The Heart of the Matter: Stem Cell Research


Our series “The Heart of the Matter” features interviews with experts on either side of a controversial issue, asking each the same questions to see where and on what grounds their arguments diverge. Participants are asked to limit their responses to 1-3 sentences.

Arguing in favor of embryonic stem cell research embryonic stem cell research is Renee Reijo Pera, Professor and Director of the Center for Human Embryonic Stem Cell Research and Education at Stanford. Arguing that such research destroys human life and is therefore unethical is William Hurlbut, Consulting Professor at the Neuroscience Institute at Stanford and a member of the President’s Council on Bioethics.

  1. When does human life begin? Does this question matter?

RP: This is a question that has been addressed by major philosophers and theologians over the centuries, with answers ranging from conception to time points during development to birth. Personally, my belief is that human life is a continuum. The sperm and egg that gives rise to an individual are themselves living cells, part of another individual and at no time does human life end and begin again.

WH: A human embryo, even at the single-cell stage, is just the first step in an unbroken continuity of life that begins with fertilization (or twinning) and ends in natural death. This natural potential for human development makes the destruction of human embryos a matter of ethical concern.

  1. Does embryonic stem cell research destroy human life?

RP: Human embryonic stem cells are all derived from embryos that would never give rise to a child and therefore human embryonic stem cell research does not destroy any life. These embryos are often not of sufficient quality to be used for reproduction or are extras from couples who successfully bore children using other embryos. Despite suggestions that couples could adopt out these embryos, so far that is not something that potential parents have been willing to consider.

WH: Yes, by current methods, the procurement of ESCs requires the destruction of human embryos. However, ESCs themselves do not have the moral status of a human life because they are merely “pluripotent,” meaning they have the capacity to give rise to all the cell types of the human body but not the coherent and integrated unity of a living organism, which requires a “totipotent” embryo. Drawing on this distinction, in May 2005 the President’s Council on Bioethics laid out four proposals for obtaining “pluripotent stem cells” with the same characteristics and potential as ESCs, but without the destruction (or even endangerment) of human embryos.

  1. Is ESC research that destroys embryos ethically problematic?

RP: It would be ethically very problematic if hESC research used embryos that were intended for reproduction, but that is not the case. Each year, more than 1 million embryos are produced in IVF clinics in the United States, approximately 40% of which will not be of sufficient quality to be used for reproduction and will be discarded. Given the choice of discarding the embryos or using them to find cures for diseases, ESC research is an ethical choice.

WH: Yes, because the principle of valuing human life as the fundamental good serves as the cornerstone of law for our civilization. In no circumstance is the intentional destruction of the life of an innocent individual deemed morally acceptable. Even where a right to abortion is given, for example, it is based on a woman’s right not to be encumbered—a right of privacy, not a right to directly kill the fetus – and if the fetus is delivered alive during an abortion, there is a legal obligation to resuscitate and sustain its life.

  1. How would you compare the medical gains thus far from ESC research and adult stem cell research?

RP: These are not comparable at this time. Human ESC research began only in 1998, with the research since that time being limited in scope due to federal bans on funding. Treatments based on adult stem cells, especially hematopoietic stem cells, are already in the clinic in part because the research has been underway much longer and because the work has been continuously funded.

WH: Like human life itself, the study of stem cells of all types is a single and inseparable project with a relationship between all of the individual phases and parts. What we learn from pluripotent stem cell research will illuminate and complement our understanding of adult stem cell production and function. The medical gains from this research to biomedical science and clinical care are far more fundamental than the typical image of producing replacement cells for direct cell therapies.

  1. Purely as a scientific matter, how would you compare the promise of embryonic vs. adult stem cells?

RP: I would not be a human embryonic stem cell biologist if I did not believe the promise of embryonic stem cells to be one of the greatest in biology.

WH: Instead of using the term ‘embryonic stem cells,’ one should say ‘pluripotent stem cells,’ since this will include the full range of cells, regardless of source, that have the same properties and potentials as embryonic stem cells.

  1. Some politicians have suggested that ESC can help cure diseases like Parkinson’s and diabetes, while others say this is just grandstanding. Who is right?

RP: Probably both: I am quite certain that some politicians engage in “grandstanding.” However, the evidence suggests that a combination of approaches that includes embryonic stem cells may be part of a therapeutic strategy in the future that may alleviate or treat Parkinson’s and diabetes.

WH: We have just stepped onto Plymouth Rock, and we have a whole continent to explore. It would be foolish to make premature pronouncements concerning the promise of this fundamental research. One thing is clear: the study of pluripotent stem cells will illuminate many basic mechanisms of cell biology and thereby eventually contribute advancement across a broad front of clinical care.

  1. What is the potential of induced pluripotent stem cell (iPS) technology?

RP: iPSC technology is one of the major scientific advances to emerge from human embryonic stem cell research. It is a major advancement that many scientists, including those in my own laboratory, find intriguing and hope will lead to major progress in embryonic stem cell biology and our understanding of human genetics and development.

WH: Although the use of viruses and over-expression of genes make these cells problematic for direct cell therapies, scientists are working to overcome these problems. For the moment iPSCs seem to function well in laboratory studies as a substitute for ESCs.

  1. Does iPS eliminate the need for embryo destruction?

RP: Perhaps you mean to ask: Will iPSC technology be preferred over hESC or embryo-based research. iPSCs were generated through genetic modifications that make the cells unsafe for transplantation into humans, a limitation that will need to be overcome in order for the cells to become therapeutically useful. However, even if those obstacles are overcome, we will need to proceed with hESC research if we want to understand and diagnose early events in development that could have importance for our understanding of common disorders of imprinting and neurological function (such as autism), chromosomal abnormalities, and miscarriage.

WH: Last November James Thompson, the University of Wisconsin scientist who first isolated ESCs and has now contributed major advances in iPSCs, commented that it was a good feeling to have both started a field and ended it–namely, eliminated the role of ESCs. Since then he has revised this statement to say that for the moment at least we need ESCs as the ‘gold standard’ against which to compare the full equivalence of function of iPSCs.

  1. Do you find any ethical problems with the creation of hybrids with human embryos, such as that created in the United Kingdom in April?

RP: I find problems with the science and rationale for the experiments and so I don’t seek to support or justify the experiments further.

WH: Although this opens difficult ethical issues about what is created by this procedure, it is possible that the product of this unnatural laboratory construction bears little similarity in developmental potential to a natural human embryo. Rather than have a major social upheaval over this issue, as is currently happening in the U.K., it seems more reasonable to first do these studies with cow and monkey cells to see what is produced and whether such a product has any scientific uses.

  1. Five years from now, will ESC researchers be able to point to major medical breakthroughs?

RP: Some companies are already applying to begin the first clinical trials of therapies using ESCs. I think that within five years these or other potential therapies will have advanced to the next phase of clinical trials, the first step in being able to move to the clinic. Clinical trials for all new therapies, not just those based on ESCs, are carried out with a degree of caution that prohibits the treatment from making it to a clinic until it is proven to be safe and effective.

WH: I believe that within five years we will have well established sources of pluripotent stem cells from iPSCs, Altered Nuclear Transfer (my own proposal), or both, allowing full social support and rapid progress in this interesting and important field of research. The medical value of these studies will become increasingly evident as basic knowledge is translated into clinical application across a broad front from cancer, autoimmune disease and neurodegenerative disorders to broader interventions in regenerative medicine. Nonetheless, there will be an almost endless series of challenging ethical issues as the benefits of scientific studies with human embryos continues to collide with basic principles in the defense of developing life.

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