Human traumatic brain injury alters plasma microRNA levels

Circulating microRNAs as biomarkers in traumatic brain injury

Preclinical and clinical studies can be greatly improved through the inclusion of diagnostic, prognostic, predictive or pharmacodynamics biomarkers. Circulating microRNAs (miRNAs) represent highly stable targets that respond to physiological and pathological changes. MicroRNA biomarkers can be detected by highly sensitive and absolutely quantitative methods currently available in most clinical laboratories. Here we review preclinical and clinical studies that have examined circulating miRNAs as potential diagnostic and prognostic biomarkers. We also present data that suggests pharmacodynamics biomarkers can be identified that are associated with neuroprotection in general. Although circulating miRNA can serve as useful tools, it is clear their expression profiles are highly sensitive to changing conditions and are influenced by a broad range of parameters including age, sex, body mass index, injury severity, time of collection, as well as methods of processing, purification and detection. Thus, considerable effort will be required to standardize methods and experimental design conditions before circulating miRNAs can prove useful in a heterologous injury like TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Salivary MicroRNAs: Diagnostic Markers of Mild Traumatic Brain Injury in Contact-Sport

Concussion is difficult to diagnose, particularly when symptoms are atypical or late in presenting. An accurate and timely initial assessment is crucial for clinical management. Cerebral spinal fluid (CSF) and blood markers of traumatic brain injury show promising results but their clinical applicability in concussion has significant limitations. In the study, we explored saliva as a new source of biomarkers of concussion. Saliva samples of concussed players were collected after 48-72 h from concussion and analyzed by high-throughput technologies. A discovery group of 10 concussed rugby professional and semiprofessional athletes and 10 non-concussed matched controls was used for the analysis of 92 inflammatory proteins by the Proseek-Multiplex-Inflammation technology. In addition, saliva samples of 6 concussed and 6 non-concussed athletes were used to screen 800 human microRNAs (miRNAs) by the Nanostring Technology. The results were then validated by RT-qPCR in an enlarged cohort (validation group) comprising 22 concussed athletes. Results showed, no significant variations of the 65 inflammatory proteins detected in saliva between groups but 5 microRNAs, miR-27b-3p (p = 0.016), let-7i-5p (p = 0.001), miR-142-3p (p = 0.008), miR-107 (p = 0.028), miR-135b-5p (p = 0.017) significantly upregulated in concussed athletes. Univariate ROC curve analysis showed that the differentially expressed miRNAs could be considered good classifiers of concussion. Further analyses showed significant correlation between these microRNAs and Reaction Time component of the ImPACT concussion assessment tool. In addition, biocomputation analysis predicted the involvement of these microRNAs in important biological processes that might be related to trauma, such as response to hypoxia, cell death, neurogenesis, axon repair and myelination. Ease of access and non-invasiveness of saliva samples make these biomarkers particularly suitable for concussion assessment.

MicroRNA-based therapeutics in central nervous system injuries

Central nervous system (CNS) injuries, such as stroke, traumatic brain injury (TBI) and spinal cord injury (SCI), are important causes of death and long-term disability worldwide. MicroRNA (miRNA), small non-coding RNA molecules that negatively regulate gene expression, can serve as diagnostic biomarkers and are emerging as novel therapeutic targets for CNS injuries. MiRNA-based therapeutics include miRNA mimics and inhibitors (antagomiRs) to respectively decrease and increase the expression of target genes. In this review, we summarize current miRNA-based therapeutic applications in stroke, TBI and SCI. Administration methods, time windows and dosage for effective delivery of miRNA-based drugs into CNS are discussed. The underlying mechanisms of miRNA-based therapeutics are reviewed including oxidative stress, inflammation, apoptosis, blood-brain barrier protection, angiogenesis and neurogenesis. Pharmacological agents that protect against CNS injuries by targeting specific miRNAs are presented along with the challenges and therapeutic potential of miRNA-based therapies.

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.

Current and Future Applications of Biomedical Engineering for Proteomic Profiling: Predictive Biomarkers in Neuro-Traumatology

This systematic review aims to summarize the impact of nanotechnology and biomedical engineering in defining clinically meaningful predictive biomarkers in patients with traumatic brain injury (TBI), a critical worldwide health problem with an estimated 10 billion people affected annually worldwide. Data were collected through a review of the existing English literature performed on Scopus, MEDLINE, MEDLINE in Process, EMBASE, and/or Cochrane Central Register of Controlled Trials. Only experimental articles revolving around the management of TBI, in which the role of new devices based on innovative discoveries coming from the field of nanotechnology and biomedical engineering were highlighted, have been included and analyzed in this study. Based on theresults gathered from this research on innovative methods for genomics, epigenomics, and proteomics, their future application in this field seems promising. Despite the outstanding technical challenges of identifying reliable biosignatures for TBI and the mixed nature of studies herein described (single cells proteomics, biofilms, sensors, etc.), the clinical implementation of those discoveries will allow us to gain confidence in the use of advanced neuromonitoring modalities with a potential dramatic improvement in the management of those patients.

An update on diagnostic and prognostic biomarkers for traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major worldwide neurological disorder of epidemic proportions. To date, there are still no FDA-approved therapies to treat any forms of TBI. Encouragingly, there are emerging data showing that biofluid-based TBI biomarker tests have the potential to diagnose the presence of TBI of different severities including concussion, and to predict outcome. Areas covered: The authors provide an update on the current knowledge of TBI biomarkers, including protein biomarkers for neuronal cell body injury (UCH-L1, NSE), astroglial injury (GFAP, S100B), neuronal cell death (αII-spectrin breakdown products), axonal injury (NF proteins), white matter injury (MBP), post-injury neurodegeneration (total Tau and phospho-Tau), post-injury autoimmune response (brain antigen-targeting autoantibodies), and other emerging non-protein biomarkers. The authors discuss biomarker evidence in TBI diagnosis, outcome prognosis and possible identification of post-TBI neurodegernative diseases (e.g. chronic traumatic encephalopathy and Alzheimer's disease), and as theranostic tools in pre-clinical and clinical settings. Expert commentary: A spectrum of biomarkers is now at or near the stage of formal clinical validation of their diagnostic and prognostic utilities in the management of TBI of varied severities including concussions. TBI biomarkers could serve as a theranostic tool in facilitating drug development and treatment monitoring.

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.

Association of Salivary MicroRNA Changes With Prolonged Concussion Symptoms

IMPORTANCE

Approximately one-third of children who experience a concussion develop prolonged concussion symptoms. To our knowledge, there are currently no objective or easily administered tests for predicting prolonged concussion symptoms. Several studies have identified alterations in epigenetic molecules known as microRNAs (miRNAs) following traumatic brain injury. No studies have examined whether miRNA expression can detect prolonged concussion symptoms.

OBJECTIVE

To evaluate the efficacy of salivary miRNAs for identifying children with concussion who are at risk for prolonged symptoms.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study at the Penn State Medical Center observed 52 patients aged 7 to 21 years presenting for evaluation of concussion within 14 days of initial head injury, with follow-up at 4 and 8 weeks.

EXPOSURES

All patients had a clinical diagnosis of concussion.

MAIN OUTCOMES AND MEASURES

Salivary miRNA expression was measured at the time of initial clinical presentation in all patients. Patients with a Sport Concussion Assessment Tool (SCAT3) symptom score of 5 or greater on self-report or parent report 4 weeks after injury were designated as having prolonged symptoms.

RESULTS

Of the 52 included participants, 22 (42%) were female, and the mean (SD) age was 14 (3) years. Participants were split into the prolonged symptom group (n = 30) and acute symptom group (n = 22). Concentrations of 15 salivary miRNAs spatially differentiated prolonged and acute symptom groups on partial least squares discriminant analysis and demonstrated functional relationships with neuronal regulatory pathways. Levels of 5 miRNAs (miR-320c-1, miR-133a-5p, miR-769-5p, let-7a-3p, and miR-1307-3p) accurately identified patients with prolonged symptoms on logistic regression (area under the curve, 0.856; 95% CI, 0.822-0.890). This accuracy exceeded accuracy of symptom burden on child (area under the curve, 0.649; 95% CI, 0.388-0.887) or parent (area under the curve, 0.562; 95% CI, 0.219-0.734) SCAT3 score. Levels of 3 miRNAs were associated with specific symptoms 4 weeks after injury; miR-320c-1 was associated with memory difficulty (R, 0.55; false detection rate, 0.02), miR-629 was associated with headaches (R, 0.47; false detection rate, 0.04), and let-7b-5p was associated with fatigue (R, 0.45; false detection rate, 0.04).

CONCLUSIONS AND RELEVANCE

Salivary miRNA levels may identify the duration and character of concussion symptoms. This could reduce parental anxiety and improve care by providing a tool for concussion management. Further validation of this approach is needed.

MicroRNAs as potential prognosticators of neurological outcome in out-of-hospital cardiac arrest patients

Out-of-hospital cardiac arrest survival rates have increased due to advancement in resuscitative measures, yet approximately 90% of survivors ultimately die or have severe neurologic dysfunction caused by ischemic injury. Currently, there are few early prognostic indicators of which patients have possibility of meaningful recovery. This leads to uncertainty for families and clinicians, as well as aggressive, invasive and expensive treatments despite medical futility. Several biomarkers investigated in traumatic brain injury have shown prognostication potential in ischemic brain injury. miRNAs, small noncoding RNAs responsible for gene regulation, have been studied in cardiovascular diseases, and have shown prognostication potential due to tissue specificity and stability in circulation. This review discusses available evidence on miRNAs prognosticating neurological outcomes after out-of-hospital cardiac arrest.

Protein Biomarkers and Neuroproteomics Characterization of Microvesicles/Exosomes from Human Cerebrospinal Fluid Following Traumatic Brain Injury

Recently, there have been emerging interests in the area of microvesicles and exosome (MV/E) released from brain cells in relation to neurodegenerative diseases. However, only limited studies focused on MV/E released post-traumatic brain injury (TBI) as they highlight on the mechanistic roles of released proteins. This study sought to examine if CSF samples from severe TBI patients contain MV/E with unique protein contents. First, nanoparticle tracking analysis determined MV/E from TBI have a mode of 74-98 nm in diameter, while control CSF MV/E have a mode of 99-104 nm. Also, there are more MV/E were isolated from TBI CSF (27.8-33.6 × 10⁸/mL) than from control CSF (13.1-18.5 × 10⁸/mL). Transmission electron microscopy (TEM) visualization also confirmed characteristic MV/E morphology. Using targeted immunoblotting approach, we observed the presence of several known TBI biomarkers such as αII-spectrin breakdown products (BDPs), GFAP, and its BDPs and UCH-L1 in higher concentrations in MV/E from TBI CSF than their counterparts from control CSF. Furthermore, we found presynaptic terminal protein synaptophysin and known exosome marker Alix enriched in MV/E from human TBI CSF. In parallel, we conducted nRPLC-tandem mass spectrometry-based proteomic analysis of two control and two TBI CSF samples. Ninety-one proteins were identified with high confidence in MV/E from control CSF, whereas 466 proteins were identified in the counterpart from TBI CSF. MV/E isolated from human CSF contain cytoskeletal proteins, neurite-outgrowth related proteins, and synaptic proteins, extracellular matrix proteins, and complement protein C1q subcomponent subunit B. Taken together, following severe TBI, the injured human brain released increased number of extracellular microvesicles/exosomes (MV/E) into CSF. These TBI MV/E contain several known TBI biomarkers and previously undescribed brain protein markers. It is also possible that such TBI-specific MV/E might contain cell to cell communication factors related to both cell death signaling a well as neurodegeneration pathways.

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.

MicroRNA Changes in Cerebrospinal Fluid After Subarachnoid Hemorrhage

Supplemental Digital Content is available in the text.

Background and Purpose—

Delayed cerebral ischemia (DCI) accounts for a major part of the morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). MicroRNAs (miRNAs) are pathophysiologically involved in acute cerebral ischemia. This study compared miRNA profiles in cerebrospinal fluid from neurologically healthy patients, as well as SAH patients with and without subsequent development of DCI.

Methods—

In a prospective case–control study of SAH patients treated with external ventricular drainage and neurologically healthy patients, miRNA profiles in cerebrospinal fluid were screened and validated using 2 different high-throughput real-time quantification polymerase chain reaction techniques. The occurrence of DCI was documented in patient charts and subsequently reviewed independently by 2 physicians.

Results—

MiRNA profiles from 27 SAH patients and 10 neurologically healthy patients passed quality control. In the validation, 66 miRNAs showed a relative increase in cerebrospinal fluid from SAH patients compared with neurologically healthy patients (P<0.001); 2 (miR-21 and miR-221) showed a relative increase in SAH patients with DCI compared with those without (P<0.05) in both the screening and validation.

Conclusions—

SAH is associated with marked changes in the cerebrospinal fluid miRNA profile. These changes could be associated to the development of DCI.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01791257.

Serum MicroRNAs Reflect Injury Severity in a Large Animal Model of Thoracic Spinal Cord Injury

Therapeutic development for spinal cord injury is hindered by the difficulty in conducting clinical trials, which to date have relied solely on functional outcome measures for patient enrollment, stratification, and evaluation. Biological biomarkers that accurately classify injury severity and predict neurologic outcome would represent a paradigm shift in the way spinal cord injury clinical trials could be conducted. MicroRNAs have emerged as attractive biomarker candidates due to their stability in biological fluids, their phylogenetic similarities, and their tissue specificity. Here we characterized a porcine model of spinal cord injury using a combined behavioural, histological, and molecular approach. We performed next-generation sequencing on microRNAs in serum samples collected before injury and then at 1, 3, and 5 days post injury. We identified 58, 21, 9, and 7 altered miRNA after severe, moderate, and mild spinal cord injury, and SHAM surgery, respectively. These data were combined with behavioural and histological analysis. Overall miRNA expression at 1 and 3 days post injury strongly correlates with outcome measures at 12 weeks post injury. The data presented here indicate that serum miRNAs are promising candidates as biomarkers for the evaluation of injury severity for spinal cord injury or other forms of traumatic, acute, neurologic injury.

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.

MicroRNAs as diagnostic markers and therapeutic targets for traumatic brain injury

Traumatic brain injury (TBI) is characterized by primary damage to the brain from the external mechanical force and by subsequent secondary injury due to various molecular and pathophysiological responses that eventually lead to neuronal cell death. Secondary brain injury events may occur minutes, hours, or even days after the trauma, and provide valuable therapeutic targets to prevent further neuronal degeneration. At the present time, there is no effective treatment for TBI due, in part, to the widespread impact of numerous complex secondary biochemical and pathophysiological events occurring at different time points following the initial injury. MicroRNAs control a range of physiological and pathological functions such as development, differentiation, apoptosis and metabolism, and may serve as potential targets for progress assessment and intervention against TBI to mitigate secondary damage to the brain. This has implications regarding improving the diagnostic accuracy of brain impairment and long-term outcomes as well as potential novel treatments. Recent human studies have identified specific microRNAs in serum/plasma (miR-425-p, -21, -93, -191 and -499) and cerebro-spinal fluid (CSF) (miR-328, -362-3p, -451, -486a) as possible indicators of the diagnosis, severity, and prognosis of TBI. Experimental animal studies have examined specific microRNAs as biomarkers and therapeutic targets for moderate and mild TBI (e.g., miR-21, miR-23b). MicroRNA profiling was altered by voluntary exercise. Differences in basal microRNA expression in the brain of adult and aged animals and alterations in response to TBI (e.g., miR-21) have also been reported. Further large-scale studies with TBI patients are needed to provide more information on the changes in microRNA profiles in different age groups (children, adults, and elderly).

Aquaporin-4: A Potential Therapeutic Target for Cerebral Edema

Aquaporin-4 (AQP4) is a family member of water-channel proteins and is dominantly expressed in the foot process of glial cells surrounding capillaries. The predominant expression at the boundaries between cerebral parenchyma and major fluid compartments suggests the function of aquaporin-4 in water transfer into and out of the brain parenchyma. Accumulating evidences have suggested that the dysregulation of aquaporin-4 relates to the brain edema resulting from a variety of neuro-disorders, such as ischemic or hemorrhagic stroke, trauma, etc. During edema formation in the brain, aquaporin-4 has been shown to contribute to the astrocytic swelling, while in the resolution phase, it has been seen to facilitate the reabsorption of extracellular fluid. In addition, aquaporin-4-deficient mice are protected from cytotoxic edema produced by water intoxication and brain ischemia. However, aquaporin-4 deletion exacerbates vasogenic edema in the brain of different pathological disorders. Recently, our published data showed that the upregulation of aquaporin-4 in astrocytes probably contributes to the transition from cytotoxic edema to vasogenic edema. In this review, apart from the traditional knowledge, we also introduce our latest findings about the effects of mesenchymal stem cells (MSCs) and microRNA-29b on aquaporin-4, which could provide powerful intervention tools targeting aquaporin-4.

The diagnostic and prognostic value of systems biology research in major traumatic and thermal injury: a review

As secondary complications remain a significant cause of morbidity and mortality amongst hospitalised trauma patients, the need to develop novel approaches by which to identify patients at risk of adverse outcome is becoming increasingly important. Centred on the idea that patients who experience “poor” outcome post trauma elicit a response to injury that is distinct from those who experience “good” outcome, tailored therapeutics is an emerging concept aimed at improving current treatment regimens by promoting patient-specific therapies. Making use of recent advancements in the fields of genomics, proteomics and metabolomics, numerous groups have undertaken a systems-based approach to analysing the acute immune and inflammatory response to major traumatic and thermal injury in an attempt to uncover a single or combination of biomarkers that can identify patients at risk of adverse outcome. Early results are encouraging, with all three approaches capable of discriminating patients with “good” outcome from those who develop nosocomial infections, sepsis and multiple organ failure, with differences apparent in blood samples acquired as early as 2 h post injury. In particular, genomic data is proving to be highly informative, identifying patients at risk of “poor” outcome with a higher degree of sensitivity and specificity than statistical models built upon data obtained from existing anatomical and physiological scoring systems. Here, focussing predominantly upon human-based research, we provide an overview of the findings of studies that have investigated the immune and inflammatory response to major traumatic and thermal injury at the genomic, protein and metabolite level, and consider both the diagnostic and prognostic potential of these approaches.

The potential for animal models to provide insight into mild traumatic brain injury: Translational challenges and strategies

Mild traumatic brain injury (mTBI) is a common health problem. There is tremendous variability and heterogeneity in human mTBI, including mechanisms of injury, biomechanical forces, injury severity, spatial and temporal pathophysiology, genetic factors, pre-injury vulnerability and resilience factors, and clinical outcomes. Animal models greatly reduce this variability and heterogeneity, and provide a means to study mTBI in a rigorous, controlled, and efficient manner. Rodent models, in particular, are time- and cost-efficient, and they allow researchers to measure morphological, cellular, molecular, and behavioral variables in a single study. However, inter-species differences in anatomy, morphology, metabolism, neurobiology, and lifespan create translational challenges. Although the term "mild" TBI is used often in the pre-clinical literature, clearly defined criteria for mild, moderate, and severe TBI in animal models have not been agreed upon. In this review, we introduce current issues facing the mTBI field, summarize the available research methodologies and previous studies in mTBI animal models, and discuss how a translational research approach may be useful in advancing our understanding and management of mTBI.

Analysis of Serum microRNA Expression Profiles and Comparison with Small Intestinal microRNA Expression Profiles in Weaned Piglets

Weaning stress induces tissue injuries and impairs health and growth in piglets, especially during the first week post-weaning. MicroRNAs (miRNAs) play vital roles in regulating stresses and diseases. Our previous study found multiple differentially expressed miRNAs in small intestine of piglets at four days post-weaning. To better understand the roles of miRNAs during weaning stress, we analyzed the serum miRNA expressional profile in weaned piglets (at four days post-weaning) and in suckling piglets (control) of the same age using miRNA microarray technology. We detected a total of 300 expressed miRNAs, 179 miRNAs of which were differentially expressed between the two groups. The miRNA microarray results were validated by RT-qPCR. The biological functions of these differentially expressed miRNAs were predicted by GO terms and KEGG pathway annotations. We identified 10 highly expressed miRNAs in weaned piglets including miR-31, miR-205, and miR-21 (upregulated) and miR-144, miR-30c-5p, miR-363, miR-194a, miR-186, miR-150, and miR-194b-5p (downregulated). Additionally, miR-194b-5p expression was significantly downregulated in serum and small intestine of weaned piglets. Our results suggest that weaning stress affects serum miRNA profiles in piglets. And serum miR-194b-5p levels can reflect its expressional changes in small intestine of piglets by weaning stress.

Epigenetic Modifications of Major Depressive Disorder

Major depressive disorder (MDD) is a chronic disease whose neurological basis and pathophysiology remain poorly understood. Initially, it was proposed that genetic variations were responsible for the development of this disease. Nevertheless, several studies within the last decade have provided evidence suggesting that environmental factors play an important role in MDD pathophysiology. Alterations in epigenetics mechanism, such as DNA methylation, histone modification and microRNA expression could favor MDD advance in response to stressful experiences and environmental factors. The aim of this review is to describe genetic alterations, and particularly altered epigenetic mechanisms, that could be determinants for MDD progress, and how these alterations may arise as useful screening, diagnosis and treatment monitoring biomarkers of depressive disorders.

Circulating microRNAs and sudden cardiac arrest outcomes

AIM

MicroRNAs (miRNAs) have regulatory functions in organs critical in resuscitation from sudden cardiac arrest due to ventricular fibrillation (VF-SCA); therefore, circulating miRNAs may be markers of VF-SCA outcome.

METHODS

We measured candidate miRNAs (N=45) in plasma using qRT-PCR among participants of a population-based VF-SCA study. Participants were randomly selected cases who died in the field (DF, n=15), died in hospital (DH, n=15), or survived to discharge (DC, n=15), and, age-, sex-, and race-matched controls (n=15). MiRNA levels were compared using ANOVA, t-tests, and fold-changes.

RESULTS

Mean age of groups ranged from 66.9 to 69.7. Most participants were male (53-67%) and white (67%). Comparing cases to controls, plasma levels of 17 miRNAs expressed in heart, brain, liver, and other tissues (including miR-29c, -34a, -122, -145, -200a, -210, -499-5p, and -663b) were higher and three non-specific miRNAs lower (miR-221, -330-3p, and -9-5p). Among DH or DC compared with DF cases, levels of two miRNAs (liver-specific miR-122 and non-specific miR-205) were higher and two heart-specific miRNAs (miR-208b and -499-5p) lower. Among DC vs. DF cases, levels of three miRNAs (miR-122, and non-specific miR-200a and -205) were higher and four heart-specific miRNAs (miR-133a, -133b, -208b, and -499-5p) lower. Among DC vs. DH cases, levels of two non-specific miRNAs (miR-135a and -9-3p) were lower.

CONCLUSIONS

Circulating miRNAs expressed in heart, brain, and other tissues differ between VF-SCA cases and controls and are related to resuscitation outcomes. Measurement of miRNAs may clarify mechanisms underlying resuscitation, improve prognostication, and guide development of therapies. Results require replication.

Blood Biomarkers for Evaluation of Perinatal Encephalopathy

Recent research in identification of brain injury after trauma shows many possible blood biomarkers that may help identify the fetus and neonate with encephalopathy. Traumatic brain injury shares many common features with perinatal hypoxic-ischemic encephalopathy. Trauma has a hypoxic component, and one of the 1st physiologic consequences of moderate-severe traumatic brain injury is apnea. Trauma and hypoxia-ischemia initiate an excitotoxic cascade and free radical injury followed by the inflammatory cascade, producing injury in neurons, glial cells and white matter. Increased excitatory amino acids, lipid peroxidation products, and alteration in microRNAs and inflammatory markers are common to both traumatic brain injury and perinatal encephalopathy. The blood-brain barrier is disrupted in both leading to egress of substances normally only found in the central nervous system. Brain exosomes may represent ideal biomarker containers, as RNA and protein transported within the vesicles are protected from enzymatic degradation. Evaluation of fetal or neonatal brain derived exosomes that cross the blood-brain barrier and circulate peripherally has been referred to as the "liquid brain biopsy." A multiplex of serum biomarkers could improve upon the current imprecise methods of identifying fetal and neonatal brain injury such as fetal heart rate abnormalities, meconium, cord gases at delivery, and Apgar scores. Quantitative biomarker measurements of perinatal brain injury and recovery could lead to operative delivery only in the presence of significant fetal risk, triage to appropriate therapy after birth and measure the effectiveness of treatment.

Behavioral, blood, and magnetic resonance imaging biomarkers of experimental mild traumatic brain injury

Repeated mild traumatic brain injuries (mTBI) may lead to serious neurological consequences, especially if re-injury occurs within the period of increased cerebral vulnerability (ICV) triggered by the initial insult. MRI and blood proteomics might provide objective measures of pathophysiological changes in mTBI, and indicate when the brain is no longer in a state of ICV. This study assessed behavioral, MRI, and blood-based markers in a rat model of mTBI. Rats were given a sham or mild fluid percussion injury (mFPI), and behavioral testing, MRI, and blood collections were conducted up to 30 days post-injury. There were cognitive impairments for three days post-mFPI, before normalizing by day 5 post-injury. In contrast, advanced MRI (i.e., tractography) and blood proteomics (i.e., vascular endothelial growth factor) detected a number of abnormalities, some of which were still present 30 days post-mFPI. These findings suggest that MRI and blood proteomics are sensitive measures of the molecular and subtle structural changes following mTBI. Of particular significance, this study identified novel tractography measures that are able to detect mTBI and may be more sensitive than traditional diffusion-tensor measures. Furthermore, the blood and MRI findings may have important implications in understanding ICV and are translatable to the clinical setting.

A Panel of Serum MiRNA Biomarkers for the Diagnosis of Severe to Mild Traumatic Brain Injury in Humans

MicroRNAs (MiRNAs) are small endogenous RNA molecules and have emerged as novel serum diagnostic biomarkers for several diseases due to their stability and detection at minute quantities. In this study, we have identified a serum miRNA signature in human serum samples of mild to severe TBI, which can be used for diagnosis of mild and moderate TBI (MMTBI). Human serum samples of MMTBI, severe TBI (STBI), orthopedic injury and healthy controls were used and miRNA profiling was done using taqman real time PCR. The real time PCR data for the MMTBI, STBI and orthopedic injury was normalized to the control samples which showed upregulation of 39, 37 and 33 miRNAs in MMTBI, STBI and orthopedic injury groups respectively. TBI groups were compared to orthopedic injury group and an up-regulation of 18 and 20 miRNAs in MMTBI and STBI groups was observed. Among these, a signature of 10 miRNAs was found to be present in both MMTBI and STBI groups. These 10 miRNAs were validated in cerebrospinal fluid (CSF) from STBI and four miRNAs were found to be upregulated in CSF. In conclusion, we identified a subset of 10 unique miRNAs which can be used for diagnosis of MMTBI and STBI.

Epigenetic changes following traumatic brain injury and their implications for outcome, recovery and therapy

Traumatic brain injury (TBI) contributes to nearly a third of all injury-related deaths in the United States. For survivors of TBI, depending on severity, patients can be left with devastating neurological disabilities that include impaired cognition or memory, movement, sensation, or emotional function. Despite the efforts to identify novel therapeutics, the only strategy to combat TBI is risk reduction (helmets, seatbelts, removal of fall hazards, etc.). Enormous heterogeneity exists within TBI, and it depends on the severity, the location, and whether the injury was focal or diffuse. Evidence from recent studies support the involvement of epigenetic mechanisms such as DNA methylation, chromatin post-translational modification, and miRNA regulation of gene expression in the post-injured brain. In this review, we discuss studies that have assessed epigenetic changes and mechanisms following TBI, how epigenetic changes might not only be limited to the nucleus but also impact the mitochondria, and the implications of these changes with regard to TBI recovery.

Blood biomarkers for brain injury: What are we measuring?

Accurate diagnosis for mild traumatic brain injury (mTBI) remains challenging, as prognosis and return-to-play/work decisions are based largely on patient reports. Numerous investigations have identified and characterized cellular factors in the blood as potential biomarkers for TBI, in the hope that these factors may be used to gauge the severity of brain injury. None of these potential biomarkers have advanced to use in the clinical setting. Some of the most extensively studied blood biomarkers for TBI include S100β, neuron-specific enolase, glial fibrillary acidic protein, and Tau. Understanding the biological function of each of these factors may be imperative to achieve progress in the field. We address the basic question: what are we measuring? This review will discuss blood biomarkers in terms of cellular origin, normal and pathological function, and possible reasons for increased blood levels. Considerations in the selection, evaluation, and validation of potential biomarkers will also be addressed, along with mechanisms that allow brain-derived proteins to enter the bloodstream after TBI. Lastly, we will highlight perspectives and implications for repetitive neurotrauma in the field of blood biomarkers for brain injury.

microRNA-22 attenuates neuronal cell apoptosis in a cell model of traumatic brain injury

Traumatic brain injury (TBI) is a major cause of injury-related deaths, and the mechanism of TBI has become a research focus, but little is known about the mechanism of microRNAs in TBI. The aim of this study is the role of microRNA-22 (miR-22) in TBI-induced neuronal cell apoptosis. Rat cortical neurons were cultured and the TBI model was induced by scratch injury in vitro, before which miR-22 level was altered by transfection of agomir or antagomir. Lactate dehydrogenase (LDH) release and TUNEL assays were performed to examine neuronal cell injury and apoptosis. The activity of caspase 3 (CASP3) and level changes of several apoptosis factors including B-cell lymphoma 2 (BCL2), BCL2-associated X protein (BAX), phosphatase and tensin homolog (PTEN) and v-AKT murine thymoma viral oncogene homolog 1 (AKT1) were detected. Results showed that TBI model cells possessed a downregulated miR-22 level (P < 0.001) and more LDH release and apoptotic cells indicating the aggravated neuronal cell injury and apoptosis induced by TBI. miR-22 agomir attenuated neuronal cell injury and apoptosis of the TBI model. It also caused the corresponding changes in CASP3 activity and other apoptosis factors, with cleaved CASP3, BAX and PTEN inhibited and BCL2 and phosphorylated AKT1 promoted, while miR-22 antagomir had the opposite effects. So miR-22 has neuroprotective roles of attenuating neuronal cell injury and apoptosis induced by TBI, which may be associated with its regulation on apoptosis factors. This study reveals miR-22 as a potential approach to TBI treatment and detailed mechanism remains to be uncovered.

Sports-related brain injuries: connecting pathology to diagnosis

Brain injuries are becoming increasingly common in athletes and represent an important diagnostic challenge. Early detection and management of brain injuries in sports are of utmost importance in preventing chronic neurological and psychiatric decline. These types of injuries incurred during sports are referred to as mild traumatic brain injuries, which represent a heterogeneous spectrum of disease. The most dramatic manifestation of chronic mild traumatic brain injuries is termed chronic traumatic encephalopathy, which is associated with profound neuropsychiatric deficits. Because chronic traumatic encephalopathy can only be diagnosed by postmortem examination, new diagnostic methodologies are needed for early detection and amelioration of disease burden. This review examines the pathology driving changes in athletes participating in high-impact sports and how this understanding can lead to innovations in neuroimaging and biomarker discovery.

Circulating MicroRNAs as Potential Biomarkers for Traumatic Brain Injury-Induced Hypopituitarism

Traumatic brain injury (TBI), a worldwide public health problem, has recently been recognized as a common cause of pituitary dysfunction. Circulating microRNAs (miRNAs) present in the sera are characteristically altered in many pathological conditions and have been used as diagnostic markers for specific diseases. It is with this goal that we planned to study miRNA expression in patients with TBI-induced hypopituitarism. Thirty-eight patients (27 male, 11 female; mean age, 43 ± 18 years) who had been admitted to the neurosurgery intensive care unit due to TBI were included in the acute phase of the study. In the chronic phase, miRNA expression profile blood samples were drawn from 25 patients who had suffered TBI 5 years ago. In the acute phase (on Days 1, 7, and 28), a substantial amount of patients (26%, 40%, and 53%; respectively) had hypopituitarism (acute adrenocorticotropic hormone deficiency). In the chronic phase eight of 25 patients (32%) had TBI-induced-hypopituitarism. Forty-seven age-gender-similar healthy controls (25 male, 22 female, mean age: 41 ± 14 years) were included in the study. In order to identify potential candidate miRNA/miRNAs whose levels had been altered in response to TBI-induced hypopituitarism, 740 miRNA expression analyses were performed in the sera of TBI patients by high throughput real-time polymerase chain reaction. Statistical analyses showed that miRNA-126-3p (miR-126-3p) and miRNA-3610 (miR-3610) were detected in the sera of patients who developed hypopituitarism on the 1st, 7th, and 28th days, and in the 5th year following TBI. In addition, miRNA-3907 showed statistically significant and constant dynamic changes on the 1st, 7th, and 28th days, and in the 5th year in the patients with TBI. Our results indicated that altered expression of miR-126-3p and miR-3610 may play an important role in the development of TBI-induced hypopituitarism.

MiR-630 Inhibits Endothelial-Mesenchymal Transition by Targeting Slug in Traumatic Heterotopic Ossification

Heterotopic ossification (HO) is the abnormal formation of mature bone in extraskeletal soft tissues that occurs as a result of inflammation caused by traumatic injury or associated with genetic mutation. Despite extensive research to identify the source of osteogenic progenitors, the cellular origins of HO are controversial and the underlying mechanisms, which are important for the early detection of HO, remain unclear. Here, we used in vitro and in vivo models of BMP4 and TGF-β2-induced HO to identify the cellular origin and the mechanisms mediating the formation of ectopic bone in traumatic HO. Our results suggest an endothelial origin of ectopic bone in early phase of traumatic HO and indicate that the inhibition of endothelial-mesenchymal transition by miR-630 targeting Slug plays a role in the formation of ectopic bone in HO. A matched case-control study showed that miR-630 is specifically downregulated during the early stages of HO and can be used to distinguish HO from other processes leading to bone formation. Our findings suggest a potential mechanism of post-traumatic ectopic bone formation and identify miR-630 as a potential early indicator of HO.

Evidence and potential in vivo functions for biofluid miRNAs: From expression profiling to functional testing: Potential roles of extracellular miRNAs as indicators of physiological change and as agents of intercellular information exchange

A controversial hypothesis in RNA biology is that extracellular microRNAs (miRNAs), including those in biofluids, have non-cell-autonomous activities. Several studies have characterized biofluid miRNA profiles in healthy or diseased individuals but generally have failed to identify distinct disease signatures. It remains unclear whether alterations in fluid miRNA levels are simply indicators of physiological change or whether miRNAs are taken up by new cells at concentrations sufficient to affect gene expression. There are limitations to biofluid miRNA studies performed to date: methodology for isolating and quantifying biofluid miRNAs is not standardized across studies; mechanistic details of miRNA release and uptake are incomplete; and efforts to assess non-cell-autonomous effects of extracellular miRNAs have employed predominantly in vitro strategies. We describe controversies and questions that need to be addressed to test possible in vivo roles of extracellular miRNAs and propose model organisms with rich genetic toolkits for carrying out in vivo functional analyses.

Elevated serum miR-93, miR-191, and miR-499 are noninvasive biomarkers for the presence and progression of traumatic brain injury

The levels of miR-93, miR-191, and miR-499 have been reported to be up-regulated in the tissues of experimental traumatic brain injury (TBI) rat models. However, the clinical diagnostic and prognostic values of the serum signatures of these 3 miRNAs in TBI remain unclear. The purpose of this study was to determine the expression levels of these 3 microRNAs (miRNAs) in the sera of TBI patients and to evaluate their relationships with the severity and clinical outcome of TBI. The serum levels of these miRNAs were assessed in TBI patients (n = 76) and healthy controls (n = 38) by quantitative reverse-transcription PCR. The severities and clinical outcomes of the TBI patients were evaluated with the Glasgow coma scale and the Glasgow outcome scale. The serum miR-93, miR-191, and miR-499 levels were significantly increased in the TBI patients compared with the controls at all examined time points, and these levels were significantly higher in the patients with severe TBI than in those with moderate or mild TBI (p < 0.05). The serum miR-93, miR-191, and miR-499 levels were significantly higher in the patients with a poor outcome than in those with a good outcome (p < 0.05). The AUCs of miR-93, miR-191, and miR-499 for distinguishing the TBI patients from the healthy controls were 1.000 (p < 0.001), 0.727 (p < 0.001) and 0.801 (p < 0.001), respectively. Interestingly, the AUCs of miR-93, miR-191, and miR-499 for distinguishing the mild TBI patients from the healthy controls were 1.000 (p < 0.001), 0.742 (p < 0.001) and 0.819 (p < 0.001), respectively. Taken together, these results indicate that miR-93, miR-191, and miR-499 are potentially valuable indicators of the diagnosis, severity, and prognosis of TBI. Our study showed that the serum levels of miR-93, miR-191, and miR-499 are all increased in traumatic brain injury (TBI) patients. Their serum levels are associated with TBI severity and outcome, which suggest that these miRNAs play important roles in the pathogenesis and progression of TBI. We think these findings should provide a new strategy for the diagnostic, prognostic, and treatment of TBI.

Pathogenetic and therapeutic applications of microRNAs in major depressive disorder

As a class of noncoding RNAs, microRNAs (miRNAs) regulate gene expression by inhibiting translation of messenger RNAs. These miRNAs have been shown to play a critical role in higher brain functioning and actively participate in synaptic plasticity. Pre-clinical evidence demonstrates that expression of miRNAs is differentially altered during stress. On the other hand, depressed individuals show marked changes in miRNA expression in brain. MiRNAs are also target of antidepressants and electroconvulsive therapy. Moreover, these miRNAs are present in circulating blood and can be easily detected. Profiling of miRNAs in blood plasma/serum provides evidence that determination of miRNAs in blood can be used as possible diagnostic and therapeutic tool. In this review article, these aspects are critically reviewed and the role of miRNAs in possible etiopathogenesis and therapeutic implications in the context of major depressive disorder is discussed.

Current status of fluid biomarkers in mild traumatic brain injury

Mild traumatic brain injury (mTBI) affects millions of people annually and is difficult to diagnose. Mild injury is insensitive to conventional imaging techniques and diagnoses are often made using subjective criteria such as self-reported symptoms. Many people who sustain a mTBI develop persistent post-concussive symptoms. Athletes and military personnel are at great risk for repeat injury which can result in second impact syndrome or chronic traumatic encephalopathy. An objective and quantifiable measure, such as a serum biomarker, is needed to aid in mTBI diagnosis, prognosis, return to play/duty assessments, and would further elucidate mTBI pathophysiology. The majority of TBI biomarker research focuses on severe TBI with few studies specific to mild injury. Most studies use a hypothesis-driven approach, screening biofluids for markers known to be associated with TBI pathophysiology. This approach has yielded limited success in identifying markers that can be used clinically, additional candidate biomarkers are needed. Innovative and unbiased methods such as proteomics, microRNA arrays, urinary screens, autoantibody identification and phage display would complement more traditional approaches to aid in the discovery of novel mTBI biomarkers.

Temporal Profile of MicroRNA Expression in Contused Cortex after Traumatic Brain Injury in Mice

MicroRNAs (miRNAs) were recently identified as important regulators of gene expression under a wide range of physiological and pathophysiological conditions. Thus, they may represent a novel class of molecular targets for the management of traumatic brain injury (TBI). In this study, we investigated the temporal profile of miRNA expression during the development of secondary brain damage after experimental TBI. For this purpose, we used a controlled cortical impact model in C57Bl/6 mice (n = 6) to induce a cortical contusion and analyzed miRNA expression in the traumatized cortex by microarray analysis during the development of secondary contusion expansion-i.e., at 1, 6, and 12 h after TBI. Of a total 780 mature miRNA sequences analyzed, 410 were detected in all experimental groups. Of these, 158 miRNAs were significantly upregulated or downregulated in TBI compared with sham-operated animals, and 52 miRNAs increased more than twofold. We validated the upregulation of five of the most differentially expressed miRNAs (miR-21*, miR-144, miR-184, miR-451, miR-2137) and the downregulation of four of the most differentially expressed miRNAs (miR-107, miR-137, miR-190, miR-541) by quantitative polymerase chain reaction (qPCR). miR-2137, the most differentially expressed miRNA after TBI, was further investigated by in situ hybridization and was found to be upregulated in neurons within the traumatic penumbra. This study gives a comprehensive picture of miRNA expression levels during secondary contusion expansion after TBI and may pave the way for the identification of novel targets for the management of brain trauma.

MicroRNAs in spent blastocyst culture medium are derived from trophectoderm cells and can be explored for human embryo reproductive competence assessment

OBJECTIVE

To assess whether extracellular microRNAs (miRNAs) can be accurately profiled from spent blastocyst culture media (SBM) and used as embryonic biomarkers.

DESIGN

Prospective cohort study.

SETTING

Private and academic in vitro fertilization centers.

PATIENT(S)

Inner cell mass-free trophectoderm (TE) samples and their relative SBM from five good-quality human blastocysts.

INTERVENTION(S)

Protocol for miRNA purification and analysis based on quantitative polymerase chain reaction set and validated on human embryonic stem cells (hESCs) and on SBM with and without biological variability.

MAIN OUTCOMES MEASURE(S)

Analysis of miRNAs in culture media in relation with TE cells and comparison of miRNA profiles between implanted and unimplanted euploid blastocysts.

RESULT(S)

Culture media from embryos in the cleavage, morula, and blastocyst stages were collected to investigate the presence of miRNAs. The SBM were prospectively collected from euploid implanted (n = 25) and unimplanted blastocysts (n = 28) for comparison. We hypothesized that human embryos secrete miRNAs in culture media that can be used as biomarkers. The comparative analysis of TE and SBM samples revealed that 96.6% (57 of 59; 95 CI, 88.3-99.6) of the miRNAs detected in the SBM were expressed from TE cells, suggesting a TE origin. The culture media collected from cleavage and morula stage embryos showed a pattern similar to blanks, suggesting that miRNAs profiling from spent culture media applies only for blastocysts. MicroRNAs analysis of SBM from euploid implanted and unimplanted blastocysts highlighted two miRNAs (miR-20a, miR-30c) that showed increased concentrations in the former and were predicted in silico to be involved in 23 implantation-related pathways.

CONCLUSION(S)

MicroRNAs secreted from human blastocysts in culture media can be profiled with high reproducibility, and this approach can be further explored for noninvasive embryo selection.

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

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

Specific miRNA and its target in neutrophils after traumatic injury

Traumatic injury is a leading cause of mortality and morbidity. MicroRNAs (miRNAs) regulate the cellular responses when traumatic injury occurs. Previously, we reported that miR-3945, miR-125a-5p, miR-363-3p, and miR-150-5p were significantly altered in neutrophils of patients who suffered traumatic injury. In the present study, by comparing neutrophils of patients suffering from major trauma with neutrophils of patients with a inflammatory disease, we found that the variation trend of miR-150-5p was relatively different in the process of these two diseases. Gene Ontology and pathway analysis of miR-150-5p revealed that it may activate the mitogen-activated protein kinase and Toll-like receptor signaling pathways and cell adhesion molecules when the traumatic injury occurs. In addition, protein kinase C alpha (PRKCA) was also identified as a direct target of miR-150-5p by establishing a miRNA-mRNA network, and this target was validated via dual-luciferase reporter and western blot analysis. Our results suggested that the expression of miR-150-5p was down-regulated in neutrophils after a major traumatic injury. miR-150-5p and its identified target PRKCA play important roles in the development of traumatic process.