| Stem Cells | |
| Why do some people have such a problem with improving the human condition? | |
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| Stem Cell
Signals In October 2004, Robert Benezra, a researcher at the Memorial Sloan-Kettering Cancer Centre in New York, was studying mice that tended to die of a genetic heart defect as embryos. They were missing two proteins that are important for developing a healthy heart. To extend their lives, Benezra injected the mouse embryos with stem cells that had the missing proteins. "And it was to our surprise and amazement that when we injected even just a few embryonic stem cells, the animals not only survived a little bit longer but they were actually born and running around quite happily", says Benezra The
stem cells hadn't simply taken over and replaced the defective mouse heart
cells. Instead, the stem cells were actually sending chemical signals to the
defective cells around them that made the bad cells grow normally. |
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Is Heaven Populated Chiefly by the Souls
of Embryos? |
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Swiss endorse stem cell research
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Stem cells to cure incontinence
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At least we will always have true defenders of the human race: |
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The False Controversy of Stem Cells If you think it through, the case for embryonic research is an easy one By MICHAEL KINSLEY TIME Magazine, Monday, May. 31, 2004 Congratulations to representative Dana Rohrabacher, 56, and his wife Rhonda, 34, who gave birth to triplets last month. As we tend to suspect when a couple has triplets, the new parents used the services of a fertility clinic. Modern in-vitro techniques generally involve creating multiple embryos in the laboratory, transferring two or three and hoping that at least one will make it through to birth. Often it doesn't work. Sometimes it works unexpectedly well. Successful or not, the process creates many more embryos than babies. There is a built-in presumption — really, an intention — that even most of the transferred embryos will die. As for embryos that aren't transferred, they get destroyed or frozen indefinitely — unless, that is, they are used for stem-cell research. So it's interesting that Rohrabacher has changed his position on the medical use of embryonic stem cells. The California Republican was a supporter of President Bush's three-year-old policy severely restricting government-funded stem-cell research. But he signed a recent letter to Bush from 206 members of Congress urging the President to reconsider that policy. Bush says he won't reconsider. "Embryonic stem-cell studies are controversial because they involve the destruction of human embryos," the New York Times explained in a May 6 article reporting on the shifting politics of stem-cell research. (For example, Nancy Reagan, whose husband has Alzheimer's, has gone public with her opposition to the Bush restrictions.) But that can't be right. Fertility clinics destroy far more human embryos than stem-cell research ever would, yet they are not controversial. Death or deep freeze is the fate of any embryo spared by the Bush policy from the indignity of contributing to medical progress. Stamping some issue as controversial can be a substitute for thinking it through. In the case of embryonic-stem-cell research, thinking it through does not require further study or commissions of experts. This is one you can feel free to try at home. In fact, thinking it through is a moral obligation, especially if you are on the side of the argument that wants to stop or slow this research. It's not complicated. An embryo used in stem-cell research (and fertility treatments) is three to five days past conception. It consists of a few dozen cells that together are too small to be seen without a microscope. It has no consciousness, no self-awareness, no ability to feel love or pain. The smallest insect is far more human in every respect except potential. Is destroying that microscopic dot the exact moral equivalent of driving a knife through the heart of an innocent 6-year-old girl? Some stem-cell enthusiasts think that even antiabortion absolutists can support stem-cell research, since it uses surplus embryos that are doomed anyhow. But that logic would justify Nazi experiments on doomed Jews in the concentration camps. If the microscopic dot is a human being with full human rights, the answer is easy: no stem-cell research. But you don't have to be an abortion-rights advocate to reach the opposite conclusion. In fact, for abortion opponents whose views fall anywhere short of fanatical absolutism, the answer ought to be easy as well: full speed ahead. To the nonabsolutist, it ought to matter a lot that restricting stem-cell research doesn't actually spare the lives of any embryos. That means the lives of real people desperately awaiting the fruits of stem-cell research are being weighed against a purely symbolic message. It also ought to matter to the nonfanatic that embryos are needed only to start the research process. Most of the research and all the treatments that come out of it will use so-called lines developed out of a few initial stem cells in the laboratory. That makes the stem-cell issue different from — and easier than — the one about fetal tissues a few years ago. Fetal-tissue treatments use brain tissue from several aborted fetuses for each patient. An embryo used in stem-cell research has nothing resembling a brain. A difficult issue is one in which you hold two or more conflicting values. Stem cells are not a difficult issue: either you think a microscopic embryo has the same human rights as you and I, or you don't. Do you believe that a woman who gets an abortion should be prosecuted for murder, just like a mother who hires a professional killer to off her teenage son? Are you picketing around fertility clinics, which kill hundreds of thousands of unborn children — if that's what you believe a 5-day-old embryo to be — just like abortion clinics do? If so, you are entitled to oppose stem-cell research. If not, please get out of the way. |
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Out of the mouths of babes: |
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Of mice, men and in-between Scientists debate blending of human, animal forms By Rick Weiss The Washington Post Nov. 20, 2004 In Minnesota, pigs are being born with human blood in their veins. In Nevada, there are sheep whose livers and hearts are largely human. In California, mice peer from their cages with human brain cells firing inside their skulls. These are not outcasts from "The Island of Dr. Moreau," the 1896 novel by H.G. Wells in which a rogue doctor develops creatures that are part animal and part human. They are real creations of real scientists, stretching the boundaries of stem cell research. Biologists call these hybrid animals chimeras, after the mythical Greek creature with a lion's head, a goat's body and a serpent's tail. They are the products of experiments in which human stem cells were added to developing animal fetuses. Living test beds Chimeras are allowing scientists to watch, for the first time, how nascent human cells and organs mature and interact — not in the cold isolation of laboratory dishes but inside the bodies of living creatures. Some are already revealing deep secrets of human biology and pointing the way toward new medical treatments. But with no federal guidelines in place, an awkward question hovers above the work: How human must a chimera be before more stringent research rules should kick in? The National Academy of Sciences, which advises the federal government, has been studying the issue and hopes to make recommendations by February. Yet the range of opinions it has received so far suggests that reaching consensus may be difficult. During one recent meeting, scientists disagreed on such basic issues as whether it would be unethical for a human embryo to begin its development in an animal's womb, and whether a mouse would be better or worse off with a brain made of human neurons. "This is an area where we really need to come to a reasonable consensus," said James Battey, chairman of the National Institutes of Health's Stem Cell Task Force. "We need to establish some kind of guidelines as to what the scientific community ought to do and ought not to do." Beyond twins and moms Chimeras (ki-MER-ahs) — meaning mixtures of two or more individuals in a single body — are not inherently unnatural. Most twins carry at least a few cells from the sibling with whom they shared a womb, and most mothers carry in their blood at least a few cells from each child they have born. Recipients of organ transplants are also chimeras, as are the many people whose defective heart valves have been replaced with those from pigs or cows. And scientists for years have added human genes to bacteria and even to farm animals — feats of genetic engineering that allow those critters to make human proteins such as insulin for use as medicines. "Chimeras are not as strange and alien as at first blush they seem," said Henry Greely, a law professor and ethicist at Stanford University who has reviewed proposals to create human-mouse chimeras there. But chimerism becomes a more sensitive topic when it involves growing entire human organs inside animals. And it becomes especially sensitive when it deals in brain cells, the building blocks of the organ credited with making humans human. In experiments like those, Greely told the academy last month, "there is a nontrivial risk of conferring some significant aspects of humanity" on the animal. Greely and his colleagues did not conclude that such experiments should never be done. Indeed, he and many other philosophers have been wrestling with the question of why so many people believe it is wrong to breach the species barrier. Does the repugnance reflect an understanding of an important natural law? Or is it just another cultural bias, like the once widespread rejection of interracial marriage? Many turn to the Bible's repeated invocation that animals should multiply "after their kind" as evidence that such experiments are wrong. Others, however, have concluded that the core problem is not necessarily the creation of chimeras but rather the way they are likely to be treated. Imagine, said Robert Streiffer, a professor of philosophy and bioethics at the University of Wisconsin, a human-chimpanzee chimera endowed with speech and an enhanced potential to learn — what some have called a "humanzee." "There's a knee-jerk reaction that enhancing the moral status of an animal is bad," Streiffer said. "But if you did it, and you gave it the protections it deserves, how could the animal complain?" Unfortunately, said Harvard political philosopher Michael J. Sandel, speaking last fall at a meeting of the President's Council on Bioethics, such protections are unlikely. "Chances are we would make them perform menial jobs or dangerous jobs," Sandel said. "That would be an objection." A research breakthrough The potential power of chimeras as research tools became clear about a decade ago in a series of dramatic experiments by Evan Balaban, now at McGill University in Montreal. Balaban took small sections of brain from developing quails and transplanted them into the developing brains of chickens. The resulting chickens exhibited vocal trills and head bobs unique to quails, proving that the transplanted parts of the brain contained the neural circuitry for quail calls. It also offered astonishing proof that complex behaviors could be transferred across species. No one has proposed similar experiments between, say, humans and apes. But the discovery of human embryonic stem cells in 1998 allowed researchers to envision related experiments that might reveal a lot about how embryos grow. The cells, found in 5-day-old human embryos, multiply prolifically and — unlike adult cells — have the potential to turn into any of the body's 200 or so cell types. Scientists hope to cultivate them in laboratory dishes and grow replacement tissues for patients. But with those applications years away, the cells are gaining in popularity for basic research. The most radical experiment, still not conducted, would be to inject human stem cells into an animal embryo and then transfer that chimeric embryo into an animal's womb. Scientists suspect the proliferating human cells would spread throughout the animal embryo as it matured into a fetus and integrate themselves into every organ. Such "humanized" animals could have countless uses. They would almost certainly provide better ways to test a new drug's efficacy and toxicity, for example, than the ordinary mice typically used today. But few scientists are eager to do that experiment. The risk, they say, is that some human cells will find their way to the developing testes or ovaries, where they might grow into human sperm and eggs. If two such chimeras — say, mice — were to mate, a human embryo might form, trapped in a mouse. Not everyone agrees that this would be a terrible result. "What would be so dreadful?" asked Ann McLaren, a renowned developmental biologist at the University of Cambridge in England. After all, she said, no human embryo could develop successfully in a mouse womb. It would simply die, she told the academy. No harm done. But others disagree — if for no other reason than nothing else out of fear of a public backlash. "Certainly you'd get a negative response from people to have a human embryo trying to grow in the wrong place," said Cynthia B. Cohen, a senior research fellow at Georgetown University's Kennedy Institute of Ethics and a member of Canada's Stem Cell Oversight Committee, which supported a ban on such experiments there. How human? But what about experiments in which scientists add human stem cells not to an animal embryo but to an animal fetus, which has already made its eggs and sperm? Then the only question is how human a creature one dares to make. In one ongoing set of experiments, Jeffrey L. Platt at the Mayo Clinic in Rochester, Minn., has created human-pig chimeras by adding human-blood-forming stem cells to pig fetuses. The resulting pigs have both pig and human blood in their vessels. And it's not just pig blood cells being swept along with human blood cells; some of the cells themselves have merged, creating hybrids. It is important to have learned that human and pig cells can fuse, Platt said, because he and others have been considering transplanting modified pig organs into people and have been wondering if that might pose a risk of pig viruses getting into patient's cells. Now scientists know the risk is real, he said, because the viruses may gain access when the two cells fuse. In other experiments led by Esmail Zanjani, chairman of animal biotechnology at the University of Nevada at Reno, scientists have been adding human stem cells to sheep fetuses. The team now has sheep whose livers are up to 80 percent human — and make all the compounds human livers make. Zanjani's goal is to make the humanized livers available to people who need transplants. The sheep portions will be rejected by the immune system, he predicted, while the human part will take root. "I don't see why anyone would raise objections to our work," Zanjani said in an interview. Mice and men Perhaps the most ambitious efforts to make use of chimeras come from Irving Weissman, director of Stanford University's Institute of Cancer/Stem Cell Biology and Medicine. Weissman helped make the first mouse with a nearly complete human immune system — an animal that has proved invaluable for tests of new drugs against the AIDS virus, which does not infect conventional mice. More recently his team injected human neural stem cells into mouse fetuses, creating mice whose brains are about 1 percent human. By dissecting the mice at various stages, the researchers were able to see how the added brain cells moved about as they multiplied and made connections with mouse cells. Already, he said, they have learned things they "never would have learned had there been a bioethical ban." Now he wants to add human brain stem cells that have the defects that cause Parkinson's disease, Lou Gehrig's disease and other brain ailments — and study how those cells make connections. Scientists suspect that these diseases, though they manifest themselves in adulthood, begin when something goes wrong early in development. If those errors can be found, researchers would have a much better chance of designing useful drugs, Weissman said. And those drugs could be tested in the chimeras in ways not possible in patients. Now Weissman says he is thinking about making chimeric mice whose brains are 100 percent human. He proposes keeping tabs on the mice as they develop. If the brains look as if they are taking on a distinctly human architecture — a development that could hint at a glimmer of humanness — they could be killed, he said. If they look as if they are organizing themselves in a mouse brain architecture, they could be used for research. So far this is just a "thought experiment," Weissman said, but he asked the university's ethics group for an opinion anyway. "Everyone said the mice would be useful," he said. "But no one was sure if it should be done." © 2004 The Washington Post Company http://www.msnbc.msn.com/id/6534243/ |
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