Implanted stem cells grew into a range of beneficial brain-cell types and greatly extended the lives of mice missing an important enzyme, researchers report. Furthermore, stem cells from mouse brains, from human-fetal brains, and from human embryos proved equally adept at battling the mouse version of Sandhoff disease. In people, that congenital enzyme deficiency is similar to Tay-Sachs disease and causes severe mental retardation and early death.
Evan Y. Snyder, who led the work at the Burnham Institute for Medical Research in La Jolla, Calif., says that the implanted cells knew exactly how to repair the brain: "Even the dumbest stem cell is smarter than the smartest neurobiologist."
The stem cells created all the maj