Embryonic stem cells taken from mice can be transformed into mouse eggs, according to a report published in the journal Science last week. If it works for mouse cells, many researchers believe that it will work for human cells, too.
In other words, colonies of human embryonic stem cells could potentially be transformed into an unlimited supply of human eggs. Those eggs, in turn, contain the factors needed to jumpstart the process that produces more malleable embryonic stem cells that can be transformed into any type of cell in the body. Thus, we now have the promise of a self-sustaining cycle of stem cell production that does not depend on donor eggs from living women.
This could have important effects on the future of what is being called regenerative medicine. Some day, physicians will be able to transform stem cells into cells and tissue that can replace damaged cells in the patient from whom the original genes were taken. Such cells would be perfect transplants that could repair things such as heart muscle damaged by heart attacks or replace dead brain cells killed by Parkinson's disease. Tens of millions of Americans could benefit from those techniques.
The major technical bottleneck has been the scarcity of human eggs needed to jumpstart the process. Heretofore, human eggs have been harvested from women who undergo hormonal treatments that cause them to superovulate. These treatments are generally unpleasant and may be dangerous to the women's health. Obtaining millions of eggs for stem cell therapies in this way would be neither moral nor practical.
Nevertheless, opponents of human stem cell research painted lurid pictures of women confined to human egg farms forced to produce eggs for avaricious doctors and corporations. Conservative embryonic stem cell opponent Wesley Smith calculated, "Obtaining [800 million] human eggs for [curing diabetes] would involve stimulating the ovaries to hyper-ovulate, which generally produces 7-10 eggs. Assuming a liberal 10 eggs harvested from each procedure, 80 million women of childbearing age would be needed as donors." Feminist Judy Norsigian, the executive director of the Boston Women's Health Book Collective, joined with conservative opponents, citing fears that stem cell therapies would lead to a "massive expansion in the use of women as paid 'egg producers.'" But thanks to the new mouse stem cell work, it appears that donated eggs soon may not be necessary.
Assuming that human eggs can be produced in mass quantities using embryonic stem cells, that might split the strange bedfellows in the Left-Right coalition against therapeutic cloning. It may also make inroads among those people uncomfortable with therapeutic cloning, because that technique would make it clear that somatic cells (normal body cells) and embryonic cells differ only in the details of their biochemistry and can be transformed from one to another. An embryonic cell is no more a complete human being requiring legal protection than any other body cell.
For those still committed to the idea that every embryo is as morally significant as a living person, the discovery of how to transform embryonic stem cells into eggs will probably have little immediate effect. However, as the details of the biochemistry of embryonic cells, eggs, and somatic cells are further unraveled, the moral intuitions of such opponents may also shift. Even the Roman Catholic Church has changed its opinion about the moral status of early embryos over time and could change it again in light of new scientific information.
The discovery that embryonic stem cells can be transformed into eggs also has implications for human reproduction. For example, it could make human reproductive cloning unnecessary. How? Proponents of reproductive cloning have always believed that it would be a little-used niche treatment for infertility. Now researchers agree that it should be possible to transform embryonic stem cells not only into eggs, but into sperm as well.
One possible future scenario would have an infertile couple using eggs derived from previously existing stem cell lines to produce their own embryonic stem cells. These new stem cells with the genetic material derived from the man and the woman could be transformed into eggs and sperm that could then be combined to form an embryo. The new embryo containing genes from both the man and woman, just like a conventionally produced embryo, could then be implanted in the woman's womb. Gay couples could also use the same technique to produce children sharing both their genes. Of course, this should only be done once the technique has been proven to work safely.
Finally, the discovery of how to transform stem cells into eggs might derail the pernicious anti-cloning bill that has already been passed twice by the House of Representatives and is still pending in the Senate. The pace of biomedical progress may well outstrip the efforts of those who are trying to stifle it.