After spinal cord injury, axons try to cross the injury site and reconnect with other cells but are stymied by scarring that forms after the injury. Previous studies suggested their movements are blocked when the protein tyrosine phosphatase sigma (PTP sigma), an enzyme found in axons, interacts with chondroitin sulfate proteoglycans, a class of sugary proteins that fill the scars.
Bradley Lang, Ph.D. and his colleagues designed a drug called ISP to block the enzyme and facilitate the drug’s entry into the brain and spinal cord. Injections of the drug under the skin of paralyzed rats near the injury site partially restored axon growth and improved movements and bladder functions.