Researchers in China say they have managed to generate new eggs using stem cells from the ovaries of female mice. But the discovery is being met with skepticism.
It is has long been believed that female mammals are born with all the eggs, or oocytes, in their ovaries they will ever have. But in this study, published in the journal Nature Cell Biology, the scientists were able to use stem cells to encourage the ovaries to produce new eggs.
The researchers, led by Ji Wu from the School of Life Science and Biotechnology at Shanghai Jiao Tong University, said they isolated what they called female germline stem cells (FGSC) from the ovaries of five-day-old and adult mice.
Germline cells are the only cells in the body that grow into sperm or eggs. While they are abundant in male testes, their existence in ovaries has been controversial.
The cells were cultured for more than six months The researchers say they were able to generate new FGSC lines that proliferated even after being cultured multiple times.
Ten thousand of the cells were injected into both ovaries of infertile female mice. Eighty per cent of the mice went on to produce offspring after natural mating. All of the offspring appeared to be healthy.
"These results suggest that oocytes can be regenerated in sterile recipient females by transplantation of FGSCs," they wrote.
"The finding may have important implications in regenerative and reproductive medicine."
Other scientists, unrelated to the study, said the results sounded interesting but needed confirmation.
Robin Lovell-Badge, a researcher into stem cell at the MRC National Institute For Medical Research in Britain, called for caution.
"This paper will stimulate lots of activity in the scientific community, as happens when any dogma is challenged," he said.
"But what would be unfortunate is if this paper is hyped as a cure for female infertility. A lot more work is needed to understand what these new cells really are, and to verify the findings and the claims."
Dr. Darwin J. Prockop, director of the Texas A&M Health Science Center College of Medicine Institute for Regenerative Medicine at Scott & White said there was no reason to believe that infertile women could one day be given stem cell injections to repopulate their ovaries with fresh eggs.
"It's a cute experiment, but I don't think it's going to have anything to do with humans," he said. "There are too many steps, too many things could go wrong."
