Researchers in Japan have just announced a major breakthrough at the intersection of stem cell research and reproductive medicine. Starting with mouse stem cells, they were able to direct the development of the cells until they became fully functional eggs or oocytes. When fertilized with mouse sperm, some of the oocytes began to function like in vitro fertilization embryos. And when these embryos were implanted in surrogate mother mice, some of them came to term and resulted in the live birth of healthy mouse pups.
The mice are shown here at 11 months old. This is the first time anyone has produced fully function mammalian oocytes from stem cells entirely in a dish. The research team used both mouse embryonic stem cells and induced pluripotent stem cells, which were derived from skin cells of donor mice. While the overall success rate was not high, the fact that living, healthy pups were born seems to demonstrate that the process works. The article and a companion news article, both to read online, appear in the October 17 issue of the journal, Nature. The research team was led by Katsuhiko Hayashi.
The reproductive systems of mice and humans are quite different. Even so, there is some optimism among researchers that what has been done in mice can someday be done using human stem cells. If so, then researchers would be able to generate human oocytes for research and for fertility treatments. It would also be possible to produce oocytes from a male donor, and this could create new reproductive options, for instance, for same sex couples. Recently, researchers in China reported that they were getting close to producing functional human, also by starting with stem cells.
As these techniques develop, it is not hard to imagine that they might be combined with gene editing. Just how these various new technologies might fit together in the next decade or two is hard to predict. But it is clear that the breakthrough involving mouse cells is another key step toward greater human control of the human procreative process. Obviously that raises a wide range of concerns, and the researchers themselves agree that the public must be involved in conversations about where these technologies are taking us. If linked to gene editing, then this technique expands the number of ways in which some form of human germline modification might be achieved. And if that happens, the result could be new ways to avoid the transmission of genetic diseases or perhaps other improvements to overall health for future generations.