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New Stem Cell Techniques May Alter Ethics Debate

Posted on: Tuesday, 18 October 2005, 15:00 CDT

By Nicholas Wade

Scientists have devised two new techniques to derive embryonic stem cells in mice, one of which avoids the destruction of the embryo, a development that may shift the grounds of the longstanding political debate about the research. The destruction of embryos is a principal objection of anti-abortion advocates who have strenuously opposed the U.S. government financing the research. The second new technique manipulates embryos so they are inherently incapable of implanting in the uterus, a possible ethical advantage in the proposed therapy, which would convert a patient's skin cells into embryonic cells and then into new tissues to repair the body. Both methods are described on Monday in the online edition of Nature. The technique for making embryonic stem cells without compromising the embryo was developed in mice and has yet to be adapted to people, but the two species are very similar at this level of embryonic development. If it does work in people, the technique might divide anti-abortionists into those who accept or reject in vitro fertilization, because the objection to deriving human embryonic stem cells would come to rest on creating the embryos in the first place, not on their destruction. "This gets around all of the ethical arguments, except for that small minority of the pro-life community that doesn't even support in vitro fertilization," said Representative Roscoe Bartlett, Republican of Maryland, whose Web site describes him as "a pro-life legislator." Until now, the only way of deriving human embryonic stem cells has been to break open the embryo before it implants in the uterus, a stage at which it is called a blastocyst, and take out the inner cell mass, whose cells form all the tissues in a human body

. Many anti-abortionists say the destruction of any embryo is wrong. The U.S. Congress has forbidden the use of federal funds for such research, and federally supported scientists can work with only a small number of existing lines of embryonic stem cells that have been exempted by President George W. Bush. Robert Lanza and colleagues at Advanced Cell Technology, a biotechnology company in Worcester, Massachusetts, have developed an alternative way of generating embryonic stem cells that leaves the embryo viable. They let a fertilized mouse egg divide three times until it contained eight cells, a stage just before the embryo becomes a blastocyst. Removing one of these cells, they then coaxed it into growing in glassware and forming cells that have all the same essential properties as embryonic stem cells derived from the inner cell mass, Lanza's team reports. The seven-cell embryo was implanted in a mouse's uterus and grew successfully to term. This part of the procedure is known to work with humans too, because it is the basis of a well-established test known as preimplantation genetic diagnosis. In the test, one cell is removed from each of a set of embryos and tested for any of 150 genetic defects, giving the parents the choice of implanting an embryo that is disease free. Lanza's technique is likely to be welcomed by many in the middle of the debate, although it has not won over the U.S. Conference of Catholic Bishops. Richard Doerflinger, its deputy director for anti- abortion activities, dismissed the technique, saying that preimplantation genetic diagnosis itself is unethical. The technique "is done chiefly to select out genetically imperfect embryos for discarding, and poses unknown risks of future harm even to the child allowed to be born," he said in an e-mail message. The other alternative method reported in Nature on Monday addresses an ethical objection to therapeutic cloning, the idea of treating patients with new tissues generated from their own cells. The cells would be obtained by taking the nucleus from a patient's skin cell and injecting it into a human egg whose nucleus had been removed. The egg develops into a blastocyst from which embryonic stem cells can be derived in the usual way. Critics say this transfer technique creates embryos only to destroy them. To counter this objection, Alexander Meissner and Rudolf Jaenisch of the Whitehead Institute in Cambridge, Massachusetts, have created mouse nuclear transfer embryos that are inherently incapable of implanting in the uterus. They did so by switching off a gene in the donor nucleus that is needed for the implantation process. The gene was switched back on later because it is needed to form the intestinal tissues.

Source: International Herald Tribune

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