Senate Democrats

Our Nation’s Top Scientists Emphasize That Recent Findings Do Not Eliminate the Need for Embryonic Stem Cell Research

Two teams of scientists, one in Japan at Kyoto University and one in the United States at the University of Wisconsin-Madison, have independently discovered a way to turn ordinary human skin cells into stem cells that appear to have the same characteristics as those derived from human embryos.  By introducing four genes known to play a role in making cells pluripotent,[1] the researchers were able to reprogram the cells so that they apparently behave like human embryonic stem cells.  Most recently, researchers at the Whitehead Institute for Biomedical Research in Massachusetts have used this new technique to cure mice of sickle cell anemia, establishing that these new cells have the potential to reverse an inherited, potentially fatal disease, and pointing to a promising future for this new technique. 

The technology used to create these cells, called induced pluripotent stem cells or “iPS” cells, holds great potential and is certainly worthy of additional exploration and funding.  Unfortunately, the Bush Administration and other opponents of embryonic stem cell research tout these studies as obviating the need for embryonic stem cell research.  It is important to note, however, that these studies are only a first step down a long road towards safe and effective clinical therapies.  We don’t know at this point whether these reprogrammed skin cells hold the same promise as stem cells derived from embryos.[2]  Meanwhile, embryonic stem cell research – using embryos that would otherwise have been discarded as medical waste – can be used today by researchers in the pursuit of curing diseases. 

That is why even the scientists responsible for these new studies agree that exploration of this new technique is a worthwhile pursuit as a complement to, but not as a substitute for, existing mechanisms for generating embryonic stem cells.  In fact, discovery of this new technique, touted by opponents of embryonic stem cell research as a panacea, would not have been accomplished without embryonic stem cell lines.  We need to do all we can today to help the millions of Americans who suffer from diseases or conditions that could be treated with therapies generated by stem cell research; they cannot afford to wait years for the development of an alternative approach that is still in its earliest stages and may not ultimately pan out.  The United States should support all ethical forms of stem cell research, without prejudging which ones will be most effective.

Embryonic stem cell research is about curing diseases and saving lives.  The isolation of human embryonic stem cells in 1998 was a major breakthrough in biology and opened a new frontier in medical research.  These cells have the unique ability to develop into virtually every cell and tissue in the body.  Harnessing this ability could enable researchers to one day cure disease and save lives.  Millions of people with debilitating diseases and disabilities stand to benefit from embryonic stem-cell therapy.  The possibilities of this research are giving hope to those with Parkinson’s disease, diabetes, spinal cord injuries, autoimmune diseases, osteoporosis, cardiovascular disease, and cancer. 

President Bush’s current stem cell policy is impeding embryonic stem cell research and the search for cures.  Under the President’s stem cell policy, federal funds cannot be used to support research on embryonic stem cell lines derived after August 9, 2001.  Fewer stem cell lines meet this criterion than the Bush Administration once claimed.  The lines that do meet the cutoff date are contaminated with mouse cells, and many are becoming unstable.  National Institutes of Health (NIH) officials report that fewer than 10 of the eligible lines are healthy enough to be used on a regular basis.  Moreover, scientists have had difficulty gaining access to the few eligible stem cell lines, and their very limited number has hindered research progress.  The President’s policy also creates tremendous financial and administrative burdens on states and research institutions, including universities across the country, that receive federal funding and wish to pursue research on newer stem cell lines. 

It’s entirely premature to suggest that the use of iPS cells can replace embryonic stem cells.  The technique used to create iPS cells holds great promise for creating patient- and disease-specific pluripotent stem cells for both research purposes and longer-term possible clinical use.  It is important to note, however, that these studies were conducted on mice.  While the iPS cells do seem to behave like embryonic stem cells in mice, mouse studies frequently fail to pan out in humans.[3]  Accordingly, we don’t know yet whether this approach will ever be viable for treating human diseases.  The technique also has shortcomings, most significantly, its use of retroviruses to insert the reprogramming genes into the cells’ chromosomes.[4]  Retroviruses are a type of virus that can cause mutations in cells, predisposing them to cancer.  To ensure iPS cells’ safety for therapy, methods to remove the vectors, the retrovirus used to ferry the genes into the skin cells, will need to be developed.[5]  More research is also needed to ensure that the cells do not differ from embryonic stem cells in a clinically significant or unexpected way.[6]  As the lead scientist on the Kyoto study asserts, progress toward socially beneficial applications of stem cell science would be indefensibly delayed if iPS cell research were pursued at the expense of further human embryonic stem cell research.[7]     

Without embryonic stem cell lines, the recent breakthroughs would not have been accomplished.  Without human embryonic stem cell lines, the Wisconsin and Kyoto researchers would not have known what the distinguishing characteristics of pluripotency are and, therefore, could not have accomplished their breakthroughs.[8]  Researchers need embryonic stem cells both as the gold standard for establishing and recognizing pluripotency, and accordingly, for determining whether the iPS stem cells can indeed function in the same manner as embryonic stem cells.[9]  Embryonic stem cell research is also essential for informing scientists’ further understanding and analyses of human iPS cells.[10]  In fact, both the U.S. and Japanese research teams that generated the iPS cells maintain that their work depended entirely on previous embryonic stem cell research.[11]  Expanded support of embryonic research is therefore necessary, not only in its own right, but to advance the science of iPS cells. 

Even if the new technique proves to be viable, certain areas of research require the use of embryonic stem cells.  There are important avenues of research that would be extremely difficult to pursue with iPS cells.  For example, while the technique used to produce iPS cells generates stem cells, it does not mimic the first days of human development, an area of study that could lead to advances in treating infertility or preventing birth defects.  Embryonic stem cells allow researchers to study the events that are critically involved in human fertility and in the chromosomal rearrangements that can lead to birth defects.  By continuing to pursue embryonic stem cell research, we can make important advances in women’s and prenatal health.[12]

President Bush’s misguided embryonic stem cell policy delayed the production of the new iPS cells for years.  The Bush Administration and other opponents of embryonic stem cell research claim that President Bush’s stem cell policy was the impetus for the development of iPS cells.  Far from inspiring the development of this new technique, the President’s misguided policy severely hindered progress in this field.  The scientists responsible for the recent breakthroughs assert that the controversy over embryonic stem cell research and the President’s restrictions delayed the production of iPS cells by four or five years.[13]

Our nation’s top stem cell experts, including those responsible for the recent findings, emphasize that embryonic stem cell research must continue.  Recognizing that the most successful proven method for creating pluripotent stem cells is to derive them from human embryos, our nation’s top cell biologists assert that recent advances in iPS cell research do not obviate the need for embryonic stem cell research. 

·                    Dr. James Thomson, co-author of the Wisconsin study and the individual who first isolated embryonic stem cells in 1998, writes in a recent op-ed, “We simply cannot invest all our hopes in a single approach.  Federal funding is essential for both adult and embryonic stem cell research, even as promising alternatives are beginning to emerge….  Further delays in pursuing the clearly viable option of embryonic stem cells will result in an irretrievable loss of time, especially if the new approach fails to prove itself.”[14]

·                    Dr. Rudolf Jaenisch of the Whitehead Institute for Biomedical Research and MIT, author of the study regarding use of the new iPS cells to cure sickle cell anemia in mice, emphasizes, “All the progress in this field was only possible because we had embryonic stem cells to work with first….   We need to make more [embryonic stem cells] and really define which are going to be the best ones for different applications.[15]

·                    Dr. Irving Weissman, director of the Institute for Stem Cell Biology and Regenerative Medicine at Stanford University, and Dr. Renee Reijo Pera, director of human embryonic stem cell research and education at Stanford, maintain that they intend to continue pursuing all avenues of embryonic stem cell research:  “We should not gamble on which method will prove best because patients who may have a narrow window of time for therapies depend on us to use the method that will get us their faster and best.”[16]

·                    Dr. Owen Witte, director of the Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, cautions, “It would be extremely foolish to place all of your bets on any single approach.[17]

·                    Dr. George Q. Daley, Associate Professor of Pediatrics and Biological Chemistry at Boston Children’s Hospital and Harvard Medical School, Associate Director of the Stem Cell Program at Children’s Hospital, and a member of the Executive Committee of the Harvard Stem Cell Institute, remarks, “Scientists are not going to just eagerly abandon embryonic stem cells because they have this alternative that seems to make other people happy…I’m frankly very worried that the policymakers are going to misinterpret the significance of this work.”[18]  

·                    Dr. Konrad Hochedlinger of the Harvard Stem Cell Institute and the Massachusetts General Hospital Center for Regenerative Medicine says of the iPS cells:  “There are still major hurdles that need to be overcome before thinking about replacing human embryonic stem cells with these cells.”[19]

·                    Dr. Doug Melton, Co-Director of the Harvard Stem Cell Institute, argues, “People will be saying this experiment suggests that we shouldn’t be using human embryos….  Until the alternative is shown to produce the same kind of extremely versatile, normal cells that we derive from previously frozen human [embryos], it would be unfair to patients to renounce that approach.”[20]

·                    Dr. Shinya Yamanaka, leader of the Kyoto University research team, and Dr. Rudolf Jaenisch, leader of the Massachusetts study, co-authored a recently-published letter emphasizing the need to continue human embryonic stem cell research.  The researchers wrote, “It would be a serious mistake to conclude that recent developments in iPS cell research (or, for that matter, any other so-called “alternative” source of pluripotent stem cells) avert the need for ongoing research on [human embryonic stem cells]….  We hold that research into all avenues of human stem cell research must proceed together.  Society deserves to have the full commitment of scientific inquiry at its service.”[21]  

Democrats will continue to fight to expand federally-funded embryonic stem cell research.   On June 20, President Bush vetoed S.5, the Stem Cell Research Enhancement Act, for the second time blocking legislation to expand the number of embryonic stem cell lines eligible for federally-funded research.  This legislation would support use of embryos that would otherwise be discarded to create stem cell lines — subject to strict ethical guidelines — that could one day cure disease and save lives.  This approach would merely allow embryonic stem cell research to vie for public funding like research into alternative sources of stem cells already can.  Both S.5 and the legislation vetoed by the President in the last Congress were approved by bipartisan majorities in both the House and the Senate, with nearly universal support from Democrats.  S.5 has the support of the overwhelming majority of Americans, as well as major medical and scientific associations, research universities and institutions, and dozens of patient advocacy organizations.   More than 100 million Americans suffer from diseases or conditions that could one day be treated with therapies derived from stem cell research.  The President’s veto is a devastating setback for them.  That is why Democrats will continue to fight to expand the President’s misguided policy.

For more information on this issue, see the following DPC Fact Sheets:  “NIH Director Agrees that Federally Funded Scientists Should Have Access to New Embryonic Stem Cell Lines” and “President Bush Blocks Legislation to Advance Stem Cell Research…Again.”




[1] Cells that are “pluripotent” have the intrinsic ability to generate all other types of tissue.

[2] Washington Post op-ed, December 3, 2007.

[3] Washington Post op-ed, December 3, 2007.

[4] Press Release, International Society for Stem Cell Research, November 21, 2007; Washington Post, December 7, 2007.

[5] News Release, University of Wisconsin-Madison, November 20, 2007.

[6] News Release, University of Wisconsin-Madison, November 20, 2007.

[7] Hyun, l., Hochedlinger, K., Jaenisch, R. and Yamanaka, S., “New Advances in iPS Research Do Not Obviate the Need for Human Embryonic Stem Cells,” Cell Stem Cell 1, October 2007.

[8] Moreno, Jonathan, Center for American Progress (Reprinted from Science Progress), November 26, 2007.

[9] Moreno, Jonathan, Center for American Progress (Reprinted from Science Progress), November 26, 2007.

[10] Nature editorial, November 29, 2007; Hyun, l., Hochedlinger, K., Jaenisch, R. and Yamanaka, S., “New Advances in iPS Research Do Not Obviate the Need for Human Embryonic Stem Cells,” Cell Stem Cell 1, October 2007.

[11] Washington Post op-ed, December 3, 2007; Nature editorial, November 29, 2007.

[12] Stanford Medical Center Report, November 28, 2007; News Release, Stanford University School of Medicine, November 20, 2007.

[13] New York Times editorial, December 1, 2007; Moreno, Jonathan, Center for American Progress (Reprinted from Science Progress), November 26, 2007.

[14] Washington Post op-ed, December 3, 2007.

[15] Washington Post, December 7, 2007.

[16] Stanford University School of Medicine News Release, November 20, 2007.

[17] Los Angeles Times, November 21, 2007.

[18] CQ Today, November 21, 2007.

[19] Harvard Science, November 20, 2007.

[20] Harvard Science, November 20, 2007.

[21] Hyun, l., Hochedlinger, K., Jaenisch, R. and Yamanaka, S., “New Advances in iPS Research Do Not Obviate the Need for Human Embryonic Stem Cells,” Cell Stem Cell 1, October 2007.

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