Researchers at Georgetown University Medical Center have announced that they have achieved "encouraging initial success" in repairing the crushed spinal cords of laboratory animals.
In their cautiously phrazed announcement, the researchers reported that five of 40 dogs, whose spinal cords were surgically destroyed, walked over surgery designed to stimulate the repair and regrowth of the damaged nerves.
If traditional medical wisdom were correct, the animals would never have recovered, for one of the givens in medicine has always been that a damaged spine cannot be repaired.
Dr. Carl C. Kao and his colleagues said their findings will not help persons who are paralyzed. They also said they are anywhere from six months to several years away from trials on humans.
The surgical portion of the technique developed by Kao, an associate professor at Georgetown and chief of neurosurgery at the Veterans Administration hospital here, involved filling the gap in the injured spine with pieces of nerve from another portion of the dog's body.
When the spinal cord is crushed - and crushing, rather than cutting, accidents are the most common in humans - the cells in the crushed portion die, preventing the stransmission of any impuses from the brain to any area of the body below the break.
Kao explained that the biggest problem in regeneration work is finding the right time to operate. If the surgery is performed too soon after the injury, the area at each end of the break dies, leaving the implanted nerves isolated and useless.
If the surgery is performed too late, he said, the blood clots at each end of the crushed area cause scarring that prevents the transmission of messages.
Operating between one and two weeks after the injury, Kao uses suction "to remove the dead tissue, and the end of the spinal cord is still very much alive."
After inserting the small pieces of nerve - each about five millimeters long - Kao "glues" the ends of the nerve pieces to the ends of the spinal cord with millions of cultured nerve cells, prepared by Jean R. Wrathall, of Georgetown's anatomy department.
In order to study the success of the procedure, Donald D. Rigamonti and Mark R. Braford, also of the anatomy, department, study the passage of electronic impulses from the animal's brain to the limbs below the repaired area of the spinal cord.
Kao said that even in the dogs that didn't walk, some of the impulses made it across the nerve bridge in the cord. Kao did his work on the dogs while working at the Medical College of Wisconsin and has been working on cats at Georgetown.
He said he should know by January how successful the procedures have been in the cats.
The researchers delivered three papers yesterday on their apparent breakthrough at the annual meeting of the Society for Neuroscience in St. Louis.
In an interview, Kao said his interest in spinal cord injuries began during his third year in medical school on Taiwan.
"I had a patient who had career of the spine. When I first saw this patient he could not move, could not pass water, could not have a bowel movement by himself . . . So I really saw the human suffering and saw this as the problem of the future."
After an internship at National Taiwan University, and initial residency at the University of Illinois, Kao went to the Indiana University, "where I met Dr. Leslie Freeman. He had been doing this work (with spinal cord regeneration) for about 20 years. He thought the scarring was the problem.
"I reviewed all his papers," Kao continued, "and I proposed that the scar could be easily removed. You could culture the brain. Scoop a little piece of the brain and put it in a culture medium. The cells will grow and then you can put it in the spinal cord and there will be no scar. But then the cavity (formed by the dying tissue) was there, and we found out that the cavity was the problem.
Kao left Indiana for a neurosurgery residency at the Mayo Clinic, and then moved on to Madison, Wis. "When I went to Madison I took three or four years to just sit down quietly and study how the cavity was formed," he said. "It is a very, very, important process."
From his "three or fur years of just sitting" Kao learned that the axons, the main portion of the nerve fibers, in the spine were trying to grow down into the break in the spine.
"The axons were trying to come down," he continued, "and they have lots of power to come down, but when they get to the end (of the break) the insulation of the nerve in the spinal cord is so sticky and fragile, it's just like a sleeve." He paused and grasped his right jacket sleeve with his left hand, preventing his right hand from breaking free of the sleeve.
"There's no way the axon can come out unless it explodes, and when it explodes it explodes itself. And it has enzymes that destroy the entire area. So any attempts at regeneration always end in self-destruction.
"We studied this mechanism," Kao said "and found that in about a week it looks like th end (of the cord) is settled. So we developed the delayed nerve grafting, going back in (to the injured spine) in about a week to take advantage" of just the right passage of time.
Nerve grafting had been attempted previously, Kao said, but no one had ever been known to wait a week before operating. "They'd cut and put the nerve in right away. This was done a long, long time ago, and over and over again." And always without success.