Stem Cells and Cloning
The controversy over stem cells has been complicated by its entanglement with the controversy over cloning. This confusion engendered by this entanglement calls for clarification. The two controversies come together on the issue of immune rejection. If we were to coax hES cells to become differentiated neural cells, and if we were to implant those cells into a patient, that patient’s immune system would likely put up a blockade and fight off an invasion of what, genetically speaking, are foreign cells. This problem of immune rejection, or ‘histocompatibility,’ represents a significant technical hurdle that scientists will need to clear if the promise of hES cell transplantation is to be realized. (Our experience with organ transplants demonstrates how serious a problem histocompatibility can be.) If, however, the stem cells could be made with the exact genetic code of the recipient, then the transplant-recipient’s body would welcome the new cells as its own. The technology of cloning appears to offer the possibility to achieve just such a genetic match. The process looks like this. The laboratory researcher would begin with a woman’s egg, an oocyte, and remove the DNA nucleus. Then using the technique of somatic cell nuclear transfer (SCNT) developed in the Dolly experiments, a DNA nucleus taken from a skin cell or some other somatic cell in the future recipient’s body would be rendered quiescent and then transferred to this enucleated oocyte. The egg would then possess a full complement of DNA, the very DNA of the future recipient. The egg would be activated, and at five days or so the stem cells would be harvested. They would be teased into becoming heart tissue or liver tissue or whatever is needed. They would be placed into the patient’s body. The stem cells would then regenerate whatever organ welcomes them home. This technique is called “therapeutic cloning” and promises perhaps the best way to overcome the problem of immune rejection. It is generally distinguished from “reproductive” cloning, which would be the use of somatic cell nuclear transfer to generate a child. The addition of therapeutic cloning to stem cell research, however, advances another set of ethical issues. Not only must the ethics of stem cells deal with the problem of destruction of a blastocyst, but it must also deal with the deliberate creation in the laboratory of a new “embryo” that is slated for destruction. Some people believe that the deliberate creation of an embryo with intent to destroy it is an even more serious ethical issue than the destruction of embryos that were already “slated for death” because they would not be implanted during the IVF process. We turn now to the three moral frameworks that have structured - and, in our view limited - the public debate over stem cells.
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