Nagy published the results of his research in an online version of the journal Nature Feb. 27.

"This new method of generating stem cells does not require embryos as starting points and could be used to generate cells from many adult tissues, such as a patient's own skin cells," Nagy said in a press release from Mount Sinai.

In 2005 Nagy created Canada's first embryonic stem cell lines from donated embryos. That research led to his discovery of the "piggyBAC" method of reprograming cells without using viruses to deliver growth factors to the cell's chromosomes. Viruses used to carry growth factors will incorporate themselves into the cells, which then often turn cancerous.

Because Nagy's technique creates "embryo-like cells," bioethicist Bridget Campion sees red flags.

"Are we in the realm of therapeutic cloning?" asked the researcher with the Canadian Catholic Bioethics Institute and consultant for the Catholic Organization for Life and Family. "Red flags go up when we say things like 'cells reverted to an embryonic state.' ”

Stem cells hold the potential to cure such diseases as Parkinson's, cystic fibrosis and others that break down entire systems in the body.

While the new technique may represent the lesser evil in that it does not use the product of sexual reproduction (whether natural or in a petrie dish) as a raw material, Campion worries about how the technique will be commercialized and whether the resulting stem cells might represent an interrupted process which otherwise could result in a human being.

"As Catholics we are filled with compassion for the suffering in the human condition, but the ends never justify the means," she said. "We don't work with that logic — that the ends justify the means. Means are extremely important."

Jesuit genetics researcher Fr. Rob Allore said there is no such thing as a scientific advance that will end debate over ethics in scientific research, but hailed Nagy's paper as "a scientific as well as a technological breakthrough."

"They are happy that this method takes us beyond the need for embryonic stem cells. The technique also begins to answer some important questions related to the genetic events involved in the induction of the stem cell state," Allore wrote in an e-mail to The Catholic Register.

Allore's own research is conducted in another lab in the same hospital as Nagy. Scientists are constantly involved in ethical debate about what they are doing and how they do it, he said.

"Even with these wonderful advances we should continue to support a wide-ranging public discussion on ethical issues associated with embryonic stem cells," said Allore.

The new technique brings closer the dream of being able to use a patient's own cells to cure disease. That makes cells derived from embryos much less attractive as a subject for further research, said Allore.

"Embryos will always be a second best source of stem cells," he said. "When stem cells are obtained from embryos you have the problem of an incomplete immunological match with the patient who is to receive the stem cells. If we can learn to induce cells to take on embryonic characteristics we should be able to obtain cells directly from the patient. After being reprogrammed they can be transplanted back into the patient where you would anticipate little or no problems with rejection."

Catholic teaching strongly endorses the positive powers of scientific research, said Campion.

"We're not luddites, OK. We're not against science. We're not against research," she said. "We're definitely not against research, but it has to be based on certain principles. Even the research community recognizes this."

Catholics should not shrink from participating in ethical debates within science, said Allore.

"The Catholic community should bring the best of our intellectual and spiritual tradition to the debate," he said.