A year back, scientists in Japan produced healthy mice from lab-created sperm; now, they've done the same with lab-made eggs. The project has big implications for humans, potentially paving the way for infertile men and women to have their own offspring. "This is quite a startling feat," says a stem cell expert. "But like so much of biomedical technology, it has a double edge to it." For instance, the breakthrough could theoretically allow people of any age, even dead people if their tissue was saved, to have children, the Wall Street Journal notes.
The scientists were able to achieve healthy mouse pups starting with two different kinds of cells: embryonic stem cells and mature adult cells "reprogrammed" into stem cells. The process works through adding proteins called growth factors to the stem cells, then combining them with somatic cells, which account for a large portion of the growing body. After implanting them in a female mouse for four weeks, scientists removed them, fertilized them with natural sperm cells, and placed them in surrogate mothers. The process resulted in healthy babies 3.9% of the time using embryonic stem cells and 1.8% of the time using mature cells—compared to 13% using natural eggs. (Read more fertility stories.)