On July 12, the Senate Appropriations Subcommittee on Labor, Health and Human Services, and Education held a hearing to examine alternative methods of deriving human embryonic stem cells. All four methods discussed at the hearing were highlighted in a white paper published in May by the President’s Council on Bioethics.
Chair Arlen Specter (R-PA) and Ranking Member Tom Harkin (D-IA) have introduced a bill (S. 471) that would allow the Department of Health and Human Services to conduct and support embryonic stem cell research. Under the bill, stem cells could be used for research if they were derived from embryos that have been donated from in vitro fertilization clinics. The House approved an identical bill (H.R. 810) on May 24 (see The Source, 5/27/05). Under current law, federal funds may be used for research on only 78 embryonic stem cell lines that were created before August 2001.
In his opening remarks, Sen. Specter said that the ban on federal funding “has impeded the National Institutes of Health from pursuing this very important subject,” adding, “There is great concern that we are not moving far enough or fast enough on scientific research…where stem cells could save lives. There is a battle between those who say that it is the destruction of human life, which I believe it is not…These embryos are created for in vitro fertilization, and those not used are discarded.” He noted that there are currently 400,000 frozen embryos that would be discarded if they are not donated for research.
Referring to one method in which the stem cells are derived from blastomeres by biopsy without destroying the embryo, Sen. Harkin stated, “I’m intrigued by this method. It seems worth pursuing. But we need to be clear about one thing as we listen to today’s testimony. There’s only one reason why this method has suddenly become so popular at the White House: They want to use it to defeat H.R. 810…They’re trying to convince Senators that instead of supporting H.R. 810, we should pin all our hopes on this blastomere method, or other so-called ‘ethical alternatives.’ They figure that if they can pull enough Senators off of H.R. 810, that will keep us from getting the 60 [votes] we need to stop a filibuster.”
Director of the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health James Battey explained that physicians at Columbia University “noted that during the human in vitro fertilization (IVF) process, there are numerous embryos that fail to continue to divide, and are therefore judged to be unsuitable for implantation. These non-dividing entities are deemed to be ‘dead,’ and they propose that harvesting cells from these embryos for the purpose of creating a [stem cell] line is no different than organ donation by a person judged to be ‘brain dead.’” Dr. Battey argued that “from a scientific perspective, there is no published study showing that it is possible to generate an embryonic stem cell line from a non-dividing, ‘dead’ embryo in rodents, non-human primates or humans,” adding, “If stem cell lines could be derived from such embryos, the resulting cell line would have to be carefully checked for karyotypic (genetic) abnormalities or other defects, which may have been the underlying cause of the embryo’s lack of development.”
Dr. Battey also discussed a method in which human somatic cells are reprogrammed back into pluripotent stem cells. “It may be possible at some time in the future to culture populations of somatic cells in the laboratory and reverse their differentiating process, enabling them to become pluripotent. Scientists may also identify the molecules in cells such as embryonic stem cells that are responsible for maintaining cells in a pluripotent state and use these factors to dedifferentiate somatic cells.” He further noted, “This proposal would raise ethical issues if the dedifferentiation process were to proceed too far and create a totipotent cell (a cloned human zygote).” Finally, Dr. Battey examined altered nuclear transfer, which would be described in more detail during the second panel. He explained that no one had successfully obtained a pluripotent stem cell line using this method, adding, “Embryonic stem cell derivations would need to undergo pilot experiments, first in rodents and then in non-human primates, to prove that this approach has merit and is technically feasible. If created, the stem cell lines would…have to be validated as authentic, with all the properties associated with self-renewing, pluripotent embryonic stem cell lines.” He also noted that this approach “is dependent upon the widespread acceptance…that the genetically modified entity created using this procedure is not, in fact, a human embryo.”
The subcommittee heard testimony from a member of the President’s Council on Bioethics, Dr. William Hurlbut of Stanford University. Highlighting altered nuclear transfer, he explained that the method “would draw on the basic techniques of somatic cell nuclear transfer, popularly known as therapeutic cloning, but with an alteration such that pluripotent cells are produced without the creation and destruction of human embryos.” Dr. Hurlbut also said that altered nuclear transfer “could provide a unique flexible tool and has many positive advantages that would help advance embryonic stem cell research. Unlike the use of embryos from IVF clinics, altered nuclear transfer would produce an unlimited range of genetic types for the study of disease, drug testing, and possibly generation of therapeutically useful cells.” Finally, he noted that his proposal “would advance our understanding of developmental biology and might serve as a bridge to transcendent technologies such as direct reprogramming of adult cells.”
Dr. Ronald Green, director of the Ethics Institute at Dartmouth College, addressed the use of single-cell blastomere biopsy to derive stem cells, explaining that the procedure “is widely used in the process of preimplantation genetic diagnosis (PGD) as a way of testing for genetic disorders before the embryo is transferred to a womb.” He explained that “the extraction of a single cell from the embryo at this stage does not appear to harm it or reduce its developmental potential. If this method could be applied to the extraction of a single cell for the creation of a human embryonic stem cell line, it could circumvent many of the ethical and legal objections to federal support for embryonic stem cell research.” He further stated, “Although banking a line of stem cells is arguably to the embryo’s benefit, it cannot be said with confidence at this time that removing a blastomere from an early embryo is to its net benefit or that it involves minimal risk. It will take additional research, which might be supported by federal funding, to determine the level of risk to embryos associated with single-cell blastomere biopsy.” Dr. Green concluded, “Although single-cell blastomere biopsy is an ethically attractive way of deriving stem cell lines, it should not be regarded as an alternative to current methods that use embryos remaining from infertility procedures, an approach that many citizens regard as ethically acceptable.”
Dr. George Daly, a professor at Harvard Medical School and a doctor at Children’s Hospital in Boston, testified on behalf of the American Society for Cell Biology. Explaining that his research involves both adult and embryonic stem cells, he stated, “In essentially all cases of adult stem cell therapy, we’re really talking about transplanting blood stem cells to treat leukemia, lymphoma, and genetic disease. Although bone marrow transplant has cured many lives, this form of adult stem cell therapy is not a certain cure. Even after many decades of clinical experience, bone marrow transplant remains an aggressive and toxic therapy that carries the highest mortality rate of any medical procedure that is routinely performed.” Dr. Daly said that his laboratory “is studying human embryonic stem cells in hopes of making blood stem cell transplants safe and more widely acceptable,” adding, “This strategy is working in mice, and we’re eager to translate the work into humans, but the current federal funding policies have held us back. Although it is true that no one to date has been treated with cellular therapies based on human embryonic stem cells, I can assure you that the mouse embryonic stem cells have had a major impact on medical research.” He expressed his support for H.R. 810, noting that the bill “would expand research opportunities and accelerate progress towards newer and better therapies for the many children I currently cannot treat successfully.”
