Human embryonic stem cells offer great medical hope, because of their ability to develop into almost any kind of adult cell. But harvesting the pluripotent cells from stored embryos has raised ethical concerns, due to the necessity of destroying potential humans to derive these cells. Now new research has shown that stem cells can be cultivated from cells split off from developing embryos without impacting the embryo itself.

In previous research, Robert Lanza and his colleagues at Advanced Cell Technology had shown that single-cell biopsies done on mouse embryos--similar to those used for genetic diagnosis prior to a human embryo's implantation--might allow for the cultivation of stem cell lines without discernible impact. The team thawed 16 human embryos that had gone unused by parents pursuing in vitro fertilization. The scientists separated single cells, known as blastomeres, from the embryos and cultivated them separately.

More than half of the blastomeres continued to divide and the researchers were able to cultivate specific target cells, such as endothelial cells. The shape, growth and abilities of these cells closely matched those of stem cells derived from other techniques. Overall, in 10 separate experiments, they created 19 embryonic stem cell-like growths as well as two cell lines capable of continuous production. "We believe the success rate can be further increased by optimizing conditions at the earliest stages of blastomere outgrowth," the researchers write in the paper presenting the finding, published online by Nature today.

If confirmed, the new technique would allow researchers to create and experiment with stem cells while avoiding ethical concerns as individual blastomeres, or their multicellular derivatives, have never been shown to be capable of generating a complete organism. And numerous studies have shown that this genetic testing technique has little impact on the survival rate of embryos. In fact, the single cells used in such testing routinely today could, in the future, grow stem cells for the resulting children, and humanity.