Impairment of pericyte-endothelium crosstalk leads to blood-brain barrier dysfunction following traumatic brain injury

Pericytes in Alzheimer's disease: Key players and therapeutic targets

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that leads to progressive cognitive decline and neuropathological changes. Pericytes, which are vessel mural cells on the basement membrane of capillaries, play a crucial role in regulating cerebrovascular functions and maintaining neurovascular unit integrity. Emerging research substantiates the involvement of pericytes in AD. This review provides a comprehensive overview of pericytes, including their structure, origin, and markers and various functions within the central nervous system. Emphatically, the review explores the intricate mechanisms through which pericytes contribute to AD, including their interactions with amyloid beta and apolipoprotein E, as well as various signaling pathways. The review also highlights potential for targeted pericyte therapy for AD, with a focus on stem cell therapy and drug treatments. Future research directions include the classification of pericyte subtypes, studies related to aging, and the role of pericytes in exosome-related mechanisms in AD pathology. In conclusion, this review consolidates current knowledge on the pivotal roles of pericytes in AD and their potential as therapeutic targets, providing valuable insights for future research and clinical interventions aimed at addressing the impact of AD on patients' lives.

Intravenous Administration of Anti-CD47 Antibody Augments Hematoma Clearance, Mitigates Acute Neuropathology, and Improves Cognitive Function in a Rat Model of Penetrating Traumatic Brain Injury

Traumatic brain injury (TBI)-induced intracerebral hematoma is a major driver of secondary injury pathology such as neuroinflammation, cerebral edema, neurotoxicity, and blood-brain barrier dysfunction, which contribute to neuronal loss, motor deficits, and cognitive impairment. Cluster of differentiation 47 (CD47) is an antiphagocytic cell surface protein inhibiting hematoma clearance. This study was designed to evaluate the safety and efficacy of blockade of CD47 via intravenous (i.v.) administration of anti-CD47 antibodies following penetrating ballistic-like brain injury (PBBI) with significant traumatic intracerebral hemorrhage (tICH). The pharmacokinetic (PK) profile of the anti-CD47 antibody elicited that antibody concentration decayed over 7 days post-administration. Blood tests and necropsy analysis indicated no severe adverse events following treatment. Cerebral hemoglobin levels were significantly increased after injury, however, anti-CD47 antibody administration at 0.1 mg/kg resulted in a significant reduction in cerebral hemoglobin levels at 72 h post-administration, indicating augmentation of hematoma clearance. Immunohistochemistry assessment of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule 1 (IBA1) demonstrated a significant reduction of GFAP levels in the lesion core and peri-lesional area. Based on these analyses, the optimal dose was identified as 0.1 mg/kg. Lesion volume showed a reduction following treatment. Rotarod testing revealed significant motor deficits in all injured groups but no significant therapeutic benefits. Spatial learning performance revealed significant deficits in all injured groups, which were significantly improved by the last testing day. Anti-CD47 antibody treated rats showed significantly improved attention deficits, but not retention scores. These results provide preliminary evidence that blockade of CD47 using i.v. administration of anti-CD47 antibodies may serve as a potential therapeutic for TBI with ICH.

From spreading depolarization to blood-brain barrier dysfunction: navigating traumatic brain injury for novel diagnosis and therapy

Considerable strides in medical interventions during the acute phase of traumatic brain injury (TBI) have brought improved overall survival rates. However, following TBI, people often face ongoing, persistent and debilitating long-term complications. Here, we review the recent literature to propose possible mechanisms that lead from TBI to long-term complications, focusing particularly on the involvement of a compromised blood-brain barrier (BBB). We discuss evidence for the role of spreading depolarization as a key pathological mechanism associated with microvascular dysfunction and the transformation of astrocytes to an inflammatory phenotype. Finally, we summarize new predictive and diagnostic biomarkers and explore potential therapeutic targets for treating long-term complications of TBI.

Assessment of cerebrovascular alterations induced by inflammatory response and oxidative-nitrative stress after traumatic intracranial hypertension and a potential mitigation strategy

The rapid perfusion of cerebral arteries leads to a significant increase in intracranial blood volume, exposing patients with traumatic brain injury to the risk of diffuse brain swelling or malignant brain herniation during decompressive craniectomy. The microcirculation and venous system are also involved in this process, but the precise mechanisms remain unclear. A physiological model of extremely high intracranial pressure was created in rats. This development triggered the TNF-α/NF-κB/iNOS axis in microglia, and released many inflammatory factors and reactive oxygen species/reactive nitrogen species, generating an excessive amount of peroxynitrite. Subsequently, the capillary wall cells especially pericytes exhibited severe degeneration and injury, the blood-brain barrier was disrupted, and a large number of blood cells were deposited within the microcirculation, resulting in a significant delay in the recovery of the microcirculation and venous blood flow compared to arterial flow, and this still persisted after decompressive craniectomy. Infliximab is a monoclonal antibody bound to TNF-α that effectively reduces the activity of TNF-α/NF-κB/iNOS axis. Treatment with Infliximab resulted in downregulation of inflammatory and oxidative-nitrative stress related factors, attenuation of capillary wall cells injury, and relative reduction of capillary hemostasis. These improved the delay in recovery of microcirculation and venous blood flow.

Pericyte derivation and transplantation for blood-CNS barrier reconstitution in CNS disorders

Disruption of the blood-central nervous system barrier (BCB) is increasingly recognized as a pathological factor in diseases and trauma of the central nervous system. Despite the neuropathological impact, current treatment modalities do not target the BCB; strategies to reconstitute the impaired BCB have been restricted to nutritional and dietary remedies. As an integral cell type in the neurovascular unit, pericytes are crucial to the development, maintenance, and repair of the BCB. As such, pericytes are well poised as cellular agents for reconstitution of the impaired BCB. Here, we summarize recent revelations regarding the role of BCB disruption in diseases and trauma of the central nervous system and highlight how pericytes are harnessed to provide targeted therapeutic effect in each case. This review will also address how recent advances in pericyte derivation strategies can serve to overcome practical hurdles in the clinical use of pericytes.

The role of reactive oxygen species in the regulation of the blood-brain barrier

The blood-brain barrier (BBB) regulates the exchange of metabolites and cells between the blood and brain, and maintains central nervous system homeostasis. Various factors affect BBB barrier functions, including reactive oxygen species (ROS). ROS can act as stressors, damaging biological molecules, but they also serve as secondary messengers in intracellular signaling cascades during redox signaling. The impact of ROS on the BBB has been observed in multiple sclerosis, stroke, trauma, and other neurological disorders, making blocking ROS generation a promising therapeutic strategy for BBB dysfunction. However, it is important to consider ROS generation during normal BBB functioning for signaling purposes. This review summarizes data on proteins expressed by BBB cells that can be targets of redox signaling or oxidative stress. It also provides examples of signaling molecules whose impact may cause ROS generation in the BBB, as well as discusses the most common diseases associated with BBB dysfunction and excessive ROS generation, open questions that arise in the study of this problem, and possible ways to overcome them.

Neurotoxic effects of metals on blood brain barrier impairment and possible therapeutic approaches

Exposure to neurotoxic and heavy metals (Pb2+, As3+, Mn2+, Cd2+, etc) has increased over time and has shown to negatively affect brain health. Heavy metals can cross the blood brain barrier (BBB) in various ways including receptor or carrier-mediated transport, passive diffusion, or transport via gaps in the endothelial cells of the brain. In high concentrations, these metals have been shown to cause structural and functional impairment to the BBB, by inducing oxidative stress, ion dyshomeostasis, tight junction (TJ) loss, astrocyte/pericyte damage and interference of gap junctions. The structural and functional impairment of the BBB results in increased BBB permeability, which ultimately leads to accumulation of these heavy metals in the brain and their subsequent toxicity. As a result of these effects, heavy metals are correlated with various neurological disorders. The pathological effects of these heavy metals can be effectively mitigated via chelation. In addition, it is possible to treat the associated disorders by counteracting the molecular mechanisms associated with the brain and BBB impairment.

An injectable refrigerated hydrogel for inducing local hypothermia and neuroprotection against traumatic brain injury in mice

BACKGROUND

Hypothermia is a promising therapy for traumatic brain injury (TBI) in the clinic. However, the neuroprotective outcomes of hypothermia-treated TBI patients in clinical studies are inconsistent due to several severe side effects. Here, an injectable refrigerated hydrogel was designed to deliver 3-iodothyronamine (T1AM) to achieve a longer period of local hypothermia for TBI treatment. Hydrogel has four advantages: (1) It can be injected into injured sites after TBI, where it forms a hydrogel and avoids the side effects of whole-body cooling. (2) Hydrogels can biodegrade and be used for controlled drug release. (3) Released T1AM can induce hypothermia. (4) This hydrogel has increased medical value given its simple operation and ability to achieve timely treatment.

METHODS

Pol/T hydrogels were prepared by a low-temperature mixing method and characterized. The effect of the Pol/T hydrogel on traumatic brain injury in mice was studied. The degradation of the hydrogel at the body level was observed with a small animal imager. Brain temperature and body temperature were measured by brain thermometer and body thermometer, respectively. The apoptosis of peripheral nerve cells was detected by immunohistochemical staining. The protective effect of the hydrogels on the blood-brain barrier (BBB) after TBI was evaluated by the Evans blue penetration test. The protective effect of hydrogel on brain edema after injury in mice was detected by Magnetic resonance (MR) in small animals. The enzyme linked immunosorbent assay (ELISA) method was used to measure the levels of inflammatory factors. The effects of behavioral tests on the learning ability and exercise ability of mice after injury were evaluated.

RESULTS

This hydrogel was able to cool the brain to hypothermia for 12 h while maintaining body temperature within the normal range after TBI in mice. More importantly, hypothermia induced by this hydrogel leads to the maintenance of BBB integrity, the prevention of cell death, the reduction of the inflammatory response and brain edema, and the promotion of functional recovery after TBI in mice. This cooling method could be developed as a new approach for hypothermia treatment in TBI patients.

CONCLUSION

Our study showed that injectable and biodegradable frozen Pol/T hydrogels to induce local hypothermia in TBI mice can be used for the treatment of traumatic brain injury.

Development and internal validation of a nomogram to predict temporary acute agitated delirium after surgery for chronic subdural hematoma in elderly patients: an analysis of the clinical database

Background

This study aimed to develop a nomogram for predicting temporary acute agitated delirium after surgery in patients with chronic subdural hematoma (CSH) without neurological compromise and hospitalized in the neurosurgery.

Methods

We included 289 patients with chronic subdural hematoma (CSH) from the medical information system of Yuebei People's Hospital of Shaoguan City, Guangdong Province, and collected 16 clinical indicators within 24 h of admission. We used the least absolute shrinkage and selection operator (LASSO) regression to identify risk factors. We established a multivariate logistic regression model and constructed a nomogram. We performed internal validation by 1,000 bootstrap samples; we plotted a receiver operating curve (ROC) and calculated the area under the curve (AUC), sensitivity, and specificity. We also evaluated the calibration of our model by the calibration curve and the Hosmer-Lemeshow goodness-of-fit test (HL test). We performed a decision curve analysis (DCA) and a clinical impact curve (CIC) to assess the net clinical benefit of our model.

Results

The nomogram included alcoholism history, hepatic insufficiency, verbal rating scale for postoperative pain (VRS), pre-hospital modified Rankin Scale (mRS), and preoperative hematoma thickness as predictors. Our model showed satisfactory diagnostic performance with an AUC value of 0.8474 in the validation set. The calibration curve and the HL test showed good agreement between predicted and observed outcomes (p = 0.9288). The DCA and CIC showed that our model had a high predictive ability for the occurrence of postoperative delirium in patients with CSDH.

Conclusion

We identified alcoholism, liver dysfunction, pre-hospital mRS, preoperative hematoma thickness, and postoperative VRS pain as predictors of postoperative delirium in chronic subdural hematoma patients. We developed and validated a multivariate logistic regression model and a nomogram.

Exploring the properties and potential of the neural extracellular matrix for next-generation regenerative therapies

The extracellular matrix (ECM) is a dynamic and complex network of proteins and molecules that surrounds cells and tissues in the nervous system and orchestrates a myriad of biological functions. This review carefully examines the diverse interactions between cells and the ECM, as well as the transformative chemical and physical changes that the ECM undergoes during neural development, aging, and disease. These transformations play a pivotal role in shaping tissue morphogenesis and neural activity, thereby influencing the functionality of the central nervous system (CNS). In our comprehensive review, we describe the diverse behaviors of the CNS ECM in different physiological and pathological scenarios and explore the unique properties that make ECM-based strategies attractive for CNS repair and regeneration. Addressing the challenges of scalability, variability, and integration with host tissues, we review how advanced natural, synthetic, and combinatorial matrix approaches enhance biocompatibility, mechanical properties, and functional recovery. Overall, this review highlights the potential of decellularized ECM as a powerful tool for CNS modeling and regenerative purposes and sets the stage for future research in this exciting field. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Neutralization of Interleukin 1-beta is associated with preservation of thalamic capillaries after experimental traumatic brain injury

Introduction

Traumatic brain injury to thalamo-cortical pathways is associated with posttraumatic morbidity. Diffuse mechanical forces to white matter tracts and deep grey matter regions induce an inflammatory response and vascular damage resulting in progressive neurodegeneration. Pro-inflammatory cytokines, including interleukin-1β (IL-1β), may contribute to the link between inflammation and the injured capillary network after TBI. This study investigates whether IL-1β is a key contributor to capillary alterations and changes in pericyte coverage in the thalamus and cortex after TBI.

Methods

Animals were subjected to central fluid percussion injury (cFPI), a model of TBI causing widespread axonal and vascular pathology, or sham injury and randomized to receive a neutralizing anti-IL-1β or a control, anti-cyclosporin A antibody, at 30 min post-injury. Capillary length and pericyte coverage of cortex and thalamus were analyzed by immunohistochemistry at 2- and 7-days post-injury.

Results and Conclusion

Our results show that early post-injury attenuation of IL-1β dependent inflammatory signaling prevents capillary damage by increasing pericyte coverage in the thalamus.

Repetitive head trauma and apoE4 induce chronic cerebrovascular alterations that impair tau elimination from the brain

Repetitive mild traumatic brain injuries (r-mTBI) sustained in the military or contact sports have been associated with the accumulation of extracellular tau in the brain, which may contribute to the pathogenesis of neurodegenerative tauopathies. The expression of the apolipoprotein E4 (apoE4) isoform has been associated with higher levels of tau in the brain, and worse clinical outcomes after r-mTBI, though the influence of apoE genotype on extracellular tau dynamics in the brain is poorly understood. We recently demonstrated that extracellular tau can be eliminated across blood-brain barrier (BBB), which is progressively impaired following r-mTBI. The current studies investigated the influence of repetitive mild TBI (r-mTBI) and apoE genotype on the elimination of extracellular solutes from the brain. Following intracortical injection of biotin-labeled tau into humanized apoE-Tr mice, the levels of exogenous tau residing in the brain of apoE4 mice were elevated compared to other isoforms, indicating reduced tau elimination. Additionally, we found exposure to r-mTBI increased tau residence in apoE2 mice, similar to our observations in E2FAD animals. Each of these findings may be the result of diminished tau efflux via LRP1 at the BBB, as LRP1 inhibition significantly reduced tau uptake in endothelial cells and decreased tau transit across an in vitro model of the BBB (basolateral-to-apical). Notably, we showed that injury and apoE status, (particularly apoE4) resulted in chronic alterations in BBB integrity, pericyte coverage, and AQP4 polarization. These aberrations coincided with an atypical reactive astrocytic gene signature indicative of diminished CSF-ISF exchange. Our work found that CSF movement was reduced in the chronic phase following r-mTBI (>18 months post injury) across all apoE genotypes. In summary, we show that apoE genotype strongly influences cerebrovascular homeostasis, which can lead to age-dependent deficiencies in the elimination of toxic proteins from the brain, like tau, particularly in the aftermath of head trauma.

Mitochondrial ferritin upregulation reduced oxidative stress and blood-brain-barrier disruption by maintaining cellular iron homeostasis in a neonatal rat model of germinal matrix hemorrhage

Germinal matrix hemorrhage (GMH) is a devasting neurological disease in premature newborns. After GMH, brain iron overload associated with hemoglobin degradation contributed to oxidative stress, causing disruption of the already vulnerable blood-brain barrier (BBB). Mitochondrial ferritin (FTMT), a novel mitochondrial outer membrane protein, is crucial in maintaining cellular iron homeostasis. We aimed to investigate the effect of FTMT upregulation on oxidative stress and BBB disruption associated with brain iron overload in rats. A total of 222 Sprague-Dawley neonatal rat pups (7 days old) were used to establish a collagenase-induced GMH model and an iron-overload model of intracerebral FeCl2 injection. Deferiprone was administered via gastric lavage 1 h after GMH and given daily until euthanasia. FTMT CRISPR Knockout and adenovirus (Ad)-FTMT were administered intracerebroventricularly 48 h before GMH and FeCl2 injection, respectively. Neurobehavioral tests, immunofluorescence, Western blot, Malondialdehyde measurement, and brain water content were performed to evaluate neurobehavior deficits, oxidative stress, and BBB disruption, respectively. The results demonstrated that brain expressions of iron exporter Ferroportin (FPN) and antioxidant glutathione peroxidase 4 (GPX4) as well as BBB tight junction proteins including Claudin-5 and Zona Occulta (ZO)-1 were found to be decreased at 72 h after GMH. FTMT agonist Deferiprone attenuated oxidative stress and preserved BBB tight junction proteins after GMH. These effects were partially reversed by FTMT CRISPR Knockout. Iron overload by FeCl2 injection resulted in oxidative stress and BBB disruption, which were improved by Ad-FTMT mediated FTMT overexpression. Collectively, FTMT upregulation is neuroprotective against brain injury associated with iron overload. Deferiprone reduced oxidative stress and BBB disruption by maintaining cellular iron homeostasis partially by the upregulating of FTMT after GMH. Deferiprone may be an effective treatment for patients with GMH.

Progress of the study of pericytes and their potential research value in adenomyosis

Pericytes (PCs) are versatile cells integral to the microcirculation wall, exhibiting specific stem cell traits. They are essential in modulating blood flow, ensuring vascular permeability, maintaining homeostasis, and aiding tissue repair process. Given their involvement in numerous disease-related pathological and physiological processes, the regulation of PCs has emerged as a focal point of research. Adenomyosis is characterized by the presence of active endometrial glands and stroma encased by an enlarged and proliferative myometrial layer, further accompanied by fibrosis and new blood vessel formation. This distinct pathological condition might be intricately linked with PCs. This article comprehensively reviews the markers associated with PCs, their contributions to angiogenesis, blood flow modulation, and fibrotic processes. Moreover, it provides a comprehensive overview of the current research on adenomyosis pathophysiology, emphasizing the potential correlation and future implications regarding PCs and the development of adenomyosis.

Progressive Age-Associated Blood-Brain Barrier Leak/Dysfunction-Nexus of Neurodegenerative Disease Using MRI Markers to Identify Preclinical Disease and Potential New Targets for Future Treatments

This review article focuses on the upstream pertinent pathophysiology leading to neurodegenerative disease. Specifically, the nexus appears to be blood-brain barrier (BBB) leakiness resulting in a two-prong inflammatory disease spectrum damaging the microvasculature and corrupting protein synthesis and degradation with accumulating misfolded toxic proteins. The suboptimal results of removing misfolded proteins mean a new approach to disease in the preclinical state is required aimed at other targets. Validated noninvasive imaging and serologic biomarkers of early preclinical disease implemented in the high-risk patient cohort along with periodic surveillance once effective treatments are developed will be required. This review discusses the physiology and pathophysiology of the BBB, new MRI imaging techniques identifying the leak, and altered fluid dynamic effects in the preclinical state. The risk factors for disease development, preventative measures, and potential treatment targets are also discussed.

ICAM-1 Deletion Using CRISPR/Cas9 Protects the Brain from Traumatic Brain Injury-Induced Inflammatory Leukocyte Adhesion and Transmigration Cascades by Attenuating the Paxillin/FAK-Dependent Rho GTPase Pathway

Intercellular adhesion molecule-1 (ICAM-1) is identified as an initiator of neuroinflammatory responses that lead to neurodegeneration and cognitive and sensory-motor deficits in several pathophysiological conditions including traumatic brain injury (TBI). However, the underlying mechanisms of ICAM-1-mediated leukocyte adhesion and transmigration and its link with neuroinflammation and functional deficits following TBI remain elusive. Here, we hypothesize that blocking of ICAM-1 attenuates the transmigration of leukocytes to the brain and promotes functional recovery after TBI. The experimental TBI was induced in vivo by fluid percussion injury (25 psi) in male and female wild-type and ICAM-1-/- mice and in vitro by stretch injury (3 psi) in human brain microvascular endothelial cells (hBMVECs). We treated hBMVECs and animals with ICAM-1 CRISPR/Cas9 and conducted several biochemical analyses and demonstrated that CRISPR/Cas9-mediated ICAM-1 deletion mitigates blood-brain barrier (BBB) damage and leukocyte transmigration to the brain by attenuating the paxillin/focal adhesion kinase (FAK)-dependent Rho GTPase pathway. For analyzing functional outcomes, we used a cohort of behavioral tests that included sensorimotor functions, psychological stress analyses, and spatial memory and learning following TBI. In conclusion, this study could establish the significance of deletion or blocking of ICAM-1 in transforming into a novel preventive approach against the pathophysiology of TBI.

Targeting blood brain barrier-Remote ischemic conditioning alleviates cognitive impairment in female APP/PS1 rats

AIMS

Alzheimer's disease (AD) is a significant global health concern, and it is crucial that we find effective methods to prevent or slow down AD progression. Recent studies have highlighted the essential role of blood vessels in clearing Aβ, a protein that contributes to AD. Scientists are exploring blood biomarkers as a potential tool for future AD diagnosis. One promising method that may help prevent AD is remote ischemic conditioning (RIC). RIC involves using sub-lethal ischemic-reperfusion cycles on limbs. However, a comprehensive understanding of how RIC can prevent AD and its long-term effectiveness is still lacking. Further research is essential to fully comprehend the potential benefits of RIC in preventing AD.

METHODS

Female wild-type (WT) and APP/PS1 transgenic rats, aged 12 months, underwent ovariectomy and were subsequently assigned to WT, APP/PS1, and APP/PS1 + RIC groups. RIC was conducted five times a week for 4 weeks. The rats' depressive and cognitive behaviors were evaluated using force swimming, open-field tests, novel objective recognition, elevated plus maze, and Barnes maze tests. Evaluation of the neurovascular unit (NVU), synapses, vasculature, astrocytes, and microglia was conducted using immunofluorescence staining (IF), Western blot (WB), and transmission electron microscopy (TEM). Additionally, the cerebro-vasculature was examined using micro-CT, and cerebral blood flow (CBF) was measured using Speckle Doppler. Blood-brain barrier (BBB) permeability was determined by measuring the Evans blue leakage. Finally, Aβ levels in the rat frontal cortex were measured using WB, ELISA, or IF staining.

RESULTS

RIC enhanced memory-related protein expression and rescued depressive-like behavior and cognitive decline in APP/PS1 transgenic rats. Additionally, the intervention protected NVU in the rat frontal cortex, as evidenced by (1) increased expression of TJ (tight junction) proteins, pericyte marker PDGFRβ, and glucose transporter 1 (GLUT1), as well as decreased VCAM1; (2) mitigation of ultrastructure impairment in neuron, cerebral vascular, and astrocyte; (3) upregulation of A2 astrocyte phenotype markers and downregulation of A1 phenotype markers, indicating a shift toward a healthier phenotype. Correspondingly, RIC intervention alleviated neuroinflammation, as evidenced by the decreased Iba1 level, a microglia marker. Meanwhile, RIC intervention elevated CBF in frontal cortex of the rats. Notably, RIC intervention effectively suppressed Aβ toxicity, as demonstrated by the enhancement of α-secretase and attenuation of β-secretase (BACE1) and γ- secretase and Aβ1-42 and Aβ1-40 levels as well.

CONCLUSION

Chronic RIC intervention exerts vascular and neuroprotective roles, suggesting that RIC could be a promising therapeutic strategy targeting the BBB and NVU during AD development.

Traumatic Brain Injury in the Long-COVID Era

Major determinants of the biological background or reserve, such as age, biological sex, comorbidities (diabetes, hypertension, obesity, etc.), and medications (e.g., anticoagulants), are known to affect outcome after traumatic brain injury (TBI). With the unparalleled data richness of coronavirus disease 2019 (COVID-19; ∼375,000 and counting!) as well as the chronic form, long-COVID, also called post-acute sequelae SARS-CoV-2 infection (PASC), publications (∼30,000 and counting) covering virtually every aspect of the diseases, pathomechanisms, biomarkers, disease phases, symptomatology, etc., have provided a unique opportunity to better understand and appreciate the holistic nature of diseases, interconnectivity between organ systems, and importance of biological background in modifying disease trajectories and affecting outcomes. Such a holistic approach is badly needed to better understand TBI-induced conditions in their totality. Here, I briefly review what is known about long-COVID/PASC, its underlying-suspected-pathologies, the pathobiological changes induced by TBI, in other words, the TBI endophenotypes, discuss the intersection of long-COVID/PASC and TBI-induced pathobiologies, and how by considering some of the known factors affecting the person's biological background and the inclusion of mechanistic molecular biomarkers can help to improve the clinical management of TBI patients.

Evidence Implicating Blood-Brain Barrier Impairment in the Pathogenesis of Acquired Epilepsy following Acute Organophosphate Intoxication

Organophosphate (OP) poisoning can trigger cholinergic crisis, a life-threatening toxidrome that includes seizures and status epilepticus. These acute toxic responses are associated with persistent neuroinflammation and spontaneous recurrent seizures (SRS), also known as acquired epilepsy. Blood-brain barrier (BBB) impairment has recently been proposed as a pathogenic mechanism linking acute OP intoxication to chronic adverse neurologic outcomes. In this review, we briefly describe the cellular and molecular components of the BBB, review evidence of altered BBB integrity following acute OP intoxication, and discuss potential mechanisms by which acute OP intoxication may promote BBB dysfunction. We highlight the complex interplay between neuroinflammation and BBB dysfunction that suggests a positive feedforward interaction. Lastly, we examine research from diverse models and disease states that suggest mechanisms by which loss of BBB integrity may contribute to epileptogenic processes. Collectively, the literature identifies BBB impairment as a convergent mechanism of neurologic disease and justifies further mechanistic research into how acute OP intoxication causes BBB impairment and its role in the pathogenesis of SRS and potentially other long-term neurologic sequelae. Such research is critical for evaluating BBB stabilization as a neuroprotective strategy for mitigating OP-induced epilepsy and possibly seizure disorders of other etiologies. SIGNIFICANCE STATEMENT: Clinical and preclinical studies support a link between blood-brain barrier (BBB) dysfunction and epileptogenesis; however, a causal relationship has been difficult to prove. Mechanistic studies to delineate relationships between BBB dysfunction and epilepsy may provide novel insights into BBB stabilization as a neuroprotective strategy for mitigating epilepsy resulting from acute organophosphate (OP) intoxication and non-OP causes and potentially other adverse neurological conditions associated with acute OP intoxication, such as cognitive impairment.

Diffusion tensor imaging and plasma immunological biomarker panel in a rat traumatic brain injury (TBI) model and in human clinical TBI

Introduction

Neuroinflammatory reactions play a significant role in the pathology and long-term consequences of traumatic brain injury (TBI) and may mediate salutogenic processes that white matter integrity. This study aimed to investigate the relationship between inflammatory markers and white matter integrity following TBI in both a rat TBI model and clinical TBI cases.

Methods

In the rat model, blood samples were collected following a controlled cortical impact (CCI) to assess a panel of inflammatory markers; MR-based diffusion tensor imaging (DTI) was employed to evaluate white matter integrity 60 days post-injury. 15 clinical TBI patients were similarly assessed for a panel of inflammatory markers and DTI post-intensive care unit discharge. Blood samples from healthy controls were used for comparison of the inflammatory markers.

Results

Time-dependent elevations in immunological markers were observed in TBI rats, with a correlation to preserved fractional anisotropy (FA) in white matter. Specifically, TBI-induced increased plasma levels of IL-1β, IL-6, G-CSF, CCL3, CCL5, and TNF-α were associated with higher white matter integrity, as measured by FA. Clinical cases had similar findings: elevated inflammatory markers (relative to controls) were associated with preservation of FA in vulnerable white matter regions.

Discussion

Inflammatory markers in post-TBI plasma samples are ambivalent with respect to prediction of favourable outcome versus a progression to more pervasive pathology and morbidity.

The role of platelets in the blood-brain barrier during brain pathology

Platelets play critical roles in maintaining hemostasis. The blood brain barrier (BBB), a significant physical and metabolic barrier, helps maintain physiological stability by limiting transportations between the blood and neural tissues. When the brain undergoes inflammation, tumor, trauma, or bleeding, the platelet responses to help with maintaining BBB homeostasis. In the traditional point of view, activated platelets aggregate to form thrombi which cover the gaps of the blood vessels to protect BBB. However, increasing evidences indicate that platelets may harm BBB by enhancing vascular permeability. Hereby, we reviewed recently published articles with a special focus on the platelet-mediated damage of BBB. Factors released by platelets can induce BBB permeability, which involve platelet-activating factors (PAF), P-selectin, ADP, platelet-derived growth factors (PDGF) superfamily proteins, especially PDGF-AA and PDGF-CC, etc. Platelets can also secrete Amyloid-β (Aβ), which triggers neuroinflammation and downregulates the expression of tight junction molecules such as claudin-5 to damage BBB. Additionally, platelets can form aggregates with neutrophils to release reactive oxygen species (ROS), which can destroy the DNA, proteins, and lipids of endothelial cells (ECs). Moreover, platelets participate in neuroinflammation to affect BBB. Conversely, some of the platelet released factors such as PDGF-BB, protects BBB. In summary, platelets play dual roles in BBB integrity and the related mechanisms are reviewed.

Mild traumatic brain injury induces pericyte detachment independent of stroke vulnerability

Mild traumatic brain injury (mTBI) is an independent risk factor for ischemic stroke and can result in poorer outcomes- an effect presumed to involve the cerebral vasculature. Here we tested the hypothesis that mTBI-induced pericyte detachment from the cerebrovascular endothelium is responsible for worsened stroke outcomes. We performed a mild closed-head injury and/or treated C57/bl6 mice with imatinib mesylate, a tyrosine kinase inhibitor that induces pericyte detachment. The time course of pericyte detachment was assessed 7, 14, and 28 days post injury (DPI). To test the role of pericytes in TBI-induced exacerbation of ischemic stroke outcomes, we induced mTBI and/or treated mice with imatinib for one week prior to transient middle cerebral artery occlusion. We found that injury promoted pericyte detachment from the vasculature commensurate with the levels of detachment seen in imatinib-only treated animals, and that the detachment persisted for at least 14DPI, but recovered to sham levels by 28DPI. Further, mTBI, but not imatinib-induced pericyte detachment, increased infarct volume. Thus, we conclude that the transient detachment of pericytes caused by mTBI may not be sufficient to exacerbate subsequent ischemic stroke damage. These data have important implications for understanding cerebrovascular dysfunction following mTBI and potential mechanisms of increased risk for future ischemic strokes.

Effect of transcutaneous electrical acupoint stimulation on remifentanil dosage during craniotomy aneurysm clipping: a prospective, randomized controlled study

BACKGROUND

Craniotomy aneurysm clipping is one of the main treatments for intracranial aneurysm (IA). Endotracheal intubation and intraoperative operation may induce dramatic hemodynamic fluctuations and increase the risk of aneurysm rupture. Intraoperative high-dose opioid use is the main measure to reduce the intraoperative stress response, but it increases the incidence of complications such as postoperative vomiting and delayed awakening. Transcutaneous electrical acupoint stimulation (TEAS) stimulates β-endorphin expression levels and reduces opioid requirements. In this study, we aimed to assess the effects of TEAS on remifentanil dosage and oxidative stress (OS) in craniotomy aneurysm clipping.

METHOD

Forty-two patients with craniotomy aneurysm clipping were randomized into two groups: the TEAS group (T group) and the sham TEAS group (S group). "Hegu" (LI4), "Neiguan" (PC6) and "Zusanli" points (ST36) were selected, and a "HANS" percutaneous acupoint electrical stimulator was used for intervention 30 min before anesthesia induction until the end of the operation. The primary outcome was intraoperative remifentanil dosage. The secondary outcomes were intraoperative propofol dosage, mean arterial pressure (MAP) and heart rate (HR) 5 min before the TEAS intervention (T0), 5 min before head holder pinning (T1), immediately after pinning (T2), 5 min before craniotomy (T3), immediately after craniotomy (T4), at craniotomy (T5), and at the end of surgery (T6), as well as serum β-endorphin levels at T1, T2 and T6 and neuron-specific enolase (NSE), S100β, superoxide dismutase (SOD) and malondialdehyde (MDA) levels at T1, T2 and 24 h after surgery (T7).

RESULTS

The dosage of remifentanil in the T group was reduced compared to that in the S group (P < 0.05). At T2, T4 and T5, the MAP and HR in the T group were lower than those in the S group (P < 0.05). At T2 and T7, the levels of NSE, S100β and MDA in group T were lower than those in group S (P < 0.05), while the SOD levels in group T were higher than those in group S (P < 0.05).

CONCLUSIONS

The use of TEAS can reduce the dosage of remifentanil and reduce hemodynamic fluctuations during craniotomy aneurysm clipping. It reduces the occurrence of OS and central nervous system damage during surgery and has a certain brain protective effect.

TRIAL REGISTRATION

ChiCTR2100052353. https://www.chictr.org.cn/about.html .

Increased Neuron-Specific Enolase Level Predicts Symptomatic Intracranial Hemorrhage in Patients with Ischemic Stroke Treated with Endovascular Treatment

BACKGROUND

Neuron-specific enolase (NSE), which is a highly specific marker for neurons, could be a predictor for prognosis in patients with symptomatic intracranial hemorrhage (sICH) with acute ischemic stroke who are receiving endovascular treatment (EVT). This study aimed to investigate the relationship between NSE and sICH in patients with acute anterior circulation stroke undergoing EVT.

METHODS

A total of 215 consecutive patients with acute stroke treated with EVT were included. Patients with stroke and acute anterior circulation occlusion, receiving EVT treated at our hospital, were enrolled between January 2017 and August 2021. NSE level was measured on arrival at the neurology intensive care unit after EVT. The patients were divided into 2 groups according to whether sICH was present. Univariate and multivariate analyses were performed. NSE level was also incorporated into the TAG score (modified Thrombolysis in Cerebral Infarction score, Alberta Stroke Program Early CT Score, and glucose level), which was developed as a scoring system to predict sICH, and the prediction capability was compared with the TAG score alone. Causal inference was performed using the package DoWhy in Python to evaluate the causal relationship between NSE and sICH.

RESULTS

The area under the curve (AUC) value of NSE showed moderate accuracy, with an AUC value of 0.729 (95% confidence interval, 0.655-0.795; P < 0.001). The NSE cutoff value was set at 23.88 ng/mL. When the NSE level ≥23.88 ng/mL, the sensitivity was 58.33% and the specificity was 78.72% (P < 0.001). The AUC for the TAG + NSE score was 0.801 compared with an AUC of 0.632 for the TAG score (Z = 2.034; P = 0.042). A causal inference model using the DoWhy library shows a proportional relationship between NSE and the diagnosis of sICH.

CONCLUSIONS

This study is the first to show that increased NSE level is an independent predictor of sICH in patients with acute anterior circulation stroke who are undergoing endovascular treatment.

Pericyte dysfunction is a key mediator of the risk of cerebral ischemia

Pericytes are critical yet understudied cells that are a central component of the neurovascular unit. They are connected to the cerebrovascular endothelium and help control vascular contractility and maintain the blood-brain barrier. Pericyte dysfunction has the potential to mediate many of the deleterious vascular consequences of ischemic stroke. Current therapeutics are designed to be administered after stroke onset and limit damage, but there are few options to target vascular risk factors pre-ischemia which likely contribute to stroke outcomes. Here, we focus on the role of pericytes in health and disease, and discuss how pericyte dysfunction can increase the risk of ischemic injury. Additionally, we note that despite the importance of pericytes in cerebrovascular disease, there are relatively few current therapeutic options that target pericyte function.

Pericyte-derived exosomal miR-210 improves mitochondrial function and inhibits lipid peroxidation in vascular endothelial cells after traumatic spinal cord injury by activating JAK1/STAT3 signaling pathway

BACKGROUND

Spinal cord injury (SCI) remains a significant health concern, with limited available treatment options. This condition poses significant medical, economic, and social challenges. SCI is typically categorized into primary and secondary injuries. Inflammation, oxidative stress, scar formation, and the immune microenvironment impede axon regeneration and subsequent functional restoration. Numerous studies have shown that the destruction of the blood-brain barrier (BBB) and microvessels is a crucial factor in severe secondary injury. Additionally, reactive oxygen species (ROS)-induced lipid peroxidation significantly contributes to endothelial cell death. Pericytes are essential constituents of the BBB that share the basement membrane with endothelial cells and astrocytes. They play a significant role in the establishment and maintenance of BBB.

RESULTS

Immunofluorescence staining at different time points revealed a consistent correlation between pericyte coverage and angiogenesis, suggesting that pericytes promote vascular repair via paracrine signaling. Pericytes undergo alterations in cellular morphology and the transcriptome when exposed to hypoxic conditions, potentially promoting angiogenesis. We simulated an early ischemia-hypoxic environment following SCI using glucose and oxygen deprivation and BBB models. Co-culturing pericytes with endothelial cells improved barrier function compared to the control group. However, this enhancement was reduced by the exosome inhibitor, GW4869. In vivo injection of exosomes improved BBB integrity and promoted motor function recovery in mice following SCI. Subsequently, we found that pericyte-derived exosomes exhibited significant miR-210-5p expression based on sequencing analysis. Therefore, we performed a series of gain- and loss-of-function experiments in vitro.

CONCLUSION

Our findings suggest that miR-210-5p regulates endothelial barrier function by inhibiting JAK1/STAT3 signaling. This process is achieved by regulating lipid peroxidation levels and improving mitochondrial function, suggesting a potential mechanism for restoration of the blood-spinal cord barrier (BSCB) after SCI.

Pericytes are protective in experimental pneumococcal meningitis through regulating leukocyte infiltration and blood-brain barrier function

BACKGROUND

Brain pericytes participate in the regulation of cerebral blood flow and the maintenance of blood-brain barrier integrity. Because of their perivascular localization, their receptor repertoire, and their potential ability to respond to inflammatory and infectious stimuli by producing various cytokines and chemokines, these cells are also thought to play an active role in the immune response to brain infections. This assumption is mainly supported by in vitro studies, investigations in in vivo disease models are largely missing. Here, we analysed the role of brain pericytes in pneumococcal meningitis, in vitro and in vivo in two animal models of pneumococcal meningitis.

METHODS

Primary murine and human pericytes were stimulated with increasing concentrations of different serotypes of Streptococcus pneumoniae in the presence or absence of Toll-like receptor inhibitors and their cell viability and cytokine production were monitored. To gain insight into the role of pericytes in brain infection in vivo, we performed studies in a zebrafish embryo model of pneumococcal meningitis in which pericytes were pharmacologically depleted. Furthermore, we analyzed the impact of genetically induced pericyte ablation on disease progression, intracranial complications, and brain inflammation in an adult mouse model of this disease.

RESULTS

Both murine and human pericytes reacted to pneumococcal exposure with the release of selected cytokines. This cytokine release is pneumolysin-dependent, TLR-dependent in murine (but not human) pericytes and can be significantly increased by macrophage-derived IL-1b. Pharmacological depletion of pericytes in zebrafish embryos resulted in increased cerebral edema and mortality due to pneumococcal meningitis. Correspondingly, in an adult mouse meningitis model, a more pronounced blood-brain barrier disruption and leukocyte infiltration, resulting in an unfavorable disease course, was observed following genetic pericyte ablation. The degree of leukocyte infiltration positively correlated with an upregulation of chemokine expression in the brains of pericyte-depleted mice.

CONCLUSIONS

Our findings show that pericytes play a protective role in pneumococcal meningitis by impeding leukocyte migration and preventing blood-brain barrier breaching. Thus, preserving the integrity of the pericyte population has the potential as a new therapeutic strategy in pneumococcal meningitis.

Bacteroides vulgatus alleviates dextran sodium sulfate-induced colitis and depression-like behaviour by facilitating gut-brain axis balance

Background

Patients with inflammatory bowel disease (IBD) have a higher prevalence of depression. Gut microbiota dysbiosis plays an important role in IBD and depression. However, few studies have explored the characteristic microbiota of patients with IBD and depression (IBDD), or their role in IBDD.

Methods

We performed deep metagenomic sequencing and 16S rDNA quantitative PCR to characterise the gut microbial communities of patients with IBDD and patients with IBD without depression (IBDND). We then assessed the effect of the microbiota on colitis and depression in mouse models of dextran sulfate sodium salt (DSS)-induced colitis and lipopolysaccharide (LPS)-induced depression. Furthermore, liquid chromatography-tandem mass spectrometry was used to analyse the microbiota-derived metabolites involved in gut-brain communication. Evans Blue tracer dye was used to assess blood-brain barrier (BBB) permeability.

Results

Our results showed that the faecal abundance of Bacteroides vulgatus (B. vulgatus) was lower in patients with IBDD than in those with IBDND. In the DSS-induced colitis mouse model, the B. vulgatus group showed a significantly lower disease activity index score, lesser weight loss, and longer colon length than the DSS group. Moreover, B. vulgatus relieved depression-like behaviour in the DSS-induced colitis mouse model and in the LPS-induced depression mouse model. Furthermore, the key metabolite of B. vulgatus was p-hydroxyphenylacetic acid (4-HPAA), which was found to relieve intestinal inflammation and alleviate depression-like behaviours in mouse models. By increasing the expression of the tight junction protein claudin-5 in the vascular endothelium of the BBB, B. vulgatus and 4-HPAA play critical roles in gut-brain communication.

Conclusion

B. vulgatus and B. vulgatus-derived 4-HPAA ameliorated intestinal inflammation and relieved depressive symptoms through the gut-brain axis. Thus, administration of B. vulgatus or 4-HPAA supplementation is a promising therapeutic strategy for treating IBD, particularly IBDD.

Cranial venous-outflow obstruction promotes neuroinflammation via ADAM17/solTNF-α/NF-κB pathway following experimental TBI

Traumatic brain injury (TBI) is a global public health problem. As an important cause of secondary injury, cerebrovascular reaction can cause secondary bleeding, venous sinus thrombosis, and malignant brain swelling. Recent clinical studies have confirmed that intracranial venous return disorder is closely related to the prognosis of patients, yet the specific molecular mechanism involved in this process is still unclear. This study used an acute subdural hematoma (ASDH) model with cranial venous outflow obstruction (CVO) to explore how CVO aggravates the pathological process after TBI, especially for inflammation and tissue damage. The results suggest that intracranial venous return disorder exacerbates neurological deficits and brain edema in rats with ASDH by aggravating the destruction of endothelial cell tight junctions (TJs) proteins and promoting the expression of inflammatory factors, the activation of microglia and expression of recombinant A disintegrin and metalloprotease 17 (ADAM17) as well as the secretion of solTNF-α, a soluble form of tumor necrosis factor-alpha (TNFα), which in turn increase IκB-α ((inhibitor of the transcription factor nuclear factor-κB) and NF-κB p65. Our study revealed a molecular basis of how CVO aggravates inflammation and tissue damage.

Methylglyoxal, a highly reactive dicarbonyl compound, as a threat for blood brain barrier integrity

The brain is a highly metabolically active organ requiring a large amount of glucose. Methylglyoxal (MGO), a by-product of glucose metabolism, is known to be involved in microvascular dysfunction and is associated with reduced cognitive function. Maintenance of the blood-brain barrier (BBB) is essential to maintain optimal brain function and a large amount of evidence indicates negative effects of MGO on BBB integrity. In this review, we summarized the current literature on the effect of MGO on the different cell types forming the BBB. BBB damage by MGO most likely occurs in brain endothelial cells and mural cells, while astrocytes are most resistant to MGO. Microglia on the other hand appear to be not directly influenced by MGO but rather produce MGO upon activation. Although there is clear evidence that MGO affects components of the BBB, the impact of MGO on the BBB as a multicellular system warrants further investigation. Diminishing MGO stress can potentially form the basis for new treatment strategies for maintaining optimal brain function.

Long-term application of silver nanoparticles in dental restoration materials: potential toxic injury to the CNS

Silver nanoparticles (AgNPs) have durable and remarkable antimicrobial effects on pathogenic microorganisms, such as bacteria and fungi, in dental plaques. As such, they are widely added to dental restoration materials, including composite resins, denture bases, adhesives, and implants, to solve the problems of denture stomatitis, peri-implant inflammation, and oral infection caused by the long-term use of these dental restoration materials. However, AgNPs can be absorbed into the blood circulatory system through the nasal/oral mucosa, lungs, gastrointestinal tract, skin, and other pathways and then distributed into the lungs, kidneys, liver, spleen, and testes, thereby causing toxic injury to these tissues and organs. It can even be transported across the blood-brain barrier (BBB) and continuously accumulate in brain tissues, causing injury and dysfunction of neurons and glial cells; consequently, neurotoxicity occurs. Other nanomaterials with antibacterial or remineralization properties are added to dental restoration materials with AgNPs. However, studies have yet to reveal the neurotoxicity caused by dental restoration materials containing AgNPs. In this review, we summarize the application of AgNPs in dental restoration materials, the mechanism of AgNPs in cytotoxicity and toxic injury to the BBB, and the related research on the accumulation of AgNPs to cause changes of neurotoxicity. We also discuss the mechanisms of neurotoxicity caused by AgNPs and the mode and rate of AgNPs released from dental restorative materials added with AgNPs to evaluate the probability of neurotoxic injury to the central nervous system (CNS), and then provide a theoretical basis for developing new composite dental restoration materials. Mechanism of neurotoxicity caused by AgNPs: AgNPs in the blood circulation enter the brain tissue after being transported across the BBB through transendothelial cell pathway and paracellular transport pathway, and continuously accumulate in brain tissue, causing damage and dysfunction of neurons and glial cells which ultimately leads to neurotoxicity. The uptake of AgNPs by neurons, astrocytes and microglia causes damage to these cells. AgNPs with non-neurotoxic level often increases the secretion of a variety of cytokines, up-regulates the expression of metallothionein in glial cells, even up-regulates autophagy and inflammation response to protect neurons from the toxic damage of AgNPs. However, the protective effect of glial cells induced by AgNPs exposure to neurotoxic levels is insufficient, which leads to neuronal damage and dysfunction and even neuronal programmed cell death, eventually cause neurotoxicity.

A method to isolate human dermal microvascular pericytes without the use of magnetic beads sorting in vitro

Human dermal microvascular pericytes (HDMPCs) are a critical component of the skin flap microvasculature and play a role in regulating flap blood flow and integrity. Pericytes were isolated mostly via magnetic bead sorting in the published literature. In this study, we discuss in detail how to separate and concentrate pericytes from human facial flaps using enzyme digestion and differential adherence instead of magnetic bead sorting. Cultured HDMPCs were seen to have well-spread irregular edges, with most cells having two longitudinal pericytic processes. The phalloidin staining revealed that HDMPCs had prominent stress fibers, and the nucleus deviated to the side that interacted with the neighboring pericytic processes. Flow cytometry analysis showed that the positive rates of NG2 in the first and second passages were 91.2% ± 0.7% and 98.2% ± 0.1% separately. And the immunofluorescence and western blot results demonstrated a positive expression of α smooth muscle actin (αSMA), platelet-derived growth factor receptor β (PDGFRβ), and NG-2, while the endothelial cell marker CD31 was negatively expressed. In summary, we established a straightforward methodology for selectively isolating and identifying HDMPCs as well as generating high-purity cell cultures in vitro without the use of magnetic bead sorting.

Omega-3 Polyunsaturated Fatty Acids Protect Neurological Function After Traumatic Brain Injury by Suppressing Microglial Transformation to the Proinflammatory Phenotype and Activating Exosomal NGF/TrkA Signaling

The transformation of microglia to a pro-inflammatory phenotype at the site of traumatic brain injury (TBI) drives the progression of secondary neurodegeneration and irreversible neurological impairment. Omega-3 polyunsaturated fatty acids (PUFA) have been shown to suppress this phenotype transformation, thereby reducing neuroinflammation following TBI, but the molecular mechanisms are unknown. We found that Omega-3 PUFA suppressed the expression of disintegrin metalloproteinase (ADAM17), the enzyme required to convert tumor necrosis factor-α (TNF-α) to the soluble form, thereby inhibiting the TNF-α/NF-κB pathway both in vitro and in a mouse model of TBI. Omega-3 PUFA also prevented the reactive transformation of microglia and promoted the secretion of microglial exosomes containing nerve growth factor (NGF), activating the neuroprotective NGF/TrkA pathway both in culture and TBI model mice. Moreover, Omega-3 PUFA suppressed the pro-apoptotic NGF/P75NTR pathway at the TBI site and reduced apoptotic neuronal death, brain edema, and disruption of the blood-brain barrier. Finally, Omega-3 PUFA preserved sensory and motor function as assessed by two broad-spectrum test batteries. The beneficial effects of Omega-3 PUFA were blocked by an ADAM17 promotor and by a NGF inhibitor, confirming the pathogenic function of ADAM17 and the central neuroprotective role of NGF. Collectively, these findings provide a strong experimental basis for Omega-3 PUFA as a potential clinical treatment for TBI.

Extracellular matrix-induced signaling pathways in mesenchymal stem/stromal cells

The extracellular matrix (ECM) is a crucial component of the stem cell microenvironment, or stem-cell niches, and contributes to the regulation of cell behavior and fate. Accumulating evidence indicates that different types of stem cells possess a large variety of molecules responsible for interactions with the ECM, mediating specific epigenetic rearrangements and corresponding changes in transcriptome profile. Signals from the ECM are crucial at all stages of ontogenesis, including embryonic and postnatal development, as well as tissue renewal and repair. The ECM could regulate stem cell transition from a quiescent state to readiness to perceive the signals of differentiation induction (competence) and the transition between different stages of differentiation (commitment). Currently, to unveil the complex networks of cellular signaling from the ECM, multiple approaches including screening methods, the analysis of the cell matrixome, and the creation of predictive networks of protein-protein interactions based on experimental data are used. In this review, we consider the existing evidence regarded the contribution of ECM-induced intracellular signaling pathways into the regulation of stem cell differentiation focusing on mesenchymal stem/stromal cells (MSCs) as well-studied type of postnatal stem cells totally depended on signals from ECM. Furthermore, we propose a system biology-based approach for the prediction of ECM-mediated signal transduction pathways in target cells. Video Abstract.

Low-intensity open-field blast exposure effects on neurovascular unit ultrastructure in mice

Mild traumatic brain injury (mTBI) induced by low-intensity blast (LIB) is a serious health problem affecting military service members and veterans. Our previous reports using a single open-field LIB mouse model showed the absence of gross microscopic damage or necrosis in the brain, while transmission electron microscopy (TEM) identified ultrastructural abnormalities of myelin sheaths, mitochondria, and synapses. The neurovascular unit (NVU), an anatomical and functional system with multiple components, is vital for the regulation of cerebral blood flow and cellular interactions. In this study, we delineated ultrastructural abnormalities affecting the NVU in mice with LIB exposure quantitatively and qualitatively. Luminal constrictive irregularities were identified at 7 days post-injury (DPI) followed by dilation at 30 DPI along with degeneration of pericytes. Quantitative proteomic analysis identified significantly altered vasomotor-related proteins at 24 h post-injury. Endothelial cell, basement membrane and astrocyte end-foot swellings, as well as vacuole formations, occurred in LIB-exposed mice, indicating cellular edema. Structural abnormalities of tight junctions and astrocyte end-foot detachment from basement membranes were also noted. These ultrastructural findings demonstrate that LIB induces multiple-component NVU damage. Prevention of NVU damage may aid in identifying therapeutic targets to mitigate the effects of primary brain blast injury.

Cellular and molecular mechanisms in vascular repair after traumatic brain injury: a narrative review

Traumatic brain injury (TBI) disrupts normal brain function and is associated with high morbidity and fatality rates. TBI is characterized as mild, moderate or severe depending on its severity. The damage may be transient and limited to the dura matter, with only subtle changes in cerebral parenchyma, or life-threatening with obvious focal contusions, hematomas and edema. Blood vessels are often injured in TBI. Even in mild TBI, dysfunctional cerebral vascular repair may result in prolonged symptoms and poor outcomes. Various distinct types of cells participate in vascular repair after TBI. A better understanding of the cellular response and function in vascular repair can facilitate the development of new therapeutic strategies. In this review, we analyzed the mechanism of cerebrovascular impairment and the repercussions following various forms of TBI. We then discussed the role of distinct cell types in the repair of meningeal and parenchyma vasculature following TBI, including endothelial cells, endothelial progenitor cells, pericytes, glial cells (astrocytes and microglia), neurons, myeloid cells (macrophages and monocytes) and meningeal lymphatic endothelial cells. Finally, possible treatment techniques targeting these unique cell types for vascular repair after TBI are discussed.

Effects of repeated sleep deprivation on brain pericytes in mice

The damaging effects of sleep deprivation (SD) on brain parenchyma have been extensively studied. However, the specific influence of SD on brain pericytes, a primary component of the blood-brain barrier (BBB) and the neurovascular unit (NVU), is still unclear. The present study examined how acute or repeated SD impairs brain pericytes by measuring the cerebrospinal fluid (CSF) levels of soluble platelet-derived growth factor receptor beta (sPDGFRβ) and quantifying pericyte density in the cortex, hippocampus, and subcortical area of the PDGFRβ-P2A-CreERT2/tdTomato mice, which predominantly express the reporter tdTomato in vascular pericytes. Our results showed that a one-time 4 h SD did not significantly change the CSF sPDGFRβ level. In contrast, repeated SD (4 h/day for 10 consecutive days) significantly elevated the CSF sPDGFRβ level, implying explicit pericyte damages due to repeated SD. Furthermore, repeated SD significantly decreased the pericyte densities in the cortex and hippocampus, though the pericyte apoptosis status remained unchanged as measured with Annexin V-affinity assay and active Caspase-3 staining. These results suggest that repeated SD causes brain pericyte damage and loss via non-apoptosis pathways. These changes to pericytes may contribute to SD-induced BBB and NVU dysfunctions. The reversibility of this process implies that sleep improvement may have a protective effect on brain pericytes.

Anti-inflammatory interleukin 1 receptor antagonist concentration in plasma correlates with blood-brain barrier integrity in the primary lesion area in traumatic brain injury patients

Purpose

Blood-brain barrier (BBB) dysregulation and pro-inflammatory signalling molecules are secondary factors that have been associated with injury severity and long-term clinical outcome following traumatic brain injury (TBI). However, the association between BBB permeability and inflammation is unknown in human TBI patients. In this study, we investigated whether BBI integrity as measured by Dynamic Contrast-Enhanced (DCE) Magnetic Resonance Imaging (MRI) correlates with plasma levels of immunological markers following TBI.

Methods

Thirty-two TBI patients recruited from a neurosurgical unit were included in the study. Structural three-dimensional T1-weighted and DCE-MRI images were acquired on a 3T MRI at the earliest opportunity once the participant was sufficiently stable after patient admission to hospital. Blood sampling was performed on the same day as the MRI. The location and extents of the haemorrhagic and contusional lesions were identified. Immunological biomarkers were quantified from the participants' plasma using a multiplex immunoassay. Demographic and clinical information, including age and Glasgow Coma Scale (GCS) were also collected and the immunological biomarker profiles were compared across controls and the TBI severity sub-groups. Contrast agent leakiness through blood-brain barriers (BBB) in the contusional lesions were assessed by fitting DCE-MRI using Patlak model and BBB leakiness characteristics of the participants were correlated with the immunological biomarker profiles.

Results

TBI patients showed reduced plasma levels of interleukin (IL)-1β, IFN-γ, IL-13, and chemokine (C-C motif) ligands (CCL)2 compared to controls and significantly higher levels of platelet-derived growth factor (PDGF-BB), IL-6, and IL-8. BBB leakiness of the contusional lesions did not significantly differ across different TBI severity sub-groups. IL-1ra levels significantly and positively correlated with the contusional lesion's BBB integrity as measured with DCE-MRI via an exponential curve relationship.

Discussion

This is the first study to combine DCE-MRI with plasma markers of inflammation in acute TBI patients. Our finding that plasma levels of the anti-inflammatory cytokine IL-1ra correlated negatively with increased leakiness of the BBB.

Pericyte Loss in Diseases

Pericytes are specialized cells located in close proximity to endothelial cells within the microvasculature. They play a crucial role in regulating blood flow, stabilizing vessel walls, and maintaining the integrity of the blood-brain barrier. The loss of pericytes has been associated with the development and progression of various diseases, such as diabetes, Alzheimer's disease, sepsis, stroke, and traumatic brain injury. This review examines the detection of pericyte loss in different diseases, explores the methods employed to assess pericyte coverage, and elucidates the potential mechanisms contributing to pericyte loss in these pathological conditions. Additionally, current therapeutic strategies targeting pericytes are discussed, along with potential future interventions aimed at preserving pericyte function and promoting disease mitigation.

Three dimensional evaluation of cerebrovascular density and branching in chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to repetitive head impacts (RHI) and characterized by perivascular accumulations of hyperphosphorylated tau protein (p-tau) at the depths of the cortical sulci. Studies of living athletes exposed to RHI, including concussive and nonconcussive impacts, have shown increased blood-brain barrier permeability, reduced cerebral blood flow, and alterations in vasoreactivity. Blood-brain barrier abnormalities have also been reported in individuals neuropathologically diagnosed with CTE. To further investigate the three-dimensional microvascular changes in individuals diagnosed with CTE and controls, we used SHIELD tissue processing and passive delipidation to optically clear and label blocks of postmortem human dorsolateral frontal cortex. We used fluorescent confocal microscopy to quantitate vascular branch density and fraction volume. We compared the findings in 41 male brain donors, age at death 31-89 years, mean age 64 years, including 12 donors with low CTE (McKee stage I-II), 13 with high CTE (McKee stage III-IV) to 16 age- and sex-matched non-CTE controls (7 with RHI exposure and 9 with no RHI exposure). The density of vessel branches in the gray matter sulcus was significantly greater in CTE cases than in controls. The ratios of sulcus versus gyrus vessel branch density and fraction volume were also greater in CTE than in controls and significantly above one for the CTE group. Hyperphosphorylated tau pathology density correlated with gray matter sulcus fraction volume. These findings point towards increased vascular coverage and branching in the dorsolateral frontal cortex (DLF) sulci in CTE, that correlates with p-tau pathology.

Choroidal circulation disturbance is an initial factor in outer retinal degeneration in rats under simulated weightlessness

Objective: Microgravity contributes to ocular injury yet the underlying mechanism remains unclear. This study aims to elucidate the mechanism behind choroidal circulation disorder and outer retinal degeneration in rats with simulated weightlessness. Methods: Optical coherence tomography angiography (OCTA) was used to evaluate choroidal circulation and retinal morphological alterations in rats with weightlessness simulation. Electroretinogram and transmission electron microscopy were used to examine the ultrastructure and function of the choroid and outer retina. Furthermore, histological and terminal deoxynucleotidyl transferase deoxyuridine dUTP nick-end labeling (TUNEL) staining was used to monitor retinal morphology. Western blotting was performed to analyze the expressions of blood-retinal outer barrier function-related proteins (Cx43, ZO-1, and occludin). Results: The choroidal thickening was observed from the fourth week of simulated weightlessness (p < 0.05), and choroidal capillary density started to decline by the fifth week (p < 0.05). Transmission electron microscopy revealed that the choroidal vessels were open and operating well by the fourth week. However, most of the mitochondria within the vascular endothelium underwent mild swelling, and by the fifth week, the choroidal vessels had various degrees of erythrocyte aggregation, mitochondrial swelling, and apoptosis. Additionally, ERG demonstrated a decline in retinal function beginning in the fifth week (p < 0.05). TUNEL staining revealed a significantly higher apoptotic index in the outer nuclear layer of the retina (p < 0.05). At the sixth week weeks of simulated weightlessness, OCTA and hematoxylin and eosin (HE) staining of retinal sections revealed that the outer nuclear layer of the retina started to become thin (p < 0.05). Results from western blotting revealed that Cx43, ZO-1, and occludin exhibited decreased expression (p < 0.05). Conclusion: Based on our findings in a rat model of simulated weightlessness, choroidal circulation disturbance induced by choroidal congestion is the initial cause of outer retinal degeneration. Blood-retinal barrier disruption is significant in this process.

Discovery of novel microRNAs and their pathogenic responsive target genes in mild traumatic brain injury

MicroRNAs (miRNAs) are non-coding RNA molecules that function in RNA silencing and post-transcriptional regulation of gene expression. They are profound mediators of molecular and cellular changes in several pathophysiological conditions. Since miRNAs play major roles in regulating gene expression after traumatic brain injury (TBI), their possible role in diagnosis, prognosis, and therapy is not much explored. In this study, we aimed to identify specific miRNAs that are involved in the pathophysiological conditions in the first 24 h after mild TBI (mTBI). The genome-wide expression of miRNAs was evaluated by applying RNA sequence in the injury area of the cerebral cortex 24 after inflicting the injury using a mouse model of mild fluid percussion injury (FPI; 10 psi). Here, we identified different annotated, conserved, and novel miRNAs. A total of 978 miRNAs after 24 h of TBI were identified, and among these, 906 miRNAs were differentially expressed between control and mTBI groups. In this study, 146 miRNAs were identified as novel to mTBI and among them, 21 miRNAs were significant (p < 0.05). Using q-RT-PCR, we validated 10 differentially and significantly expressed novel miRNAs. Further, we filtered the differentially expressed miRNAs that were linked with proinflammatory cytokines, apoptosis, matrix metalloproteinases (MMPs), and tight junction and junctional adhesion molecule genes. Overall, this work shows that mTBI induces widespread changes in the expression of miRNAs that may underlie the progression of the TBI pathophysiology. The detection of several novel TBI-responsive miRNAs and their solid link with pathophysiological genes may help in identifying novel therapeutic targets.

Neuroprotective Effects of Delayed TGF-β1 Receptor Antagonist Administration on Perinatal Hypoxic-Ischemic Brain Injury

Hypoxic-ischemic (HI) brain injury in neonatal encephalopathy triggers a wave of neuroinflammatory events attributed to causing the progressive degeneration and functional deficits seen weeks after the primary damage. The cellular processes mediating this prolonged neurodegeneration in HI injury are not sufficiently understood. Consequently, current therapies are not fully protective. In a recent study, we found significant improvements in neurologic outcomes when a small molecule antagonist for activin-like kinase 5 (ALK5), a transforming growth factor beta (TGF-β) receptor was used as a therapeutic in a rat model of moderate term HI. Here, we have extended those studies to a mouse preterm pup model of HI. For these studies, postnatal day 7 CD1 mice of both sexes were exposed to 35-40 min of HI. Beginning 3 days later, SB505124, the ALK5 receptor antagonist, was administered systemically through intraperitoneal injections performed every 12 h for 5 days. When evaluated 23 days later, SB505124-treated mice had ∼2.5-fold more hippocampal area and ∼2-fold more thalamic tissue. Approximately 90% of the ipsilateral hemisphere (ILH) was preserved in the SB505124-treated HI mice compared to the vehicle-treated HI mice, where the ILH was ∼60% of its normal size. SB505124 also preserved the subcortical white matter. SB505124 treatment preserved levels of aquaporin-4 and n-cadherin, key proteins associated with blood-brain barrier function. Importantly, SB505124 administration improved sensorimotor function as assessed by a battery of behavioral tests. Altogether, these data lend additional support to the conclusion that SB505124 is a candidate neuroprotective molecule that could be an effective treatment for HI-related encephalopathy in moderately injured preterm infants.

Immune regulation in neurovascular units after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Survivors may experience movement disorders, memory loss, and cognitive deficits. However, there is a lack of understanding of the pathophysiology of TBI-mediated neuroinflammation and neurodegeneration. The immune regulation process of TBI involves changes in the peripheral and central nervous system (CNS) immunity, and intracranial blood vessels are essential communication centers. The neurovascular unit (NVU) is responsible for coupling blood flow with brain activity, and comprises endothelial cells, pericytes, astrocyte end-feet, and vast regulatory nerve terminals. A stable NVU is the basis for normal brain function. The concept of the NVU emphasizes that cell-cell interactions between different types of cells are essential for maintaining brain homeostasis. Previous studies have explored the effects of immune system changes after TBI. The NVU can help us further understand the immune regulation process. Herein, we enumerate the paradoxes of primary immune activation and chronic immunosuppression. We describe the changes in immune cells, cytokines/chemokines, and neuroinflammation after TBI. The post-immunomodulatory changes in NVU components are discussed, and research exploring immune changes in the NVU pattern is also described. Finally, we summarize immune regulation therapies and drugs after TBI. Therapies and drugs that focus on immune regulation have shown great potential for neuroprotection. These findings will help us further understand the pathological processes after TBI.

Mild Traumatic Brain Injury Induces Time- and Sex-Dependent Cerebrovascular Dysfunction and Stroke Vulnerability

Mild traumatic brain injury (mTBI) produces subtle cerebrovascular impairments that persist over time and promote increased ischemic stroke vulnerability. We recently established a role for vascular impairments in exacerbating stroke outcomes 1 week after TBI, but there is a lack of research regarding long-term impacts of mTBI-induced vascular dysfunction, as well as a significant need to understand how mTBI promotes stroke vulnerability in both males and females. Here, we present data using a mild closed head TBI model and an experimental stroke occurring either 7 or 28 days later in both male and female mice. We report that mTBI induces larger stroke volumes 7 days after injury, however, this increased vulnerability to stroke persists out to 28 days in female but not male mice. Importantly, mTBI-induced changes in blood-brain barrier permeability, intravascular coagulation, angiogenic factors, total vascular area, and glial expression were differentially altered across time and by sex. Taken together, these data suggest that mTBI can result in persistent cerebrovascular dysfunction and increased susceptibility to worsened ischemic outcomes, although these dysfunctions occur differently in male and female mice.

Myelin Debris Impairs Tight Junctions and Promotes the Migration of Microvascular Endothelial Cells in the Injured Spinal Cord

Clearance of myelin debris caused by acute demyelination is an essential process for functional restoration following spinal cord injury (SCI). Microvascular endothelial cells, acting as "amateur" phagocytes, have been confirmed to engulf and degrade myelin debris, promoting the inflammatory response, robust angiogenesis, and persistent fibrosis. However, the effect of myelin debris engulfment on the function of endothelial tight junctions (TJs) remains unclear. Here, we demonstrate that myelin debris uptake impairs TJs and gap junctions of endothelial cells in the lesion core of the injured spinal cord and in vitro, resulting in increased permeability and leakage. We further show that myelin debris acts as an inducer to regulate the endothelial-to-mesenchymal transition in a dose-dependent manner and promotes endothelial cell migration through the PI3K/AKT and ERK signaling pathways. Together, our results indicate that myelin debris engulfment impairs TJs and promotes the migration of endothelial cells. Accelerating myelin debris clearance may help maintain blood-spinal cord barrier integrity, thus facilitating restoration of motor and sensory function following SCI.

Mfsd2a attenuated hypoxic-ischemic brain damage via protection of the blood-brain barrier in mfat-1 transgenic mice

Previous studies have shown that mfat-1 transgenic mice have protective effects against some central nervous system (CNS) disorders, owing to the high docosahexaenoic acid (DHA) content enriched in their brains. However, whether this protective effect is connected to the blood-brain barrier (BBB) remains unclear. This study aims to investigate the mechanisms of the protective effect against hypoxic-ischemic brain damage (HIBD) of mfat-1 transgenic mice. mfat-1 mice not only demonstrated a significant amelioration of neurological dysfunction and neuronal damage but also partly maintained the physiological permeability of the BBB after HIBD. We initially showed this was associated with elevated major facilitator superfamily domain-containing 2a (Mfsd2a) expression on the BBB, resulting from more lysophosphatidylcholine (LPC)-DHA entering the brain. Wild-type (WT) mice showed a similar Mfsd2a expression trend after long-term feeding with an LPC-DHA-rich diet. Knockdown of Mfsd2a by siRNA intra-cerebroventricular (ICV) injection neutralized the protective effect against HIBD-induced BBB disruption in mfat-1 mice, further validating the protective function of Mfsd2a on BBB. HIBD-induced BBB high permeability was attenuated by Mfsd2a, primarily through a transcellular pathway to decrease caveolae-like vesicle-mediated transcytosis. Taken together, these findings not only reveal that mfat-1 transgenic mice have higher expression of Mfsd2a on the BBB, which partly sustains BBB permeability via vesicular transcytosis to alleviate the severity of HIBD, but also suggest that dietary intake of LPC-DHA may upregulate Mfsd2a expression as a novel therapeutic strategy for BBB dysfunction and survival in HIBD patients.

Connexin 43: An Interface Connecting Neuroinflammation to Depression

Major depressive disorder (MDD) is a leading chronic mental illness worldwide, characterized by anhedonia, pessimism and even suicidal thoughts. Connexin 43 (Cx43), mainly distributed in astrocytes of the brain, is by far the most widely and ubiquitously expressed connexin in almost all vital organs. Cx43 forms gap junction channels in the brain, which mediate energy exchange and effectively maintain physiological homeostasis. Increasing evidence suggests the crucial role of Cx43 in the pathogenesis of MDD. Neuroinflammation is one of the most common pathological features of the central nervous system dysfunctions. Inflammatory factors are abnormally elevated in patients with depression and are closely related to nearly all links of depression. After activating the inflammatory pathway in the brain, the release and uptake of glutamate and adenosine triphosphate, through Cx43 in the synaptic cleft, would be affected. In this review, we have summarized the association between Cx43 and neuroinflammation, the cornerstones linking inflammation and depression, and Cx43 abnormalities in depression. We also discuss the significant association of Cx43 in inflammation and depression, which will help to explore new antidepressant drug targets.

Systemic Cell Adhesion Molecules in Severe Mental Illness: Potential Role of Intercellular CAM-1 in Linking Peripheral and Neuroinflammation

BACKGROUND

Cell adhesion molecules (CAMs) orchestrate leukocyte trafficking and could link peripheral and neuroinflammation in patients with severe mental illness (SMI), by promoting inflammatory and immune-mediated responses and mediating signals across blood-brain barrier. We hypothesized that CAMs would be dysregulated in SMI and evaluated plasma levels of different vascular and neural CAMs. Dysregulated CAMs in plasma were further evaluated in vivo in leukocytes and brain tissue and in vitro in induced pluripotent stem cells.

METHODS

We compared plasma soluble levels of different vascular (VCAM-1, ICAM-1, P-SEL) and neural (JAM-A, NCAD) CAMs in circulating leukocytes in a large SMI sample of schizophrenia (SCZ) spectrum disorder (n = 895) and affective disorder (n = 737) and healthy control participants (n = 1070) controlling for age, sex, body mass index, C-reactive protein, and freezer storage time. We also evaluated messenger RNA expression of ICAM1 and related genes encoding ICAM-1 receptors in leukocytes using microarray (n = 842) and in available RNA sequencing data from the CommonMind Consortium (CMC) in postmortem samples from the dorsolateral prefrontal cortex (n = 474). The regulation of soluble ICAM-1 in induced pluripotent stem cell-derived neurons and astrocytes was assessed in patients with SCZ and healthy control participants (n = 8 of each).

RESULTS

Our major findings were 1) increased soluble ICAM-1 in patients with SMI compared with healthy control participants; 2) increased ITGB2 messenger RNA, encoding the beta chain of the ICAM-1 receptor, in circulating leukocytes from patients with SMI and increased prefrontal cortex messenger RNA expression of ICAM1 in SCZ; and 3) enhanced soluble ICAM-1 release in induced pluripotent stem cell-derived neurons from patients with SCZ.

CONCLUSIONS

Our results support a systemic and cerebral dysregulation of soluble ICAM-1 expression in SMI and especially in patients with SCZ.