Three sources of stem cells
The controversy surrounding stem cell research is more about where the stem
cells come from than what they are being used for. There are 3 types of stem
cells, based on where they come from: adult, fetal, and embryonic.
Adult stem cells are found in the bodies of adults, often in the blood and bone marrow. These are the type of stem cells that are used in stem cell transplants for people with MS. Adult stem cells can be collected by taking blood or by using a needle to remove bone marrow, usually from the hip bone.
Fetal stem cells are found within a fetus, which is a developing baby aged 8 weeks or older. They can be collected from the placenta or the umbilical cord blood after birth. They may also be collected from a fetus that has been aborted.
Embryonic stem cells come from a newly fertilized egg that is six to eight days old. These stem cells are special because they can develop into any kind of cell within the body. Fetal and adult stem cells are more specialized – they can only divide into certain types of cells. For example, hematopoietic stem cells develop into blood cells. Embryonic stem cells may be harvested from leftover fertilized eggs from in vitro fertilization clinics.
What is – and isn't – controversial
The use of fetal and embryonic stem cells for research and treatment is where
most of the controversy and emotion lies. Harvesting adult stem cells has relatively
low risk to the donor, and does not destroy an embryo or fetus – it simply collects
some of the adult's cells, which the body will quickly replace. Using embryonic
stem cells means destroying the embryo. Those opposed to creating extra embryos
with the knowledge that some of the embryos will be discarded or used for research
instead of being implanted in a woman's uterus may also be concerned about embryonic
stem cell research. Using fetal stem cells from a terminated pregnancy also
raises a number of ethical issues. Those opposed to abortion are concerned that
finding a use for the terminated fetus may encourage abortion. On the other
hand, those not opposed to abortion may feel that the terminated fetus should
be used for medical research or treatment.
Since stem cell transplants for MS use adult stem cells, the stem cell controversy is less of an issue for this treatment.
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