Extracellular matrix and matrix receptors in blood-brain barrier formation and stroke

Beyond wrecking a wall: revisiting the concept of blood-brain barrier breakdown in ischemic stroke

The blood-brain barrier constitutes a dynamic and interactive boundary separating the central nervous system and the peripheral circulation. It tightly modulates the ion transport and nutrient influx, while restricting the entry of harmful factors, and selectively limiting the migration of immune cells, thereby maintaining brain homeostasis. Despite the well-established association between blood-brain barrier disruption and most neurodegenerative/neuroinflammatory diseases, much remains unknown about the factors influencing its physiology and the mechanisms underlying its breakdown. Moreover, the role of blood-brain barrier breakdown in the translational failure underlying therapies for brain disorders is just starting to be understood. This review aims to revisit this concept of "blood-brain barrier breakdown," delving into the most controversial aspects, prevalent challenges, and knowledge gaps concerning the lack of blood-brain barrier integrity. By moving beyond the oversimplistic dichotomy of an "open"/"bad" or a "closed"/"good" barrier, our objective is to provide a more comprehensive insight into blood-brain barrier dynamics, to identify novel targets and/or therapeutic approaches aimed at mitigating blood-brain barrier dysfunction. Furthermore, in this review, we advocate for considering the diverse time- and location-dependent alterations in the blood-brain barrier, which go beyond tight-junction disruption or brain endothelial cell breakdown, illustrated through the dynamics of ischemic stroke as a case study. Through this exploration, we seek to underscore the complexity of blood-brain barrier dysfunction and its implications for the pathogenesis and therapy of brain diseases.

Effect of metabolic disorders on reactive gliosis and glial scarring at the early subacute phase of stroke in a mouse model of diabetes and obesity

It is well recognized that type II Diabetes (T2D) and overweight/obesity are established risk factors for stroke, worsening also their consequences. However, the underlying mechanisms by which these disorders aggravate outcomes are not yet clear limiting the therapeutic opportunities. To fill this gap, we characterized, for the first time, the effects of T2D and obesity on the brain repair mechanisms occurring 7 days after stroke, notably glial scarring. In the present study, by performing a 30-minute middle cerebral artery occlusion (MCAO) on db/db (obese diabetics mice) and db/+ (controls) mice, we demonstrated that obese and diabetic mice displayed larger lesions (i.e. increased infarct volume, ischemic core, apoptotic cell number) and worsened neurological outcomes compared to their control littermates. We then investigated the formation of the glial scar in control and db/db mice 7 days post-stroke. Our observations argue in favor of a stronger and more persistent activation of astrocytes and microglia in db/db mice. Furthermore, an increased deposition of extracellular matrix (ECM) was observed in db/db vs control mice (i.e. chondroitin sulfate proteoglycan and collagen type IV). Consequently, we demonstrated for the first time that the db/db status is associated with increased astrocytic and microglial activation 7 days after stroke and resulted in higher deposition of ECM within the damaged area. Interestingly, the injury-induced neurogenesis appeared stronger in db/db as shown by the labeling of migrating neuroblast. This increase appeared correlated to the larger size of lesion. It nevertheless raises the question of the functional integration of the new neurons in db/db mice given the observed dense ECM, known to be repulsive for neuronal migration. Carefully limiting glial scar formation after stroke represents a promising area of research for reducing neuronal loss and limiting disability in diabetic/obese patients.

Suspected Mitochondrial Dysfunction and Complex Pathophysiology in Fatal Hypermobile Ehlers-Danlos Syndrome: Insights from a Case Report and Post-Mortem Findings

Background/Objectives: Hypermobile Ehlers-Danlos Syndrome (hEDS) is a complex connective tissue disorder with multi-systemic manifestations that significantly impact quality of life. This case report investigates the clinical course and molecular mechanisms of advanced hEDS through an in-depth case study and post-mortem findings. Methods: The clinical history of a 24-year-old patient with advanced hEDS was analyzed, focusing on progressive complications across multiple systems. Post-mortem examination and genetic analysis were performed to elucidate the underlying pathophysiology. Results: The patient's clinical course was marked by gastrointestinal, neurological, and immune complications requiring numerous surgical interventions. Post-mortem findings revealed severe gastrointestinal dysmotility and Alzheimer's Type II astrocytes. Genetic analysis identified variants in mtDNA genes ATP6, CYB, and ND, suggesting a potential role of impaired mitochondrial function in hEDS pathogenesis but requiring further validation through functional studies. Conclusions: This case report provides valuable insights into the potential role of mitochondrial dysfunction in advanced hEDS and highlights the need for further research in this area. Future studies should include comprehensive functional assays, longitudinal tissue sampling, family genetic analyses, and muscle biopsies to better understand the complex interplay between genetic factors, mitochondrial function, and clinical manifestations in hEDS. Establishing genetic bases and developing targeted therapies addressing both structural and metabolic aspects are crucial. The patient's legacy offers invaluable information that could significantly contribute to enhancing diagnostic accuracy and developing personalized treatment strategies for this challenging disorder, potentially leading to better care for individuals living with hEDS.

Activation of the Coagulation Cascade as a Universal Danger Sign

Hemostasis is a mechanism that stops bleeding from an injured vessel, involves multiple interlinked steps, culminating in the formation of a "clot" sealing the damaged area. Moreover, it has long been recognized that inflammation also provokes the activation of the coagulation system. However, there has been an increasing amount of evidence revealing the immune function of the hemostasis system. This review collects and analyzes the results of the experimental studies and data from clinical observations confirming the inflammatory function of hemostasis. Here, we summarize the latest knowledge of the pathways in immune system activation under the influence of coagulation factors. The data analyzed allow us to consider the components of hemostasis as receptors recognizing «foreign» or damaged «self» or/and as «self» damage signals that initiate and reinforce inflammation and affect the direction of the adaptive immune response. To sum up, the findings collected in the review allow us to classify the coagulation factors, such as Damage-Associated Molecular Patterns that break down the conventional concepts of the coagulation system.

Plasma levels of matrix metalloproteinases in early psychosis, anxiety and depression: Evidence from the ALSPAC cohort

BACKGROUND

Converging evidence supports the role of Matrix Metalloproteinases (MMPs) in psychiatric disorders. Originally identified as regulators of the extracellular matrix (ECM), MMPs' functions span multiple processes, including inflammation, synaptic plasticity, neuronal migration, and blood-brain barrier maintenance. Tissue Inhibitors of Metalloproteinases (TIMPs) are major regulators of MMPs. In the present study we examined the associations of plasma MMPs and TIMPs with mental disorders in young adults aged 24 years in the Avon Longitudinal Study of Parents and Children (ALSPAC).

METHODS

The present study was a nested case control study within the Avon Longitudinal Study of Parents and Children and comprised 374 participants who met criteria for psychiatric disorders (35 met the criteria for psychotic disorder, 201 for mild/moderate depressive disorder, and 266 for generalised anxiety disorder) and 401 controls. All cases and controls had were selected from the group of 4019 participants who had attended at age 24 years, completed psychiatric assessments and provided plasma samples. Plasma concentrations of MMP2, MMP3, MMP9 and TIMP-4 were quantified using proximity extension assays available on Olink® Cardiovascular Panel III. Logistic regression analysis compared standardised MMPs and TIMPs levels in cases and controls. Models were adjusted for sex, body mass index, and cigarette smoking.

RESULTS

There was evidence for an association between MMP3 and depressive disorder (Odds ratio [OR] 1.35, 95 % confidence interval [CI] 1.06-1.73). There was evidence for an association between TIMP4 and depressive disorder (OR 1.51, 95 % CI 1.22-1.88) and generalised anxiety disorder (OR 1.43, 95 % CI 1.19-1.72). There was no evidence for an association between MMPs and psychotic disorders.

CONCLUSIONS

The study revealed that 24-year-olds with depressive and anxiety disorders exhibited elevated plasma concentrations of TIMP-4 compared to controls. There was evidence for an association between MMP3 and depressive disorder. These findings provide further support for the involvement of metalloproteinases as biomarkers in the pathophysiology of mental disorders during early adulthood.

3D Neurovascular Unit Tissue Model to Assess Responses to Traumatic Brain Injury

The neurovascular unit (NVU) is a critical interface in the central nervous system that links vascular interactions with glial and neural tissue. Disruption of the NVU has been linked to the onset and progression of neurodegenerative diseases. Despite its significance the NVU remains challenging to study in a physiologically relevant manner. Here, a 3D cell triculture model of the NVU is developed that incorporates human primary brain microvascular endothelial cells, astrocytes, and pericytes into a tissue system that can be sustained in vitro for several weeks. This tissue model helps recapitulate the complexity of the NVU and can be used to interrogate the mechanisms of disease and cell-cell interactions. The NVU tissue model displays elevated cell death and inflammatory responses following mechanical damage, to emulate traumatic brain injury (TBI) under controlled laboratory conditions, including lactate dehydrogenase (LDH) release, elevated inflammatory markers TNF-α and monocyte chemoattractant cytokines MCP-2 and MCP-3 and reduced expression of the tight junction marker ZO-1. This 3D tissue model serves as a tool for deciphering mechanisms of TBIs and immune responses associated with the NVU.

A Wonderful Journey: The Diverse Roles of Adenosine Deaminase Action on RNA 1 (ADAR1) in Central Nervous System Diseases

BACKGROUND

Adenosine deaminase action on RNA 1 (ADAR1) can convert the adenosine in double-stranded RNA (dsRNA) molecules into inosine in a process known as A-to-I RNA editing. ADAR1 regulates gene expression output by interacting with RNA and other proteins; plays important roles in development, including growth; and is linked to innate immunity, tumors, and central nervous system (CNS) diseases.

RESULTS

In recent years, the role of ADAR1 in tumors has been widely discussed, but its role in CNS diseases has not been reviewed. It is worth noting that recent studies have shown ADAR1 has great potential in the treatment of neurodegenerative diseases, but the mechanisms are still unclear. Therefore, it is necessary to elaborate on the role of ADAR1 in CNS diseases.

CONCLUSIONS

Here, we focus on the effects and mechanisms of ADAR1 on CNS diseases such as Aicardi-AicardiGoutières syndrome, Alzheimer's disease, Parkinson's disease, glioblastoma, epilepsy, amyotrophic lateral sclerosis, and autism. We also evaluate the impact of ADAR1-based treatment strategies on these diseases, with a particular focus on the development and treatment strategies of new technologies such as microRNAs, nanotechnology, gene editing, and stem cell therapy. We hope to provide new directions and insights for the future development of ADAR1 gene editing technology in brain science and the treatment of CNS diseases.

Basement membranes' role in immune cell recruitment to the central nervous system

Basement membranes form part of the extracellular matrix (ECM), which is the structural basis for all tissue. Basement membranes are cell-adherent sheets found between cells and vascular endothelia, including those of the central nervous system (CNS). There is exceptional regional specialisation of these structures, both in tissue organisation and regulation of tissue-specific cellular processes. Due to their location, basement membranes perform a key role in immune cell trafficking and therefore are important in inflammatory processes causing or resulting from CNS disease and injury. This review will describe basement membranes in detail, with special focus on the brain. We will cover how genetic changes drive brain pathology, describe basement membranes' role in immune cell recruitment and how they respond to various brain diseases. Understanding how basement membranes form the junction between the immune and central nervous systems will be a major advance in understanding brain disease.

Drug Delivery Across the Blood-Brain Barrier: A New Strategy for the Treatment of Neurological Diseases

The blood-brain barrier (BBB) serves as a highly selective barrier between the blood and the central nervous system (CNS), and its main function is to protect the brain from foreign substances. This physiological property plays a crucial role in maintaining CNS homeostasis, but at the same time greatly limits the delivery of drug molecules to the CNS, thus posing a major challenge for the treatment of neurological diseases. Given that the high incidence and low cure rate of neurological diseases have become a global public health problem, the development of effective BBB penetration technologies is important for enhancing the efficiency of CNS drug delivery, reducing systemic toxicity, and improving the therapeutic outcomes of neurological diseases. This review describes the physiological and pathological properties of the BBB, as well as the current challenges of trans-BBB drug delivery, detailing the structural basis of the BBB and its role in CNS protection. Secondly, this paper reviews the drug delivery strategies for the BBB in recent years, including physical, biological and chemical approaches, as well as nanoparticle-based delivery technologies, and provides a comprehensive assessment of the effectiveness, advantages and limitations of these delivery strategies. It is hoped that the review in this paper will provide valuable references and inspiration for future researchers in therapeutic studies of neurological diseases.

Tension at the gate: sensing mechanical forces at the blood-brain barrier in health and disease

Microvascular brain endothelial cells tightly limit the entry of blood components and peripheral cells into the brain by forming the blood-brain barrier (BBB). The BBB is regulated by a cascade of mechanical and chemical signals including shear stress and elasticity of the adjacent endothelial basement membrane (BM). During physiological aging, but especially in neurological diseases including multiple sclerosis (MS), stroke, small vessel disease, and Alzheimer's disease (AD), the BBB is exposed to inflammation, rigidity changes of the BM, and disturbed cerebral blood flow (CBF). These altered forces lead to increased vascular permeability, reduced endothelial reactivity to vasoactive mediators, and promote leukocyte transmigration. Whereas the molecular players involved in leukocyte infiltration have been described in detail, the importance of mechanical signalling throughout this process has only recently been recognized. Here, we review relevant features of mechanical forces acting on the BBB under healthy and pathological conditions, as well as the endothelial mechanosensory elements detecting and responding to altered forces. We demonstrate the underlying complexity by focussing on the family of transient receptor potential (TRP) ion channels. A better understanding of these processes will provide insights into the pathogenesis of several neurological disorders and new potential leads for treatment.

Assessing Mild Traumatic Brain Injury-Associated Blood-Brain Barrier (BBB) Damage and Restoration Using Late-Phase Perfusion Analysis by 3D ASL MRI: Implications for Predicting Progressive Brain Injury in a Focused Review

Mild traumatic brain injury (mTBI) is a common occurrence around the world, associated with a variety of blunt force and torsion injuries affecting all age groups. Most never reach medical attention, and the identification of acute injury and later clearance to return to usual activities is relegated to clinical evaluation-particularly in sports injuries. Advanced structural imaging is rarely performed due to the usual absence of associated acute anatomic/hemorrhagic changes. This review targets physiologic imaging techniques available to identify subtle blood-brain barrier dysfunction and white matter tract shear injury and their association with chronic traumatic encephalopathy. These techniques provide needed objective measures to assure recovery from injury in those patients with persistent cognitive/emotional symptoms and in the face of repetitive mTBI.

Identification biomarkers in disease progression of obstructive sleep apnea from children serum based on WGCNA and Mfuzz

Obstructive sleep apnea (OSA) syndrome is a prevalent form of respiratory sleep disorder, with an increasing prevalence among children. The consequences of OSA include obesity, diabetes, cardiovascular disease, and neuropsychological diseases. Despite its pervasive impact, a significant proportion of individuals especially children remain unaware that they suffer from OSA. Consequently, there is an urgent need for an accessible diagnostic approach. In this study, we conducted a bioinformatic analysis to identify potential biomarkers from a proteomics dataset comprising serum samples from children with OSA in the progression stage. In the Gene Set Enrichment Analysis (GSEA), we observed that the complement and immune response pathways persisted throughout the development of OSA and could be detected in the early stages. Subsequent to soft clustering and WGCNA analysis, it was revealed that the Hippo pathway, including ITGAL and FERMT3, plays a role in mild OSA. The analysis revealed a significant alteration of the complement and coagulation pathways, including TFPI and MLB2, in moderate OSA. In severe OSA, there was an association between hypoxia and the extracellular matrix (ECM) receptor interaction and collagen binding. In summary, it can be posited that the systemic inflammation may persist throughout the progression of OSA. Furthermore, severe OSA is characterized by abnormal vascular endothelial function, which may be attributed to chronic hypoxia. Finally, four potential biomarkers (ITGAL, TFPI, TTR, ANTXR1) were identified based on LASSO regression, and a prediction model for OSA progression was constructed based on the biomarkers.

Meta-analysis of the make-up and properties of in vitro models of the healthy and diseased blood-brain barrier

In vitro models of the human blood-brain barrier (BBB) are increasingly used to develop therapeutics that can cross the BBB for treating diseases of the central nervous system. Here we report a meta-analysis of the make-up and properties of transwell and microfluidic models of the healthy BBB and of BBBs in glioblastoma, Alzheimer's disease, Parkinson's disease and inflammatory diseases. We found that the type of model, the culture method (static or dynamic), the cell types and cell ratios, and the biomaterials employed as extracellular matrix are all crucial to recapitulate the low permeability and high expression of tight-junction proteins of the BBB, and to obtain high trans-endothelial electrical resistance. Specifically, for models of the healthy BBB, the inclusion of endothelial cells and pericytes as well as physiological shear stresses (~10-20 dyne cm-2) are necessary, and when astrocytes are added, astrocytes or pericytes should outnumber endothelial cells. We expect this meta-analysis to facilitate the design of increasingly physiological models of the BBB.

Engineering a 3D Biomimetic Peptides Functionalized-Polyethylene Glycol Hydrogel Model Cocultured with Endothelial Cells and Astrocytes: Enhancing In Vitro Blood-Brain Barrier Biomimicry

The blood-brain barrier (BBB) poses a significant challenge for drug delivery and is linked to various neurovascular disorders. In vitro BBB models provide a tool to investigate drug permeation across the BBB and the barrier's response to external injury events. Yet, existing models lack fidelity in replicating the BBB's complexity, hindering a comprehensive understanding of its functions. This study introduces a three-dimensional (3D) model using polyethylene glycol (PEG) hydrogels modified with biomimetic peptides that represent recognition sequences of key proteins in the brain. Hydrogels were functionalized with recognition sequences for laminin (IKVAV) and fibronectin peptides (RGD) and chemically cross-linked with matrix metalloprotease-sensitive peptides (MMPs) to mimic the extracellular matrix of the BBB. Astrocytes and endothelial cells were seeded within and on the surface of the hydrogels, respectively. The barrier integrity was assessed through different tests including transendothelial electrical resistance (TEER), the permeability of sodium fluorescence (Na-F), the permeability of Evan's blue bound to albumin (EBA), and the expression of zonula occluden-1 (ZO-1) in seeded endothelial cells. Hydrogels with a combination of RGD and IKVAV peptides displayed superior performance, exhibiting significantly higher TEER values (55.33 ± 1.47 Ω·cm2) at day 5 compared to other 2D controls including HAECs-monoculture and HAECs-cocultured with NHAs seeded on well inserts and 3D controls including RGD hydrogel and RGD-IKVAV monoculture with HAECs and RGD hydrogel cocultured with HAECs and NHAs. The designed 3D system resulted in the lowest Evan's blue permeability at 120 min (0.215 ± 0.055 μg/mL) compared to controls. ZO-1 expression was significantly higher and formed a relatively larger network in the functionalized hydrogel cocultured with astrocytes and endothelial cells compared to the controls. Thus, the designed 3D model effectively recapitulates the main BBB structure and function in vitro and is expected to contribute to a deeper understanding of pathological CNS angiogenesis and the development of effective CNS medications.

Validation studies and multi-omics analysis of Zhx2 as a candidate quantitative trait gene underlying brain oxycodone metabolite (oxymorphone) levels and behavior

Sensitivity to the subjective reinforcing properties of opioids has a genetic component and can predict addiction liability of opioid compounds. We previously identified Zhx2 as a candidate gene underlying increased brain concentration of the oxycodone (OXY) metabolite oxymorphone (OMOR) in BALB/cJ (J) versus BALB/cByJ (By) females that could increase OXY state-dependent reward. A large structural intronic variant is associated with a robust reduction of Zhx2 expression in J mice, which we hypothesized enhances OMOR levels and OXY addiction-like behaviors. We tested this hypothesis by restoring the Zhx2 loss-of-function in Js (MVKO) and modeling the loss-of-function variant through knocking out the Zhx2 coding exon (E3KO) in Bys and assessing brain OXY metabolite levels and behavior. Consistent with our hypothesis, Zhx2 E3KO females showed an increase in brain OMOR levels and OXY-induced locomotor activity. However, contrary to our hypothesis, state-dependent expression of OXY-CPP was decreased in E3KO females and increased in E3KO males. We also overexpressed Zhx2 in the livers and brains of Js and observed Zhx2 overexpression in select brain regions that was associated with reduced OXY state-dependent learning. Integrative transcriptomic and proteomic analysis of E3KO mice identified astrocyte function, cell adhesion, extracellular matrix properties, and endothelial cell functions as pathways influencing brain OXY metabolite concentration and behavior. These results support Zhx2 as a quantitative trait gene underlying brain OMOR concentration that is associated with changes in OXY behavior and implicate potential quantitative trait mechanisms that together inform our overall understanding of Zhx2 in brain function.

Role of blood-brain barrier dysfunction in the development of poststroke epilepsy

Stroke is a major contributor to mortality and morbidity worldwide and the most common cause of epilepsy in the elderly in high income nations. In recent years, it has become increasingly evident that both ischemic and hemorrhagic strokes induce dysfunction of the blood-brain barrier (BBB), and that this impairment can contribute to epileptogenesis. Nevertheless, studies directly comparing BBB dysfunction and poststroke epilepsy (PSE) are largely absent. Therefore, this review summarizes the role of BBB dysfunction in the development of PSE in animal models and clinical studies. There are multiple mechanisms whereby stroke induces BBB dysfunction, including increased transcytosis, tight junction dysfunction, spreading depolarizations, astrocyte and pericyte loss, reactive astrocytosis, angiogenesis, matrix metalloproteinase activation, neuroinflammation, adenosine triphosphate depletion, oxidative stress, and finally cell death. The degree to which these effects occur is dependent on the severity of the ischemia, whereby cell death is a more prominent mechanism of BBB disruption in regions of critical ischemia. BBB dysfunction can contribute to epileptogenesis by increasing the risk of hemorrhagic transformation, increasing stroke size and the amount of cerebral vasogenic edema, extravasation of excitatory compounds, and increasing neuroinflammation. Furthermore, albumin extravasation after BBB dysfunction contributes to epileptogenesis primarily via increased transforming growth factor β signaling. Finally, seizures themselves induce BBB dysfunction, thereby contributing to epileptogenesis in a cyclical manner. In repairing this BBB dysfunction, pericyte migration via platelet-derived growth factor β signaling is indispensable and required for reconstruction of the BBB, whereby astrocytes also play a role. Although animal stroke models have their limitations, they provide valuable insights into the development of potential therapeutics designed to restore the BBB after stroke, with the ultimate goal of improving outcomes and minimizing the occurrence of PSE. In pursuit of this goal, rapamycin, statins, losartan, semaglutide, and metformin show promise, whereby modulation of pericyte migration could also be beneficial.

A dispensable role of mural cell-derived laminin-5 in intracerebral hemorrhage

Although most laminin isoforms are neuroprotective in stroke, mural cell-derived laminin-α5 plays a detrimental role in an ischemia-reperfusion model. To determine whether this deleterious effect is an intrinsic feature of mural cell-derived laminin-α5 or unique to ischemic stroke, we performed loss-of-function studies using middle-aged mice with laminin-α5 deficiency in mural cells (α5-PKO) in an intracerebral hemorrhage (ICH) model. Control and α5-PKO mice exhibited comparable changes in all parameters examined, including hematoma size, neuronal death, neurological function, blood-brain barrier integrity, and reactive gliosis. These findings highlight a minimal role of mural cell-derived laminin-α5 in ICH. Together with the detrimental role of mural cell-derived laminin-α5 in ischemic stroke, these negative results in ICH model suggest that mural cell-derived laminin-α5 may exert distinct functions in different diseases.

Monomeric and oligomeric amyloid-β cause distinct Alzheimer's disease pathophysiological characteristics in astrocytes in human glymphatics-on-chip models

Alzheimer's disease (AD) is marked by the aggregation of extracellular amyloid-β (Aβ) and astrocyte dysfunction. For Aβ oligomers or aggregates to be formed, there must be Aβ monomers present; however, the roles of monomeric Aβ (mAβ) and oligomeric Aβ (oAβ) in astrocyte pathogenesis are poorly understood. We cultured astrocytes in a brain-mimicking three-dimensional (3D) extracellular matrix and revealed that both mAβ and oAβ caused astrocytic atrophy and hyper-reactivity, but showed distinct Ca2+ changes in astrocytes. This 3D culture evolved into a microfluidic glymphatics-on-chip model containing astrocytes and endothelial cells with the interstitial fluid (ISF). The glymphatics-on-chip model not only reproduced the astrocytic atrophy, hyper-reactivity, and Ca2+ changes induced by mAβ and oAβ, but recapitulated that the components of the dystrophin-associated complex (DAC) and aquaporin-4 (AQP4) were properly maintained by the ISF, and dysregulated by mAβ and oAβ. Collectively, mAβ and oAβ cause distinct AD pathophysiological characteristics in the astrocytes.

Challenges and Future Perspectives in Modeling Neurodegenerative Diseases Using Organ-on-a-Chip Technology

Neurodegenerative diseases (NDDs) affect more than 50 million people worldwide, posing a significant global health challenge as well as a high socioeconomic burden. With aging constituting one of the main risk factors for some NDDs such as Alzheimer's disease (AD) and Parkinson's disease (PD), this societal toll is expected to rise considering the predicted increase in the aging population as well as the limited progress in the development of effective therapeutics. To address the high failure rates in clinical trials, legislative changes permitting the use of alternatives to traditional pre-clinical in vivo models are implemented. In this regard, microphysiological systems (MPS) such as organ-on-a-chip (OoC) platforms constitute a promising tool, due to their ability to mimic complex and human-specific tissue niches in vitro. This review summarizes the current progress in modeling NDDs using OoC technology and discusses five critical aspects still insufficiently addressed in OoC models to date. Taking these aspects into consideration in the future MPS will advance the modeling of NDDs in vitro and increase their translational value in the clinical setting.

Hypermobile Ehlers-Danlos syndrome and spontaneous CSF leaks: the connective tissue conundrum

Collagen, the most abundant protein in the body, is a key component of the extracellular matrix (ECM), which plays a crucial role in the structure and support of connective tissues. Abnormalities in collagen associated with connective tissue disorders (CTD) can lead to neuroinflammation and weaken the integrity of the blood-brain barrier (BBB), a semi-permeable membrane that separates the brain's extracellular fluid from the bloodstream. This compromise in the BBB can result from disruptions in ECM components, leading to neuroinflammatory responses, neuronal damage, and increased risks of neurological disorders. These changes impact central nervous system homeostasis and may exacerbate neurological conditions linked to CTD, manifesting as cognitive impairment, sensory disturbances, headaches, sleep issues, and psychiatric symptoms. The Ehlers-Danlos syndromes (EDS) are a group of heritable CTDs that result from varying defects in collagen and the ECM. The most prevalent subtype, hypermobile EDS (hEDS), involves clinical manifestations that include joint hypermobility, skin hyperextensibility, autonomic dysfunction, mast cell activation, chronic pain, as well as neurological manifestations like chronic headaches and cerebrospinal fluid (CSF) leaks. Understanding the connections between collagen, CSF, inflammation, and the BBB could provide insights into neurological diseases associated with connective tissue abnormalities and guide future research.

Cerebrospinal Fluid Proteome Map Reveals Molecular Signatures of Reversible Cerebral Vasoconstriction Syndrome

Reversible cerebral vasoconstriction syndrome (RCVS) is a complex neurovascular disorder characterized by repetitive thunderclap headaches and reversible cerebral vasoconstriction. The pathophysiological mechanism of this mysterious syndrome remains underexplored and there is no clinically available molecular biomarker. To provide insight into the pathogenesis of RCVS, this study reported the first landscape of dysregulated proteome of cerebrospinal fluid (CSF) in patients with RCVS (n  =  21) compared to the age- and sex-matched controls (n  =  20) using data-independent acquisition mass spectrometry. Protein-protein interaction and functional enrichment analysis were employed to construct functional protein networks using the RCVS proteome. An RCVS-CSF proteome library resource of 1054 proteins was established, which illuminated large groups of upregulated proteins enriched in the brain and blood-brain barrier (BBB). Personalized RCVS-CSF proteomic profiles from 17 RCVS patients and 20 controls reveal proteomic changes involving the complement system, adhesion molecules, and extracellular matrix, which may contribute to the disruption of BBB and dysregulation of neurovascular units. Moreover, an additional validation cohort validated a panel of biomarker candidates and a two-protein signature predicted by machine learning model to discriminate RCVS patients from controls with an area under the curve of 0.997. This study reveals the first RCVS proteome and a potential pathogenetic mechanism of BBB and neurovascular unit dysfunction. It also nominates potential biomarker candidates that are mechanistically plausible for RCVS, which may offer potential diagnostic and therapeutic opportunities beyond the clinical manifestations.

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.

Obesity-induced blood-brain barrier dysfunction: phenotypes and mechanisms

Obesity, a burgeoning global health issue, is increasingly recognized for its detrimental effects on the central nervous system, particularly concerning the integrity of the blood-brain barrier (BBB). This manuscript delves into the intricate relationship between obesity and BBB dysfunction, elucidating the underlying phenotypes and molecular mechanisms. We commence with an overview of the BBB's critical role in maintaining cerebral homeostasis and the pathological alterations induced by obesity. By employing a comprehensive literature review, we examine the structural and functional modifications of the BBB in the context of obesity, including increased permeability, altered transport mechanisms, and inflammatory responses. The manuscript highlights how obesity-induced systemic inflammation and metabolic dysregulation contribute to BBB disruption, thereby predisposing individuals to various neurological disorders. We further explore the potential pathways, such as oxidative stress and endothelial cell dysfunction, that mediate these changes. Our discussion culminates in the summary of current findings and the identification of knowledge gaps, paving the way for future research directions. This review underscores the significance of understanding BBB dysfunction in obesity, not only for its implications in neurodegenerative diseases but also for developing targeted therapeutic strategies to mitigate these effects.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

Occludin and collagen IV degradation mediated by the T9SS effector SspA contributes to blood-brain barrier damage in ducks during Riemerella anatipestifer infection

Riemerella anatipestifer infection is characterized by meningitis with neurological symptoms in ducklings and has adversely affected the poultry industry. R. anatipestifer strains can invade the duck brain to cause meningitis and neurological symptoms, but the underlying mechanism remains unknown. In this study, we showed that obvious clinical symptoms, an increase in blood‒brain barrier (BBB) permeability, and the accumulation of inflammatory cytokines occurred after intravenous infection with the Yb2 strain but not the mutant strain Yb2ΔsspA, indicating that Yb2 infection can lead to cerebrovascular dysfunction and that the type IX secretion system (T9SS) effector SspA plays a critical role in this pathological process. In addition, we showed that Yb2 infection led to rapid degradation of occludin (a tight junction protein) and collagen IV (a basement membrane protein), which contributed to endothelial barrier disruption. The interaction between SspA and occludin was confirmed by coimmunoprecipitation. Furthermore, we found that SspA was the main enzyme mediating occludin and collagen IV degradation. These data indicate that R. anatipestifer SspA mediates occludin and collagen IV degradation, which functions in BBB disruption in R. anatipestifer-infected ducks. These findings establish the molecular mechanisms by which R. anatipestifer targets duckling endothelial cell junctions and provide new perspectives for the treatment and prevention of R. anatipestifer infection.

Integrated transcriptomic and proteomic profiling reveals the key molecular signatures of brain endothelial reperfusion injury

BACKGROUND

Reperfusion therapy after ischemic stroke often causes brain microvascular injury. However, the underlying mechanisms are unclear.

METHODS

Transcriptomic and proteomic analyses were performed on human cerebral microvascular endothelial cells following oxygen-glucose deprivation (OGD) or OGD plus recovery (OGD/R) to identify molecules and signaling pathways dysregulated by reperfusion. Major findings were further validated in a mouse model of cerebral ischemia and reperfusion.

RESULTS

Transcriptomic analysis identified 390 differentially expressed genes (DEGs) between the OGD/R and OGD group. Pathway analysis indicated that these genes were mostly associated with inflammation, including the TNF signaling pathway, TGF-β signaling pathway, cytokine-cytokine receptor interaction, NOD-like receptor signaling pathway, and NF-κB signaling pathway. Proteomic analysis identified 201 differentially expressed proteins (DEPs), which were primarily associated with extracellular matrix destruction and remodeling, impairment of endothelial transport function, and inflammatory responses. Six genes (DUSP1, JUNB, NFKBIA, NR4A1, SERPINE1, and THBS1) were upregulated by OGD/R at both the mRNA and protein levels. In mice with cerebral ischemia and reperfusion, brain TNF signaling pathway was activated by reperfusion, and inhibiting TNF-α with adalimumab significantly attenuated reperfusion-induced brain endothelial inflammation. In addition, the protein level of THBS1 was substantially upregulated upon reperfusion in brain endothelial cells and the peri-endothelial area in mice receiving cerebral ischemia.

CONCLUSION

Our study reveals the key molecular signatures of brain endothelial reperfusion injury and provides potential therapeutic targets for the treatment of brain microvascular injury after reperfusion therapy in ischemic stroke.

Blood-based biomarkers of cerebral small vessel disease

Age-associated cerebral small vessel disease (CSVD) represents a clinically heterogenous condition, arising from diverse microvascular mechanisms. These lead to chronic cerebrovascular dysfunction and carry a substantial risk of subsequent stroke and vascular cognitive impairment in aging populations. Owing to advances in neuroimaging, in vivo visualization of cerebral vasculature abnormities and detection of CSVD, including lacunes, microinfarcts, microbleeds and white matter lesions, is now possible, but remains a resource-, skills- and time-intensive approach. As a result, there has been a recent proliferation of blood-based biomarker studies for CSVD aimed at developing accessible screening tools for early detection and risk stratification. However, a good understanding of the pathophysiological processes underpinning CSVD is needed to identify and assess clinically useful biomarkers. Here, we provide an overview of processes associated with CSVD pathogenesis, including endothelial injury and dysfunction, neuroinflammation, oxidative stress, perivascular neuronal damage as well as cardiovascular dysfunction. Then, we review clinical studies of the key biomolecules involved in the aforementioned processes. Lastly, we outline future trends and directions for CSVD biomarker discovery and clinical validation.

System biology approaches to identify hub genes linked with ECM organization and inflammatory signaling pathways in schizophrenia pathogenesis

Schizophrenia (SZ) is a chronic and devastating mental illness that affects around 20 million individuals worldwide. Cognitive deficits and structural and functional changes of the brain, abnormalities of brain ECM components, chronic neuroinflammation, and devastating clinical manifestation during SZ are likely etiological factors shown by affected individuals. However, the pathophysiological events associated with multiple regulatory pathways involved in the brain of this complex disorder are still unclear. This study aimed to develop a pipeline based on bioinformatics and systems biology approaches for identifying potential therapeutic targets involving possible biological mechanisms from SZ patients and healthy volunteers. About 420 overlapping differentially expressed genes (DEGs) from three RNA-seq datasets were identified. Gene ontology (GO), and pathways analysis showed several biological mechanisms enriched by the commonly shared DEGs, including extracellular matrix organization (ECM) organization, collagen fibril organization, integrin signaling pathway, inflammation mediated by chemokines and cytokines signaling pathway, and GABA-B receptor II and IL4 mediated signaling. Besides, 15 hub genes (FN1, COL1A1, COL3A1, COL1A2, COL5A1, COL2A1, COL6A2, COL6A3, MMP2, THBS1, DCN, LUM, HLA-A, HLA-C, and FBN1) were discovered by comprehensive analysis, which was mainly involved in the ECM organization and inflammatory signaling pathway. Furthermore, the miRNA target of the hub genes was analyzed with the random-forest-based approach software miRTarBase. In addition, the transcriptional factors and protein kinases regulating overlapping DEGs in SZ, namely, SUZ12, EZH2, TRIM28, TP53, EGR1, CSNK2A1, GSK3B, CDK1, and MAPK14, were also identified. The results point to a new understanding that the hub genes (fibronectin 1, collagen, matrix metalloproteinase-2, and lumican) in the ECM organization and inflammatory signaling pathways may be involved in the SZ occurrence and pathogenesis.

Live Mapping of the Brain Extracellular Matrix and Remodeling in Neurological Disorders

Live imaging of the brain extracellular matrix (ECM) provides vital insights into changes that occur in neurological disorders. Current techniques such as second or third-harmonic generation offer limited contrast for live imaging of the brain ECM. Here, a new method, pan-ECM via chemical labeling of extracellular proteins, is introduced for live brain ECM imaging. pan-ECM labels all major ECM components in live tissue including the interstitial matrix, basement membrane, and perineuronal nets. pan-ECM enables in vivo observation of the ECM heterogeneity between the glioma core and margin, as well as the assessment of ECM deterioration under stroke condition, without ECM shrinkage from tissue fixation. These findings indicate that the pan-ECM approach is a novel way to image the entire brain ECM in live brain tissue with optical resolution. pan-ECM has the potential to advance the understanding of ECM in brain function and neurological diseases.

CNS Drug Delivery in Stroke: Improving Therapeutic Translation From the Bench to the Bedside

Drug development for ischemic stroke is challenging as evidenced by the paucity of therapeutics that have advanced beyond a phase III trial. There are many reasons for this lack of clinical translation including factors related to the experimental design of preclinical studies. Often overlooked in therapeutic development for ischemic stroke is the requirement of effective drug delivery to the brain, which is critical for neuroprotective efficacy of several small and large molecule drugs. Advancing central nervous system drug delivery technologies implies a need for detailed comprehension of the blood-brain barrier (BBB) and neurovascular unit. Such knowledge will permit the innate biology of the BBB/neurovascular unit to be leveraged for improved bench-to-bedside translation of novel stroke therapeutics. In this review, we will highlight key aspects of BBB/neurovascular unit pathophysiology and describe state-of-the-art approaches for optimization of central nervous system drug delivery (ie, passive diffusion, mechanical opening of the BBB, liposomes/nanoparticles, transcytosis, intranasal drug administration). Additionally, we will discuss how endogenous BBB transporters represent the next frontier of drug delivery strategies for stroke. Overall, this review will provide cutting edge perspective on how central nervous system drug delivery must be considered for the advancement of new stroke drugs toward human trials.

Systematic identification of key basement membrane related genes as potential new biomarkers in Alzheimer's disease

OBJECTIVE

The study aimed to identify biomarkers associated with basement membranes (BMs)-related genes (BMGs) in Alzheimer's disease (AD) and investigate their potential role in the progression of AD pathology.

METHODS

Gene expression profiles were retrieved from Gene Expression Omnibus database. 222 human BMGs were collected from the relevant literature. Subsequently, the differentially expressed BMGs (DE-BMGs) were filtered, and the key DE-BMGs were identified using weighted gene correlation network analysis (WGCNA) and two machine learning algorithms. The expression levels, diagnostic values, clinical significances, enrichment analyses and regulatory networks of these candidate biomarkers were further examined.

RESULTS

A total of 44 DE-BMGs were acquired by comparing AD temporal cortex with nondemented controls. Using WGCNA and machine learning, versiscan (VCAN), tissue inhibitor of metalloproteinase 1 (TIMP1), structural maintenance of chromosome 3 (SMC3), and laminin β2 (LAMB2) were ultimately identified as candidate biomarkers, and they were verified in a murine model. These biomarkers had high diagnostic value (area under the curve (AUC)＞0.8). The diagnostic value of the four gene combination was then evaluated in multiple databases, yielding AUCs ranging from 0.688 to 1. Furthermore, a meaningful correlation between these biomarkers and AD pathology progression was observed. Finally, comprehensive analyses involving Hallmark pathway enrichment, immune cell infiltration analysis, transcriptional regulatory, and competitive endogenous RNA networks indicated that key DE-BMGs closely correlated with oxidative stress and immune dysfunction.

CONCLUSION

Our study comprehensively identified four candidate BMGs and their combination model that play a crucial part in the diagnosis and pathogenesis of AD.

Microfibrillar-associated protein 4 as a potential marker of acute relapse in inflammatory demyelinating diseases of the central nervous system: Pathological and clinical aspects

BACKGROUND

Microfibrillar-associated protein 4 (MFAP4) is an extracellular matrix protein not previously described in the human central nervous system (CNS).

OBJECTIVES

We determined MFAP4 CNS expression and measured cerebrospinal fluid (CSF) and serum levels.

METHODS

Tissue was sampled at autopsy from patients with acute multiple sclerosis (MS) (n = 3), progressive MS (n = 3), neuromyelitis optica spectrum disorder (NMOSD) (n = 2), and controls (n = 9), including 6 healthy controls (HC). MFAP4 levels were measured in 152 patients: 49 MS, 62 NMOSD, 22 myelin oligodendrocyte glycoprotein-associated disease (MOGAD), and 19 isolated optic neuritis (ION).

RESULTS

MFAP4 localized to meninges and vascular/perivascular spaces, intense in the optic nerve. At sites of active inflammation, MFAP4 reactivity was reduced in NMOSD and acute MS and less in progressive MS. CSF MFAP4 levels were reduced during relapse and at the onset of diseases (mean U/mL: MS 14.3, MOGAD 9.7, and ION 14.6 relative to HC 17.9. (p = 0.013, p = 0.000, and p = 0.019, respectively). Patients with acute ON (n = 68) had reduced CSF MFAP4 (mean U/mL: 14.5, p = 0.006). CSF MFAP4 levels correlated negatively with relapse severity (rho = -0.41, p = 0.017).

CONCLUSION

MFAP4 immunoreactivity was reduced at sites of active inflammation. CSF levels of MFAP4 were reduced following relapse and may reflect disease activity.

Research Progress on Natural Plant Molecules in Regulating the Blood-Brain Barrier in Alzheimer's Disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder. With the aging population and the continuous development of risk factors associated with AD, it will impose a significant burden on individuals, families, and society. Currently, commonly used therapeutic drugs such as Cholinesterase inhibitors, N-methyl-D-aspartate antagonists, and multiple AD pathology removal drugs have been shown to have beneficial effects on certain pathological conditions of AD. However, their clinical efficacy is minimal and they are associated with certain adverse reactions. Furthermore, the underlying pathological mechanism of AD remains unclear, posing a challenge for drug development. In contrast, natural plant molecules, widely available, offer multiple targeting pathways and demonstrate inherent advantages in modifying the typical pathologic features of AD by influencing the blood-brain barrier (BBB). We provide a comprehensive review of recent in vivo and in vitro studies on natural plant molecules that impact the BBB in the treatment of AD. Additionally, we analyze their specific mechanisms to offer novel insights for the development of safe and effective targeted drugs as well as guidance for experimental research and the clinical application of drugs for the prevention and treatment of AD.

Astroglial Connexin 43-Mediated Gap Junctions and Hemichannels: Potential Antidepressant Mechanisms and the Link to Neuroinflammation

Major depression disorder (MDD) is a neuropsychiatric disorder associated with a high suicide rate and a higher disability rate than any other disease. Evidence suggests that the pathological mechanism of MDD is related to astrocyte dysfunction. Depression is mainly associated with the expression of connexin 43 (Cx43) and the function of Cx43-mediated gap junctions and hemichannels in astrocytes. Moreover, neuroinflammation has been a hotspot in research on the pathology of depression, and Cx43-mediated functions are thought to be involved in neuroinflammation-related depression. However, the specific mechanism of Cx43-mediated functions in neuroinflammation-related depression pathology remains unclear. Therefore, this review summarizes and discusses Cx43 expression, the role of gap junction intercellular communication, and its relationship with neuroinflammation in depression. This review also focuses on the effects of antidepressant drugs (e.g., monoamine antidepressants, psychotropic drugs, and N-methyl-D-aspartate receptor antagonists) on Cx43-mediated function and provides evidence for Cx43 as a novel target for the treatment of MDD. The pathogenesis of MDD is related to astrocyte dysfunction, with reduced Cx43 expression, GJ dysfunction, decreased GJIC and reduced BDNF expression in the depressed brain. The effect of Cx43 on neuroinflammation-related depression involving inflammatory cytokines, glutamate excitotoxicity, and HPA axis dysregulation. Antidepressant drugs targeting Cx43 can effectively relieve depressive symptoms.

Damage mechanism and therapy progress of the blood-brain barrier after ischemic stroke

The blood-brain barrier (BBB) serves as a defensive line protecting the central nervous system, while also maintaining micro-environment homeostasis and inhibiting harmful materials from the peripheral blood. However, the BBB's unique physiological functions and properties make drug delivery challenging for patients with central nervous system diseases. In this article, we briefly describe the cell structure basis and mechanism of action of the BBB, as well as related functional proteins involved. Additionally, we discuss the various mechanisms of BBB damage following the onset of an ischemic stroke, and lastly, we mention several therapeutic strategies accounting for impairment mechanisms. We hope to provide innovative ideas for drug delivery research via the BBB.

ADAR1 suppression causes interferon signaling and transposable element transcript accumulation in human astrocytes

Neuroinflammation is a central mechanism of brain aging and Alzheimer's disease (AD), but the exact causes of age- and AD-related neuroinflammation are incompletely understood. One potential modulator of neuroinflammation is the enzyme adenosine deaminase acting on RNA 1 (ADAR1), which regulates the accumulation of endogenous double-stranded RNA (dsRNA), a pro-inflammatory/innate immune activator. However, the role of ADAR1 and its transcriptomic targets in astrocytes, key mediators of neuroinflammation, have not been comprehensively investigated. Here, we knock down ADAR1 in primary human astrocytes via siRNA transfection and use transcriptomics (RNA-seq) to show that this results in: (1) increased expression of type I interferon and pro-inflammatory signaling pathways and (2) an accumulation of transposable element (TE) transcripts with the potential to form dsRNA. We also show that our findings may be clinically relevant, as ADAR1 gene expression declines with brain aging and AD in humans, and this is associated with a similar increase in TE transcripts. Together, our results suggest an important role for ADAR1 in preventing pro-inflammatory activation of astrocytes in response to endogenous dsRNA with aging and AD.

Cortistatin deficiency reveals a dysfunctional brain endothelium with impaired gene pathways, exacerbated immune activation, and disrupted barrier integrity

BACKGROUND

Brain activity governing cognition and behaviour depends on the fine-tuned microenvironment provided by a tightly controlled blood-brain barrier (BBB). Brain endothelium dysfunction is a hallmark of BBB breakdown in most neurodegenerative/neuroinflammatory disorders. Therefore, the identification of new endogenous molecules involved in endothelial cell disruption is essential to better understand BBB dynamics. Cortistatin is a neuroimmune mediator with anti-inflammatory and neuroprotective properties that exerts beneficial effects on the peripheral endothelium. However, its role in the healthy and injured brain endothelium remains to be evaluated. Herein, this study aimed to investigate the potential function of endogenous and therapeutic cortistatin in regulating brain endothelium dysfunction in a neuroinflammatory/neurodegenerative environment.

METHODS

Wild-type and cortistatin-deficient murine brain endothelium and human cells were used for an in vitro barrier model, where a simulated ischemia-like environment was mimicked. Endothelial permeability, junction integrity, and immune response in the presence and absence of cortistatin were evaluated using different size tracers, immunofluorescence labelling, qPCR, and ELISA. Cortistatin molecular mechanisms underlying brain endothelium dynamics were assessed by RNA-sequencing analysis. Cortistatin role in BBB leakage was evaluated in adult mice injected with LPS.

RESULTS

The endogenous lack of cortistatin predisposes endothelium weakening with increased permeability, tight-junctions breakdown, and dysregulated immune activity. We demonstrated that both damaged and uninjured brain endothelial cells isolated from cortistatin-deficient mice, present a dysregulated and/or deactivated genetic programming. These pathways, related to basic physiology but also crucial for the repair after damage (e.g., extracellular matrix remodelling, angiogenesis, response to oxygen, signalling, and metabolites transport), are dysfunctional and make brain endothelial barrier lacking cortistatin non-responsive to any further injury. Treatment with cortistatin reversed in vitro hyperpermeability, tight-junctions disruption, inflammatory response, and reduced in vivo BBB leakage.

CONCLUSIONS

The neuropeptide cortistatin has a key role in the physiology of the cerebral microvasculature and its presence is crucial to develop a canonical balanced response to damage. The reparative effects of cortistatin in the brain endothelium were accompanied by the modulation of the immune function and the rescue of barrier integrity. Cortistatin-based therapies could emerge as a novel pleiotropic strategy to ameliorate neuroinflammatory/neurodegenerative disorders with disrupted BBB.

Novel homozygous LAMB1 in-frame deletion in a pediatric patient with brain anomalies and cerebrovascular event

Biallelic pathogenic variants in LAMB1 have been associated with autosomal recessive lissencephaly 5 (OMIM 615191), which is characterized by brain malformations (cobblestone lissencephaly, hydrocephalus), developmental delay, and epilepsy. Pathogenic variants in LAMB1 are rare, with only 11 pathogenic variants and 11 patients reported to date. Here, we report on a 6-year-old patient from a consanguineous family with profound developmental delay, microcephaly, and a history of a perinatal cerebrovascular event. Brain magnetic resonance imaging (MRI) showed cerebellar cystic defects, signal intensity abnormalities, and a hypoplastic corpus callosum. Trio-exome analysis revealed a homozygous in-frame deletion of Exons 23 and 24 of LAMB1 affecting 104 amino acids including the epidermal growth factor (EGF)-like units 11 and 12 in Domain III. To our knowledge, this is the first reported in-frame deletion in LAMB1. Our findings broaden the clinical and molecular spectrum of LAMB1-associated syndromes.

Ozanimod differentially preserves human cerebrovascular endothelial barrier proteins and attenuates matrix metalloproteinase-9 activity following in vitro acute ischemic injury

Endothelial integrity is critical in mitigating a vicious cascade of secondary injuries following acute ischemic stroke (AIS). Matrix metalloproteinase-9 (MMP-9), a contributor to endothelial integrity loss, is elevated during stroke and is associated with worsened stroke outcome. We investigated the FDA-approved selective sphingosine-1-phosphate receptor 1 (S1PR1) ligand, ozanimod, on the regulation/activity of MMP-9 as well as endothelial barrier components [platelet endothelial cell adhesion molecule 1 (PECAM-1), claudin-5, and zonula occludens 1 (ZO-1)] in human brain microvascular endothelial cells (HBMECs) following hypoxia plus glucose deprivation (HGD). We previously reported that S1PR1 activation improves HBMEC integrity; however, mechanisms underlying S1PR1 involvement in endothelial cell barrier integrity have not been clearly elucidated. We hypothesized that ozanimod would attenuate an HGD-induced increase in MMP-9 activity that would concomitantly attenuate the loss of integral barrier components. Male HBMECs were treated with ozanimod or vehicle and exposed to 3 h of normoxia (21% O2) or HGD (1% O2). Immunoblotting, zymography, qRT-PCR, and immunocytochemical labeling techniques assessed processes related to MMP-9 and barrier markers. We observed that HGD acutely increased MMP-9 activity and reduced claudin-5 and PECAM-1 levels, and ozanimod attenuated these responses. In situ analysis, via PROSPER, suggested that attenuation of MMP-9 activity may be a primary factor in maintaining these integral barrier proteins. We also observed that HGD increased intracellular mechanisms associated with augmented MMP-9 activation; however, ozanimod had no effect on these select factors. Thus, we conclude that ozanimod has the potential to attenuate HGD-mediated decreases in HBMEC integrity in part by decreasing MMP-9 activity as well as preserving barrier properties.NEW & NOTEWORTHY We have identified a potential novel mechanism by which ozanimod, a selective sphingosine-1-phosphate receptor 1 (S1PR1) agonist, attenuates hypoxia plus glucose deprivation (HGD)-induced matrix metalloproteinase-9 (MMP-9) activity and disruptions in integral human brain endothelial cell barrier proteins. Our results suggest that ischemic-like injury elicits increased MMP-9 activity and alterations of barrier integrity proteins in human brain microvascular endothelial cells (HBMECs) and that ozanimod via S1PR1 attenuates these HGD-induced responses, adding to its therapeutic potential in cerebrovascular protection during the acute phase of ischemic stroke.

Stroke-induced damage on the blood-brain barrier

The blood-brain barrier (BBB) is a functional phenotype exhibited by the neurovascular unit (NVU). It is maintained and regulated by the interaction between cellular and non-cellular matrix components of the NVU. The BBB plays a vital role in maintaining the dynamic stability of the intracerebral microenvironment as a barrier layer at the critical interface between the blood and neural tissues. The large contact area (approximately 20 m2/1.3 kg brain) and short diffusion distance between neurons and capillaries allow endothelial cells to dominate the regulatory role. The NVU is a structural component of the BBB. Individual cells and components of the NVU work together to maintain BBB stability. One of the hallmarks of acute ischemic stroke is the disruption of the BBB, including impaired function of the tight junction and other molecules, as well as increased BBB permeability, leading to brain edema and a range of clinical symptoms. This review summarizes the cellular composition of the BBB and describes the protein composition of the barrier functional junction complex and the mechanisms regulating acute ischemic stroke-induced BBB disruption.

ABCB1 and ABCG2 Regulation at the Blood-Brain Barrier: Potential New Targets to Improve Brain Drug Delivery

The drug efflux transporters ABCB1 and ABCG2 at the blood-brain barrier limit the delivery of drugs into the brain. Strategies to overcome ABCB1/ABCG2 have been largely unsuccessful, which poses a tremendous clinical problem to successfully treat central nervous system (CNS) diseases. Understanding basic transporter biology, including intracellular regulation mechanisms that control these transporters, is critical to solving this clinical problem.In this comprehensive review, we summarize current knowledge on signaling pathways that regulate ABCB1/ABCG2 at the blood-brain barrier. In Section I, we give a historical overview on blood-brain barrier research and introduce the role that ABCB1 and ABCG2 play in this context. In Section II, we summarize the most important strategies that have been tested to overcome the ABCB1/ABCG2 efflux system at the blood-brain barrier. In Section III, the main component of this review, we provide detailed information on the signaling pathways that have been identified to control ABCB1/ABCG2 at the blood-brain barrier and their potential clinical relevance. This is followed by Section IV, where we explain the clinical implications of ABCB1/ABCG2 regulation in the context of CNS disease. Lastly, in Section V, we conclude by highlighting examples of how transporter regulation could be targeted for therapeutic purposes in the clinic. SIGNIFICANCE STATEMENT: The ABCB1/ABCG2 drug efflux system at the blood-brain barrier poses a significant problem to successful drug delivery to the brain. The article reviews signaling pathways that regulate blood-brain barrier ABCB1/ABCG2 and could potentially be targeted for therapeutic purposes.

Pericyte-Mediated Molecular Mechanisms Underlying Tissue Repair and Functional Recovery after Ischemic Stroke

There are still many patients suffering from ischemic stroke and related disabilities worldwide. To develop a treatment that promotes functional recovery after acute ischemic stroke, we need to elucidate endogenous tissue repair mechanisms. The concept of a neurovascular unit (NVU) indicates the importance of a complex orchestration of cell-cell interactions and their microenvironment in the physiology and pathophysiology of various central nervous system diseases, particularly ischemic stroke. In this concept, microvascular pericytes play a crucial role in regulating the blood-brain barrier integrity, cerebral blood flow (CBF), and vascular stability. Recent evidence suggests that pericytes are also involved in the tissue repair leading to functional recovery following acute ischemic stroke through the interaction with other cell types constituting the NVU; pericytes may organize CBF recovery, macrophage-mediated clearance of myelin debris, intrainfarct fibrosis, and periinfarct astrogliosis and remyelination. In this review, we will discuss the physiological and pathophysiological functions of pericytes, their involvement in the molecular mechanisms underlying tissue repair and functional recovery after ischemic stroke, and a therapeutic strategy to promote endogenous regeneration.

Polymeric and biological membranes for organ-on-a-chip devices

Membranes are fundamental elements within organ-on-a-chip (OOC) platforms, as they provide adherent cells with support, allow nutrients (and other relevant molecules) to permeate/exchange through membrane pores, and enable the delivery of mechanical or chemical stimuli. Through OOC platforms, physiological processes can be studied in vitro, whereas OOC membranes broaden knowledge of how mechanical and chemical cues affect cells and organs. OOCs with membranes are in vitro microfluidic models that are used to replace animal testing for various applications, such as drug discovery and disease modeling. In this review, the relevance of OOCs with membranes is discussed as well as their scaffold and actuation roles, properties (physical and material), and fabrication methods in different organ models. The purpose was to aid readers with membrane selection for the development of OOCs with specific applications in the fields of mechanistic, pathological, and drug testing studies. Mechanical stimulation from liquid flow and cyclic strain, as well as their effects on the cell's increased physiological relevance (IPR), are described in the first section. The review also contains methods to fabricate synthetic and ECM (extracellular matrix) protein membranes, their characteristics (e.g., thickness and porosity, which can be adjusted depending on the application, as shown in the graphical abstract), and the biological materials used for their coatings. The discussion section joins and describes the roles of membranes for different research purposes and their advantages and challenges.

Analysis of matrisome expression patterns in murine and human dorsal root ganglia

The extracellular matrix (ECM) is a dynamic structure of molecules that can be divided into six different categories and are collectively called the matrisome. The ECM plays pivotal roles in physiological processes in many tissues, including the nervous system. Intriguingly, alterations in ECM molecules/pathways are associated with painful human conditions and murine pain models. Nevertheless, mechanistic insight into the interplay of normal or defective ECM and pain is largely lacking. The goal of this study was to integrate bulk, single-cell, and spatial RNA sequencing (RNAseq) datasets to investigate the expression and cellular origin of matrisome genes in male and female murine and human dorsal root ganglia (DRG). Bulk RNAseq showed that about 65% of all matrisome genes were expressed in both murine and human DRG, with proportionally more core matrisome genes (glycoproteins, collagens, and proteoglycans) expressed compared to matrisome-associated genes (ECM-affiliated genes, ECM regulators, and secreted factors). Single cell RNAseq on male murine DRG revealed the cellular origin of matrisome expression. Core matrisome genes, especially collagens, were expressed by fibroblasts whereas matrisome-associated genes were primarily expressed by neurons. Cell-cell communication network analysis with CellChat software predicted an important role for collagen signaling pathways in connecting vascular cell types and nociceptors in murine tissue, which we confirmed by analysis of spatial transcriptomic data from human DRG. RNAscope in situ hybridization and immunohistochemistry demonstrated expression of collagens in fibroblasts surrounding nociceptors in male and female human DRG. Finally, comparing human neuropathic pain samples with non-pain samples also showed differential expression of matrisome genes produced by both fibroblasts and by nociceptors. This study supports the idea that the DRG matrisome may contribute to neuronal signaling in both mouse and human, and that dysregulation of matrisome genes is associated with neuropathic pain.

Blood-Brain Barrier Breakdown in Neuroinflammation: Current In Vitro Models

The blood-brain barrier, which is formed by tightly interconnected microvascular endothelial cells, separates the brain from the peripheral circulation. Together with other central nervous system-resident cell types, including pericytes and astrocytes, the blood-brain barrier forms the neurovascular unit. Upon neuroinflammation, this barrier becomes leaky, allowing molecules and cells to enter the brain and to potentially harm the tissue of the central nervous system. Despite the significance of animal models in research, they may not always adequately reflect human pathophysiology. Therefore, human models are needed. This review will provide an overview of the blood-brain barrier in terms of both health and disease. It will describe all key elements of the in vitro models and will explore how different compositions can be utilized to effectively model a variety of neuroinflammatory conditions. Furthermore, it will explore the existing types of models that are used in basic research to study the respective pathologies thus far.

Neuroprotective compounds from marine invertebrates

Background

Neuroinflammation is a key pathological feature of a wide variety of neurological disorders, including Parkinson’s, multiple sclerosis, Alzheimer’s, and Huntington’s disease. While current treatments for these disorders are primarily symptomatic, there is a growing interest in developing new therapeutics that target the underlying neuroinflammatory processes.

Main body

Marine invertebrates, such as coral, sea urchins, starfish, sponges, and sea cucumbers, have been found to contain a wide variety of biologically active compounds that have demonstrated potential therapeutic properties. These compounds are known to target various key proteins and pathways in neuroinflammation, including 6-hydroxydopamine (OHDH), caspase-3 and caspase-9, p-Akt, p-ERK, p-P38, acetylcholinesterase (AChE), amyloid-β (Aβ), HSF-1, α-synuclein, cellular prion protein, advanced glycation end products (AGEs), paraquat (PQ), and mitochondria DJ-1.

Short conclusion

This review focuses on the current state of research on the neuroprotective effects of compounds found in marine invertebrates and the potential therapeutic implications of these findings for treating neuroinflammatory disorders. We also discussed the challenges and limitations of using marine-based compounds as therapeutics, such as sourcing and sustainability concerns, and the need for more preclinical and clinical studies to establish their efficacy and safety.

Graphical abstract

Defining blood-induced microglia functions in neurodegeneration through multiomic profiling

Blood protein extravasation through a disrupted blood-brain barrier and innate immune activation are hallmarks of neurological diseases and emerging therapeutic targets. However, how blood proteins polarize innate immune cells remains largely unknown. Here, we established an unbiased blood-innate immunity multiomic and genetic loss-of-function pipeline to define the transcriptome and global phosphoproteome of blood-induced innate immune polarization and its role in microglia neurotoxicity. Blood induced widespread microglial transcriptional changes, including changes involving oxidative stress and neurodegenerative genes. Comparative functional multiomics showed that blood proteins induce distinct receptor-mediated transcriptional programs in microglia and macrophages, such as redox, type I interferon and lymphocyte recruitment. Deletion of the blood coagulation factor fibrinogen largely reversed blood-induced microglia neurodegenerative signatures. Genetic elimination of the fibrinogen-binding motif to CD11b in Alzheimer's disease mice reduced microglial lipid metabolism and neurodegenerative signatures that were shared with autoimmune-driven neuroinflammation in multiple sclerosis mice. Our data provide an interactive resource for investigation of the immunology of blood proteins that could support therapeutic targeting of microglia activation by immune and vascular signals.

Strategic outline of interventions targeting extracellular matrix for promoting healthy longevity

The extracellular matrix (ECM), composed of interlinked proteins outside of cells, is an important component of the human body that helps maintain tissue architecture and cellular homeostasis. As people age, the ECM undergoes changes that can lead to age-related morbidity and mortality. Despite its importance, ECM aging remains understudied in the field of geroscience. In this review, we discuss the core concepts of ECM integrity, outline the age-related challenges and subsequent pathologies and diseases, summarize diagnostic methods detecting a faulty ECM, and provide strategies targeting ECM homeostasis. To conceptualize this, we built a technology research tree to hierarchically visualize possible research sequences for studying ECM aging. This strategic framework will hopefully facilitate the development of future research on interventions to restore ECM integrity, which could potentially lead to the development of new drugs or therapeutic interventions promoting health during aging.

The Role of Vitamin D in Neuroprotection in Multiple Sclerosis: An Update

Multiple sclerosis (MS) is a complex neurological condition that involves both inflammatory demyelinating and neurodegenerative components. MS research and treatments have traditionally focused on immunomodulation, with less investigation of neuroprotection, and this holds true for the role of vitamin D in MS. Researchers have already established that vitamin D plays an anti-inflammatory role in modulating the immune system in MS. More recently, researchers have begun investigating the potential neuroprotective role of vitamin D in MS. The active form of vitamin D, 1,25(OH)₂D₃, has a range of neuroprotective properties, which may be important in remyelination and/or the prevention of demyelination. The most notable finding relevant to MS is that 1,25(OH)₂D₃ promotes stem cell proliferation and drives the differentiation of neural stem cells into oligodendrocytes, which carry out remyelination. In addition, 1,25(OH)₂D₃ counteracts neurodegeneration and oxidative stress by suppressing the activation of reactive astrocytes and M1 microglia. 1,25(OH)₂D₃ also promotes the expression of various neuroprotective factors, including neurotrophins and antioxidant enzymes. 1,25(OH)₂D₃ decreases blood-brain barrier permeability, reducing leukocyte recruitment into the central nervous system. These neuroprotective effects, stimulated by 1,25(OH)₂D₃, all enhance neuronal survival. This review summarizes and connects the current evidence supporting the vitamin D-mediated mechanisms of action for neuroprotection in MS.

Targeting lysyl-oxidase (LOX) may facilitate intramural periarterial drainage for the treatment of Alzheimer's disease

Alzheimer's disease is the commonest form of dementia. It is likely that a lack of clearance of amyloid beta (Aβ) results in its accumulation in the parenchyma as Aβ oligomers and insoluble plaques, and within the walls of blood vessels as cerebral amyloid angiopathy (CAA). The drainage of Aβ along the basement membranes of blood vessels as intramural periarterial drainage (IPAD), could be improved if the driving force behind IPAD could be augmented, therefore reducing Aβ accumulation. There are alterations in the composition of the vascular basement membrane in Alzheimer's disease. Lysyl oxidase (LOX) is an enzyme involved in the remodelling of the extracellular matrix and its expression and function is altered in various disease states. The expression of LOX is increased in Alzheimer's disease, but it is unclear whether this is a contributory factor in the impairment of IPAD in Alzheimer's disease. The pharmacological inhibition of LOX may be a strategy to improve IPAD and reduce the accumulation of Aβ in the parenchyma and within the walls of blood vessels.