Loss of microRNA-15a/16-1 function promotes neuropathological and functional recovery in experimental traumatic brain injury.

The diffuse axonal damage in white matter and neuronal loss, along with excessive neuroinflammation, hinder long-term functional recovery after traumatic brain injury (TBI). MicroRNAs (miRs) are small noncoding RNAs that negatively regulate protein-coding target genes in a posttranscriptional manner. Recent studies have shown that loss of function of the miR-15a/16-1 cluster reduced neurovascular damage and improved functional recovery in ischemic stroke and vascular dementia. However, the role of the miR-15a/16-1 cluster in neurotrauma is poorly explored. Here, we report that genetic deletion of the miR-15a/16-1 cluster facilitated the recovery of sensorimotor and cognitive functions, alleviated white matter/gray matter lesions, reduced cerebral glial cell activation, and inhibited infiltration of peripheral blood immune cells to brain parenchyma in a murine model of TBI when compared with WT controls. Moreover, intranasal delivery of the miR-15a/16-1 antagomir provided similar brain-protective effects conferred by genetic deletion of the miR-15a/16-1 cluster after experimental TBI, as evidenced by showing improved sensorimotor and cognitive outcomes, better white/gray matter integrity, and less inflammatory responses than the control antagomir-treated mice after brain trauma. miR-15a/16-1 genetic deficiency and miR-15a/16-1 antagomir also significantly suppressed inflammatory mediators in posttrauma brains. These results suggest miR-15a/16-1 as a potential therapeutic target for TBI.

Role of regulatory non-coding RNAs in traumatic brain injury.

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

[Effects of Different Carbon Inputs on Soil Stoichiometry in Tianshan Mountains].

Soil C, N, and P elements are important components of the forest ecosystem. Studying the influence of exogenous carbon input change on the stoichiometry of the forest soil can reveal the element recycling process and the balanced feedback mechanism of the forest ecosystem. In this study, using the research object of a spruce forest in Tianshan Mountain, the short-term effect of exogenous carbon input on soil C, N, and P in the soil was analyzed through Detritus Input and Removal Treatment (DIRT), and then the interrelationship between soil stoichiometry and other soil physicochemical factors under different treatments was discussed. The results showed that:① the soil C, N, and P contents in most soil layers were the highest double litter (DL) treatment, soil ω(C) by soil depth from shallow to deep was 168.92, 119.88, 103.33, and 64.23 g·kg-1; soil ω(N) was 10.60, 9.32, 8.78, and 8.07 g·kg-1; soil ω(P) was 0.50, 0.45, 0.37, and 0.36 g·kg-1; in the no input (NI) treatment, soil ω(C) by soil depth from shallow to deep was 104.56, 89.24, 48.08, and 43.96 g·kg-1; soil ω(N) was 6.83, 2.60, 2.63, and 2.22 g·kg-1; soil ω(P) was 0.40, 0.34, 0.32, and 0.22 g·kg-1; and a decreased trend was shown with the deepening of the soil layer. Except in the NI treatment, C:N was 0-10 cm and significantly higher than that in other soils (P<0.05), NL soil C:P at 30-50 cm was significantly higher than that in other soils, and NI soil N:P was 0-10 cm and significantly higher than that in other soils (P<0.05). ② Microbial carbon, nitrogen, and phosphorus were significantly higher from 0-10 cm than that in other soil layers (P<0.05). ③ Redundancy analysis results showed that soluble organic carbon and microbial nitrogen at different carbon input levels were important factors affecting the stoichiometric characteristics of soil C, N, and P.

Interleukin-4 mitigates anxiety-like behavior and loss of neurons and fiber tracts in limbic structures in a microglial PPARγ-dependent manner after traumatic brain injury.

Traumatic brain injury (TBI) is commonly followed by intractable psychiatric disorders and long-term changes in affect, such as anxiety. The present study sought to investigate the effect of repetitive intranasal delivery of interleukin-4 (IL-4) nanoparticles on affective symptoms after TBI in mice. Adult male C57BL/6 J mice (10-12 weeks of age) were subjected to controlled cortical impact (CCI) and assessed by a battery of neurobehavioral tests up to 35 days after CCI. Neuron numbers were counted in multiple limbic structures, and the integrity of limbic white matter tracts was evaluated using ex vivo diffusion tensor imaging (DTI). As STAT6 is a critical mediator of IL-4-specific transcriptional activation, STAT6 knockout mice were used to explore the role of endogenous IL-4/STAT6 signaling axis in TBI-induced affective disorders. We also employed microglia/macrophage (Mi/Mϕ)-specific PPARγ conditional knockout (mKO) mice to test if Mi/Mϕ PPARγ critically contributes to IL-4-afforded beneficial effects. We observed anxiety-like behaviors up to 35 days after CCI, and these measures were exacerbated in STAT6 KO mice but mitigated by repetitive IL-4 delivery. We discovered that IL-4 protected against neuronal loss in limbic structures, such as the hippocampus and the amygdala, and improved the structural integrity of fiber tracts connecting the hippocampus and amygdala. We also observed that IL-4 boosted a beneficial Mi/Mϕ phenotype (CD206+/Arginase 1+/PPARγ+ triple-positive) in the subacute injury phase, and that the numbers of Mi/Mϕ appositions with neurons were robustly correlated with long-term behavioral performances. Remarkably, PPARγ-mKO completely abolished IL-4-afforded protection. Thus, CCI induces long-term anxiety-like behaviors in mice, but these changes in affect can be attenuated by transnasal IL-4 delivery. IL-4 prevents the long-term loss of neuronal somata and fiber tracts in key limbic structures, perhaps due to a shift in Mi/Mϕ phenotype. Exogenous IL-4 therefore holds promise for future clinical management of mood disturbances following TBI.

Genetic deletion of Krüppel-like factor 11 aggravates traumatic brain injury.

BACKGROUND: The long-term functional recovery of traumatic brain injury (TBI) is hampered by pathological events, such as parenchymal neuroinflammation, neuronal death, and white matter injury. Krüppel-like transcription factor 11 (KLF 11) belongs to the zinc finger family of transcription factors and actively participates in various pathophysiological processes in neurological disorders. Up to now, the role and molecular mechanisms of KLF11 in regulating the pathogenesis of brain trauma is poorly understood. METHODS: KLF11 knockout (KO) and wild-type (WT) mice were subjected to experimental TBI, and sensorimotor and cognitive functions were evaluated by rotarod, adhesive tape removal, foot fault, water maze, and passive avoidance tests. Brain tissue loss/neuronal death was examined by MAP2 and NeuN immunostaining, and Cresyl violet staining. White matter injury was assessed by Luxol fast blue staining, and also MBP/SMI32 and Caspr/Nav1.6 immunostaining. Activation of cerebral glial cells and infiltration of blood-borne immune cells were detected by GFAP, Iba-1/CD16/32, Iba-1/CD206, Ly-6B, and F4/80 immunostaining. Brian parenchymal inflammatory cytokines were measured with inflammatory array kits. RESULTS: Genetic deletion of KLF11 worsened brain trauma-induced sensorimotor and cognitive deficits, brain tissue loss and neuronal death, and white matter injury in mice. KLF11 genetic deficiency in mice also accelerated post-trauma astrocytic activation, promoted microglial polarization to a pro-inflammatory phenotype, and increased the infiltration of peripheral neutrophils and macrophages into the brain parenchyma. Mechanistically, loss-of-KLF11 function was found to directly increase the expression of pro-inflammatory cytokines in the brains of TBI mice. CONCLUSION: KLF11 acts as a novel protective factor in TBI. KLF11 genetic deficiency in mice aggravated the neuroinflammatory responses, grey and white matter injury, and impaired long-term sensorimotor and cognitive recovery. Elucidating the functional importance of KLF11 in TBI may lead us to discover novel pharmacological targets for the development of effective therapies against brain trauma.

Genetic Deficiency of MicroRNA-15a/16-1 Confers Resistance to Neuropathological Damage and Cognitive Dysfunction in Experimental Vascular Cognitive Impairment and Dementia.

Chronic cerebral hypoperfusion-derived brain damage contributes to the progression of vascular cognitive impairment and dementia (VCID). Cumulative evidence has shown that microRNAs (miRs) are emerging as novel therapeutic targets for CNS disorders. In this study, it is sought to determine the regulatory role of miR-15a/16-1 in VCID. It is found that miR-15a/16-1 knockout (KO) mice exhibit less cognitive and sensorimotor deficits following VCID. Genetic deficiency of miR-15a/16-1 in VCID mice also mitigate myelin degeneration, axonal injury, and neuronal loss. Mechanistically, miR-15a/16-1 binds to the 3'-UTR of AKT3 and IL-10RA. Genetic deletion of miR-15a/16-1 increases AKT3 and IL-10RA expression in VCID brains, and intranasal delivery of AKT3 and IL-10RA siRNA-loaded nanoparticles partially reduce brain protection and cognitive recovery in miR-15a/16-1 KO mice after VCID. In conclusion, the miR-15a/16-1-IL/10RA/AKT3 axis plays a critical role in regulating vascular brain damage and cognitive decline after VCID. Targeting miR-15a/16-1 is a novel therapeutic approach for the treatment of VCID.

Non-coding RNAs in the regulation of blood-brain barrier functions in central nervous system disorders.

The blood-brain barrier (BBB) is an essential component of the neurovascular unit that controls the exchanges of various biological substances between the blood and the brain. BBB damage is a common feature of different central nervous systems (CNS) disorders and plays a vital role in the pathogenesis of the diseases. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNA (lncRNAs), and circular RNAs (circRNAs), are important regulatory RNA molecules that are involved in almost all cellular processes in normal development and various diseases, including CNS diseases. Cumulative evidences have demonstrated ncRNA regulation of BBB functions in different CNS diseases. In this review, we have summarized the miRNAs, lncRNAs, and circRNAs that can be served as diagnostic and prognostic biomarkers for BBB injuries, and demonstrated the involvement and underlying mechanisms of ncRNAs in modulating BBB structure and function in various CNS diseases, including ischemic stroke, hemorrhagic stroke, traumatic brain injury (TBI), spinal cord injury (SCI), multiple sclerosis (MS), Alzheimer's disease (AD), vascular cognitive impairment and dementia (VCID), brain tumors, brain infections, diabetes, sepsis-associated encephalopathy (SAE), and others. We have also discussed the pharmaceutical drugs that can regulate BBB functions via ncRNAs-related signaling cascades in CNS disorders, along with the challenges, perspective, and therapeutic potential of ncRNA regulation of BBB functions in CNS diseases.

Nitro-oleic acid-mediated blood-brain barrier protection reduces ischemic brain injury.

Nitro-oleic acid (OA-NO2), a nitroalkene formed in nitric oxide-dependent oxidative reactions, has been found in human plasma and is thought to regulate pathophysiological functions. Recently, accumulating evidence suggests that OA-NO2 may function as an anti-inflammatory mediator, and ameliorate the progression of diabetes and cardiovascular diseases. However, the role of OA-NO2 in ischemic brain injury remains unexplored. In this study, C57BL/6 mice were subjected to 1 h transient middle cerebral artery occlusion (MCAO) and followed by 1- 7 days of reperfusion. These mice were treated with vehicle, OA, or OA-NO2 (10 mg/kg) via tail vein injection at 2 h after the onset of MCAO. Our results show that intravenous administration of OA-NO2 led to reduced BBB leakage in ischemic brains, reduced brain infarct, and improved sensorimotor functions in response to ischemic insults when compared to OA and vehicle controls. Also, OA-NO2 significantly reduced BBB leakage-triggered infiltration of neutrophils and macrophages in the ischemic brains. Moreover, OA-NO2 treatment reduced the M1-type microglia and increased M2-type microglia. Mechanistically, OA-NO2 alleviated the decline of mRNA and protein level of major endothelial TJs including ZO-1 in stroke mice. Treatment of OA-NO2 also significantly inhibited stroke-induced inflammatory mediators, iNOS, E-selectin, P-selectin, and ICAM1, in mouse brains. In conclusion, OA-NO2 preserves BBB integrity and confers neurovascular protection in ischemic brain damage. OA-NO2-mediated brain protection may help us to develop a novel therapeutic strategy for the treatment of ischemic stroke.

Long non-coding RNAs mediate cerebral vascular pathologies after CNS injuries.

Central nervous system (CNS) injuries are one of the leading causes of morbidity and mortality worldwide, accompanied with high medical costs and a decreased quality of life. Brain vascular disorders are involved in the pathological processes of CNS injuries and might play key roles for their recovery and prognosis. Recently, increasing evidence has shown that long non-coding RNAs (lncRNAs), which comprise a very heterogeneous group of non-protein-coding RNAs greater than 200 nucleotides, have emerged as functional mediators in the regulation of vascular homeostasis under pathophysiological conditions. Remarkably, lncRNAs can regulate gene transcription and translation, thus interfering with gene expression and signaling pathways by different mechanisms. Hence, a deeper insight into the function and regulatory mechanisms of lncRNAs following CNS injury, especially cerebrovascular-related lncRNAs, could help in establishing potential therapeutic strategies to improve or inhibit neurological disorders. In this review, we highlight recent advancements in understanding of the role of lncRNAs and their application in mediating cerebrovascular pathologies after CNS injury.

Genetic deletion of endothelial microRNA-15a/16-1 promotes cerebral angiogenesis and neurological recovery in ischemic stroke through Src signaling pathway.

Cerebral angiogenesis is tightly controlled by specific microRNAs (miRs), including the miR-15a/16-1 cluster. Recently, we reported that endothelium-specific conditional knockout of the miR-15a/16-1 cluster (EC-miR-15a/16-1 cKO) promotes post-stroke angiogenesis and improves long-term neurological recovery by increasing protein levels of VEGFA, FGF2, and their respective receptors VEGFR2 and FGFR1. Herein, we further investigated the underlying signaling mechanism of these pro-angiogenic factors after ischemic stroke using a selective Src family inhibitor AZD0530. EC-miR-15a/16-1 cKO and age- and sex-matched wild-type littermate (WT) mice were subjected to 1 h middle cerebral artery occlusion (MCAO) and 28d reperfusion. AZD0530 was administered daily by oral gavage to both genotypes of mice 3-21d after MCAO. Compared to WT, AZD0530 administration exacerbated spatial cognitive impairments and brain atrophy in EC-miR-15a/16-1 cKO mice following MCAO. AZD0530 also attenuated long-term recovery of blood flow and inhibited the formation of new microvessels, including functional vessels with blood circulation, in the penumbra of stroked cKO mice. Moreover, AZD0530 blocked the Src signaling pathway by downregulating phospho-Src and its downstream mediators (p-Stat3, p-Akt, p-FAK, p-p44/42 MAPK, p-p38 MAPK) in post-ischemic brains. Collectively, our data demonstrated that endothelium-targeted deletion of the miR-15a/16-1 cluster promotes post-stroke angiogenesis and improves long-term neurological recovery via activating Src signaling pathway.

Noncoding RNAs in Cardiovascular Disease: Current Knowledge, Tools and Technologies for Investigation, and Future Directions: A Scientific Statement From the American Heart Association.

BACKGROUND: The discovery that much of the non-protein-coding genome is transcribed and plays a diverse functional role in fundamental cellular processes has led to an explosion in the development of tools and technologies to investigate the role of these noncoding RNAs in cardiovascular health. Furthermore, identifying noncoding RNAs for targeted therapeutics to treat cardiovascular disease is an emerging area of research. The purpose of this statement is to review existing literature, offer guidance on tools and technologies currently available to study noncoding RNAs, and identify areas of unmet need. METHODS: The writing group used systematic literature reviews (including MEDLINE, Web of Science through 2018), expert opinion/statements, analyses of databases and computational tools/algorithms, and review of current clinical trials to provide a broad consensus on the current state of the art in noncoding RNA in cardiovascular disease. RESULTS: Significant progress has been made since the initial studies focusing on the role of miRNAs (microRNAs) in cardiovascular development and disease. Notably, recent progress on understanding the role of novel types of noncoding small RNAs such as snoRNAs (small nucleolar RNAs), tRNA (transfer RNA) fragments, and Y-RNAs in cellular processes has revealed a noncanonical function for many of these molecules. Similarly, the identification of long noncoding RNAs that appear to play an important role in cardiovascular disease processes, coupled with the development of tools to characterize their interacting partners, has led to significant mechanistic insight. Finally, recent work has characterized the unique role of extracellular RNAs in mediating intercellular communication and their potential role as biomarkers. CONCLUSIONS: The rapid expansion of tools and pipelines for isolating, measuring, and annotating these entities suggests that caution in interpreting results is warranted until these methodologies are rigorously validated. Most investigators have focused on investigating the functional role of single RNA entities, but studies suggest complex interaction between different RNA molecules. The use of network approaches and advanced computational tools to understand the interaction of different noncoding RNA species to mediate a particular phenotype may be required to fully comprehend the function of noncoding RNAs in mediating disease phenotypes.

Endothelium-targeted deletion of the miR-15a/16-1 cluster ameliorates blood-brain barrier dysfunction in ischemic stroke.

The blood-brain barrier (BBB) maintains a stable brain microenvironment. Breakdown of BBB integrity during cerebral ischemia initiates a devastating cascade of events that eventually leads to neuronal loss. MicroRNAs are small noncoding RNAs that suppress protein expression, and we previously showed that the miR-15a/16-1 cluster is involved in the pathogenesis of ischemic brain injury. Here, we demonstrated that when subjected to experimentally induced stroke, mice with an endothelial cell (EC)-selective deletion of miR-15a/16-1 had smaller brain infarcts, reduced BBB leakage, and decreased infiltration of peripheral immune cells. These mice also showed reduced infiltration of proinflammatory M1-type microglia/macrophage in the peri-infarct area without changes in the number of resolving M2-type cells. Stroke decreases claudin-5 abundance, and we found that EC-selective miR-15a/16-1 deletion enhanced claudin-5 mRNA and protein abundance in ischemic mouse brains. In cultured mouse brain microvascular ECs (mBMECs), the miR-15a/16-1 cluster directly bound to the 3' untranslated region (3'UTR) of Claudin-5, and lentivirus-mediated ablation of miR-15a/16-1 diminished oxygen-glucose deprivation (OGD)-induced down-regulation of claudin-5 mRNA and protein abundance and endothelial barrier dysfunction. These findings suggest that genetic deletion of endothelial miR-15a/16-1 suppresses BBB pathologies after ischemic stroke. Elucidating the molecular mechanisms of miR-15a/16-1-mediated BBB dysfunction may enable the discovery of new therapies for ischemic stroke.

Endothelium-Targeted Deletion of microRNA-15a/16-1 Promotes Poststroke Angiogenesis and Improves Long-Term Neurological Recovery.

RATIONALE: Angiogenesis promotes neurological recovery after stroke and is associated with longer survival of stroke patients. Cerebral angiogenesis is tightly controlled by certain microRNAs (miRs), such as the miR-15a/16-1 cluster, among others. However, the function of the miR-15a/16-1 cluster in endothelium on postischemic cerebral angiogenesis is not known. OBJECTIVE: To investigate the functional significance and molecular mechanism of endothelial miR-15a/16-1 cluster on angiogenesis in the ischemic brain. METHODS AND RESULTS: Endothelial cell-selective miR-15a/16-1 conditional knockout (EC-miR-15a/16-1 cKO) mice and wild-type littermate controls were subjected to 1 hour middle cerebral artery occlusion followed by 28-day reperfusion. Deletion of miR-15a/16-1 cluster in endothelium attenuates post-stroke brain infarction and atrophy and improves the long-term sensorimotor and cognitive recovery against ischemic stroke. Endothelium-targeted deletion of the miR-15a/16-1 cluster also enhances post-stroke angiogenesis by promoting vascular remodeling and stimulating the generation of newly formed functional vessels, and increases the ipsilateral cerebral blood flow. Endothelial cell-selective deletion of the miR-15a/16-1 cluster up-regulated the protein expression of pro-angiogenic factors VEGFA (vascular endothelial growth factor), FGF2 (fibroblast growth factor 2), and their receptors VEGFR2 (vascular endothelial growth factor receptor 2) and FGFR1 (fibroblast growth factor receptor 1) after ischemic stroke. Consistently, lentiviral knockdown of the miR-15a/16-1 cluster in primary mouse or human brain microvascular endothelial cell cultures enhanced in vitro angiogenesis and up-regulated pro-angiogenic proteins expression after oxygen-glucose deprivation, whereas lentiviral overexpression of the miR-15a/16-1 cluster suppressed in vitro angiogenesis and down-regulated pro-angiogenic proteins expression. Mechanistically, miR-15a/16-1 translationally represses pro-angiogenic factors VEGFA, FGF2, and their receptors VEGFR2 and FGFR1, respectively, by directly binding to the complementary sequences within 3'-untranslated regions of those messenger RNAs. CONCLUSIONS: Endothelial miR-15a/16-1 cluster is a negative regulator for postischemic cerebral angiogenesis and long-term neurological recovery. Inhibition of miR-15a/16-1 function in cerebrovascular endothelium may be a legitimate therapeutic approach for stroke recovery.

Endothelium-targeted overexpression of Krüppel-like factor 11 protects the blood-brain barrier function after ischemic brain injury.

Microvascular endothelial cell (EC) injury and the subsequent blood-brain barrier (BBB) breakdown are frequently seen in many neurological disorders, including stroke. We have previously documented that peroxisome proliferator-activated receptor gamma (PPARγ)-mediated cerebral protection during ischemic insults needs Krüppel-like factor 11 (KLF11) as a critical coactivator. However, the role of endothelial KLF11 in cerebrovascular function and stroke outcome is unclear. This study is aimed at investigating the regulatory role of endothelial KLF11 in BBB preservation and neurovascular protection after ischemic stroke. EC-targeted overexpression of KLF11 significantly mitigated BBB leakage in ischemic brains, evidenced by significantly reduced extravasation of BBB tracers and infiltration of peripheral immune cells, and less brain water content. Endothelial cell-selective KLF11 transgenic (EC-KLF11 Tg) mice also exhibited smaller brain infarct and improved neurological function in response to ischemic insults. Furthermore, EC-targeted transgenic overexpression of KLF11 preserved cerebral tight junction (TJ) levels and attenuated the expression of pro-inflammatory factors in mice after ischemic stroke. Mechanistically, we demonstrated that KLF11 directly binds to the promoter of major endothelial TJ proteins including occludin and ZO-1 to promote their activities. Our data indicate that KLF11 functions at the EC level to preserve BBB structural and functional integrity, and therefore, confers brain protection in ischemic stroke. KLF11 may be a novel therapeutic target for the treatment of ischemic stroke and other neurological conditions involving BBB breakdown and neuroinflammation.

Regulatory microRNAs and vascular cognitive impairment and dementia.

Vascular cognitive impairment and dementia (VCID) is defined as a progressive dementia disease related to cerebrovascular injury and often occurs in aged populations. Despite decades of research, effective treatment for VCID is still absent. The pathological processes of VCID are mediated by the molecular mechanisms that are partly modulated at the post-transcriptional level. As small endogenous non-coding RNAs, microRNAs (miRs) can regulate target gene expression through post-transcriptional gene silencing. miRs have been reported to play an important role in the pathology of VCID and have recently been suggested as potential novel pharmacological targets for the development of new diagnosis and treatment strategies in VCID. In this review, we summarize the current understanding of VCID, the possible role of miRs in the regulation of VCID and attempt to envision future therapeutic strategies. Since manipulation of miR levels by either pharmacological or genetic approaches has shown therapeutic effects in experimental VCID models, we also emphasize the potential therapeutic value of miRs in clinical settings.

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

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

Noncoding RNAs and Stroke.

Over many years, extensive efforts have focused on the development and improvement of diagnostic and therapeutic strategies to reduce stroke-associated neurovascular damage, such as blood-brain barrier dysfunction, brain edema, parenchymal inflammation, and neural cell death. However, the only clinically applied pharmacological therapy to date for the treatment of acute ischemic stroke is thrombolysis. Because of the short therapeutic window of current thrombolytic therapy and the activation of various pathophysiological signaling cascades triggered after ischemic stroke, the development of new therapies is urgently required. Noncoding RNAs (ncRNAs) are defined as untranslated regulatory RNA molecules. Although ncRNAs with biological roles have been known for almost 60 years, they have within the past decade emerged as key mediators of posttranscriptional gene expression/function in pathological aspects of ischemic stroke. With properties of relative stability, specificity, and reproducibility, ncRNAs are considered to be promising as biomarkers and better candidates than proteins and genes for early recognition of the onset of disease. In this update, we summarized the current knowledge for three groups of ncRNAs in stroke, focusing on the role of long noncoding RNAs and circular RNAs as biomarkers for stroke and as targets for regulating large sets of genes in related pathways after ischemic stroke.

Long Non-Coding RNA Malat1 Regulates Angiogenesis in Hindlimb Ischemia.

Angiogenesis is a complex process that depends on the delicate regulation of gene expression. Dysregulation of transcription during angiogenesis often leads to various human diseases. Emerging evidence has recently begun to show that long non-coding RNAs (lncRNAs) may mediate angiogenesis in both physiological and pathological conditions; concurrently, underlying molecular mechanisms are largely unexplored. Previously, our lab identified metastasis associates lung adenocarcinoma transcript 1 (Malat1) as an oxygen-glucose deprivation (OGD)-responsive endothelial lncRNA. Here we reported that genetic deficiency of Malat1 leads to reduced blood vessel formation and local blood flow perfusion in mouse hind limbs at one to four weeks after hindlimb ischemia. Malat1 and vascular endothelial growth factor receptor 2 (VEGFR2) levels were found to be increased in both cultured mouse primary skeletal muscle microvascular endothelial cells (SMMECs) after 16 h OGD followed by 24 h reperfusion and in mouse gastrocnemius muscle that underwent hindlimb ischemia followed by 28 days of reperfusion. Moreover, Malat1 silencing by locked nucleic acid (LNA)-GapmeRs significantly reduced tube formation, cell migration, and cell proliferation in SMMEC cultures. Mechanistically, RNA subcellular isolation and RNA-immunoprecipitation experiments demonstrate that Malat1 directly targets VEGFR2 to facilitate angiogenesis. The results suggest that Malat1 regulates cell-autonomous angiogenesis through direct regulation of VEGFR2.