Biotechnology is getting into some pretty interesting territory these days. The latest breakthrough comes from Kyoto University where research scientists have, for the first time, created a mouse by using eggs produced by stem cells alone. The achievement once again shows the remarkable possibilities presented by regenerative technologies like stem cells — but also the unsettling potential for human births in which parents might not be required.
Back in 2011, the same scientists, a team led by Mitinori Saitou, produced healthy mouse pups by using sperm derived from mouse stem cells. But if that wasn't remarkable enough, they have now shown that it's also possible to produce viable eggs with stem cells, too.
To do so, they used mouse embryonic stem cells (ES) and induced pluripotent stem cells (iPS). These cells are undifferentiated — they are simply waiting for an indication as to what type of functional cell they should transform into. Prior to this breakthrough, however, scientists had a hard time creating germ cells (an embryonic cell with the potential of developing into a gamete). This has to do with the way that germ cells divide, namely through meiosis in which cells contain a single copy of each chromosome.
To overcome this problem, Saitou took the ES and iPS cells and cultured them into a mix of proteins to produce primordial germ cells, what they hoped would eventually turn into an oocyte. Following that, they mixed the proto-oocytes (what the researchers call primordial germ cell-like cells (PGCLCs)) with fetal ovarian cells, and scaffolded the structure by grafting them onto the natural ovaries within live mice.
A month later, the proto-oocytes had turned into proper oocytes, which were in turn fertilized in a petri dish. The embryos were then implanted into a surrogate mother. The resulting pups turned out to be healthy — and in fact, they grew up to be fertile themselves.
Making human eggs
Moving forward, Saitou's group is trying to make the primordial cells from human tissue. It's thought that creating human sperm and eggs from embryonic stem cells will help scientists to better understand the reproductive process.
It's also thought that the technique could help both men and women who experience fertility problems. This could offer a way for prospective parents to have biological children that are derived from their own stem cells. It could also allow women to have babies later in life, or for women who cannot get pregnant due to cancer treatments.
More conceptually, the breakthrough suggests that human babies might someday be born from tissue samples and cell lines alone — with no direct parent involved. There are clearly a host of ethical implications that need to be addressed before any of this can be allowed to happen.
Correction: An earlier version of this article indicated that the sperm used to fertilize the eggs were also derived from stem cells, which is not the case.
The entire study can be read in Science.