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

Evaluation of a Set of miRNAs in 26 Cases of Fatal Traumatic Brain Injuries

In forensic medicine, identifying novel biomarkers for use as diagnostic tools to ascertain causes of death is challenging because of sample degradation. To that aim, a cohort (n = 26) of fatal traumatic brain injuries (TBIs) were tested for three candidate miRNAs (namely, miR-124-3p, miR-138-5p, and miR144-3p). For each case, three FFPE specimens (coup area (CA), contrecoup area (CCA), and the corpus callosum (CC)) were investigated, whereas the FFPE brain tissues of 45 subjects (deceased due to acute cardiovascular events) were used as controls. Relative quantification via the ∆∆Ct method returned significantly higher expression levels of the three candidate miRNAs (p < 0.01) in the TBI cases. No difference was detected in the expression levels of any miRNA investigated in the study among the CA, CCA, and CC. Furthermore, the analyzed miRNAs were unrelated to the TBI samples' post-mortem intervals (PMIs). On the contrary, has-miR-124-3p ahashsa-miR-144-3p were significantly correlated (p < 0.01) with the agonal time in TBI deaths. Since the RNA was highly degraded in autoptic FFPE tissues, it was impossible to analyze the mRNA targets of the miRNAs investigated in the present study, highlighting the necessity of standardizing pre-analytical processes even for autopsy tissues.

Traumatic MicroRNAs: Deconvolving the Signal After Severe Traumatic Brain Injury

History of traumatic brain injury (TBI) represents a significant risk factor for development of dementia and neurodegenerative disorders in later life. While histopathological sequelae and neurological diagnostics of TBI are well defined, the molecular events linking the post-TBI signaling and neurodegenerative cascades remain unknown. It is not only due to the brain's inaccessibility to direct molecular analysis but also due to the lack of well-defined and highly informative peripheral biomarkers. MicroRNAs (miRNAs) in blood are promising candidates to address this gap. Using integrative bioinformatics pipeline including miRNA:target identification, pathway enrichment, and protein-protein interactions analysis we identified set of genes, interacting proteins, and pathways that are connected to previously reported peripheral miRNAs, deregulated following severe traumatic brain injury (sTBI) in humans. This meta-analysis revealed a spectrum of genes closely related to critical biological processes, such as neuroregeneration including axon guidance and neurite outgrowth, neurotransmission, inflammation, proliferation, apoptosis, cell adhesion, and response to DNA damage. More importantly, we have identified molecular pathways associated with neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, based on purely peripheral markers. The pathway signature after acute sTBI is similar to the one observed in chronic neurodegenerative conditions, which implicates a link between the post-sTBI signaling and neurodegeneration. Identified key hub interacting proteins represent a group of novel candidates for potential therapeutic targets or biomarkers.

An Overview on the Use of miRNAs as Possible Forensic Biomarkers for the Diagnosis of Traumatic Brain Injury

Determining the cause of death is one of the main goals of forensic pathology. However, conditions can occur in which common approaches—external inspection, autopsy, histology, etc.—might not be conclusive. With the advancement of molecular biology, several investigative techniques have been developed over the years, and the application as approaches complementary to routine procedures has proved useful in these cases. In this context, microRNA (miRNA) profiling has attracted increasing interest due to these molecules’ ability to regulate physiological and pathological processes. The evidence of differential miRNA expression in both animal models and human samples of traumatic brain injury (TBI) has laid the basis for comprehension of the underlying pathophysiological mechanisms, thus allowing us to identify some of them as possible TBI diagnostic biomarkers. The present narrative review aims to explore the primary miRNAs involved in the mechanisms underlying TBI, which could be considered for future evaluation as possible markers in a post mortem setting.

YTHDF1 Attenuates TBI-Induced Brain-Gut Axis Dysfunction in Mice

The brain-gut axis (BGA) is a significant bidirectional communication pathway between the brain and gut. Traumatic brain injury (TBI) induced neurotoxicity and neuroinflammation can affect gut functions through BGA. N⁶-methyladenosine (m⁶A), as the most popular posttranscriptional modification of eukaryotic mRNA, has recently been identified as playing important roles in both the brain and gut. However, whether m⁶A RNA methylation modification is involved in TBI-induced BGA dysfunction is not clear. Here, we showed that YTHDF1 knockout reduced histopathological lesions and decreased the levels of apoptosis, inflammation, and oedema proteins in brain and gut tissues in mice after TBI. We also found that YTHDF1 knockout improved fungal mycobiome abundance and probiotic (particularly Akkermansia) colonization in mice at 3 days post-CCI. Then, we identified the differentially expressed genes (DEGs) in the cortex between YTHDF1-knockout and WT mice. These genes were primarily enriched in the regulation of neurotransmitter-related neuronal signalling pathways, inflammatory signalling pathways, and apoptotic signalling pathways. This study reveals that the ITGA6-mediated cell adhesion molecule signalling pathway may be the key feature of m⁶A regulation in TBI-induced BGA dysfunction. Our results suggest that YTHDF1 knockout could attenuate TBI-induced BGA dysfunction.

Serum microRNAs associated with concussion in football players

Mild Traumatic Brain Injury (mild TBI)/concussion is a common sports injury, especially common in football players. Repeated concussions are thought to lead to long-term brain damage including chronic traumatic encephalopathy (CTE). With the worldwide growing interest in studying sport-related concussion the search for biomarkers for early diagnosis and progression of neuronal injury has also became priority. MicroRNAs are short, non-coding RNAs that regulate gene expression post-transcriptionally. Due to their high stability in biological fluids, microRNAs can serve as biomarkers in a variety of diseases including pathologies of the nervous system. In this exploratory study, we have evaluated changes in the expression of selected serum miRNAs in collegiate football players obtained during a full practice and game season. We found a miRNA signature that can distinguish with good specificity and sensitivity players with concussions from non-concussed players. Furthermore, we found miRNAs associated with the acute phase (let-7c-5p, miR-16-5p, miR-181c-5p, miR-146a-5p, miR-154-5p, miR-431-5p, miR-151a-5p, miR-181d-5p, miR-487b-3p, miR-377-3p, miR-17-5p, miR-22-3p, and miR-126-5p) and those whose changes persist up to 4 months after concussion (miR-17-5p and miR-22-3p).

The Role of Extracellular Vesicles in Optic Nerve Injury: Neuroprotection and Mitochondrial Homeostasis

Stem cell therapies hold great promise as alternative treatments for incurable optic nerve disorders. Although mesenchymal stem cells exhibit various tissue regeneration and recovery capabilities that may serve as valuable therapies, the clinical applications remain limited. Thus, we investigated the utility of extracellular vesicles (EVs) from human placenta-derived mesenchymal stem cells (hPSCs) in this context. Hypoxically preconditioned hPSCs (HPPSCs) were prepared via short-term incubation under 2.2% O2 and 5.5% CO2. The EVs were then isolated. R28 cells (retinal precursor cells) were exposed to CoCl2 and treated with EVs for 24 h. Cell proliferation and regeneration were measured using a BrdU assay and immunoblotting; ATP quantification revealed the extent of the mitochondrial function. The proteome was determined via liquid chromatography-tandem mass spectroscopy. Differentially expressed proteins (DEPs) were detected and their interactions identified. HPPSC_EVs functions were explored using animal models of optic nerve compression. HPPSC_EVs restored cell proliferation and mitochondrial quality control in R28 cells damaged by CoCl2. We identified DEPs (p < 0.05) that aided recovery. The mitochondrial DEPs included LONP1; PARK7; VDAC1, 2, and 3; HSPD1; and HSPA9. EVs regulated the levels of mitophagic proteins in R28 cells injured by hypoxia; the protein levels did not increase in LONP1 knockdown cells. LONP1 is a key mediator of the mitophagy that restores mitochondrial function after hypoxia-induced optic nerve injury.

Associations between lipids in selected brain regions, plasma miRNA, and behavioral and cognitive measures following 28Si ion irradiation

The space radiation environment consists of multiple species of charged particles, including 28Si ions, that may impact brain function during and following missions. To develop biomarkers of the space radiation response, BALB/c and C3H female and male mice and their F2 hybrid progeny were irradiated with 28Si ions (350 MeV/n, 0.2 Gy) and tested for behavioral and cognitive performance 1, 6, and 12 months following irradiation. The plasma of the mice was collected for analysis of miRNA levels. Select pertinent brain regions were dissected for lipidomic analyses and analyses of levels of select biomarkers shown to be sensitive to effects of space radiation in previous studies. There were associations between lipids in select brain regions, plasma miRNA, and cognitive measures and behavioral following 28Si ion irradiation. Different but overlapping sets of miRNAs in plasma were found to be associated with cognitive measures and behavioral in sham and irradiated mice at the three time points. The radiation condition revealed pathways involved in neurodegenerative conditions and cancers. Levels of the dendritic marker MAP2 in the cortex were higher in irradiated than sham-irradiated mice at middle age, which might be part of a compensatory response. Relationships were also revealed with CD68 in miRNAs in an anatomical distinct fashion, suggesting that distinct miRNAs modulate neuroinflammation in different brain regions. The associations between lipids in selected brain regions, plasma miRNA, and behavioral and cognitive measures following 28Si ion irradiation could be used for the development of biomarker of the space radiation response.

Plasma miR-9-3p and miR-136-3p as Potential Novel Diagnostic Biomarkers for Experimental and Human Mild Traumatic Brain Injury

Noninvasive, affordable circulating biomarkers for difficult-to-diagnose mild traumatic brain injury (mTBI) are an unmet medical need. Although blood microRNA (miRNA) levels are reportedly altered after traumatic brain injury (TBI), their diagnostic potential for mTBI remains inconclusive. We hypothesized that acutely altered plasma miRNAs could serve as diagnostic biomarkers both in the lateral fluid percussion injury (FPI) model and clinical mTBI. We performed plasma small RNA-sequencing from adult male Sprague-Dawley rats (n = 31) at 2 days post-TBI, followed by polymerase chain reaction (PCR)-based validation of selected candidates. miR-9a-3p, miR-136-3p, and miR-434-3p were identified as the most promising candidates at 2 days after lateral FPI. Digital droplet PCR (ddPCR) revealed 4.2-, 2.8-, and 4.6-fold elevations in miR-9a-3p, miR-136-3p, and miR-434-3p levels (p < 0.01 for all), respectively, distinguishing rats with mTBI from naïve rats with 100% sensitivity and specificity. DdPCR further identified a subpopulation of mTBI patients with plasma miR-9-3p (n = 7/15) and miR-136-3p (n = 5/15) levels higher than one standard deviation above the control mean at <2 days postinjury. In sTBI patients, plasma miR-9-3p levels were 6.5- and 9.2-fold in comparison to the mTBI and control groups, respectively. Thus, plasma miR-9-3p and miR-136-3p were identified as promising biomarker candidates for mTBI requiring further evaluation in a larger patient population.

Exosomal MicroRNAs in Military Personnel with Mild Traumatic Brain Injury: Preliminary Results from the Chronic Effects of Neurotrauma Consortium Biomarker Discovery Project

Chronic symptoms after mild traumatic brain injury (mTBI) are common among veterans and service members, and represent a significant source of morbidity, with those who sustain multiple mTBIs at greatest risk. Exosomal micro-RNAs (miRNAs), mediators of intercellular communication, may be involved in chronic TBI symptom persistence. Exosomal miRNA (exomiR) was extracted from 153 participants enrolled in the Chronic Effect of Neurotrauma Consortium (CENC) longitudinal study (no TBI, n = 35; ≥ 3 mTBIs (rTBI), n = 45; 1-2 mTBIs, n = 73). Analyses were performed with nCounter® Human miRNA Expression Panels and Ingenuity Pathway Analysis (IPA) for identification of gene networks associated with TBI. Generalized linear models were used to analyze the predictive value of exomiR dysregulation and remote neurobehavioral symptoms. Compared with controls, there were 17 dysregulated exomiRs in the entire mTBI group and 32 dysregulated exomiRs in the rTBI group. Two miRNAs, hsa-miR-139-5p and hsa-miR-18a-5p, were significantly differentially expressed in the rTBI and 1-2 mTBI groups. IPA analyses showed that these dysregulated exomiRs correlated with pathways of inflammatory regulation, neurological disease, and cell development. Within the rTBI group, exomiRs correlated with gene activity for hub-genes of tumor protein TP53, insulin-like growth factor 1 receptor, and transforming growth factor beta. TBI history and neurobehavioral symptom survey scores negatively and significantly correlated with hsa-miR-103a-3p expression. Participants with remote mTBI have distinct exomiR profiles, which are significantly linked to inflammatory and neuronal repair pathways. These profiles suggest that analysis of exosomal miRNA expression may provide novel insights into the underlying pathobiology of chronic TBI symptom persistence.

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.

Brain Perfusion Mediates the Relationship Between miRNA Levels and Postural Control

Transcriptomics, regional cerebral blood flow (rCBF), and a virtual reality-based spatial motor task were integrated using mediation analysis in a novel demonstration of “imaging omics.” Data collected in National Collegiate Athletic Association (NCAA) Division I football athletes cleared for play before in-season training showed significant relationships in 1) elevated levels of miR-30d and miR-92a to elevated putamen rCBF, 2) elevated putamen rCBF to compromised Balance scores, and 3) compromised Balance scores to elevated microRNA (miRNA) levels. rCBF acted as a consistent mediator variable (Sobel’s test P < 0.05) between abnormal miRNA levels and compromised Balance scores. Given the involvement of these miRNAs in inflammation and immune function and that vascular perfusion is a component of the inflammatory response, these findings support a chronic inflammatory model in these athletes with 11 years of average football exposure. rCBF, a systems biology measure, was necessary for miRNA to affect behavior.

UBA2 activates Wnt/β-catenin signaling pathway during protection of R28 retinal precursor cells from hypoxia by extracellular vesicles derived from placental mesenchymal stem cells

Background

Stem cell transplantation has been proposed as an alternative treatment for intractable optic nerve disorders characterized by irrecoverable loss of cells. Mesenchymal stem cells, with varying tissue regeneration and recovery capabilities, are being considered for potential cell therapies. To overcome the limitations of cell therapy, we isolated exosomes from human placenta-derived mesenchymal stem cells (hPMSCs) and investigated their therapeutic effects in R28 cells (retinal precursor cells) exposed to CoCl₂.

Method

After 9 h of exposure to CoCl₂, the hypoxic damaged R28 cells were divided into the non-treatment group (CoCl₂ + R28 cells) and treatment group (CoCl₂ + R28 cells treated with exosome). Immunoblot analysis was performed for Pcna, Hif-1α, Vegf, Vimentin, Thy-1, Gap43, Ermn, Neuroflament, Wnt3a, β-catenin, phospo-GSK3β, Lef-1, UBA2, Skp1, βTrcp, and ubiquitin. The proteomes of each group were analyzed by liquid chromatography/tandem mass (LC-MS/MS) spectrometry. Differentially expressed proteins (DEPs) were detected by label-free quantification, and the interactions of the proteins were examined through signal transduction pathway and gene ontology analysis.

Result

We observed that exosome could significantly recover proliferation damaged by CoCl₂ treatment. In addition, the treatment group presented the decreased expression of Hif-1α protein (P < 0.05) and increased expression of proliferation marker, Pcna, and nerve regeneration-related factors such as Vimentin, Thy-1, and Neuroflament (P < 0.05) compared with the non-treatment group. In total, 200 DEPs were identified in the non-treatment group and treatment group (fold change ≥ 2, p < 0.05). Catenin and ubiquitin systems (UBA2, UBE2E3, UBE2I) were found in both the DEP lists of downregulated proteins from the non-treatment group and upregulated proteins from the treatment group. The mRNA expressions of ubiquitin systems were significantly decreased under hypoxic conditions. Moreover, UBA2 and Wnt/β-catenin protein were associated with the rescue of the hypoxic damaged R28 cells. Using a siRNA system, we could find it out that hPMSC exosomes could not repair altered expressions of target proteins by CoCl₂ in lacking UBA2 R28 cells.

Conclusion

This study reported that hypoxic damaged expression of regeneration markers in R28 cells was significantly recovered by hPMSC exosomes. We could also demonstrate that UBA2 played a key role in activating the Wnt/β-catenin signaling pathway during protection of hypoxic damaged R28 cells, induced by hPMSC exosomes.

miR-142-3p Expression Is Predictive for Severe Traumatic Brain Injury (TBI) in Trauma Patients

BACKGROUND

Predictive biomarkers in biofluids are the most commonly used diagnostic method, but established markers in trauma diagnostics lack accuracy. This study investigates promising microRNAs (miRNA) released from affected tissue after severe trauma that have predictive values for the effects of the injury.

METHODS

A retrospective analysis of prospectively collected data and blood samples of n = 33 trauma patients (ISS ≥ 16) is provided. Levels of miR-9-5p, -124-3p, -142-3p, -219a-5p, -338-3p and -423-3p in severely injured patients (PT) without traumatic brain injury (TBI) or with severe TBI (PT + TBI) and patients with isolated TBI (isTBI) were measured within 6 h after trauma.

RESULTS

The highest miR-423-3p expression was detected in patients with severe isTBI, followed by patients with PT + TBI, and lowest levels were found in PT patients without TBI (2^-∆∆Ct, p = 0.009). A positive correlation between miR-423-3p level and increasing AIS_head (p = 0.001) and risk of mortality (RISC II, p = 0.062) in trauma patients (n = 33) was found. ROC analysis of miR-423-3p levels revealed them as statistically significant to predict the severity of brain injury in trauma patients (p = 0.006). miR-124-3p was only found in patients with severe TBI, miR-338-3p was shown in all trauma groups. miR-9-5p, miR-142-3p and miR-219a-5p could not be detected in any of the four groups.

CONCLUSION

miR-423-3p expression is significantly elevated after isolated traumatic brain injury and predictable for severe TBI in the first hours after trauma. miR-423-3p could represent a promising new biomarker to identify severe isolated TBI.

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.

Plasma Exosome-derived MicroRNAs as Novel Biomarkers of Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is a widespread central nervous system (CNS) condition and a leading cause of death, disability, and long-term disability including seizures and emotional and behavioral issues. To date, applicable diagnostic biomarkers have not been elucidated. MicroRNAs (miRNAs) are enriched and stable in exosomes in plasma. Therefore, we speculated that miRNAs in plasma exosomes might serve as novel biomarkers for TBI diagnosis and are also involved in the pathogenesis of TBI. In this study, we first isolated exosomes from peripheral blood plasma in rats with TBI and then investigated the alterations in miRNA expression in exosomes by high-throughput RNA sequencing. As a result, we identified 50 significantly differentially expressed miRNAs, including 31 upregulated and 19 downregulated miRNAs. Then, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the most highly correlated pathways that were identified were the MAPK signaling pathway, regulation of actin cytoskeleton, Rap1 signaling pathway and Ras signaling pathway. This study provides novel perspectives on miRNAs in peripheral blood plasma exosomes, which not only could be used as biomarkers of TBI diagnosis but could also be manipulated as therapeutic targets of TBI.

Current trends in biomarker discovery and analysis tools for traumatic brain injury

Traumatic brain injury (TBI) affects 1.7 million people in the United States each year, causing lifelong functional deficits in cognition and behavior. The complex pathophysiology of neural injury is a primary barrier to developing sensitive and specific diagnostic tools, which consequentially has a detrimental effect on treatment regimens. Biomarkers of other diseases (e.g. cancer) have provided critical insight into disease emergence and progression that lend to developing powerful clinical tools for intervention. Therefore, the biomarker discovery field has recently focused on TBI and made substantial advancements to characterize markers with promise of transforming TBI patient diagnostics and care. This review focuses on these key advances in neural injury biomarkers discovery, including novel approaches spanning from omics-based approaches to imaging and machine learning as well as the evolution of established techniques.

Comparison of serum and saliva miRNAs for identification and characterization of mTBI in adult mixed martial arts fighters

Traumatic brain injury (TBI) is a major cause of death and disability worldwide, with mild TBI (mTBI) accounting for 85% of cases. mTBI is also implicated in serious long-term sequelae including second impact syndrome and chronic traumatic encephalopathy. mTBI often goes undiagnosed due to delayed symptom onset and limited sensitivity of conventional assessment measures compared with severe TBI. Current efforts seek to identify accurate and reliable non-invasive biomarkers associated with functional measures relevant to long-term outcomes. Here we evaluated the utility of serum and salivary microRNAs (miRNAs) to serve as sensitive and specific peripheral biomarkers of possible mTBI. Our primary objectives were to establish the relationship between peripheral measures of miRNA, objective quantification of head impacts, and sensitive indices of balance and cognitive function in healthy young adult athletes. A secondary objective was to compare the sensitivity of miRNA versus commonly used blood-based protein biomarkers. 50 amateur mixed martial arts (MMA) fighters participated. 216 saliva and serum samples were collected at multiple time points, both pre- and post-fight. Levels of 10 serum proteins were compared in a subset of the fighters (n = 24). Levels of miRNAs were obtained by next generation sequencing. Functional outcomes were evaluated using a computerized assessment system that measured cognitive performance, body sway, and combined cognitive performance and body sway during dual task completion. Data were analyzed using multivariate logistic regression for predictive classification, analysis of variance, correlation analysis and principal component analysis. We identified a subset of salivary and serum miRNAs that showed robust utility at predicting TBI likelihood and demonstrated quantitative associations with head impacts as well as cognitive and balance measures. In contrast, serum proteins demonstrated far less utility. We also found that the timing of the responses varies in saliva and serum, which is a critical observation for biomarker studies to consider.

Apolipoprotein E Affects In Vitro Axonal Growth and Regeneration via the MAPK Signaling Pathway

Following central nervous system injury in mammals, failed axonal regeneration is closely related to dysneuria. Previous studies have shown that the obvious effects of apolipoprotein E (ApoE) on traumatic brain injury (TBI) were associated with an axonal mechanism. However, little information on the actions of ApoE and its isoforms on axonal regeneration following TBI was provided. In our study, the cerebral cortices of ApoE-deficient (ApoE^-/-) and wild-type (ApoE^+/+) mice were cultured in vitro, and an axonal transection model was established. Interventions included the conditioned medium of astrocytes, human recombinant ApoE2/3/4 isoforms and inhibitors of the JNK/ERK/p38 pathway. Axonal growth and regeneration were evaluated by measuring the maximum distance and area of the axons. The expression levels of β-tubulin III, MAP2, ApoE, p-JNK, p-ERK and p-p38 were detected by immunofluorescence and western blotting. The results showed that ApoE mRNA and protein were expressed in intact axons and regenerated axons. Axonal growth and regeneration were attenuated in ApoE^-/- mice but recovered by exogenous ApoE. Human recombinant ApoE3 positively influenced axonal growth and regeneration; these effects were mediated by the JNK/ERK/p38 pathway. These results suggest ApoE and its isoforms may have influenced axonal growth and regeneration via the MAPK signaling pathway in vitro.

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-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.

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.

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.

Extracellular Vesicles: Biomarkers, Therapeutics, and Vehicles in the Visual System

PURPOSE

We discuss recent advances in extracellular vesicle (EV) technology as biomarkers, therapeutics, and drug delivery vehicles in the visual system with an emphasis on the retina.

RECENT FINDINGS

Retinal cell-type specific EVs can be detected in the blood and in the aqueous humor and EV miRNA cargoes can be used diagnostically to predict retinal disease progression. Studies have now shown EVs can deliver bioactive miRNA and AAV cargoes to the inner retinal cell layers and, in some models, improve retinal ganglion cell (RGC) survival and axon regeneration.

SUMMARY

EV molecular profiles and cargoes are attractive biomarkers for retinal and optic nerve disease and trauma and EVs offer a safe and tunable platform for delivering therapies to ocular tissues. However, EVs are heterogeneous by nature with variable lipid membranes, cargoes, and biologic effects, warranting stringent characterization to understand how heterogeneous EV populations modulate positive tissue remodeling.

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).