 |
 |
When a Cell Does an Embryo's Work, a Debate Is Born February 9, 1999: Six years ago, scientists in Canada published a remarkable paper. In it, they reported that they had grown entire mice from individual cells that they had plucked from mouse embryos. At the time, it was seen by those in the small world of mouse researchers as a technological tour de force. But now, as scientists are eyeing human embryo cells as material for research, the experiment is giving rise to a thorny philosophical question. If you can grow a mouse from a single embryo cell, you should in theory be able to grow a human from a single human embryo cell. And if you can grow a human from a single embryo cell, is that cell the moral equivalent of an entire embryo? Where, in other words, does the potential for human life lie? There are no simple answers anymore, ethicists say. "There's a certain ambiguity or complexity that wasn't appreciated before," said Dr. Thomas Murray, the director of the Hastings Center, an organization that studies ethical issues. But even debating the question is a political mine field, some experts say. The answers can determine whether scientists can go ahead with experiments on isolated human embryo cells that they hope will revolutionize medicine or whether they will be required to treat single human embryo cells with the same sort of restraint that they treat a human embryo. "People who hold a pro-life view regard the human embryo from the moment of conception as a fully protectable human being," said Dr. Ronald Green, director of the Ethics Institute of Dartmouth College. And so discussions of whether embryo cells are the equivalent of embryos or the equivalent of human tissue, like skin or muscle, are being carried out with the abortion debates looming in the background. "That's a tremendous pressure in these discussion," Green said. The mouse embryo cells that the Canadian scientists studied were of a special type, known as stem cells, that in theory can grow into any tissues or organs, although not -- most assumed until the experiment six years ago -- into an entire healthy mouse. Researchers have worked with mouse embryonic stem cells for years, but only recently have scientists been able to isolate human embryonic stem cells, a result that has profound implications. Scientists speak of learning to push human embryonic stem cells along a pathway to become a spongy bone marrow, brimming with red and white blood cells, or a pancreas that could squirt out insulin for a person with diabetes or a fresh new layer of skin for a burn patient. There is just one problem: the federal government bans the use of its money for research in which human embryos are destroyed or discarded. The question was, where does that leave embryo stem cells? In a recent decision, lawyers for the Department of Health and Human Services wrote that human embryonic stem cells were not included in the research ban. The reason, the National Institutes of Health wrote in a statement, was that the cells "are not an embryo as defined by statute" and that since human embryonic stem cells "do not have the capacity to develop into a human being, they cannot be considered human embryos consistent with the commonly accepted or scientific meaning of that term." Nonsense, says Dr. Lee Silver, a mouse geneticist at Princeton University. If what matters, as the government lawyers wrote, is "the capacity to develop into a human being," then human embryonic stem cells are the moral equivalent of embryos. "Metaphysically, it's all the same," Silver said. He thinks research with human embryo cells should be permitted but is offended, he said, by all the winking and nodding by scientists who do not want to admit the true potential of these cells to become a baby, if anyone wanted to try. Silver's position on the nature of stem cells is supported by Dr. Andras Nagy, the University of Toronto scientist who created mice out of stem cells six years ago in collaboration with a colleague, Dr. Janet Rossant. Nagy said that he saw no reason why a human embryonic stem cell could not become a human being. "I don't think there's a theoretical or practical impossibility of creating a completely stem-cell derived human being, if one wanted to do that." Others drew fine distinctions over what it meant to have a "capacity" to develop into a human being. They pointed out that Nagy and Dr. Rossant had to wrap their embryonic stem cells in a sort of artificial placenta when they dropped them into a female mouse's uterus. The "placenta" was a clump of genetically disabled cells that could not grow or become part of the developing fetus but could temporarily protect the stem cells and help them attach to the uterine wall. Dr. John Gearhart of the Johns Hopkins University School of Medicine, who led one of the two research groups that isolated human embryonic stem cells, said the real question was whether the stem cells by themselves could grow into a person. "The bottom line has to be that these cells in and of themselves are not capable of doing that," he said. He added that the genetically disabled cells "are absolutely essential," explaining that they "enable the embryonic stem cells to get through the very early stages of embryo development." "There is a real biological difference between an embryonic stem cell and a fertilized egg," said Dr. Brigid Hogan, a mouse embryonic stem-cell researcher at Vanderbilt University. The problem, said Green, is that people are still trying to use biology to draw moral lines in the sand, and biology just does not suffice anymore. Questions arise with cloning because then any cell of the body could, in theory, be used to make a new human being, Green said. And, he added, they arise with stem cells, because they could become a human being with a lot less laboratory manipulation. The result, he said, is that "the lines get very difficult to draw." "People like to think that the biology is going to tell us something definitive," Green said. But, he added, "the biology only poses decisions." by GINA KOLATA Copyright 1999 The New York Times Company http://www.nytimes.com/library/national/science/020999sci-embryo-cells.html janet paterson - 51 now /41 dx /37 onset - almonte/ontario/canada <http://www.newcountry.nu/pd/members/janet/index.htm> [log in to unmask]