CHAPTER FIVE
Findings and Recommendations

Stem cell research offers unprecedented opportunities for developing new treatments for debilitating diseases for which there are few or no cures. Stem cells also present a new way to explore fundamental questions of biology, such as determining the basic mechanisms of tissue development and specialization, which will be required for the development of therapies. However, our society holds diverse views about the morality of using early embryos for research, and we find ourselves searching for a consensus on how to proceed with this new avenue of research. Provocative and conflicting claims about the biology and biomedical potential of adult and embryonic stem cells have been made both inside and outside the scientific community. The committee considered those claims in light of the meaning and importance of the preliminary data from recent stem cell experiments. The following findings and recommendations constitute the final result of the committee’s deliberations on these issues.

Finding 1: Experiments in mice and other nonhuman animals are necessary but not sufficient for medical advances in human regenerative medicine. There are substantial biological differences between animal and human development and between animal and human stem cells, although the full range of similarities and differences is not understood.

Recommendation: Studies with human stem cells are



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Stem Cells and the Future of Regenerative Medicine CHAPTER FIVE Findings and Recommendations Stem cell research offers unprecedented opportunities for developing new treatments for debilitating diseases for which there are few or no cures. Stem cells also present a new way to explore fundamental questions of biology, such as determining the basic mechanisms of tissue development and specialization, which will be required for the development of therapies. However, our society holds diverse views about the morality of using early embryos for research, and we find ourselves searching for a consensus on how to proceed with this new avenue of research. Provocative and conflicting claims about the biology and biomedical potential of adult and embryonic stem cells have been made both inside and outside the scientific community. The committee considered those claims in light of the meaning and importance of the preliminary data from recent stem cell experiments. The following findings and recommendations constitute the final result of the committee’s deliberations on these issues. Finding 1: Experiments in mice and other nonhuman animals are necessary but not sufficient for medical advances in human regenerative medicine. There are substantial biological differences between animal and human development and between animal and human stem cells, although the full range of similarities and differences is not understood. Recommendation: Studies with human stem cells are

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Stem Cells and the Future of Regenerative Medicine essential to make progress in the development of treatments for human disease, and this research should continue. Finding 2: Current scientific data indicate that there are important biological differences between adult and embryonic stem cells and among adult stem cells found in different types of tissue. The therapeutic implications of these biological differences are not clear, and additional scientific data are needed on all stem cell types. Adult stem cells from bone marrow have so far provided most of the examples of successful therapies for replacement of diseased or destroyed cells. Their potential for fully differentiating into other cell types (such as brain, nerve, and pancreas cells) is still poorly understood and remains to be clarified. In contrast, embryonic stem cells studied in animals clearly are capable of developing into multiple tissue types and capable of long-term self-renewal in culture, features that have not yet been demonstrated with many adult stem cells. The application of stem cell research to therapy for human disease will require much more knowledge about the biological properties of all types of stem cells. The best available scientific and medical evidence indicates that research on both embryonic and adult human stem cells will be needed. Moreover, research on embryonic stem cells will be important to inform research on adult stem cells, and vice versa. Recommendation: Although stem cell research is on the cutting edge of biological science today, it is still in its infancy. Studies of both embryonic and adult human stem cells will be required to most efficiently advance the scientific and therapeutic potential of regenerative medicine. Research on both adult and embryonic human stem cells should be pursued. Finding 3: Over time, all cell lines in tissue culture change, typically accumulating harmful genetic mutations. There is no reason to expect stem cell lines to behave differently. In addition, most existing stem cell lines have been cultured in the presence of nonhuman cells or serum that could lead to potential human health risks. Consequently, vigilant

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Stem Cells and the Future of Regenerative Medicine monitoring of the integrity of existing cell lines is essential. In addition, the generation of new stem cell lines is likely to be important to replace those that become inviable and to increase understanding of the impact of long-term cell culture. Recommendation: While there is much that can be learned using existing stem cell lines if they are made widely available for research, concerns about changing genetic and biological properties of these stem cell lines necessitate continued monitoring as well as the development of new stem cell lines in the future. Finding 4: High-quality, publicly funded research is the wellspring of medical breakthroughs. Although private, for-profit research plays a critical role in translating the fruits of basic research into medical advances that are broadly available to the public, the status of stem cell research is far from the point of providing therapeutic products. Without public funding of basic research on stem cells, progress toward medical therapies is likely to be hindered. In addition, public funding offers greater opportunities for regulatory oversight and public scrutiny of stem cell research. Recommendation: Human stem cell research that is publicly funded and conducted under established standards of open scientific exchange, peer-review, and public oversight offers the most efficient and responsible means to fulfill the promise of stem cells to meet the need for regenerative medical therapies. Finding 5: Conflicting ethical perspectives surround the use of embryonic stem cells in medical research, particularly where the moral and legal status of human embryos is concerned. The differing perspectives are difficult to reconcile. Given the controversial nature of research with fetal and embryonic tissues, restrictions and guidelines for ethical conduct of such research have been developed. Recommendation: If the federal government chooses to fund human stem cell research, proposals to work on human embryonic stem cells should be required to justify the decision on scientific

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Stem Cells and the Future of Regenerative Medicine grounds and should be strictly scrutinized for compliance with existing and future federally mandated ethical guidelines. Finding 6: The use of embryonic stem cells is not the first scientific advance to raise public concerns about ethical and social issues in biomedical research. Recombinant-DNA techniques likewise raised questions and were subject to intense debate and public scrutiny. In that case, a national advisory body, the Recombinant DNA Advisory Committee, was established at the National Institutes of Health to ensure that the research met with the highest scientific and ethical standards. Recommendation: A national advisory group composed of outstanding researchers, ethicists, and other stakeholders should be established at NIH to oversee research on human embryonic stem cells. The group should include leading experts in the most current scientific knowledge relevant to stem cell research who can evaluate the technical merit of any proposed research on human embryonic stem cells. Other roles for the group could include evaluation of potential risks to research subjects and ensuring compliance with all legal requirements and ethical standards. Finding 7: Regenerative medicine is likely to involve the implantation of new tissue in patients with damaged or diseased organs. A substantial obstacle to the success of transplantation of any cells, including stem cells and their derivatives, is the immune-mediated rejection of foreign tissue by the recipient’s body. In current stem cell transplantation procedures with bone marrow and blood, success hinges on obtaining a close match between donor and recipient tissues and on the use of immunosuppressive drugs, which often have severe and potentially life-threatening side effects. To ensure that stem cell-based therapies can be broadly applicable for many conditions and people, new means of overcoming the problem of tissue rejection must be found. Although ethically controversial, the somatic cell nuclear transfer technique promises to have that advantage. Other options for this purpose include genetic manipulation

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Stem Cells and the Future of Regenerative Medicine of the stem cells and the development of a very large bank of ES cell lines. Recommendation: In conjunction with research on stem cell biology and the development of potential stem cell therapies, research on approaches that prevent immune rejection of stem cells and stem cell-derived tissues should be actively pursued. These scientific efforts include the use of a number of techniques to manipulate the genetic makeup of stem cells, including somatic cell nuclear transfer.

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