Researchers have discovered a class of cells in the developing mouse brain that have a penchant for roaming. The find, reported in the May issue of Nature Neuroscience, might lead to new strategies for the treatment of neurodegenerative diseases such as Huntington's and Parkinson's diseases.
Some scientists nurse hopes of curing neurodegenerative disease by replacing dying cells with neuronal stem cells, cells from embryonic tissue that can develop into any kind of neuron. One problem with this approach is that transplanted cells stay where they land, which makes it difficult to treat afflictions in which brain cell loss is more widespread. To find out whether some precursor cells might be more successful at roving than others, neurobiologists Hynek Wichterle and Arturo Alvarez-Buylla at Rockefeller University in New York decided to test the mobility of cells from various regions of the embryonic mouse brain.
First, the team cultured slices from different brain regions in a gel in petri dishes. They noticed that many cells from the forebrain, the front-most part of the developing brain, a region called the medial ganglionic eminence (MGE), started moving through the gel, while others stayed put. When they later injected the cells from different regions into the brains of adult mice, the MGE cells moved on average eight times farther than the rest, or up to 1.3 millimeters from the injection site--quite a distance in the minuscule mouse brain. The MGE cells even crossed into other brain areas, and they turned into real nerve cells; about one third became a specific type of neuron that makes the inhibitory neurotransmitter GABA. Therefore, Wichterle says, MGE cells show the most promise for treating conditions with defects in the GABA-system, such as Huntington's disease and a certain type of epilepsy in which GABA is in short supply.
Neuroscientist Anders Björklund of Lund University in Sweden calls the study "a step in the right direction." In addition to replacing lost nerve cells, MGE cells altered to carry a therapeutic gene might also be used for delivering drugs to the brain, he says. But Björklund adds a cautionary note: His own research suggests that the lesions seen in neurodegenerative disease may inhibit the migration of transplanted cells.