Scientists have been working feverishly in recent years on methods to create lines of human embryonic stem (ES) cells that do not involve the destruction of human embryos. Now, researchers in Europe report they can get new lines from "arrested" embryos--early embryos that have ceased to develop but that contain individual cells that can be induced to grow separately. They and others say that the technique should satisfy people who object to stem cell research on the grounds that it harms potential human life.
The team, headed by biologist Miodrag Stojkovic, who has labs at the Principe Felipe Research Centre in Valencia, Spain, and at a company called Sintocell in Serbia, obtained 161 embryos that had been donated for research at the University of Newcastle in the U.K. Of these, thirteen had stopped developing at 6 to 7 days after fertilization, when they were at the 16-24 cell stage, and 119 had stopped developing a few days after fertilization.
In a paper published online yesterday in Stem Cells, the researchers report that they succeeded in generating pluripotent human ES cell lines--i.e., cells that can develop into many different kinds of cells-- from one of the 13 late-arrested embryos. To ascertain that they had stopped growing permanently, the scientists waited up to 2 days after the last cell division before trying to cultivate them. They then plated the embryos on a growth medium. Five of the 13 cultures generated outgrowths. And of these, two developed cells with ES cell characteristics. One of these was cultivated into a "fully characterized" human ES cell line, proving that it could differentiate into all three germ layers both in the dish and in live mice. The earlier-arrested embryos did not produce ES cell lines.
Stojkovic's team points out that about two-thirds of in-vitro fertilization (IVF) embryos fail to reach the blastocyst stage. Now, they say, scientists will be able to use this material that would otherwise be discarded. The team makes it clear that it thinks its approach is superior to one reported last month in Nature by scientists at Advanced Cell Technology (ACT) in California--deriving an ES cell line from a single cell taken from a morula (ScienceNOW 23 August). The authors of the ACT paper were criticized for claiming their procedure could be done without harming embryos when in fact they destroyed those used in their experiment.
"I think [this research] is a clear advance," says Donald Landry, director of the Division of Experimental Therapeutics at Columbia University in New York. "The only question one could have is their explicit definitions for irreversible arrest." Landry and colleagues have long been promoting the idea of getting stem cells from dead embryos, and have been scrutinizing embryos at various stages in order to develop watertight criteria for showing "irreversible arrest" of cell division. With such standards, says Landry, he and his colleagues believe the National Institutes of Health, which does not permit harm to live embryos, would allow them to be used in federally funded research.