New stem cell methods seek to break ethical impasse

Two papers published Oct. 16 in Nature's online edition proposed new methods of extracting stem cells from mouse embryos without destroying the embryos, an attempt to address the ethical concerns of those who believe the established method of deriving stem cells destroys human life.

"The most basic objection to embryonic stem cell research is the fact that embryos are deprived of any further potential to develop into a complete human being," Robert Lanza, MD, medical director for Advanced Cell Technology, Worcester, Mass., and a senior author of one of the Nature studies, said in a statement. "We have shown in a mouse model that you can generate embryonic stem cells using a method that does not interfere with the developmental potential of the embryo."

While critics of human embryonic stem cell research said they're open to new methods, neither of the proposed workarounds met their approval.

Gene Rudd, MD, associate executive director for the Christian Medical and Dental Assns., said that embryonic stem cell research was acceptable in animals but that the new techniques were still ethically problematic.

"Both of these strategies fell short," Dr. Rudd said. "Is it ethical to create a human embryo that has lethal defect? Is it fair to extract one cell from an eight-cell human embryo knowing that the one cell that is removed is totipotential, not pluripotential, and maybe should be deemed to have the same moral status as a fertilized ovum?"

Meanwhile, the White House was mum on whether the new techniques would prove acceptable to President Bush, who in 2001 limited federal funding of human embryonic stem cell research to a small group of existing stem cell lines.

The reaction stems from news that Dr. Lanza and colleagues from the University of Wisconsin-Madison and Wake Forest University in Winston-Salem, N.C., were able to extract an embryonic stem cell from a single blastomere removed at the eight-cell stage before the blastocyst has formed. The scientists then used that stem cell from the mouse embryo to create a colony of other stem cells.

The technique is commonly used by fertility clinics to perform a preimplantation genetic diagnosis of human embryos before in vitro fertilization. In mice, the process produced the much-prized pluripotent stem cells that could potentially develop into any form of cell or tissue, while leaving the early embryo relatively intact for potential implantation in the uterus.

The second new technique is known as altered nuclear transfer and was first proposed as a way around the human embryonic stem cell morass by William B. Hurlbut, MD, a member of the President's Council on Bioethics.

Scientists at the Massachusetts Institute of Technology successfully generated a mouse embryo that could be harvested for its stem cells but could not develop further once implanted. They did this by suppressing the expression of a gene called Cdx2, which is responsible for placental development. Dr. Hurlbut has argued that the resulting embryo has the same moral status as a teratoma, and hailed the MIT experiments as a step forward.

But both research teams cautioned that while the methods seemed promising, they were untested in human embryos.

Supporters of human embryonic stem cell research using the established method known as somatic cell nuclear transfer criticized the scientists for pursuing research in an attempt to pacify critics.

"The principle behind this will fail," said David Magnus, PhD, director of the Stanford University Center for Biomedical Ethics. "I have no problem with anybody doing any kinds of experiments they want because they find them interesting, but we shouldn't be pursuing some kind of illusory ethical fool's gold."

The U.S. Conference of Catholic Bishops and the Vatican, for example, have said that any manipulation of embryos for the benefit of others is morally wrong whether the embryo is destroyed or not.

But Dr. Rudd said he wouldn't go that far. "I do believe that groups like ourselves who hold some values but will also make an effort to promote the science can be pacified," he said.

AMA policy supports federal funding for human embryonic stem cell research.