Study: Mouse Stem Cells Form Embryos

May 2, 2003 ( Discovery Channel News) — A team of U.S. and French researchers has produced the first test tube gametes, or reproductive cells, from embryonic mouse stem cells, a development with far-reaching implications for cloning and fertility research. The research marked the first demonstration that embryonic stem cells are capable of producing all types of cells, including reproductive cells, in a laboratory environment, the scientists concluded in their findings, published on the journal Science website Thursday.

"Most scientists have thought it impossible to grow gametes from stem cells outside the body," said lead researcher Dr. Hans Schoeler of the University of Pennsylvania's veterinary school. "We found that not only can mouse embryonic stem cells produce oocytes, but that these oocytes can then enter meiosis, recruit adjacent cells to form structures similar to the follicles that surround and nurture natural mouse eggs, and develop into embryos," Schoeler said. "These germ cells then accumulated a coating of cells similar to the follicles surrounding mammalian eggs."

Until now, stem cells cultivated in vitro were considered to be pluripotent: in other words, able to produce all types of cells except for ovocytes and sperm. But the researchers found that the cells seemed to undergo meiosis — a cell division process inherent in sperm and egg development — and eventually developed into first-stage embryos, although the eggs were not fertilized.

Researchers now want to determine whether ovocytes produced in vitro can be fertilized. "This is the first demonstration that embryonic stem cells are totipotent -- capable of developing in every cell type -- outside of the body, according to the study authors. The U.S.-French team said the findings could have important implications.