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.