Interleukin-6 protein expression is more important than interleukin-6 mRNA levels in assessing surgical invasiveness

Interleukin-6 (IL-6) protein has been recognized as a sensitive marker of surgical stress response. However, little is known about the clinical significance of IL-6 mRNA levels as a marker of surgical stress. This study aims to examine the role of IL-6 mRNA expression in comparing the tissue invasiveness of microendoscopic discectomy (MED) and open discectomy (OD).

Twenty-three consecutive patients were randomly selected to undergo either MED or OD. The total RNA was extracted from the peripheral whole blood of patients at pre-op and at 1, 2, 4, 8, 12 h post-op. The real-time reverse transcription polymerase chain reaction (RT-PCR) using the SYBR Green I fluorescence dye and the 2(-DeltaDeltaCt) method was adopted to measure the IL-6 gene expression.

The quantitative changes of IL-6 mRNA expression in MED and OD patients at different times post-op differed significantly, P = 0.04. Experimental results indicate that the changes in IL-6 mRNA expression in OD and MED groups varied significantly at 1 h, 12 h post-op, 10.26-fold versus 4.42-fold and 52.15-fold versus 26.78-fold increase, respectively. Although IL-6 mRNA expression demonstrated an earlier difference than protein levels at 1 h post-op, IL-6 mRNA levels were found to be significantly affected after surgical procedures. Furthermore, compared with our enzyme-linked immunosorbent assay data, no significant correlation existed between IL-6 mRNA and protein levels at any post-op time interval.

We conclude that IL-6 mRNA expression using RT-PCR to extract the total RNA from a patient's peripheral whole blood is more sensitive than protein levels but can be significantly affected by surgical procedures. The enzyme-linked immunosorbent assay data on IL-6 protein expression are more consistent and significant than IL-6 mRNA levels in comparing tissue invasiveness between MED and OD.