An international research team has achieved a scientific first by producing embryonic stem cells from cloned embryos, advancing the effort to generate replacement tissues for sick patients.

Embryonic stems cells are the starter cells to all others in the body, which means potentially they can grow into any type of tissue, from blood to bone to brain. For a decade-and-a-half, they have been seen as a potential source of rejection-free transplant tissues for ailments ranging from diabetes to paralysis. They were also the subject of a fierce political fight over the medical ethics of using human embryos in research during the Bush administration because the embryos had to be destroyed in the process of retrieving the embryonic cells.

"We have now refined the steps to come up with a process for generating these cells that is pretty efficient," says Shoukhrat Mitalipov of Oregon Health & Science University in Beaverton, who headed the cell cloning study released by the journal Cell. "There is no one trick to making this work. It is like winning the lottery, all the numbers have to line up the right way to win."