Mice Brains Can Fix Themselves
By Kristen Philipkoski

02:00 PM Nov. 01, 2004 PT

Harvard scientists have manipulated stem cells already present in the
brains of mice to induce the birth of new neurons, an advance once
considered impossible by most scientists.

They induced the birth of new cells by killing nearby neurons in
mice, which set off a cascade of events that led to stem cells, also
called precursor cells, producing new neurons in the cerebral cortex.
If scientists can turn this into a therapy for humans, it would mean
that patients could literally heal themselves with stem cells already
present in their brains.

The researchers' goal is not to create a therapy that would kill
neurons in order to activate the birth of new ones. Rather, they hope
experiments like this one, which appeared in the Proceedings of the
National Academy of Sciences online, will lead to new ways to grow
neurons. Researchers could eventually identify key molecules involved
with neuron birth and translate them into drugs, said Jeffrey
Macklis, a researcher at Harvard Medical School who led the study.

"(The neurons) developed into mature neurons that not only took up
proper locations within the brain, but reconnected to the spinal
cord," Macklis said.

The newborn neurons took the place of many damaged neurons in the
mice. The work could be a model for neuron replacement in spinal cord
injury or diseases including Alzheimer's, Parkinson's and Lou
Gehrig's. And such a therapy would avoid any immune or other
complications that might result from stem-cell transplantation.

Researchers long thought the adult central nervous system had little
or no ability to regenerate. But recent studies have shown some
regeneration, mainly in the hippocampus and olfactory regions. In
2000, Macklis and his colleagues showed for the first time they could
induce neurogenesis (the birth of new cells) in complex brain regions
such as the cerebral cortex. Other experiments showed that
surrounding brain cells turn on molecular signals when certain types
of neurons die.

In this latest work, the Harvard researchers wanted to see if they
could specifically generate corticospinal motor neurons, which are
located in the cerebral cortex and which play important roles in
neurodegenerative diseases.

The researchers used a special molecule activated with long-
wavelength light to kill neurons, injecting it into the brains of
adult mice. The photo-activated molecules selectively killed
corticospinal motor neurons, which live in the cortex and control
voluntary motor function.

Neurogenesis occurred shortly after the neurons died. Immature
neurons emerged from another region of the brain, the subventricular
zone, and migrated into the cortex. They matured into neurons that
resembled corticospinal neurons. Some of them survived for more than
a year and even sent signals all the way into the spinal cord.

SOURCE: Wired News
http://tinyurl.com/6rnpp

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