Alternative sources of stem cells.

Embryonic stem cell research pits the promise of curing devastating diseases and saving lives against the destruction of human life at its earliest stages. To circumvent this moral dilemma, the President's Council on Bioethics recently published a white paper, Alternative Sources of Human Pluripotent Stem Cells, (1) that examines four ways human pluripotent cells might be derived without killing human embryos. The effort to find such alternatives demonstrates a welcome recognition of the potential benefit of ESC research--sometimes dismissed as mere "hype" by its opponents. The White Paper is no "white wash": the scientific and ethical obstacles to finding acceptable alternatives are clearly laid out, and the diversity of opinion among the Council members is honestly acknowledged. Given the deep moral or religious opposition to destroying human embryos, the attempt to find alternative sources of human pluripotent cells is clearly worthwhile. The question, however, remains: can this be done, and at what cost? Deriving stem cells from dead embryos. The first proposal is based on an analogy with organ donation: just as it is ethically acceptable to remove organs from no-longer-living developed human beings, it should be equally acceptable to remove stem cells from no-longer-living human embryos. Using the traditional definition of death as the irreversible loss of the integrated functioning of an organism as a whole, Donald Landry and Howard Zucker of the Columbia University College of Physicians and Surgeons suggested in a proposal to the council that the embryo is properly considered "organismically dead" when it has irreversibly lost the capacity for continued and integrated cellular division, growth, and differentiation. A central question raised by the proposal and taken up in the white paper is whether the concept of organismic death--the death of an organism as a whole--can meaningfully be applied to organisms at the very beginning of life, when they are composed of a few undifferentiated cells. Moreover, even if the concept can be applied, determining that an embryo has died is more difficult than it is for an adult. An embryo has no integrating organs: no brain to be "brain-dead," no heart to cease beating and circulating blood. The problem is compounded by the fact that, in order for stem cells to be derived, the arrested embryos must contain at least some viable cells that retain normal developmental potential and that can be induced to resume dividing. But if these cells can resume dividing under certain conditions, has the embryo in fact died? Janet Rowley, a member of the President's Council, raises a different objection. She notes that part of the proposal involves observing thawed IVF embryos to see which ones have undergone spontaneous cleavage arrest and are thus "organismically dead." However, not all the thawed embryos will be dead; about half will continue to grow and divide. What will happen to these healthy embryos? They will be allowed to die while "scientists struggle to recoup a few living cells from the dead embryos!" She finds "totally baffling" the notion that it is ethically sound to let healthy embryos die rather than use them to try to develop cell lines that could benefit sick and dying patients. Nonharmful biopsy. The second proposal is based on the idea that stem cell lines might be derived from single cells extracted from early embryos in ways that do not destroy the embryo, which could then be used for reproduction. The impetus for this proposal comes from preimplantation genetic diagnosis, in which one or two cells are removed from an embryo created through IVF. (The cells are then tested for genetic disease.) More than 1,000 babies have been born worldwide after PGD, with apparently no ill effects. However, in the absence of long-term safety studies, it is not possible to determine conclusively that embryo biopsy is safe for the future child. …