Sperm and eggs created in dish produce mouse pups

October 5, 2012

These adult mice grew from oocytes, or immature eggs, derived in vitro from induced pluripotent stem cells (credit: Mitinori Saitou and Katsuhiko Hayashi)

After producing normal mouse pups last year using sperm derived from stem cells, a Kyoto University team of researchers has now accomplished the same feat using eggs created the same way, Science Now reports. The study may eventually lead to new ways of helping infertile couples conceive.

The stem cells in both cases are embryonic stem (ES) cells and induced pluripotent stem (iPS) cells. The former are taken from embryos and the latter are adult tissue cells that are reprogrammed to act like stem cells. In theory, both can produce all of the body’s cell types, yet most researchers have been unable to turn them into germ cells, precursors of sperm and eggs.

The Kyoto group, led by stem cell biologist Mitinori Saitou, found a process that works. As with the sperm, the group started with ES and iPS cells and cultured them in a cocktail of proteins to produce primordial germ cell-like cells. To get oocytes, or precursor egg cells, they then mixed the primordial cells with fetal ovarian cells, forming reconstituted ovaries that they then grafted onto natural ovaries in living mice.

Four weeks and 4 days later, the primordial germ cell-like cells had developed into oocytes. The team removed the ovaries, harvested the oocytes, fertilized them in vitro, and implanted the resulting embryos into surrogate mothers. About 3 weeks later, normal mouse pups were born, the researchers report online today in Science.

Further in the future, the technique could lead to a new tool for treating infertility. “This study has provided the critical proof of principle that oocytes can be generated from induced pluripotent stem cells,” Clark says. If applied to humans, it could lead to the ability to create oocytes from iPS cells taken from infertile women.