Differential expression of microRNAs in dorsal root ganglia after sciatic nerve injury

The Role of microRNAs in Regulating Cancer Cell Response to Oxaliplatin-Containing Regimens

Oxaliplatin (cyclohexane-1,2-diamine; oxalate; platinum [2+]) is a third-generation chemotherapeutic drug with anticancer effects. Oxaliplatin has a role in the treatment of several cancers. It is one of the few drugs which can eliminate the neoplastic cells of colorectal cancer. Also, it has an influential role in breast cancer, lung cancer, bladder cancer, prostate cancer, and gastric cancer. Although oxaliplatin has many beneficial effects in cancer treatment, resistance to this drug is in the way to cure neoplastic cells and reduce treatment efficacy. microRNAs are a subtype of small noncoding RNAs with ∼22 nucleotides that exist among species. They have diverse roles in physiological processes, including cellular proliferation and cell death. Moreover, miRNAs have essential roles in resistance to cancer treatment and can strengthen sensitivity to chemotherapeutic drugs and regimens. In colorectal cancer, the co-treatment of oxaliplatin with anti-miR-19a can partially reverse the oxaliplatin resistance through the upregulation of phosphatase and tensin homolog (PTEN). Moreover, by preventing the spread of gastric cancer cells and downregulating glypican-3 (GPC3), MiR-4510 may modify immunosuppressive signals in the tumor microenvironment. Treatment with oxaliplatin may develop into a specialized therapeutic drug for patients with miR-4510 inhibition and glypican-3-expressing gastric cancer. Eventually, miR-122 upregulation or Wnt/β-catenin signaling suppression boosted the death of HCC cells and made them more sensitive to oxaliplatin. Herein, we have reviewed the role of microRNAs in regulating cancer cells' response to oxaliplatin, with particular attention to gastrointestinal cancers. We also discussed the role of these noncoding RNAs in the pathophysiology of oxaliplatin-induced neuropathic pain.

Spatiotemporal microRNA profile in peripheral nerve regeneration: miR-138 targets vimentin and inhibits Schwann cell migration and proliferation

While the peripheral nervous system has regenerative ability, restoration of sufficient function remains a challenge. Vimentin has been shown to be localized in axonal growth fronts and associated with nerve regeneration, including myelination, neuroplasticity, kinase signaling in nerve axoplasm, and cell migration; however, the mechanisms regulating its expression within Schwann cell (SC) remain unexplored. The aim of this study was to profile the spatial and temporal expression profile of microRNA (miRNA) in a regenerating rat sciatic nerve after transection, and explore the potential role of miR-138-5p targeting vimentin in SC proliferation and migration. A rat sciatic nerve transection model, utilizing a polyethylene nerve guide, was used to investigate miRNA expression at 7, 14, 30, 60, and 90 days during nerve regeneration. Relative levels of miRNA expression were determined using microarray analysis and subsequently validated with quantitative real-time polymerase chain reaction. In vitro assays were conducted with cultured Schwann cells transfected with miRNA mimics and assessed for migratory and proliferative potential. The top seven dysregulated miRNAs reported in this study have been implicated in cell migration elsewhere, and GO and KEGG analyses predicted activities essential to wound healing. Transfection of one of these, miRNA-138-5p, into SCs reduced cell migration and proliferation. miR-138-5p has been shown to directly target vimentin in cancer cells, and the luciferase assay performed here in rat Schwann cells confirmed it. These results detail a role of miR-138-5p in rat peripheral nerve regeneration and expand on reports of it as an important regulator in the peripheral nervous system.

Identification of miRNAs involved in DRG neurite outgrowth and their putative targets

Peripheral neurons regenerate their axons after injury. Transcriptional regulation by microRNAs (miRNAs) is one possible mechanism controlling regeneration. We profiled miRNA expression in mouse dorsal root ganglion neurons after a sciatic nerve crush, and identified 49 differentially expressed miRNAs. We evaluated the functional role of each miRNA using a phenotypic analysis approach. To predict the targets of the miRNAs we employed RNA-Sequencing and examined transcription at the isoform level. We identify thousands of differentially expressed isoforms and bioinformatically associate the miRNAs that modulate neurite growth with their putative target isoforms to outline a network of regulatory events underlying peripheral nerve regeneration. MiR-298, let-7a, and let-7f enhance neurite growth and target the majority of isoforms in the differentially expressed network.

Role of miR-145 in chronic constriction injury in rats

The present study aims to investigate the effects and underlying mechanisms of miRNA-145 (miR-145) in rat models of chronic constriction injury (CCI). Rats were randomly divided into control, sham, CCI, agomiRNA (agomiR)-normal control (NC) and agomiR-145 groups (n=25 in each group); in addition, 30 rats with CCI were divided into small hairpin (sh)RNA-NC and shRNA-ras responsive element binding protein 1 (RREB1) groups. Paw withdrawal thermal latency (PWTL) and paw withdrawal mechanical threshold (PWMT) were detected. Reverse transcription-quantitative polymerase chain reaction was used to detect miR-145 expression levels, and western blotting was performed to measure RREB1 and phosphorylated-protein kinase B (p-AKT) expression levels. In addition, a dual luciferase reporter assay was conducted to identify the target gene of miR-145. PWMT and PWTL were decreased in CCI rats and this decrease was alleviated by miR-145 injection. At 1, 3, 5 and 7 days after CCI, miR-145 expression level in the spinal cord tissue of rats in the CCI group was significantly decreased compared with 1 day before CCI (P<0.05). Compared with the CCI group, miR-145 expression level in the agomiR-145 group was significantly higher (P<0.05). In addition, expression levels of RREB1 and p-AKT were significantly increased in the CCI group and significantly decreased in the agomiR-145 group (P<0.05). Furthermore, knockdown of RREB1 expression by shRNA-RREB1 significantly increased values of PWMT and PWTL, decreased expression levels of RREB1 and p-AKT, and increased miR-145 expression levels (P<0.05). Further investigation demonstrated that miR-145 can bind with RREB1 mRNA. In conclusion, miR-145 may be involved in the development of CCI through regulating the expression of RREB1.

miR-148b-3p promotes migration of Schwann cells by targeting cullin-associated and neddylation-dissociated 1

MicroRNAs (miRNAs) are small, non-coding RNAs that negatively adjust gene expression in multifarious biological processes. However, the regulatory effects of miRNAs on Schwann cells remain poorly understood. Previous microarray analysis results have shown that miRNA expression is altered following sciatic nerve transaction, thereby affecting proliferation and migration of Schwann cells. This study investigated whether miR-148b-3p could regulate migration of Schwann cells by directly targeting cullin-associated and neddylation-dissociated 1 (Cand1). Up-regulated expression of miR-148b-3p promoted Schwann cell migration, whereas silencing of miR-148b-3p inhibited Schwann cell migration in vitro. Further experiments confirmed that Cand1 was a direct target of miR-148b-3p, and Cand1 knockdown reversed suppression of the miR-148b-3p inhibitor on Schwann cell migration. These results suggested that miR-148b-3p promoted migration of Schwann cells by directly targeting Cand1 in vitro.

The regulatory roles of non-coding RNAs in nerve injury and regeneration

Non-coding RNAs (ncRNAs), especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), have attracted much attention since their regulatory roles in diverse cell processes were recognized. Emerging studies demonstrate that many ncRNAs are differentially expressed after injury to the nervous system, significantly affecting nerve regeneration. In this review, we compile the miRNAs and lncRNAs that have been reported to be dysregulated following a variety of central and peripheral nerve injuries, including acquired brain injury, spinal cord injury, and peripheral nerve injury. We also list investigations on how these miRNAs and lncRNAs exert the regulatory actions in neurodegenerative and neuroregenerative processes through different mechanisms involving their interaction with target coding genes. We believe that comprehension of the expression profiles and the possible functions of ncRNAs during the processes of nerve injury and regeneration will help understand the molecular mechanisms responsible for post-nerve-injury changes, and may contribute to the potential use of ncRNAs as a diagnostic marker and therapeutic target for nerve injury.

microRNA and Pain

Pain is an important protective system that alerts organisms to actual or possible tissue damage. However, a variety of pathologies can lead to chronic pain that is no longer beneficial. Lesions or diseases of the somatosensory nervous system cause intractable neuropathic pain that occasionally lasts even after the original pathology subsides. Chronic inflammatory diseases like arthritis are also associated with severe pain. Because conventional analgesics such as non-steroidal anti-inflammatory drugs and opioids have limited efficacy and/or severe adverse events associated with long-term use, chronic pain remains a major problem in clinical practice. Recently, causal roles of microRNAs in chronic pain and their therapeutic potential have been emerging. microRNA expressions are altered not only at the primary origin of pain, but also along the somatosensory pathways. Notably, microRNA expressions are differentially affected depending on the causes of chronic pain. This chapter summarizes current insights into the roles of microRNAs in pain based on the underlying pathologies.