Effects of Degenerative Autologous Nucleus Pulposus on the Lumbar Sympathetic Trunk: Sympathetic Inflammation in Rats

Objective We have reported the presence of discogenic visceral pain secondary to anterior herniation of the lumbar disc. The aim of this study was to observe the inflammatory response of the sympathetic trunk to an autologous degenerative nucleus pulposus (NP) injection under fluoroscopy. Methods A total of 72 rats were used. In 24 rats, the autologous NP suspension was injected into the right sympathetic trunk. Next, food intake and body weight of each rat were monitored for 14 days. Fourteen days after the injection, the right lumbar sympathetic trunk was harvested for histological assessment, and protein levels of IL-1 β, IL-6, and TNF-α were quantified via ELISA. Results In the NP-treated group, endoneural hyperemia and intensive infiltration of inflammatory cells could be identified in sections of the sympathetic trunk by the hematoxylin and eosin (H&E) stain. Meanwhile, elevated concentrations of IL-1 β, IL-6, and TNF-α were determined in the sympathetic trunk of the NP group as compared to that of the naïve and control groups, which indicated the development of an inflammatory response. Furthermore, food intake and body weight of rats in the NP group decreased significantly. Conclusions The results indicated that an inflammatory response in the sympathetic trunk can be caused by anterior herniation of the lumbar disc, which can generate a sympathetic inflammatory pain response.