An exciting new experiment began this month in the battle against Alzheimer's disease. For the first time, gene therapy has been used in a human for the treatment of a brain disease. Neurosurgeons at the University of California in San Diego (UCSD) injected 2.5 million genetically modified cells into a 60-year-old woman's brain through a small hole drilled in her skull. The procedure took 11 hours. Scientists began by harvesting skin cells from the woman. Then they inserted into these skin cells the gene that directs the production of a protein called nerve growth factor (NGF). If all goes according to plan, the inserted cells will act like tiny NGF factories, pumping out the protein.

NGF is a naturally occurring protein in normal brains. One of its jobs is to keep brain cells alive by promoting growth and survival (much like food helps us grow and thrive). NGF helps the cholinergic system function properly. This system includes nerve cells that produce the neurotransmitter acetylcholine, a chemical signal the brain needs to process information and to function normally. In the brain of an Alzheimer's patient, the cholinergic cells wither and stop making acetylcholine. Low acetylcholine levels can cause problems with memory, emotions, and language. Research has shown that NGF revives these dying cells, thus increasing the amount of acetylcholine in the brain.

In the procedure at UCSD, doctors inserted the modified skin cells into the nucleus basalis of Meynert, a group of cells about the size of your thumbnail at the base of the frontal lobe. This area contains many cholinergic nerve cells. Replacing NGF in the brain is somewhat like filling a car with gas; it gives the cells the ability to function and to send signals where they need to go.

The cells were injected only into the right side of the woman's brain, so comparisons can be made with what happens in the left side of the brain (control side). Researchers hope that the new cells will do two things:

1. Stop the brain cell loss associated with Alzheimer's disease.
2. Reverse the neurodegeneration by replacing damaged cells.

The woman has been released from the hospital and scientists should have some answers within three months. Neurologist Dr. Mark Tuszynski, who led the study, cautioned that this "is unlikely to be a cure." Rather, doctors hope that this technique will delay some symptoms and improve the quality of life for the patients. Research on animals, however, has been promising. UCSD researchers have shown that similar work in monkeys reversed the degeneration of brain cells that is similar to that seen in human Alzheimer's disease.

Humans seem to be the only animals who suffer from Alzheimer's disease, so the animal model is not a perfect one--results from experiments in animals may not hold true for humans. Furthermore, gene therapy is a complicated procedure, so even if this trial works, the technique will not gain widespread use immediately. While the verdict is still out on gene therapy, it could prove to be a useful weapon in what is now a small arsenal against Alzheimer's disease.