The day a skiing accident paralyzed John Kessler’s daughter was the day he decided to dedicate his research efforts to spinal cord injuries.
Over the past seven years, this motivation has propelled Kessler, Chairman of Northwestern’s Department of Neurology, to the forefront of the field. With a combination of nanotechnology and biology, he and Prof. Samuel Stupp have suppressed scar tissue in spinal cords and stimulated nerve regeneration in mice using a nano-engineered gel. The research, which may someday lead to treatment for humans, was published earlier this month in the Journal of Neuroscience.
“There is a growing amount of research that integrates nanotechnology with medicine, drug delivery or gene delivery, but it is not very common to integrate nanotechnology with regenerative medicine,” said Stupp, a Board of Trustees professor of Materials Science, Chemistry and Medicine. The 1977 alum of NU’s Graduate School added that NU scientists are also investigating regeneration of bones, cartilage and heart tissue after a heart attack. “We were pioneers in that area.”
The gel has nanostructures called peptide amphiphiles that self-assemble into noodle-like fibers when injected into the body, said Stupp, who directs the Institute for BioNanotechnology in Medicine. He and Kessler published an earlier study in 2004 on the same gel tested in a controlled test-tube environment. But this recent study demonstrates the gel’s success in living mice, said Stupp.
Kessler’s research examines the most common type of spinal cord injuries, which occur when the spine is compressed and bruised.
“When the spinal cord is injured, it’s like cutting a telephone cable,” Kessler said. “All the axons, which are the long processes from the cells in the brain growing down the spinal cord to hook up with the cells at the bottom of the spinal cord, get cut.”
Although the signals that control functions such as leg movement are severed, the spinal cord itself is rarely completely cut, he said. But the nerves, which have the capacity to regrow, don’t reconnect by themselves because of the “inhospitable environment.”
“There’s a lack of molecules to tell the fibers to grow,” Kessler said. “More than that, there is actually a set of molecules that get released from damaged materials that inhibit the fibers from growing.”
Each square centimeter of the gel’s fibers are covered with about a quadrillion biological signals that prevent a scar from forming and prompt the motor and sensory neurons from both the lower and the upper parts of the spinal cord to regenerate, Stupp said.
The innovative gel is significantly different from the implantation method that most scientists use, Kessler said. But Prof. Lonnie Shea of the chemical and biological engineering department combines both techniques in his research with rats.
“We implant a structure that mimics the architecture of the spinal cord, which hopefully will allow us to provide a structure that promotes regeneration,” he said.
Shea has also been running trials using his implanted material to deliver protein and DNA with Stupp’s gel injections to limit inflammation.
“We’re trying to use a biomaterial approach and nanotechnology to create and alter the environment locally,” he said.
But neither project addresses cases of damaged spinal cords injured months or years ago, such as that of Kessler’s daughter. That’s the next step, Kessler said, even though the inhibitory scar tissue will already have formed.
“It might be that we have to go back in and re-injure the spinal cord and then treat it,” he said.
And it still could be years before the research and the gel can be effective in humans, who clearly have much thicker and longer spinal cords than mice, Kessler said.
“As a scientist, I have a lot of goals,” he said. “I would love to be the person who puts the last piece in the puzzle. But as a physician and as a father, I don’t care who does it. I just want it to be done.”
