ovaries, something that had previously been considered impossible.

Young female cancer patients who had been treated with the chemotherapy drug ABVD appeared to have double or even quadruple the density of egg follicles compared with healthy women.

'It's a big increase, not just a few. We have no other explanation than that new eggs have been formed,' Professor Evelyn Telfer of the University of Edinburgh told The Guardian.

Chemotherapy drugs can often cause the ovaries to fail, but ABVD does not appear to cause such fertility problems and Professor Telfer set out to discover why. She took biopsies from 11 young female Hodgkin's lymphoma patients and from ten healthy women. Those treated with another chemotherapy drug, OEPA-COPDAC, had fewer follicles than the healthy women, but those treated with ABVD had a much higher density of follicles – similar to what would be seen in the ovaries of prepubescent girls.

The follicles themselves resembled those seen in infant or even fetal ovaries, which Professor Telfer suggests fits with the idea that they may have been newly formed.

'This was something remarkable and completely unexpected for us. The tissue appeared to have formed new eggs. The dogma is that the human ovary has a fixed population of eggs and that no new eggs form throughout life,' said Professor Telfer.

She presented her findings at the annual meeting of the European Society of Human Reproduction and Embryology in Helsinki in July and the research will soon be published in the journal Human Reproduction.

Other scientists have reacted to the research with a mixture of interest and scepticism.

'I think that these findings, and the identification of the mechanisms involved, may pave the way for development of new fertility treatments or extend women's reproductive span by replenishment of the ovaries with new follicles,' Dr Kenny Rodriguez-Wallberg of the Karolinska University Hospital in Stockholm told The Guardian. 'It suggests that the ovary is indeed a more complex and versatile organ than we have been taught, or that we expected, with an inherent capacity of renewal.'

But Professor David Albertini of the Center for Human Reproduction in New York suggested that other explanations for the results were possible – such as the eggs splitting in two, or rising to the surface of the ovary as a result of stress caused by the chemotherapy.

Professor Nick Macklon at the University of Southampton told The Guardian that the work 'raises more questions than it answers'.

'The slight worry is that clinicians are very quick to pick up anything that will improve IVF,' he said. 'There’s no evidence at this stage that these drugs would improve the odds for people who are having a poor response to IVF drugs.'

Professor Telfer conducted a study in 2012 that showed that stem cells in mouse ovaries continue to divide throughout their reproductive life, and that these stem cells may form eggs.