Remaking ourselves? The ethics of stem-cell research.

In the first week of November, articles in both Science and the Proceedings of the National Academy of Science reported the stunning news that human stem cells have been isolated and cultivated. These cells are the precursors of the entire human body. The capacity to isolate and cultivate them means that we have the potential ability to produce tissue in the laboratory for use in generating new tissue, in developing new organs for transplantations, as well as cells for use in gene therapy.

In one line of research, the cells were taken from the inner cell mass of the blastocyst stage - one of the earliest stages in the development of the human preimplantation embryo. It is from these undifferentiated cells that the entire embryo and fetus will develop. These particular blastocyst cells were taken from preimplantation embryos left over from fertility treatments that were not going to be used in further in vitro fertilization attempts. In the second line of research, using aborted fetuses, the cells were taken from their embryonic germ cells that would not develop into specific body parts but into new eggs or sperm.

Herein lies the nub of the ethical issue: What is the moral status of the very early human embryo and of the tissue of an aborted fetus? In both lines of research, the teams of scientists recognize that the cells do have moral status since they come from human embryonic material. While I agree totally, 1 see a distinction between those cells drawn from the human preimplantation embryo and those obtained from aborted fetuses. While I do not agree with them, the group working on embryonic germ cells (the ones from aborted fetuses) claims that the use of these cells presents no particular problem because such cells could not be the precursor of a fetus; even so, they too recognize the special status of the human tissue.

I would argue that because the process of what biologists call differentiation has not yet occurred in the preimplantation embryo, such an entity is not individualized; it therefore lacks a core feature of personhood. This is so for two reasons: First, the cells in this entity have the capacity to become some (pluripotent) or any (totipotent) part of the body - and therefore the preimplantation embryo cannot be understood to be a single individual. For by definition, an individual is an entity that cannot be divided or, if it is, it becomes two halves neither of which can survive on its own. Second, the cells of the preimplantation embryo can be separated without harm to the organism (for example, in preimplantation diagnosis, one or two cells can be removed and examined for genetic disease). Further, the cells can be divided artificially to form twins. Finally, each of the cells has the potential to be another whole individual. My argument is that since the entity at this stage is not yet individualized, it lacks a critical, though not the only, criterion for personhood.

So how might we think of such an entity? Let me suggest an idea developed by the medieval philosopher Duns Scotus, though, of course, he had no clue about stem cells. His concept may help us get a handle on how to think about this entity in order to come to some ethical resolution about the development and use of embryonic stem cells. This argument does not apply to the use of embryonic germ cells, that is, to cells obtained from aborted fetuses, because individuation has already happened.

Scotus uses the term "common nature" to describe what is common to both the group and the individual. The term is part of his larger theory of knowledge and individualization. "Common nature" is essentially the basis for the definition of any entity, what all horses share in common, for example. But what horses share in common is indifferent to whether we are referring to a singular horse or to all horses. For Scotus, then, the common nature needs something else - an individualizing principle - to constitute a particular horse. Scotus's principle of individuation constricts, as he says, the form of this common nature into an individual, rendering this being unique, distinct from all others of the same species, and indivisible. In short, it has a singular unity; it is incapable of being divided into two wholes.

We can think of the preimplantation embryo as our common human nature for two reasons. First, even though this entity, is genetically distinct from its parents and even genetically unique, it is not yet individualized. Individualization does not occur until after the process of restriction is completed, some two weeks after the process of fertilization. To my mind, this process is a biological analogy to Scotus's concept of the principle of individuation, the constricting of the common nature into an individual. After the process is completed (normally after two weeks), the cells are committed to being specific cells in specific body parts. This is the biological beginning of true (though not full) individuality and, I would argue, marks a critical ethical line.

However, prior to that time, these human cells are indifferent to becoming specific cells in this particular body. They are not, I would argue, morally privileged by virtue of individuality or, a fortiori, by personhood. True, they are morally privileged by being human cells, cells that manifest the human genome, and as such are an entity that represents the essence of human nature. This is the second reason why the preimplantation embryo can be understood in terms of Scotus's "common nature." Essentially such research would be utilizing cells that in fact represent what is common to humans in the most basic sense; our common human nature in the blastomere is preindividual and prepersonal. And because these cells are our common human nature and not individualized human nature (the minimal definition of personhood), I argue that cells from this entity may be used in research to obtain and develop stem cells for use in transplantation or to develop specific human tissue or perhaps even organs.

Clearly those from whom such entities come must consent to this research, and the blastomeres must be handled with respect. But ultimately, such research is not research on a human person. It is research on our common human nature, and as such is morally justifiable.

RELATED ARTICLE: The cows come home

The announcement (New York Times, November 12, 1998) that scientists have implanted a human nucleus in the enucleated egg of a cow - have in fact produced a hybrid entity that is largely but not entirely human - demonstrates not only the speed at which such research moves but also the-ever-more complicated ethical tangles into which we have gotten ourselves.

Can we slow this down a little so that we can think about what we are doing?

Creating stem cells by fusing human cells with cow eggs is qualitatively different from other kinds of stem-cell research because we really don't know what will happen until we do it. Even though the human material reportedly took over rapidly and began producing human proteins, the interaction between bovine cytoplasm and human DNA cannot be fully modeled mathematically. And there are at least two other problems. If bovine mytrocondrial DNA remains in the cytoplasm, will it interact with the human DNA, and with what consequences? Will the blending of the two species be the occasion for cross-species diseases?

Although this particular research has not been verified or published, it was announced to test its public acceptability. While public reactions should certainly to be taken into account, what ethical method uses market research as a criterion? One would think that the company (Advanced Cell Technology of Worcester, Massachusetts) would want to argue that its research is both worthwhile and ethical, not simply that the public does not object to it.

If the bovine cytoplasm were to act only as a nutrient source, and if the human DNA were to take over totally, the resulting organism would have the human genome and would qualify as human. But that presents a whole new set of problems. For even though the technology was ostensibly developed to generate stem cells, other applications would be sure to follow - for example, a ready supply of bovine eggs for use in assisted human reproduction.

Who approved this research? Not the full Institutional Review Board at the University of Massachusetts, where the scientists work. It was given administrative approval without review. Because of its uniqueness and because it created a hybrid, I would argue that the experimentation should have had full review. And now, given the need to sift through all of the recently reported stem-cell research, I would further argue that there should be a moratorium on the hybrid research.

Still the barn door looks like it's open.

T.A.S.

Thomas A. Shannon is professor of religion and social ethics at Worcester Polytechnic Institute in Worcester, Massachusetts.