Human eggs could one day be produced in "unlimited" numbers thanks to research that could revolutionise fertility treatment.
Stem cells found in women's ovaries can be encouraged to create immature eggs known as oocytes in the laboratory, researchers said.
Judging by experiments carried out on mice grafted with human tissue, these eggs could then be readied for fertilisation – and though further tests on human cells could not be carried out due to ethical restructions, similar work with mice eggs indicated fertilisation was possible.
The study, published in Nature Medicine, claims to disprove the belief that women are born with all the eggs they will ever possess.
The results offer hope that women are "no longer faced with the idea that there's a fixed bank account of eggs at birth with only withdrawals and no deposits", Dr Jonathan Tilly, the paper's lead author and a reproductive biologist at Massachusetts General Hospital in Boston, told the Wall Street Journal.
"I think it opens up the chance that sometime in the future we might get to the point of having an unlimited source of human eggs," he said.