Alternative Sources of Pluripotent Stem Cells
Warning: Catholic Online does in no way endorse this WHITE PAPER: Alternative Sources of Pluripotent Stem Cells. It is published here on Catholic Online for information purposes only.
The President's Council on Bioethics
Human embryonic stem cells hold great interest because of their pluripotency—their capacity to give rise to the various specialized cells of the body—and because of their longevity—their ability to be propagated for many generations in laboratory culture without losing their pluripotency. Until now, these cells have been obtainable only from living human embryos [at the 100-to-200-cell (blastocyst) stage of development] by a process that necessarily destroys the embryos and that therefore makes this research ethically controversial. Over the past several years, the ethical controversy has been the subject of federal (and state) legislation and public policy and of ongoing public debate.i
The President’s Council on Bioethics is committed to the goals of advancing biomedical science and upholding ethical norms. Notwithstanding our sometimes sharp individual ethical differences, we have recognized that all parties to the debates about embryo research have something vital to defend, and not only for themselves but for all of us.1 As members of a national public bioethics body, we are also mindful of the need to understand and respect the strongly held ethical views of our fellow citizens, even when we do not share them. For these reasons, we must be receptive to any creative scientific or technical suggestions that might enable scientists to proceed with their research in ways that would not raise ethical questions or violate the ethical principles of many Americans.
Accordingly, in an effort to find ethically uncontroversial ways to advance human embryonic stem cell research, the Council has recently been looking into specific proposals for obtaining pluripotent, genetically stable, and long-lived human stem cells by methods that would meet the moral standard of not destroying or endangering human embryos in the process. This White Paper introduces these proposals and begins an analysis of their strengths and weaknesses, ethical, scientific, and practical. Because the scientific and practical merits of these proposals are in large part empirical matters, not settled in advance by mere speculation, we give special weight to the ethical analysis. We also explore, in a preliminary way, whether these alternative avenues of deriving and using pluripotent stem cells are likely to be embraced by scientists or to become eligible for federal funding.
Conceptually, four broad approaches present themselves. The stem cells could be derived: (1) by extracting cells from embryos already dead; or (2) by non-harmful biopsy of living embryos; or (3) by extracting cells from artificially created non-embryonic but embryo-like cellular systems (engineered to lack the essential elements of embryogenesis but still capable of some cell division and growth); or (4) by dedifferentiation of somatic cells back to pluripotency. In each of these four cases, the scientific standard by which success should be measured is only the desired functional capacity of the cells derived—stable pluripotency—and not their origin (embryos, adults, or artificial embryo-like clusters of cells). Should stem cells obtainable by one or another of these methods turn out to have exactly the same properties and capacities as embryonic stem cells (ESCs), their value for scientific research should be no different from that of standard ESCs.
Recently, more or less detailed examples of each of these four approaches have been proposed or discussed.
According to the first proposal, pluripotent human stem cells are to be derived from early IVF embryos (roughly 4-8 cells) that have spontaneously died (as evidenced by the irreversible cessation of cell division) but some of whose blastomeresii appear normal and healthy. Crucial to this approach is (a) enunciating a concept of organismic death of an early embryo and (b) devising criteria that permit a determination that embryonic death has occurred. In addition, to satisfy the moral standard, only those once-frozen embryos that are thawed and that die spontaneously during efforts to produce a child will be eligible for post-mortem cell extraction. This proposal was presented at the Council’s December 3, 2004, meeting by Drs. Donald Landry and Howard Zucker of the Columbia University College of Physicians and Surgeons.
According to the second proposal, pluripotent stem cells are to be derived from blastomeres obtained by biopsy of an early human embryo. Crucial to this approach is finding a stage of early embryonic development at ...
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