Human Cloning? Stem Cell Advance Reignites Ethics Debate

A new stem cell discovery has reawakened controversy about human cloning though technical challenges mean scientists are far from being able to create human babies as in Michael Bay's 2005 sci-fi flick "The Island."

Not that they would even want to.

"Nobody in their right mind would want to do that," said John Gearhart, the director of the Institute for Regenerative Medicine at the University of Pennsylvania, who was not involved in the study. And indeed, the research wasn't conducted with the idea of creating cloned mini-me's in mind. Instead, scientists attempting to treat diseases of the cell's powerhouse, the mitochondria, refined the technique, which is the same one used to create the cloned sheep Dolly in 1996. [5 Wild Stem Cell Discoveries]

But the parallels between the animal-cloning procedure and the new human one have triggered concern. The U.S. Conference of Catholic Bishops (USCCB) swiftly issued a statement condemning the research, both on the grounds that embryos were destroyed in the research process and over the concern that the full reproductive cloning of humans is on its way.

"They or others may be close to being able to develop cloned human embryos to the fetal stage and then beyond," said Richard Doerflinger, the associate director of USCCB's Secretariat of Pro-Life Activities.

Technical difficulties

Fortunately for anyone concerned about the specter of human cloning, scientists say they're nowhere close to being able to get cloned human embryos past early stages of development. The study's leader, Shoukhrat Mitalipov of Oregon Health & Science University, told reporters that the early embryos 100-cell bundles known as blastocysts seem to have defects preventing them from implanting properly in the uterus and reaching maturity.

A blastocyst consists of an inner mass of cells that will become the fetus. Surrounding this inner cell mass as a hollow ball is a layer of cells called the trophoblast. These trophoblast cells are destined to become the placenta, the organ that nourishes the growing embryo and, later, the fetus. [8 Odd Changes That Happen During Pregnancy]

But in clones, the trophoblast cells frequently fail, perhaps a domino effect from just a few genes going wrong, said Jose Cibelli, a stem cell researcher at Michigan State University. The mother's body may reject the implanting embryo. If implantation occurs, the vast majority of cloned embryos fail to make it past the first trimester of pregnancy.

For example, scientists can take a normal embryo from the uterus of one cow, transplant it into another and have a 60 percent chance of a normal calf being born. Transferring a cloned cow embryo into a cow uterus results in a healthy calf less than 10 percent of the time, Cibelli told LiveScience.

Read more:
Human Cloning? Stem Cell Advance Reignites Ethics Debate