Stem cells from adult bone marrow normally generate bone, muscle, cartilage and fat cellsa limited set compared with embryonic stem cells, which can spawn the full spectrum of adult tissues. Prior research with cultured tissue had shown that a mix of chemicals could change bone marrow stem cells from mice to those resembling brain cells, but when a team led by neurologist Lorraine Iacovitti of Thomas Jefferson University in Philadelphia tried the same brew on human cells, the number altered was modest. After experimenting with several different cocktails, the researchers hit on a mix that transformed 100 percent of cultured stem cells into those that looked like neurons in under an hour. "It's really the most dramatic thing we've ever witnessed in the lab," Iacovitti says.
She doesn't know yet whether they will act like neurons, but the changed cells seem to produce the neurotransmitter known as GABA. Cells that make GABA deteriorate in Huntington's disease, Iacovitti notes. She hopes to find dopamine-producing neurons to replace those lost in Parkinson's disease. Generating neurons from adult stem cells "would be a huge leap forward and put to rest a lot of the ethical issues we've been grappling with for years," she explains. People are also less likely to reject transplanted cells from their own bodies. Iacovitti says she has to tackle the problem of keeping the cells differentiated before she can do anything else, however. "We're a long way off from thinking about the clinic. But the fact that we can get it to happen is still extremely hopeful."