Editing Somatic cell nuclear transfer (section)

==Controversy==
{{Further|Stem cell controversy}}

[[File:Human blastocyst.jpg|right|thumb|250px|Human [[blastocyst]], showing the [[inner cell mass]] (top, right)]]
Nuclear transfer techniques present a different set of ethical considerations than those associated with the use of other stem cells like embryonic stem cells which are [[Stem cell controversy|controversial]] for their requirement to destroy an embryo. These different considerations have led to some individuals and organizations who are ''not'' opposed to human embryonic stem cell research to be concerned about, or opposed to, SCNT research.<ref name="rifkin">[[Jeremy Rifkin]]. (February 18, 2002). [http://www.thenation.com/doc/20020218/rifkin "Fusion Biopolitics".] {{Webarchive|url=https://web.archive.org/web/20090616061931/http://www.thenation.com/doc/20020218/rifkin |date=2009-06-16 }} ''The Nation''. Retrieved on August 7, 2006.</ref><ref name="Stolberg">Sheryl Gay Stolberg, "[https://query.nytimes.com/gst/fullpage.html?res=9C0DE7DA1E3BF937A15752C0A9649C8B63&sec=&spon=&pagewanted=all Some for Abortion Rights Lean Right in Cloning Fight]", ''New York Times'' (January 24, 2002)</ref><ref>Lori B. Andrews, et al., [http://geneticsandsociety.org/article.php?id=1958 Open Letter to US Senate on Human Cloning] {{webarchive|url=https://web.archive.org/web/20101122105524/http://geneticsandsociety.org/article.php?id=1958 |date=2010-11-22}}, (March 19, 2002)</ref>

One concern is that blastula creation in SCNT-based human stem cell research will lead to the reproductive cloning of humans. Both processes use the same first step: the creation of a nuclear transferred embryo, most likely via SCNT. Those who hold this concern often advocate for strong regulation of SCNT to preclude implantation of any derived products for the intention of human reproduction,<ref name="Regulation">Lori B. Andrews et al. (March 19, 2002).[http://genetics-and-society.org/resources/cgs/2002_open_letter.html "Open Letter to US Senators on Human Cloning and Eugenic Engineering".] {{webarchive|url=https://web.archive.org/web/20060930074200/http://www.genetics-and-society.org/resources/cgs/2002_open_letter.html |date=2006-09-30}} Retrieved on August 7, 2006</ref> or its prohibition.<ref name="rifkin"/>

A second important concern is the appropriate source of the eggs that are needed. SCNT requires human [[ovum|egg cells]], which can only be obtained from women. The most common source of these eggs today are eggs that are produced and in excess of the clinical need during IVF treatment. This is a minimally invasive procedure, but it does carry some health risks, such as [[ovarian hyperstimulation syndrome]].

One vision for successful stem cell therapies is to create custom stem cell lines for patients. Each custom stem cell line would consist of a collection of identical stem cells each carrying the patient's own DNA, thus reducing or eliminating any problems with rejection when the stem cells were transplanted for treatment. For example, to treat a man with Parkinson's disease, a cell nucleus from one of his cells would be transplanted by SCNT into an egg cell from an egg donor, creating a unique lineage of stem cells almost identical to the patient's own cells. (There would be differences. For example, the mitochondrial DNA would be the same as that of the egg donor. In comparison, his own cells would carry the mitochondrial DNA of his mother.)

Potentially millions of patients could benefit from stem cell therapy, and each patient would require a large number of donated eggs in order to successfully create a single custom therapeutic stem cell line. Such large numbers of donated eggs would exceed the number of eggs currently left over and available from couples trying to have children through [[assisted reproductive technology]]. Therefore, healthy young women would need to be induced to sell eggs to be used in the creation of custom stem cell lines that could then be purchased by the medical industry and sold to patients. It is so far unclear where all these eggs would come from.

Stem cell experts consider it unlikely that such large numbers of human egg donations would occur in a developed country because of the unknown long-term public health effects of treating large numbers of healthy young women with heavy doses of hormones in order to induce hyper-ovulation (ovulating several eggs at once). Although such treatments have been performed for several decades now, the long-term effects have not been studied or declared safe to use on a large scale on otherwise healthy women. Longer-term treatments with much lower doses of hormones are known to increase the rate of cancer decades later. Whether hormone treatments to induce hyper-ovulation could have similar effects is unknown. There are also ethical questions surrounding paying for eggs. In general, marketing body parts is considered unethical and is banned in most countries.{{why|date=March 2024}} Human eggs have been a notable exception to this rule for some time.

To address the problem of creating a human egg market, some stem cell researchers are investigating the possibility of creating artificial eggs. If successful, human egg donations would not be needed to create custom stem cell lines. However, this technology may be a long way off.