Where Do Stem Cells Come From?

There are three sources of stem cells: embryos, fetal germ cells, and adult peripheral stem cells. When a particular stem cell is grown in the laboratory to produce a colony for later use, the colony is called a stemcell line. In the U.S., the National Stem Cell Bank distributes these lines for researchers. In other countries, many private companies do so.

Embryonic stem cells (ESCs) are derived from fourto fivedayold embryos, which contain about 30 pluripotent cells. The embryos are generally taken from excess embryos from fertility clinics. Each time a woman has invitro fertility treatment, about a half dozen embryos are created. If the extra ones are not frozen for later use, they are destroyed. Currently, there are over 400,000 unused frozen embryos in U.S. fertility clinics. Since the rest would be destroyed anyway, it is considered ethical to use them for scientific research. ESCs are pluripotent and relatively easy to grow. However, the use of embryonic stem cells has run into tremendous opposition in the United States Religious organizations, in particular, feel that embryos or fetuses should have the same rights as humans do after birth. In their view, killing an embryo to use its tissue is equivalent to murder.

(They are also against IVF, because that typically involves discarding unused embryos; in other words, killing them.) President Bush has faced this dispute by trying an awkward compromise: to allow the use of current stemcell lines (which numbered just 25 useful lines at the time of his order) but prohibit development of more embryonic stemcell lines. He also sharply restricted further research. Other countries — notably Israel, Singapore, South Korea, and India — have no such qualms and are forging ahead in research.

It is estimated that the U.S. now lags three to four years behind these countries in stem cell research.

Fetal (or embryonic) germ cells are derived from socalled primordial germ cells, the cells that go on to produce sperm and eggs in adults. Germ cells are pluripotent stem cells. Less research has been performed on fetal germ cells, mainly because they are taken from fetuses that are deliberately aborted — an even more contentious issue in the U.S. Other countries are less interested in fetal germ cells because they are difficult to grow, and the differentiation into specialized tissue is much harder to control. Adults also have stem cells, which allow continued production and specialization of new cells. They are multipotent cells, although recent research shows that some may be pluripotent. These cells would be the ideal stem cells. However, they are extremely difficult to identify. At this time, there are two major ways of getting adult stem cells: from bone marrow and from umbilical cord blood.

Bonemarrow transplants are really a sort of stemcell therapy. Since the stem cells cannot be identified, a tube of marrow is extracted from a donor and put into the patient — hoping that it contains sufficient stem cells and that they will be accepted. The procedure is complex and expensive. Some types of health insurance will pay for it; otherwise, the patient has to pay upwards of $100,000 for the treatment. Bonemarrow transplants can be had for much less in other countries — it is a growing part of medical tourism — but it is still expensive. Since the fetus has a large number of stem cells, it makes sense that the placenta and umbilical cord would have some as well. These birth products used to be discarded. Now, some of the blood from the placenta and umbilical cord after birth is often kept as a rich source of hematopoietic (bloodforming) stem cells. Many people are banking umbilical cord blood for a supply of stem cells that could be used throughout the baby’s life should the need arise. Forprofit private storage cord blood banks will store a baby’s cord blood for use by that individual or a designated family member. The fee for private storage varies but averages about $1,500 initially plus $100 per year. This is also considerably cheaper overseas.

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Sheep Stem Cells? A number of border clinics in Mexico and elsewhere offer stemcell therapy at a huge discount. Closer inspection of their claims reveals that they inject, or administer orally, socalled “stem cells” from sheep. This is total fraud. Even if the cells were verified stem cells, injected sheep cells would be quickly destroyed by the human immune system. Any such cells taken orally would be quickly destroyed by stomach acids. These clinics are operated by charlatans, and their claims are highly suspect.

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