Why We Need Not Kill To Save Lives
Myths and realities of stem cell research:
Why We Need Not Kill To Save Lives
By Richard M. Doerflinger
In December 1998, when researchers announced that they had cultured human embryonic stem cells, scientists and politicians became starry-eyed over the medical promise of these cells. Their enthusiasm has obscured both the moral dimensions of the debate and the reality that the benefits they seek can be found in the use of morally acceptable alternatives.
Contrary to what has been repeated over and over again, human embryos are not the only source for stem cells.
Stem cells are fast-growing, unspecialized cells that can reproduce themselves, and also produce more specialized cells as needed. All the inner cell mass of a week-old human embryo is made up of these cells. This is why scientists wanted to obtain and destroy "spare" embryos [embryos created but not implanted] from in vitro fertilization clinics to create stem cell cultures.
Moral qualms about such destruction must be ignored, said proponents, because harvesting such cells from embryos is the only realistic way to produce cures for Parkinson's disease, diabetes, Lou Gehrig's disease, and other ravaging ailments.
But a great deal has changed in a year and a half. Startling alternatives to destructive embryo research have arrived that are far closer to helping patients some using adult stem cells, some using other approaches altogether.
In short, the choice between medical progress and moral principle is a false dilemma. We can pursue the cure of disease in morally acceptable ways.
As a consequence of further research it is clear that many irresponsible claims about the unique promise of embryonic stem cells must now be abandoned.
Claim: Stem cells cannot be found in most adult tissues.
Reality: For many years medical experts have used "hematopoietic" (blood-producing) stem cells from patients' bone marrow, especially in treatment of cancer and leukemia. Now stem cells have been found in a wide variety of adult tissues: neural stem cells in brain and other nerve tissue; "mesenchymal" stem cells that form new bone and cartilage in bone marrow; "epithelial" stem cells in skin and eye tissue that can be used to repair damaged corneas; and stem cells in the pancreas, muscle tissue, and so on. It seems live neural stem cells can be obtained from adult cadavers even hours or days after death (UniSci [unisci.com], April 28, 1999).
Claim: Embryonic cells are less likely to be rejected by the body's immune system.
Reality: The cells most fully protected from such rejection are a patient's own stem cells, which can be modified, stimulated, or grown in culture to repair damaged tissue. Rejection problems may also be less serious if fetal or neonatal stem cells (from placentas or umbilical cords from live births, or from bone marrow obtained after miscarriages) are used.
Because any foreign tissue, even embryonic cells, may lead to incompatible transplants, some embryo research proponents such as the Geron Corporation are moving toward the further abuse of making genetically matched embryos for each patient by cloning. Why not use the "genetically matched" cells in a patient's own body, instead of creating new human embryos who would be killed for such cells?
Claim: Adult stem cells can't be "immortalized" and multiplied in culture to the extent that embryonic cells can.
Reality: In the January 1999 Nature Genetics, University of Texas researchers reported that the enzyme telomerase can " immortalize" adult cell cultures without producing the uncontrolled growth of cancer cells. In July 1999, Department of Veterans Affairs researchers said they had maintained cultures of blood-producing stem cells from mice for several months, multiplying them a million-fold, by adding a growth factor called thrombopoietin. And in the March 28, 2000, Proceedings of the National Academy of Sciences, Dr. Darwin Prockop (now at Tulane University) reported on advances enabling his team to multiply human bone marrow stem cells a billion-fold in six weeks.
Claim: Only embryonic cells can be genetically modified to serve important new roles in the body.
Reality: In May 1999, researchers reported progress in genetically modifying patients' own hematopoietic stem cells so they will be more resistant to harm from high-dose chemotherapy (MSNBC, May 17, 1999). Dr. Micheline Mathews of Harvard Medical School has cured a rare genetic disease in mice by inserting the missing gene into their own stem cells. And in April 2000, French researchers reported in Science the first clear success in human gene therapy, curing severe combined immunodeficiency disease (SCID) in several children by inserting the missing gene into their bone marrow stem cells.
Claim: Adult cells may produce formless tissue, but only embryonic cells can be used to create whole organs.
Reality: The field of "tissue engineering" has taken off in recent years, forming increasingly complex organs by stimulating adult tissues to grow on artificial templates that are then discarded. Now an NIH-funded team at the University of Washington says it will use this new technology to grow a human heart from adult cells in 10 years (Agence France Presse, May 23, 2000).
Claim: Embryonic cells are "pluripotent," capable of forming a wide variety of different tissues, while adult stem cells can only create one or two narrowly defined types of cells.
Reality: Adult stem cells are vastly more versatile than once thought. Swedish researchers reported in the June 2 issue of Science that adult neural stem cells can produce many different cell types. They noted that other recent studies show that bone marrow stem cells transplanted to the brain can produce nerve tissue, and that blood-producing stem cells can produce muscle cells and vice versa. "Together with the data presented here," they conclude, "these studies suggest that stem cells in different adult tissues may be more similar than previously thought and perhaps in some cases have a developmental repertoire close to that of ES [embryonic stem] cells."
Claim: Even if they are more versatile than once thought, adult cells don't spontaneously create almost every type of cell as embryonic stem cells do.
Reality: Yes, and that makes them safer and more useful for treating patients than embryonic cells. Embryonic cells "turn into bone cells and knee cells," says I. Richard Garr of NeuralStem Pharmaceuticals in College Park, Maryland. "You can't put them in a person's head without being 100 percent sure they won't turn into these other things" (New York Times, May 30, 2000). That may be exactly what happened some years ago when a man received a fetal tissue transplant to treat his Parkinson's disease. Apparently the transplant used some tissue of an earlier gestational age than is generally used. The man died a year later because deposits of bone, skin, and hair tissue had filled the ventricles of his brain (Neurology, May 1996).
Adult stem cells only become different types of cells when they are given new signals to do so. Placed in their usual environment, they seem to produce only the cell types of that particular tissue which is exactly what is needed to repair such tissue safely. Thus, "besides skirting the ethical dilemmas surrounding research on embryonic and fetal stem cells, adult cells... might have another advantage: They may be easier to manage" (G. Vogel, in Science, Feb. 25, 2000).
Claim: Adult pancreatic cell transplants have proved a failure at treating diabetes, so embryonic cells are needed to advance toward a cure.
Reality: This is what the Juvenile Diabetes Foundation has said. But on May 18 of this year, University of Alberta researchers announced successful treatment of severe diabetes by providing patients with adult pancreatic islet cells producing insulin. The breakthrough was due to the use of cells from two adult cadavers for each transplant, and a new anti-rejection drug. Also, in the March 2000 issue of Nature Medicine, a University of Florida team announced successful treatment of diabetes in mice using adult pancreatic stem cells. "The next step is take this into humans," they said (Reuters, Feb. 28, 2000).
It is unclear what the future holds. Some research avenues may prove less promising than they now seem. At the same time, new avenues not anticipated now may be announced tomorrow. Only one thing is certain: The exaggerated claim that we must destroy human embryos to advance medical progress was not only morally obtuse but scientifically irresponsible.
Why We Need Not Kill To Save Lives
By Richard M. Doerflinger
In December 1998, when researchers announced that they had cultured human embryonic stem cells, scientists and politicians became starry-eyed over the medical promise of these cells. Their enthusiasm has obscured both the moral dimensions of the debate and the reality that the benefits they seek can be found in the use of morally acceptable alternatives.
Contrary to what has been repeated over and over again, human embryos are not the only source for stem cells.
Stem cells are fast-growing, unspecialized cells that can reproduce themselves, and also produce more specialized cells as needed. All the inner cell mass of a week-old human embryo is made up of these cells. This is why scientists wanted to obtain and destroy "spare" embryos [embryos created but not implanted] from in vitro fertilization clinics to create stem cell cultures.
Moral qualms about such destruction must be ignored, said proponents, because harvesting such cells from embryos is the only realistic way to produce cures for Parkinson's disease, diabetes, Lou Gehrig's disease, and other ravaging ailments.
But a great deal has changed in a year and a half. Startling alternatives to destructive embryo research have arrived that are far closer to helping patients some using adult stem cells, some using other approaches altogether.
In short, the choice between medical progress and moral principle is a false dilemma. We can pursue the cure of disease in morally acceptable ways.
As a consequence of further research it is clear that many irresponsible claims about the unique promise of embryonic stem cells must now be abandoned.
Claim: Stem cells cannot be found in most adult tissues.
Reality: For many years medical experts have used "hematopoietic" (blood-producing) stem cells from patients' bone marrow, especially in treatment of cancer and leukemia. Now stem cells have been found in a wide variety of adult tissues: neural stem cells in brain and other nerve tissue; "mesenchymal" stem cells that form new bone and cartilage in bone marrow; "epithelial" stem cells in skin and eye tissue that can be used to repair damaged corneas; and stem cells in the pancreas, muscle tissue, and so on. It seems live neural stem cells can be obtained from adult cadavers even hours or days after death (UniSci [unisci.com], April 28, 1999).
Claim: Embryonic cells are less likely to be rejected by the body's immune system.
Reality: The cells most fully protected from such rejection are a patient's own stem cells, which can be modified, stimulated, or grown in culture to repair damaged tissue. Rejection problems may also be less serious if fetal or neonatal stem cells (from placentas or umbilical cords from live births, or from bone marrow obtained after miscarriages) are used.
Because any foreign tissue, even embryonic cells, may lead to incompatible transplants, some embryo research proponents such as the Geron Corporation are moving toward the further abuse of making genetically matched embryos for each patient by cloning. Why not use the "genetically matched" cells in a patient's own body, instead of creating new human embryos who would be killed for such cells?
Claim: Adult stem cells can't be "immortalized" and multiplied in culture to the extent that embryonic cells can.
Reality: In the January 1999 Nature Genetics, University of Texas researchers reported that the enzyme telomerase can " immortalize" adult cell cultures without producing the uncontrolled growth of cancer cells. In July 1999, Department of Veterans Affairs researchers said they had maintained cultures of blood-producing stem cells from mice for several months, multiplying them a million-fold, by adding a growth factor called thrombopoietin. And in the March 28, 2000, Proceedings of the National Academy of Sciences, Dr. Darwin Prockop (now at Tulane University) reported on advances enabling his team to multiply human bone marrow stem cells a billion-fold in six weeks.
Claim: Only embryonic cells can be genetically modified to serve important new roles in the body.
Reality: In May 1999, researchers reported progress in genetically modifying patients' own hematopoietic stem cells so they will be more resistant to harm from high-dose chemotherapy (MSNBC, May 17, 1999). Dr. Micheline Mathews of Harvard Medical School has cured a rare genetic disease in mice by inserting the missing gene into their own stem cells. And in April 2000, French researchers reported in Science the first clear success in human gene therapy, curing severe combined immunodeficiency disease (SCID) in several children by inserting the missing gene into their bone marrow stem cells.
Claim: Adult cells may produce formless tissue, but only embryonic cells can be used to create whole organs.
Reality: The field of "tissue engineering" has taken off in recent years, forming increasingly complex organs by stimulating adult tissues to grow on artificial templates that are then discarded. Now an NIH-funded team at the University of Washington says it will use this new technology to grow a human heart from adult cells in 10 years (Agence France Presse, May 23, 2000).
Claim: Embryonic cells are "pluripotent," capable of forming a wide variety of different tissues, while adult stem cells can only create one or two narrowly defined types of cells.
Reality: Adult stem cells are vastly more versatile than once thought. Swedish researchers reported in the June 2 issue of Science that adult neural stem cells can produce many different cell types. They noted that other recent studies show that bone marrow stem cells transplanted to the brain can produce nerve tissue, and that blood-producing stem cells can produce muscle cells and vice versa. "Together with the data presented here," they conclude, "these studies suggest that stem cells in different adult tissues may be more similar than previously thought and perhaps in some cases have a developmental repertoire close to that of ES [embryonic stem] cells."
Claim: Even if they are more versatile than once thought, adult cells don't spontaneously create almost every type of cell as embryonic stem cells do.
Reality: Yes, and that makes them safer and more useful for treating patients than embryonic cells. Embryonic cells "turn into bone cells and knee cells," says I. Richard Garr of NeuralStem Pharmaceuticals in College Park, Maryland. "You can't put them in a person's head without being 100 percent sure they won't turn into these other things" (New York Times, May 30, 2000). That may be exactly what happened some years ago when a man received a fetal tissue transplant to treat his Parkinson's disease. Apparently the transplant used some tissue of an earlier gestational age than is generally used. The man died a year later because deposits of bone, skin, and hair tissue had filled the ventricles of his brain (Neurology, May 1996).
Adult stem cells only become different types of cells when they are given new signals to do so. Placed in their usual environment, they seem to produce only the cell types of that particular tissue which is exactly what is needed to repair such tissue safely. Thus, "besides skirting the ethical dilemmas surrounding research on embryonic and fetal stem cells, adult cells... might have another advantage: They may be easier to manage" (G. Vogel, in Science, Feb. 25, 2000).
Claim: Adult pancreatic cell transplants have proved a failure at treating diabetes, so embryonic cells are needed to advance toward a cure.
Reality: This is what the Juvenile Diabetes Foundation has said. But on May 18 of this year, University of Alberta researchers announced successful treatment of severe diabetes by providing patients with adult pancreatic islet cells producing insulin. The breakthrough was due to the use of cells from two adult cadavers for each transplant, and a new anti-rejection drug. Also, in the March 2000 issue of Nature Medicine, a University of Florida team announced successful treatment of diabetes in mice using adult pancreatic stem cells. "The next step is take this into humans," they said (Reuters, Feb. 28, 2000).
It is unclear what the future holds. Some research avenues may prove less promising than they now seem. At the same time, new avenues not anticipated now may be announced tomorrow. Only one thing is certain: The exaggerated claim that we must destroy human embryos to advance medical progress was not only morally obtuse but scientifically irresponsible.
posted by R7 | 8/18/2004 02:39:00 AM
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