Loss of microRNA-124 expression in neurons in the peri-lesion area in mice with spinal cord injury

The role of apoptosis in spinal cord injury: a bibliometric analysis from 1994 to 2023

Background

Apoptosis after spinal cord injury (SCI) plays a pivotal role in the secondary injury mechanisms, which cause the ultimate neurologic insults. A better understanding of the molecular and cellular basis of apoptosis in SCI allows for improved glial and neuronal survival via the administrations of anti-apoptotic biomarkers. The knowledge structure, development trends, and research hotspots of apoptosis and SCI have not yet been systematically investigated.

Methods

Articles and reviews on apoptosis and SCI, published from 1st January 1994 to 1st Oct 2023, were retrieved from the Web of Science™. Bibliometrix in R was used to evaluate annual publications, countries, affiliations, authors, sources, documents, key words, and hot topics.

Results

A total of 3,359 publications in accordance with the criterions were obtained, which exhibited an ascending trend in annual publications. The most productive countries were the USA and China. Journal of Neurotrauma was the most impactive journal; Wenzhou Medical University was the most prolific affiliation; Cuzzocrea S was the most productive and influential author. "Apoptosis," "spinal-cord-injury," "expression," "activation," and "functional recovery" were the most frequent key words. Additionally, "transplantation," "mesenchymal stemness-cells," "therapies," "activation," "regeneration," "repair," "autophagy," "exosomes," "nlrp3 inflammasome," "neuroinflammation," and "knockdown" were the latest emerging key words, which may inform the hottest themes.

Conclusions

Apoptosis after SCI may cause the ultimate neurological damages. Development of novel treatments for secondary SCI mainly depends on a better understanding of apoptosis-related mechanisms in molecular and cellular levels. Such therapeutic interventions involve the application of anti-apoptotic agents, free radical scavengers, as well as anti-inflammatory drugs, which can be targeted to inhibit core events in cellular and molecular injury cascades pathway.

Circular RNA HIPK2 Promotes A1 Astrocyte Activation after Spinal Cord Injury through Autophagy and Endoplasmic Reticulum Stress by Modulating miR-124-3p-Mediated Smad2 Repression

Glial scarring formed by reactive astrocytes after spinal cord injury (SCI) is the primary obstacle to neuronal regeneration within the central nervous system, making them a promising target for SCI treatment. Our previous studies have demonstrated the positive impact of miR-124-3p on neuronal repair, but it remains unclear how miR-124-3p is involved in autophagy or ER stress in astrocyte activation. To answer this question, the expression of A1 astrocyte-related markers at the transcriptional and protein levels after SCI was checked in RNA-sequencing data and verified using quantitative polymerase chain reaction (qPCR) and Western blotting in vitro and in vivo. The potential interactions among circHIPK2, miR-124-3p, and Smad2 were analyzed and confirmed by bioinformatics analyses and a luciferase reporter assay. In the end, the role of miR-124-3p in autophagy, ER stress, and SCI was investigated by using Western blotting to measure key biomarkers (C3, LC3, and Chop) in the absence or presence of corresponding selective inhibitors (siRNA, 4-PBA, TG). As a result, SCI caused the increase of A1 astrocyte markers, in which the upregulated circHIPK2 directly targeted miR-124-3p, and the direct downregulating effect of Smad2 by miR-124-3p was abolished, while Agomir-124 treatment reversed this effect. Injury caused a significant change of markers for ER stress and autophagy through the circHIPK2/miR-124-3p/Smad2 pathway, which might activate the A1 phenotype, and ER stress might promote autophagy in astrocytes. In conclusion, circHIPK2 may play a functional role in sequestering miR-124-3p and facilitating the activation of A1 astrocytes through regulating Smad2-mediated downstream autophagy and ER stress pathways, providing a new perspective on potential targets for functional recovery after SCI.

Hydralazine plays an immunomodulation role of pro-regeneration in a mouse model of spinal cord injury

Spinal cord injury (SCI) results in severe motor and sensory dysfunction with no effective therapy. Spinal cord debris (sp) from injured spinal cord evokes secondary SCI continuously. We and other researchers have previously clarified that it is mainly bone marrow derived macrophages (BMDMs) infiltrating in the lesion epicenter to clear sp, rather than local microglia. Unfortunately, the pro-inflammatory phenotype of these infiltrating BMDMs is predominant which impairs wound healing. Hydralazine, as a potent vasodilator and scavenger of acrolein, has protective effects in many diseases. Hydralazine is also confirmed to promote motor function and hypersensitivity in SCI rats through scavenging acrolein. However, few studies have explored the effects of hydralazine on immunomodulation, as well as spontaneous pain and emotional response, the important syndromes in clinical patients. It remains unclear whether hydralazine affects infiltrating BMDMs after SCI. In this study, we targeted BMDMs to explore the influence of hydralazine on immune cells in a mouse model of SCI, and also investigated the contribution of polarized BMDMs to hydralazine-induced neurological function recovery after SCI in male mice. The adult male mice underwent T10 spinal cord compression. The results showed that in addition to improving motor function and hypersensitivity, hydralazine relieved SCI-induced spontaneous pain and emotional response, which is a newly discovered function of hydralazine. Hydralazine inhibited the recruitments of pro-inflammatory BMDMs and educated infiltrated BMDMs to a more reparative phenotype involving in multiple biological processes associated with SCI pathology, including immune/inflammation response, neurogenesis, lipid metabolism, oxidative stress, fibrosis formation, and angiogenesis, etc. As an overall effect, hydralazine-treated BMDMs loaden with sp partially rescued neurological function after SCI. It is concluded that hydralazine plays an immunomodulation role of educating pro-inflammatory BMDMs to a more reparative phenotype; and hydralazine-educated BMDMs contribute to hydralazine-induced improvement of neurological function in SCI mice, which provides support for drug and cell treatment options for SCI therapy.

MicroRNAs in spinal cord injury: A narrative review

Spinal cord injury (SCI) is a global medical problem with high disability and mortality rates. At present, the diagnosis and treatment of SCI are still lacking. Spinal cord injury has a complex etiology, lack of diagnostic methods, poor treatment effect and other problems, which lead to the difficulty of spinal cord regeneration and repair, and poor functional recovery. Recent studies have shown that gene expression plays an important role in the regulation of SCI repair. MicroRNAs (miRNAs) are non-coding RNA molecules that target mRNA expression in order to silence, translate, or interfere with protein synthesis. Secondary damage, such as oxidative stress, apoptosis, autophagy, and inflammation, occurs after SCI, and differentially expressed miRNAs contribute to these events. This article reviews the pathophysiological mechanism of miRNAs in secondary injury after SCI, focusing on the mechanism of miRNAs in secondary neuroinflammation after SCI, so as to provide new ideas and basis for the clinical diagnosis and treatment of miRNAs in SCI. The mechanisms of miRNAs in neurological diseases may also make them potential biomarkers and therapeutic targets for spinal cord injuries.

miR-124: A Promising Therapeutic Target for Central Nervous System Injuries and Diseases

Central nervous system injuries and diseases, such as ischemic stroke, spinal cord injury, neurodegenerative diseases, glioblastoma, multiple sclerosis, and the resulting neuroinflammation often lead to death or long-term disability. MicroRNAs are small, non-coding, single-stranded RNAs that regulate posttranscriptional gene expression in both physiological and pathological cellular processes, including central nervous system injuries and disorders. Studies on miR-124, one of the most abundant microRNAs in the central nervous system, have shown that its dysregulation is related to the occurrence and development of pathology within the central nervous system. Herein, we review the molecular regulatory functions, underlying mechanisms, and effective delivery methods of miR-124 in the central nervous system, where it is involved in pathological conditions. The review also provides novel insights into the therapeutic target potential of miR-124 in the treatment of human central nervous system injuries or diseases.

MicroRNA-124: A Key Player in Microglia-Mediated Inflammation in Neurological Diseases

Neurological disorders are mainly characterized by progressive neuron loss and neurological deterioration, which cause human disability and death. However, many types of neurological disorders have similar pathological mechanisms, including the neuroinflammatory response. Various microRNAs (miRs), such as miR-21, miR-124, miR-146a, and miR-132 were recently shown to affect a broad spectrum of biological functions in the central nervous system (CNS). Microglia are innate immune cells with important roles in the physiological and pathological activities of the CNS. Recently, abnormal expression of miR-124 was shown to be associated with the occurrence and development of various diseases in CNS via regulating microglia function. In addition, miR-124 is a promising biomarker and therapeutic target. Studies on the role of miR-124 in regulating microglia function involved in pathogenesis of neurological disorders at different stages will provide new ideas for the use of miR-124 as a therapeutic target for different CNS diseases.

miRNA-221 Regulates Spinal Cord Injury-Induced Inflammatory Response through Targeting TNF-α Expression

OBJECTIVES

To investigate the roles of miR-221 in spinal cord injury (SCI) as well as the underlying mechanism.

METHODS

A mouse model of SCI was generated and used to examine dynamic changes in grip strength of the mouse upper and lower limbs. The expression of miR-221 and tumor necrosis factor-α (TNF-α) was detected by RT-qPCR and Western blot. Levels of inflammation and oxidative stress in microglia cells of the injured mice overexpressing miR-221 were then measured by ELISA. Bioinformatics analysis and dual-luciferase reporter assay were conducted to identify the miR-221 target.

RESULTS

We successfully constructed SCI mouse model. The results of qRT-PCR showed that miR-221 was gradually upregulated in the spinal cord tissue of mice in the SCI group with the prolonged injury time. At the same time, the mRNA and protein of TNF-α gradually decreased. We further confirmed through cell experiments that the inflammatory factors TNF-α and IL-6, as well as iNOS and eROS, were upregulated in spinal cord microglia cells of SCI mice, and upregulation of miR-122 can inhibit their expression. Finally, the luciferase reporter experiment confirmed that miR-122 targeted TNF-α.

CONCLUSIONS

We present evidence that miR-221 promotes functional recovery of the injured spinal cord through targeting TNF-α, while alleviating inflammatory response and oxidative stress.

MiR-495 regulates cell proliferation and apoptosis in H2O2 stimulated rat spinal cord neurons through targeting signal transducer and activator of transcription 3 (STAT3)

Background

MicroRNA-495 (miR-495) is a post-translational modulator that performs several functions, and it is involved in several disease states. On the other hand, the physiological functions of miR-495 in H₂O₂ stimulated mouse spinal cord neuronal dysfunction have not yet been fully understood.

Methods

In this study, we speculated that miR-495 may regulate the expression of STAT3 in the processes of neuronal proliferation and apoptosis following spinal cord injury (SCI). Cell viability was assessed with methyl thiazolyl tetrazolium (MTT) assay. Caspase-3 activity was assayed with ELISA. Cellular apoptotic changes were measured with TUNEL assay. Intracellular ROS production was determined by measuring uptake of dichlorodihydrofluorescein diacetate (DCFH-DA; PCR was used to assay the mRNA expression of STAT3 gene bearing predicted targeting positions for miR-495, while qRT-PCR was used to measure miR-495 mRNA.

Results

The results demonstrated that treatment of SCNs with H₂O₂ led to a significant decrease in cell survival, while it enhanced apoptosis. The H₂O₂ treatment induced cell membrane dysfunction, and increased ROS levels and DNA damage. Interestingly, the expression of miR-495 was markedly suppressed when SCNs were exposed to H₂O₂. However, miR-495 overexpression reversed H₂O₂-induced cytotoxicity and apoptosis in SCNs. Moreover, H₂O₂ exposure elevated protein and mRNA concentrations of STAT3 in SCNs. Bioinformatics analysis showed likely binding domains of miR-495 in the 3'-untranslated regions of STAT3 in SCNs. MiR-495 loss-of-function and gain-of-function significantly up-regulated and down-regulated both STAT3 mRNA and protein expressions, respectively, in SCNs.

Conclusions

miR-495 overexpression inhibited H₂O₂-induced SCN dysfunction. This mechanism was mediated through the down-regulation of STAT3 expression.

The Effect of Melatonin Modulation of Non-coding RNAs on Central Nervous System Disorders: An Updated Review

Melatonin is a hormone produced in and secreted by the pineal gland. Besides its role in regulating circadian rhythms, melatonin has a wide range of protective functions in the central nervous system (CNS) disorders. The mechanisms underlying this protective function are associated with the regulatory effects of melatonin on related genes and proteins. In addition to messenger ribonucleic acid (RNA) that can be translated into protein, an increasing number of non-coding RNAs in the human body are proven to participate in many diseases. This review discusses the current progress of research on the effects of melatonin modulation of non-coding RNAs (ncRNAs), including microRNA, long ncRNA, and circular RNA. The role of melatonin in regulating common pathological mechanisms through these ncRNAs is also summarized. Furthermore, the ncRNAs, currently shown to be involved in melatonin signaling in CNS diseases, are discussed. The information compiled in this review will open new avenues for future research into melatonin mechanisms and provide a further understanding of ncRNAs in the CNS.

Roles of miRNAs in spinal cord injury and potential therapeutic interventions

Spinal cord injury (SCI) affects approximately 200,000 individuals per year worldwide. There are more than 27 million people worldwide living with long-term disability due to SCI. Historically, it was thought that the central nervous system (CNS) had little ability for regeneration; however, more recent studies have demonstrated potential for repair within the CNS. Because of this, there exists a renewed interest in the discovery of novel approaches to promote regeneration in the CNS including the spinal cord. It is important to know the roles of the microRNAs (miRNAs) in modulation of pathogenesis in SCI and the potentials of the miRNA-based clinical interventions for controlling post-injury symptoms and improving functional recovery. The miRNAs, which are non-coding RNAs with an average of 22 nucleotides in length, are post-transcriptional gene regulators that cause degradation of the target mRNAs and thus negatively control their translation. This review article focuses on current research related to miRNAs and their roles in modulating SCI symptoms, asserting that miRNAs contribute to critical post-SCI molecular processes including neuroplasticity, functional recovery, astrogliosis, neuropathic pain, inflammation, and apoptosis. In particular, miR-96 provides a promising therapeutic opportunity to improve the outcomes of clinical interventions, including the way SCI injuries are evaluated and treated.

Emerging molecular therapeutic targets for spinal cord injury

Introduction: Spinal cord injury (SCI) is a complicated and devastating neurological disorder. Patients with SCI usually have dramatically reduced quality of life. In recent years, numerous studies have reported advances in understanding the pathophysiology of SCI and developing preclinical therapeutic strategies for SCI, including various molecular therapies, and yet there is still no cure. Areas covered: After SCI, tissue damage, responses and repair involve interactions among many cellular components, including neurons, axons, glia, leukocytes, and other cells. Accordingly, numerous cellular genes and molecules have become therapeutic targets for neural tissue repair, circuit reconstruction, and behavioral restoration. Here, we review the major recent advances in biological and molecular strategies to enhance neuroprotection, axon regeneration, remyelination, neuroplasticity and functional recovery in preclinical studies of SCI. Expert opinion: Researchers have made tremendous progress in identifying individual and combined molecular therapies in animal studies. It is very important to identify additional highly effective treatments for early neuroprotective intervention and for functionally meaningful axon regeneration and neuronal reconnections. Because multiple mechanisms contribute to the functional loss after SCI, combining the most promising approaches that target different pathophysiological and molecular mechanisms should exhibit synergistic actions for maximal functional restoration. [Databases searched: PubMed; inclusive dates: 6/27/2019].

MicroRNA‑124 improves functional recovery and suppresses Bax‑dependent apoptosis in rats following spinal cord injury

Spinal cord injury (SCI) induces aberrant expression of microRNAs (miRNAs), causing various secondary injury responses, including inflammation, apoptosis and oxidative stress. However, the mechanisms underlying miRNA-mediated apoptosis have not been fully elucidated. In the present study, a rat SCI model was established and a miRNA microarray was analyzed to detect miRNA expression profiles at different times post-SCI. The Basso, Beattie and Bresnahan score, cresyl violet staining and terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling staining were used to evaluate locomotor activity, lesion volume and neuronal cell apoptosis, respectively, at different time points post-SCI. It was observed that numerous miRNAs were altered at 14 days post-SCI and miR-124 was one of the most notably downregulated miRNAs. The present results demonstrated that overexpression of miR-124 by agomir-124 improves functional recovery, decreases lesion size and suppresses neuronal cell apoptosis in a rat SCI model. Luciferase reporter assay demonstrated that miR-124 inhibited apoptosis regulator BAX (Bax) expression, a key molecule in the activation of the mitochondrial apoptotic pathway, by targeting its 3′-untranslated region in BV-2 cells. Furthermore, restoration of Bax by pc-DNA-Bax inhibits the protective effect of miR-124 in H₂O₂-treated BV-2 cells. Notably, the present results demonstrated that miR-124 may block the mitochondrial apoptotic pathway by inhibiting Bax, cleaved-caspase-9 and cleaved-caspase-3 expression in rats following SCI. Collectively, the present results suggested that miR-124 may improve functional recovery and supress neuronal cell apoptosis by blocking the mitochondrial apoptotic pathway in SCI rats, suggesting that miR-124 may serve as a potential therapeutic target in SCI treatment.

RETRACTED: Tanshinone IIA alleviates oxidative damage after spinal cord injury in vitro and in vivo through up-regulating miR-124

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Corresponding Author with the agreement of the editor. The authors used DMSO (dimethyl sulfoxide) to dissolve tanshinone IIA in this experiment, but even after dilution, DMSO also can induce toxicity of PC12 cells, which also can affect the result of the experiment. After discussion, the authors found that sulfotanshinone sodium injection can be used to replace tanshinone II A, which is both an aqueous solution and has been clinically proved to be an ideal substitute. Further, in error, the authors used 0μM /12.5μM /50μM /100μM /200μM H2O2 to stimulate oxidative injury as in figure 1A, but missed 25μM H2O2, which may also affect the experimental results.

Lentivirus-mediated microRNA-124 gene-modified bone marrow mesenchymal stem cell transplantation promotes the repair of spinal cord injury in rats

Our study aims to explore the effects of lentivirus-mediated microRNA-124 (miR-124) gene-modified bone marrow mesenchymal stem cell (BMSC) transplantation on the repair of spinal cord injury (SCI) in rats. BMSCs were isolated from the bone marrow of rats. The target gene miR-124 was identified using a luciferase-reporter gene assay. Seventy-two rats were selected for construction of the SCI model, and the rats were randomly divided into the blank group, sham group, SCI group, negative control (NC) group, overexpressed miR-124 group and si-PDXK group. The mRNA expression of miR-124 and the mRNA and protein expression of pyridoxal kinase (PDXK) were detected by quantitative real-time polymerase chain reaction and western blotting. The locomotor capacity of the rats was evaluated using the Basso, Beattie and Bresnahan (BBB) scale. Brdu, neuron-specific enolase (NSE), neurofilament (NF) and microtubule-associated protein 2 (MAP2) were detected using immunohistochemistry. The expression levels of thyrotropin-releasing hormone (TRH), prostacyclin (PGI2) and gangliosides (GM) were measured using an enzyme-linked immunosorbent assay. PDXK was identified as the target gene of miR-124. The overexpressed miR-124 group exhibited higher miR-124 expression than the SCI, NC and si-PDXK groups. Compared with the SCI and NC groups, the PDXK expression was downregulated in the overexpressed miR-124 and si-PDXK groups, and the BBB scores were significantly increased 7, 21 and 35 days after transplantation. The double-labeled positive cell densities (Brdu+NSE/NF/MAP2) and the expression levels of TRH, PGI2 and GM in the overexpressed miR-124 group were significantly higher than those in the NC and SCI groups. These results indicated that miR-124 targeted PDXK to accelerate the differentiation of BMSCs into neurocytes and promote SCI repair.

Non-coding RNAs and neuroprotection after acute CNS injuries

Accumulating evidence indicates that various classes of non-coding RNAs (ncRNAs) including microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs) and long non-coding RNAs (lncRNAs) play important roles in normal state as well as the diseases of the CNS. Interestingly, ncRNAs have been shown to interact with messenger RNA, DNA and proteins, and these interactions could induce epigenetic modifications and control transcription and translation, thereby adding a new layer of genomic regulation. The ncRNA expression profiles are known to be altered after acute CNS injuries including stroke, traumatic brain injury and spinal cord injury that are major contributors of morbidity and mortality worldwide. Hence, a better understanding of the functional significance of ncRNAs following CNS injuries could help in developing potential therapeutic strategies to minimize the neuronal damage in those conditions. The potential of ncRNAs in blood and CSF as biomarkers for diagnosis and/or prognosis of acute CNS injuries has also gained importance in the recent years. This review highlighted the current progress in the understanding of the role of ncRNAs in initiation and progression of secondary neuronal damage and their application as biomarkers after acute CNS injuries.

The Role of microRNA Markers in the Diagnosis, Treatment, and Outcome Prediction of Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition that affects many people worldwide. Treatment focuses on controlling secondary injury cascade and improving regeneration. It has recently been suggested that both the secondary injury cascade and the regenerative process are heavily regulated by microRNAs (miRNAs). The measurement of specific biomarkers could improve our understanding of the disease processes, and thereby provide clinicians with the opportunity to guide treatment and predict clinical outcomes after SCI. A variety of miRNAs exhibit important roles in processes of inflammation, cell death, and regeneration. These miRNAs can be used as diagnostic tools for predicting outcome after SCI. In addition, miRNAs can be used in the treatment of SCI and its symptoms. Significant laboratory and clinical evidence exist to show that miRNAs could be used as robust diagnostic and therapeutic tools for the treatment of patients with SCI. Further clinical studies are warranted to clarify the importance of each subtype of miRNA in SCI management.