Non-Traditional Sources of Pluripotent Stem Cells: A New Chapter in the Debate?
John F. Brehany, Ph.D., S.T.L.
Fall 2005
For several years, ethical and political debate has been swirling over whether, and how, to utilize stem cells for research, drug testing, and regenerative medicine. Many scientists advocate use of embryonic stem cells (ESC) because of their near-universal, “pluripotent” flexibility. However, the fact that their derivation requires the destruction of human embryos, or close collaboration with abortion in the case of stem cells derived from the gonadal ridge of young embryos, has rendered them ethically suspect and excluded from federal funding under the Dickey Amendment and the Bush administration policy of 2001. Adult stem cells (ASC), on the other hand, have been derived from an increasing list of bodily tissue, utilized in an increasing list of cures, and have demonstrated unprecedented flexibility in changing into alternative types of cells.[1] However, because ASC are considered at best “multipotent,” rather than pluripotent, many scientists continue to demand access to ESC.
Recent efforts to resolve the impasse have generated proposals that stretch the boundaries of technology and ethics. These proposals seek to retain access to pluripotent ESC while avoiding the ethical and political consequences of destroying human embryos. The concepts for several “nontraditional” approaches to deriving ESC were presented to the President’s Council on Bioethics (PCB) in December 2004.[2] While ethically and technologically challenging, the proposals and the PBC’s analyses significantly expand the public debate and provide new opportunities to introduce ethical considerations into public discourse.
Proposals for Nontraditional Sources of Pluripotent Stem Cells
The first two proposals involve the retrieval of individual blastomeres (totipotent cells) from human embryos, culturing these to develop into blastocysts (embryos at 4-5 days gestation) and then extracting human ESC from the inner cell mass. Landry and Zucker propose obtaining blastomeres from “organismically dead embryos,” drawing an analogy with the widely accepted practice of organ donation. Their proposal includes establishing clear and reliable markers of embryonic death and utilizing only embryos that are thawed with a view to implantation (but then fail to demonstrate organized cellular activity). The second proposal endorses extraction of one or more pluripotent blastomeres from living human embryos, then culturing these to the blastocyst stage and deriving ESC, arguing that blastomere extraction (an increasingly common practice in artificial reproductive technologies in conjunction with preimplantation genetic diagnosis) can be performed without [apparent] damage to the embryos that are allowed to survive. The ESC could then be used either for the benefit of a third party or for the future benefit of the original, developing embryo.
The third proposal is the most complex, ethically and technologically. This approach, called altered nuclear transfer (ANT), seeks to bypass destroying human embryos by creating a “nonhuman” cellular organism that could develop long enough to produce ESC. William Hurlbut of Stanford University argues that, providing an organism lacks the essential biological structures necessary for normal human development (even if it is capable of developing enough to produce stem cells) and providing that the genetic engineering that removes these essential biological structures is performed prior to conception, one can argue that no human embryo has been created, or destroyed.
The fourth and final proposal involves somatic cell de-differentiation – the return of the body’s specialized cells directly to a pluripotent state, without creating a human embryo. Whether somatic cell de-differentiation is possible in the foreseeable future remains to be seen. However, since December 2004 a more specific proposal, called ooctye assisted reprogramming (OAR) has been advanced and has garnered widespread support from opponents of traditional forms of ESC derivation.[3]
Ethical Analysis
The PBC recognized the wide array of ethical issues raised by these proposals. Still, there is a consensus in the PBC’s analyses that respect for life of human embryos is a central ethical and public policy consideration. The PBC acknowledges that both proposals involving blastomere extraction are flawed because they require the eventual destruction of a human blastocyst (despite the distance the Landry/Zucker proposal tries to establish between the source of ESC and the destruction of embryos). Based on the same principle, the fourth proposal is the least problematic because it would involve transforming “mere” parts of the human body into other parts, and not the creation and destruction of a distinct human organism. Hurlbut’s proposal drew the most sustained ethical analysis and critique,[4] in part because not all agreed that the proposed “artificial organism” would not be human, in part because of the discomfort created by intentionally introducing critically disabling flaws into the human genome, and in part because of the likely rejection by scientists of ESC from such a unusual source.
These new proposals, and the debate they have engendered, are welcome because they shift the focus away from the “all or nothing” terms in which many construe the debate, and they provide an opportunity to broaden the debate by introducing considerations that can enrich ethical discourse both in the Church and in the public square. One such ethical consideration is based on Foucault’s recognition of the importance of “practices” (small, habitual, pervasive actions) in shaping our view of reality and our values. If any of the above proposals or a similar one becomes widespread, it likely will give rise to an industry in which the most fundamental structures of human nature and embodiment are measured and controlled. To prevent the objectification or commodification of human nature, it will be necessary to avoid, or challenge, the effect of such practices.
On a related note, Schindler draws attention to the profoundly different view of nature underlying much of modern science and technology.[5] He argues that, particularly in the age of biotechnology, to adequately defend human dignity (and ensure that technology serves, rather than determines, human nature and the human good) it is not enough to propose technological solutions to ethical dilemmas. Rather, to help shape not only technological methods but also the ends of science, we must examine the underlying assumptions of all proposals and defend our own deepest beliefs about nature and human nature.
[1] See, e.g., “Benefits of Stem Cells to Human Patients: Adult Stem Cells v. Embryonic Stem Cells,” available at http://www.stemcellresearch.org/facts/treatments.htm
[2] President’s Council on Bioethics, Alternative Sources of Pluripotent Stem Cells: A White Paper (May 2005), available at http://www.bioethics.gov.
[3] “Production of Pluripotent Stem Cells by Oocyte Assisted Reprogramming: A Joint Statement,” available at http://www.cbhd.org/resources/stemcells/jointstatment_2005-06-20.htm
[4] Douglas A. Melton, George Q. Daley, and Charles G. Jennings, “Altered Nuclear Transfer in Stem Cell Research: A Flawed Proposal,” N. Engl. J. Med. 351(27) (Dec. 30, 2004): 2701-02.
[5] David L. Schindler, “Biotechnology and the Givenness of the Good: Posing the Moral Question Regarding Human Dignity,” 31 Communio (Winter 2004): 612-45.
