Biologists have demonstrated two new techniques for deriving embryonic stem cells in mice, both designed to sidestep the main objection of opponents of stem cell research: the need to destroy embryos.

In separate papers published online Monday in the journal Nature, researchers proved that two techniques previously proposed to derive embryonic stem cells without destroying an embryo can work -- at least in mice. In one paper, researchers avoided breaking up the embryo outright, while in the second, the team's goal was to avoid producing a viable embryo.

Embryonic stem cells are "pluripotent," meaning they have the ability to become any type of cell in the body. That offers potential cures to diseases such as ALS (Lou Gehrig's disease), diabetes, cancer, and Parkinson's. But isolating the cells requires the destruction of three- to five-day-old embryos. By order of President George W. Bush, federal funding for stem cell researchers is available only for projects using stem cell lines that existed before August 2001.

Scientists say the restriction has slowed research, and have long been hunting for ways to increase funding, such as state-level initiatives and rules changes that would fund experiments on any stem cells derived from embryos left over from in-vitro fertilization procedures and earmarked for disposal.

The new techniques may offer an alternative solution to the funding problem -- but researchers and ethicists say neither approach is likely to provide a clean way out of the ethical debate over embryonic stem cell research, since each endangers embryos in its own way.

In one of the Nature papers, Robert Lanza, vice president of medical and scientific development at Advanced Cell Technology in Worcester, MA, and colleagues report the creation of embryonic stem cell lines using a technique similar to preimplantation genetic diagnosis, which is used to detect genetic abnormalities in IVF embryos before they are implanted in the mother's uterus.

In preimplantation genetic diagnosis, or PGD, doctors allow the embryos to divide until they consist of eight cells, then remove a single cell and test it for genetic abnormalities. Lanza and his colleagues did the same in mice -- but rather than testing the separated cell, they put it in a petri dish with previously derived embryonic stem cells, which provided factors that pushed it to divide and develop characteristics of stem cells.

Once enough cells had grown, they separated the two different cell types into fully competent embryonic stem cell lines. The remaining seven cells of the embryos were implanted into female mice and developed into normal mice at the same rate as undisturbed IVF embryos.

It could take years to see whether the technique works in humans; but if it does, Lanza envisions that prospective parents already electing PGD might agree to let the single cell removed for diagnosis divide overnight. Then one cell would be used for diagnosis and the other to create a stem cell line for research. "You would not change the clinical outcome or add any additional risk to that embryo in any way," says Lanza.

The eventual goal is to create the first method for deriving human embryonic stem cells that might be eligible for federal funding. "We think since this does not involve destruction of embryos, we should be able to create lines within the existing framework of laws and regulations," Lanza says.

But to some opponents of embryonic stem cell research, particularly Catholic ethicists, Lanza's method isn't much better than current techniques for deriving the cells -- and may not sidestep proscriptions against endangering embryos.

The Roman Catholic Church opposes in vitro fertilization itself and considers preimplantation genetic diagnosis a further affront to the sanctity of life. "PGD applied to humans is unethical," says Richard Doerflinger, deputy director of pro-life activities for the U.S. Conference of Catholic Bishops. "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."