An article in the latest issue of Nature Medicine has everyone in the infertility community buzzing. Researchers say they have isolated rare stem cells in women's ovaries that have the capability of creating new eggs.
Women are born with a lifetime of eggs and do not produce additional eggs as they age. (Men, on the other hand, produce sperm continually at an average of 100 million a day.) An average woman's body matures and releases one egg during each monthly menstrual cycle from menarche (her first cycle) until menopause (when her menstrual cycles have stopped). A woman's fertility begins to decline relatively early in her lifespan; by age 25, fertility begins to decrease. By age 30, her ovarian reserve is down to 12%, meaning most of her eggs gone.
In this latest study led by Jonathan Tilly, director of the Vincent Center for Reproductive Biology at Massachusetts General Hospital, the researchers built upon previous research done in mice, in which they were able to isolate the egg stem cells, mature them in vitro and produce eggs. Tilly's earlier work found proteins on the stem cells that distinguished them from other types of cells. These same proteins were found in women, the cells were isolated and grown, and then added back to the ovarian tissue samples and then transplanted into a mouse, where immature eggs began to grow.