Cloning Takes a Giant Step Forward
The Dubious Advance of Modern Science
| 3184 hits
By E. Christian Brugger
DENVER, Colorado, OCT. 10, 2011 (Zenit.org).- The journal Nature announced last Wednesday that scientists had for the first time successfully derived "patient specific" stem cells from a cloned human embryo. The last time such a claim was made was by the now discredited Korean researcher Hwang Woo Suk, who alleged in a 2005 paper in the journal Science that his team had procured stem cells from cloned human embryos. Subsequent investigations found that Hwang had fabricated the data.
Nature announced that a research team led by Dieter Egli and Scott Noggle from the New York Stem Cell Foundation used a variation of the cloning technology known as somatic cell nuclear transfer (SCNT) to create what appears to have been badly disabled human embryos from which stem cells were culled. In ordinary SCNT -- as used, for example, to clone "Dolly" the sheep -- a female oocyte (egg) is "enucleated" (its nucleus is removed) and the nucleus of another cell, an adult somatic cell, is transferred into it. Since most of our DNA is found in the nuclei of our cells, removing the egg's own nucleus means producing a bag of oocyte cytoplasm empty of almost all genetic material. The transferred somatic cell nucleus, containing a full 46 chromosome complement, now becomes the nucleus of the newly minted cell. The oocyte cytoplasm goes to work on the nuclear DNA reprogramming it back to the active condition of an embryo nucleus. When stimulated to divide, the dividing one-celled creation is an embryo, a cloned embryo, with the DNA not of the supplier of the egg, but of the donor somatic cell.
The New York lab team, however, did not enucleate the eggs. Rather, it transferred the somatic cell nuclei -- called "diploid" because they contain two complete sets of chromosomes -- straight into the eggs with their own nuclei intact. This resulted in cells with a "triploid" nucleus (i.e., with three rather than two copies of genetic material, the third contributed from the egg's nucleus). The triploid nuclei underwent reprogramming to the state of pluripotency. Cell division commenced and proceeded to the blastocyst stage (approximate 70–100 cells). Researchers then disaggregated the blastocysts -- destroyed them -- and harvested their stem cells.
Were the blastocysts living human embryos? Some experts have argued they were. Daniel P. Sulmasy, a professor of medicine and ethics at the University of Chicago and member of the Obama bioethics advisory commission, said confidently: "They have created human embryos. They are abnormal, but they are still human embryos." His conclusion sounds plausible to me. Up until now, SCNT performed on human cells (as opposed to sheep, dogs, etc.) has been a non-starter. Scientists have successfully cloned sheep, dogs, even monkeys. But development in humans is considerably more complicated. Cell division fizzles out after the first few steps suggesting that no living human organism -- no embryo -- ever comes into existence.
Two things are different with the recent experiment. First, the cells divided to the blastocyst stage indicating they possessed an intrinsic and ordered (human) developmental trajectory. Second, some babies, although not very many, are born alive with triploid conditions. They are badly disabled and rarely survive longer than a few weeks. But no one would dare say they are anything but human beings. So triploidy is not necessarily a deal killer when it comes to actual human development.
Three big ethical problems surround this research. The first, of course, is that it cloned human embryos for the mercenary purpose of harvesting their stem cells. Second, the embryos were profoundly disabled by the intent of the researchers who made them. And third, the research team paid female donors to super-ovulate using powerful and potentially dangerous drugs for a project with unproven benefits. The research team had to use 270 eggs from 16 different donors to secure its results.
Commentators friendly to embryo-destructive research are beginning to raise their voices again in favor of embryo cloning, destruction, and stem cell harvesting. Their brazenness was muted for a while after the November 2007 announcement that stem cells characterized by "pluripotency" (the quality coveted in Embryonic Stem Cells, ESCs) had been successfully derived from human skin cells. For at least three reasons, these "induced pluripotent stem cells" (iPSCs) generated enormous interest: first, because they do not require the destruction of human embryos, second, the cells from which they are derived are found in abundance, and third, they can be produced without the need for female oocytes.
Although research into iPSCs is still booming, in the past five years studies have highlighted several potential weaknesses with iPSCs. Consequently, scientists are beginning to clamor again for stem cells derived from human embryos, the so-called gold standard of pluripotency.
The Nature announcement is indeed significant because it suggests that cloning to produce "patient specific" stem cells may one day be successful. Stem cells are "patient specific" when they possess the identical nuclear DNA of the patient whom they would be used to treat. They are desirable because when injected into the patient's body, his or her body is more likely to "think" the cells are its own; this may minimize the serious problem of immunological rejection.
One way to create "patient specific" stem cells, at least in principle, is through SCNT: by transferring the DNA of one person (the patient) into an enucleated egg and stimulating the newly created cell -- which, if the technique is successful, is a one celled embryo, called a "zygote" -- to divide to the blastocyst stage. When the embryo is destroyed, the harvested stem cells possess the genetic code of the patient, not the egg donor.
But there should be no ambiguity at present: the New York researchers manifestly did not produce "patient specific" stem cells, since the embryos from which the cells were derived had triploid nuclei that were not "specific" to any patient.
The research also suggests that when using cloning the egg nucleus contributes something necessary to embryonic development, at least as far as the blastocyst stage. If this is the case, then the newly devised technique will assure that the cells are never useful for clinical purposes, unless a way is devised to safely and completely extract the extra copy of DNA contributed by the oocyte.
For those concerned about the exploitation of human embryos, the announcement deserves the harshest censure possible. Creating disabled human life and then destroying it in order to devise ways to assist human healing is a bad means to a good end: a radical injustice to the victimized embryos, further unraveling of our community's respect for the good of life, and degrading of the moral characters of the researchers who do such deeds.
The desire for pluripotent stem cells is only likely to increase with time. Wise and conscientious citizens will do well to advocate for research into legitimate alternative sources for deriving pluripotent stem cells.
* * *
E. Christian Brugger is a Senior Fellow of Ethics and director of the Fellows Program at the Culture of Life Foundation; and the J. Francis Cardinal Stafford Chair of Moral Theology at St. John Vianney Theological Seminary in Denver, Colorado.