Embryonic stem cells have been used to restore limb movement in paralyzed mice, say scientists at Johns Hopkins University School of Medicine, USA. The embryonic stem cells formed new nerve connections in the paralyzed mice.
This research is seen as proof by scientists that one day paralyzed humans will be cured as a result of stem-cell grafts. It may be several years away, but the evidence that it will come is much more compelling now.
You can read about this in the journal Annals of Neurology.
The difference between this experiment and others is that this one has managed to get the neurons to make functional connections to muscle. Previous studies managed to use stem cell therapy to create nerve cells only.
For a limb muscle to move, a brain cell must send a message to a motor neuron, which lies in the spinal cord. The motor neuron in the spinal cord then reaches out to the muscle using axons, long fibers. An impulse is sent down the axons and the muscle contracts. The message relay is done through a complicated system of signalling chemicals.
Dr. Douglas Kerr, lead researcher, and his team, devised a neural concoction that lead to the creation of a network of new motor neurons that could restore the brain’s ability to get its message all the way through to the limb muscles.
The scientists got the mouse embryonic stem cells to turn into motor neurons. By adding retinoic acid and sonic hedgehog protein, they managed to get the new motor neurons to exist happily in the spinal cord. They were then delivered into the spinal chords of paralyzed mice.
Naomi Kleitman, U.S. National Institute of Neurological Disorders and Stroke, who helped fund the study, said “We know that there are proteins in this area that inhibit axons from growing in adult animals. They’re part of how we keep our nervous system from going haywire during normal function.? The scientists had to find a way of preventing this stopping of axons from growing. By adding cyclic AMP and rolipram the scientists were able to stop the body from blocking the growth of axons.
They then managed to get the right axons to grow in the way they wanted by using chemicals which acted like axon growth traffic lights.
In one mouse, 4,100 new motor neurons were created in the spinal cord. Of those, 200 left the cord, of which 120 reached the skeletal muscle. The scientists say the new connections look identical to the ones seen in healthy mice.
Of the 15 paralyzed mice, 11 regained muscle function and strength.
Researchers say further studies are needed, but stressed that this is probably the beginning of something which one day may help paralyzed humans move again.
Written by: Christian Nordqvist
Editor: Medical News Today