Comparative analysis of serum proteomes: Identification of proteins associated with sciatica due to lumbar intervertebral disc herniation.

Lumbar intervertebral disc herniation (LDH) is one of the most common orthopedic conditions that can cause lower back pain and sciatica. However, the pathogenesis of LDH is poorly understood. The aim of the present study was to use proteomic analysis of blood samples to establish whether there are serum proteins associated with LDH, which may be useful in elucidating LDH pathogenesis. The ultimate aim was to develop a simple technique for the diagnosis of LDH based on the blood samples of patients with sciatica. The study used comparative analysis of serum proteomes associated with sciatica due to LDH. A total of 30 LDH patients with sciatica, receiving treatment between August and December 2007, were selected as the experimental group (or LDH group). A total of 2 ml of blood was obtained from each of the 30 patients in the LDH group and from 30 healthy volunteers, who constituted the control group. Two-dimensional electrophoresis of the blood samples was conducted, distinct protein spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and proteins associated with LDH were detected. An enzyme-linked immunosorbent assay (ELISA) was developed to screen for the LDH proteins and was tested on the sera of a second test and control group that included 10 patients with LDH and 10 healthy subjects, respectively. Based on signal intensity, the expression levels of 6 proteins on the dielectrophoretogram were found to be significantly associated with LDH. The identities of the LDH proteins were upregulated apolipoprotein-L1 (APO-L1) and two types of serum albumin precursors, and downregulated apolipoprotein M (APO-M), tetranectin (TN) and immunoglobulin light chain (IGL). Further ELISA experiments confirmed that there were increased serum levels of 4 out of the 6 proteins in patients with sciatica due to LDH, which was statistically different compared to the healthy subjects. In conclusion, these results suggest that serum APO-L1, TN, APO-M and IGL may serve as LDH biomarkers.