What about Other Sources of Stem Cells?

Because of the prominence of the embryo protection voices, some have thought that all ethical issues would disappear if only we could avoid destroying the blastocyst. Some argue that “adult” stem cells, if fully researched, are likely to hold the same benefit as embryonic stem cells. “Adult stem cells” refer to multipotent stem cells such as those found in the blood stream. They can be derived from living persons or umbilical cords and would not involve destruction of an early embryo. Here again, we note that the term “adult” may be misleading, for the just-born infant is considered an “adult” for purposes of adult stem cell research.

Others argue that adult stem cells will not solve the ethical issues. Adult stem cells are already partially differentiated, already designated for a limited range of tissue types. They are not pluripotent. To date, no credible experiments on adult stem cells have demonstrated that their value to regenerative medicine is equal to that of embryonic stem cells. Some studies have suggested that adult stem cells from one tissue type can migrate to and integrate into other tissues. However, it has not been demonstrated that these stem cells actually become the new tissue type; that is, it has not been demonstrated that they function as a stem cell of this new tissue type - they do not produce daughter cells of that tissue type nor do they appear to regenerate that tissue. In order for transplanted stem cells to be valuable for regenerative medicine they need to be capable of three things: 1) they must lodge in the host tissue, 2) they must become that tissue type, and 3) they must regenerate that tissue. As of this writing, only embryonic stem cells have demonstrated all three capabilities. Most scientists recommend that adult stem cell research continue, to be sure; but they recommend that embryonic stem cell research also be continued.

Because of this, several other proposals have been made. One suggests that stem cells might be derived from “organismically dead” embryos - those that were frozen following IVF and upon being thawed fail to divide. If they are declared organismically dead, then using them does not involve killing. Others have suggested that it may be possible to remove one or two cells from the inner cell mass in order to culture stem cells. Just as one or two cells are often removed from an IVF embryo in order to check for genetic disease, this process would not destroy the blastocyst. Still others have proposed that we might use science to create an organism that is genetically engineered so that it could not develop into a full-fledged human embryo or fetus. Or it might be possible to stimulate an egg into dividing without having fertilized it or used SCNT; thus, there is no “embryo” but only a dividing egg.

Two things should be noted about these proposals. First, it should be noted that their development attests to the significance of the embryo protection framework. Each represents a way of trying to avoid the problem of killing the early blastocyst. Second it should be noted that each of these proposals raises new and difficult ethical issues. For instance, removal of one or two cells from the inner cell mass might put that blastocyst at risk for anomalies if brought to birth. For this reason, the President’s Council rejects this option even though it avoids the ethical issue of killing an embryo.

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