Reprogrammed body cells continue to show promise as a treatment for disease. Last year, scientists used the cells, called induced pluripotent stem (iPS) cells, to successfully treat sickle cell disease in mice (ScienceNOW, 6 December 2007). Now, investigators have shown that neurons derived from iPS cells alleviate a Parkinson's-like movement disorder in rats.
A team led by Marius Wernig, a postdoc in the lab of stem cell researcher Rudolf Jaenisch at the Massachusetts Institute of Technology in Cambridge generated iPS cells from mouse tail cells by adding four genes. The researchers then differentiated the cells into neural progenitor cells using the same techniques that guide the differentiation of embryonic stem cells. When the cells were injected into the brains of fetal mice, they developed into several types of brain cells and formed connections in a half-dozen brain regions.
To see whether the iPS cells could be grown into dopamine-producing neurons that could be used to treat disease, the researchers gave adult rats a Parkinson's-like movement disorder. They did this by injecting a substance that killed dopamine neurons on one side of the brain, causing the rats to move in circles. Batches of dopamine neurons grown from the mouse iPS cells were then injected into the brain area--the striatum--most stricken by Parkinson's in five rats. Within 8 weeks, four of the five treated rats showed significant recovery of function and stopped going in circles, the researchers report online today in Proceedings of the National Academy of Sciences.
A number of issues need to be resolved before the approach can be tried in humans. For example, scientists still don't know if the transplanted neurons need to form electrical connections in the host's brain or if it's enough for them just to be churning out dopamine, says Jaenisch. And serious safety issues--such as the risk of tumor formation from incompletely-differentiated nerve cells--have to be resolved. Nonetheless, Ted Dawson, head of the Parkinson's Disease Center at Johns Hopkins University in Baltimore, Maryland, says if such problems are ironed out, iPS cells "could revolutionize the way we treat" Parkinson's.
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