The recent announcement that two separate research teams successfully reprogrammed human skin cells to behave like embryonic stem cells was widely hailed by Catholic leaders as being a moral milestone with great clinical promise.

"From both a practical and moral perspective, this advance represents a significant benefit over embryonic stem cell research" since it was accomplished without destroying human embryos, said Dr. Marie Hilliard, RN, director of bioethics and public policy for the National Catholic Bioethics Center in Philadelphia.

Independent research groups headed by Dr. Shinya Yamanaka of Kyoto University in Japan and Dr. James A. Thomson of the University of Wisconsin were able to generate "induced pluripotent stem" (iPS) cells, having the properties of human embryonic stem cells which can potentially become any one of the body's 220 cell types.

Scientists have long theorized that stem cell research will one day result in the growth of replacement tissues for patients who suffer from incurable diseases such as diabetes, Alzheimer's and Parkinson's. The reprogramming stem cell breakthrough was achieved by the tweaking of four genes in somatic (adult) skin cells, using a virus to reprogram them to earlier states.

"The reprogramming [technique] most clearly gives evidence what most scientists and ethicists have said from the beginning: that 'for all the best and most sound scientific, medical and ethical reasons adult stem cell research was the most promising for legitimate medical use,'" said Vincentian Father Richard Benson, academic dean and professor of moral theology at St. John's Seminary, Camarillo.

Though embryonic stem cell research has been ongoing for several years --- California voters approved a $3-billion bond measure in 2004 (Prop 71) to fund stem cell research --- to date, there hasn't been one clinical trial or therapeutic discovery using embryonic stem cells, notes Hilliard.

"All clinical benefits have come from adult stem cell therapies using adult tissue, umbilical cord blood and amniotic fluid cells. Over 70 diseases, from multiple myeloma to spinal cord injuries have been treated using adult stem cells," Hilliard said.

She pointed out proponents of stem cell research that destroys human embryos acknowledge the problem of tissue rejection that must be addressed when using stem cells from these embryos. According to Hilliard, embryonic stem cell researchers estimate that over 100,000 stem cell lines will be needed to accommodate the genetic diversity of the populations needing therapies.

To generate the huge number of stem cell lines needed, Hilliard noted, four million human embryos would have to be destroyed. Of the more than 400,000 frozen embryos in fertility clinics in the U.S., she added, only approximately 11,200 are slated for research donation. And it's anticipated that if 10,000 embryos were thawed, only 100 would be biologically fit for research.

"There have always been significant limitations to embryonic stem cell research," said Father Benson. "Apart from the major concern about killing innocent embryos, there is the need for a huge number of eggs to supply the research."

He noted that it took 250 eggs to produce the cloned sheep, "Dolly." Interestingly enough, the scientist who originally cloned Dolly, Professor Ian Wilmut, has recently announced that he is abandoning cloning research to pursue direct reprogramming since it's "easier to accept socially."

Sulpician Father Gerald Coleman, vice president of corporate ethics, Daughters of Charity Health System and lecturer in ethics at Santa Clara University, applauds efforts by scientists to address ethical issues. He pointed out Dr. Thomson had ethical concerns in 1998 about engaging in his initial embryonic stem cell research, which he felt had great potential for new treatments for incurable diseases. Thomson's ethical dilemma was assuaged by the knowledge that he was extracting stem cells from embryos slated to be destroyed by fertility clinics.

The latest research of Yamanaka and Thomson, explained Father Coleman, seeks the same therapeutic goal of embryonic stem cell research without destroying human embryos. However, he added, it is unlikely that the huge amounts of money given to embryonic research will quickly transfer to reprogramming research since it is not clear yet whether reprogrammed skin cells will act exactly the same as embryonic stem cells.

"In the history of science, it is unusual for scientists to truly want to think carefully about the ethical implications of their work before they set out to do it," said Father Coleman. "Yamanaka and Thomson seem to be very aware of the need for anticipatory ethical discussion. This fact bodes well for their teams and should be a strong lesson for other scientists and those who finance their work."

Biochemical reprogramming "will resolve most but not all the ethical concerns about pluripotent stem cell research," said Dr. James Walter, Loyola Marymount University's Bioethics Institute chair, in an e-mail Nov. 28 to The Tidings from Japan's Ryukoku University where he was delivering a paper on "Human Embryonic Stem Cell Research: A Catholic Christian Perspective."

"Surely, the moral issue of creating and then destroying embryos or using existing embryos to derive these cells is resolved. Also, the need for [human] eggs and the payment of women to sell their eggs are likewise resolved by this research. However, there is still the moral issue of safety, but hopefully the safety issue will be resolved as well by further research," said Walter.

That said, Walter warned people need to be realistic about how soon any therapeutic results, if any, may be achieved from reprogramming. "We are years away from this research having any significant impact on clinical medicine, especially if we can't resolve the safety issue connected with it" due to iPS cells' tendency to cause cancer, he explained.

In a late-breaking development revealed Nov. 30 by Dr. Yamanaka, it was announced that the cancer-causing gene c-Myc does not have to be used. According to a Dec. 1 article in the Los Angeles Times, the new method is less efficient but does produce iPS cells.

"Many safety and efficacious issues still need to be resolved," said Walter, "and we must proceed carefully so that we do not experiment on humans until we are as sure as we can be that this research will not do more harm than good to patients. More basic research is needed before clinical trials can even begin.

"However," he added, "this is a significant scientific discovery, and hope to overcome these terrible diseases may be on the horizon without all the moral issues connected to it."

For a commentary on this issue from the California Catholic Conference, see page 14.