The effects of epidural application of allografted nucleus pulposus in rats on cytokine expression, limb withdrawal and nerve root discharge

Abstract
This study investigated cytokine expression, behavioral and neurophysiologic changes in Lewis rats whose lumbar nerve roots were exposed to nucleus pulposus (NP). Allografted NP or fat was implanted over the left L5 nerve root. Sham rats had no NP or fat implantation. Control rats had no surgery. Rats were allowed to survive for 7 days and were tested daily for hind-paw mechanical and thermal withdrawal response (TWR). Granulation tissue was processed by immunohistochemistry for cytokines—interleukin 1 beta (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor (TNF). Neurophysiological response from the L5 nerve roots was also characterized after 7 days. Significant staining density for IL-1β, IL-6 and TNF was observed in NP granulation tissue compared with fat and sham (pp<0.05) but not higher than fat and sham rats. These results support the inflammatory nature of NP but offer limited support to NP-mediated thermal behavioral changes.