WASHINGTON Skin cells re-programmed to act like embryonic stem cells eased symptoms of Parkinson's disease in rats, researchers reported on Monday in a first step toward tailored treatments for people that bypass concerns about using human embryos.
The experiment suggests it may be possible to take a small sample of skin and turn it into a transplant perfectly matched to patients with Parkinson's and other diseases, the researchers reported in the Proceedings of the National Academy of Sciences.
It also supports the usefulness of newly created cells that resemble powerful embryonic stem cells. The stem cell experts used so-called induced pluripotent stem cells, which are skin cells reprogrammed to act like embryonic stem cells.
"It's a proof of principle experiment that argues, yes, these cells may have the therapeutic promise that people ascribe to them," said Rudolf Jaenisch, a stem cell expert at the Whitehead Institute and the Massachusetts Institute of Technology.
Researchers have been trying to find ways to harness stem cells, the body's master cells, to treat patients with serious injuries, brain diseases and organ damage caused by conditions such as diabetes.
Stem cells taken from very early embryos appear to be the most malleable and the most powerful. But many people object to their use because the embryo usually must be destroyed to extract them.
Several teams have reported a way to re-program ordinary skin cells to act like embryonic stem cells by adding several genes. Jaenisch's team tested some of these cells in rats and mice. They first got such cells to take up residence in the brains of unborn mice.
REPLACING BRAIN CELLS
Then they damaged the brains of rats to resemble Parkinson's, which is caused by the destruction of certain brain cells that produce a message-carrying chemical called dopamine. Patients lose abilities associated with movement, and progress from a type of shakiness to paralysis and death.
There is no cure. Transplants of cells from fetuses have offered some relief from symptoms in a few people.
In the rats, the cell transplants improved symptoms markedly, the researchers said.
"This is the first demonstration that re-programmed cells can integrate into the neural system or positively affect neurodegenerative disease," said MIT's Marius Wernig.
One problem with transplanting these powerful but immature cells is that they can differentiate into undesired tissues.
Ole Isacson of McLean Hospital and Harvard Medical School and colleagues used green fluorescent protein to mark the cells that had become dopamine-making neurons, so that only these desired cells were transplanted into the rat brains.
"We have just started now to work on the human equivalents," Isacson said in a telephone interview.
The cells grew well, he added.
"The efficiency of our cell transplantation therapy was striking," the researchers wrote -- the transplanted cells grew well in eight of the nine rats and they all showed improved movement after treatment.
Safety issues will have to be addressed before the method is tested in people, they noted.
Viruses are used to carry the new genes into the skin cells and transform them, an approach that could cause cancer.
But the researchers said their approach is equivalent to so-called therapeutic cloning, which uses cloning technology to create perfectly matched cell transplants. Last month a team at Memorial Sloan-Kettering Institute in New York said they used the cloning approach to treat Parkinson's in mice.
(Editing by Will Dunham and Eric Beech)