Spring 2002 Vol. 2 No. 1
Little wonder that controversy has surrounded the topic of human reproductive cloning. Such a prospect brings into stark relief questions about who we are, what we might become, and how we should use new scientific advances. It also raises ethical considerations about certain types of related research.
Elected officials, with input from all segments of society, will have to make the fundamental ethical and public policy choices concerning cloning. The scientific community's role is to provide a clear understanding of what science actually says about the safety and feasibility of technologies that might be used to clone humans, as well as the possible implications that a ban on human reproductive cloning might have on stem cell research. For this purpose, the National Academies convened a panel to probe the scientific and medical aspects of human reproductive cloning -- with the hope that its report would provide useful input to decision-makers and the public.
After conducting a review of the relevant literature, the panel recommended that U.S. policy-makers ban cloning aimed at creating a child because it would be dangerous for the woman, fetus, and newborn -- and would most likely fail.
The need for a ban should be re-examined within five years, but it should be reconsidered only if a new scientific review indicates that the procedures are likely to be safe and successful, and if a broad national dialogue on societal, religious, and ethical issues suggests that reconsideration is warranted, the report says.
To date, sheep and five other mammalian species -- cattle, pigs, goats, mice, and cats -- have been cloned. The results of many of these experiments clearly illustrate the problems involved. Few cloning attempts are successful. Many clones die in utero -- even at late stages -- or soon after birth, and those that survive frequently have severe birth defects. Plus, female animals carrying cloned fetuses face serious risks, including the possibility of death. Human reproductive cloning is likely to have similar results, the panel concluded.
Human reproductive cloning is an assisted reproductive technology, which if successful would produce a newborn genetically identical to another person. The method used to initiate the procedure involves removing the nucleus of an egg cell and replacing it with the nucleus of a cell from an adult. The reconstructed egg is then stimulated to begin dividing, leading to the formation of a pre-implantation embryo -- or "blastocyst" -- made up of roughly 150 cells. If placed in a uterus, the blastocyst can implant and become a fetus, which may develop further and result in a newborn.
There is a related but different procedure, referred to as nuclear transplantation to produce stem cells. Unlike reproductive cloning, the aim of this procedure is to create embryonic stem cells only for clinical and research purposes and does not involve placing a blastocyst in a uterus.
The scientific and medical considerations that justify a ban on human reproductive cloning at this time do not apply to stem cell research, the panel said. Stem cells are unspecialized cells that can renew themselves indefinitely and, under the right conditions, develop into more mature cells with specialized functions. They could be powerful tools for medical research and improved therapies for treating disease. Still, a wide-ranging national dialogue on the societal, religious, and ethical issues concerning this area of study also is needed. The panel hopes its work will inform these broader considerations by all segments of society. -- Vanee Vines
Scientific and Medical Aspects of Human Reproductive Cloning. Panel on Scientific and Medical Aspects of Human Cloning; Committee on Science, Engineering, and Public Policy, Division on Policy and Global Affairs; Board on Life Sciences, Division on Earth and Life Studies (2002, 296 pp.; ISBN 0-309-07637-4; available from National Academy Press, tel. 1-800-624-6242; $35.00 plus $4.50 shipping for single copies).
The panel was chaired by Irving L. Weissman, Karel and Avice Beekhuis Professor of Cancer Biology, and professor of pathology and developmental biology, Stanford University, Stanford, Calif. The study was sponsored by the National Academies.