Is There Any Relationship between Plasma IL-6 and TNF-α Levels and Lumbar Disc Degeneration? A Retrospective Single-Center Study

Abstract

Intervertebral disc degeneration (IDD) is one of the most common degenerative diseases all over the world. A growing number of studies have proved that large amounts of cytokines are produced during the development of IDD, and the inflammatory responses induced by these cytokines aggravate the occurrence and development of the disc degeneration. In this retrospective single-center study, a total of 182 lumbar spine cases were retrospectively reviewed between July 2020 and October 2021. An appropriate cutoff value was found for discriminating severity of IDD by William rank-sum test and locally weighted scatterplot smoothing algorithm. The cumulative grade was also calculated by summing Pfirrmann grades for all lumbar spine intervertebral discs. It was found that high-score group (total $\text{score}>18$ ) plasma interleukin-6 (IL-6) concentration was significantly higher than that of the low-score group (total $\text{score}\le 18$ ) ( $9.6\pm 1.75$ vs. $5.40\pm 0.61$  pg/ml, $p=0.002$ ), tumor necrosis factor-α (TNF-α) following the same trend ( $5.27\pm 1.48$ vs. $2.97\pm 0.23$ , $p=0.006$ ), which was most pronounced in the upper lumbar intervertebral discs (L1-3). In the entire sample, preoperative IL-6 concentration was significantly higher than that of the postoperation ( $p<0.001$ ), while the TNF-α was the opposite ( $p=0.039$ ). It was also found that there were significant differences in the two groups with respect to age and hypertension ( $p<0.001$ and $p=0.037$ ). In conclusion, this study preliminarily indicated the relationship between IL-6 and TNF-α and the severity of lumbar disc degeneration.