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For over a century, since the time of the great neuroscientist Alois Alzheimer (1864-1915), medical researchers have been able to identify the devastating effects of Alzheimer's disease by studying the brains of the deceased. A recent innovation, however, allows researchers to study the disease in living brain tissue.
Growing Brain Tissue in a Petri Dish
The fundamental problem in Alzheimer's research has always been that there is no easy way to determine whether a drug has had an effect until after the patient is dead, and by the time a person with Alzheimer's expires, different brain samples tend to look alike. Researchers have been able to test drugs on mice that have a disease similar to Alzheimer's, but results in treating mice do not necessarily translate to results in treating humans.
The breakthrough method of studying Alzheimer's disease arose from a suggestion from Dr. Doo Yeon Kim of the Massachusetts General Hospital's Genetics and Aging Research Unit to his colleague Dr. Rudolph Tanzi that they study brain cells grown in a gel (typically spread over a Petri dish).
Dr. Tanzi took living human brain cells, gave them the genes for Alzheimer's disease, and placed them in a Petri dish. In about a month the cells develop plaque, a substance that looks something like a scrubbing pad. Plaques consist of broken-down and twisted proteins that accumulate between the cells.
In another few weeks, they formed the mass of spaghetti-like neurofibrillary tangles that form the lumps and bumps in the brain that are characteristic of the disease. Tangles appear as nerve cells die. Plaques and tangles interrupt the flow of electrical signals between neurons, and eventually neurons that can no longer communicate with the rest of the brain atrophy and die, leaving behind broken circuits.
Not a Perfect System, But a Major Improvement
A bunch of brain cells growing in a dish in a laboratory, of course, is not functionally equivalent to the human brain. Especially signficant for Alzheimer's research is the fact that cultures of neurons grown in the lab don't include cells from the immune system, which are believed to regulate and accelerate the formation of the tissue-destructive plaques and tangles. However, the ability to observe the formation of plaques and tangles in living brain tissue is of enormous value in testing potential new drugs to treat the disease.
Dr. Tanzi and colleagues' discovery is also important for another reason.
In a few cases, people have died of Alzheimer's and found not to have plaques and tangles when their brains were examined at autopsy. And in a few cases, people have lived free of Alzheimer's but found to have the physical indications of the disease in their brains.