Japanese researchers at Kyoto University have created sperm from embryonic stem cells, the famed cells capable of becoming any type of cell in the human body. The researchers first modified embryonic stem cells into sperm progenitor cells, i.e. cells that are specialized to make sperm. After injecting the progenitor cells into sterile male mice, the mice fathered a new generation of healthy mouse pups and the researchers knew they had succeeded. The experiment offers hope to infertile men but the procedure is not yet ready for humans.
What’s the Big Idea?
There remains a catch. Were this procedure one day available to infertile men, their genetic information would not be passed on to their children. “By the time a person is of reproductive age—let alone gets past the first several days of embryonic development—it’s too late to make embryonic stem cells with one’s matching D.N.A.” To transfer genetic information from sperm progenitor cells, they will have to be made from induced pluripotent stem cells, or iPS cells, which are taken from adult tissue and “rewound” to an earlier state of development.