title: Interleukin-6 protein expression is more important than interleukin-6 mRNA levels in assessing surgical invasiveness.
abstract: BACKGROUND
  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).
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Orthopedic Surgery, Chang Gung Memorial Hospital at Chia-Yi, Chia-Yi, Taiwan. tjhuang@adm.cgmh.org.tw
authors.forename: Tsung-Jen
authors.initials: TJ
authors.lastname: Huang
authors.forename: Yen-Yao
authors.initials: YY
authors.lastname: Li
authors.forename: Yi-Jan
authors.initials: YJ
authors.lastname: Weng
authors.forename: Chin-Chang
authors.initials: CC
authors.lastname: Cheng
authors.forename: Robert Wen-Wei
authors.initials: RW
authors.lastname: Hsu
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D017586:Diskectomy / Q000009:adverse effects* / Q000379:methods*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects*; D016133:Polymerase Chain Reaction; D011183:Postoperative Complications / Q000097:blood; D012333:RNA, Messenger / Q000097:blood* / Q000378:metabolism; D012680:Sensitivity and Specificity; D013312:Stress, Physiological / Q000097:blood / Q000209:etiology
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D012333:RNA, Messenger