Close up of a stem cell
Hundreds of thousands of infertile women could be given hope of becoming mothers after doctors discovered a way to create eggs using stem cells.
Researchers believe that they can produce new eggs in infertile women even if the ovaries are damaged or the woman has passed the usual age of conception.
The technique involves transplanting stem cells into the ovaries and could work on the one in 10 women who suffer from infertility as well as those who want children late in life.
Until recently it was assumed that a woman was born with a finite lifetime store of around two million egg-producing follicles and no more could be produced.
By puberty this number has already fallen to about 400,000, and at the menopause too few eggs remain to permit fertility.
But four years ago scientists in the USA showed it was possible to obtain stem cells from the ovaries of adult women that could be grown into mature egg cells.
Stem cells are “master cells” which can be manipulated in a laboratory to become any other cell in the body.
This work adds to the growing evidence that ovaries maintain an ability to manufacture new eggs long after birth.
Stem cell-derived eggs could in theory be used to delay the natural menopause, or provide new hope to female cancer patients made infertile by their treatment.
The new research was conducted by a team of Chinese scientists led by Dr Ji Wu, from Jiao Tong University in Shanghai, who isolated a small number of female germline stem cells (FGSCs) from the ovaries of adult mice.
The cells were grown in a laboratory for more than six months and given a green fluorescent jellyfish protein to act as a marker.
After they were transplanted into infertile mice, the stem cells developed into mature oocytes, or eggs, capable of being fertilised.
Eventually the mice gave birth to offspring carrying the fluorescent protein gene.
Dr Wu said he believed that the system would work in humans as we share the same “female germline stem cells”.
“These cells can be used to extend female reproductive lifespan,” he said. “The generation of new oocytes (eggs) could postpone normal or premature ovarian failure, or be used in the treatment of infertility.”
The scientists, who published their findings in the journal Nature Cell Biology, said the work was also crucial to anti-ageing and regenerative medicine.
Professor Robin Lovell-Badge, from the Medical Research Council National Institute for Medical Research, said: “The present paper describes a new set of data… suggesting that there is a small population of cells (referred to as FGSCs) persisting in the ovaries of mice from birth to adulthood that can be isolated, grown in culture, frozen and thawed if required, returned to ovaries of other mice that have been depleted of their own eggs, and then give rise to offspring after mating to normal male mice.
“If true, and especially if applicable also to humans, then this is very important. For example, it could provide a means to restore fertility to women who have few eggs or who have had to undergo cancer treatments, by isolating these cells, expanding their number in culture and keeping them frozen until needed for IVF, etc.”
Professor Azim Surani, from Cambridge University’s Gurdon Institute, said: “Sperm are produced continuously in men but the number of eggs in women is fixed at birth.
“This new study in mice now suggests that there are also stem cells present in ovaries that can be cultured in a dish, which upon transfer to ovaries can develop into viable eggs and give rise to offspring.
“This finding, if confirmed independently, could advance understanding of these ovarian stem cells and advance research on female infertility.”