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Experiments on Mice Embryos May Answer Objections to Stem Cell Research

Posted on: Monday, 17 October 2005, 12:00 CDT

By Malcolm Ritter THE ASSOCIATED PRESS

NEW YORK -- Two new mouse experiments may show how to obtain human embryonic stem cells without ethical hurdles, a step that could allow federal funding for such research, scientists reported Sunday.

Currently, scientists must sacrifice human embryos to harvest such cells, which can form any tissue type and are seen as valuable for studying and treating illnesses like diabetes and Parkinson's disease.

Objections to the embryo destruction have led to a ban on federal funding for such work, which scientists say hampers research.

The new methods, detailed Sunday in the online edition of the journal Nature, seek to obtain the cells without destroying embryos.

The Coalition for the Advancement of Medical Research cautioned that despite the goal of avoiding ethical quandaries, the new approaches "will not sit well with many who oppose embryonic stem cell research."

An official with the U.S. Conference of Catholic Bishops said the two reported techniques still raise ethical objections, although a spokesman for a group of Roman Catholic bioethicists called one of them a step in the right direction.

In the standard method of harvesting stem cells, researchers wait five days or so after fertilization until the embryo has become a ball of up to 150 cells. They obtain stem cells from the interior of the ball, which destroys the embryo.

One of the new mouse studies borrowed a lab technique used in fertility clinics, called pre-implantation genetic diagnosis or PGD. It is used to screen embryos for genetic disorders.

In the study, researchers plucked a single cell from eight-cell mouse embryos, which were about two days old. While fertility clinics use such a cell for genetic testing, the researchers cultured the plucked cells and found they behaved like embryonic stem cells. The embryos, meanwhile, went on to produce mice.

The result suggests that when clinics do PGD, they could let the cell they remove divide into two, and use one resulting cell for genetic testing and the other to establish a stem cell line, said Robert Lanza of Advanced Cell Technology in Worcester, Mass., an author of the study.

But Richard Doerflinger, deputy director of pro-life activities for the Catholic bishops conference, said PGD itself is unethical. It poses a risk of harm and is mostly an effort "to select out genetically imperfect embryos," he said.

The second mouse study used a modified form of therapeutic cloning, a technique that aims to generate stem cells that genetically match a patient, for either treatment or research.

Results were reported by Dr. Rudolf Jaenisch and Alexander Meissner of the Whitehead Institute for Biomedical Research and the Massachusetts Institute of Technology.

As with normal therapeutic cloning, they took eggs whose DNA- containing nuclei had been removed and inserted in each one a nucleus from a body cell of a mouse. But before the insertion, they blocked the action of a key gene in the nuclei, to ensure the eggs could not produce an embryo that can implant in a uterus. Yet, the eggs divided and grew enough to yield stem cells.

This modified technique, called altered nuclear transfer, has been championed by Dr. William Hurlbut of Stanford University, a member of the President's Council on Bioethics. He said the abstract cluster of cells the egg produces is not an embryo but a "non- embryonic entity" that lacks an embryo's developmental potential.

"You don't create a living being," he said.

Doerflinger disagreed, saying the technique appears to create and then destroy an embryo, which would make it unethical.

But the Rev. Tad Pacholczyk, director of education for the National Catholic Bioethics Center in Philadelphia, called the approach a step in the right direction. Scientists are already discussing a modified version in which adding the nucleus to the egg would result in a single stem cell, not an embryo, he said.

Source: Daily Breeze

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