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Finding Ethically Acceptable Solutions for Therapeutic Human Stem Cell Research

Posted on: Friday, 4 July 2008, 03:00 CDT

By Meyer, John R

Abstract Katrien Devolder offers a compromise solution for the derivation of human embryonic stem cells that is designed to appease those who consider the killing of human embryos immoral. She proposes to build on a gradualist view of embryonic development in which the embryo merits special respect as human but does not possess ultimate value. Respect for the embryo must be weighed against other values, such as the desires of potential parents and the medical needs of patients who could benefit from stem cell therapy. Devolder also contends that William Hurlbut's "altered nuclear transfer" (ANT) proposal will not satisfy those who hold that the beginning of human life occurs at conception. In my critique of Devolder's position, I discuss why ANT and "oocyte assisted reprogramming" (OAR) are ethically questionable, and then review the epistemological value of the hylomorphic view of the human embryo, as well as the ethical importance of potentiality and intentionality. Finally, I argue for an expanded research effort in the area of adult stem cell therapy, which obviates the ethical dilemma associated with the manipulation or destruction of human embryos.

Introduction

Katrien Devolder offers a compromise solution for the contemporary debate over whether it is ethically licit to derive pluripotent stem cells from human embryos. The most controversial issue for those who advocate the harvesting of human embryonic stem (hES) cells is to take into account the special moral worth the immature human being possesses in the eyes of many people. While only a few authors claim that the human being is a person from the moment of conception, several Christian ethicists defend the human identity of the embryo and its unique moral status. Devolder points out, however, that numerous individual scientists and governmental agencies have developed intermediate positions on this question in order to foster promising research with hES cells for therapeutic purposes. These individuals generally argue that this line of investigative activity offers the possibility of alleviating the debilitating effects of numerous diseases if it is vigorously fostered and adequately financed.1

While a variety of new techniques for deriving hES cells have been proposed recently, Devolder reminds us that these methods are not all acceptable to everyone on ethical grounds. In this article I expand on her assessment of "altered nuclear transfer" (ANT), extending that critique to "oocyte assisted reprogramming" (OAR), suggesting that, in the final analysis, these two methods could actually be morally equivalent. I then offer some critical observations of her own compromise solution, suggesting that it is faulty in several critical respects. As an alternative, I briefly discuss the possibility of pursuing additional research into the therapeutic use of adult stem cells, such as those that can be derived from bone marrow and cord blood, an approach that avoids the ethical problems associated with hES cell use.

In Search of Compromise

Katrien Devolder describes a proposal advanced by Howard Zucker and Don Landry in which hES cells are taken from surplus embryos produced by in vitro fertilization (IVF). She correctly concludes that this proposal is just "a redundant compromise" meant to appeal to those who already accept the morality of IVF. While one could make a distinction between the morality of IVF for reproductive purposes and for the procurement of stem cells, I point out elsewhere how IVF tends to de-personalize human conception, trivializes marital sexuality, and often entails the destruction of some embryos.2 Similar reservations apply to the establishment of colonies of hES cells derived from single-cell blastomeres obtained from two-day-old pre-implantation embryos.3 While the researchers who developed this technique report that it spares the embryo, in fact, embryos were destroyed in the study. Moreover, given the fact that the blastomere could be totipotent, even if an embryo were not destroyed, scientists could be disrupting the development of a new embryo.

An alternative to deriving hES cells from (the destruction of) blastocysts would be to harvest these cells from the entity created by "altered nuclear transfer" (ANT), a variation on somatic cell nuclear transfer cloning. Here a technician alters a particular gene in a donor (somatic) cell nucleus, and then combines it with an enucleated oocyte, thereby creating an ANT entity (or "ANTity") that does not mature to the embryonic developmental stage and yet produces pluripotent hES cells. According to Dr. William Hurlbut, the original architect and principal advocate of ANT, deriving hES cells from the inner cell mass of these "embryoid-like entities" is ethically acceptable because the ANTity is a "limited cellular system that is biologically and morally akin to a complex tissue culture."4 Markus Grompe subsequently proposed a modification of ANT, "oocyte assisted reprogramming" (or OAR), which produces hES cells directly, that is, without forming an intermediary ANTity. Here a gene (e.g., nanog) is overexpressed in the host oocyte, which reprograms the donor somatic cell genome to produce a pluripotent cell.5

What are ANTities and OARites?

Both ANT and OAR are premised on the idea that the identity and function of every cell of the human body depends on which genes in the nucleus are switched on or off. ANT preemptively alters the epigenetic state of a somatic cell by silencing a particular gene in the nucleus (e.g., Cdx2) prior to transferring its genetic material into a host "ooplast" (the organic sac of cytoplasm left after the enucleation of an oocyte). According to one proponent of this procedure, "the gene sequence is not what is responsible for determining cellular identity, since the DNA is identical in nearly every cell in the human body. Rather it is the programming of the gene sequence that distinguishes cell types."6 Critics contend that ANT amounts to creating a badly disabled human embryo, for the epigenetic state of a cell does not define the ontological identity of an organism.7-9 Actually, something similar could be said about OAR, since the nanog gene holds the "OARite" in an undifferentiated state of development.10 Devolder points out that if we were to disable an implanted embryo so that it could not develop beyond eight weeks of gestation, it would be hard to justify that procedure in the minds of most people. Concerning Hurlbut's argument that his proposal shifts the ethical debate from when an embryo should be considered a human being to what component parts and organized structure constitute a human being, Devolder contends that the meaning of some expressions he uses (e.g., "integrated organismal existence" and "a self-sustaining and harmonious whole") are far from clear.

In the opinion of several authors, ANT creates a defective embryo that is prevented from developing into a blastocyst, with the ANTity progressing through developmental stages that are identical to a normal embryo. The OAR method, in contrast, creates an entity that is defective from its inception, with the genetic material of the donor reprogrammed to overexpress the nanog gene in order to maintain pluripotency and prevent differentiation. While the OARite seems to share no developmental stages with a normal embryo, it does share the initial stages of development seen in cloned embryos, including the process of nuclear reprogramming that occurs after the adult nucleus is introduced into the oocyte. This has led a couple of authors to conclude that the only difference between the OARite and the ANTity is that the developmental path of the former is shorter than the latter.11 In the end, OAR could be morally equivalent to ANT, simply representing an innovative attempt to overcome the "time-delay" inherent in the ANT technique.

To Be or Not to Be: Is that an Embryo?

While Hurlbut claims that the ANTity has no inherent principle of unity, because it does not form a trophoblast and embed in the uterus, the failure to form a trophoblast does not necessarily mean the ANTity is not an organism.12 Furthermore, the failure of an embryoid body to become a true blastocyst is the consequence of an intentional act, not the result of a random genetic mutation or a cytological defect, and it is clearly immoral to intentionally cause a defect in a developing embryo. In addition, since the product of ANT has a complete human genome (i.e., with the material constituents accounting for functional unity), the "silencing" of the gene responsible for triggering differentiation of the trophectoderm leaves the suppressed gene intact. Even if this gene were deleted, seriously altered, or damaged in some way, that would not signal the emergence of a new kind of organism, much less the absence of a human organism.

Some authors contend that the ANTity is not a genuine human being at all, because its developmental trajectory resembles that of an ovarian teratoma or a hydatidiform mole, entities that arise when a blastocyst divides prior to implantation and recombines with placental tissue. However, ovarian teratomas (or ovarian dermoid cysts) are wholly maternal in origin, arising from the spontaneous (i.e., parthenogenic) activation of an oocyte, whereas an ANTity has both maternal and paternal genes. Similarly, the parthenote is not really an analogue of an ANTity either, since it has a full complement of chromosomes derived only from the female. Hydatidiform moles, which can be complete or partial, are composed exclusively of paiernauy-derived genes; further, partial moles have 69 rather than 46 chromosomes, being the result of two sperms jointly fertilizing one egg. In sum, the comparison of the ANTity to teratomas, parenotes and hydatidiform moles fails, and so the argument that the ANTity is not really human fails as well. Does silencing gene expression alter speciation?

Although nearly every cell of the human body carries the entire genome, not all genes are expressed in all tissues, or even at every point of development. Genes are normally turned on and off at different developmental stages, with the expression of one gene affecting the overall pattern of gene expression in the organism. The coordination of cell divisions takes place by a process of methylation in which some genes are "silenced" and others are "turned on" so that development can proceed to the next stage.13 Over against Hurlbut's claim that the ANTity has no inherent principle of unity because it does not carry out certain functions, the process used to produce an ANTity mimics the initial phase of a natural pregnancy, except that a technician artificially prevents pregnancy.

The Cdx2 gene has been advanced as a possible genetic control switch for ANT because it is not expressed until the 16- to 32-cell stage of embryonic development, and it plays a critical role in the formation of the trophectoderm (which gives rise to the placenta). If this gene is "silenced" (by inserting a gene encoding an RNA that inhibits Cdx2 expression), the resultant embryoid body will not embed in the uterine wall. Besides the fact we do not know whether human Cdx2-deficient pseudo-embryos die at the same stage as mouse pseudo-embryos, it is possible that the hES cells taken from ANTities could develop in unpredictable ways.14 Moreover, since the pseudo-embryo's Cdx2 gene can be reactivated,15 a true embryo was probably present all along. In reality, gene "silencing" is similar to the situation of persons with genetic predispositions for Huntington's disease, Alzheimer's disease, or breast cancer. And so, in the words of W. Malcolm Byrnes, "one could argue that ANT- derived embryos (which are perfectly normal in every respect during the initial stages of development, except that they have genes knocked out of their genomes) are indeed human embryos."16 In sum, it appears that both ANT and OAR create a genetically disabled embryo, which is intentionally prevented from developing in a normal manner by artificially silencing the gene responsible for trophoectoderm formation.

When Does Human Life Begin?

Irving Weismann insists that the key issue in the hES cell debate is when human life begins, and this cannot be determined by science alone, but calls for recourse to philosophical reflection.17 David Schindler alleges that the proponents of OAR fail to recognize that the beginning of life is shrouded in mystery, and their reduction of life's origins to empirically observable facts fails to take into account the ontological dependence of all life on something other than itself. "[D]etermination of the presence of life in its most subtle beginnings is precisely not obvious in the manner of a positivistic fact, but always involves philosophical mediation (even if only unconsciously)."18 This is especially true of human beings, who are the source of their thoughts and actions, yet cannot be the ultimate source of their own spiritual life.19

Ontological individuation, rational ensoulment, and human potentiality

Some authors allege that the dominant view in ethics supports the instrumental use of the pre-implantation embryo because this entity has a relatively low moral status.20 One reason cited in support of this interpretation is that monozygotic twinning is possible up to 14-15 days after fertilization. Since the zygote or early embryo could divide up to the point of gastrulation, with any embryonic cell capable of becoming an individual human being, Thomas Shannon and James Wolter allege that the early conceptus has not completed ontological individuation. "While the zygote is the beginning of genetically distinct life, it is neither an ontological individual nor necessarily the immediate precursor of one."21 Of critical importance to this argument are the loss of cellular totipotency in the zygote/embryo and the restriction of its developmental possibilities to that of a single human being. However, just because the zygote/ embryo could possibly divide into integral twins before implantation does not necessarily mean it is not an ontological individual.22 Shannon and Wolter assume that embryonic individuation comes from something added on to the pre-implantation embryo, which ensures a level of development and integral function that prevents the emergence of another individual. The fact that a zygote could divide before implantation does not preclude it from being an ontological individual, although once it matures beyond the age of twining any division would result in only body parts (and not new organisms).

The hylomorphic theory of ensoulment

Since all living creatures have an animating principle of life, the notion of a soul is not limited to human beings. Moreover, the philosophical concept of "form" (or soul) explains the very nature (or essence) of animate things, being the ultimate principle of the organization and continuation of any life form (not simply the genetic structure of a material body). According to Thomas Aquinas' hylomorphic description of the soul-body (form-matter) relation, all animated beings are composites of "matter" (hyle) and "form" (morphe). The form or soul is the animating principle of a living substance, for it actualizes and configures the matter (or body) to which it is united. The rational soul of a human being is unique vis- a-vis the vegetative and sensible souls of plants and non-rational animals in that its faculties are not reducible to matter. That is to say, by its very nature, the rational soul transcends matter and is not confined to the limits of a body.23 Rose Koch-Hersehnov believes that hylomorphism has exceptional explanatory power for modern embryology, and she suggests that a hylomorphic account of immediate animation could explain why the "forced twinning" of human embryos has been unsuccessful to date. If twinning were simply a matter of splitting the chromosomes of one organism into two sets of chromosomes, the simple action of dividing an embryo in a material manner would always result in two organisms. So, in her estimation, the totipotency of pre-implantation embryos is merely a hypothetical possibility: "although published studies by no means provides evidence for an ensouled embryo, a review of studies on artificially induced twinning affords more plausibility to ensoulment at fertilization than is offered in philosophical literature on our origins."24

There is another potential difficulty with the theory of immediate animation which Koch-Hersehnov does not discuss. It would seem that if a human soul were present in a pre-implantation embryo, there would be evident human functions under its control. Specifically, given that the human being cannot carry out rational operations without a brain, it appears that a rational soul is not present in the early embryo (since the brain is absent). Actually, such a Cartesian concept of the soul-body relation overlooks an important feature of the soul's function, namely, its animation of a human body. In Gilbert Ryle's critique of Cartesian mind-body dualism, the human being is not simply a ghost in a machine. According to Ryle, Descartes made a category mistake by considering the mind as a substance, for mental activities really belong to the category of relations, not substance.25 Those who allege that a rational soul could not be present in the embryo without a brain to sustain intellectual activity forget that the soul primarily acts as the animating principle of life, and only secondarily functions as the principle of rational and volitional operations, when requisite vital organs like the brain reach a mature functional state.26

Aquinas (1226-1274) held that during normal human development only a vegetative soul is present at first, followed by an animate soul, and then a rational soul. In contrast, Thomas Fienus (1567- 1631) and Paolo Zacchia (1584-1659) argued that a rational soul is present from the moment of conception, and that this single soul directs organ development in the embryo.27 While the embryo does not manifest rational functions, it has the potential to develop a nervous system, and this is ascribed to its form or essence. "This teleological function of the form not only distinguishes the hylomorphic soul from a Cartesian soul but can account for how we could have once been the 'undeveloped' body that is the zygote."28 Indeed, philosophical theories of human growth that deny that the pre-implantation embryo is a human being offer no credible explanation for regular development of the unicellular zygote and the multicellular embryo, nor do they address the potential of the embryo to act in personal ways.

The significance of embryonic potentiality and moral intention

The potential for the early embryo to develop into a mature human being with operations that should always and everywhere be recognized and protected is present from the first moment of its existence. After all, there is no substantial change in the embryo from conception to birth, or from conception to its first thought- the individual human being has the same essence or substance from conception to death. Devolder overlooks this aspect of the potentiality argument, simply accusing those who use it to defend the embryo's special moral status of failing to take into account the hopes of infertile (prospective) parents. "[I]t is not the embryo as such that will be the object of value, but the embryo that is intended to lead to the birth of the desired child."29 However, in a strict axiological sense, an existing embryo is not really comparable with a (possible) future embryo. Something that is merely possible does not presently exist and thus only has hypothetical value, whereas something that already exists possesses definite moral value hic et mine. To focus one's attention on future possibilities, assigning greater value to them over real existents, amounts to living in a world of dreams. While what I want or desire in life reveals a motive for action, it lacks the impersonality required to serve as a suitable moral reason for action.30 Devolder admits that the greater value some people assign to a prospective child over the intrinsic value of an embryo is merely a belief, not something based on or derived from empirical facts or philosophical considerations. In reality, she argues that value is based on personal preference. The obvious problem with a preference- utilitarian approach to ethical inquiry is that people may be mistaken about their preferences, and they can be wrong for reasons that are not limited to what they consider would be most satisfying to them. Morality requires us to do more than seek personal preferences or subjective satisfaction; it demands taking into account justice, which entails the awareness of the rights and needs of others, calling for a non-arbitrary standard which will ensure that the basic values of all human beings are respected. A morally upright intention is another critical feature of good moral action, for the specific desires we entertain and seek to satisfy are not necessarily good, based solely on whether an act serves as an effective means for attaining a particular goal. This is not to say that intention is unimportant. Barry Miller points out that "the mere cutting of Plato's throat by Socrates is, in itself, neither morally good nor morally bad: it would be good if Socrates were intending to remove a tumour, bad if he intended to kill Plato, and neither good nor bad if he performed the act while sleepwalking."31 While the desire to have a child is morally good in the abstract, recourse to IVF is morally wrong in the judgment of many, and for a variety of more or less compelling reasons, as I briefly outlined above.

James Peterson questions the relevance of potentiality for the personal identity of an embryo, yet he mixes apples and oranges when comparing the potential of gametes to give rise to an embryo with the potential of embryos to display personal properties as they mature over time. "How can we let patients who are unmistakably people die to protect embryos that, even if implanted, may or may not turn out to someday become persons? We should not kill people to benefit others, but we should also not let people die to protect human tissue such as sperm or ova, though such gametes have great potential."32 In actual fact, there are two kinds of potentiality dealt with in this statement, and neither one is a sustainable critique of the genuine potentiality of the embryo. First of all, comparing the moral value of adult human beings with the potentiality of embryos to act as persons is specious: one should either compare the moral status of the embryo with the moral status of an adult or compare the potentiality of the embryo with the potentiality of an adult. Second, comparing the potentiality of the embryo to act as an adult human being with the potentiality of a gamete to become an embryo is an egregious (biological) error, for the gamete is not an organism but a reproductive part of an organism.

Current embryological science indicates that the organism resulting from the union of a sperm and an egg is a genetically human individual from the moment of conception, and the development of this nascent human being involves a continuous process of maturation, moving from one developmental phase to the next, with only arbitrary points of demarcation separating one phase from another. Few authors would contest the fact that the human being is an ever changing work-in-progress, eventually coming to be and to act in more personal ways by virtue of his or her relationships and actions. When addressing the issue of the potential of human embryos to act as mature persons, bioethicists often fail to distinguish between perception and conceptual thought. Perception is the process of acquiring, selecting, and organizing sensory information, whereas conceptual thought involves the mind's intentional exemplification of, or formal identification with, things in the world by way of language, as well as the ability to judge that these things are as one takes them to be.33 This distinction is not only important to keep in mind when comparing the sentient and primarily perceptive life of non-human animals with the rational operations of human beings, but it is also critical for evaluating the moral status of the immature human being. For example, the argument that rational ensoulment cannot occur until the cerebrum is sufficiently developed to support conceptual thought defies common sense, because to deny that an infant is a human being is patently absurd. In addition, the embryo is largely responsible for its own regular and complex development, including the inherent capacity for rational thought.34 Furthermore, we do not find the rational soul in any specific body part or organ, because, as the animating principle of bodily matter, it organizes and is responsible for the integrated function of the entire organism.

Finding a Happy Medium

Devolder suggests that the best way to manage the dilemma surrounding the procurement of hES cells is two-fold: to recognize the fact that most people accord a gradual and variable moral status to the early embryo, and to accept the idea that a contested value should not restrict scientific freedom. Over against the first point, moral value cannot be ascribed to an organism based solely on an extrinsic principle, such as human convention or public opinion, or the extrinsic properties or qualities it possesses at a given point in time. Notice, when Jonathan Moreno's writes, "although embryos deserve respect, they are not morally equivalent to human beings," what he means is that certain properties must be present in a human being before we are compelled to respect it unconditionally.35 Rather than evaluate nascent human life in terms of its (personal) properties, which are largely hidden, it is preferable to accept that the human embryo is human. Development of the embryo does not alter its ontological status, even though its perceived moral value may change in the minds of some as the embryo takes on more obviously human qualities. In short, one's moral stance toward the embryo should not depend on when its personal properties appear, but rather should be based on its human identity.

Devolder admits that the human embryo merits special respect, yet she alleges that we can sacrifice embryos for purposes of "highest importance," without explaining why one's personal desires outweigh the embryo's intrinsic moral worth. In effect, she applies a utilitarian calculus to public policy decision-making, without providing a convincing ethical justification for assigning greater moral value to alleviating suffering than to the intrinsic value of embryonic human life. There is a strong tendency here to focus on hypothetical benefits to justify the use of any means to achieve a desired result. What is missing in such thinking is an objective moral standard that would enable us to judge which options are good to employ as means to achieve the desired end. Any possible actions can be measured against one another in an ethical sense only if they have some shared property that can be evaluated by a distinct moral norm.36

The second element at work in Devolder's position is the belief that there are several legitimate views of the moral status of the embryo, and tolerance dictates that we never consider any one moral evaluation as simply true. Since the true moral value of the human embryo is not agreed upon, "a justification primarily based on a contested value is insufficient to restrict scientific freedom to such an extent."37 However, if freedom is limited to and is measured by what is, we can only act freely if we know the truth about things.38 In the issue before us at present, the human embryo either is or is not a human being-these are the only two possibilities. Notwithstanding the opinion of Norman Ford, who, like Shannon and Wolter, holds that the "pre-embryo" (or "pro-embryo") is not an ontologically distinct human individual, the totipotentiality of cells in the early embryo is merely a hypothetical possibility (not an active potentiality). Indeed, if the totipotency of embryonic cells were active, all these cells would become individual persons all the time, not just when twinning takes place. For all intents and purposes, monozygotic twinning is a developmental accident, in which a new genetically identical individual arises by way of asexual reproduction (or self-cloning).39

Ironically, the avid interest in hES cells for regenerative stem cell therapy is driven in part by the great success of bone marrow transplants, in which hematopoietic stem cells collected from the peripheral blood of HLA-matched siblings are used to treat diseases like leukemia and lymphoma. It is not too surprising, then, to learn that there are embryonic-like stem cell populations in adult bone marrow, which could serve as a source of pluripotent stem cells for tissue regeneration.40 Of equal interest, stem cells with pluripotent flexibility taken from umbilical cord blood and the placenta are beneficial in animal models of spinal cord injury, stroke, and Parkinson's disease.41 In addition, a recent example of the value and efficacy of employing autologous stem cell grafts is the case of Ryan Schneider, who was diagnosed with cerebral palsy at 3 years of age. Fortunately, his parents had the foresight to save Ryan's infantile cord blood at birth, and so physicians were able infuse the child with his own hematopoietic stem cells, causing his condition to improve rather dramatically in a short period of time.42 Unlike hES cells derived from the early embryo, which are not immunologically compatible with potential patients in need of cell transplants, using endogenous stem cells for therapeutic purposes avoids the risk of immunorejection.43 Even adult human neural progenitor cells (AHNPs) from the brain are highly expandable in cell culture, and these differentiate normally when implanted into the lateral ventricles of the brains of nude mice.44 So, even though many scientists have argued that hES cells are more promising than adult stem cells for regenerative medicine, one commentator quips: "if neurons are the goal, then harvesting AHNPs from a patient's brain, rather than going the somatic nuclear transfer route, seems [to be] a win-win situation."45 It now appears that there are stem/progenitor cells in more accessible areas of the body as well, which could serve as an effective means for providing regenerative cell therapy without using hES cells. For example, epidermal neural crest stem cells (EPI-NCSC) taken from hair follicles have a high degree of innate plasticity, and these cells can be isolated at high levels of purity and expanded in vitro. Perhaps the patient's own EPI-NCSC could be used for cell replacement/repair therapy, even for such intractable conditions as spinal cord injuries, avoiding a graft-versus-host rejection of the implant.46 The most exciting new discovery in the field of adult stem cell research is the extraction of stem cells from amniotic fluid. These cells are not tumorigenic; they can be induced to differentiate into cell types representing all three embryonic germ layers; and they are truly pluripotent.47

In the final analysis, the primary benefit of studying human stem cells may be to serve as models of disease processes in individual patients, without having to destroy human embryos. For instance, a physician could take cells from a diseased patient and revert them to their embryonic form, in order to see how they mature and why their development goes awry. This would shed light on the basic cause of the disease as well as serve as a means of screening potential drug therapies.48 So, while scientists often boldly assert that embryonic stem cell research should be pursued because these cells are more flexible and offer greater possibilities for future therapies, adult stem cells are not only more stable and less prone to tumorigenesis than hES cells, but autologous grafting of endogenous progenitor cells avoids immunorejection. These two considerations favor the pursuit of adult stem cell biology over experimenting with and the destroying human embryos, if medical therapy is the true goal of human stem cell research.49

Conclusion

Katrein Devolder maintains that the human embryo only deserves a limited level of respect because of its lack of ultimate value. The moral status of the embryo ought to be considered in terms of external and internal factors, weighing the former more heavily than the latter. This claim is apparently based on changing public opinions concerning the true identity of the embryo, with its intrinsic value being subordinate to and dependent on the intentions of others. However, if we were to set up personal preference as a legitimate ethical theory, no impersonal criteria for moral reasoning would be valid.50 Having been strongly influenced by naturalistic ways of thinking, and having virtually eliminated the qualitative discrimination of values, we are left with nothing more than desire and the maximization of its fulfillment as a practical guide for action.51 No wonder it has been so difficult to reach a consensus on the ethical probity of hES cell research.

Endnotes

1. Katrien Devolder, "What's in a Name? Embryos, Entities, and ANTities in the Stem Cell Debate," Journal of Medical Ethics 32 (2006): 43-48.

2. See my "Cloning Human Embryos: Why Artificial Human Procreation is Immoral," The Linacre Quarterly 62 (1995): 22-29.

3. Irina Klimanskaya, Young Chung, Sandy Becker, Shi-Jiang Lu, Robert Lanza, "Human Embryonic Stem Cell Lines Derived from Single Elastomeres," Nature. Advance online publication - 23 August 2006. This article is available at http://www.nature.com/nature/journal/ vaop/.

4. William B. Hurlbut, "Altered Nuclear Transfer as a Morally Acceptable Means for the Procurement of Human Embryonic Stem Cells." Paper presented to the President's Council on Bioethics, December 3, 2004: 2.

5. Markus Grompe, Robert P. George, "Creative Science Will Resolve Stem-cell Issues," Wall Street Journal June 25, 2005: A 14.

6. E. Christian Brugger, "Moral Stem Cells," First Things 163 (2006): 15.

7. Roberto Colombo, "Altered Nuclear Transfer as an Alternative Way to Human Embryonic Stem Cells: Biological and Moral Notes," Communio 31 (2004): 645-648.

8. Adrian J. Walker, "Altered Nuclear Transfer: A Philosophical Critique," Communio 31 (2004): 649-684.

9. David L. Schindler, "Veritatis Splendor and the Foundations of Bioethics: Notes Towards an Assessment of Altered Nuclear Transfer and Embryonic (Pluripotent) Stem Cell Research," Communio 32 (2005): 195-201.

10. John Shea, "The Pre-embryo Question," Catholic Insight - January 18-21, 2005. Available at http://catholicinsight. com/ online/bioethics/preembryo.

11. See W. Malcolm Byrnes and Jose Granados, "ANT-OAR Fails on All Counts," Science and Theology News (July 13, 2006). Available at http://wwwstnews.org/News-2902.htm.

12. Maureen L. Condic and Samuel B. Condic, "Defining Organisms by Organization," National Catholic Bioethics Quarterly 5 (2005): 346; cf. William B. Hurlbut, "Altered Nuclear Transfer as a Morally Acceptable Means for the Procurement of Human Embryonic Stem Cells," Perspectives in Biology and Medicine 48 (2005) : 225.

13. W. Jerome Bracken, "Is the Early Embryo a Person?," The Linacre Quarterly 68 (2001): 54-55.

14. Douglas A. Melton, George Q. Daley, Charles G. Jennings, "Altered Nuclear Transfer in Stem-cell Research - A Flawed Proposal," New England Journal of Medicine 351 (2004): 2791-2792.

15. Alexander Meissner and Rudolf Jaenish, "Generation of Nuclear Transfer-derived Pluripotent ES Cells from Cloned Cdx2-deficient Blastocysts," Nature 439 (2006): 212-215.

16. W. Malcolm Byrnes, "Why Human 'Altered Nuclear Transfer' is Unethical," National Catholic Bioethics Quarterly 5 (2005): 275- 276.

17. Irving L. Weissman, "Politic Stem Cells," Nature 439 (2006): 145-148.

18. David L. Schindler, "A Response to the Joint Statement, 'Production of Pluripotent Stem Cells by Oocyte Assisted Reprogramming'," Communio 32 (2005): 375.

19. Claude Bruaire, L'etre et l'esprit (Paris: Presses universitaires de France, 1983), 131.

20. Guido de Wert and Christine Mummery, "Human Embryonic Stem Cells: Research, Ethics and Politics," Human Reproduction 18 (2003): 680.

21. Thomas A. Shannon and Allan B. Wolter, "Reflections on the Moral Status of the Pre-embryo," Theological Studies 51 (1990): 603- 626, citation at 612.

22. Allan Holland, "A Fortnight of My Life is Missing: A Discussion of the Status of the Human 'Pre-embryo'," Journal of Applied Philosophy 7 (1990): 25-37.

23. See Thomas Aquinas, Quaestio Disputata de Anima a. 2 corpus.

24. Rose Koch-Hershenov, "Totipotency, Twinning, and Ensoulment at Fertilization," Journal of Medicine and Philosophy 31 (2006): 139- 164 (150).

25. See Gilbert Ryle, "Descartes' Myth," in The Concept of Mind (New York: Barnes and Noble, 1949), pp. 11-24.

26. Stephen J. Heaney, "Aquinas and the Presence of the Human Rational Soul in the Early Embryo," The Thomist 56 (1992): 34-37. For more on the distinctions one should make when discussing the unique functions of the rational soul, see my "Embryonic Personhood, Human Nature, and Rational Ensoulment," The Heythrop Journal 47 (2006): 206-225.

27. Cf. David Albert Jones, The Soul of the Embryo: An Enquiry into the Status of the Human Embryo in the Christian Tradition (London/New York: Continuum, 2004), 162-164.

28. Rose Koch-Hershenov, "Totipotency, Twinning, and Ensoulment at Fertilization," Journal of Medicine and Philosophy 31 (2006): 153.

29. Katrien Devolder, "Human Embryonic Stem Cell Research: Why the Discarded-Created-Distinction Cannot be Based on the Potentiality Argument," Bioethics 19 (2005): 181.

30. Robert P. George, In Defense of Natural Law (Oxford: Oxford University Press, 1999), 257.

31. Barry Miller, A Most Unlikely God: A Philosophical Enquiry into the Nature of God (Notre Dame and London: University of Notre Dame Press, 1996), 137.

32. James C. Petersen, "Is the Human Embryo a Human Being?," in eds. Brent Waters and Ronald Cole-Turner, God and the Embryo: Religious Voices on Stem Cells and Cloning (Washington, DC: Georgetown University Press, 2004), 85.

33. See John Haldane, "A Return to Form in the Philosophy of Mind," Ratio 9 (1998) : 253-277; John McDowell, Mind and World (Cambridge, MA: Harvard University Press, 1994), 11-12.

34. John Haldane and Patrick Lee, "Aquinas on Ensoulment, Abortion and the Value of Life," Philosophy 78 (2003) : 269-271.

35. Jonathan D. Moreno and Sam Berger, "Taking Stem Cells Seriously," The American Journal of Bioethics 6 (2006): 6.

36. See my "The Brave New World of Embryonic Stem Cell Research: Utilitarian Consequentialism and Faulty Moral Reasoning," The Linacre Quarterly 72 (2005): 319-330.

37. Katrien Devolder, "What's in a Name? Embryos, Entities, and ANTities in the Stem Cell Debate," Journal of Medical Ethics 32 (2006): 46. 38. James V. Schall, "Aquinas and the Life of the Mind," New Blackfriars 87 (2006): 402-403.

39. See Norman Ford, When Did I Begin?: Conception of the Human Individual in History, Philosophy, and Science (Cambridge/New York: Cambridge University Press, 1988), 27-28, 32, 176-77; idem, The Prenatal Person: Ethics from Conception to Birth (Oxford: Blackwell Publishers, 2002), 67. For an apt criticism of Ford, see William E. May, Catholic Bioethics and the Gift of Human Life (Huntington, IN: Our Sunday Visitor Publishing, 2000), 166-170; Germain Grisez, "When Do People Begin?," in Proceedings of the American Catholic Philosophical Association 63 (1989): 22-47; Benedict Ashley and Albert Moraczewski, "Is the Biological Subject of Human Rights Present from Conception?," in eds. Peter Cataldo and Albert Moraczewski, The Fetal Tissue Issue (Braintree, MA: Pope John Paul XXIII Medical-Moral Research and Education Center, 1994), 33-60 (esp. 50-53).

40. M. Kucia, R. Reca, F. R. Campbell, E. Zuba-Surma, M. Majka, J. Ratajczak, M. Z. Ratajczak, "A Population of Very Small Embryonic- like (VSEL) CXCR4+SSEA-I+Oct-4+ Stem Cells Identified in Adult Bone Marrow," Leukemia 20 (2006): 857-869.

41. David A. Prentice, "Current Science of Regenerative Medicine with Stem Cells," Journal of Investigative Medicine 54 (2006): 33- 37.

42. Cord Blood Registry, "Ryan's Story," Available at http:// www.cordblood.com.

43. Cf. Stuart H. Orkin and Sean J. Morrison, "Stem-cell Competition," Nature 418 (2002): 25-27.

44. See Noah M. Wallon, Benjamin M. Sutter, Huan-Xi Chen, Lung- Ji Chang, Steven N. Roper, Bjorn Scheffler, Dennis A. Steindler, "Derivation and Large-scale Expansion of Multipotent Astroglial Neural Progenitors from Adult Human Brain," Development 133 (2006): 3671-3681.

45. Ricki Lewis, "Elastomere Blasphemy," The American Journal of Bioethics 6 (2006): W38.

46. See Yao Fei Hu, Zhi-Jian Zhang, Maya Sieber-Blum, "An Epidermal Neural Crest Stem Cell (EPI-NCSC) Molecular Signature," Stem Cells 24 (2006): 2692-2702; Maya Sieber-Blum, Lisa Schnell, Milos Grim, Yao Fei Hu, Regula Schneider, Martin E. Schwab, "Characterization of Epidermal Neural Crest Stem Cell (EPI-NCSC) Grafts in the Lesional Spinal Cord," Molecular and Cell Neuroscience 32 (2006): 67-81.

47. Paolo De Coppi, Georg Bartsch Jr., M. Minhaj Siddiqui, Tao Xu, Cesar C. Santos, Laura Perin, Gustavo Mostoslavsky, Angeline C. Serre, Evan Y. Snyder, James J. Yoo, Mark E. Furth, Shay Soker and Anthony Atala, "Isolation of Amniotic Stem Cell Lines with Potential for Therapy," Nature Biotechnology 25 (2007): 100-106.

48. Nicholas Wade, "Some Scientists See Shift in Stem Cell Hopes," New York Times - August 14, 2006. Available at http:// www.nytimes.com/2006/08/14.

49. See my "Human Embryonic Stem Cells and Respect for Life," Journal of Medical Ethics 26 (2000): 166-70.

50. Alasdair MacIntyre, After Virtue, 2nd ed. (Notre Dame, IN: Notre Dame University Press, 1984), 24.

51. Charles Taylor, Sources of the Self: The Making of the Modern Identity (Cambridge, MA: Harvard University Press, 1989), 79.

JOHN R. MEYER, MS, DDS, STD

John R. Meyer, MS, DDS, STD, is a priest of the Opus Dei Prelature and is currently the Vicar of the Prelature in California, residing in San Francisco, California, USA.

John R. Meyer, MS, DDS, STD, is a priest of the Opus Dei Prelature and is currently the Vicar of the Prelature in California, residing in San Francisco, California, USA.

Copyright Bioethics Press Spring 2008

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