Une longue étude au Centre de recherche du Reeve-Irvine a montré que l'enzyme PTEN peut contrôler la régénération nerveuse aprés une lésion médullaire.
(La même news a été traduite ci-dessus)
8 Août 2010
Connections from brain shown in red; gap in narrow middle is the damaged region of the spinal cord. Image courtesy Oswald Steward, UC Irvine.
A research team including UC Irvine made nerve connections regrow in mice with spinal cord injuries — a scientific first that could lead to restoring function to paralyzed limbs in humans.
By deleting an enzyme in the brains of genetically modified mice that controls nerve regeneration after spinal cord injuries, they caused the nerve connections to regrow.
Normally, the enzyme cuts off such regrowth in adults.
“By deleting this molecular break, it turns back the clock,” said Steward, co-author of a paper on the process published online Sunday. “So the nerve cells in the brain are kind of young again.”
It took two years for scientists at UC Irvine and Harvard University to induce the nerve-cell regrowth in the mice. UC San Diego also took part in the study, published online in the journal, Nature Neuroscience.
The next question: finding out whether limb function can be restored in injured mice with the deleted enzyme, called PTEN.
“Our experiments are designed really to identify therapies that eventually could be used for people,” Steward said.
And the possibilities are not limited to spinal cord injuries.
Researchers have already shown that optic nerves can be regenerated using the same process.
And while the enzyme deletion process did not involve the use of human embryonic stem cells, treatments in which both are used together could help bridge difficult gaps in nerve growth that the enzyme procedure alone could not.
“We’ve succeeded in causing these connections to regenerate, but not perfectly,” Steward said. “And in particular, right at the injury site, we still face a pretty huge barrier. So, for example, one can easily imagine using stem cells to recreate a growth-permissive environment at the site.”
Geron Corp. announced just over a week ago that it would begin the first-ever clinical trials of acute spinal cord injuries using human embryonic stem cells, a treatment developed by UC Irvine’s Hans Keirstead.
The enzyme-deletion procedure must get past a few hurdles. The mice were genetically modified to make it easier to remove the enzyme. The scientists must show that the technique works without the help of modified genes.
“Obviously, we’re not going to get genetically modified people,” Steward said.
The treatment, like Keirstead’s, also works only within days of an injury; a major goal is to make it work on chronic injuries as well.
And the enzyme fulfills important jobs, notably suppressing tumors. The scientists must be able to start and stop the deletions when they wish to avoid the potentail runaway growth of cancer.
Still, the discovery is a genuine breakthrough, likely to lead to major advances — not only allowing the paralyzed to walk again, but restoring function in, for example, paralyzed hands.
“This is totally new,” Steward said. “Everybody we talked to says this is just really unprecedented as far as the kind of growth that we’re seeing. People have been working on trying to regenerate this pathway for spinal cord injury literally for 100 years. This is the first time there’s been significant success in getting these connections to regrow.”