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The Truth About Stem Cells: An interview with Dr. David Prentice


David Prentice is a professor of life sciences at Indiana State University and an adjunct professor of medical & molecular genetics at the Indiana University School of Medicine. Dr. Prentice also services as an ad hoc science adviser to Kansas Republican Senator Sam Brownback.


Kathryn Jean Lopez: What impact do you think the Nobel laureates' letter to President Bush urging him to feed federal funds to human-embryo stem-cell research has had and will have?

David Prentice: I think the letter will have primarily PR value in the media. It perpetuates a number of misconceptions and misleading statements regarding stem-cell research, particularly embryonic as opposed to adult stem-cell research, and will serve to continue to cloud the issue. I believe President Bush and his staff are well aware of the truth about embryonic versus adult stem-cell research.

Lopez: Ultimately ideally, practically who should be making these decisions anyway? Most reasonable people will read the newspaper and see that Francis Crick and conservatives will see Milton Friedman signed this letter and will think, well, they must be right?

Prentice: An informed citizenry working with an informed legislative branch and an informed executive branch gives the best answer. Unfortunately, many in the public will read about this letter, recognize some high-profile "icons" or simply that there are a lot of "smart people" who've signed on, and think that they know all about this scientific research. Knowledgeable people do not always perpetuate the truth. President Bush and Congress obviously have the final say on how our federal research dollars will be spent. The hope is that all who are participating in this debate are fully informed about the facts and are not swayed by celebrities who are unfortunately ill-informed or deliberately misled, but rather weigh both the scientific and the ethical evidence.

Lopez: There is a lot of misinformation and deception going on in the press accounts of the "stem-cell debate," isn't there?

Prentice: This is probably the worst problem in this whole debate, the perpetuation (innocent or not) of misleading statements which obscure many of the real facts. The Nobel Laureate letter itself is a prime example of the "mixmaster" treatment of the facts. What is usually lacking from press reports are a few key "adjectives" that clarify the situation defining whether the cells discussed are human or animal cells, and especially whether they are "embryonic" or "adult" stem cells.

For example, the letter sent to President Bush says that "insulin-secreting cells have normalized blood glucose in diabetic mice." These experiments were done with ADULT stem cells from mice, NOT embryonic stem cells. In fact, there are as yet no reports of anyone being able to produce insulin-secreting cells from human embryonic stem cells, but human ADULT stem cells that secrete insulin HAVE been isolated.

The letter promulgates the claim (made repeatedly in NIH documents) that adult stem cells do not have the same potential as embryonic stem cells, which in theory can form any tissue. But studies done with adult stem cells (studies which mirror the ones done with embryonic stem cells) DO show that adult stem cells have the capacity to form essentially any tissue.

The most misleading term which continues to be used is "pluripotent." Literally, this means able to form most (but not all) tissues. This term continues to be used incorrectly, primarily to imply that human embryonic stem cells can form all human tissues except "trophoblast" tissue this is an essential outer layer of cells in the early embryo which allows it to implant into the uterine wall and nourishes early development. The trophoblast is also the part of the embryo removed in its destruction to harvest the inner embryonic stem cells. The phrase "human pluripotent stem cells" has been used to counter the question of whether human embryonic stem cells in culture could actually reform a human embryo, implying that this is not possible. Yet in testimony before the Senate, then-Director of the NIH, Harold Varmus, said that this possibility was uncertain, and that in fact it would be unethical to attempt such an experiment to determine whether this was possible. Enter the term pluripotent if the embryonic stem cells cannot form trophoblast, they cannot form an embryo. Mouse embryonic stem cells cannot form trophoblast tissue. BUT, as stated in Thomson's original paper in 1998, human embryonic stem cells CAN form trophoblast in culture.

Lopez: There are other ways to get stem cells, besides embryos, aren't there? Are they just as good?

Prentice: There are several excellent alternatives to embryos, and they are actually better potential sources of stem cells for numerous reasons. The best sources are from our own organs termed "adult stem cells" or "tissue stem cells." Another excellent source is cord blood; the small amount of blood left in an umbilical cord after it is detached from a newborn is rich in stem cells. In the last two years, we've gone from thinking that we had very few stem cells in our bodies, to recognizing that many (perhaps most) organs maintain a reservoir of these cells.

We've known for some time that bone-marrow stem cells can make more blood, but now we know that these adult stem cells can also make bone, muscle, cartilage, heart tissue, liver, and even brain. Interestingly enough, we now know that our brain contains stem cells which can be stimulated to make more neurons, or to take up different job descriptions as muscle or blood. Bone marrow and cord blood are already successfully being used clinically, while clinical use of embryonic stem cells is years away. Current clinical applications of adult stem cells include treatments for cancer, arthritis, lupus, and making new corneas, to name a few.

One distinct advantage of using our own adult stem cells is that there will be no transplant rejection, since it is our own tissue. Use of human embryonic stem cells will require lifelong use of drugs to prevent rejection of the tissue. Or, the patient will have to be cloned (a second ethical issue!), and that embryo (the patient's twin) sacrificed to obtain the embryonic stem cells for the tissue (essentially creating a human being whose only purpose is to be "harvested").

Another advantage of adult stem cells might be considered from a manufacturing viewpoint: A 2-step manufacturing process is more direct and has much less likelihood of a problem than a 10-step process. Adult stem cells have shown success at forming many specific tissues so far, certainly more than human embryonic stem cells in the laboratory. And as one researcher noted regarding human embryonic stem cells: "We thought from the first that problems would arise using hPSCs [human pluripotent stem cells] to make replacement tissues," indicating that the early stage cells are both difficult and slow to grow. "More important, there's a risk of tumors. If you're not very careful when coaxing these early cells to differentiate to form nerve cells and the like you risk contaminating the newly differentiated cells with the stem cells. Injected into the body, [embryonic] stem cells can produce tumors." No such problems exist with adult stem cells.

Lopez: To what extent are we exploring those options?

Prentice: Several scientists are investigating uses of adult stem cells to form new tissues or repair damaged/diseased tissue, such as for diabetes, Alzheimer's, Parkinson's, and stroke. As mentioned before, others are already using bone marrow and cord blood, as well as corneal tissue, for clinical applications. But the number of researchers in this area is still small, as is the amount of grant dollars needed to fund the research. And sadly, embryonic stem cells have been held up as the panacea for disease and a fountain of youth, despite the advantages of adult stem cells both scientifically and ethically. Given that adult stem cells have shown themselves to be scientifically more successful than embryonic stem cells, and ethically palatable, much more needs to be heard and said about adult stem cells, and much more funding needs to go to adult stem-cell research.

Lopez: Do members of Congress understand this debate? Are you confident that people in the administration do especially to offset HHS secretary Tommy Thompson, who is personally for research on human embryos for this purpose.

Prentice: Some members of Congress have made it a point to be well informed in the real facts of this issue, particularly Sen. Sam Brownback. Many, however, have received blended or deceptive information, and have been misled as to the capabilities of adult stem cells and the scientific disadvantages of embryonic stem cells.

Lopez: What should pro-life groups be doing to get the real story out-about alternative sources? And, simply, what their argument against this research is, so it isn't simply caricatured in the press?

Prentice: First INFORM YOURSELF WITH THE FACTS on the alternatives, as well as the facts (rather than the hype) about embryonic stem cells. Do No Harm, the Coalition of Americans for Research Ethics, has a wealth of articles about the alternatives on their website, plus links to other sources. Then tell your family, friends, neighbors, any groups to which you belong, and especially your Senators and your Representative. Impress on them that there is more to the story than is usually told, and urge them to check out the real difference in results between embryonic and adult stem cells, the promises versus the reality. And INSIST that the media tell the full story, complete with all of the adjectives and the evidence.

Human embryonic stem-cell research is illegal, immoral, and unnecessary.

It is ILLEGAL regarding use of federal funds because Congress has stated that no funds should be used for research which involves the creation or destruction of human embryos for research purposes, and human embryos are destroyed in the process of deriving human embryonic stem cells.

It is IMMORAL, because human beings are killed in the process. Scientifically there is no disputing that we are a human being even at the one-cell stage. It has never been acceptable to sacrifice one set of human lives for the potential benefit of others (and they are only potential benefits at this point.) Human embryonic stem cell research assigns different values to different human beings, designating some as people and some as property.

It is totally UNNECESSARY. Ethical alternatives exist such as adult stem cells which have already shown much more promise than embryonic cells, these results for adult stem cells are fully detailed in the scientific literature, and that adult stem cells are already being used clinically, making good on the potential that embryonic stem cells only promise.


Lopez, Kathryn Jean "The Truth About Stem Cells An interview with Dr. David Prentice." National Review (February 26, 2001).

Reprinted with permission of the National Review.


Kathryn Jean Lopez is associate editor at the National Review.

Copyright 2001 National Review




Copyright 2004 Victor Claveau. All Rights Reserved