BackgroundMicroRNAs (miRNAs) are involved in the neuroplastic changes which induce and maintain neuropathic pain. However, it is unknown whether nerve injury leads to altered miRNA expression and modulation of pain relevant target gene expression within peripheral nerves. In the present study, expression profiles of miR-1 and the pain-relevant targets, brain derived neurotrophic factor (BDNF) and Connexin 43 (Cx43), were studied in peripheral neuropathic pain, which was induced by chronic constriction injury (CCI) of the sciatic nerve in rats. The expression of miR-1 was investigated in the sciatic nerve, dorsal root ganglion (DRG) and the ipsilateral spinal cord by qPCR. Changes of BDNF and Cx43 expression patterns were studied using qPCR, Western blot analysis, ELISA and immunohistochemistry.ResultsIn sciatic nerves of naïve rats, expression levels of miR-1 were more than twice as high as in DRG and spinal cord. In neuropathic rats, CCI lead to a time-dependent downregulation of miR-1 in the sciatic nerve but not in DRG and spinal cord. Likewise, protein expression of the miR-1 targets BDNF and Cx43 was upregulated in the sciatic nerve and DRG after CCI. Immunohistochemical staining revealed an endoneural abundancy of Cx43 in injured sciatic nerves which was absent after Sham operation.ConclusionsThis study demonstrates that CCI leads to a regulation of miRNAs (miR-1) in the peripheral nervous system. This regulation is associated with alterations in the expression and localization of the miR-1 dependent pain-relevant proteins BDNF and Cx43. Further studies will have to explore the function of miRNAs in the context of neuropathic pain in the peripheral nervous system.

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This audit has inherent weakness including a small sample size and lack of a control group. However, this report highlights the advantages of ultrasound guidance in enhancing the accuracy and safety profile of a minimally neuro-destructive technique. Further randomized controlled trials are needed to confirm the efficacy of this treatment modality.

Remote ischemic preconditioning (RIPC) is an easily applicable method for protecting the heart against a subsequent ischemia and reperfusion (I/R) injury. However, the exact molecular mechanisms underlying RIPC are unknown. We examined the involvement of microRNAs (miRNAs) and in particular the expression of miRNA-1 (miR-1) in RIPC and myocardial ischemia. Remote ischemic preconditioning was conducted by four cycles of 5-min bilateral hind-limb ischemia in male Wistar rats. Cardiac ischemia was induced by ligation of the left anterior descending coronary artery for 35 min followed by 2 or 6 h of reperfusion. MicroRNA expression was analyzed by Taqman miRNA arrays and quantitative polymerase chain reaction assays. Luciferase assays were performed to validate the miR-1 target gene brain-derived neurotrophic factor (BDNF). Brain-derived neurotrophic factor mRNA and protein levels were analyzed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Remote ischemic preconditioning led to a differential expression of miRNAs. The most abundant cardiac miRNA, miR-1, was downregulated by RIPC without following ischemia as well as after I/R and RIPC followed by I/R after 2 h of reperfusion. After 6 h of reperfusion, RIPC led to an upregulation of miR-1, whereas ischemia had no effect on miR-1 expression. Luciferase assays confirmed the interaction of miR-1 with BDNF, a protein that has been shown to exert cardioprotective effects. Brain-derived neurotrophic factor protein levels in rat hearts measured by enzyme-linked immunosorbent assay were not significantly altered after 2 or 6 h of reperfusion in all intervention groups. Remote ischemic preconditioning leads to changes in the expression levels of the most abundant cardiac miRNA, miR-1. MicroRNA 1 levels did not correlate with protein levels of BDNF, a known miR-1 target, in vivo. Further studies are needed to explore the biological significance of changes in miR-1 expression levels and the potential interaction with BDNF in RIPC-induced cardioprotection.