MiR-34a is differentially expressed in dorsal root ganglia in a rat model of chronic neuropathic pain

Abstract

IntroductionRecent evidence shows that numerous microRNAs (miRNAs) regulate pain-related genes in chronic pain. The aim of the present study was to further explore the regulation of miRNAs and their effect on the expression of pain-associated target genes in experimental neuropathic pain. MethodsMale Wistar rats underwent chronic constriction injury (CCI) of the sciatic nerve or Sham procedure. After assessment of mechanical allodynia, the ipsilateral dorsal root ganglia (DRG) were harvested. MiRNA expression levels were analysed with Agilent microRNA microarrays and real time quantitative PCR. An interaction between miRNAs and pain-relevant genes was confirmed by luciferase assays. Western Blot analysis and ELISA were performed to evaluate protein expression, respectively. ResultsMechanical allodynia developed within 6 days after CCI. MiRNA-arrays revealed the differential expression of 49 miRNAs after 4 h, of 3 miRNAs after 1 d, of 26 miRNAs after 6 d and of 28 miRNAs after 12 d in the CCI group versus Sham. Time-dependent down regulation of miR-34a was verified by qPCR. Bioinformatic prediction revealed an interaction with several pain-relevant targets including voltage-gated sodium channel β2 subunit (SCN2B) and vesicle-associated membrane protein 2 (VAMP-2), both of which were subsequently confirmed by luciferase assay. VAMP-2 expression was statistically significantly increased 12 d after CCI. A non-significant upregulation of SCN2B in the DRG after CCI was confirmed by ELISA. DiscussionPeripheral mononeuropathic pain in rats was associated with distinct alterations of miRNA expression in the ipsilateral DRG. Notably, miR-34a was time-dependently down regulated. We validated SCN2B and VAMP-2 as new targets of miR-34a. While SCN2B expression was only marginally altered, VAMP-2 expression was increased. The present study underlines that the induction and maintenance of neuropathic pain is accompanied by expression changes of miRNAs in the peripheral nervous system, adding several previously unreported miRNAs, including miR-34a.