Scientists in Japan have for the first time transformed mouse embryonic stem cells into sperm cells, The Wall Street Journal reports. Researchers have previously been able to turn stem cells into human egg cells, but developing sperm cells was considered much more difficult. Writing in the online edition of the Proceedings of the National Academy of Science, researchers from the Mitsubishi Kagaku Institute of Life Science report that they were able to use embryonic stem cells and cells producing a protein that stimulates sperm development to transform the stem cells into sperm cells. The researchers then implanted the cells into male mice to expose them to male hormones to complete their development--a process that may be able to be conducted outside the body in the laboratory. The sperm cells were shown to be active and successfully fertilized mouse eggs.
The research was conducted only on male stem cells, and it's not clear yet if the process will work with female stem cells, the scientists said. If research pans out that does allow the creation of human male sperm cells from female stem cells, it may be possible for lesbian couples to have children that are genetically theirs, with one partner donating an egg and the other donating stem cells that will be converted into sperm. Research is also continuing by scientists in Philadelphia and France on developing human egg cells from male stem cells, which could someday allow gay-male couples to conceive children that have the genes of both partners.