Infertile women have been offered new hope after scientists found that a common cancer drug triggers the development of new eggs, an outcome which was previously thought to be impossible.
In a discovery hailed as "astonishing", researchers at the University of Edinburgh proved it is possible to reverse the clock and coax the ovaries back into a pre-pubescent state where they begin to produce new eggs.
Women are born with all their eggs, which is why conceiving becomes harder with age, because the eggs grow old, become damaged and eventually run out entirely.
But scientists noticed that women who had undergone chemotherapy for Hodgkin’s Lymphoma with a drug combination known as ABVD had up to 10 times the number of eggs as healthy women.
Far from damaging the chance of having a baby, the cancer drugs may actually have improved their fertility.
The researchers speculate that the shock of chemotherapy may trigger stem cells in the ovaries into producing new follicles, the hollow hair-like structures which each produce a single egg.
Lead researcher Professor Evelyn Telfer, of the University of Edinburgh's School of Biological Sciences, said: "We were astonished when we saw what had happened to the tissue. It looked like pre-pubescent tissue with a high density of follicles and clustering that you don’t normally see in an adult.
“We knew that ABVD does not have a sterilising effect like some cancer drugs can, but to find new eggs being made, in such huge numbers, that was very surprising to see.
“It looks like something is being activated probably in the germline or stem cells and we need to find out what that mechanism is. It could be that the harshness of the treatment triggers some kind of shock effect or perturbation which stimulates the stem cells into producing new eggs.
“I think it’s a pretty big deal. It is the first time that we have ever been able to see new follicles being formed within the ovary, and it may only be a small number of women, but it is significant that the same effect was seen in all of the women on ABVD. The outcome may be significant and far-reaching.”
Scientists analysed samples of ovarian tissue donated by 14 women who had undergone chemotherapy, alongside tissues from 12 healthy women.
They found that the tissue from eight of the cancer patients who had been treated with ABVD had between four and 10 times more eggs compared with tissue from women who had received a different chemotherapy, or healthy women of a similar age.
The ovarian tissue was seen to be in healthy condition, appearing similar to tissue from young women's ovaries.
Although the eggs are still in an immature state, the scientists are now trying to discover how they were created in the first place, then work out a way to bring them to maturity. It is unclear if the eggs in their current form would be functional.
But if research can reveal the mechanism, it would help scientists understand how women could produce more eggs during their lifetime, which was until now thought to be impossible.
Future studies will examine the separate impact of each of the four drugs that combine to make ABVD - known as adriamycin, bleomycin, vinblastine and dacarbazine - to better understand the biological mechanisms involved.
Professor Charles Kingsland, a fertility expert of Liverpool Women’s Hospital, said: “This is a very small but extremely interesting study. It's very early days but may give an insight as to how the ovary can make new eggs, which previously we thought was impossible.
“It's particularly fascinating that a commonly used chemotherapeutic agent to treat cancer in young girls has been shown to cause this effect.”
The study was published in the journal Human Reproduction, and supported by the Medical Research Council.