Purdue News

January 18, 1983 Electrodes Rejuvenate Cut Spinal Cords West Lafayette, Ind. – A basic similarity between the primitive spinal cords of lampreys and the sophisticated ones of humans prompts a Purdue University researcher to see new hope for paraplegics. Professor Richard Borgens' ideas on nerve regeneration through implanted electrodes have already been used to speed regeneration of nerves in the spinal cords of larval lampreys after the spines of the eel-like fish had been severed. Borgens, who reported on his work at an international scientific meeting in London, says he is "very excited about the state of spinal cord trauma research and where it is going. It used to be that severe spinal cord injuries were considered hopeless, but attitudes about this have changed markedly in the last five to seven years. "Many now view paraplegia as a potentially treatable condition." Borgens notes that his research with lamprey larvae is based on a time-honored scientific concept that all injured tissue drives electric current through itself. In fact, as a National Spinal Cord Injury Foundation fellow at Yale, Borgens and his colleagues were the first to measure the natural electric current flowing into a cut spinal cord, that of a lamprey. The biologist, an assistant professor of anatomy in Purdue's School of Veterinary Medicine, explains that although lampreys are among the few vertebrates which can naturally regenerate neural function across a severed spinal cord, it takes four to five months for the nerves to re generate across the cut. An electric field imposed across the cut can induce regeneration about three times faster, says Borgens. "Having already shown that the injured spinal cords of larval lampreys drive steady current through themselves," he says, "we artificially enhanced this electric field with batteries and strikingly enhanced the regeneration of severed spinal cord nerves in these fish." He remarks that this suggests if the same kind of technology could be applied to the spinal cords of higher vertebrates, similar results might be expected. "We don't know that yet, but we have every reason to believe that's a reasonable expectation now," Borgens observes. "With these results, we fully intend to try this approach with mammals." He points out that although lampreys are a primitive form of vertebrate, they have neurons with a complex anatomy analagous in many ways to that of higher vertebrates, even though unlike the latter, lampreys do have some active regenerative capacity in their spinal cords. But wouldn't this difference be critical in trying to relate human and lamprey responses to spinal cord injury? "While the lamprey does have a slight capacity to regenerate a severed spinal cord," remarks Borgens, "we're focusing on the responses of individual nerves to injury, trying to learn something about what controls their regeneration and to what extent. "Whatever we learn, we're certainly going to try to apply to mammalian nerves; if we can learn how to control the regeneration of identifiable neurons in one vertebrate, then there's some reason to believe we'll be able to control nerves and their responses to injury in other vertebrates as well." He says he believes that "once we understand the nature of the signals and controls that operate basically in all cells in their responses to injury, then perhaps we'll be able to adapt these findings to higher vertebrates and reawaken a lot of dormant regenerative abilities. I say dormant because I don't think mammals cannot regenerate nerves and other tissues; we just don't know the proper controls. "I think naturally produced electric signals are one of these." The simplicity of lampreys' spinal cords, observes Borgens, makes them ideal for such research. "Studying spinal cord injuries in the mammal is difficult," he says. "One cannot identify the many nerves that project up and down the cord after injury; there is scar tissue, damage to the blood supply, and orthopedic problems resulting from the injury." With the lamprey, a jawless fish which is among the most primitive vertebrates in existence, there are many fewer complications, he says. He explains that the lamprey doesn't have blood vessels within its spinal cord, so cells in the cord are not as affected from interruption of blood flow after the cord is severed. Just as important, he adds, is that the lamprey brain and spinal cord have large, individual neurons that are easy to identify even after injury. Also, says Borgens, the lamprey's brain and spinal cord can be removed and kept "alive" in a culture 10 to 12 days for further manipulation and study. One of the especially interesting findings in spinal cord research so far, mentions Borgens, is that in many animals that regain function after spinal injury, it's not necessary for all the nerves to regenerate across the damaged area--or even for them to make the appropriate connections--in order to produce significant degrees of functional recovery. "This," he remarks, "suggests that the task of achieving some degree of functional recovery in humans may not be an impossible one." "There's more to spinal cord injury than the inability to walk," he says. He recalls that an official of the American Paralysis Association, herself a paraplegic, pointed out to him that almost any type of improvement would be a godsend. "Her view was, 'If anyone could develop a way to restore bladder control, or sensation, it would improve our lives radically."' Borgens' current research is funded by the Paralyzed Veterans of America and the National Institutes of Health.   Contact Purdue News Service (765) 494-2096 or purduenews@purdue.edu. To the Purdue News and Photos Page