A new study in lab rats by scientists at MIT and Harvard has shown skin cells that have been "reprogrammed" to act as stem cells can be transformed into neurons to treat neurodegeneration.
The study in the Proceedings of the National Academy of Sciences
shows that reprogrammed cells, also called induced pluripotent stem (iPS) cells, when transplanted into the brains of mice and rats transform into neurons. These neurons were seen to improve debilitating symptoms typical of Parkinson's disease in a rat model.
Pluripotency is the ability to transform into any kind of cell.† But this concept in reprogrammed cells raises some serious questions about the abilities and potential dangers of the cells.
The research team, led by Rudolph Jaenisch at the Whitehead Institute for Biomedical Research at MIT, made the skin cells of a mouse pluripotent by infecting them with a retrovirus carrying four genes. This was a previously developed method for reprogramming cells.†
The researchers showed that they could turn mouse skin cells into functioning neurons in culture. Then they transplanted these neurons into the brains of mice while they were still fetuses.
After the mice grew into early adulthood, the researchers examined the brains and identified the transplanted cells.† The programmed cells had been labeled with a fluorescent marker for identification.
The cells "migrate nicely into the brain and mature in the brain.† They adopt functions of mature neurons," said Marius Wernig, a postdoctoral fellow at the Whitehead Institute. "This is the first demonstration that re-programmed cells can integrate into the neural system or positively affect neurodegenerative disease," he added.
The next step was to see whether these functioning neurons could repair a defect in an animal model of disease. In Parkinson's disease, a specific population of neurons that produce dopamine are lost.
Rats used in the study were given a toxin that kills dopamine neurons on one side of the brain. Although the rats appear normal, when their dopamine neurons are stimulated with amphetamine, they begin to turn in circles in the direction of the damaged side.
In rats that were given transplants of neurons derived from iPS cells, the motor defect was improved.
The researchers said however that safety issues would have to be considered before the method is tested in people.
Currently they are considered unsafe for use in humans because viruses are used to carry the new genes into skin cells and transform them and this could cause cancer.
The researchers said their approach matches the so-called therapeutic cloning, which uses cloning technology to create perfectly matched cell transplants.
Parkinson's is a debilitating disease where patients lose abilities associated with movement, and progress from a type of shakiness to paralysis and death.
There is no complete cure for the disease. Transplants of cells from fetuses have offered some relief from the disease symptoms, in a few cases.
Scientists world over are working on finding ways to harness stem cells, the body's master cells.† Stem cells can be used to treat patients with serious injuries, brain diseases and organ damage caused by conditions such as diabetes.
So far stem cells taken from very early embryos are seen to be the most malleable and the most powerful. But many people object to their use on ethical grounds because the embryo must be destroyed to extract the stem cells.
Another benefit in using stem cells from skin is that if the cells came from a patient's own skin, there would be no potential complications from immune rejection of foreign tissue.