By stimulating nerve cells in laboratory rats at the time of the injury and then again one week later, the scientists were able to increase the growth capacity of nerve cells and to sustain that capacity. Both factors are critical for nerve regeneration.
The study, reported in the November 15 issue of the Proceedings of the National Academy of Sciences, builds on earlier findings in which the researchers were able to induce cell growth by manipulating the nervous system before a spinal cord injury, but not after.
Key to the research is an important difference in the properties of the nerve fibers of the central nervous system (CNS), which consists of the brain and spinal cord, and those of the peripheral nervous system (PNS), which is the network of nerve fibers that extends throughout the body.
Nerve cells normally grow when they are young and stop when they are mature. When an injury occurs in CNS cells, the cells are unable to regenerate on their own. In PNS cells, however, an injury can stimulate the cells to regrow. PNS nerve regeneration makes it possible for severed limbs to be surgically reattached to the body and continue to grow and regain function.
Regeneration occurs because PNS cell bodies are sensitive to damage to their nerve processes, and they react by sending out a signal that triggers the nerve fibers to regrow, explains Allan Basbaum, PhD, senior study author and chair of the UCSF Department of Anatomy. "Apparently this communication doesn't take place within the CNS."
Scientists do not yet know the biochemical cause for the difference, he adds.
The traditional scientific approach in efforts to enhance CNS regeneration is to manipulate the biochemical environment of the cells at the site of the spinal cord injury, according
Contact: Linda Gebroe
University of California - San Francisco