Scientists are exploring the connection between Alzheimer's and the brain's ability to regenerate neurons.
If you scrape your knee or break a bone, new cells repair the damage before you even know it. Other organs in the body are even better at regrowing themselves: The cells lining the gut regenerate every three to four days. In contrast, the brain has a limited capacity to regenerate and repair itself.
Even when brain cells begin to die off in Alzheimer’s or other types of dementia, there aren’t nearly enough new cells dividing and surviving to repair the brain.
Up until the mid-20th century, scientists believed that no new brain cells at all formed over the lifetime. But in the 1960s and 1970s, scientists discovered dividing cells in the brain through a process called neurogenesis. The rate of formation for new neuronal cells decreases with age. Newborn cells emerge near the hippocampus, a region of the brain important for memory — one affected early on in Alzheimer’s.
If brain cells are dying over the course of Alzheimer’s disease, could stimulating the production of new cells solve the problem?
A 2019 study found that among people with Alzheimer’s, those with more neurogenesis — more new brain cells being formed — had less cognitive impairment. These findings came with an exciting realization: Increasing the brain’s ability to regenerate brain cells could stave off cognitive decline and dementia.
The previous year, another study found that stimulating the production and survival of new neurons in mouse models of Alzheimer’s did in fact improve cognition. The researchers found that brain-derived neurotrophic factor — a signaling molecule that helps neurons grow — even mimicked the effects of exercise on cognition.
One of the researchers involved in this work, María Llorens-Martín at the Autonomous University of Madrid, believes neurogenesis might hold the key to figuring out what causes Alzheimer’s and how to diagnose it early.
“What is failing in the environment that is making these neurons die prematurely or making it very difficult for them to get connected appropriately?” she said in an interview with The Scientist.
Although this work raises more questions than it answers, harnessing the brain’s own regenerative ability could stave off or even halt the progression of Alzheimer’s.