Producing eggs after menopause may now be possible thanks to a new study which shows that stem cells taken from human ovaries can produce “normal healthy eggs.”
“Our current views of ovarian aging are incomplete. There’s much more to the story than simply the trickling away of a fixed pool of eggs,” said lead researcher Jonathan Tilly of Harvard’s Massachusetts General Hospital, who has long hunted these cells in a series of controversial studies.
The scientific community has long held the contention that women are “born with a fixed amount of ova at birth, which gradually become depleted by menopause. However, Tilly began to wonder if that was really true after reporting that the ovaries of adult mice harbor some egg-producing stem cells back in 2004.As a result he began to wonder if the same existed in human females.
“A female is most endowed with oocytes (eggs) as a fetus, when she has about 7 million,” Tilly stated during a phone interview with Bloomberg News. “That number drops to 1 million by birth, and around 300,000 by puberty. By menopause the number is zero. Because of this, scientists for the past sixty years believed that the ovarian stems cells capable of producing eggs are only active during the fetal stage.”
In challenging that theory, Tilly and his team gathered healthy ovaries donated by patients undergoing sex change surgery and used them to identify ovarian stem cells because they “express a rare protein that’s only seen in reproductive cells.”
They then injected these cells into human ovarian tissue that had been grafted under the skin of mice (which provided the blood that enabled them to grow). Within two weeks, they found that early stage human follicles with oocytes had begun to develop.
Although further research is needed, many scientists now believe that the ability to “harness” these stem cells could eventually lead to more efficient treatments for infertile women.
Tilly and his team are now working with scientists at Japan’s Saitama Medical University, to develop a bank for ovarian stem cells which can be cryogenically frozen and thawed without damaging them (unlike human eggs). They also hope to identify hormones and other growth factors for accelerating the production of human oocytes from the stem cells as well as ways to improve in-vitro fertilization
The new research was funded largely by the National Institutes of Health. Tilly co-founded a company, OvaScience Inc., to try to develop the findings into fertility treatments. Details of Tilly’s study can now be found in the journal Nature Medicine.