Biomarkers Mapping in a Neuropathic Pain Mice Model with Sciatic Nerve Chronic Constriction Injury (CCI).

Introduction Neuropathic pain (NP) is an continuous pain caused by injury to the somatosensory system, is persistent and is refractory to analgesics. Common causes of NP include post herpetic neuralgia, diabetic neuropathy, cutting or compression of nerve. In this work a surgical mice model with a sciatic nerve chronic constriction injury (CCI) was used as a NP model. This CCI model involves both inflammatory and neuropathic components (1). The aim of this work was to identify significantly altered proteins in the blood of CCI operated mice in order to find possible predictive biomarkers of NP. Methodology To perform the CCI, the right sciatic nerve of the mice was exposed at the level of the mid-thigh. In CCI operated mice, three ligatures were loosely tied around the nerve, whereas in sham-operated controls, the sciatic nerve was exposed but not ligated. One week after surgery, the blood from the two groups was collected and the protein expression patterns was analyzed by a two-dimensional gel electrophoresis (2DE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to sequence protein signals. Results Results showed seven differentially expressed protein spots: five isoforms of haptoglobin, expressed only in the CCI operated mice group, transthyretin and apolipoprotein A-IV expressed mainly in the control group (sham-operated mice). Haptoglobin is an acute phase protein strongly associated with inflammation and is overexpressed during neuron damage. The five isoforms of haptoglobin observed in CCI operated mice serum are likely due to post-translational modifications. Conclusions This preliminary study provided data for potential biomarkers of neuropathic pain that can result useful for future neuropathic pain drug development.