The stem cell controversy is the bioethical debate primarily concerning the creation, treatment, and destruction of human embryos incident to research involving embryonic stem cells. Not all stem cell research involves the creation, use, or destruction of human embryos. For example, adult stem cells, amniotic stem cells and induced pluripotent stem cells do not involve human embryos.

Stem cells have the ability to differentiate into almost any specialized cells, helping heal physical trauma, degenerative conditions, and genetic diseases (in combination with gene therapy). Further treatments using stem cells could potentially be developed thanks to their ability to repair extensive tissue damage.[1]

Great levels of success and potential have been shown from research using adult stem cells. In early 2009, the FDA approved the first human clinical trials using embryonic stem cells. Embryonic stem cells are pluripotent, and thus can become any other cell type excluding the placenta. Adult stem cells, however, are generally limited to differentiating into different cell types of their tissue of origin. However, some evidence suggests that adult stem cell plasticity may exist, increasing the number of cell types a given adult stem cell can become. In addition, embryonic stem cells are considered more useful for nervous system therapies, because researchers have struggled to identify and isolate neural progenitors from adult tissues. Embryonic stem cells, however, might be rejected by the immune system - a problem that wouldn't occur if the patient received his or her own stem cells.

Some stem cell researchers are working to develop techniques of isolating stem cells that are as potent as embryonic stem cells, but do not require a human embryo.

Some believe that human skin cells can be coaxed to "de-differentiate" and revert to an embryonic state. Researchers at Harvard University, led by Kevin Eggan, have attempted to transfer the nucleus of a somatic cell into an existing embryonic stem cell, thus creating a new stem cell line.[2] Another study published in August 2006 also indicates that differentiated cells can be reprogrammed to an embryonic-like state by introducing four specific factors, resulting in induced pluripotent stem cells.[3] Human skins cells reverting to their embryonic state have been accomplished at the Oregon Health & Science University and the Oregon National Primate Research Center, making this no longer a matter of belief.[4]

Researchers at Advanced Cell Technology, led by Robert Lanza, reported the successful derivation of a stem cell line using a process similar to preimplantation genetic diagnosis, in which a single blastomere is extracted from a blastocyst.[5] At the 2007 meeting of the International Society for Stem Cell Research (ISSCR),[6] Lanza announced that his team had succeeded in producing three new stem cell lines without destroying the parent embryos. "These are the first human embryonic cell lines in existence that didn't result from the destruction of an embryo." Lanza is currently in discussions with the National Institutes of Health (NIH) to determine whether the new technique sidesteps U.S. restrictions on federal funding for ES cell research.[7]

Anthony Atala of Wake Forest University says that the fluid surrounding the fetus has been found to contain stem cells that, when utilized correctly, "can be differentiated towards cell types such as fat, bone, muscle, blood vessel, nerve and liver cells". The extraction of this fluid is not thought to harm the fetus in any way. He hopes "that these cells will provide a valuable resource for tissue repair and for engineered organs as well".[8]

While stem cell research has, for years, been stymied by concerns of ethics and morals, in recent years there have been advances in obtaining and using stem cells extracted from adult subjects. By using stem cells taken from an adult, scientists have been able to treat some of the worst diseases that continue to plague our species, including various forms of cancer as well as muscular and neurological degenerative diseases. Taking these stem cells from adults does not permanently harm the patient and has none of the ethical or moral pitfalls that embryonic stem cell research has been associated with. While this new form of stem cell research is gaining in popularity, it still has a stigma attached to it solely by being stem cell research. If the public can be educated about this, a new form of medicine may be fast approaching from the horizon.

The status of the human embryo and human embryonic stem cell research is a controversial issue as, with the present state of technology, the creation of a human embryonic stem cell line requires the destruction of a human embryo. Stem cell debates have motivated and reinvigorated the pro-life movement, whose members are concerned with the rights and status of the embryo as an early-aged human life. They believe that embryonic stem cell research instrumentalizes and violates the sanctity of life, and some also view it as tantamount to murder.[9] The fundamental assertion of those who oppose embryonic stem cell research is the belief that human life is inviolable, combined with the belief that human life begins when a sperm cell fertilizes an egg cell to form a single cell.

A portion of stem cell researchers use embryos that were created but not used in in vitro fertility treatments to derive new stem cell lines. Most of these embryos are to be destroyed, or stored for long periods of time, long past their viable storage life. In the United States alone, there have been estimates of at least 400,000 such embryos.[10] See also Embryo donation.

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