By 2027 to 2037 scientists will likely be able to create a baby from human skin cells that have been coaxed to grow into eggs and sperm and used to create embryos to implant in a womb.
The process, in vitro gametogenesis, or I.V.G., so far has been used only in mice. But stem cell biologists say it is only a matter of time before it could be used in human reproduction — opening up mind-boggling possibilities.
With I.V.G., two men could have a baby that was biologically related to both of them, by using skin cells from one to make an egg that would be fertilized by sperm from the other. Women with fertility problems could have eggs made from their skin cells, rather than go through the lengthy and expensive process of stimulating their ovaries to retrieve their eggs.
IVF (Invitro fertilization) produces 70,000, or almost 2 percent, of the babies born in the United States each year. Worldwide there been more than 6.5 million babies born worldwide through I.V.F. and related technologies.
I.V.G. requires layers of complicated bioengineering. Scientists must first take adult skin cells — other cells would work as well or better, but skin cells are the easiest to get — and reprogram them to become embryonic stem cells capable of growing into different kinds of cells.
Then, the same kind of signaling factors that occur in nature are used to guide those stem cells to become eggs or sperm.
Last year, researchers in Japan, led by Katsuhiko Hayashi, used I.V.G. to make viable eggs from the skin cells of adult female mice, and produced embryos that were implanted into female mice, who then gave birth to healthy babies.
The female germ line undergoes a unique sequence of differentiation processes that confers totipotency to the egg. The reconstitution of these events in vitro using pluripotent stem cells is a key achievement in reproductive biology and regenerative medicine. Here we report successful reconstitution in vitro of the entire process of oogenesis from mouse pluripotent stem cells. Fully potent mature oocytes were generated in culture from embryonic stem cells and from induced pluripotent stem cells derived from both embryonic fibroblasts and adult tail tip fibroblasts. Moreover, pluripotent stem cell lines were re-derived from the eggs that were generated in vitro, thereby reconstituting the full female germline cycle in a dish. This culture system will provide a platform for elucidating the molecular mechanisms underlying totipotency and the production of oocytes of other mammalian species in culture.
Scientists could make an egg out of skin cells from women who can’t produce viable eggs–or who have other fertility problems, or who don’t want to go through the difficult process of surgical removal of their eggs for IVF. Or men with fertility problems involving their sperm. Two women could make a child that was truly theirs, with eggs from one and sperm made from skin cells of the other. Or two men, vice-versa.
Mouse oocytes created from embryonic stem cells. Credit: Katsuhiko Hayashi, Kyushu Univ
In a couple of decades, Greely predicts, it will be possible to examine and select an embryo not just for a particular genetic disease but also for other traits, ranging from hair color to musical ability to potential temperament.
Greely concedes that Easy PGD will be mostly available in rich countries, but he also thinks it will be widely available in those countries because it will be free. Preventing the birth of people with genes that increase their risk of serious (and expensive) disease will save health care systems so much money that Easy PGD will be convincingly cost-effective.
That will be a powerful incentive to encourage prospective parents to further decouple procreation from sexual intercourse, and make it easy for them to drop off their skin cells at a lab. The lab will then generate a big supply of embryos containing the couple’s genes, embryos that can be examined for desirable characteristics as well as disease genes. The winner of this elimination contest will, presumably, be selected for implantation.