By JR Minkel
In a new study, rats were spared
the limb-weakening effects of a stroke if they were treated with brain tissue
cultivated from human embryonic stem cells. But unlike similar experiments, the
transplanted cells gave no sign of causing tumors, according to a report this
week in the online journal PLoS One.
Researchers say that if they can
build a string of such successes in a range of animal models, they can make a
stronger case for testing the cells in people. "This is really exciting,
just to overcome this obstacle of tumorigenicity," says
Investigators have had success
of late creating stem cells, or cells very similar to them, from new sources
such as adult human tissue. But the ongoing scientific challenge is to harness
those cells' ability to morph into the different adult cell types and thereby
develop new treatments for debilitating diseases such as stroke, which strikes
about 700,000 Americans every year, according to the U.S. Centers for Disease
Control and Prevention.
Daadi and his colleagues
transplanted specially grown human neural stem cells—precursors of neurons and
other neural cell types—into the brains of rats made to suffer a stroke in the
right hemisphere of the brain, which had sapped the strength from their front
left paws. Rats that received the transplant recovered strength in the impaired
limbs, as judged by a test in which the rodents explore a tube. Animals given a
sham injection regained little or none of the lost strength, the group reports.
The researchers found no sign of
tumor growth in the brains of the healed rats or after stem cell injections
into the bodies of healthy rats. Daadi attributes the success to their way of
harvesting neural stem cells from human embryonic stem cells, which he says
weeded out unwanted cell types that might grow into tumors.
An application for early human
testing of a stroke treatment using cells derived from human fetal brain
tissue, developed by the Guildford, England–based stem cell company ReNeuron
Group, PLC, is currently on hold with the Food and Drug Administration, pending
additional data.
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