Why haven stem cell transplants worked so far?
There are many reasons scientists have encountered obstacles in engineering successful stem cell treatments for Parkinson’s. “The comparison I always use is, imagine trying to wire your house after it was built,” says Langston. “I mean, when you build a house, all the wiring goes in very early. When the house is built, if you had to do all the wiring afterwards, that would be pretty tricky. Now imagine you’re trying to do that in a living brain with 4 billion neurons.” Some stem cells revert from the type of cells they’ve been cultivated to become — generally dopamine neurons when dealing with Parkinson’s — back into generic stem cells when they’re placed in the brain. And an adult brain seems to have ways of recognizing embryonic stem cells as not belonging. “We’re learning there’re all types of signals in the adult brain that tell these little guys to go away,” says Langston. Furthermore, a stem cell’s inherent ability to develop into any kind of cell — the property that makes the
