Their intention was to develop alternative techniques for obtaining stem cells that would be acceptable to those, such as President George W. Bush, who oppose the research because they equate the destruction of an embryo with taking a human life -- but their efforts may have fallen short of this mark.

Already, groups opposed to embryonic-stem-cell research and some scientists are saying the techniques do not solve the ethical dilemma, but merely raise new moral and philosophical questions. Neither method is intended to replace conventional techniques.

Another consideration is the work was done in mice and thus it is not known if it will hold true in human cells. Such a determination will require research that might destroy human embryos -- the very dilemma researchers have been trying to avoid. Both studies were published online by the journal Nature.

Embryonic stem cells can give rise to every cell type in the body, and the scientific consensus is the research holds the potential to yield insights about how diseases develop and ways to regenerate damaged or diseased tissue.

In the first study, a team led by Dr. Robert Lanza of Advanced Cell Technology in Worcester, Mass., used a technique known as pre-implantation genetic diagnosis essentially to conduct a biopsy of mice embryos and pluck out one cell, while leaving the embryo intact and healthy. PGD is used routinely to screen for genetic defects at in-vitro fertilization clinics.

The researchers used the single cells to generate five embryonic stem cells that appeared genetically normal. The cells also exhibited markers that indicated they could give rise to all the cell types of the body. The biopsied embryos were normal and they developed to term.

"Many people -- including the president -- are concerned about destroying life in order to save life," Lanza told United Press International. "We have shown, for the first time, that you can generate embryonic stem cells using a method that doesn't interfere with the developmental potential of the embryo."

Other scientists and groups opposed to embryo destruction, however, found flaws with this approach.

Dr. George Daley, associate director of the stem-cell program at Children's Hospital in Boston, called both techniques "extremely, extremely exciting" during a media briefing Friday, but said of Lanza's method, "There's the biological possibility that a single cell actually has the potential to become life itself."

If this is the case, "this would not solve the ethical issue," said Daley, who himself is not opposed to embryonic-stem-cell techniques that involve the destruction of human embryos.

Lanza countered that the biopsied cells were obtained from the blastomere stage of the embryo, and they do not appear capable of developing into embryos.

"Individual human blastomeres have never been shown to have the capacity to create viable embryos in the laboratory," he said.

Richard Doerflinger, deputy director of the secretariat for pro-life activities of the U.S. Conference of Catholic Bishops, also objected to the technique.

"PGD applied to humans is unethical, because it poses a risk of death to the embryo, 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," Doerflinger told UPI.

Lanza said, however, PGD "is relatively simple and does not injure the embryo. In fact, it has been used to generate thousands of healthy babies."

He acknowledged that no one knows whether children produced from embryos exposed to PGD might develop problems 20 years or 30 years down the road, but scientists plan to explore that question.

Kathy Hudson, director of Johns Hopkins University's Genetics and Public Policy Center, said she is developing "a new effort to create a PGD database in the United States to collect the data needed to answer these and other important scientific and clinical questions about the safety and efficacy of PGD."

The second technique was developed by Rudolf Jaenish, of the Massachusetts Institute of Technology's Whitehead Institute for Biomedical Research in Cambridge, Mass., and colleagues. They generated mouse embryos with a dysfunctional gene called Cdx-2 that plays a role in attaching the embryo to the wall of the uterus. Without a functioning Cdx-2 gene, the embryos cannot implant in the uterus and develop further, so they are not considered viable.

The thinking is it would be ethically acceptable to conduct the embryo-destroying process of obtaining embryonic stem cells from such defective embryos, but the concept has yet to win over anyone on either side of the debate.

Daley said "the Cdx-2 gene is not the answer" to solving the ethical issue. The technique generates an embryo that essentially is normal in its first few days, but later will be doomed to demise when the Cdx-2 gene does not function properly, he said.

Doerflinger objected for much the same reasons.

"It is not enough to say the genetic defect preventing organismal development was introduced into the genome from the very beginning," Doerflinger said, noting that humans often develop certain diseases during their life, such as Huntington's, for which the genetic defect was present at birth.

"Creating these human lives just to destroy them is wrong," he said. "Engineering them so they will self-destruct after a certain point in development is wrong."

Patient groups were enthusiastic, but they also were concerned the two new techniques could confuse Congress or the public into thinking conventional stem-cell extraction techniques were unnecessary, or that they might influence legislation pending in the Senate that would expand stem-cell lines that qualify for federal funding.

"These studies are in fact arguments for why we need to push forward with stem-cell science," said Sean Tipton, spokesman for the Coalition for the Advancement of Medical Research, a consortium of patient groups, medical societies and universities.

"It shows this is a rapidly changing field (and) we don't have all the answers," Tipton said. "The only way we're going to get those is to let our scientists get to work."

Lanza echoed those sentiments, saying his biopsy approach is not a substitute for conventional methods of obtaining stem cells.

"We hope our approach can be perfected in humans, but a lot of people don't have time to wait for us to work this out," he said. "It would be tragic not to pursue all the options and methods available to us to get this technology to the bedside as soon as possible."

The bill pending in the Senate, called the Stem Cell Research Enhancement Act of 2005, would allow federal funding for research involving surplus embryos from fertilization clinics that otherwise would be discarded. Bush's policy limited federal funding to stem-cell lines in existence prior to Aug. 9, 2001.

The House passed the legislation last May, and Tipton said he expects there will be enough votes to pass it in the Senate. There also may be enough votes to make it veto-proof, he added. Bush has said he would veto the legislation if it passed through both chambers of Congress. If so, it would be the first bill the president vetoed in nearly five years in office.

Although stem-cell research is controversial, those opposed to it appear to be in the minority, because polls indicate most Americans support the research. A recent survey by Johns Hopkins University's Genetics and Public Policy Center found approximately 77 percent of those surveyed either approve or strongly approve of it.

Lanza said his biopsy technique could be used to generate new stem cell lines that would meet the criteria for federal funding because it "does not involve the destruction of an embryo, nor does the biopsied cell ever develop into an embryo at any point."

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