Stem Cell Research: An NPR Special Report
A 'Virtual Roundtable' on Federal Funding

Ihor Lemischka

Ihor Lemischka, associate professor, Department of Molecular Biology, Princeton University:

To begin, let me state very clearly that I am strongly in favor of continued federal funding for human embryonic and fetal stem cell research. I am very convinced that these types of studies are of great importance for biomedicine. I also know that many, if not most, of the great advances in biomedical research have come from publicly supported efforts. Given the completion of the human genome sequence, as well as other advances, the future for clinically important breakthroughs in biomedical science appears to be very bright.

I have arrived at my strong position in favor of stem cell research from a scientific point of view, as well as from the vantage point of my ethical and moral beliefs. Let me also state clearly that I respect the views of persons that do not morally or ethically agree with my position. From these points of view, I agree to disagree. I do not however, agree with those who would attempt to argue against human embryonic stem research from a scientific point of view. I will focus my comments on this issue.

Much has been made recently of the alleged plasticity of stem cells obtained from adult tissue sources. This has been used as an argument that adult stem cells are just as versatile as their embryonic counterparts; and therefore, circumvent the necessity of studying the latter.

It is very important to stress that although the reports concerning the abilities of adult stem cells are of great interest, they are relatively few; and in most if not all cases, the jury is still out regarding the scientific interpretation of the experimental observations. In addition, at least some of the reports have not yet been subjected to peer review, and consequently have not been published in the scientific press. Too often these days it seems that reports of new and exciting observations first appear in the popular press, and are considered by many as irrefutable. Peer review is only one of the standard requirements for the acceptance of experimental observations into the realm of valid science. While it is likely that many of these reports will be validated by the peer review process, before this actually occurs, the results must be considered as preliminary.

A second important criterion by which experimental observations become valid parts of scientific knowledge is their reproducibility by numerous independent laboratories. This is crucial because no single laboratory is perfect, and often unforeseen complications arise in the experiments performed. In few, if any, cases have the exciting reports been adequately confirmed by independent laboratories. The main reason for this is that independent confirmations take time, and the novel observations are very recent. Nevertheless, without independent confirmation, any novel experimental result must be considered preliminary.

In summary, the novel reports of previously unsuspected abilities of adult stem cells have not yet met the full set of criteria required by sound scientific method. Much more work needs to be done before we can accurately estimate the properties of any stem cell population, including those obtained from adult tissues. Setting-up a situation where adult and embryonic stem cells are considered to be interchangeable is entirely premature.

An additional point: Without the ability to perform direct comparative studies, it will never be possible to rigorously ask if adult stem cells can substitute for those obtained from embryos. Already in the blood forming system, the most intensively studied and best described stem cell system, it is clear that adult and fetal stem cells will have significant differences in their functional abilities. We only know this because it has been possible to perform comparative studies. Such comparative studies need to be performed in the human system.

In summary, we simply do not know the relative clinical usefulness of embryonic and adult stem cell populations. A prohibition of further research on one or the other source of stem cells will perpetuate our lack of knowledge.

Ihor Lemischka is an associate professor in the Department of Molecular Biology at Princeton University.

Other voices:
• Douglas Johnson, legislative director, National Right to Life Committee
• Micheline Mathews-Roth, MD, associate professor of medicine, Harvard Medical School
• Daniel Perry, executive director, Alliance for Aging Research
• David A. Prentice, founding member, Do No Harm: The Coalition of Americans for Research Ethics
• Arti K. Rai, assistant professor, University of Pennsylvania Law School