Does Research Really Need Human Embryos and Cloning?
Neurobiologist Maureen L. Condic investigates 11 common arguments in favor of embryonic stem-cell research, and explains why science may not need the controversial technique, after all.
Claim: Good science demands that we investigate all avenues of inquiry.
False. “Good” research respects both scientific and ethical standards. Researchers' 2007 breakthrough in induced pluripotent stem cells, or iPSC, provides patient-specific stem cells that are the functional equivalent of embryonic stem cells. IPSC research meets every mark of good science and has the following ethical advantages: It does not destroy human embryos; it does not use human oocytes (eggs) harvested from women; and it does not alienate a large part of the country’s citizens by engaging in research that they find deeply immoral.
Claim: Human embryonic stem-cell research involves only embryos that will be discarded by fertility clinics.
False. Human-embryo cloning is the endgame. HESC proponents are now advocating for tax funding of research of embryos created solely for the purpose of research—whether by cloning or fertilization.
Unlike iPS cells, hES cells from “surplus embryos” are not genetically identical to patients, and would be rejected by the immune system. For hESCs to be patient-specific like iPS cells, "spare embryos" from fertility clinics will not be sufficient. Instead, cloned embryos will have to be intentionally produced in the laboratory, and then destroyed to obtain stem-cell lines.
Claim: Americans support funding embryonic stem-cell research.
Americans are not aware that President Obama's executive order did not limit taxpayer funding to “spare embryos who would die anyway.” A recent poll shows that while many Americans support the use of “spare” embryos for research, intentionally producing cloned embryos only to destroy them for research is largely rejected by the public.
A March 2009 Gallup poll shows that 14% of Americans support funding of unrestricted embryo research. This means that 86% of Americans would be opposed to what the National Institutes of Health is poised to fund if they were aware that the president’s order was not restricted to “spare embryos who would die anyway.
Claim: Even if “leftover” embryos from fertility clinics would not be sufficient for treating patients, politicians should codify into law the Obama executive order allowing federal funding for the use of such embryos in research, despite the recent advance of iPSCs.
Direct reprogramming to create iPSCs provides a scientifically feasible and promising alternative to research that requires destroying human embryos. Even President Clinton’s bioethics commission concluded that embryo destruction posed a moral problem and was “justifiable” only if there were no alternatives.
“In our judgment, the derivation of stem cells from embryos remaining following infertility treatments is justifiable only if no less morally problematic alternatives are available for advancing the research. But as we have noted, stem cells from embryos appear to be different in scientifically important ways from AS cells and also appear to offer greater promise of therapeutic breakthroughs. The claim that there are alternatives to using stem cells derived from embryos is not, at the present time, supported scientifically. We recognize, however, that this is a matter that must be revisited continually as science advances.”
- National Bioethics Advisory Commission, Ethical Issues in Human Stem Cell Research (Sept. 1999), Volume I, p. 53
Claim: Embryonic stem cells are natural cells, not laboratory-produced like iPSCs, so they are better.
Just because embryonic stem cells, known as ES cells, are isolated from embryos does not mean that they are unchanged by the isolation process. Multiple studies have shown that ES cells are not identical to natural cells of the embryo; rather they are a laboratory-produced cell type, just as iPS cells are. This is precisely why ES cells can be patented as “inventions.”
Claim: We don’t really know if iPSCs and ESCs are equivalent, but ESCs are the "gold standard" to which iPS cells must be compared.
ES and iPS cells are similar, but not identical. The important feature of both iPS and ES cells is that they are functional equivalents of cells that exist naturally in embryos; i.e. when injected into embryos, both iPS cells and ES cells produce all the tissues of the adult body.
Dr. James Thomson, the first scientist ever to isolate, culture, and characterize human embryonic stem cells in 1998, and author of one of the two initial human iPSC studies, found that iPS cells “meet the defining criteria” for embryonic stem cells “with the significant exception that the iPS cells are not derived from embryos.”
Mouse iPSCs have passed the strictest possible scientific tests for being functional equivalents of mouse ESCs. Tests for human cells are more limited, but human iPSCs have met all the available criteria for being the functional equivalent of hESCs. This can be established with greater certainty through comparisons with the existing hESC lines, which have been used in the vast majority of human ESC studies throughout the world.
Claim: Scientists still need to compare iPSCs to hESCs.
Yes, but this does not require cloning or destroying human embryos to make more hESC lines. Existing cell lines are more than sufficient for this comparison.
Furthermore, the primate system permits the best in-depth platform for comparative studies. From Rhesus macaque monkeys, primate pluripotent stem cells are available from all conceivable sources: IVF embryos, naturally conceived embryos (removed from the fallopian tube after fertilization), somatic cell nuclear transfer-cloned embryos, parthenotes, and, recently, primate iPS cells as well.
Claim: We don't know whether iPSCs or hESCs will be better for research.
There are at least three significant reasons why iPSCs are better for research:
* First, patient-specific iPSCs are available “here and now,” compared to the merely theoretical prospects of stem cells from human-embryo cloning. Direct reprogramming is the ONLY way to derive pluripotent cells from specific adult patients (i.e. patient-specific stem cells) for research on human genetic diseases at this time. In the last year, multiple disease-specific human iPS cell lines have already been produced.
* Second, direct reprogramming makes multiple iPSC lines from an individual patient’s skin cells without any additional cost or effort—an enormous scientific advantage. Obtaining iPSCs does not require access to a fertility clinic, simplifying the requirements for research, and these cells are easier to produce than hESCs, so more scientists will work with them and research will advance much more quickly. In the last year, over 800 new laboratories have begun conducting research on iPS cells.
* Third, because iPSCs do not involve human embryos or human eggs, they will be subject to significantly simpler regulatory requirements. IPSCs are fully eligible now for funding by the NIH, and in fact the Wisconsin iPSC study was partly funded by the NIH.
Claim: We don't know whether iPSCs or hESCs will be better for therapies.
Currently, clinical trials for either hESCs or iPSCs are problematic because of concerns regarding safety (cancer risk) and efficacy (ability to differentiate into useful cell types). However, if these obstacles can be overcome, there are at least two significant reasons why iPSCs will be better for therapies:
* IPSCs are patient-specific, a huge advantage for therapeutic use, compared to hESCs “left over” from fertility clinics that are not patient-specific and would require immune suppression.
* IPSCs do not use human eggs, making it possible to develop therapies without imposing significant medical risks on women (who must be given hormones to produce numerous eggs per cycle for egg donation).
Claim: IPSCs can make tumors and convert to cancer cells.
Multiple scientific studies show that all pluripotent cells, including hESCs, form tumors (teratomas) and can convert to cancer cells. The risk of tumor formation from iPS cells was initially greater than for embryo-derived stem cells because the genes used for reprogramming remained inserted in the cell. However, over the last year, the iPS technique has been significantly improved. Current approaches have eliminated any added risk of tumor formation, and iPS cells are now no more likely to produce tumors or cause cancer than are hESCs.
The risk of tumor formation that is NOT due to the reprogramming procedure but common to all pluripotent stem cells can theoretically be addressed by converting pluripotent stem cells into mature cells that do not form tumors and can be transplanted safely to patients. It is important to understand that the efficient conversion of pluripotent stem cells to transplantable cells useful in the clinic is not yet possible for any human cell type, although much progress has been made. Thus, no immediate therapies should be expected from human pluripotent stem cells, either embryo-derived or iPSC.
Claim: Embryos are just a ball of cells, but patients are human beings who are suffering.
All human beings began life as a one-cell embryo. The argument that small size and immaturity are sufficient reasons to destroy one human individual, in the hope of benefiting someone of larger size or greater maturity is clearly an unethical line of reasoning. The critical question is whether human embryos at early stages are mere collections of human cells or developing human beings. And this question has been thoroughly addressed by the scientific evidence: Embryos are developing human beings, not tumors or disorganized collections of human cells. They are small and immature, as all human beings once were, but they are human individuals. As Dr. Leon Kass, former chairman of the President's Council on Bioethics, has stated in the Washington Post:
"The moral issue does not disappear just because the embryos are very small or because they are no longer wanted for reproductive purposes: Because they are living human embryos, destroying them is not a morally neutral act. Just as no society can afford to be callous to the needs of suffering humanity, none can afford to be cavalier about how it treats nascent human life."
Claim: Science should not be restricted by ‘religious’ objections.
Religious objections are those that appeal to specific religious traditions, invoking religious authorities or teachings, such as those found in the Quran, the Torah, or the Bible. An objection to eating during daylight hours in the month of Ramadan, to eating pork at any time, or to eating meat on Fridays during the season of Lent would be examples of “religious” objections stemming from the Islamic, Jewish, and Catholic traditions, respectively. Such objections should indeed be confined to members of the religion itself.
In contrast, objections to embryo-destructive research are not religious; they are ethical and moral objections. They are based on religiously neutral reasoning that takes into consideration both the scientific evidence indicating human embryos are human individuals and the current U.S. law that prohibits harming human beings (including prenatal human beings) in scientific experiments. The protection of human beings who participate in scientific research is an important ethical consideration. The Nazi experiments on Jews, the Tuskegee syphilis experiments on black men, and the Japanese hypothermia experiments on prisoners of war were unethical, and were not justified simply because they led to new and exciting discoveries that benefited patients. Science, like all human endeavors, must operate within an ethical framework. This is not a religious objection, it is just common sense.