Stem Cell Research and a Ban on Human Cloning
Some biotechnology companies claim that a ban on producing human embryos through cloning would stall important research in generating “stem cells” to cure a variety of diseases Cong. Record, 2/5/98, S425. To put this claim in perspective:
1. Cloning is desired as a source of “customized stem cell lines” which would be an exact genetic match to each individual patient with a given disease. But this would require each individual patient to undergo somatic cell nuclear transfer to produce one or many living human embryos who genetically are the patient’s identical twin sisters or brothers.Order now
These embryos would then be destroyed to provide embryonic stem cells.
Two methods of obtaining the cells have been described. In one, the embryo is allowed to develop normally for a week or two to the blastocyst stage, at or after the usual time of implantation in the mother’s womb; then this embryo, consisting of hundreds of cells, is dissected for its stem cells. The other method is to introduce molecular signals into the embryo’s environment to “trick” its cells into departing from normal development and instead producing “a mass of undifferentiated tissue,” which can then be reprogrammed into various kinds of cells Lee Silver, Remaking Eden: Cloning and Beyond in a Brave New World (Avon Books 1997), p. 128. In either case, the living embryo is destroyed.
2. This avenue for providing medical benefits has been described even by supporters as “largely conjectural” (J. Kassirer and N. Rosenthal, in New England Journal of Medicine, March 26, 1998, p. 905). President Clinton’s National Bioethics Advisory Commission called it “a rather expensive and far-fetched scenario.
” The Commission observed: “Because of ethical and moral concerns raised by the use of embryos for research purposes it would be far more desirable to explore the direct use of human cells of adult origin to produce specialized cells or tissues for transplantation into patients.”
The Commission outlined three alternative avenues for promising research using stem cells that do not involve human cloning, two of which do not use human embryos at all (Cloning Human Beings: Report and Recommendations of the National Bioethics Advisory Commission, June 1997, pp. 30-31).
The Commission’s Alternatives
The alternatives outlined by President Clinton’s Commission are as follows:
1. Generating “a few, widely used and well characterized human embryonic stem cell lines, genetically altered to prevent graft rejection in all possible recipients.” This would raise its own ethical objections because it may involve producing and destroying some human embryos at the outset; but it does not require somatic cell nuclear transfer, or the creating and destroying of genetically related embryos for each individual patient.
2. Stimulating “proliferation and differentiation of the quiescent stem cells which are known to exist in many adult tissues, including even the nervous system.” Such stem cells could be “customized” to each individual patient and would not be from embryonic sources.
3. Identifying “methods by which somatic cells could be ‘de-differentiated’ and then ‘re-differentiated’ along a particular path.” This would permit “the growth of specialized cells compatible with a specific individual person for transplantation.
” While at present this option is considered speculative, its feasibility is now enhanced by the central finding of the research that produced “Dolly” the sheep: An adult body cell can be “de-differentiated” surprisingly easily and regressed all the way back to a stage at which it can provide the nucleus for a new developing embryo. The question is: Can this regression be done to a point short of this, so an adult cell becomes the basis for cells that are like embryonic stem cells but never came from an embryo?
Other Alternatives (not explicitly cited by the Commission)
4. There are other promising sources of pluripotent (not embryonic) stem cells for treatment of disease. One example is hematopoietic (blood cell producing) stem cells from bone marrow or even from the umbilical cord blood in live births. These cells are already widely used in cancer treatment and in research on treating leukemia and other blood diseases. Their versatility was recently found to be even greater than once thought.
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