Stem Cells without Embryos This is the first column of a series where we will look at some of the hot new topics in bioethics, attempting to simplify the jargon, and sort through some of the latest developments. Recently, a letter was released on the Ethics and Public Policy website (http://www.eppc.org/publications/pubID.2374/pub_detail.asp) that dealt with making embryonic stem cells without destroying human embryos. Many prominent Catholic scholars signed the letter. The letter proposed a new technique called oocyte assisted reprogramming, or OAR for short. This technique has never been done in the laboratory, but if it were to prove feasible, it could offer a way out of the central ethical dilemma raised by embryonic stem cell research. The central objection to embryonic stem cell research is that it requires the destruction of embryonic humans who are about 5 days old, in order to procure their stem cells. OAR might provide scientists with a way to make embryonic stem cells directly, without creating or destroying human embryos. Because no embryos would be involved, the stem cells you would get out of the OAR procedure really shouldn’t be called embryonicat all, but rather pluripotent. They would be pluripotent because they would be very flexible, as flexible as the stem cells you get from embryos. So how do you use OAR to make pluripotent stem cells? OAR makes use of a woman’s egg to carry out a procedure that, on first glance, looks very similar to cloning. Suppose for a moment that a police officer suffering from diabetes were to donate a skin cell from his arm, and we took the nucleus of that skin cell (which contains his DNA) and placed it inside a woman’s egg, after we had taken out her egg’s own nucleus. In other words, a kind of “nucleus swap”. The expression that scientists use is “nuclear transfer”. This is what cloning is all about. Even though no sperm is involved, the egg-with-a-new-nucleus now divides and grows normally as a human embryo, a new human being. This embryo is special, however, because it would have the same genes, and be the identical twin brother of the police officer. It would be a very young clone of the officer, and if that embryo were implanted into a woman’s uterus, it could become a live-born cloned baby. But if that tiny little embryo at the beginning were denied the safe harbor of a woman’s uterus to grow in, and the embryo was instead destroyed to extract its stem cells, scientists could get immune-matched cells for the potential benefit of treating the police officer’s diabetes. The reason they would be immune-matched cells, tailored to the police officer, would be that they came from his own identical twin brother. It turns out that identical twins can exchange organs (like kidneys) between each other without rejecting those organs. So the stem cells from his embryonic twin brother, in theory, could be introduced into his body without being rejected. The moral problem here, of course, is that you create your own twin brother (or twin sister if you are a woman) precisely in order to kill them when they are very young for their desired stem cells.If OAR were successful, it would avoid this moral problem. Instead of creating your own identical twin brother (or sister) for the purposes of strip-mining their stem cells, OAR would propose to directly make pluripotent stem cells through the same series of steps as cloning. The big difference would happen at the very beginning of the process, when special genetic changes would be made in the DNA of the police officer’s skin cell. These changes involve turning on special master genes that direct a cell to be pluripotent, or highly flexible, like a stem cell, rather than totipotent, or completely flexible, like an embryo. So when the “nucleus swap” would occur, the new cell would now become a kind of stem cell, rather than an embryo. In other words, the woman’s egg would never be activated to form a human being. If the resulting cells made by OAR were put into a uterus, nothing would happen, no pregnancy would be possible, since they would be stem cells, not embryos. Only embryos are capable of implanting into the wall of the uterus in making a woman pregnant. Since OAR stem cells are not derived from embryos, and are not embryos themselves, it would be morally permissible to culture and grow them or manipulate them in the lab as needed, in an attempt to come up with new therapies for patients. So the advantage with the OAR stem cells would be the same as for cloning, namely, that the stem cells that resulted from OAR would be immune-matched to the police officer, and in theory should not be rejected by his body if they were transplanted into him. OAR still remains a conceptual proposal at this time, but studies should be funded to look at the procedure in animals, to assure that it is technically feasible, and to assure that it can be done without making embryos and without crossing any moral lines. Some people might argue that we should not promote any research that makes it even remotely appear that we support embryonic-type stem cell research, given that so many remarkable successes in treating human patients are already happening using morally acceptable umbilical cord and adult stem cells. It is true, of course, that embryonic stem cells have not yet cured even a single human, while adult stem cells have successfully treated thousands of patients suffering from more than 50 types of ailments. It is also true that there are no clinical trials in humans yet using embryonic-type stem cells, while there are more than 200 clinical trials already underway using various kinds of adult stem cells. All of this reminds us how adult stem cells are indeed likely to provide the most effective route to the largest numbers of cures in the future. All of this also reminds us how such research should be vigorously funded and encouraged. But it may turn out that umbilical cord and other adult-type stem cells may not be able to do the job for every disease, while embryonic-type stem cells might end up being able to work in a few cases. If this does happen, and we have been proactive in examining and encouraging morally acceptable alternatives to getting pluripotent stem cells without destroying embryos, we will all be better off if, and when, that day comes. Rev. Tadeusz Pacholczyk, Ph.D. earned his doctorate in neuroscience from Yale and did post-doctoral work at Harvard. He is a priest of the diocese of Fall River, MA, and serves as the Director of Education at The National Catholic Bioethics Center in Philadelphia. |
