By Christine Dell`amore Apr 27, 2006, 0:12 GMT
WASHINGTON, DC, United States (UPI) — A new stem-cell technology has allowed rats with spinal-cord injuries to walk again within two weeks, an advance that could one day help people with traumatic spinal-cord injuries.
The rats that were given immature immune system support cells, or astrocytes, experienced a 40-percent rise in nerve-fiber growth at the site of the injury in just eight days.
‘This is the first time an astrocyte has been generated in tissue culture and shown significant recovery of function,’ said lead author Dr. Stephen Davies, assistant professor of neurosurgery at Baylor College of Medicine in Houston.
‘Stem cell technology is moving at a tremendous space at the moment, and this (study) makes advances in how to use that technology.’
The research, funded in part by the Christopher Reeve Foundation, will appear April 26 in the open-access Journal of Biology.
Scientists have been focusing on using stem cells to repair the central nervous system in humans for several years. By definition, stem cells, either adult or embryonic, can respond to signals in tissue and become cells of that type of tissue. Adult stem cells come from the body`s tissue or organs, and embryonic stem cells derive from eggs that have been fertilized in vitro.
When an injury occurs to the spinal cord, the body creates scar tissue to prevent infection, a mechanism that has little effect on the skin but is disastrous on the spinal cord, Davies said. That`s because scars inhibit nerve-fiber regeneration, creating paralysis and other problems.
Due to the scarring, transplanting adult stem cells into a damaged spinal cord does not spur nerve growth.
So Davies and colleagues wondered if they could signal cells similar to stem cells, called glial-restricted precursors, or GRPs, to become a specific type of embryonic astrocyte — a type of cell thought to have an amazing ability to repair embryonic spinal cord — and whether transplanting these cells into adult spinal cord injuries would prevent scarring and encourage nerve growth.
To do this, scientists generated a specific type of astrocyte support cell from the GRPs, which were discovered by cell biologist Margot Mayer-Proschel of the University of Rochester Medical Center.
Rats given this specialized astrocyte cell formed less scar tissue and nerve damage, as opposed to the control group that was transplanted with un-cultured cells. Their locomotion also improved to the point where they could walk completely normally up to two weeks after receiving the treatment.
Also exciting, Davies said, was that the brains of the rats also showed improvement. When damage to the spinal cord occurs, neurons in the brain, which have nerve fibers that run down the spinal cord, often degenerate. But with the astrocyte transplant there was a significant suppression of degeneration: Up to 80 percent of neurons did not atrophy, Davies said.
Davies` work does not focus on remyelination, a technique of other stem-cell researchers to restore myelin, a substance that protects nerve cells, in the central nervous system. Instead, he focused on changing the structure of the injury site itself. The transplanted cells may have also encouraged uncut nerve fibers around the injury to promote new connections.
The GRPs are of great interest, and the study reaffirms they are an attractive method for repairing spinal-cord damage, said Dr. Wise Young, a neuroscientist and director of Rutgers University`s W.M. Keck Center for Collaborative Neuroscience.
‘This is going to create a lot of excitement in the field,’ he said of Davies` work.
Young, a pioneer in treating spinal-cord injury, has organized clinical trials in China, where he plans to test the influence of umbilical-cord blood stem cells in the central nervous system.
‘The paper shows very compelling data for moving GRPs to clinical trial as soon as compatible human cells can be obtained,’ Young said.
But first, researchers would have to overcome a huge obstacle: the lack of availability of stem-cell lines in the United States. It would take hundreds of thousands of the GRP cells to act in a person, Davies said.
Even so, this could be a short-term dilemma: Young said he is confident that it won`t be long before scientists can make any cell into a stem cell.
‘A stem cell is just a cell expressing certain genes, and there`s nothing more mysterious than that. We just have to know what the genes are,’ he said.
Davies plans to continue researching the effect of GRPs on rats.
‘We have a 40 percent efficiency in (repairing) nerve fibers. I want to see more than 90 percent,’ he said.
Eventually, Davies hopes the new technology can be used to repair central nervous system injuries in people in the future, as well as other neurogenerative diseases.