CAMBRIDGE, Mass. — Recent claims to be able to develop embryonic stem cells for medicine without destroying human embryos have been greeted with cautious optimism.

One of the reasons scientists came up with two new procedures to obtain stem cells was to overcome the ethical objections to killing an early embryo. But most pro-life and Catholic scientists and ethicists said the procedures, unveiled in the scientific journal Nature Oct. 17, do not pass ethical muster.

Modern biology texts state that, from conception on, the human embryo is a living human being with unique DNA (distinct from that of the mother's egg and the father's sperm), and is a boy or girl with normal life expectancy.

None of these scientifically verifiable facts is a religious belief. But the Catechism of the Catholic Church teaches: “From the first moment of his existence, a human being must be recognized as having the rights of a person — among which is the inviolable right of every innocent being to life” (No. 2270).

A spokesman for the U.S. Conference of Catholic Bishops and a statement by the Christian Medical Association also said the studies, done with mice, failed to protect unborn life.

In both cases, the stem-cell scientists who conducted the experiments said pro-life ethical concerns and federal funding restrictions imposed by President Bush at least partly motivated the studies. Neither group is opposed to embryonic stem-cell research.

“I personally don't have any problem with nuclear transfer [cloning]. I realize other people do, so if we can help to resolve the problem, I think it is worthwhile,” said Rudolph Jaenisch, the Massachusetts Institute of Technology scientist whose study elicited the most interest from pro-life scientists and ethicists.

But the news held out hope for scientists like Dr. Markus Grompe, who said, “The fact that people are even doing this — they are implicitly admitting that there is a problem with the ethics, and they are working on finding a way to make it more palatable, and I think that's great.”

Said Grompe, a Catholic and a stem-cell scientist at Oregon Health and Science University, “If enough people put their heads on it and work on it, it will get solved.”

Embryonic stem cells theoretically can develop into any tissue in the body, and many scientists believe they have great potential for a range of therapies, but Catholic teaching opposes destroying human embryos to obtain the cells.

The Congregation for the Doctrine of the Faith stated in the 1987 instruction Donum Vitae, “Medical research must refrain from operations on live embryos, unless there is a moral certainty of not causing harm to the life or integrity of the unborn child and the mother, and on condition that the parents have given their free and informed consent to the procedure. It follows that all research, even when limited to the simple observation of the embryo, would become illicit were it to involve risk to the embryo's physical integrity or life by reason of the methods used or the effects induced” (No. 4).

The Dickey Amendment and Bush administration policy allows federal money for embryonic stem-cell research only if it uses a limited number of embryonic stem-cell lines derived from embryos killed prior to Aug. 9, 2001. Though there are virtually no restrictions on privately funded experimentation, many scientists and patient advocacy groups complain that the Bush policy leaves medicine with too few cells for experiments.

Jaenisch and Alexander Meissner, also of MIT, successfully created “fully competent” mouse embryonic stem cells using a controversial theory called altered nuclear transfer. This theory, developed by Stanford professor Dr. William Hurlbut and purported to overcome the ethical dilemma of destroying human embryos, was recommended for animal testing by the President's Council on Bioethics in a white paper published in May.

The Jaenisch/Meissner study was the first time the altered nuclear transfer theory had been tested.

In that process, the idea is to alter the development of the entity created during the cloning process so a “non-embryonic entity” is created, thus making it ethical to crunch it up for its stem cells. Critics say altered nuclear transfer tampers with the beginning of life and creates a disabled embryo, but an embryo nonetheless — a conclusion disputed by Hurlbut and by Jaenisch.

However, earlier criticism of this technique prompted the development of a modified version of altered nuclear transfer, oocyte assisted reprogramming, also supported by Hurlbut. Animal testing of the oocyte assisted reprogramming theory was advocated in a June 20 Wall Street Journal op-ed piece by Grompe and Princeton professor Robert George, as well as in a paper signed by 35 scientists and bioethicists, including Archbishop John Myers of Newark, N.J. The theory of oocyte assisted reprogramming is that it is possible to program the cell and egg to skip directly to the pluripotent stage and avoid creating any embryo-like entity.

Still, Christian Medical Association Executive Director Dr. David Stevens believes the “entity” is an embryo. “Just because scientists have created a genetic time bomb in the embryo does not change its essential human nature,” he said.

Advanced Cell Technology led the second study reported in Nature Oct. 17, using the pre-implantation diagnosis technique employed to check in-vitro-created embryos for genetic defects. In the study, a cell was removed from an eight-cell embryo and replicated to create an embryonic stem-cell line, apparently without harming the baby mouse born later.

Advanced Cell Technology focuses on embryonic stem-cell and cloning research, and states on its website it owns more than 300 patents or patent applications related to stem-cell therapy.

The President's Council on Bioethics had recommended against even animal testing on the Advanced Cell Technology work of doing a biopsy on an embryo to withdraw a cell to culture. Catholic teaching opposes both artificial reproduction and endangering the baby's health.

David Prentice, scientific adviser to the Family Research Council as well as to Sen. Sam Brownback, R-Kansas, said both studies had problems.

“I find it encouraging that at least some scientists recognize that there are ethical concerns about embryo destruction,” Prentice said. “But neither of these two techniques gets around the ethical problems.”

In contrast, there are now scores of successful adult stem-cell therapies, including many using umbilical-cord blood, he said.

Jaenisch said he was pleasantly surprised at how easy it was to apply the altered nuclear transfer theory in a research setting with mice. Jaenisch said no embryo is created because the silencing of the cdx2 gene in the skin cell, before it is introduced to the enucleated egg, means “it cannot organize itself.”

Father Tadeusz Pacholczyk, director of education at the National Catholic Bioethics Center in Philadelphia and a biologist, disagreed.

“Not many commentators would agree that the cdx2 gene knockdown experiment carried out in Jaenisch's lab produced a non-embryo,” he said. “In fact the authors of the paper themselves refer to it as a ‘cdx2 deficient embryo’ in the final paragraph of the paper. So, a deficient embryo, but an embryo nonetheless.”

Father Pacholczyk was one of the 35 signers supporting animal testing of oocyte assisted reprogramming. He is optimistic that there is great potential within the realm of science “if we are willing to acknowledge and confront the grave moral issues swirling around this research with some creativity and elbow grease.”

Legionary Father Thomas Berg, executive director of The Westchester Institute, a bioethics think tank in Thornwood, N.Y., found the studies to be a step in the right direction.

“Scientific interest in embryos and their stem cells is here to stay,” he said. “We need to work toward ethically sound solutions that can minimize and assuage that interest as much as possible.”

Valerie Schmalz is based in San Francisco.