Reactions in the press last month were uncharacteristically subdued when Ole Isacson and colleagues announced in Proceedings of the National Academy of Sciences that embryonic mouse stem cells, implanted into the striatum of a rat model of Parkinson's disease, could turn into functional dopaminergic neurons. They found that in more than 60% of implanted rats, the stem cells not only developed a dopaminergic phenotype, but also reduced motor asymmetry and normalized corticostriatal responses, as measured by functional imaging.

All of the news stories led with a positive angle. Many, including one in USA Today (7 January 2002), quoted Isacson as saying, “if further experiments are successful, there could be human trials of the technique in about five years.” But although hopes will have been raised among patients and their families by some of the headlines, the media responsibly presented the problems as well as the promise of this potential new treatment. All of the stories focused on a problem with the study — the fact that 20% of rats that received the transplants developed teratomas.

The online BBC News site (8 January 2002) carried perhaps the most critical story, including quotes from an interview with UK researcher Roger Barker. He suggested that it might be possible to engineer stem cells with a 'suicide gene' that could be turned on if a teratoma developed. But he also said, “I don't think this will be a treatment in humans for quite some time”, which will certainly have dampened some of the raised expectations.