Differential response of miRNA-21 and its targets after traumatic brain injury in aging mice

Prospects and challenges of tissue-derived extracellular vesicles

Extracellular vesicles (EVs) are considered a vital component of cell-to-cell communication and represent a new frontier in diagnostics and a means to identify pathways for therapeutic intervention. Recently, studies have revealed the importance of tissue-derived EVs (Ti-EVs), which are EVs present in the interstitial spaces between cells, as they better represent the underlying physiology of complex, multicellular tissue microenvironments in biology and disease. EVs are native, lipid bilayer membraned nano-sized particles produced by all cells that are packaged with varied functional biomolecules including proteins, lipids, and nucleic acids. They are implicated in short- and long-range cellular communication and may elicit functional responses in recipient cells. To date, studies have often utilized cultured cells or biological fluids as a source for EVs that do not capture local molecular signatures of the tissue microenvironment. Recent work utilizing Ti-EVs has elucidated novel biomarkers for disease and provided insights into disease mechanisms that may lead to the development of novel therapeutic agents. Still, there are considerable challenges facing current studies. This review explores the vast potential and unique challenges for Ti-EV research and provides considerations for future studies that seek to advance this exciting field.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

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

hPMSCs-Derived Exosomal miRNA-21 Protects Against Aging-Related Oxidative Damage of CD4+ T Cells by Targeting the PTEN/PI3K-Nrf2 Axis

Mesenchymal stem cells (MSCs)-derived exosomes were considered a novel therapeutic approach in many aging-related diseases. This study aimed to clarify the protective effects of human placenta MSCs-derived exosomes (hPMSC-Exo) in aging-related CD4⁺ T cell senescence and identified the underlying mechanisms using a D-gal induced mouse aging model. Senescent T cells were detected SA-β-gal stain. The degree of DNA damage was evaluated by detecting the level of 8-OH-dG. The superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities were measured. The expression of aging-related proteins and senescence-associated secretory phenotype (SASP) were detected by Western blot and RT-PCR. We found that hPMSC-Exo treatment markedly decreased oxidative stress damage (ROS and 8-OH-dG), SA-β-gal positive cell number, aging-related protein expression (p53 and γ-H2AX), and SASP expression (IL-6 and OPN) in senescent CD4⁺ T cells. Additionally, hPMSC-Exo containing miR-21 effectively downregulated the expression of PTEN, increased p-PI3K and p-AKT expression, and Nrf2 nuclear translocation and the expression of downstream target genes (NQO1 and HO-1) in senescent CD4⁺ T cells. Furthermore, in vitro studies uncovered that hPMSC-Exo attenuated CD4⁺ T cell senescence by improving the PTEN/PI3K-Nrf2 axis by using the PTEN inhibitor bpV (HOpic). We also validated that PTEN was a target of miR-21 by using a luciferase reporter assay. Collectively, the obtained results suggested that hPMSC-Exo attenuates CD4⁺ T cells senescence via carrying miRNA-21 and activating PTEN/PI3K-Nrf2 axis mediated exogenous antioxidant defenses.

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

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

Real-Time Noninvasive Bioluminescence, Ultrasound and Photoacoustic Imaging in NFκB-RE-Luc Transgenic Mice Reveal Glia Maturation Factor-Mediated Immediate and Sustained Spatio-Temporal Activation of NFκB Signaling Post-Traumatic Brain Injury in a Gender-Specific Manner

Neurotrauma especially traumatic brain injury (TBI) is the leading cause of death and disability worldwide. To improve upon the early diagnosis and develop precision-targeted therapies for TBI, it is critical to understand the underlying molecular mechanisms and signaling pathways. The transcription factor, nuclear factor kappa B (NFκB), which is ubiquitously expressed, plays a crucial role in the normal cell survival, proliferation, differentiation, function, as well as in disease states like neuroinflammation and neurodegeneration. Here, we hypothesized that real-time noninvasive bioluminescence molecular imaging allows rapid and precise monitoring of TBI-induced immediate and rapid spatio-temporal activation of NFκB signaling pathway in response to Glia maturation factor (GMF) upregulation which in turn leads to neuroinflammation and neurodegeneration post-TBI. To test and validate our hypothesis and to gain novel mechanistic insights, we subjected NFκB-RE-Luc transgenic male and female mice to TBI and performed real-time noninvasive bioluminescence imaging (BLI) as well as photoacoustic and ultrasound imaging (PAI). Our BLI data revealed that TBI leads to an immediate and sustained activation of NFκB signaling. Further, our BLI data suggest that especially in male NFκB-RE-Luc transgenic mice subjected to TBI, in addition to brain, there is widespread activation of NFκB signaling in multiple organs. However, in the case of the female NFκB-RE-Luc transgenic mice, TBI induces a very specific and localized activation of NFκB signaling in the brain. Further, our microRNA data suggest that TBI induces significant upregulation of mir-9-5p, mir-21a-5p, mir-34a-5p, mir-16-3p, as well as mir-155-5p within 24 h and these microRNAs can be successfully used as TBI-specific biomarkers. To the best of our knowledge, this is one of the first and unique study of its kind to report immediate and sustained activation of NFκB signaling post-TBI in a gender-specific manner by utilizing real-time non-invasive BLI and PAI in NFκB-RE-Luc transgenic mice. Our study will prove immensely beneficial to gain novel mechanistic insights underlying TBI, unravel novel therapeutic targets, as well as enable us to monitor in real-time the response to innovative TBI-specific precision-targeted gene and stem cell-based precision medicine.

Melatonin as a promising modulator of aging related neurodegenerative disorders: Role of microRNAs

One of the host risk factors involved in aging-related diseases is coupled with the reduction of endogenous melatonin (MLT) synthesis in the pineal gland. MLT is considered a well-known pleiotropic regulatory hormone to modulate a multitude of biological processes such as the regulation of circadian rhythm attended by potent anti-oxidant, anti-inflammatory, and anti-cancer properties. It has also been established that the microRNAs family, as non-coding mRNAs regulating post-transcriptional processes, also serve a crucial role to promote MLT-related advantageous effects in both experimental and clinical settings. Moreover, the anti-aging impact of MLT and miRNAs participation jointly are of particular interest, recently. In this review, we aimed to scrutinize recent advances concerning the therapeutic implications of MLT, particularly in the brain tissue in the face of aging. We also assessed the possible interplay between microRNAs and MLT, which could be considered a therapeutic strategy to slow down the aging process in the nervous system.

Ethnic and trans-ethnic genome-wide association studies identify new loci influencing Japanese Alzheimer's disease risk

Alzheimer's disease (AD) has no cure, but early detection and risk prediction could allow earlier intervention. Genetic risk factors may differ between ethnic populations. To discover novel susceptibility loci of AD in the Japanese population, we conducted a genome-wide association study (GWAS) with 3962 AD cases and 4074 controls. Out of 4,852,957 genetic markers that passed stringent quality control filters, 134 in nine loci, including APOE and SORL1, were convincingly associated with AD. Lead SNPs located in seven novel loci were genotyped in an independent Japanese AD case-control cohort. The novel locus FAM47E reached genome-wide significance in a meta-analysis of association results. This is the first report associating the FAM47E locus with AD in the Japanese population. A trans-ethnic meta-analysis combining the results of the Japanese data sets with summary statistics from stage 1 data of the International Genomics of Alzheimer's Project identified an additional novel susceptibility locus in OR2B2. Our data highlight the importance of performing GWAS in non-European populations.

Anabolic-androgenic steroids and brain injury: miRNA evaluation in users compared to cocaine abusers and elderly people

Anabolic-androgenic steroids (AASs) can be used to treat both hormonal diseases and other pathologies characterized by muscle loss (aging, cancer, and AIDS). Even if the adverse effects related to the misuse of AASs have been well studied in different systems and apparatuses, knowledge about brain damage is poor.In this scenario, this experimental study aimed to analyze the role of several microRNAs (miRNAs) in brain damage after AAS misuse, to better comprehend the underlying mechanisms. The research hypothesis at the base of this experimental study is that the chronic use of AASs may be associated to brain damage with a dysregulation of these miRNAs. Moreover, miRNA expression values were compared among three different groups, "AAS" group, "Cocaine" group and "Aging" group, in order to define if AAS brain damage can be compared with the brain impairment linked to aging and/or cocaine assumption.This experimental study revealed that the tested miRNAs (hsa-miR-21-5p, hsa-miR-34a-5p, hsa-miR-124-5p, hsa-miR-132-3p, and hsa-miR-144-3p) were overexpressed in all enrolled groups. In the light of the presented results, the identification of specific circulating and/or tissue biomarkers is challenging for the scientific community. Further studies with larger samples are needed to confirm these interesting findings.

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

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

Epigenetic mechanisms of neurodegenerative diseases and acute brain injury

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

Inhibition of miR-324-5p increases PM20D1-mediated white and brown adipose loss and reduces body weight in juvenile mice

Obesity is a serious public health problem characterized by abnormal or excessive fat accumulation, which is caused by an energy imbalance between calories consumed and calories expended. MiRNAs have been involved in the regulation of occurrence and progression of obesity. This study aims to investigate the role of miR-324-5p in regulating the adipose tissue mass and preliminarily probe into its effect on progression of obesity. MiR-324-5p was upregulated in the epididymal white adipose tissues (eWAT), inguinal white adipose tissues (iWAT) and brown adipose tissues (BAT) of the mice fed with high fat diet (HFD). Under room temperature (RT) or thermoneutrality (TN) condition, when tail intravenously injected with miR-324-5p antagomir (anta-miR-324-5p), the fat mass and total weight of mice were both significantly suppressed. The suppressive effect was more distinct under TN than RT. The weight of iWAT and BAT were both inhibited by anta-miR-324-5p under TN. Moreover, PM20D1 was a direct target gene of miR-324-5p. In primary iWAT cells, the expression of PM20D1 was significantly increased by anta-miR-324-5p, whereas decreased by the miR-324-5p mimic. Furthermore, anta-miR-324-5p noticeably increased the cellular oxygen consumption in primary BAT and iWAT cells. Our findings indicated that inhibition of miR-324-5p increased PM20D1-mediated fat consumption and reduced body weight in mice, suggesting that miR-324-5p may be a novel therapeutic target against obesity.

Tackling Aging by Using miRNA as a Target and a Tool

miRNA is a class of short noncoding RNA that regulates gene expression at the post-transcriptional level. Evidence of age-associated changes in miRNA expression has been collected in models ranging from nematodes to humans; however, there has been little discussion of how to turn our knowledge of miRNA biology into antiaging therapy. This opinion article provides a snapshot of our current understanding of the roles of miRNA in modulating the aging process. We discuss major chemical techniques for modifying the miRNA structure as well as developing delivery systems for intervention. Finally, technical needs to be met for bench-to-clinic translation of miRNA-based interventions are highlighted for future research.

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.

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

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

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.

Targeting of microRNA-21-5p protects against seizure damage in a kainic acid-induced status epilepticus model via PTEN-mTOR

OBJECTIVE

Studies have shown that microRNAs play a role in the development of epilepsy by regulating downstream target messenger (m)RNA. The present study aims to determine the changes associated with microRNA-21-5p (miR-21-5p) during epileptogenesis in a kainic acid rat model, and to assess whether the PTEN-mTOR pathway is a target of miR-21-5p.

METHOD

Reverse transcription polymerase chain reaction (RT-PCR) was used to examine the quantitative expressions of miR-21-5p and PTEN, and Western blotting was used to test the activity of mTOR in the acute, latent, and chronic stages of epileptogenesis. The antagomir of miR-21-5p was injected into the intracerebroventricular space using a microsyringe. Neuronal death and epilepsy discharge were assessed by Nissl staining and electroencephalography (EEG), respectively. The Morris water maze (MWM) was used to assess the cognitive impairment in rats after status epilepticus (SE).

RESULTS

Both miR-21-5p and mTOR were upregulated and PTEN was downregulated in rats during acute, latent, and chronic stages of epileptogenesis when compared with those of the control. After using antagomir miR-21-5p in vivo, miR-21-5p and mTOR decreased and the expression of PTEN increased compared with that in the SE model. The silencing of miR-21-5p diminished the number of abnormal spikes on EEG and decreased the number of neuron deletions on Nissl staining. The cognitive and memory impairment caused by epilepsy could also be improved after miR-21-5p knockdown in vivo.

CONCLUSION

The results of the present study demonstrate that PTEN-mTOR is the target of miR-21-5p in a kainic acid model of epilepsy. The knockout of miR-21-5p decreases the neuronal damage in stages of epileptogenesis. The miR-21-5p/PTEN/mTOR axis may be a potential target for preventing and treating seizures and epileptic damage.

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

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

Traumatic brain injury: classification, models, and markers

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

Exosomes derived from hypoxia-preconditioned mesenchymal stromal cells ameliorate cognitive decline by rescuing synaptic dysfunction and regulating inflammatory responses in APP/PS1 mice

Administration of exosomes derived from mesenchymal stromal cells (MSCs) could improve some neurologic conditions by transferring functional biomolecules to recipient cells. Furthermore, exosomes from hypoxic progenitor cells exerted better therapeutic effects in organ injury through specific cargoes. However, there are no related reports about whether exosomes derived from MSCs or hypoxia-preconditioned MSCs (PC-MSCs) could prevent memory deficits in Alzheimer disease (AD). In this study, the exosomes derived from MSCs or PC-MSCs were systemically administered to transgenic APP/PS1 mice. The expression of miR-21 in MSCs was significantly increased after hypoxic treatment. Injection of exosomes from normoxic MSCs could rescue cognition and memory impairment according to results of the Morris water maze test, reduced plaque deposition, and Aβ levels in the brain; could decrease the activation of astrocytes and microglia; could down-regulate proinflammatory cytokines (TNF-α and IL-1β); and could up-regulate anti-inflammatory cytokines (IL-4 and -10) in AD mice, as well as reduce the activation of signal transducer and activator of transcription 3 (STAT3) and NF-κB. Compared to the group administered exosomes from normoxic MSCs, in the group administered exosomes from PC-MSCs, learning and memory capabilities were significantly improved; the plaque deposition and Aβ levels were lower, and expression of growth-associated protein 43, synapsin 1, and IL-10 was increased; and the levels of glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1, TNF-α, IL-1β, and activation of STAT3 and NF-κB were sharply decreased. More importantly, exosomes from PC-MSCs effectively increased the level of miR-21 in the brain of AD mice. Additionally, replenishment of miR-21 restored the cognitive deficits in APP/PS1 mice and prevented pathologic features. Taken together, these findings suggest that exosomes from PC-MSCs could improve the learning and memory capabilities of APP/PS1 mice, and that the underlying mechanism may lie in the restoration of synaptic dysfunction and regulation of inflammatory responses through regulation of miR-21.-Cui, G.-H., Wu, J., Mou, F.-F., Xie, W.-H., Wang, F.-B., Wang, Q.-L., Fang, J., Xu, Y.-W., Dong, Y.-R., Liu, J.-R., Guo, H.-D. Exosomes derived from hypoxia-preconditioned mesenchymal stromal cells ameliorate cognitive decline by rescuing synaptic dysfunction and regulating inflammatory responses in APP/PS1 mice.

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

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

MSCs-Derived Exosomes and Neuroinflammation, Neurogenesis and Therapy of Traumatic Brain Injury

Exosomes are endosomal origin membrane-enclosed small vesicles (30-100 nm) that contain various molecular constituents including proteins, lipids, mRNAs and microRNAs. Accumulating studies demonstrated that exosomes initiated and regulated neuroinflammation, modified neurogenic niches and neurogenesis, and were even of potential significance in treating some neurological diseases. These tiny extracellular vesicles (EVs) can derive from some kinds of multipotent cells such as mesenchymal stem cells (MSCs) that have been confirmed to be a potentially promising therapy for traumatic brain injury (TBI) in experimental models and in preclinical studies. Nevertheless, subsequent studies demonstrated that the predominant mechanisms of MSCs's contributions to brain tissue repairment and functional recovery after TBI were not the cell replacement effects but likely the secretion-based paracrine effects produced by EVs such as MSCs-derived exosomes. These nanosized exosomes derived from MSCs cannot proliferate, are easier to preserve and transfer and have lower immunogenicity, compared with transplanted exogenous MSCs. These reports revealed that MSCs-derived exosomes might promise to be a new and valuable therapeutic strategy for TBI than MSCs themselves. However, the concrete mechanisms involved in the positive effects induced by MSCs-derived exosomes in TBI are still ambiguous. In this review, we intend to explore the potential effects of MSCs-derived exosomes on neuroinflammation and neurogenesis in TBI and, especially, on therapy.

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).

Traumatic brain injury increases levels of miR-21 in extracellular vesicles: implications for neuroinflammation

Traumatic brain injury (TBI) is an important health concern and effective treatment strategies remain elusive. Understanding the complex multicellular response to TBI may provide new avenues for intervention. In the context of TBI, cell–cell communication is critical. One relatively unexplored form of cell–cell communication in TBI is extracellular vesicles (EVs). These membrane‐bound vesicles can carry many different types of cargo between cells. Recently, miRNA in EVs have been shown to mediate neuroinflammation and neuronal injury. To explore the role of EV‐associated miRNA in TBI, we isolated EVs from the brain of injured mice and controls, purified RNA from brain EVs, and performed miRNA sequencing. We found that the expression of miR‐212 decreased, while miR‐21, miR‐146, miR‐7a, and miR‐7b were significantly increased with injury, with miR‐21 showing the largest change between conditions. The expression of miR‐21 in the brain was primarily localized to neurons near the lesion site. Interestingly, adjacent to these miR‐21‐expressing neurons were activated microglia. The concurrent increase in miR‐21 in EVs with the elevation of miR‐21 in neurons, suggests that miR‐21 is secreted from neurons as potential EV cargo. Thus, this study reveals a new potential mechanism of cell–cell communication not previously described in TBI.

A study of microRNAs from dried blood spots in newborns after perinatal asphyxia: a simple and feasible biosampling method

BACKGROUND

The potential of microRNAs (miRNAs) as bedside biomarkers in selecting newborns with hypoxic-ischemic encephalopathy (HIE) for neuroprotection has yet to be explored. Commonly, blood-based biomarker tests use plasma or serum which don't allow evaluation of both intracellular and extracellular changes.

METHODS

We describe a technique to extract and compare expression of miRNAs from a single small 6-mm-diameter dried blood spot (DBS) stored at room temperature with those from EDTA-blood, plasma, and urine. Three miRNAs (RNU6B, let7b, and miR-21) were quantified via extraction and quantitative RT-PCR performed from a DBS and compared with levels from EDTA-blood, plasma, and urine. Secondarily, candidate miRNAs let7b, miR-21, miR-29b, miR-124, and miR-155 in DBS were evaluated as potential biomarkers for HIE.

RESULTS

Candidate miRNAs were extractable in all biosamples from newborns, with the highest expression in DBS. There was a good correlation between miRNAs' levels in DBS and EDTA-blood at -80 °C. No significant difference was observed in the miRNA levels between the favorable and unfavorable outcome groups for babies with HIE.

CONCLUSION

DBS may be useful for studying the potential of miRNAs as biomarkers for brain injury.

Regulatory roles of microRNA-21 in fibrosis through interaction with diverse pathways (Review)

MicroRNA-21 (miR-21) is a small, non-coding RNA which can regulate gene expression at the post‑transcriptional level. While the fibrogenic process is vital in tissue repair, proliferation and transition of fibrogenic cells combined with an imbalance of secretion and degradation of the extracellular matrix results in excessive tissue remodeling and fibrosis. Recent studies have indicated that miR‑21 is overexpressed during fibrosis and can regulate the fibrogenic process in a variety of organs and tissues via diverse pathways. The present review summarized the significant roles of miR-21 in fibrosis and discussed the underlying key pathways.

A Single Bolus of Docosahexaenoic Acid Promotes Neuroplastic Changes in the Innervation of Spinal Cord Interneurons and Motor Neurons and Improves Functional Recovery after Spinal Cord Injury

Docosahexaenoic acid (DHA) is an ω-3 polyunsaturated fatty acid that is essential in brain development and has structural and signaling roles. Acute DHA administration is neuroprotective and promotes functional recovery in animal models of adult spinal cord injury (SCI). However, the mechanisms underlying this recovery have not been fully characterized. Here we investigated the effects of an acute intravenous bolus of DHA delivered after SCI and characterized DHA-induced neuroplasticity within the adult injured spinal cord. We found robust sprouting of uninjured corticospinal and serotonergic fibers in a rat cervical hemisection SCI model. A mouse pyramidotomy model was used to confirm that this robust sprouting was not species or injury model specific. Furthermore, we demonstrated that corticospinal fibers sprouting to the denervated side of the cord following pyramidotomy contact V2a interneurons. We also demonstrated increased serotonin fibers and synaptophysin in direct contact with motor neurons. DHA also increased synaptophysin in rat cortical cell cultures. A reduction in phosphatase and tensin homolog (PTEN) has been shown to be involved in axonal regeneration and synaptic plasticity. We showed that DHA significantly upregulates miR-21 and downregulates PTEN in corticospinal neurons. Downregulation of PTEN and upregulation of phosphorylated AKT by DHA were also seen in primary cortical neuron cultures and were accompanied by increased neurite outgrowth. In summary, acute DHA induces anatomical and synaptic plasticity in adult injured spinal cord. This study shows that DHA has therapeutic potential in cervical SCI and provides evidence that DHA could exert its beneficial effects in SCI via enhancement of neuroplasticity.

SIGNIFICANCE STATEMENT

In this study, we show that an acute intravenous injection of docosahexaenoic acid (DHA) 30 min after spinal cord injury induces neuroplasticity. We found robust sprouting of uninjured corticospinal and serotonergic fibers in a rat hemisection spinal cord injury model. A mouse pyramidotomy model was used to confirm that the robust sprouting involved V2a interneurons. We show that DHA significantly upregulates miR-21 and phosphorylated AKT, and downregulates phosphatase and tensin homolog (PTEN), which is involved in suppressing anatomical plasticity, in corticospinal neurons and in primary cortical neuron cultures. We conclude that acute DHA can induce anatomical and synaptic plasticity. This provides direct evidence that DHA could exert its beneficial effects in spinal cord injury via neuroplasticity enhancement.

Systematic analysis of the p53-related microRNAs in breast cancer revealing their essential roles in the cell cycle

Numerous miRNAs have been found to be involved in the regulation of the p53 signaling pathway. Conversely, p53 regulates the transcription or processing of microRNAs (miRNAs). Given that complexities in the association between p53 and miRNAs exist, and due to the rapidly increasing amount of literature regarding the interactions between p53 and miRNAs, the present study systematically analyzed the associations between miRNAs and p53 in breast cancer using a literature-based discovery approach, natural language processing. A total of 22 miRNAs were found to be associated with p53. Next, three popular online tools (PicTar, miRanda and TargetScan) were used to predict the targets of each miRNA, and certain targets were validated by experiments. Gene Ontology annotation and network analysis demonstrated that the majority of the targets of the p53-related miRNAs were enriched in the cell cycle process. These results suggest that, in addition to regulating the transcription of cell cycle-related genes, p53 also indirectly modulates the cell cycle via miRNAs.

Targeting MicroRNAs in Prevention and Treatment of Neurodegenerative Disorders

Preclinical Research microRNAs (miRNAs) are small noncoding RNAs (ncRNAs) that are key regulators of gene expression. They act on wide range of targets by binding to mRNA via imperfect complementarity at 3' UTR. Evidence suggests that miRNAs regulate many biological processes including neuronal development, differentiation, and disease. Altered expression of several miRNAs has been reported in many neurodegenerative disorders (NDDs). Many miRNAs are altered in these diseases, but miRNA 15, miRNA 21, and miRNA 146a have been shown to play critical role in many neurodegenerative conditions. As these miRNAs regulate many genes, miRNA targeted approaches would allow concurrently targeting of multiple effectors of pathways that regulate disease progression. In this review, we describe the role of miRNAs in various NDDs and their potential as therapeutic tools in prevention and treatment of neurological conditions.

MiR-21 in Extracellular Vesicles Leads to Neurotoxicity via TLR7 Signaling in SIV Neurological Disease

Recent studies have found that extracellular vesicles (EVs) play an important role in normal and disease processes. In the present study, we isolated and characterized EVs from the brains of rhesus macaques, both with and without simian immunodeficiency virus (SIV) induced central nervous system (CNS) disease. Small RNA sequencing revealed increased miR-21 levels in EVs from SIV encephalitic (SIVE) brains. In situ hybridization revealed increased miR-21 expression in neurons and macrophage/microglial cells/nodules during SIV induced CNS disease. In vitro culture of macrophages revealed that miR-21 is released into EVs and is neurotoxic when compared to EVs derived from miR-21^-/- knockout animals. A mutation of the sequence within miR-21, predicted to bind TLR7, eliminates this neurotoxicity. Indeed miR-21 in EV activates TLR7 in a reporter cell line, and the neurotoxicity is dependent upon TLR7, as neurons isolated from TLR7^-/- knockout mice are protected from neurotoxicity. Further, we show that EVs isolated from the brains of monkeys with SIV induced CNS disease activates TLR7 and were neurotoxic when compared to EVs from control animals. Finally, we show that EV-miR-21 induced neurotoxicity was unaffected by apoptosis inhibition but could be prevented by a necroptosis inhibitor, necrostatin-1, highlighting the actions of this pathway in a growing number of CNS disorders.

HIV associated neurocognitive disorder (HAND) are neurological disorders caused due to the entry of HIV infection in the brain. HIV-1 does not directly infect central or peripheral neurons, however, virus-infected cells of the monocyte/macrophage lineage maintain a low-level HIV infection in the CNS. "Indirect effects" of macrophage activation–such as dysregulation of cytokines and chemokines, free-radical (oxidative stress) injury, and secretion of soluble factors that are potently neurotoxic–have been implicated as effectors of nervous system injury in HIV. Here, we report that extracellular vesicles released from macrophages can enhance neurotoxicity. Using a nonhuman primate model of HAND, simian immunodeficiency virus encephalitis (SIVE), we find that exosomes isolated from SIVE brains contain,microRNAs, including miR-21, that can serve as ligands to the key immune regulatory receptors, toll-like receptors, and can elicit neurotoxicity. We provide in vitro evidence for such an effect, and that the toxicity can be mediated by necroptosis. Thus, our study provides insights into other potential neurotoxic mechanisms by which HIV infection in the brain could harm neuronal health.

Investigational agents for treatment of traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. To date, there are no pharmacologic agents proven to improve outcomes from TBI because all the Phase III clinical trials in TBI have failed. Thus, there is a compelling need to develop treatments for TBI.

AREAS COVERED

The following article provides an overview of select cell-based and pharmacological therapies under early development for the treatment of TBI. These therapies seek to enhance cognitive and neurological functional recovery through neuroprotective and neurorestorative strategies.

EXPERT OPINION

TBI elicits both complex degenerative and regenerative tissue responses in the brain. TBI can lead to cognitive, behavioral, and motor deficits. Although numerous promising neuroprotective treatment options have emerged from preclinical studies that mainly target the lesion, translation of preclinical effective neuroprotective drugs to clinical trials has proven challenging. Accumulating evidence indicates that the mammalian brain has a significant, albeit limited, capacity for both structural and functional plasticity, as well as regeneration essential for spontaneous functional recovery after injury. A new therapeutic approach is to stimulate neurovascular remodeling by enhancing angiogenesis, neurogenesis, oligodendrogenesis, and axonal sprouting, which in concert, may improve neurological functional recovery after TBI.