NEW ORLEANS--Two years ago Fred H. Gage set neurologists buzzing when he, his co-workers at the Salk Institute in La Jolla, Calif., and collaborators in Sweden disproved a long-standing "fact" that the human brain cannot grow new neurons once it reaches adulthood. That buzz has recently intensified into a hum of excitement as new observations of stem cells--immature cells that can divide repeatedly and give rise to many different kinds of tissues, including neurons--have found that the cells appear to be more accessible and more malleable than scientists had dared hope. Tantalized by the prospect of growing petri dishes full of neurons from a patient's own skin or marrow, several scientists spoke dreamily to reporters at a November 2000 conference in New Orleans about their hopes that transplanted stem cells could repair the nervous wreckage left by Parkinson's disease, Alzheimer's disease, multiple sclerosis, stroke or head trauma. Major newspapers ran with the story.
A close look at the details, however, suggests that the story has run ahead of the science. The most important recent experiments have uncovered three surprising properties of stem cells that together do raise the possibility of new therapies. But the results also raise a host of difficult questions.
This article was originally published with the title Biological Alchemy.