The announcement that human embryonic stem cells (hESCs) have been obtained from a single cell removed from an embryo apparently without damaging it raises the exciting possibility that one of the primary ethical issues of hESC research could be taken off the table. But both sides of the stem cell debate still have some work and waiting to do before the policy implications of this experiment can be fully understood.
As the authors of the paper in this week’s Nature magazine note, the effects of removing a cell from an embryo composed of eight to ten cells is not thoroughly understood. Is the embryo damaged by that process? And how often are embryos inadvertently destroyed in this single-cell biopsy process? Although the technique of removing a cell for the purpose of preimplantation genetic diagnosis (PGD) is routine, the effects on the embryos themselves, and any resulting fetuses and children, need to be tracked. If there is any risk of embryo destruction or damage, then single-cell biopsy would not have any moral advantage over obtaining hESCs from remaining embryos in fertility clinics.
A different problem is the fate of that biopsied embryo. Can we improve the technique so we won’t need to biopsy hundreds of embryos to derive a few stem cell lines? Will a woman be prepared to have it transferred to her uterus, even with assurances about its viability? Having permitted an embryo to be biopsied for research or therapy, how could we require a woman to have it transferred to her uterus? (As the authors of the Nature paper describe, at this time the biopsy method should be limited to the PGD context, in which a woman plans to have the remaining embryo transferred anyway.) If the embryo is simply returned to a fertility clinic freezer and never transferred into the uterus or eventually destroyed then, again, the ethical advantage of this method of obtaining hESCs will have been reduced.
There are still other ethical and scientific questions that need to be answered before the implications of single-cell biopsy for the stem cell debate can be understood. For example, it has been demonstrated that these single cells can in and of themselves give rise to a normal embryo in other animals. Even if the biopsied cells could not themselves become embryos, they could make a genetic contribution to an embryo if surrounded by other cells. How is that possibility to be weighed ethically? In the experiment described in Nature, several cells are taken from the same embryo. In practice it is likely that only one or two would be taken from the same eight to ten cell embryos. It is not known, however, whether all cells in the early embryo would develop in the same way, so they may not be equivalent for research or therapeutic purposes.
This alternative method of deriving stem-cell-like cells is still nascent. This experiment has not proven the procedure to be practical or safe, and will require additional time and research to address the range of moral and technical questions the new procedure poses. In the meantime, we cannot slow our pursuit of life-saving cures using conventional methods of embryonic stem cell derivation.
There is one clear and rather ironic lesson from this experience: under the law the reported experiment could not have been done using federal funds, even though it might obviate the ethical debate about embryonic stem cells. Further experiments to address ethical and technical questions regarding this procedure will also be ineligible for federal funding. Currently, the 1995 Dickey-Wicker Amendment to the National Institutes of Health budget bans federal funding for research that creates or destroys embryos, Now is the time to repeal this outdated law.
Jonathan D. Moreno, Ph.D., is Emily Davie and Joseph S. Kornfeld Professor of Biomedical Ethics and Director of the Center for Biomedical Ethics at the University of Virginia. He is a Senior Fellow at the Center for American Progress and Director of the Progressive Bioethics Initiative.
John D. Gearhart, Ph.D., is C. Michael Armstrong Professor of Medicine and Director of the Stem Cell Program at Johns Hopkins Medicine.
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Jonathan D. Moreno