It has been a few years since cloning controversies dominated the news, but that may change now that scientists at Oregon Health & Science University claim to have overcome previous barriers, creating human embryonic stem cells (hESC) using the technique that leads to reproductive cloning.
In somatic cell nuclear transfer (SCNT), a donor cell is transferred to an egg cell whose nucleus has been removed, creating a human embryo. "Our finding offers new ways of generating stem cells for patients with dysfunctional or damaged tissues and organs," developmental and stem cell biologist Shoukhrat Mitalipov is quoted as saying in a press release that accompanied publication of the paper today in the journal Cell. "Such stem cells can regenerate and replace those damaged cells and tissues and alleviate diseases that affect millions of people," Mitalipov said.
Other researchers have used SCNT to generate only mouse and monkey embryonic stem cells, the press release said, but "those attempts failed to produce human SCNT embryos that could progress beyond the 8-cell stage, falling far short of the 150-cell blastocyst stage that could provide hESCs for clinical purposes."
Mitalipov and his team "transferred nuclei from human skin cells into the cytoplasm of human egg cells, generating blastocysts that gave rise to hESC colonies. The resulting hESCs resembled those derived from fertilized embryos, had no chromosomal abnormalities, showed normal gene activity, and were capable of turning into more specialized cell types that could be used for replacing damaged tissues."
Four hESC lines were derived from five eight-day-old blastocysts that were produced from one donor, the peer-reviewed paper (Tachibana et al., "Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer," Cell ) said. "It was thought that, to make human SCNT work, many thousands of human eggs would be needed," Mitalipov is quoted as saying in the press release. "We were able to produce one ESC line using just two human eggs, which would make this approach practical for widespread therapeutic use."
In an email interview with Christianity Today, Mitalipov said his research avoids much of the ethical debates over human cloning.
"We were focused on using egg cytoplasm to reprogram patient cells into pluripotent stem cells but not on reproductive cloning," he said. "I believe the technique does not create embryos. ... I believe we should help patients suffering from incurable and horrible diseases."
Mitalipov also said that the research may reduce concerns over egg donor exploitation. "We showed that eggs from some donors provide better reprogramming efficacy," he said.
"We believe that the quality of eggs can be improved by proper stimulations. This will significantly reduce the number of eggs needed to make stem cells.
William Hurlbut, a consulting professor and physician at Stanford University and former member of George W. Bush's Presidential Council on Bioethics, said Mitalipov's work is important because "it opens a doorway to a vast realm of research that is at once scientifically important and ethically controversial."
"Most immediately, it will allow the creation of hESC lines that are genetically tailored to an individual patient and provide cell cultures that model specific disease processes," Hurlbut said. "Later, it could lead to many other uses of cloned embryos for projects studying human development and, eventually, set the stage for creation and implantation of cloned embryos for reproductive purposes."
"Any reasonable person would have serious concerns about where this approach will lead us. We need to find morally acceptable ways forward that do not involve the direct creation and destruction of human embryos," Hurlbut said.
Hurlbut is collaborating with Mitalipov on Altered Nuclear Transfer, a technique that uses some of the same technology, but that Hurlbut says does not involve the creation of a human embryo. "I believe we need to have both a theoretical basis and empirical evidence that what we are doing does not create an embryo, not just evidence that it can't implant and keep growing," he said.
"The reasons why primate-cloned embryos won't implant are probably just technical barriers. Science is clever at figuring out what goes wrong and fixing it," said Hurlbut. He believes Mitalipov's paper will "mark the beginning of a whole new chapter of moral scientific controversy."
"I think it's extremely important that we proceed with moral consensus and social solidarity in our federal funding of biomedical research," Hurlbut said. His own conviction is that human embryos should never be created for use as raw materials in projects of biomedical science. "From fertilization onwards, regardless of how you're getting the embryo, we should regard all stages of human development as being those of a living human organism and therefore morally inviolable being."
Asked what advantage SCNT derived hESCs have over induced pluripotent (adult) stem cells, Hurlbut said, "That remains to be seen. What will happen following this paper is a careful analysis of how these cells compare with induced pluripotent stem cells and whether there are specific advantages to using SCNT."
In 2002, the President's Council on Bioethics issued a report on cloning that included a section on deriving hESCs for research through SCNT.
"The act of cloning embryos may be undertaken with healing motives. But it is not itself an act of healing or therapy. The beneficiaries of any such acts of cloning are, at the moment, hypothetical and in the future. And if medical treatments do eventually result, the embryonic clone from which the treatment was derived will not itself be the beneficiary of any therapy. On the contrary, this sort of cloning actually takes apart (or destroys) the embryonic being that results from the act of cloning," the report said.
The council recommended using the phrase "cloning-for-biomedical-research" rather than the vague and less politically charged description "somatic cell nuclear transfer."
"Although as a scientific matter 'somatic cell nuclear transfer' or 'nuclear transplantation' may accurately describe the technique that is used to produce the embryonic clone, these terms fail to convey the nature of the deed itself, and they hide its human significance," the report said. "The recipient of the transferred nucleus is an (enucleated) egg cell (rather than another kind of cell), which then can be made to initiate cell division as if it were just like a zygote produced by fertilization," the report said.
David Stevens, M.D., CEO of the Christian Medical and Dental Association, said his organization remains opposed to such research.
"Mitalipov's unvalidated claim to have solved some of the technical barriers in cloning humans to sacrifice on the altar of science for their valuable biological parts should not distract us from the facts that his technology is unnecessary and unethical," he said. "The outrageous promises of embryonic stem cells curing a myriad of disease have been unfulfilled for 15 years while adult and other forms of stem cells are already providing real cures for real people. History reveals the tragedies of immoral human experimentation. Building a culture of life begins with protecting the most vulnerable of human beings."
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