Talk about a spine-tingling sensation.
Yesterday at the Engineering Tissue Growth International Conference and Exposition, a spinal cord researcher shared exciting preliminary findings from an experimental technique that uses immune cells to repair severed spinal cords.
Although their injuries should have made them permanently paralyzed and numb, three patients who received the therapy have begun to feel light touches and pin pricks. Two can now voluntarily twitch some muscles. And "there is still continuous improvement, so we're happy," said Dr. Valentin Fulga, a senior vice president at Proneuron Biotechnologies, after his presentation to tissue engineering experts. If the results hold up, it could be the first case of a therapy that can restore sensation and function to people with severe spinal cord injuries. Proneuron says there are 12,000 spinal cord injuries in the United States each year.
The spinal cord is a rope of nerves that delivers impulses between the brain and the body. When the cord is completely cut through, or transected, signals can no longer be transmitted to and from the nerves below the injury. If the injury occurs high on the cord, the patient may not have any movement or sensation below the neck. An injury that occurs a few levels lower may leave the patient with use of the arms, but paralyze the legs.
Scientists once thought such spinal cord damage could not heal because nerve cells do not regenerate. But animal experiments conducted by Michal Schwartz of the Weizmann
Institute in Israel indicated otherwise. In a 1998 study, which was published in Nature Medicine, she cut the spinal cords of 22 adult rats at the chest level and then injected the cords with macrophages, a type of immune system cell. Twenty weeks later, most of the rats were able to move their hind legs.
"Macrophages are key players in the inflammatory reaction and starting the wound healing process," Fulga said. Once placed at the injury site, the researchers reasoned, the cells could promote regeneration of the spinal cord.
Humans, like rats, don't have macrophages in the central nervous system, namely the brain and spinal cord, but they are easily extracted from the blood. The cells are activated in a lab dish so that once they are in the spinal cord, they can secrete chemicals and perform their usual functions.
The first human to receive the treatment, which was developed by Proneuron, a privately held company based near Tel Aviv, was 18-year-old Melissa Holley of Ridgway, Colo. Her spinal cord was severed in a car accident on June 25. Ten days later, an air ambulance flew her to Sheba Medical Center in Tel Aviv, where her spine injury was injected with her own recently harvested macrophages. The study protocol dictates that the cells be given within 14 days of the injury, a window based on animal studies.
Holley told the Denver Post in December that she began feeling the muscles contract in her left inner thigh on Thanksgiving Day, then quickly discovered she could control the muscle movement. Now, she can contract muscles of both legs and, with effort, wiggle some of her toes.
Fulga noted in his talk that Holley could not feel anything below the middle of her torso after the accident. She now has sensation, although not completely normal, throughout the injury-affected area.
The second participant in the trial, an Israeli, became quadriplegic after his injury. Nearly five months after treatment, he started regaining movement. He can flex his wrists and move his thumb, Fulga said. "All three patients recovered significant sensory function all over the body," he said. The third participant, also an Israeli, was treated four months ago and has not yet had any movement of his legs.
Tests of message transmission between the brain and the limbs suggest that nerve pathways are being restored in the patients. How much more improvement will occur is not known. The primary goal of this first trial is to establish the safety of the procedure. Thus far, none of the patients has suffered side effects. Five more patients will be recruited into the study.