Scientists Create Sperm And Egg Cells From Stem Cells

Wednesday, October 10, 2012

These adult mice grew from oocytes, or immature eggs, derived in vitro from induced pluripotent stem cells.
Stem Cells
Researchers at Kyoto University have grown adult mice from oocytes, or immature eggs, derived in vitro from induced pluripotent stem cells. It is reported that this achievement will have long-lasting impact on the field of reproductive cell biology and genetics as well as stir moral and ethical issues, as it raises the possibility of creating parentless embryos.
A fter 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. 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.

Image Source: Development

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.

Saitou says that with a bit more progress in understanding the complex interactions at work, they may be able to coax the cells through the entire oocyte development process in a lab dish. If successful, "we may be able to skip the grafting," he says.

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," says Amander Clark, a stem cell biologist at University of California, Los Angeles.  If applied to humans, it could lead to the ability to create oocytes from iPS cells taken from infertile women.

Saitou cautions though that moving on to human research will require resolving thorny ethical issues and technical difficulties. The extreme, the new approach could lead to the production of human embryos from cell lines and tissue samples.

SOURCE  Science Now

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