Excerpted from the Introduction to the WHITE PAPER: Alternative Sources of Pluripotent Stem Cells. The full report is available in hard copy from The President’s Council on Bioethics, 1801 Pennsylvania Avenue, N.W., Suite 700, Washington, DC 20006. The paper is also available online from www.bioethics.gov. The report examines each proposal to ascertain whether it is ethically sound, whether it is scientifically sound, and whether the proposal is “realistic” in terms of good public policy and research practice.

1) Pluripotent human stem cells could be derived from early IVF embryos (roughly 4-8 cells) that have spontaneously died (as evidenced by the irreversible cessation of dell division) but with some individual cells (blastomeres) that appear normal and healthy. Crucial to this approach is enunciating a concept of the death of a human embryo and devising criteria that permit a determination that embryonic death has occurred. Only those once-frozen embryos that are thawed and that die spontaneously during assisted reproduction efforts 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.

2) Pluripotent human stem cells could be derived from blastomeres obtained by biopsy of an early human embryo. This is a technique already practiced for pre-implant genetic testing of embryos for reproduction. Crucial to this approach is to find a stage of early embryonic development at which the removal of one or a few cells by biopsy can be carried out without harming the embryo, while the cells or cells removed from the embryo are still viable for research use.

3) There are a variety of proposals for engineering “biological artifacts” possessing some of the developmental capacities of natural embryogenesis (but lacking the organismal character of human embryos) and containing cells from which pluripotent stem cell lines can be derived. Crucial to this approach is demonstrating both that the developing entity is truly not a human embryo and that the cells derived from it are, in fact, normal human pluripotent cells. In addition, creating such “biological artifacts” must not itself introduce other ethical problems. One such proposal (“Altered Nuclear Transfer”) was presented at the Council’s December 3, 2004 meeting by Council Member Dr. William Hurlbut.

4) Human embryonic stem cells could potentially be derived by reprogramming human somatic cells, perhaps with the aid of special cytoplasmic factors obtained from oocytes (eggs) or alternatively possibly from pluripotent embryonic stem cells, so as to “dedifferentiate” the somatic cells back into pluripotent stem cells. Crucial to this approach is discovering a way to reverse cell differentiation all the way to pluripotency, but not even further to result in totipotency (as in cloning).