Born again. A dark stain labels neurons in a healthy rat hippocampus (top). Many cells are killed after a simulated stroke (middle), but new cells take their place in treated rats (bottom).

Brain Cells Renewed in Rats

The adult brain is notoriously bad at healing itself. But a new study suggests it may just need a push to get started. Injections of growth factors yielded new brain cells in adult rats suffering from a stroke-like injury. The treatment restored some cognitive function, which raises the possibility that the brain's own cells could be stimulated to repair brain damage in humans.

The scientists, led by neurobiologist Masato Nakafuku of the University of Tokyo, simulated strokes by briefly shutting off arteries in the neck of rats. Then they infused a cocktail of growth factors directly into the animals' brains for several days. The growth factors didn't do anything to help the dying cells. But within a month, the rats had regained 40% of the neurons they'd lost--more than twice the regeneration that occurred without the growth factors. More importantly, the team reports in the 23 August issue of Cell, the treatment led to improved performance on a test of rat cognition--finding a submerged platform in a water maze.

The new cells grew from progenitor cells, stemlike cells that can divide to produce neurons. Many scientists believe that stimulating endogenous stem or progenitor cells to repair damage could be the ideal treatment for many diseases and injuries, because it circumvents problems--such as immune rejection or tumor creation--raised by injecting stem cells into a patient. But that's particularly difficult in the central nervous system, where little cell regeneration normally occurs.

So it's encouraging that the new study suggests stem cells are more widespread in the hippocampus than had been thought, says neuroscientist Mark Mattson of the National Institute on Aging's Gerontology Research Center in Baltimore, Maryland. "This is a very important study with implications for the treatment of patients," says Mattson. "These neurons are critical for learning and memory and are selectively damaged in stroke and Alzheimer's disease."

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Posted in Brain & Behavior