Do ES Stem Cells Prevent Heart Disease?
The promise of stem cells, whether embryonic or adult, is in their power to differentiate into any type of somatic cell. Although adult stem cells have racked up an impressive number of therapeutic successes,* embryonic (ES) stem cells have only been promised to do so – until now. In Science Oct. 8,1 Cornell scientists coaxed embryonic stem cells to prevent a fatal heart defect in mouse embryos, but in an unusual way: they did not differentiate into heart tissues at all, but locally (in the blastocyst) and “from a distance” (via the mother’s circulatory system) secreted factors that stimulated the embryo to trigger the formation of its own cardiac cells. Three UC San Diego scientists, in the same issue,2 explain:
Unlocking the therapeutic potential of embryonic stem (ES) cells has remained a tantalizing but elusive goal. In this new era of “regenerative medicine,” the central experimental game plan has been predicated on driving the differentiation of ES cells along specific cell lineages (for example, neural, cardiac, endocrine), expansion and purification of the cell type of interest, and in vivo repopulation of damaged or degenerating organs by ES cell-derived differentiated cells. However, there are numerous hurdles to using ES cells as therapeutic tools. These include the need for reliable ES cell differentiation protocols for different cell lineages, purification techniques for the differentiated progeny, as well as ways to circumvent the immunological rejection of transplanted cells. Given the complexity of these multiple steps, it is not surprising that there are few clear examples of in vivo ES cell therapy for treating disease-related phenotypes. On page 247 of this issue, an exciting new study by Fraidenraich and co-workers1 expands the potential therapeutic repertoire of ES cells. These investigators provide direct evidence that ES cells can rescue otherwise lethal cardiac defects in mouse embryos. Intriguingly, the rescue effect is not subject to the differentiation of ES cells into the cardiac cell lineages that are normally associated with heart regeneration. Rather, the therapeutic effect of the transplanted ES cells depends on their secretion of defined factors that act either locally within the embryonic heart, or at a distance via the maternal circulation, to trigger fetal myocyte proliferation in utero.
Stem cells from an embryo face rejection because they do not belong to the individual being treated and are seen as invaders. In addition, they have a tendency to produce deformed embryos when injected into a blastocyst. Adult stem cells from the patient’s own tissues do not have the rejection problem, and undergo differentiation as expected. So while adult stem cell therapies have already demonstrated the differentiation of cells into other types, these ES cells in this study did not – they merely secreted substances that caused a mutated mouse embryo, which otherwise would have died before birth, to grow its own cardiac cells. In essence, the secreted factors only stimulated the mouse’s own genes to supply missing ingredients caused by the mutation. Since stem cell differentiation was not involved, and the stem cells did not get incorporated into the mouse tissues, what kind of benefit does this study promise for human therapies?
Given the potential of ES cells to induce the formation of teratomas (defective embryonic tissue), these findings do not necessarily suggest that administering ES cells to pregnant mothers will become a new therapeutic approach for treating congenital heart disease. However, given that a subset of maternal factors can cross the placenta, there remains a possibility that a subset of embryonic cardiac defects could be partially corrected by the careful delivery of the necessary proteins in the maternal circulation. Increasingly, congenital heart defects can be diagnosed accurately in utero with noninvasive imaging technology. In addition, ES cell-based assay systems may ultimately allow for the identification of likely candidate maternal factors that could correct a subset of severe human congenital heart defects.
The potential benefits of this study, therefore, appear tentative at best, while adult stem cells have a proven track record without ethical concerns.
*For examples, use the Search box with the phrase adult stem cells.
1Fraidenraich et al., “Rescue of Cardiac Defects in Id Knockout Embryos by Injection of Embryonic Stem Cells,” Science, Science, Vol 306, Issue 5694, 247-252, 8 October 2004, [DOI: 10.1126/science.1102612].
2Chien, Moretti and Laugwitz, “ES Cells to the Rescue,” Science, Vol 306, Issue 5694, 239-240, 8 October 2004, [DOI: 10.1126/science.1104769].
Big Science wants ES stem cell funding, and they jump on any tentative success with excitement unwarranted by the facts. If the ES cells do not differentiate, and only treat an prenatal condition that otherwise would be fatal, then they not only hold promise for living children or adults, but instead provide a reason for not aborting the embryo, because the stem cells might save it. Would the political liberals who support ES stem cell research want that?
In tonight’s second presidential debate, John Kerry dodged questions on both of these moral issues. In one case, he was asked point blank why, if adult stem cells already show success, we need embryonic stem cell research (see article on WorldNetDaily). He patronized the questioner with phony compassion about the deep moral convictions that motivated her question, then proceeded to ignore it. The only reason he gave for supporting federal funds for ES stem cell research was that Big Science says it wants it, and he wants to be a president that supports “science” (see 08/11/2004 editorial). President Bush, in rebuttal, reiterated the principle that guided his difficult decision on stem cells: a life should not be created to be destroyed, even to assist another life (see 09/03/2004 headline).
In another case, a questioner asked what Kerry would say to a voter who did not want her tax dollars used to support abortion. Again, he patronized the questioner but dodged the question. He said although he personally disliked abortion because he is Catholic, he cannot as a legislator impose his moral values on others. That was not what she asked. She asked why others’ moral values should be used to force her to pay her tax dollars on something that violates her moral values. For the questions Kerry should face without bluffing or dodging, read this article by Steven Ertelt on on LifeNews.com
Kerry also dodged the issue of his vote against the partial-birth abortion ban (six times), passed by both houses of Congress and signed by the President, but overruled by a federal judge. He said he had to oppose it, because it did not contain a provision for the life of the mother, in spite of the fact that the carefully-worded law specifically made that provision (see ACLJ website for documentation and history of the bill). The claim that the bill needed a provision for the “health of the mother” is a huge loophole. Health could mean anything – mental health, hangnails or a cold – and there is never a health reason for the grisly practice of sucking the brains out of a baby halfway born.
So this is the kind of “science-friendly” president the liberals are promoting, for less than moral reasons (see 09/27/2004 headline). Science and baloney do not go together. They are supposed to be opposites.