Expression of spinal cord microRNAs in a rat model of chronic neuropathic pain.

Neuropathic pain is accompanied by significant alterations of gene expression patterns in the somatosensory nervous system. The spinal cord is particularly prone to neuroplastic changes. Since the expression of microRNAs (miRNAs) has been linked to numerous pathophysiological processes, a contribution of miRNAs to the maladaptive plasticity of the spinal cord in neuropathic pain is possible. Aim of the present study therefore was to characterize the specific expression pattern of miRNAs in the rat spinal cord. Furthermore, we evaluated the time-dependent changes in expression patterns of spinal miRNAs in the chronic constriction injury (CCI) model of neuropathic pain in rats. Results from miRNA microarrays revealed a distinct expression pattern of miRNAs in the rat spinal cord. MiRNAs-494, -720, -690 and -668 showed the highest signal intensities. Members of the let-7 family as well as miR-124 belong to the group of the most highly expressed miRNAs. Induction of neuropathic pain by CCI did not lead to relevant differences in spinal miRNA expression levels compared to sham-operated animals at any studied time point. Therefore, modulation of miRNAs does not seem to contribute significantly to the changes in gene expression that cause neural plasticity in the spinal cord in this model of chronic neuropathic pain.