Special Harvard Commentary: The Ethical Debate Over Embryonic Stem Cells
Last reviewed and revised on May 20, 2013
By Anthony L. Komaroff, M.D.
Embryonic stem cells can turn into virtually any type of specialized cell. But because embryonic stem cells come from human embryos, they are the subject of a huge ethical controversy.
The Moral Arguments
Embryonic stem cells come from very early embryos. Such embryos:
The ethical question is simple: Is the embryo from which embryonic stem cells are taken a human life? When does life begin? Since removing the stem cells destroys the embryo, if an early embryo is a human life, then a human life has been destroyed.
One issue on which virtually all scientists and the general public agree is that creating a human clone and then trying to let that embryo grow into a human baby is unethical. Such "reproductive cloning" has been performed successfully in animals, the most famous example being the sheep named Dolly.
In 2007, cells very much like embryonic stem cells were created in both mice and humans by reprogramming specialized cells, and without creating an embryo! Since the ethical questions around human embryonic stem cells involve destroying an embryo from which embryonic stem cells have been taken, successful reprogramming in humans would be unlikely to raise ethical concerns.
The Legal Realities
There are two legal realities in the United States that affect the argument over the morality of using embryonic stem cells. The first is that abortion has been legalized by the U.S. Supreme Court — under certain conditions.
The second legal reality is that since 2001, there have been a limited number of embryonic stem cells for researchers to use. Although that limitation was eased by President Barack Obama in 2009, there still are constraints that some scientists feel are unnecessarily holding back research.
Can Scientific Research Change the Ethical Argument?
There are three possibilities that could make the ethical conflict irrelevant.
- Reprogramming — This involves tricking specialized cells to turn into cells very much like embryonic stem cells. This eliminates the need to collect embryonic stem cells from embryos, and hence would eliminate the ethical concerns in humans. However, it remains uncertain if this technique will work and be safe, if applied in humans.
- Giving adult stem cells the same ability as embryonic stem cells to turn into virtually any tissue. — This means there would be no need for embryonic stem cells. Recently, some adult stem cells called "multipotent adult progenitor cells" have been discovered that may have greater potential than most adult stem cells. However, it is too early to know if this potential will be so great that it avoids the need for embryonic stem cells.
- Coaxing specialized cells to reproduce themselves — Recently, Harvard researchers found that, in mice, the insulin-producing cells of the pancreas can do just this. Those same researchers discovered in 2013 a natural body chemical that can make this happen. If other specialized cells could be similarly coaxed, and if this could occur in humans as well as in mice, it could also eliminate the need for stem cell therapies.
- Transforming one specialized cell into another type of specialized cell, without first creating a stem cell — Recently, Harvard researchers accomplished this feat in living mice. One kind of pancreas cell was transformed into a beta cell — the kind of cell in the pancreas that makes insulin. If this feat could be achieved in humans, it could have important implications for treating diabetes. If this feat could be achieved with other types of specialized cells in other organs — for example, transforming one type of heart cell into heart muscle cells, to replace cells killed during a heart attack — it could have implications for many other diseases, as well.
Anthony L. Komaroff, M.D., is professor of medicine and editor-in-chief of Harvard Health Publications at Harvard Medical School. Dr. Komaroff also is senior physician and was formerly director of the Division of General Medicine at Brigham and Women's Hospital. Dr. Komaroff has served on various advisory committees to the federal government, and is an elected Fellow of the American Association for the Advancement of Science.