For the first time, scientists have derived embryonic stem cells from a primate without fertilizing the female egg -- raising the possibility that human stem cells could be created without destroying viable human embryos.

This is because the monkey embryos in this case were created through a process called parthenogenesis, in which an unfertilized egg is coaxed into becoming an early embryo. Unlike the human embryos that have been used for stem cell research, embryos created in this manner cannot become a viable fetus.

The technique has been used before in primates, but until now scientists have not been able to derive stem cells lines from the resulting embryo.

Because stem cells can potentially differentiate into any type of body tissue, scientists believe they can be used to replace the diseased cells that mark conditions such as Alzheimer's disease, Parkinson's, heart disease and diabetes.

But as the stem cells used in research are usually derived from embryos, which are destroyed in the process, controversy has surrounded stem cell research. In the US, federal funds can only go toward research on existing human stem cell lines, and not work in which an embryo will be destroyed.

For those who are concerned about the ethics of destroying potentially viable embryos, parthenogenesis could be an attractive approach to obtaining stem cells.
It is possible that, in the future, advances in parthenogenesis and in getting stem cells from adult tissue could "wipe out" the debate over embryonic stem cell research.

The principle that parthenogenesis could also work in humans has already been demonstrated. Collaborators on this work from the Massachusetts-based biotech firm Advanced Cell Technology (ACT) reported last November that they had induced human eggs to develop into early embryos. No stem cells were produced.

But that part of their work was overshadowed by news that they had also cloned the first human embryo. This was achieved through a process called somatic cell nuclear transfer, in which the nucleus of an egg is replaced with that of a cell from a donor's body. When an early embryo results, it is a genetic match to the donor.

When the aim of such cloning is to produce stem cells that match the donor -- and not a cloned human being -- it is called therapeutic cloning. If stem cells are to be useful in treating disease, many experts believe that they will have to be generated through therapeutic cloning to avoid rejection. But therapeutic cloning also creates a potentially viable early embryo that must be destroyed to get the stem cells.

Parthenogenesis might offer another option in harvesting genetically matched stem cells for patients, according to the current report.

Science February 1, 2002;295:819