A critical role for miR-184 in the fate determination of oligodendrocytes

The therapeutic potential of microRNAs to ameliorate spinal cord injury by regulating oligodendrocyte progenitor cells and remyelination

Spinal cord injury (SCI) can cause loss of sensory and motor function below the level of injury, posing a serious threat to human health and quality of life. One significant characteristic feature of pathological changes following injury in the nervous system is demyelination, which partially contributes to the long-term deficits in neural function after injury. The remyelination in the central nervous system (CNS) is mainly mediated by oligodendrocyte progenitor cells (OPCs). Numerous complex intracellular signaling and transcriptional factors regulate the differentiation process from OPCs to mature oligodendrocytes (OLs) and myelination. Studies have shown the importance of microRNA (miRNA) in regulating OPC functions. In this review, we focus on the demyelination and remyelination after SCI, and summarize the progress of miRNAs on OPC functions and remyelination, which might provide a potential therapeutic target for SCI treatments.

MiR-184-5p represses neuropathic pain by regulating CCL1/CCR8 signaling interplay in the spinal cord in diabetic mice

BACKGROUND

Diabetic neuropathic pain (DNP) is a serious complication for diabetic patients involving nervous system. MicroRNAs (miRNAs) are small-noncoding RNAs which are dysregulated in neuropathic pain, and might be critical molecules for pain treatment. Our previous study has shown miR-184-5p was significantly downregulated in DNP. Therefore, the mechanism of miR-184-5p in DNP was investigated in this study.

METHODS

A DNP model was established through streptozotocin (STZ). The pharmacological tools were injected intrathecally, and pain behavior was evaluated by paw withdrawal mechanical thresholds (PWMTs). Bioinformatics analysis, Dual-luciferase reporter assay and fluorescence-in-situ-hybridization (FISH) were used to seek and confirm the potential target genes of miR-184-5p. The expression of relative genes and proteins was analyzed by quantitative reverse transcriptase real-time PCR (qPCR) and western blotting.

RESULTS

MiR-184-5p expression was down-regulated in spinal dorsal on days 7 and 14 after STZ, while intrathecal administration of miR-184-5p agomir attenuates neuropathic pain induced by DNP and intrathecal miR-184-5p antagomir induces pain behaviors in naïve mice. Chemokine CC motif ligand 1 (CCL1) was found to be a potential target of miR-184-5p and the protein expression of CCL1 and the mRNA expression of CCR8 were up-regulated in spinal dorsal on days 7 and 14 after STZ. The luciferase reporter assay and FISH demonstrated that CCL1 is a direct target of miR-184-5p. MiR-184-5p overexpression attenuated the expression of CCL1/CCR8 in DNP; intrathecal miR-184-5p antagomir increased the expression of CCL1/CCR8 in spinal dorsal of naïve mice.

CONCLUSION

This research illustrates that miR-184-5p alleviates DNP through the inhibition of CCL1/CCR8 signaling expression.

microRNA-184 in the landscape of human malignancies: a review to roles and clinical significance

MicroRNAs (miRNAs) are a class of non-coding RNAs (ncRNAs) with a short length of 19-22 nucleotides. miRNAs are posttranscriptional regulators of gene expression involved in various biological processes like cell growth, apoptosis, and angiogenesis. miR-184 is a well-studied miRNA, for which most studies report its downregulation in cancer cells and tissues and experiments support its role as a tumor suppressor inhibiting malignant biological behaviors of cancer cells in vitro and in vivo. To exert its functions, miR-184 affects some signaling pathways involved in tumorigenesis like Wnt and β-catenin, and AKT/mTORC1 pathway, oncogenic factors (e.g., c-Myc) or apoptotic proteins, such as Bcl-2. Interestingly, clinical investigations have shown miR-184 with good performance as a prognostic/diagnostic biomarker for various cancers. Additionally, exogenous miR-184 in cell and xenograft animal studies suggest it as a therapeutic anticancer target. In this review, we outline the studies that evaluated the roles of miR-184 in tumorigenesis as well as its clinical significance.

Limiting viral replication in hepatocytes alters Rift Valley fever virus disease manifestations

Rift Valley fever virus (RVFV) causes mild to severe disease in humans and livestock. Outbreaks of RVFV have been reported throughout Africa and have spread outside Africa since 2000, calling for urgent worldwide attention to this emerging virus. RVFV directly infects the liver, and elevated transaminases are a hallmark of severe RVFV infection. However, the specific contribution of viral replication in hepatocytes to pathogenesis of RVFV remains undefined. To address this, we generated a recombinant miRNA-targeted virus, RVFVmiR-122, to limit hepatocellular replication. MicroRNAs are evolutionarily conserved non-coding RNAs that regulate mRNA expression by targeting them for degradation. RVFVmiR-122 includes an insertion of four target sequences of the liver-specific miR-122. In contrast to control RVFVmiR-184, which contains four target sequences of mosquito-specific miR-184, RVFVmiR-122 has restricted replication in vitro in primary mouse hepatocytes. RVFVmiR-122-infected C57BL/6 mice survived acute hepatitis and instead developed late-onset encephalitis. This difference in clinical outcome was eliminated in Mir-122 KO mice, confirming the specificity of the finding. Interestingly, C57BL/6 mice infected with higher doses of RVFVmiR-122 had a higher survival rate which was correlated with faster clearance of virus from the liver, suggesting a role for activation of host immunity in the phenotype. Together, our data demonstrate that miR-122 can specifically restrict the replication of RVFVmiR-122 in liver tissue both in vitro and in vivo, and this restriction alters the clinical course of disease following RVFVmiR-122 infection. IMPORTANCE Rift Valley fever virus (RVFV) is a hemorrhagic fever virus that causes outbreaks in humans and livestock throughout Africa and has spread to continents outside Africa since 2000. However, no commercial vaccine or treatment is currently available for human use against RVFV. Although the liver has been demonstrated as a key target of RVFV, the contribution of viral replication in hepatocytes to overall RVFV pathogenesis is less well defined. In this study we addressed this question by using a recombinant miRNA-targeted virus with restricted replication in hepatocytes. We gained a better understanding of how this individual cell type contributes to the development of disease caused by RVFV. Techniques used in this study provide an innovative tool to the RVFV field that could be applied to study the consequences of limited RVFV replication in other target cells.

Phenome-wide association study of loci harboring de novo tandem repeat mutations in UK Biobank exomes

When present in coding regions, tandem repeats (TRs) may have large effects on protein structure and function contributing to health and disease. We use a family-based design to identify de novo TRs and assess their impact at the population level in 148,607 European ancestry participants from the UK Biobank. The 427 loci with de novo TR mutations are enriched for targets of microRNA-184 (21.1-fold, P = 4.30 × 10^-5, FDR = 9.50 × 10^-3). There are 123 TR-phenotype associations with posterior probabilities > 0.95. These relate to body structure, cognition, and cardiovascular, metabolic, psychiatric, and respiratory outcomes. We report several loci with large likely causal effects on tissue microstructure, including the FAN1-[TG]_N and carotid intima-media thickness (mean thickness: beta = 5.22, P = 1.22 × 10^-6, FDR = 0.004; maximum thickness: beta = 6.44, P = 1.12 × 10^-6, FDR = 0.004). Two exonic repeats FNBP4-[GGT]_N and BTN2A1-[CCT]_N alter protein structure. In this work, we contribute clear and testable hypotheses of dose-dependent TR implications linking genetic variation and protein structure with health and disease outcomes.

MicroRNAs in oligodendrocyte development and remyelination

Oligodendrocytes are the glial cells responsible for the formation of myelin around axons of the central nervous system (CNS). Myelin is an insulating layer that allows electrical impulses to transmit quickly and efficiently along neurons. If myelin is damaged, as in chronic demyelinating disorders such as multiple sclerosis (MS), these impulses slow down. Remyelination by oligodendrocytes is often ineffective in MS, in part because of the failure of oligodendrocyte precursor cells (OPCs) to differentiate into mature, myelinating oligodendrocytes. The process of oligodendrocyte differentiation is tightly controlled by several regulatory networks involving transcription factors, intracellular signaling pathways, and extrinsic cues. Understanding the factors that regulate oligodendrocyte development is essential for the discovery of new therapeutic strategies capable of enhancing remyelination. Over the past decade, microRNAs (miRNAs) have emerged as key regulators of oligodendrocyte development, exerting effects on cell specification, proliferation, differentiation, and myelination. This article will review the role of miRNAs on oligodendrocyte biology and discuss their potential as promising therapeutic tools for remyelination.

Bu Shen Yi Sui Capsules Promote Remyelination by Regulating MicroRNA-219 and MicroRNA-338 in Exosomes to Promote Oligodendrocyte Precursor Cell Differentiation

Remyelination is a refractory feature of demyelinating diseases such as multiple sclerosis (MS). Studies have shown that promoting oligodendrocyte precursor cell (OPC) differentiation, which cannot be achieved by currently available therapeutic agents, is the key to enhancing remyelination. Bu Shen Yi Sui capsule (BSYSC) is a traditional Chinese herbal medicine over many years of clinical practice. We have found that BSYSC can effectively treat MS. In this study, the effects of BSYSC in promoting OPCs differentiation and remyelination were assessed using an experimental autoimmune encephalomyelitis (EAE) model in vivo and cultured OPCs in vitro. The results showed that BSYSC reduced clinical function scores and increased neuroprotection. The expression of platelet-derived growth factor receptor α (PDGFR-α) was decreased and the level of 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) was increased in the brains and spinal cords of mice as well as in OPCs after treatment with BSYSC. We further found that BSYSC elevated the expression of miR-219 or miR-338 in the serum exosomes of mice with EAE, thereby suppressing the expression of Sox6, Lingo1, and Hes5, which negatively regulate OPCs differentiation. Therefore, serum exosomes of BSYSC-treated mice (exos-BSYSC) were extracted and administered to OPCs in which miR-219 or miR-338 expression was knocked down by adenovirus, and the results showed that Sox6, Lingo1, and Hes5 expression was downregulated, MBP expression was upregulated, OPCs differentiation was increased, and the ability of OPCs to wrap around neuronal axons was improved. In conclusion, BSYSC may exert clinically relevant effects by regulating microRNA (miR) levels in exosomes and thus promoting the differentiation and maturation of OPCs.

Radiation-induced neuropathological changes in the oligodendrocyte lineage with relevant clinical manifestations and therapeutic strategies

PURPOSE

With technological advancements in radiation therapy for tumors of the central nervous system (CNS), high doses of ionizing radiation can be delivered to the tumors with improved accuracy. Despite the reduction of ionizing radiation-induced toxicity to surrounding tissues of the CNS, a wide array of side effects still occurs, particularly late-delayed changes. These alterations, such as white matter damages and neurocognitive impairments, are often debilitative and untreatable, significantly affecting the quality of life of these patients, especially children. Oligodendrocytes, a major class of glial cells, have been identified to be one of the targets of radiation toxicity and are recognized be involved in late-delayed radiation-induced neuropathological changes. These cells are responsible for forming the myelin sheaths that surround and insulate axons within the CNS. Here, the effects of ionizing radiation on the oligodendrocyte lineage as well as the common clinical manifestations resulting from radiation-induced damage to oligodendrocytes will be discussed. Potential prophylactic and therapeutic strategies against radiation-induced oligodendrocyte damage will also be considered.

CONCLUSION

Oligodendrocytes and oligodendrocyte progenitor cells (OPCs) are radiosensitive cells of the CNS. Here, general responses of these cells to radiation exposure have been outlined. However, several findings have not been consistent across various studies. For instance, cognitive decline in irradiated animals was observed to be accompanied by obvious demyelination or white matter changes in several studies but not in others. Hence, further studies have to be conducted to elucidate the level of contribution of the oligodendrocyte lineage to the development of late-delayed effects of radiation exposure, as well as to classify the dose and brain region-specific responses of the oligodendrocyte lineage to radiation. Several potential therapeutic approaches against late-delayed changes have been discussed, such as the transplantation of OPCs into irradiated regions and implementation of exercise. Many of these approaches show promising results. Further elucidation of the mechanisms involved in radiation-induced death of oligodendrocytes and OPCs would certainly aid in the development of novel protective and therapeutic strategies against the late-delayed effects of radiation.

Functions of noncoding RNAs in glial development

Glia are widely distributed in the central nervous system and are closely related to cell metabolism, signal transduction, support, cell migration, and other nervous system development processes and functions. Glial development is complex and essential, including the processes of proliferation, differentiation, and migration, and requires precise regulatory networks. Noncoding RNAs (ncRNAs) can be deeply involved in glial development through gene regulation. Here, we review the regulatory roles of ncRNAs in glial development. We briefly describe the classification and functions of noncoding RNAs and focus on microRNAs (miRNAs) and long ncRNAs (lncRNAs), which have been reported to participate extensively during glial formation. The highlight of this summary is that miRNAs and lncRNAs can participate in and regulate the signaling pathways of glial development. The review not only describes how noncoding RNAs participate in nervous system development but also explains the processes of glial development, providing a foundation for subsequent studies on glial development and new insights into the pathogeneses of related neurological diseases.

MicroRNAs, Multiple Sclerosis, and Depression

Multiple sclerosis (MS) is a chronic disease of the central nervous system that affects the brain and spinal cord. There are several disease courses in MS including relapsing–remitting MS (RRMS), primary progressive MS (PPMS), and secondary progressive MS (SPMS). Up to 50% of MS patients experience depressive disorders. Major depression (MD) is a serious comorbidity of MS. Many dysfunctions including neuroinflammation, peripheral inflammation, gut dysbiosis, chronic oxidative and nitrosative stress, and neuroendocrine and mitochondrial abnormalities may contribute to the comorbidity between MS and MD. In addition to these actions, medical treatment and microRNA (miRNA) regulation may also be involved in the mechanisms of the comorbidity between MS and MD. In the study, I review many common miRNA biomarkers for both diseases. These common miRNA biomarkers may help further explore the association between MS and MD.

SOX Transcription Factors as Important Regulators of Neuronal and Glial Differentiation During Nervous System Development and Adult Neurogenesis

The SOX proteins belong to the superfamily of transcription factors (TFs) that display properties of both classical TFs and architectural components of chromatin. Since the cloning of the Sox/SOX genes, remarkable progress has been made in illuminating their roles as key players in the regulation of multiple developmental and physiological processes. SOX TFs govern diverse cellular processes during development, such as maintaining the pluripotency of stem cells, cell proliferation, cell fate decisions/germ layer formation as well as terminal cell differentiation into tissues and organs. However, their roles are not limited to development since SOX proteins influence survival, regeneration, cell death and control homeostasis in adult tissues. This review summarized current knowledge of the roles of SOX proteins in control of central nervous system development. Some SOX TFs suspend neural progenitors in proliferative, stem-like state and prevent their differentiation. SOX proteins function as pioneer factors that occupy silenced target genes and keep them in a poised state for activation at subsequent stages of differentiation. At appropriate stage of development, SOX members that maintain stemness are down-regulated in cells that are competent to differentiate, while other SOX members take over their functions and govern the process of differentiation. Distinct SOX members determine down-stream processes of neuronal and glial differentiation. Thus, sequentially acting SOX TFs orchestrate neural lineage development defining neuronal and glial phenotypes. In line with their crucial roles in the nervous system development, deregulation of specific SOX proteins activities is associated with neurodevelopmental disorders (NDDs). The overview of the current knowledge about the link between SOX gene variants and NDDs is presented. We outline the roles of SOX TFs in adult neurogenesis and brain homeostasis and discuss whether impaired adult neurogenesis, detected in neurodegenerative diseases, could be associated with deregulation of SOX proteins activities. We present the current data regarding the interaction between SOX proteins and signaling pathways and microRNAs that play roles in nervous system development. Finally, future research directions that will improve the knowledge about distinct and various roles of SOX TFs in health and diseases are presented and discussed.

Mir-184 Contributes to Brain Injury Through Targeting PPAP2B Following Ischemic Stroke in Male Rats

Our previous study revealed that miR-184 expression is significantly altered in the brain following ischemic stroke in rats. However, it is unknown whether this alteration in miR-184 expression contributes to brain injury after ischemic stroke. Here, we aim to address the potential of miR-184 to impact nerve injury following ischemia and reperfusion. Rats received ICV injection of miR-184 adenovirus or empty vector and were subjected to right middle cerebral artery occlusion (MCAO) to establish an ischemic stroke model. We cultured SH-SY5Y cells under oxygen-glucose deprivation/reoxygenation (OGD/R) and transfected them with miR-184 lentivirus to explore the primary mechanisms. To evaluate miR-184 expression, neurological function deficits, the cerebral infarct volume, cell viability, and apoptosis, qRT-PCR analysis of miR-184 expression, the modified neurological severity score (mNSS) system, TTC staining, the CCK-8 assay, flow cytometry, and dual-luciferase reporter assays were utilized. We found that miR-184 expression was downregulated and that the cerebral infarct volume and mNSSs were increased following ischemic stroke; however, increasing the level of miR-184 alleviated brain damage. Overexpression of miR-184 resulted in increased viability and reduced apoptosis of SH-SY5Y cells following OGD/R in vitro. We identified the phosphatidic acid phosphatase type 2B (PPAP2B) gene as a direct target gene of miR-184. In summary, our results reveal that attenuation of miR-184 levels in ischemic stroke contributes to ischemic injury through targeting PPAP2B mRNA-mediated apoptosis, which may be a promising therapeutic target for ischemic stroke.

The Role of MicroRNAs in Repair Processes in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disorder characterised by demyelination of central nervous system neurons with subsequent damage, cell death and disability. While mechanisms exist in the CNS to repair this damage, they are disrupted in MS and currently there are no treatments to address this deficit. In recent years, increasing attention has been paid to the influence of the small, non-coding RNA molecules, microRNAs (miRNAs), in autoimmune disorders, including MS. In this review, we examine the role of miRNAs in remyelination in the different cell types that contribute to MS. We focus on key miRNAs that have a central role in mediating the repair process, along with several more that play either secondary or inhibitory roles in one or more aspects. Finally, we consider the current state of miRNAs as therapeutic targets in MS, acknowledging current challenges and potential strategies to overcome them in developing effective novel therapeutics to enhance repair mechanisms in MS.