Although it has long been assumed that women are born with all the eggs they will ever have in a lifetime, recent research has hinted that that might not be the case. Now researchers report the strongest evidence yet that women may be able to replenish their supply of eggs after they are born — and perhaps after age or disease might have normally hindered their fertility. The findings could help trigger new treatments for infertility and rejigger current views about how eggs develop in the ovary and whether aging should affect women’s ability to reproduce. In the new study, a milestone in an eight-year research journey led by Jonathan Tilly, director of the Vincent Center for Reproductive Biology at Massachusetts General Hospital, scientists successfully isolated a population of egg stem cells from human ovarian tissue and showed that these cells could go on to produce what appear to be human eggs. MORE: Scientists Restore Fertility in Mice Using Lab-Generated Sperm Tilly had previously isolated a similar population of egg stem cells from mouse ovaries, but critics raised questions about whether the cells were truly stem cells — cells that were truly the precursors of eggs, or oocytes — or whether they were actually very early, immature eggs themselves. Two groups, including Tilly’s, have since verified the results, showing that the cells are stem cells that were capable of going on to form viable oocytes that could be fertilized to produce healthy mouse pups. That led Tilly to investigate whether a similar egg stem cell existed in humans. But obtaining healthy ovarian tissue was a problem, since most ovarian samples currently available for research are obtained from cancer patients hoping to spare their tissue from treatment. Coincidentally, Tilly learned that a former research fellow from his lab, now working at Saitama Medical University in Japan, had been perfecting a technique for removing and freezing intact ovaries from patients undergoing sex change operations because of a gender identity disorder. By the time Tilly approached his colleague about his egg stem cell … Continue reading Ovary Stem Cells Can Produce New Human Eggs, Scientists Say