Using a mix of two standard serums, Masato Nakafuku of Japan Science and Technology Corporation and his group stimulated new nerve cells to grow in the animals' injured hippocampus, a region involved in storing memories (1). The mice did not develop some of the learning difficulties usually associated with such an injury.
Researchers had assumed that the brain was unable to repair these cells, called pyramidal neurons. Patients who suffer stroke in this area have severe and irreversible memory problems.
It's really quite remarkable, says Sally Temple, who studies nerve regeneration at Albany Medical College in New York. Temple warns that the results need to be repeated before she is fully convinced.
The findings add to growing evidence that treatments might one day coax people's brains into repairing themselves after stroke, Parkinson's disease or other disorders. I'm extremely confident, says neuroscientist Steven Goldman of Cornell University in New York.
Several areas of the adult brain spontaneously make new cells throughout life. Recently, researchers have begun to alter the type or number of new cells using certain growth promoters.
Hippocampal pyramidal neurons, however, were thought unable to regenerate. It's surprising, says Goldman, but I don't think anyone had bothered to look.
Nakafuku's team starved mice of oxygen, damaging their brains. Then they infused the animals' brains for three days with two proteins that trigger cell division. They found that cells outside the hippocampus made new nerve cells that migrated into the damaged area, and appeared to form normal connections with other cells.
It is unlikely that the same serums could be used as human drugs, however, as they could trigger other cells into becoming tumours. Researchers will need to find new drugs that stimulate cells to make very specific cell types that travel to a damaged area. They also have to work out an efficient way to deliver these drugs to brain cells. This work is at a pretty primitive stage, says Goldman.
Nakatomi, H. et al. Regeneration of hippocampal pyramidal neurons after ischaemic brain injury by recruitment of endogenous neural progenitors. Cell, 110, 429 - 441, (2002).
23 August 2002