Scientists in Tennessee have scraped stem cells from the surface of five women’s ovaries and coaxed the cells to become human eggs.
The work, which was published in Reproductive Biology and Endocrinology, could extend a woman’s fertility for a decade or more if future experiments show that the eggs are capable of becoming fertilized. The five women who volunteered for the study ranged in age from 39 to 52.
Women who want to postpone pregnancy until later in life could potentially freeze some of these cells, called ovarian surface epithelium cells, for later use. And women who thought it was too late for children could have a second chance to conceive their own genetically related child.
“It is potentially path-breaking if the results … are validated independently by other researchers,” said Dr. Eric Scott Sills, a partner at Georgia Reproductive Specialists in Atlanta, and editor in chief of the Journal of Experimental & Clinically Assisted Reproduction. “It has the potential to significantly reshape how we approach menopause and the treatment of infertility in women over age 35,” said Sills, who did not participate in the research.
Antonin Bukovsky, who led the study, is a professor at the University of Tennessee Graduate School Medicine and has been studying female infertility for 20 years. Ten years ago, Bukovsky and his colleagues reported that ovarian surface epithelium cells, or OSEs, grow into human eggs. Last year they published surprising research suggesting that women produce eggs throughout life. Until that paper was published, as well as a similar study performed in mice, the conventional wisdom was that women were born with a set number of eggs.
Their previous work led the researchers to believe they might be able to use OSEs to grow human eggs in a dish. Through small abdominal incisions, they used a laparoscope to scrape OSEs from the women’s ovaries, then grew the cells in a dish for up to six days. They bathed the cells in a medium containing estrogen, called phenol red, which helped coax the cells into becoming mature eggs.
Other efforts to preserve fertility have seen some success in recent years. In March 2004, Kutluk Oktay of Cornell University produced an egg using ovarian tissue that had been frozen for six years, then implanted and grown in the woman’s arm. Oktay went on to create an embryo using one of the eggs.
Using Oktay’s method, scientists could save ovarian tissue before it had been treated with radiation or chemotherapy, which often renders a woman infertile. Bukovsky’s method offers the possibility that even women who have already undergone cancer treatment might now be able to grow eggs from their OSEs. There’s a chance, however, that the cells might be too damaged by the therapy to produce eggs.
“I would think that if the chemo is doing a good job, then it probably will not allow the survival of cells that would be usable in the future,” Sills said. “But we don’t know that, and there could be something special about the pace of division of the OSE cells that somehow renders them immune to chemotherapy. We know they are rapidly dividing, so they might be more tolerant of radiation.”
Other women have chosen to freeze their eggs. More than 100 babies have been born using frozen eggs, but the method is still considered experimental, and researchers aren’t sure whether birth defects might be more common in babies resulting from frozen eggs.
Researchers say all of the work is in early stages, and it’s not yet clear whether the techniques will become widespread treatments for infertility.
The results might also come in handy for scientists who say they need human eggs to create cloned human embryos for research. They want to use therapeutic cloning, also called somatic cell nuclear transfer, to create human embryos that carry the genetic traits of specific ailments such as Lou Gehrig’s and Alzheimer’s diseases. Observing the development of stem-cell lines extracted from those embryos could teach researchers how to fight the disease. Scientists also believe cloning could be help create cell therapies that would be an exact genetic match for any given patient, reducing the risk of immune rejection.
The need for eggs worries some feminist groups that suspect underprivileged women will be targeted to provide eggs, putting their health at risk.
by Kristen Philipkoski