With an assist, an old mouse might be able to make new eggs.
Sterilized female mice produced healthy babies after receiving a transplant of egg-generating stem cells from another mouse, researchers report online May 18 in Molecular Therapy. If such a procedure worked in humans — still a distant prospect — it could help women with early menopause or chemotherapy-induced infertility to conceive.
These egg-generating cells are germline stem cells — precursors that become either eggs or sperm depending on whether they end up in ovaries or testes. While male germline stem cells differentiate (or become specialized) throughout a man’s life to produce a steady supply of new sperm, a woman’s are believed to differentiate into a stockpile of eggs during a relatively narrow time frame before she’s even born. Some recent studies have begun to question that conventional wisdom, though the idea that germline stem cells could still exist in women after birth is controversial.
“It’s been a debate for many years, whether there were indeed cells in the adult ovary capable of forming new eggs,” says Evelyn Telfer, a reproductive biologist at the University of Edinburgh who wasn’t part of the new study.
If such a population of cells existed, women might be able to produce new eggs later in life. That could offer hope to women whose existing eggs were damaged in some way. Isolating those germline stem cells and coaxing them to become eggs has proven tricky, though. The cells need just the right environmental conditions to turn into eggs.
Scientists have previously shown that isolated germline stem cells from mice can turn into eggs in a petri dish. “The argument is whether these cells will do it in the body normally, or is this a feature of the cells being cultured,” Telfer says.