The researchers say that this arrangement reduces the amount of a plaque that is the main trait of Alzheimer's disease. The combination, according to the scientists, activated the regeneration of neurons that are destroyed by Alzheimer's and are crucial for healthy brain functions.
"It's very exciting. If our success with mice can translate into the human brain, it could give hope to patients and their families," Sugaya said.
Six years ago, Sugaya reported that brain stem cells transplanted into aged rats seemed to become functional neurons and improved age-associated memory loss, with no side effects.
When Sugaya transplanted stem cells into the brains of Alzheimer's-model mice, he found that the stem cells did not form any neurons. He found that surplus amounts of the amyloid-precursor protein (APP), which produces a component of the plaques, a hallmark of Alzheimer's, prevent stem cells from becoming neurons.
The research team treated Alzheimer's-model mice producing human APP with phenserine, which is known to reduce the amount of APP in the brain. The APP level in the brain of treated mice was reduced by up to 50 percent, which would provide best possible conditions for the brain stem cells to become neurons. Under this environment, the research team found that stem cells transplanted into the brain successfully produced neurons.
Sugaya is now investigating whether a combination of phenserine and his compound (NBI-18), which increases brain stem cells by 600 percent, could become another way to treat Alzheimer's. Increasing neurons may be important in improving brain function, particularly in people with neurodegenerative diseases.
"It's one thing to be able to manipulate stem cells for creating specific tissue types - the brain, the eyes, the heart - but every disease is different. Simply producing transplantable cells isn't enough. You have to think of how the disease works and figure out ways to apply the cells. Sometimes that may mean coming up with other compounds that help deliver the therapy," he said.
The research findings are published in PNAS, Proceedings of the National Academy of Sciences.