Researchers from Memorial Sloan-Kettering Cancer Center and the Rockefeller University have taken an important step toward developing new treatments for Parkinson's disease and a host of other ailments, using techniques from cloning to create embryonic stem cells in the lab. These cells have the remarkable ability to grow into any replacement body part, be it bone, skin, blood or brain. Thus, by cloning a patient's own stem cells and growing them into needed tissues, scientists hope to avoid the common problem of transplant rejection. "This was the very first step in showing this kind of therapy might work," says Sloan-Kettering scientist Lorenz Studer, senior author on a paper that appeared in Science on Friday.

The researchers took cells from the tail of one mouse and transferred the nuclei from those cells into another mouse's oocytes, which had been emptied of their own nuclei. This kind of nuclear transfer is the first step in cloning an entirely new animal. After a few days of development, however, the researchers removed the embryonic stem cells and then coaxed them into becoming brain cells that make the neurotransmitter dopamine. It is this type of neuron that patients with Parkinson's disease slowly lose.

"These are a very specialized cell type," Studer explains. "Even within the fully developed brain, only about 1 in 100,000 cells are midbrain dopamine neurons, so it's quite a feat to be able to generate them." Scientists had previously created dopamine neurons only from hard-to-access fetal brain stem cells. With a grant from the Michael J. Fox Foundation, Studer now plans to take the experiment further: he will clone embryonic stem cells from mice with Parkinson's, generate genetically matched dopamine neurons and then transplant those cells back into the mice, hoping it will treat the disease.