Scientists turn
Stem Cells to Neurons
SAN FRANCISCO(AP) Researchers at the
University of Wisconsin, Madison
reported Sunday that they've whipped up
an exciting _ but intricate _ new recipe
that could someday treat spinal cord
injuries or provide a cure for
amyotrophic lateral sclerosis, better
known as Lou Gehrig's disease.
Step one: Take human embryonic stem
cells, the microscopic dots that have
brought condemnation from the pope,
opposition from the president and people
generally opposed to abortion. Add
pinches of chemicals, dashes of other
biological ingredients implicated in
brain growth at just the right moment
and voila: brain cells called motor
neurons that control every body
movement.
The conclusion, reported online in
science journal Nature Biotechnology, is
important for two reasons. First, stem
cell scientists have struggled to
accomplish what researcher Su-Chun Zhang
and his colleagues have just
accomplished. It took Zhang's team two
years of tedious trial-and-error
experiments to direct stem cells to turn
into motor neurons.
Perhaps more important, Zhang's recipe
shows researchers that timing is
everything when adding their chemical
cocktails to stem cell stews. Stem cells
are vulnerable to successful human
manipulation for only the briefest of
moments _ and at different intervals
depending on the results each researcher
craves.This shows that you can't dump
whatever growth factors you want in
there," Zhang said. "It's not that
simple. It's very specific. You have to
have the right cocktail in the right
amount at the right time."
Other scientists said Zhang's work also
will help researchers better translate
data gleaned from decades of animal
experiments into human terms. Scientists
were losing faith that 25 years of work
with the embryonic stem cells of mice
had little direct correlation to humans,
said Harvard University neuroscientist
Ole Isacson.
But with Zhang, and others, showing that
the biological clock ticks differently
in different animals and in each type of
cell, it appears translating animal data
to human terms is more about timing than
biology.
"That is also somewhat reassuring," said
Isacson, who has created
dopamine-producing brain cells from stem
cells. Parkinson disease patients lose
dopamine cells, which help regulate body
movement.
Embryonic stem cells are created in the
first days after conception and
ultimately turn into the 220 or so types
of cells that make up the human body.
Scientists believe they can someday
control what stem cells become and when,
using that power to replace damaged and
dead cells that cause a wide range of
suffering, from diabetes to Parkinson's.
But harnessing that power has proved
elusive in all but a few cell types such
as heart and two other types of brain
cells.
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