Altered expression of miRNA-21 and its targets in the hippocampus after traumatic brain injury

Epigenetics and the neurodegenerative process

Neurological diseases are multifactorial, genetic and environmental. Environmental factors such as diet, physical activity and emotional state are epigenetic factors. Environmental markers are responsible for epigenetic modifications. The effect of epigenetic changes is increased inflammation of the nervous system and neuronal damage. In recent years, it has been shown that epigenetic changes may cause an increased risk of neurological disorders but, currently, the relationship between epigenetic modifications and neurodegeneration remains unclear. This review summarizes current knowledge about neurological disorders caused by epigenetic changes in diseases such as Alzheimer's disease, Parkinson's disease, stroke and epilepsy. Advances in epigenetic techniques may be key to understanding the epigenetics of central changes in neurological diseases.

Research on stem cell therapy for spinal cord injury: a bibliometric and visual analysis from 2018-2023

Objectives: The aim of this study was to conduct a bibliometric analysis of the literature on stem cell treatment for spinal cord injury to gain an intuitive understanding of how the field is progressing, discover topics of interest, and determine what development trends are emerging in this field. Background: Spinal cord injury and its complications often cause an enormous economic burden, and postinjury repair and treatment have always been challenging in clinical and scientific research. Stem cell therapy for spinal cord injury can prevent immune rejection and induce the release of neuroprotective and anti-inflammatory factors to reduce the production of stress-related proteins, reactive oxygen species, and inflammatory reactions. Methods: We analyzed the number and quality of publications in the field of stem cell therapy in spinal cord injury between 2018.01.01 and 2023.06.30 in the core collection database of Web of Science. CiteSpace and VOSviewer were used to sort and summarize these studies by country, institution, authors' publications, and collaborative networks. In addition, the research topics of interest were identified and summarized. Results: This study ultimately included 2,150 valid papers, with the number of publications showing a gradual upward trend. The country, institution, author and journal with the greatest number of publications and citations are China, the Chinese Academy of Sciences, Dai JW, and the International Journal of Molecular Sciences, respectively. The top three high-frequency keyword clusters were hereditary paraplegia, reactive astrocytes and tissue engineering. Conclusion: With the help of visual analysis, we identified general trends and research topics of interest in the field of spinal cord injury over the last 5 years. Our findings suggest that stem cell transplantation for spinal cord injury and exosome therapy may be a focus of future research. This study provides a foundation for future research on stem cell therapy as well as clinical efforts in this field.

Role of regulatory non-coding RNAs in traumatic brain injury

Traumatic brain injury (TBI) is a potentially fatal health event that cannot be predicted in advance. After TBI occurs, it can have enduring consequences within both familial and social spheres. Yet, despite extensive efforts to improve medical interventions and tailor healthcare services, TBI still remains a major contributor to global disability and mortality rates. The prompt and accurate diagnosis of TBI in clinical contexts, coupled with the implementation of effective therapeutic strategies, remains an arduous challenge. However, a deeper understanding of changes in gene expression and the underlying molecular regulatory processes may alleviate this pressing issue. In recent years, the study of regulatory non-coding RNAs (ncRNAs), a diverse class of RNA molecules with regulatory functions, has been a potential game changer in TBI research. Notably, the identification of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and other ncRNAs has revealed their potential as novel diagnostic biomarkers and therapeutic targets for TBI, owing to their ability to regulate the expression of numerous genes. In this review, we seek to provide a comprehensive overview of the functions of regulatory ncRNAs in TBI. We also summarize regulatory ncRNAs used for treatment in animal models, as well as miRNAs, lncRNAs, and circRNAs that served as biomarkers for TBI diagnosis and prognosis. Finally, we discuss future challenges and prospects in diagnosing and treating TBI patients in the clinical settings.

Ursolic acid ameliorates traumatic brain injury in mice by regulating microRNA-141-mediated PDCD4/PI3K/AKT signaling pathway

BACKGROUND

Neuronal apoptosis and inflammation are the key pathogenic features of secondary brain injury, which results in the neurological impairment that traumatic brain injury (TBI) patients experience. Ursolic Acid (UA) has been shown to have neuroprotective properties against brain damage, however, detailed mechanisms have not been fully disclosed. Research on brain-related microRNAs (miRNAs) has opened up new possibilities for the neuroprotective treatment of UA by manipulating miRNAs. The present study was designed to investigate the impact of UA on neuronal apoptosis and the inflammatory response in TBI mice.

METHODS

The mice's neurologic condition was assessed using the modified neurological severity score (mNSS) and the learning and memory abilities were assessed using the Morris water maze (MWM). Cell apoptosis, oxidative stress, and inflammation were utilized to examine the impact of UA on neuronal pathological damage. miR-141-3p was selected to evaluate whether UA influences miRNAs in a way that has neuroprotective benefits.

RESULTS

The results showed that UA markedly decreased brain edema and neuronal mortality through oxidative stress and neuroinflammation in TBI mice. Using data from the GEO database, we found that miR-141-3p was considerably downregulated in TBI mice and that this downregulation was reversed by UA treatment. Further studies have shown that UA regulates miR-141-3p expression to exhibit its neuroprotective effect in mouse models and cell injury models. Then, miR-141-3p was discovered to directly target PDCD4 in TBI mice and neurons, a well-known PI3K/AKT pathway regulator in the neurons. Most importantly, the upregulation of phosphorylated (p)-AKT and p-PI3K provided the most compelling evidence that UA reactivated the PI3K/AKT pathway in the TBI mouse model, which was through regulating miR-141-3p.

CONCLUSION

Our findings support the notion that UA can improve TBI by modulating miR-141 mediated PDCD4/PI3K/AKT signaling pathway.

Non-coding RNAs and Exosomal Non-coding RNAs in Traumatic Brain Injury: the Small Player with Big Actions

Nowadays, there is an increasing concern regarding traumatic brain injury (TBI) worldwide since substantial morbidity is observed after it, and the long-term consequences that are not yet fully recognized. A number of cellular pathways related to the secondary injury in brain have been identified, including free radical production (owing to mitochondrial dysfunction), excitotoxicity (regulated by excitatory neurotransmitters), apoptosis, and neuroinflammatory responses (as a result of activation of the immune system and central nervous system). In this context, non-coding RNAs (ncRNAs) maintain a fundamental contribution to post-transcriptional regulation. It has been shown that mammalian brains express high levels of ncRNAs that are involved in several brain physiological processes. Furthermore, altered levels of ncRNA expression have been found in those with traumatic as well non-traumatic brain injuries. The current review highlights the primary molecular mechanisms participated in TBI that describes the latest and novel results about changes and role of ncRNAs in TBI in both clinical and experimental research.

miRNA dysregulation in traumatic brain injury and epilepsy: a systematic review to identify putative biomarkers for post-traumatic epilepsy

Traumatic brain injury (TBI) leads to post-traumatic epilepsy (PTE); hence, both TBI and PTE share various similar molecular mechanisms. MicroRNA (miRNA) is a small noncoding RNA that acts as a gene-silencing molecule. Notably, the dysregulation of miRNAs in various neurological diseases, including TBI and epilepsy, has been reported in several studies. However, studies on commonly dysregulated miRNAs and the regulation of shared pathways in both TBI and epilepsy that can identify potential biomarkers of PTE are still lacking. This systematic review covers the peer-review publications of TBI and database studies of epilepsy-dysregulated miRNAs of clinical studies. For TBI, 290 research articles were identified after screening, and 12 provided data for dysregulated miRNAs in humans. The compiled data suggest that 85 and 222 miRNAs are consecutively dysregulated in TBI and epilepsy. In both, 10 miRNAs were found to be commonly dysregulated, implying that they are potentially dysregulated miRNAs for PTE. Furthermore, the targets and involvement of each putative miRNA in different pathways were identified and evaluated. Additionally, clusters of predicted miRNAs were analyzed. Each miRNA's regulatory role was linked with apoptosis, inflammation, and cell cycle regulation pathways. Hence, these findings provide insight for future diagnostic biomarkers.

The Role of miR-20 in Health and Disease of the Central Nervous System

Current understanding of the mechanisms underlying central nervous system (CNS) injury is limited, and traditional therapeutic methods lack a molecular approach either to prevent acute phase or secondary damage, or to support restorative mechanisms in the nervous tissue. microRNAs (miRNAs) are endogenous, non-coding RNA molecules that have recently been discovered as fundamental and post-transcriptional regulators of gene expression. The capacity of microRNAs to regulate the cell state and function through post-transcriptionally silencing hundreds of genes are being acknowledged as an important factor in the pathophysiology of both acute and chronic CNS injuries. In this study, we have summarized the knowledge concerning the pathophysiology of several neurological disorders, and the role of most canonical miRNAs in their development. We have focused on the miR-20, the miR-17~92 family to which miR-20 belongs, and their function in the normal development and disease of the CNS.

Effects of Methylprednisolone in the Treatment of Spinal Cord Injuries by Evaluation of microRNA-21: An Experimental Study

BACKGROUND AND STUDY AIMS

 Spinal cord injury (SCI) is one of the most complicated pathologies that affect active young males. miR-21 primarily regulates several cellular processes. We aimed to elucidate the regulatory role of miR-21 and test methylprednisolone as a disease-modifying agent on experimental SCI tissues.

METHODS

 A total of 36 8- to 10-week-old adult female Sprague-Dawley rats weighing 250 to 300 g were used. Animals were randomly divided into six groups. Except for groups 1 and 4, the spinal trauma model was applied to all animal groups using the clipping method. In groups 3 and 6, methylprednisolone was given. For real-time polymerase chain reaction (PCR) investigations, rats in groups 1, 2, and 3 were reoperated on after the first postoperative day, whereas those in groups 4, 5, and 6 were reoperated on after postoperative day 7 and spinal cord samples from the laminectomy area were removed for gene expression analysis. Relative gene expression of miR-21, Gfap, Vim, Stat3, Faslg, Pten, Bax, Bcl2, Cox2, and Il6 were determined with quantitative reverse transcription (qRT) PCR.

RESULTS

 In group 3, the miR-21 expression significantly increased compared with groups 1 and 2. When compared with group 3, a decrease in miR-21 expression was observed in group 6 (p < 0.05). When compared with group 4, group 6 had lower levels of Gfap, Pten, Stat3, and Bax (p < 0.05).

CONCLUSIONS

 miR-21 supports the beneficial aspects of the body's healing mechanisms following SCI. In the acute phase, the use of methylprednisolone increases miR-21 expression in the early period of trauma. Methylprednisolone increases some astrogliosis and inflammation biomarkers' levels; however, it did not affect the apoptotic biomarkers.

Clinical-Pathological Study on Expressions β-APP, GFAP, NFL, Spectrin II, CD68 to Verify Diffuse Axonal Injury Diagnosis, Grade and Survival Interval

Traumatic brain injury (TBI) is one of the leading causes of death worldwide, particularly in young people. Diffuse axonal injuries (DAI) are the result of strong rotational and translational forces on the brain parenchyma, leading to cerebral oedema and neuronal death. DAI is typically characterized by coma without focal lesions at presentation and is defined by localized axonal damage in multiple regions of the brain parenchyma, often causing impairment of cognitive and neuro-vegetative function. Following TBI, axonal degeneration has been identified as a progressive process that begins with the disruption of axonal transport, leading subsequently to axonal swelling, axonal ballooning, axonal retraction bulges, secondary disconnection and Wallerian degeneration. The objective of this paper is to report on a series of patients who have suffered fatal traumatic brain injury, in order to verify neurological outcomes in dynamics, relative to the time of injury, using antibodies for neurofilament (NFL), spectrin II, beta-amyloid (β-APP), glial fibrillary acidic protein (GFAP) and cluster of differentiation 68 (CD68). From the studied cases, a total of 50 cases were chosen, which formed two study groups. The first study group comprises 30 cases divided according to survival interval. The control group comprises 20 cases with no history of traumatic brain injury. Cardiovascular disease and history of stroke, cases suffering from loss of vital functions, a post-traumatic survival time of less than 15 min, autolysis and putrefaction were established as criteria for exclusion. Based on their expression, we tested for diagnosis and degree of DAI as a strong predictor of mortality. Immunoreactivity was significantly increased in the DAI group compared to the control group. The earliest changes were recorded for GFAP and CD68 immunolabeling, followed by β-APP, spectrin II and NFM. The most intense changes in immunostaining were recorded for spectrin II. Comparative analysis of brain apoptosis, reactive astrocytosis and inflammatory reaction using specific immunohistochemical markers can provide important information on diagnosis of DAI and prognosis, and may elucidate the timing of the traumatic event in traumatic brain injury.

The role of miRNA in retinal ganglion cell health and disease

miRNA are short non-coding RNA responsible for the knockdown of proteins through their targeting and silencing of complimentary mRNA sequences. The miRNA landscape of a cell thus affects the levels of its proteins and has significant consequences to its health. Deviations in this miRNA landscape have been implicated in a variety of neurodegenerative diseases and have also garnered interest as targets for treatment. Retinal ganglion cells are the sole projection neuron of the retina with their axons making up the optic nerve. They are a focus of study not only for their importance in vision and the myriad of blinding diseases characterized by their dysfunction and loss, but also as a model of other central nervous system diseases such as spinal cord injury and traumatic brain injury. This review summarizes current knowledge on the role of miRNA in retinal ganglion cell function, highlighting how perturbations can result in disease, and how modulating their abundance may provide a novel avenue of therapeutic research.

MicroRNA miR-21 Decreases Post-stroke Brain Damage in Rodents

Due to their role in controlling translation, microRNAs emerged as novel therapeutic targets to modulate post-stroke outcomes. We previously reported that miR-21 is the most abundantly induced microRNA in the brain of rodents subjected to preconditioning-induced cerebral ischemic tolerance. We currently show that intracerebral administration of miR-21 mimic decreased the infarct volume and promoted better motor function recovery in adult male and female C57BL/6 mice subjected to transient middle cerebral artery occlusion. The miR-21 mimic treatment is also efficacious in aged mice of both sexes subjected to focal ischemia. Mechanistically, miR-21 mimic treatment decreased the post-ischemic levels of several pro-apoptotic and pro-inflammatory RNAs, which might be responsible for the observed neuroprotection. We further observed post-ischemic neuroprotection in adult mice administered with miR-21 mimic intravenously. Overall, the results of this study implicate miR-21 as a promising candidate for therapeutic translation after stroke.

Saliva RNA biomarkers predict concussion duration and detect symptom recovery: a comparison with balance and cognitive testing

OBJECTIVE

The goals of this study were to assess the ability of salivary non-coding RNA (ncRNA) levels to predict post-concussion symptoms lasting ≥ 21 days, and to examine the ability of ncRNAs to identify recovery compared to cognition and balance.

METHODS

RNA sequencing was performed on 505 saliva samples obtained longitudinally from 112 individuals (8-24-years-old) with mild traumatic brain injury (mTBI). Initial samples were obtained ≤ 14 days post-injury, and follow-up samples were obtained ≥ 21 days post-injury. Computerized balance and cognitive test performance were assessed at initial and follow-up time-points. Machine learning was used to define: (1) a model employing initial ncRNA levels to predict persistent post-concussion symptoms (PPCS) ≥ 21 days post-injury; and (2) a model employing follow-up ncRNA levels to identify symptom recovery. Performance of the models was compared against a validated clinical prediction rule, and balance/cognitive test performance, respectively.

RESULTS

An algorithm using age and 16 ncRNAs predicted PPCS with greater accuracy than the validated clinical tool and demonstrated additive combined utility (area under the curve (AUC) 0.86; 95% CI 0.84-0.88). Initial balance and cognitive test performance did not differ between PPCS and non-PPCS groups (p > 0.05). Follow-up balance and cognitive test performance identified symptom recovery with similar accuracy to a model using 11 ncRNAs and age. A combined model (ncRNAs, balance, cognition) most accurately identified recovery (AUC 0.86; 95% CI 0.83-0.89).

CONCLUSIONS

ncRNA biomarkers show promise for tracking recovery from mTBI, and for predicting who will have prolonged symptoms. They could provide accurate expectations for recovery, stratify need for intervention, and guide safe return-to-activities.

miRNAs as Potential Biomarkers for Traumatic Brain Injury: Pathway From Diagnosis to Neurorehabilitation

BACKGROUND

Biomarkers that can advance precision neurorehabilitation of the traumatic brain injury (TBI) are needed. MicroRNAs (miRNAs) have biological properties that could make them well suited for playing key roles in differential diagnoses and prognoses and informing likelihood of responsiveness to specific treatments.

OBJECTIVE

To review the evidence of miRNA alterations after TBI and evaluate the state of science relative to potential neurorehabilitation applications of TBI-specific miRNAs.

METHODS

This scoping review includes 57 animal and human studies evaluating miRNAs after TBI. PubMed, Scopus, and Google Scholar search engines were used.

RESULTS

Gold standard analytic steps for miRNA biomarker assessment are presented. Published studies evaluating the evidence for miRNAs as potential biomarkers for TBI diagnosis, severity, natural recovery, and treatment-induced outcomes were reviewed including statistical evaluation. Growing evidence for specific miRNAs, including miR21, as TBI biomarkers is presented.

CONCLUSIONS

There is evidence of differential miRNA expression in TBI in both human and animal models; however, gaps need to be filled in terms of replication using rigorous, standardized methods to isolate a consistent set of miRNA changes. Longitudinal studies in TBI are needed to understand how miRNAs could be implemented as biomarkers in clinical practice.

Penetrating Ballistic-Like Brain Injury Leads to MicroRNA Dysregulation, BACE1 Upregulation, and Amyloid Precursor Protein Loss in Lesioned Rat Brain Tissues

Severe traumatic brain injury (TBI) is a risk factor for neurodegenerative diseases. Yet, the molecular events involving dysregulated miRNAs that may be associated with protein degradation in the brain remains elusive. Quantitation of more than 800 miRNAs was conducted using rat ipsilateral coronal brain tissues collected 1, 3, or 7 days after penetrating ballistic-like brain injury (PBBI). As a control for each time-point, Sham-operated animals received craniotomy alone. Microarray and systems biology analysis indicated that the amplitude and complexity of miRNAs affected were greatest 7 day after PBBI. Arrays and Q-PCR inferred that dysregulation of miR-135a, miR-328, miR-29c, and miR-21 were associated with altered levels of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), PSEN1, PSEN2, and amyloid precursor protein (APP) genes. These events were followed by increased levels of mature BACE1 protein and concomitant loss of full length APP within 3–7 days, then elevation of amyloid beta (Aβ)-40 7 days after PBBI. This study indicates that miRNA arrays, coupled with systems biology, may be used to guide study design prior validation of miRNA dysregulation. Associative analysis of miRNAs, mRNAs, and proteins within a proposed pathway are poised for further validation as biomarkers and therapeutic targets relevant to TBI-induced APP loss and subsequent Aβ peptide generation during neurodegeneration.

Validity of Serum miRNA 93 and miRNA 191 to Reduce Unnecessary Computed Tomography in Patients With Mild Head Trauma

Background

Indication for the appropriate use of cranial computed tomography (CCT) in patients with mild head trauma (MHT) based on history and physical examination alone remains unclear. Recent studies have been reported that 90% of patients with MHT who undergo CCT under the present clinical decision rules have no clinically important brain injuries. We aimed to investigate whether peripheral blood expression of microRNA 93 (miR93) and microRNA 191 (miR191) in patients with MHT can predict the presence or absence of intracranial injury, reducing the unnecessary use of CCT.

Methods

Fifty-nine consecutive adult patients with isolated MHT undergoing CCT based on the clinical decision guidelines of the New Orleans criteria and 91 age- and sex-matched controls were enrolled in this prospective observational cohort study. Patients were divided into two groups: those without or with traumatic intracerebral or extracerebral lesions identified by CCT. Patients were further divided into two subgroups based on the presence or absence of traumatic parenchymal lesions defined as traumatic brain injury (TBI).

Results

Mean serum miR93 and miR191 levels differed significantly between study groups. Of the 79 patients investigated, 16 exhibited trauma-relevant lesions on CCT scan (CCT+). With a cut-off limit of 0.15, miR191 had an area under the curve value of 0.765 (0.640 - 0.889), with sensitivity of 68.1% and specificity of 68.8% in CCT+ patients. Compared to MHT patients without TBI, mean serum miR191 levels were markedly elevated in patients with TBI. However, miR93 levels did not exhibit significant changes in either group.

Conclusions

Circulating miRNA levels increased after MHT and differentiated patients with and without intracranial or extracranial lesions demonstrable on CCT. Adding the measurement of serum miRNAs particularly miR191 to the clinical decision rules for a CCT scan in patients with MHI could allow a reduction in scans.

MicroRNA alterations in neuropathologic cognitive disorders with an emphasis on dementia: Lessons from animal models

Cognitive dysfunction is a state of losing or having difficulties in remembering, learning, focusing, or making decisions that impact individual healthy life. Small single-stranded and nonprotein coding RNAs, microRNAs (miRNAs) participate actively in regulatory processes, incorporate cognitive signaling pathways, and intensely affect cognitive evolution. miRNAs exert their modification activities through translational or transcriptional processes. Reportedly, cognitive impairment and dementia are rising, especially in developing countries. Herein we provided a brief review of original studies addressing miRNA changes in the most common neurological diseases with a focus on dementia and Alzheimer's disease. It must be noted that an increase in the level of certain miRNAs but a decrease in other ones deteriorate cognitive performance. The current review revealed that induction of miR-214-3p, miR-302, miR-21, miR- 200b/c, miR-207, miR-132, miR-188-3p and 5p, and miR-873 improved cognitive impairment in various cognitive tasks. On the other hand, intentionally lowering the level of miR-34a, miR-124, miR-574, and miR-191a enhanced cognitive function and memory. Synaptic dysfunction is a core cause of cognitive dysfunction; miRNA-34, miRNA-34-c, miRNA-124, miRNA-188-5p, miRNA-210-5p, miRNA-335-3p, and miRNA-134 strongly influence synaptic-related mechanisms. The downregulation of miRNA-132 aggregates both amyloid and tau in tauopathy. Concerning the massive burden of neurological diseases worldwide, the future challenge is the translation of animal model knowledge into the detection of pathophysiological stages of neurocognitive disorders and designing efficient therapeutic strategies. While the delivery procedure of agomir or antagomir miRNAs into the brain is invasive and only applied in animal studies, finding a safe and specific delivery route is a priority.

Chronic Regulation of miR-124-3p in the Perilesional Cortex after Experimental and Human TBI

Traumatic brain injury (TBI) dysregulates microRNAs, which are the master regulators of gene expression. Here we investigated the changes in a brain-enriched miR-124-3p, which is known to associate with major post-injury pathologies, such as neuroinflammation. RT-qPCR of the rat tissue sampled at 7 d and 3 months in the perilesional cortex adjacent to the necrotic lesion core (aPeCx) revealed downregulation of miR-124-3p at 7 d (fold-change (FC) 0.13, p < 0.05 compared with control) and 3 months (FC 0.40, p < 0.05) post-TBI. In situ hybridization confirmed the downregulation of miR-124-3p at 7 d and 3 months post-TBI in the aPeCx (both p < 0.01). RT-qPCR confirmed the upregulation of the miR-124-3p target Stat3 in the aPeCx at 7 d post-TBI (7-fold, p < 0.05). mRNA-Seq revealed 312 downregulated and 311 upregulated miR-124 targets (p < 0.05). To investigate whether experimental findings translated to humans, we performed in situ hybridization of miR-124-3p in temporal lobe autopsy samples of TBI patients. Our data revealed downregulation of miR-124-3p in individual neurons of cortical layer III. These findings indicate a persistent downregulation of miR-124-3p in the perilesional cortex that might contribute to post-injury neurodegeneration and inflammation.

Epigenetic mechanisms of neurodegenerative diseases and acute brain injury

Epigenetic modifications are emerging as major players in the pathogenesis of neurodegenerative disorders and susceptibility to acute brain injury. DNA and histone modifications act together with non-coding RNAs to form a complex gene expression machinery that adapts the brain to environmental stressors and injury response. These modifications influence cell-level operations like neurogenesis and DNA repair to large, intricate processes such as brain patterning, memory formation, motor function and cognition. Thus, epigenetic imbalance has been shown to influence the progression of many neurological disorders independent of aberrations in the genetic code. This review aims to highlight ways in which epigenetics applies to several commonly researched neurodegenerative diseases and forms of acute brain injury as well as shed light on the benefits of epigenetics-based treatments.

MicroRNAs: The New Challenge for Traumatic Brain Injury Diagnosis

The acronym TBI refers to traumatic brain injury, an alteration of brain function, or an evidence of brain pathology, that is caused by an external force. TBI is estimated to become the third leading cause of permanent disability and mortality worldwide. TBI-related injuries can be classified in many ways, according to the degree of severity or the pathophysiology of brain injury (primary and secondary damage). Numerous cellular pathways act in secondary brain damage: excitotoxicity (mediated by excitatory neurotransmitters), free radical generation (due to mitochondrial impairment), neuroinflammatory response (due to central nervous system and immunoactivation) and apoptosis. In this scenario, microRNAs are implicated in the regulation of almost all genes at the post-transcriptional level. Several microRNAs have been demonstrated to be specifically expressed in particular cerebral areas; moreover, physiological changes in microRNA expression during normal cerebral development upon the establishment of neural networks have been characterized. More importantly, microRNAs show profound alteration in expression in response to brain pathological states, both traumatic or not. This review summarizes the most important molecular networks involved in TBI and examines the most recent and important findings on TBI-related microRNAs, both in animal and clinical studies. The importance of microRNA research holds promise to find biomarkers able to unearth primary and secondary molecular patterns altered upon TBI, to ultimately identify key points of regulation, as a valuable support in forensic pathology and potential therapeutic targets for clinical treatment.

MicroRNA-23a-3p improves traumatic brain injury through modulating the neurological apoptosis and inflammation response in mice

Secondary brain damage plays an important role in Traumatic brain injury (TBI) and inhibition of this damage has benefit for TBI treatment. However, the pathogenesis of secondary brain damage remains largely unknown. Here, we tried to explore the influence of microRNAs (miRNAs) on neuron apoptosis and inflammatory response after TBI. Firstly, the miRNA expression profiles were analyzed in the cerebral cortex tissues from the TBI mice model (controlled cortical impact) using miRNA microarray. miR-23a-3p (miR-23a) attracted our attention as its suppressive effects on apoptosis and inflammation. The further results showed that miR-23a upregulation improved long-term neurological function, the neuron apoptosis, and inhibited neuroinflammation, whereas knockdown of miR-23a had an opposite result. Using etoposide-induced primary cortical neurons injury model, we found that miR-23a was decreased in this cell model and miR-23a overexpression-suppressed etoposide induced the activity of caspase 3 and the releases of inflammatory mediators in primary cortical neurons. Phosphatase and tensin homolog (PTEN), a well‑known regulator of the AKT/mTOR pathway, was found to be a direct target of miR‑23a in the primary cortical neurons. Most importantly, it was found that miR-23a overexpression reactivated the AKT/mTOR pathway in TBI mice model, as demonstrated by the upregulation of phosphorylated (p‑)AKT and p‑mTOR. Taken together, these data indicate that miR-23a may serve as a therapeutic target for the treatment of TBI.

A hairpin DNA-fueled nanoflare for simultaneous illumination of two microRNAs in drug-induced nephrotoxic cells with target catalytic recycling amplification

The detection of specific extracellular microRNAs (miRNAs) is beneficial for the prediction of drug-induced kidney injury. Here, a novel hairpin DNA-fueled nanoflare was developed for the simultaneous detection of drug-induced nephrotoxicity-related miRNA-21 and miRNA-200c with target catalytic recycling amplification. The nanoflare utilized gold nanoparticles (AuNPs) as the highly efficient quencher to ensure a low background signal. With the help of the fueled hairpin DNA, the miRNA targets could serve as the catalysts for the assembly of DNA duplexes. Therefore, the nanoflare could respond to the miRNAs to yield signal outputs of 1 : n (target : signal) rather than an equivalent reaction ratio of 1 : 1, achieving the signal amplified detection of low-abundant miRNAs. The targets can be concurrently detected with the detection limit of 18.1 and 21.1 pM for miRNA-21 and miRNA-200c, respectively, which are approximately 2 orders of magnitude lower than that of the non-catalytic probes. In addition, this nanoflare offered a high selectivity for determination between perfectly matched targets and single-base mismatched targets. It should be noted that the nanoflare was successfully employed to predict the drug-induced nephrotoxicity by the detection of miRNAs in culture media excreted from the drug-treated renal cells using a fluorescent microplate reader. Our hairpin DNA-fueled nanoflare could also accurately detect the divergence of miRNA-21 and miRNA-200c between drug-treated nephrotoxic cells and tumor cells, demonstrating a promising potential for exploring the pathogenesis of drugs and auxiliary diagnosis of drug-induced nephrotoxicity.

MicroRNAs in central nervous system diseases: A prospective role in regulating blood-brain barrier integrity

Given the essential role of the blood-brain barrier (BBB) in the central nervous system (CNS), cumulative investigations have been performed to elucidate how modulation of BBB structural and functional integrity affects the pathogenesis of CNS diseases such as stroke, traumatic brain injuries, dementia, and cerebral infection. Recent studies have demonstrated that microRNAs (miRNAs) contribute to the maintenance of the BBB and thereby mediate CNS homeostasis. This review summarizes emerging studies that demonstrate cerebral miRNAs regulate BBB function in CNS disorders, emphasizing the direct role of miRNAs in BBB molecular composition. Evidence presented in this review will encourage a deeper understanding of the mechanisms by which miRNAs regulate BBB function, and facilitate the development of new miRNAs-based therapies in patients with CNS diseases.

Circular RNA expression profiles in neonatal rats following hypoxic-ischemic brain damage

Circular RNAs (circRNAs) have been studied in a number of diseases. However, the roles of circRNAs in hypoxic‑ischemic brain damage (HIBD) remains unknown. In the present study, high throughput sequencing was used to profile altered circRNAs in HIBD rats. A total of 66 circRNAs were identified to be differentially expressed (fold‑change >2 and P‑value <0.05) in HIBD rats compared with the control group, including 20 upregulated and 46 downregulated circRNAs. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that numerous mRNAs transcribed from the host genes of altered circRNAs were involved in brain damage and neural regeneration. The interaction of circRNA/microRNA was predicted based on TargetScan and miRanda. The results of this study demonstrated an altered circRNA expression pattern in HIBD rats and suggests important roles in HIBD physiological and pathological processes. These findings suggest a novel focus for future studies investigating the molecular mechanism underlying HIBD and possibilities for the treatment of HIBD through modulating circRNAs.

Rapid detection and cellular fluorescence imaging of the TBI biomarker Let-7i using a DNA–AgNC nanoprobe

Rapid fluorescence detection of Let-7i for TBI diagnosis and intracellular imaging have been studied using the multifunctional DNA–AgNCs.

microRNAs Sculpt Neuronal Communication in a Tight Balance That Is Lost in Neurological Disease

Since the discovery of the first microRNA 25 years ago, microRNAs (miRNAs) have emerged as critical regulators of gene expression within the mammalian brain. miRNAs are small non-coding RNAs that direct the RNA induced silencing complex to complementary sites on mRNA targets, leading to translational repression and/or mRNA degradation. Within the brain, intra- and extracellular signaling events tune the levels and activities of miRNAs to suit the needs of individual neurons under changing cellular contexts. Conversely, miRNAs shape neuronal communication by regulating the synthesis of proteins that mediate synaptic transmission and other forms of neuronal signaling. Several miRNAs have been shown to be critical for brain function regulating, for example, enduring forms of synaptic plasticity and dendritic morphology. Deficits in miRNA biogenesis have been linked to neurological deficits in humans, and widespread changes in miRNA levels occur in epilepsy, traumatic brain injury, and in response to less dramatic brain insults in rodent models. Manipulation of certain miRNAs can also alter the representation and progression of some of these disorders in rodent models. Recently, microdeletions encompassing MIR137HG, the host gene which encodes the miRNA miR-137, have been linked to autism and intellectual disability, and genome wide association studies have linked this locus to schizophrenia. Recent studies have demonstrated that miR-137 regulates several forms of synaptic plasticity as well as signaling cascades thought to be aberrant in schizophrenia. Together, these studies suggest a mechanism by which miRNA dysregulation might contribute to psychiatric disease and highlight the power of miRNAs to influence the human brain by sculpting communication between neurons.

miR-124-3p is a chronic regulator of gene expression after brain injury

Traumatic brain injury (TBI) initiates molecular and cellular pathologies that underlie post-injury morbidities, including hippocampus-related memory decline and epileptogenesis. Non-coding small RNAs are master regulators of gene expression with the potential to affect multiple molecular pathways. To evaluate whether hippocampal gene expression networks are chronically regulated by microRNAs after TBI, we sampled the dentate gyrus of rats with severe TBI induced by lateral fluid-percussion injury 3 months earlier. Ingenuity pathway analysis revealed 30 upregulated miR-124-3p targets, suggesting that miR-124-3p is downregulated post-TBI (z-score = - 5.146, p < 0.05). Droplet digital polymerase chain reaction (ddPCR) and in situ hybridization confirmed the chronic downregulation of miR-124-3p (p < 0.05). Quantitative PCR analysis of two targets, Plp2 and Stat3, indicated that their upregulation correlated with the miR-124-3p downregulation (r = - 0.647, p < 0.05; r = - 0.629, p < 0.05, respectively). Immunohistochemical staining of STAT3 confirmed the increased protein expression. STRING analysis showed that 9 of the 30 miR-124-3p targets belonged to a STAT3 network. Reactome analysis and data mining connected the targets especially to inflammation and signal transduction. L1000CDS2 software revealed drugs (e.g., importazole, trichostatin A, and IKK-16) that could reverse the observed molecular changes. The translational value of our data was emphasized by in situ hybridization showing chronic post-traumatic downregulation of miR-124-3p in the dentate gyrus of TBI patients. Analysis of another brain injury model, status epilepticus, highlighted the fact that chronic downregulation of miR-124 is a common phenomenon after brain injury. Together, our findings indicate that miR-124-3p is a chronic modulator of molecular networks relevant to post-injury hippocampal pathologies in experimental models and in humans.

Angiopoietin/Tie2 Axis Regulates the Age-at-Injury Cerebrovascular Response to Traumatic Brain Injury

Although age-at-injury influences chronic recovery from traumatic brain injury (TBI), the differential effects of age on early outcome remain understudied. Using a male murine model of moderate contusion injury, we investigated the underlying mechanism(s) regulating the distinct response between juvenile and adult TBI. We demonstrate similar biomechanical and physical properties of naive juvenile and adult brains. However, following controlled cortical impact (CCI), juvenile mice displayed reduced cortical lesion formation, cell death, and behavioral deficits at 4 and 14 d. Analysis of high-resolution laser Doppler imaging showed a similar loss of cerebral blood flow (CBF) in the ipsilateral cortex at 3 and 24 h post-CCI, whereas juvenile mice showed enhanced subsequent restoration at 2-4 d compared with adults. These findings correlated with reduced blood-brain barrier (BBB) disruption and increased perilesional vessel density. To address whether an age-dependent endothelial cell (EC) response affects vessel stability and tissue outcome, we magnetically isolated CD31⁺ ECs from sham and injured cortices and evaluated mRNA expression. Interestingly, we found increased transcripts for BBB stability-related genes and reduced expression of BBB-disrupting genes in juveniles compared with adults. These differences were concomitant with significant changes in miRNA-21-5p and miR-148a levels. Accompanying these findings was robust GFAP immunoreactivity, which was not resolved by day 35. Importantly, pharmacological inhibition of EC-specific Tie2 signaling abolished the juvenile protective effects. These findings shed new mechanistic light on the divergent effects that age plays on acute TBI outcome that are both spatial and temporal dependent.SIGNIFICANCE STATEMENT Although a clear "window of susceptibility" exists in the developing brain that could deter typical developmental trajectories if exposed to trauma, a number of preclinical models have demonstrated evidence of early recovery in younger patients. Our findings further demonstrate acute neuroprotection and improved restoration of cerebral blood flow in juvenile mice subjected to cortical contusion injury compared with adults. We also demonstrate a novel role for endothelial cell-specific Tie2 signaling in this age-related response, which is known to promote barrier stability, is heightened in the injured juvenile vasculature, and may be exploited for therapeutic interventions across the age spectrum following traumatic brain injury.

MicroRNA-21 in the Pathogenesis of Traumatic Brain Injury

MicroRNAs (miRNAs), an abundant class of small noncoding RNA molecules, which regulate gene expression by functioning as post-transcriptional regulatory factors, have been identified as key components of traumatic brain injury (TBI) progression. MicroRNA-21 (miR-21) is a recently identified typical miRNA that is involved in the signaling pathways of inflammation, neuronal apoptosis, reactive gliosis, disruption of blood brain barrier, angiogenesis and recovery process induced by physical exercises in TBI. Hence, miR-21 is now considered as a potential therapeutic target of TBI. We review the correlative literature and research progress regarding the roles of miR-21 in TBI in this article.

MicroRNA-711-Induced Downregulation of Angiopoietin-1 Mediates Neuronal Cell Death

Angiopoietin-1 (Ang-1) is a well-known endothelial growth factor, but its effects on neurons have yet to be elucidated. We show that Ang-1 is rapidly downregulated in the injured brain after controlled cortical impact (CCI), a mouse experimental traumatic brain injury (TBI) model and in etoposide-induced neuronal apoptosis in vitro. Ang-1 treatment inhibits etoposide-induced upregulation of proapoptotic B-cell lymphoma 2 (Bcl-2) family members Noxa, p53 upregulated modulator of apoptosis (Puma), Bcl-2 interacting mediator of cell death (Bim), and Bcl-2-associated X protein (Bax); reduces markers of caspase-dependent (cytochrome c release/caspase activation) and caspase-independent (apoptosis-inducing factor release) pathways; and limits neuronal cell death. Ang-1 treatment phosphorylates receptors Tunica interna endothelial cell kinase 2 (Tie2), and β1-integrin and limits the etoposide-induced decrease in protein kinase B (Akt) activity. Blocking Tie2 and β1-integrin signaling reduces Ang-1 neuroprotective effects. After both TBI and etoposide treatment microRNA (miR)-711 are upregulated, consistent with its putative role as a negative regulator of Ang-1. We show that miR-711 directly targets the Ang-1 messenger RNA (mRNA), decreasing Ang-1 expression. Increased levels of miR-711 and Ang-1 mRNA are found in the RNA-induced silencing complex complex site of miR-mediated degradation of target mRNAs after etoposide treatment and the miR-711mimic downregulates Ang-1. Administration of miR-711 inhibitor elevates Ang-1 after TBI whereas Ang-1 administration increases Akt activation; reduces Puma, Noxa, Bim, and Bax levels; and attenuates caspase-dependent and -independent neuronal apoptosis 24 h after TBI. Ang-1 also attenuates neuronal degeneration, increases gene expression of molecules that maintain blood-brain barrier integrity, and reduces post-traumatic lesion volume/edema 24 h after TBI. Although we only observed short-term neuroprotective effects after Ang-1 administration, miR-711-dependent downregulation of Ang-1, followed by Akt pathway inhibition, may play a role in neuronal cell death after neuronal injury in vitro and after experimental TBI.

MicroRNA Signature of Traumatic Brain Injury: From the Biomarker Discovery to the Point-of-Care

Traumatic brain injury (TBI) is a serious problem that causes high morbidity and mortality around the world. Currently, no reliable biomarkers are used to assess the severity and predict the recovery. Many protein biomarkers were extensively studied for diagnosis and prognosis of different TBI severities such as S-100β, glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), neurofilament light chain (NFL), cleaved tau protein (C-tau), and ubiquitin C-terminal hydrolase-L1 (UCH-L1). However, none of these candidates is currently used in the clinical practice, due to relatively low sensitivity, for the diagnosis of mild TBI (mTBI) or mild to moderate TBI (MMTBI) patients who are clinically well and do not have a detectable intracranial pathology on the scans. MicroRNAs (miRNAs or miRs) are a class of small endogenous molecular regulators, which showed to be altered in different pathologies, including TBI and for this reason, their potential role in diagnosis, prognosis and therapeutic applications, is explored. Promising miRNAs such as miR-21, miR-16 or let-7i were identified as suitable candidate biomarkers for TBI and can differentiate mild from severe TBI. Also, they might represent new potential therapeutic targets. Identification of miRNA signature in tissue or biofluids, for several pathological conditions, is now possible thanks to the introduction of new high-throughput technologies such as microarray platform, Nanostring technologies or Next Generation Sequencing. This review has the aim to describe the role of microRNA in TBI and to explore the most commonly used techniques to identify microRNA profile. Understanding the strengths and limitations of the different methods can aid in the practical use of miRNA profiling for diverse clinical applications, including the development of a point-of-care device.

Clinical-pathological study on β-APP, IL-1β, GFAP, NFL, Spectrin II, 8OHdG, TUNEL, miR-21, miR-16, miR-92 expressions to verify DAI-diagnosis, grade and prognosis

Traumatic brain injury (TBI) is one of the most important death and disability cause, involving substantial costs, also in economic terms, when considering the young age of the involved subject. Aim of this paper is to report a series of patients treated at our institutions, to verify neurological results at six months or survival; in fatal cases we searched for βAPP, GFAP, IL-1β, NFL, Spectrin II, TUNEL and miR-21, miR-16, and miR-92 expressions in brain samples, to verify DAI diagnosis and grade as strong predictor of survival and inflammatory response. Concentrations of 8OHdG as measurement of oxidative stress was performed. Immunoreaction of β-APP, IL-1β, GFAP, NFL, Spectrin II and 8OHdG were significantly increased in the TBI group with respect to control group subjects. Cell apoptosis, measured by TUNEL assay, were significantly higher in the study group than control cases. Results indicated that miR-21, miR-92 and miR-16 have a high predictive power in discriminating trauma brain cases from controls and could represent promising biomarkers as strong predictor of survival, and for the diagnosis of postmortem traumatic brain injury.

Traumatic brain injury: classification, models, and markers

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Due to its high incidence rate and often long-term sequelae, TBI contributes significantly to increasing costs of health care expenditures annually. Unfortunately, advances in the field have been stifled by patient and injury heterogeneity that pose a major challenge in TBI prevention, diagnosis, and treatment. In this review, we briefly discuss the causes of TBI, followed by its prevalence, classification, and pathophysiology. The current imaging detection methods and animal models used to study brain injury are examined. We discuss the potential use of molecular markers in detecting and monitoring the progression of TBI, with particular emphasis on microRNAs as a novel class of molecular modulators of injury and its repair in the neural tissue.

The microRNA miR-21 conditions the brain to protect against ischemic and traumatic injuries

Ischemic and traumatic injuries to CNS remain leading causes of death and disability worldwide, despite decades of research into risk factors, therapies, and preventative measures. Recent studies showed that CNS injuries significantly alter the cerebral microRNAome that impact the secondary brain damage as well as plasticity and recovery. Many microRNA based therapies are currently in various clinical trials for different pathologic conditions indicating their therapeutic potential. In the present review, we discuss the role of miR-21 in acute CNS injuries which is currently thought to be a potent neuroprotective microRNA. We emphasize on the potential of miR-21 in promoting cell and tissue survival and preventing inflammation and apoptosis. We also discussed the role of miR-21 in conditioning the brain to promote ischemic tolerance. Finally, we discussed some of the challenges and difficulties to develop miR-21 as a neuroprotective therapy in humans.

Identification of crucial miRNAs and the targets in renal cortex of hypertensive patients by expression profiles

BACKGROUNDS

Defect in kidney is one major reason of hypertension. The study aimed ao uncovering the regulatory mechanisms of miRNAs and the targets in hypertensive kidney.

METHODS

Gene expression profile of GSE28345 and miRNA expression profile of GSE28283 were downloaded from GEO database. After data preprocessing, differently expressed genes (DEGs) and miRNAs (DE-miRs) were identified using limma package. Then targets of miRNAs were predicted according to information in relevant databases. Function and pathway enrichment analyses were performed for DEGs using DAVID software. Furthermore, protein-protein interaction (PPI) networks were constructed for up- and down-regulated genes, respectively, using the Cytoscape. Additionally, for down-regulated DEGs, the integrated regulatory network was established combining PPI network with the miRNA-mRNA interactions.

RESULTS

As a result, 285 DEGs were identified, including 177 up-regulated and 108 down-regulated genes. Combined with the predicted targets of miRNAs, 22 up-regulated DE-miRs were identified. In the integrated network for down-regulated DEGs, three crucial nodes were identified as ASPN, COL12A1, and SCN2A. ASPN was predicted as target of miR-21 and miR-374b, and COL12A1 was the target of miR-30e, miR-21, and miR-195, while SCN2A was the target of miR-30e, miR-374b, and miR-195. Notably, COL12A1 and ASPN were linked with each other in the network.

CONCLUSION

Three crucial genes were identified in hypertensive kidney, such as COL12A1, ASPN, and SCN2A. ASPN might co-function with COL12A1, and they both might be the targets of miR-21. SCN2A might be a novel target of miR-30e and miR-374b. However, more experiments are needed to validate these results.

Overlapping MicroRNA Expression in Saliva and Cerebrospinal Fluid Accurately Identifies Pediatric Traumatic Brain Injury

To assess the accuracy and physiological relevance of circulating microRNA (miRNA) as a biomarker of pediatric concussion, we compared changes in salivary miRNA and cerebrospinal fluid (CSF) miRNA concentrations after childhood traumatic brain injury (TBI). A case-cohort design was used to compare longitudinal miRNA concentrations in CSF of seven children with severe TBI against three controls without TBI. The miRNAs "altered" in CSF were interrogated in saliva of 60 children with mild TBI and compared with 18 age- and sex-matched controls. The miRNAs with parallel changes (Wilcoxon rank sum test) in CSF and saliva were interrogated for predictive accuracy of TBI status using a multivariate regression technique. Spearman rank correlation identified relationships between miRNAs of interest and clinical features. Functional analysis with DIANA mirPath identified related mRNA pathways. There were 214 miRNAs detected in CSF, and 135 (63%) were also present in saliva. Six miRNAs had parallel changes in both CSF and saliva (miR-182-5p, miR-221-3p, mir-26b-5p, miR-320c, miR-29c-3p, miR-30e-5p). These miRNAs demonstrated an area under the curve of 0.852 for identifying mild TBI status. Three of the miRNAs exhibited longitudinal trends in CSF and/or saliva after TBI, and all three targeted mRNAs related to neuronal development. Concentrations of miR-320c were directly correlated with child and parent reports of attention difficulty. Salivary miRNA represents an easily measured, physiologically relevant, and accurate potential biomarker for TBI. Further studies assessing the influence of orthopedic injury and exercise on peripheral miRNA patterns are needed.

Acute Inflammatory Response Following Increased Blood-Brain Barrier Permeability Induced by Focused Ultrasound is Dependent on Microbubble Dose

Rationale: Focused ultrasound (FUS), in conjunction with circulating microbubbles (MBs), can be used to transiently increase the permeability of the blood-brain barrier (BBB) in a targeted manner, allowing therapeutic agents to enter the brain from systemic circulation. While promising preclinical work has paved the way for the initiation of 3 human trials, there remains concern regarding neuroinflammation following treatment. The aim of this study was to assess the magnitude of this response following sonication and explore the influence of MB dose. Methods: Differential expression of NFκB signaling pathway genes was assessed in rats at 6 h and 4 days following a FUS-mediated increase in BBB permeability. Three sonication schemes were tested: (1) a clinical imaging dose of MBs + peak negative pressure (PNP) controlled by acoustic feedback, (2) 10x clinical imaging dose of MBs + constant PNP of 0.290 MPa, and (3) 10x clinical imaging dose of MBs + PNP controlled by acoustic feedback. Follow-up magnetic resonance imaging (MRI) was performed to assess edema and hemorrhage. Hematoxylin and eosin histology was used to evaluate general tissue health. Results: MB dose has a significant impact on the expression of several key genes involved in acute inflammation and immune activation, including Tnf, Birc3, and Ccl2. At a clinical imaging dose of MBs, there were no significant changes detected in the expression of any NFκB signaling pathway genes. Conversely, a high MB dose resulted in a clear activation of the NFκB signaling pathway, accompanied by edema, neuronal degeneration, neutrophil infiltration, and microhemorrhage. Results also suggest that post-FUS gadolinium enhancement may hold predictive value in assessing the magnitude of inflammatory response. Conclusion: While a significant and damaging inflammatory response was observed at high MB doses, it was demonstrated that FUS can be used to induce increased BBB permeability without an associated upregulation of NFκB signaling pathway gene expression. This emphasizes the importance of employing optimized FUS parameters to mitigate the chances of causing injury to the brain at the targeted locations.

MicroRNA‑21 promotes neurite outgrowth by regulating PDCD4 in a rat model of spinal cord injury

Altered expression levels of microRNA-21 (miRNA-21) have been observed in a series of pathological processes, including cancer and central nervous system injury; however, the involvement of miRNA-21 in the molecular pathophysiology of spinal cord injury (SCI) has not been well documented. The present study examined the expression levels of miRNA-21 and its predicted target genes, programmed cell death 4 (PDCD4) and phosphatase and tensin homolog (PTEN), in rats using quantitative polymerase chain reaction and western blotting to further understand the role of miRNA-21 and the mechanisms underlying repair following SCI. The present study demonstrated that compared with uninjured spinal cords, miRNA-21 expression levels were significantly downregulated in injured spinal cords 4 and 8 h, and 1 day post-SCI, and were significantly upregulated after 3 and 7 days. Conversely, expression levels of PDCD4 and PTEN were significantly decreased at days 3 and 7 post-SCI compared with the control group. miRNA-21 overexpression in monolayer-cultured postnatal rat spinal cord neurons promoted neurite outgrowth and downregulated protein expression levels of PDCD4; however, PTEN protein expression levels were unaltered. To confirm that miRNA-21 directly targets PDCD4, a pRL-CMV luciferase reporter construct was used to detect miRNA-21 interactions with the PDCD4 3′-untranslated region. The results demonstrated that miRNA-21 decreased luciferase activity compared with a rat PDCD4 control reporter. The results of the present study suggested that increased miRNA-21 expression levels following SCI may promote the repair of injured spinal cords by inhibiting the expression of its target gene PDCD4.

Physical exercise as an epigenetic modulator of brain plasticity and cognition

A large amount of evidence has demonstrated the power of exercise to support cognitive function, the effects of which can last for considerable time. An emerging line of scientific evidence indicates that the effects of exercise are longer lasting than previously thought up to the point to affect future generations. The action of exercise on epigenetic regulation of gene expression seem central to building an "epigenetic memory" to influence long-term brain function and behavior. In this review article, we discuss new developments in the epigenetic field connecting exercise with changes in cognitive function, including DNA methylation, histone modifications and microRNAs (miRNAs). The understanding of how exercise promotes long-term cognitive effects is crucial for directing the power of exercise to reduce the burden of neurological and psychiatric disorders.

miR-21a-5p Contributes to Porcine Hemagglutinating Encephalomyelitis Virus Proliferation via Targeting CASK-Interactive Protein1 In vivo and vitro

Porcine hemagglutinating encephalomyelitis virus (PHEV) is a highly neurovirulent coronavirus that can cause nervous symptoms in piglets with muscle tremors, hind limb paralysis, and nystagmus. Whether some factors affect virus replication and proliferation had not been fully understood in the course of nerve damage caused by PHEV infection. In recent years, some reports suggested that miRNA might play a key regulatory role in viral infection. In this study, we found the miR-21a-5p is notably up-regulated in the brains of mice and N2a cells infected with PHEV, and it down-regulated the expression of CASK-interactive protein1 (Caskin1) by directly targeting the 3′-UTR of Caskin1 using a Dual-Luciferase reporter assay. The over-expression of miR-21a-5p or Caskin1 knockdown in the host significantly contributes to PHEV proliferation. Conversely, the silencing of miR-21a-5p by miR-21a-5p inhibitors suppressed the virus proliferation. Taken together, our results indicate that Caskin1 is the direct target gene of miR-21a-5p, and it is advantageous to virus proliferation by down-regulating Caskin1. These findings may help in the development of strategies for therapeutic applications.

Serum microRNAs are non-invasive biomarkers for the presence and progression of subarachnoid haemorrhage

miRNAs are important regulators of translation and have been associated with the pathogenesis of a number of cardiovascular diseases including stroke and may be possible prognostic biomarkers. The purpose of the present study was to determine the expression levels of miRNAs in the sera of subarachnoid haemorrhage (SAH) patients and to evaluate their relationships with the severity and clinical outcome of SAH. Serum samples on day 3 after the onset of SAH were subjected to microarray analysis with Exqion miRCURY^TM LNA array and quantitative PCR analysis. Serum samples from SAH patients (n=60) and healthy controls (n=10) were subjected to quantitative PCR analysis. The severities and clinical outcomes of the SAH patients were evaluated with the WFNS grade and the Modified Rankin Scale (mRS). Three miRNAs, miR-502-5p, miR-1297 and miR-4320 were significantly up-regulated in the sera of SAH patients when compared with the healthy controls. The serum miR-502-5p and miR-1297 levels were significantly higher in the patients with severe SAH and a poor outcome than in those with mild SAH and a good outcome (P<0.05). The areas under the receiver operating characteristic (ROC) curves (AUCs) of miR-502-5p, miR-1297 and miR-4320 to distinguish the SAH patients from the healthy controls were 0.958 (P<0.001), 0.950 (P<0.001) and 0.843 (P<0.001) respectively. Taken together, these results indicate that miR-502-5p and miR-1297 are potentially valuable indicators of the diagnosis, severity and prognosis of SAH, and miR-4320 was a potentially valuable indicator of the diagnosis of SAH.

Mitochondria and microRNA crosstalk in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of long-term impairments in higher cognitive functioning, including deficits in attention and memory. It is well known that some of these persistent deficits are related, in part, to ongoing secondary injury events characterized by pervasive biochemical and pathophysiological stressors, including a rapid and sustained phase of mitochondrial dysfunction. A loss of mitochondrial function impacts a number of important cellular events and we have begun to investigate the novel hypothesis that mitochondria play a critical role in regulating the cellular activity of specific microRNAs in response to cellular demands and stressors. In this special issue report, we summarize briefly the rationale for investigating the crosstalk between mitochondria and microRNA, and provide recent preliminary data suggesting that mitochondria-microRNA interactions are modified in response to TBI-related cellular stressors. We postulate that this interaction is critical for regulating appropriate cellular microRNA responses, which opens up opportunities for therapeutic interventions targeting both mitochondrial function and microRNA activity.

Differential expression of microRNAs in the brains of mice subjected to increasing grade of mild traumatic brain injury

OBJECTIVE

To investigate the effect of heterogeneity in mTBI on miRNA expression in mouse brain and to identify molecular pathways targeted by the modulated miRNAs.

METHODS

A weight drop device was used to induce four increasing grades of mTBI. MiRNA expression was evaluated using TaqMan rodent miRNA arrays. Bioinformatics analysis was done using the DIANA miRPath tool and Ingenuity Pathway Analysis software. Histology of brain sections was evaluated using H&E staining.

RESULTS

No histologic lesions were observed in the brains of injured mice; however, significant modulation in miRNA expression profile was observed. Global miRNA profiling indicated a trend of decrease in the number of modulated miRNAs from 24 hours to day 7 post-injury, except for the most severe grade of mTBI. Canonical pathways like calcium signalling, synaptic pathways and axon guidance pathway were the major targets of the modulated miRNAs. Network correlation analyses indicated an interaction between the modulated miRNAs and putative protein biomarkers of TBI.

CONCLUSIONS

The data demonstrated that varying intensities of mTBI induced a differential miRNA expression profile in the brain post-injury. Pathways such as calcium and synaptic signalling were major targets of modulated miRNAs and may play a role in the pathophysiology of mTBI.