The role of tumor necrosis factor-α in apoptosis of dorsal root ganglion cells induced by herniated nucleus pulposus in rats

Study Design. The mechanisms of apoptosis underlying a characteristic tissue reaction at the surface of the dorsal root ganglion (DRG) exposed to nucleus pulposus were studied in rats with special reference to the role of tumor necrosis factor-alpha (TNF). Objective. To study the characteristic tissue reaction at the surface of the DRG exposed to nucleus pulposus with special reference to the role of TNF. Summary of Background Data. Nucleus pulposus cells are capable of producing TNF. Recently, local application of nucleus pulposus was shown to induce a characteristic tissue reaction at the DRG surface due to apoptosis. Methods. Recombinant TNF was applied to the DRG to mimic L4-L5 disc herniation in rats. The DRGs were resected 24 hours after surgery. Sections of the specimens were processed for immunohistochemistry using antisera to single-stranded DNA, Caspase 3, and TNF, and observed by light and electron microscopy. Results. Typical apoptotic changes of the cell nuclei were observed in the DRG after application of TNF. The presence of single-stranded DNA, Caspase 3, and TNF further confirmed the occurrence of DRG cell apoptosis. Conclusion. TNF seemed to play a key role in induction of apoptosis of DRG cells, which resembled that induced by application of nucleus pulposus.