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Why the Debate?
Stem cells are cells which are capable of reproducing indefinitely. Most types of stem cells, unlike ordinary body cells, can develop into other types of cells. This potential intrigues medical researchers hoping to cure many human diseases and injuries through replacing damaged, faulty, or missing body cells with stem cells. Treatments may one day be used to treat or cure conditions such as diabetes, Parkinson's disease, spinal cord injury and even paralysis.
But the use of some stem cells in research has sparked an ethical debate. The source of the controversy is the source of the cells. To understand the debate properly we'll explore how stem cells are obtained.
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Embryonic stem cells are cells taken from the inner cell mass of an embryo from four days to several weeks after fertilization. These stem cells are pluripotent, meaning they can develop into almost any body tissue. Some medical researchers hope this potency may mean they can one day be used in stem cell therapies for many different conditions.
Embryonic stem cells are obtained by killing the embryo. Some bioethicists believe that any human organism, even an embryo, is a human person with the same rights as any other person. To them, removing the inner cell mass and killing the embryo is equivalent to murder.
Other bioethicists do not see the embryo as having the full rights of a child or adult, but nevertheless find the destruction of embryos for research to be troubling. To them, the ethics of embryonic stem cells depends on the potential benefits. They perform a sort of ethical cost-benefit analysis, comparing the harm to the embryo to the good of the possible therapies that may one be developed.
Finally, some bioethicists do not consider the embryo to be anything but a potential person. They do not consider the use of embryonic stem cells to be any more troubling than the use of any other human tissue in research.
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Adult stem cells are obtained from tissues that have already undergone some degree of development. Despite the name, they come not only from adults, but from fetuses, newborns, and children as well.
One rich source of adult stem cells is the umbilical cord, an organ that naturally dies after birth. Removing stem cells from an umbilical cord after a baby has been born is therefore not controversial, as long as the parents consent to the procedure.
Another source is bone marrow. Several types of multipotent stem cells are found there. Obtaining bone marrow from a donor is a painful procedure that has some inherent risks, but if the donor (or the donor's legal guardian) gives informed consent, ethicists generally consider it acceptable.
As long as informed consent is obtained from a person (or from the person's legal guardian), the use of adult stem cells is uncontroversial because they can be obtained without killing an embryo, child, or adult.