UC San Diego has discovered a way to grow nerve fibers in rats with severe spinal cord injuries, a potentially big step toward treating some of the 300,000 Americans who are fully or partially paralyzed.
Researchers used stem cells to basically rewire the central nervous system, enabling the rats to regain some movement. The technique, reported in the journal Cell, causes connections from neurons to spread beyond the injury, restoring the ability of the brain and spine to communicate.
“New connections grew in very large numbers and over very long distances after the most severe form of spinal cord injury,” said Mark Tuszynski, co-author of the study and director of the UCSD Center for Neural Repair. “We are conducting experiments now to determine whether this can be translated to humans.”
The California Institute for Regenerative Medicine (CIRM), the agency that is distributing $3 billion in state funds for stem cell research, has awarded Tuszynski $4.7 million to further develop the advance, which he made with fellow UCSD neuroscientist Paul Lu.
“I’ve been in the business a long time and have never seen this degree of regeneration in rats. This is very significant work,” said Alan Trounson, CIRM’s president.
Tuszynski and Lu have been focusing on axons, the tiny fibers that transmit signals away from nerve cells. These fibers carry messages to other cells and to the spinal cord. They make up an essential part of the communications network in the central nervous system.
Scientists have been able to regenerate hundreds of axons in rats that have suffered a spinal cord injury, but not enough to reverse the damage. UCSD tackled the problem in research rats by creating a gel that contained neural stem cells. The researchers then placed the gel on the exact spot in the rats where the spinal cord had been severed.
Tuszynski said that technique led to the “growth of tens of thousands of new axons. This is unprecedented.”
The growth enabled the rats to regain some power in their joints and to move around to a limited degree.
“We further found that these stem cells send out new axons for truly remarkable distances in the spinal cord,” Tuszynski said. “Previous work has shown axon growth of about two millimeters. Axons in this study grew more than 10 times longer than this. Previously, it had been thought that new axons cannot grow well in the injured spinal cord. This work shows that axons from these early stage neurons can grow remarkably well in the injured adult spinal cord.
The technique was replicated in two human stem cell lines, including one that is already being used in a human clinical trial for amyotrophic lateral sclerosis (ALS), which is better known as Lou Gehrig’s Disease.
With the $4.7 million in CIRM money, Tuszynski plans to test the effectiveness and safety of the treatment over longer time periods, and scale up the treatment to larger animals. If successful, the studies would lead to human clinical trials.
About 11,000 people suffer spinal cord injuries in the U.S year. Roughly 80 percent are men, and more than half of the injuries involve people from the ages of 16 to 30.
“At a time when money for research is so jeopardized across many funding sources, it’s particularly noteworthy that CIRM has the capacity to support this promising work and take it to the next level, particularly for individuals living with spinal cord injury,” said Susan Howley, Executive Vice President, Research, Christopher & Dana Reeve Foundation.
(Story sources: Cell, UC San DIego, CIRM, National Spinal Cord Injury Association; Christopher & Dana Reeve Foundation.)