Embryonic stem cells are the basic cells capable of changing into any kind of cell in the human body. Until now the best place to get embryonic stem cells were from human embryos. But attempts to harvest those cells has been met with technical as well as ethical challenges, and for years scientists have been trying to find alternatives.

Now researchers have used a cloning technique, the same one used to create Dolly the sheep, to create human stem cells. The scientists from Oregon Health & Science University and the Oregon National Primate Research Center, transplanted genetic material from an adult skin cell into an unfertilized human egg cell that had its DNA removed. The hybrid cell divided and multiplied until the blastocyst stage — around 150 cells — which is large enough to provide a source of embryonic stem cells. These cells were then grown into beating heart cells. In theory, such cells could be grown into any kind of cell to repair damaged tissue, such as in a heart, or as nerve cells to treat spinal cord injuries.

By using these cloning techniques, not only are scientists creating the much-desired embryonic stage of stem cells but also side-stepping the problem of harvesting cells from a fertilized human egg, which under other circumstances could grow into a human being. And because the cells would be cloned from the patient, the person's own body wouldn't reject the new tissue.

The study was published this week in the journal Cell.

Credit: Steve Gschmeissner/Science Photo Library/Corbis