Blood-spinal cord barrier pericyte reductions contribute to increased capillary permeability

No-reflow after recanalization in ischemic stroke: From pathomechanisms to therapeutic strategies

Endovascular reperfusion therapy is the primary strategy for acute ischemic stroke. No-reflow is a common phenomenon, which is defined as the failure of microcirculatory reperfusion despite clot removal by thrombolysis or mechanical embolization. It has been reported that up to 25% of ischemic strokes suffer from no-reflow, which strongly contributes to an increased risk of poor clinical outcomes. No-reflow is associated with functional and structural alterations of cerebrovascular microcirculation, and the injury to the microcirculation seriously hinders the neural functional recovery following macrovascular reperfusion. Accumulated evidence indicates that pathology of no-reflow is linked to adhesion, aggregation, and rolling of blood components along the endothelium, capillary stagnation with neutrophils, astrocytes end-feet, and endothelial cell edema, pericyte contraction, and vasoconstriction. Prevention or treatment strategies aim to alleviate or reverse these pathological changes, including targeted therapies such as cilostazol, adhesion molecule blocking antibodies, peroxisome proliferator-activated receptors (PPARs) activator, adenosine, pericyte regulators, as well as adjunctive therapies, such as extracorporeal counterpulsation, ischemic preconditioning, and alternative or complementary therapies. Herein, we provide an overview of pathomechanisms, predictive factors, diagnosis, and intervention strategies for no-reflow, and attempt to convey a new perspective on the clinical management of no-reflow post-ischemic stroke.

Brain Targeting Nanomedicines: Pitfalls and Promise

Brain diseases are the most devastating problem among the world's increasingly aging population, and the number of patients with neurological diseases is expected to increase in the future. Although methods for delivering drugs to the brain have advanced significantly, none of these approaches provide satisfactory results for the treatment of brain diseases. This remains a challenge due to the unique anatomy and physiology of the brain, including tight regulation and limited access of substances across the blood-brain barrier. Nanoparticles are considered an ideal drug delivery system to hard-to-reach organs such as the brain. The development of new drugs and new nanomaterial-based brain treatments has opened various opportunities for scientists to develop brain-specific delivery systems that could improve treatment outcomes for patients with brain disorders such as Alzheimer's disease, Parkinson's disease, stroke and brain tumors. In this review, we discuss noteworthy literature that examines recent developments in brain-targeted nanomedicines used in the treatment of neurological diseases.

Spinal Cord Injury Management Based on Microglia-Targeting Therapies

Spinal cord injury is a complicated medical condition both from the clinician's point of view in terms of management and from the patient's perspective in terms of unsatisfactory recovery. Depending on the severity, this disorder can be devastating despite the rapid and appropriate use of modern imaging techniques and convenient surgical spinal cord decompression and stabilization. In this context, there is a mandatory need for novel adjunctive therapeutic approaches to classical treatments to improve rehabilitation chances and clinical outcomes. This review offers a new and original perspective on therapies targeting the microglia, one of the most relevant immune cells implicated in spinal cord disorders. The first part of the manuscript reviews the anatomical and pathophysiological importance of the blood-spinal cord barrier components, including the role of microglia in post-acute neuroinflammation. Subsequently, the authors present the emerging therapies based on microglia modulation, such as cytokines modulators, stem cell, microRNA, and nanoparticle-based treatments that could positively impact spinal cord injury management. Finally, future perspectives and challenges are also highlighted based on the ongoing clinical trials related to medications targeting microglia.

Impact of Helicobacter pylori and metabolic syndrome on mast cell activation-related pathophysiology and neurodegeneration

Both Helicobacter pylori (H. pylori) infection and metabolic syndrome (MetS) are highly prevalent worldwide. The emergence of relevant research suggesting a pathogenic linkage between H. pylori infection and MetS-related cardio-cerebrovascular diseases and neurodegenerative disorders, particularly through mechanisms involving brain pericyte deficiency, hyperhomocysteinemia, hyperfibrinogenemia, elevated lipoprotein-a, galectin-3 overexpression, atrial fibrillation, and gut dysbiosis, has raised stimulating questions regarding their pathophysiology and its translational implications for clinicians. An additional stimulating aspect refers to H. pylori and MetS-related activation of innate immune cells, mast cells (MC), which is an important, often early, event in systemic inflammatory pathologies and related brain disorders. Synoptically, MC degranulation may play a role in the pathogenesis of H. pylori and MetS-related obesity, adipokine effects, dyslipidemia, diabetes mellitus, insulin resistance, arterial hypertension, vascular dysfunction and arterial stiffness, an early indicator of atherosclerosis associated with cardio-cerebrovascular and neurodegenerative disorders. Meningeal MC can be activated by triggers including stress and toxins resulting in vascular changes and neurodegeneration. Likewise, H.pylori and MetS-related MC activation is linked with: (a) vasculitis and thromboembolic events that increase the risk of cardio-cerebrovascular and neurodegenerative disorders, and (b) gut dysbiosis-associated neurodegeneration, whereas modulation of gut microbiota and MC activation may promote neuroprotection. This narrative review investigates the intricate relationship between H. pylori infection, MetS, MC activation, and their collective impact on pathophysiological processes linked to neurodegeneration. Through a comprehensive search of current literature, we elucidate the mechanisms through which H. pylori and MetS contribute to MC activation, subsequently triggering cascades of inflammatory responses. This highlights the role of MC as key mediators in the pathogenesis of cardio-cerebrovascular and neurodegenerative disorders, emphasizing their involvement in neuroinflammation, vascular dysfunction and, ultimately, neuronal damage. Although further research is warranted, we provide a novel perspective on the pathophysiology and management of brain disorders by exploring potential therapeutic strategies targeting H. pylori eradication, MetS management, and modulation of MC to mitigate neurodegeneration risk while promoting neuroprotection.

Carbenoxolone mitigates extensive fibrosis formation in PLP-induced EAE model and multiple sclerosis serum-exposed pericyte culture

Introduction

Multiple sclerosis (MS) is one of the most common causes of disability in young adults. Nearly, 85% of MS cases start with attacks and remissions, classified as relapsing-remitting multiple sclerosis (RRMS). With repeating attacks, MS causes brain-spinal cord atrophy and enhanced disability as disease progresses. PLP-induced EAE is one of the most established models for pathophysiology and treatment of RRMS. Recent studies demonstrated the possible role of pericytes in perivascular and intra-lesional fibrosis in PLP-induced EAE, whose importance remains elusive. Hence, we have investigated the possible role of pericytes in fibrosis formation and amelioration with a hemichannel blocker, Carbenoxolone (CBX).

Methods

PLP-induced experimental autoimmune encephalitis (EAE) model is used and the effect of CBX is investigated. Clinical scores were recorded and followed. Perivascular Collagen 1 and 3 accumulations were demonstrated as markers of fibrosis in the spinal cord. To delineate the role of pericytes, human brain vascular pericytes (HBVP) were incubated with the sera of MS patients to induce in-vitro MS model and the fibrosis formation was investigated.

Results

In the PLP induced in-vivo model, both intracerebroventricular and intraperitoneal CBX have significantly mitigated the disease progression followed by clinical scores, demyelination, and fibrosis. Moreover, CBX significantly mitigated MS-serum-induced fibrosis in the HBVP cell culture.

Discussion

The study demonstrated two important findings. First, CBX decreases fibrosis formation in both in-vivo and in-vitro MS models. Secondly, it improves neurological scores and decreases demyelination in the EAE model. Therefore, CBX can be potential novel therapeutic option in treating Multiple Sclerosis.

The Role of Helicobacter pylori and Metabolic Syndrome-Related Mast Cell Activation Pathologies and Their Potential Impact on Pregnancy and Neonatal Outcomes

Helicobacter pylori infection, a significant global burden beyond the gastrointestinal tract, has long been implicated in various systemic pathologies. Rising evidence suggests that the bacterium's intricate relationship with the immune system and its potential to induce chronic inflammation impact diverse pathophysiological processes in pregnant women that may in turn affect the incidence of several adverse pregnancy and neonate outcomes. Helicobacter pylori infection, which has been linked to metabolic syndrome and other disorders by provoking pericyte dysfunction, hyperhomocysteinemia, galectin-3, atrial fibrillation, gut dysbiosis, and mast cell activation pathologies, may also contribute to adverse pregnancy and neonatal outcomes. Together with increasing our biological understanding of the individual and collective involvement of Helicobacter pylori infection-related metabolic syndrome and concurrent activation of mast cells in maternal, fetus, and neonatal health outcomes, the present narrative review may foster related research endeavors to offer novel therapeutic approaches and informed clinical practice interventions to mitigate relevant risks of this critical topic among pregnant women and their offspring.

β1 integrins play a critical role maintaining vascular integrity in the hypoxic spinal cord, particularly in white matter

Interactions between extracellular matrix (ECM) proteins and β1 integrins play an essential role maintaining vascular integrity in the brain, particularly under vascular remodeling conditions. As blood vessels in the spinal cord are reported to have distinct properties from those in the brain, here we examined the impact of β1 integrin inhibition on spinal cord vascular integrity, both under normoxic conditions, when blood vessels are stable, and during exposure to chronic mild hypoxia (CMH), when extensive vascular remodeling occurs. We found that a function-blocking β1 integrin antibody triggered a small degree of vascular disruption in the spinal cord under normoxic conditions, but under hypoxic conditions, it greatly enhanced (20-fold) vascular disruption, preferentially in spinal cord white matter (WM). This resulted in elevated microglial activation as well as marked loss of myelin integrity and reduced density of oligodendroglial cells. To understand why vascular breakdown is localized to WM, we compared expression levels of major BBB components of WM and grey matter (GM) blood vessels, but this revealed no obvious differences. Interestingly however, hypoxyprobe staining demonstrated that the most severe levels of spinal cord hypoxia induced by CMH occurred in the WM. Analysis of brain tissue revealed a similar preferential vulnerability of WM tracts to show vascular disruption under these conditions. Taken together, these findings demonstrate an essential role for β1 integrins in maintaining vascular integrity in the spinal cord, and unexpectedly, reveal a novel and fundamental difference between WM and GM blood vessels in their dependence on β1 integrin function during hypoxic exposure. Our data support the concept that the preferential WM vulnerability described may be less a result of intrinsic differences in vascular barrier properties between WM and GM, and more a consequence of differences in vascular density and architecture.

Asiaticoside Attenuates Blood-Spinal Cord Barrier Disruption by Inhibiting Endoplasmic Reticulum Stress in Pericytes After Spinal Cord Injury

The blood-spinal cord barrier (BSCB) plays a vital role in the recovery of spinal cord function after spinal cord injury (SCI). Pericytes, pluripotent members of the neurovascular unit (NVU), receive signals from neighboring cells and are critical for maintaining CNS function. Therapeutic targets for the BSCB include endothelial cells (ECs) and glial cells, but few drugs target pericytes. This study was designed to explore whether asiaticoside has a positively effect on pericytes and the integrity of the BSCB. In this study, we found that asiaticoside could inhibit the loss of junction proteins just 1 day after SCI in vivo, but our in vitro study showed no significant differences in the expression of endothelial junction proteins between the control and asiaticoside treatment groups. We also found that asiaticoside could inhibit endoplasmic reticulum (ER) stress and pericyte apoptosis, which might be associated with the inhibition of junction protein reduction in ECs. Thus, we investigated the interactions between pericytes and ECs. Our results showed that asiaticoside could decrease the release of matrix metalloproteinase (MMP)-9 in pericytes and therefore upregulate the expression of junction proteins in ECs. Furthermore, the protective effect of asiaticoside on pericytes is related to the inhibition of ER stress via the MAPK signaling pathway. Taken together, our results demonstrate that asiaticoside treatment inhibits BSCB disruption and enhances functional recovery after SCI.

The role of endothelial cell-pericyte interactions in vascularization and diseases

BACKGROUND

Endothelial cells (ECs) and pericytes (PCs) are crucial components of the vascular system, with ECs lining the inner layer of blood vessels and PCs surrounding capillaries to regulate blood flow and angiogenesis. Intercellular communication between ECs and PCs is vital for the formation, stability, and function of blood vessels. Various signaling pathways, such as the vascular endothelial growth factor/vascular endothelial growth factor receptor pathway and the platelet-derived growth factor-B/platelet-derived growth factor receptor-β pathway, play roles in communication between ECs and PCs. Dysfunctional communication between these cells is associated with various diseases, including vascular diseases, central nervous system disorders, and certain types of cancers.

AIM OF REVIEW

This review aimed to explore the diverse roles of ECs and PCs in the formation and reshaping of blood vessels. This review focused on the essential signaling pathways that facilitate communication between these cells and investigated how disruptions in these pathways may contribute to disease. Additionally, the review explored potential therapeutic targets, future research directions, and innovative approaches, such as investigating the impact of EC-PCs in novel systemic diseases, addressing resistance to antiangiogenic drugs, and developing novel antiangiogenic medications to enhance therapeutic efficacy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Disordered EC-PC intercellular signaling plays a role in abnormal blood vessel formation, thus contributing to the progression of various diseases and the development of resistance to antiangiogenic drugs. Therefore, studies on EC-PC intercellular interactions have high clinical relevance.

Intruders or protectors - the multifaceted role of B cells in CNS disorders

B lymphocytes are immune cells studied predominantly in the context of peripheral humoral immune responses against pathogens. Evidence has been accumulating in recent years on the diversity of immunomodulatory functions that B cells undertake, with particular relevance for pathologies of the central nervous system (CNS). This review summarizes current knowledge on B cell populations, localization, infiltration mechanisms, and function in the CNS and associated tissues. Acute and chronic neurodegenerative pathologies are examined in order to explore the complex, and sometimes conflicting, effects that B cells can have in each context, with implications for disease progression and treatment outcomes. Additional factors such as aging modulate the proportions and function of B cell subpopulations over time and are also discussed in the context of neuroinflammatory response and disease susceptibility. A better understanding of the multifactorial role of B cell populations in the CNS may ultimately lead to innovative therapeutic strategies for a variety of neurological conditions.

Nanoparticle-mediated delivery of non-viral gene editing technology to the brain

Neurological disorders pose a significant burden on individuals and society, affecting millions worldwide. These disorders, including but not limited to Alzheimer's disease, Parkinson's disease, and Huntington's disease, often have limited treatment options and can lead to progressive degeneration and disability. Gene editing technologies, including Zinc Finger Nucleases (ZFN), Transcription Activator-Like Effector Nucleases (TALEN), and Clustered Regularly Interspaced Short Palindromic Repeats-associated Protein 9 (CRISPR-Cas9), offer a promising avenue for potential cures by targeting and correcting the underlying genetic mutations responsible for neurologic disorders. However, efficient delivery methods are crucial for the successful application of gene editing technologies in the context of neurological disorders. The central nervous system presents unique challenges to treatment development due to the blood-brain barrier, which restricts the entry of large molecules. While viral vectors are traditionally used for gene delivery, nonviral delivery methods, such as nanoparticle-mediated delivery, offer safer alternatives that can efficiently transport gene editing components. Herein we aim to introduce the three main gene editing nucleases as nonviral treatments for neurologic disorders, the delivery barriers associated with brain targeting, and the current nonviral techniques used for brain-specific delivery. We highlight the challenges and opportunities for future research in this exciting and growing field that could lead to blood-brain barrier bypassing therapeutic gene editing.

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.

Blood-brain barrier breakdown is linked to tau pathology and neuronal injury in a differential manner according to amyloid deposition

The blood-brain barrier (BBB) breakdown has been suggested as an early marker for Alzheimer's disease (AD); yet the relationship between BBB breakdown and AD-specific biomarkers based on the amyloid/tau/neurodegeneration framework is not clear. This study investigated the relationship between BBB permeability, AD-specific biomarkers, and cognition in patients with cognitive impairment. In this prospective study, we enrolled 62 participants with mild cognitive impairment or dementia between January 2019 and October 2020. All participants were assessed through cognitive tests, amyloid positron emission tomography (PET), dynamic contrast-enhanced magnetic resonance imaging (MRI) for BBB permeability (Ktrans), cerebrospinal fluid studies for Aβ42/40 ratio, phosphorylated-tau Thr181 protein (p-tau), total tau protein (t-tau), and structural MRI for neurodegeneration. In amyloid PET (+) group, higher cortical Ktrans was associated with lower Aβ40 (r = -0.529 p = 0.003), higher Aβ42/40 ratio (r = 0.533, p = 0.003), lower p-tau (r = -0.452, p = 0.014) and lower hippocampal volume (r = -0.438, p = 0.017). In contrast, cortical Ktrans was positively related to t-tau level. (r = 0.489, p = 0.004) in amyloid PET (-) group. Our results suggest that BBB permeability is related to AD-specific biomarkers, but the relationship can vary by the presence of Aβ plaque accumulation.

Blood-spinal cord barrier disruption in degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is the most prevalent cause of spinal cord dysfunction in the aging population. Significant neurological deficits may result from a delayed diagnosis as well as inadequate neurological recovery following surgical decompression. Here, we review the pathophysiology of DCM with an emphasis on how blood-spinal cord barrier (BSCB) disruption is a critical yet neglected pathological feature affecting prognosis. In patients suffering from DCM, compromise of the BSCB is evidenced by elevated cerebrospinal fluid (CSF) to serum protein ratios and abnormal contrast-enhancement upon magnetic resonance imaging (MRI). In animal model correlates, there is histological evidence of increased extravasation of tissue dyes and serum contents, and pathological changes to the neurovascular unit. BSCB dysfunction is the likely culprit for ischemia-reperfusion injury following surgical decompression, which can result in devastating neurological sequelae. As there are currently no therapeutic approaches specifically targeting BSCB reconstitution, we conclude the review by discussing potential interventions harnessed for this purpose.

The neurovascular unit in healthy and injured spinal cord

The neurovascular unit (NVU) reflects the close temporal and spatial link between neurons and blood vessels. However, the understanding of the NVU in the spinal cord is far from clear and largely based on generalized knowledge obtained from the brain. Herein, we review the present knowledge of the NVU and highlight candidate approaches to investigate the NVU, particularly focusing on the spinal cord. Several unique features maintain the highly regulated microenvironment in the NVU. Autoregulation and neurovascular coupling ensure regional blood flow meets the metabolic demand according to the blood supply or local neural activation. The blood-central nervous system barrier partitions the circulating blood from neural parenchyma and facilitates the selective exchange of substances. Furthermore, we discuss spinal cord injury (SCI) as a common injury from the perspective of NVU dysfunction. Hopefully, this review will help expand the understanding of the NVU in the spinal cord and inspire new insights into SCI.

A panel of TDP-43-regulated splicing events verifies loss of TDP-43 function in amyotrophic lateral sclerosis brain tissue

TDP-43 dysfunction is a molecular hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). A major hypothesis of TDP-43 dysfunction in disease is the loss of normal nuclear function, resulting in impaired RNA regulation and the emergence of cryptic exons. Cryptic exons and differential exon usage are emerging as promising markers of lost TDP-43 function in addition to revealing biological pathways involved in neurodegeneration in ALS/FTD. In this brief report, we identified markers of TDP-43 loss of function by depleting TARDBP from post-mortem human brain pericytes, a manipulable in vitro primary human brain cell model, and identifying differential exon usage events with bulk RNA-sequencing analysis. We present these data in an interactive database (https://www.scotterlab.auckland.ac.nz/research-themes/tdp43-lof-db-v2/) together with seven other TDP-43-depletion datasets we meta-analysed previously, for user analysis of differential expression and splicing signatures. Differential exon usage events that were validated by qPCR were then compiled into a 'differential exon usage panel' with other well-established TDP-43 loss-of-function exon markers. This differential exon usage panel was investigated in ALS and control motor cortex tissue to verify whether, and to what extent, TDP-43 loss of function occurs in ALS. We find that profiles of TDP-43-regulated cryptic exons, changed exon usage and changed 3' UTR usage discriminate ALS brain tissue from controls, verifying that TDP-43 loss of function occurs in ALS. We propose that TDP-43-regulated splicing events that occur in brain tissue will have promise as predictors of disease.

Development and repair of blood vessels in the zebrafish spinal cord

The vascular system is inefficiently repaired after spinal cord injury (SCI) in mammals, resulting in secondary tissue damage and immune deregulation that contribute to the limited functional recovery. Unlike mammals, zebrafish can repair the spinal cord (SC) and restore motility, but the vascular response to injury has not been investigated. Here, we describe the zebrafish SC blood vasculature, starting in development with the initial vessel ingression in a body size-dependent manner, the acquisition of perivascular support and the establishment of ventral to dorsal blood circulation. The vascular organization grows in complexity and displays multiple barrier specializations in adulthood. After injury, vessels rapidly regrow into the lesion, preceding the glial bridge and axons. Vascular repair involves an early burst of angiogenesis that creates dysmorphic and leaky vessels. Dysfunctional vessels are later removed, as pericytes are recruited and the blood-SC barrier is re-established. This study demonstrates that zebrafish can successfully re-vascularize the spinal tissue, reinforcing the value of this organism as a regenerative model for SCI.

Spinal Cord Blood Vessels in Aged Mice Show Greater Levels of Hypoxia-Induced Vascular Disruption and Microglial Activation

In response to chronic mild hypoxia (CMH, 8% O2), spinal cord blood vessels launch a robust angiogenic response that is associated with transient disruption of the blood-spinal cord barrier (BSCB) which, in turn, triggers a microglial vasculo-protective response. Because hypoxia occurs in many age-related conditions, the goal of this study was to define how aging influences these responses by comparing events in young (8-10 weeks) and aged (20 months) mice. This revealed that aged mice had much greater (3-4-fold) levels of hypoxic-induced BSCB disruption than young mice and that, while the early stage of the angiogenic response in aged mice was no different to young mice, the maturation of newly formed vessels was significantly delayed. Interestingly, microglia in the spinal cords of aged mice were much more activated than young mice, even under normoxic conditions, and this was further enhanced by CMH, though, surprisingly, this resulted in reduced microglial clustering around leaky blood vessels and diminished vasculo-protection. Vascular disruption was associated with loss of myelin in spinal cord white matter (WM) in both young and aged mice. Furthermore, it was notable that the spinal cord of aged mice contained a lower density of Olig2+ oligodendroglial cells even under normoxic conditions and that CMH significantly reduced the density of Olig2+ cells in spinal cord WM of the aged, but not the young, mice. These results demonstrate that spinal cord blood vessels of aged mice are much more vulnerable to the damaging effects of hypoxia than young mice, in part due to the reduced vasculo-protection conferred by chronically activated microglial cells. These observations may have implications for the pathogenesis and/or treatment of spinal cord diseases such as amyotrophic lateral sclerosis (ALS) and suggest that an improvement in microglial function could offer therapeutic potential for treating these age-related conditions.

Pathological hemodynamic changes and leukocyte transmigration disrupt the blood-spinal cord barrier after spinal cord injury

BACKGROUND

Blood-spinal cord barrier (BSCB) disruption is a key event after spinal cord injury (SCI), which permits unfavorable blood-derived substances to enter the neural tissue and exacerbates secondary injury. However, limited mechanical impact is usually followed by a large-scale BSCB disruption in SCI. How the BSCB disruption is propagated along the spinal cord in the acute period of SCI remains unclear. Thus, strategies for appropriate clinical treatment are lacking.

METHODS

A SCI contusion mouse model was established in wild-type and LysM-YFP transgenic mice. In vivo two-photon imaging and complementary studies, including immunostaining, capillary western blotting, and whole-tissue clearing, were performed to monitor BSCB disruption and verify relevant injury mechanisms. Clinically applied target temperature management (TTM) to reduce the core body temperature was tested for the efficacy of attenuating BSCB disruption.

RESULTS

Barrier leakage was detected in the contusion epicenter within several minutes and then gradually spread to more distant regions. Membrane expression of the main tight junction proteins remained unaltered at four hours post-injury. Many junctional gaps emerged in paracellular tight junctions at the small vessels from multiple spinal cord segments at 15 min post-injury. A previously unnoticed pathological hemodynamic change was observed in the venous system, which likely facilitated gap formation and barrier leakage by exerting abnormal physical force on the BSCB. Leukocytes were quickly initiated to transverse through the BSCB within 30 min post-SCI, actively facilitating gap formation and barrier leakage. Inducing leukocyte transmigration generated gap formation and barrier leakage. Furthermore, pharmacological alleviation of pathological hemodynamic changes or leukocyte transmigration reduced gap formation and barrier leakage. TTM had very little protective effects on the BSCB in the early period of SCI other than partially alleviating leukocyte infiltration.

CONCLUSIONS

Our data show that BSCB disruption in the early period of SCI is a secondary change, which is indicated by widespread gap formation in tight junctions. Pathological hemodynamic changes and leukocyte transmigration contribute to gap formation, which could advance our understanding of BSCB disruption and provide new clues for potential treatment strategies. Ultimately, TTM is inadequate to protect the BSCB in early SCI.

Edema after CNS Trauma: A Focus on Spinal Cord Injury

Edema after spinal cord injury (SCI) is one of the first observations after the primary injury and lasts for few days after trauma. It has serious consequences on the affected tissue and can aggravate the initial devastating condition. To date, the mechanisms of the water content increase after SCI are not fully understood. Edema formation results in a combination of interdependent factors related to mechanical damage after the initial trauma progressing, along with the subacute and acute phases of the secondary lesion. These factors include mechanical disruption and subsequent inflammatory permeabilization of the blood spinal cord barrier, increase in the capillary permeability, deregulation in the hydrostatic pressure, electrolyte-imbalanced membranes and water uptake in the cells. Previous research has attempted to characterize edema formation by focusing mainly on brain swelling. The purpose of this review is to summarize the current understanding of the differences in edema formation in the spinal cord and brain, and to highlight the importance of elucidating the specific mechanisms of edema formation after SCI. Additionally, it outlines findings on the spatiotemporal evolution of edema after spinal cord lesion and provides a general overview of prospective treatment strategies by focusing on insights to prevent edema formation after SCI.

The Active Role of Pericytes During Neuroinflammation in the Adult Brain

Microvessels in the central nervous system (CNS) have one of the highest populations of pericytes, indicating their crucial role in maintaining homeostasis. Pericytes are heterogeneous cells located around brain microvessels; they present three different morphologies along the CNS vascular tree: ensheathing, mesh, and thin-strand pericytes. At the arteriole-capillary transition ensheathing pericytes are found, while mesh and thin-strand pericytes are located at capillary beds. Brain pericytes are essential for the establishment and maintenance of the blood-brain barrier, which restricts the passage of soluble and potentially toxic molecules from the circulatory system to the brain parenchyma. Pericytes play a key role in regulating local inflammation at the CNS. Pericytes can respond differentially, depending on the degree of inflammation, by secreting a set of neurotrophic factors to promote cell survival and regeneration, or by potentiating inflammation through the release of inflammatory mediators (e.g., cytokines and chemokines), and the overexpression of cell adhesion molecules. Under inflammatory conditions, pericytes may regulate immune cell trafficking to the CNS and play a role in perpetuating local inflammation. In this review, we describe pericyte responses during acute and chronic neuroinflammation.

Brain and spinal cord arteriolosclerosis and its associations with cerebrovascular disease risk factors in community-dwelling older adults

Arteriolosclerosis is common in older brains and related to cognitive and motor impairment. We compared the severity of arteriolosclerosis and its associations with cerebrovascular disease risk factors (CVD-RFs) in multiple locations in the brain and spinal cord. Participants (n = 390) were recruited in the context of a longitudinal community-based clinical-pathological study, the Rush Memory and Aging Project. CVD-RFs were assessed annually for an average of 8.7 (SD = 4.3) years before death. The annual assessments included systolic (SBP) and diastolic (DBP) blood pressure, diabetes mellitus (DM), low- and high-density lipoprotein cholesterol, triglyceride, body mass index, and smoking. Postmortem pathological assessments included assessment of arteriolosclerosis severity using the same rating scale in three brain locations (basal ganglia, frontal, and parietal white matter regions) and four spinal cord levels (cervical, thoracic, lumbar and sacral levels). A single measure was used to summarize the severity of spinal arteriolosclerosis assessments at the four levels due to their high correlations. Average age at death was 91.5 (SD = 6.2) years, and 73% were women. Half showed arteriolosclerosis in frontal white matter and spinal cord followed by parietal white matter (38%) and basal ganglia (27%). The severity of arteriolosclerosis in all three brain locations showed mild-to-moderate correlations. By contrast, spinal arteriolosclerosis was associated with brain arteriolosclerosis only in frontal white matter. Higher DBP was associated with more severe arteriolosclerosis in all three brain locations. DM was associated with more severe arteriolosclerosis only in frontal white matter. Controlling for DBP, higher SBP was inversely associated with arteriolosclerosis in parietal white matter. Blood cholesterol and triglyceride, high body mass index, or smoking were not related to the severity of arteriolosclerosis in any brain region. None of the CVD-RFs were associated with the severity of spinal arteriolosclerosis. These data indicate that severity of arteriolosclerosis and its associations with CVD-RFs may vary in different CNS locations.

Perivascular PDGFRB+ cells accompany lesion formation and clinical evolution differentially in two different EAE models

BACKGROUND

Multiple Sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that may lead to progressive disability. Here, we explored the behavioral pattern and the role of vasculature especially PDGFRB+ pericytes/ perivascular cells, in MS pathogenesis.

METHODS

We have evaluated vascular changes in two different experimental allergic encephalomyelitis (EAE) mice models (MOG and PLP-induced). PDGFRB+ cells demonstrated distinct and different behavioral patterns. In both models, fibrosis formation was detected via collagen, fibronectin, and extracellular matrix accumulation.

RESULTS

The PLP-induced animal model revealed that fibrosis predominantly occurs in perivascular locations and that PDGFRB+ cells are accumulated around vessels. Also, the expression of fibrotic genes and genes coding extracellular matrix (ECM) proteins are upregulated. Moreover, the perivascular thick wall structures in affected vessels of this model presented primarily increased PDGFRB+ cells but not NG2+ cells in the transgenic NG2-DsRed transgenic animal model. On the other hand, in MOG induced model, PDGFRB+ perivascular cells were accumulated at the lesion sites. PDGFRB+ cells colocalized with ECM proteins (collagen, fibronectin, and lysyl oxidase L3). Nevertheless, both MOG and PLP-immunized mice showed increasing EAE severity, and disability parallel with enhanced perivascular cell accumulation as the disease progressed from earlier (day 15) to later (day 40).

CONCLUSION

As a result, we have concluded that PDGFRB+ perivascular cells may be participating in lesion progression and as well as demonstrating different responses in different EAE models.

Antibody-oligonucleotide conjugate achieves CNS delivery in animal models for spinal muscular atrophy

Antisense oligonucleotides (ASOs) have emerged as one of the most innovative new genetic drug modalities. However, their high molecular weight limits their bioavailability for otherwise-treatable neurological disorders. We investigated conjugation of ASOs to an antibody against the murine transferrin receptor, 8D3130, and evaluated it via systemic administration in mouse models of the neurodegenerative disease spinal muscular atrophy (SMA). SMA, like several other neurological and neuromuscular diseases, is treatable with single-stranded ASOs that modulate splicing of the survival motor neuron 2 (SMN2) gene. Administration of 8D3130-ASO conjugate resulted in elevated levels of bioavailability to the brain. Additionally, 8D3130-ASO yielded therapeutic levels of SMN2 splicing in the central nervous system of adult human SMN2-transgenic (hSMN2-transgenic) mice, which resulted in extended survival of a severely affected SMA mouse model. Systemic delivery of nucleic acid therapies with brain-targeting antibodies offers powerful translational potential for future treatments of neuromuscular and neurodegenerative diseases.

Blood-Brain Barrier Disruption and Its Involvement in Neurodevelopmental and Neurodegenerative Disorders

The blood-brain barrier (BBB) is a highly specialized and dynamic compartment which regulates the uptake of molecules and solutes from the blood. The relevance of the maintenance of a healthy BBB underpinning disease prevention as well as the main pathomechanisms affecting BBB function will be detailed in this review. Barrier disruption is a common aspect in both neurodegenerative diseases, such as amyotrophic lateral sclerosis, and neurodevelopmental diseases, including autism spectrum disorders. Throughout this review, conditions altering the BBB during the earliest and latest stages of life will be discussed, revealing common factors involved. Due to the barrier's role in protecting the brain from exogenous components and xenobiotics, drug delivery across the BBB is challenging. Potential therapies based on the BBB properties as molecular Trojan horses, among others, will be reviewed, as well as innovative treatments such as stem cell therapies. Additionally, due to the microbiome influence on the normal function of the brain, microflora modulation strategies will be discussed. Finally, future research directions are highlighted to address the current gaps in the literature, emphasizing the idea that common therapies for both neurodevelopmental and neurodegenerative pathologies exist.

Key brain cell interactions and contributions to the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide, with the two major hallmarks being the deposition of extracellular β-amyloid (Aβ) plaques and of intracellular neurofibrillary tangles (NFTs). Additionally, early pathological events such as cerebrovascular alterations, a compromised blood-brain barrier (BBB) integrity, neuroinflammation and synaptic dysfunction, culminate in neuron loss and cognitive deficits. AD symptoms reflect a loss of neuronal circuit integrity in the brain; however, neurons do not operate in isolation. An exclusively neurocentric approach is insufficient to understand this disease, and the contribution of other brain cells including astrocytes, microglia, and vascular cells must be integrated in the context. The delicate balance of interactions between these cells, required for healthy brain function, is disrupted during disease. To design successful therapies, it is critical to understand the complex brain cellular connections in AD and the temporal sequence of their disturbance. In this review, we discuss the interactions between different brain cells, from physiological conditions to their pathological reactions in AD, and how this basic knowledge can be crucial for developing new therapeutic strategies.

Moderate systemic therapeutic hypothermia is insufficient to protect blood-spinal cord barrier in spinal cord injury

Blood–spinal cord barrier (BSCB) disruption is a pivotal event in spinal cord injury (SCI) that aggravates secondary injury but has no specific treatment. Previous reports have shown that systemic therapeutic hypothermia (TH) can protect the blood–brain barrier after brain injury. To verify whether a similar effect exists on the BSCB after SCI, moderate systemic TH at 32°C was induced for 4 h on the mice with contusion-SCI. In vivo two-photon microscopy was utilized to dynamically monitor the BSCB leakage 1 h after SCI, combined with immunohistochemistry to detect BSCB leakage at 1 and 4 h after SCI. The BSCB leakage was not different between the normothermia (NT) and TH groups at both the in vivo and postmortem levels. The expression of endothelial tight junctions was not significantly different between the NT and TH groups 4 h after SCI, as detected by capillary western blotting. The structural damage of the BSCB was examined with immunofluorescence, but the occurrence of junctional gaps was not changed by TH 4 h after SCI. Our results have shown that moderate systemic TH induced for 4 h does not have a protective effect on the disrupted BSCB in early SCI. This treatment method has a low value and is not recommended for BSCB disruption therapy in early SCI.

Dysfunction of the neurovascular unit in brain aging

An emerging concept termed the neurovascular unit (NVU) underlines neurovascular coupling. It has been reported that NVU impairment can result in neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Aging is a complex and irreversible process caused by programmed and damage-related factors. Loss of biological functions and increased susceptibility to additional neurodegenerative diseases are major characteristics of aging. In this review, we describe the basics of the NVU and discuss the effect of aging on NVU basics. Furthermore, we summarize the mechanisms that increase NVU susceptibility to neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Finally, we discuss new treatments for neurodegenerative diseases and methods of maintaining an intact NVU that may delay or diminish aging.

The role of extracellular matrix alterations in mediating astrocyte damage and pericyte dysfunction in Alzheimer's disease: A comprehensive review

The brain is a highly vascularized tissue protected by the blood-brain barrier (BBB), a complex structure allowing only necessary substances to pass through into the brain while limiting the entrance of harmful toxins. The BBB comprises several components, and the most prominent features are tight junctions between endothelial cells (ECs), which are further wrapped in a layer of pericytes. Pericytes are multitasked cells embedded in a thick basement membrane (BM) that consists of a fibrous extracellular matrix (ECM) and are surrounded by astrocytic endfeet. The primary function of astrocytes and pericytes is to provide essential blood supply and vital nutrients to the brain. In Alzheimer's disease (AD), long-term neuroinflammatory cascades associated with infiltration of harmful neurotoxic proteins may lead to BBB dysfunction and altered ECM components resulting in brain homeostatic imbalance, synaptic damage, and declined cognitive functions. Moreover, BBB structure and functional integrity may be lost due to induced ECM alterations, astrocyte damage, and pericytes dysfunction, leading to amyloid-beta (Aβ) hallmarks deposition in different brain regions. Herein, we highlight how BBB, ECM, astrocytes, and pericytes dysfunction can play a leading role in AD's pathogenesis and discuss their impact on brain functions.

Maternal immune activation leads to defective brain-blood vessels and intracerebral hemorrhages in male offspring

Intracerebral hemorrhages are recognized risk factors for neurodevelopmental disorders and represent early biomarkers for cognitive dysfunction and mental disability, but the pathways leading to their occurrence are not well defined. We report that a single intrauterine exposure of the immunostimulant Poly I:C to pregnant mice at gestational day 9, which models a prenatal viral infection and the consequent maternal immune activation, induces the defective formation of brain vessels and causes intracerebral hemorrhagic events, specifically in male offspring. We demonstrate that maternal immune activation promotes the production of the TGF-β1 active form and the consequent enhancement of pSMAD1-5 in males' brain endothelial cells. TGF-β1, in combination with IL-1β, reduces the endothelial expression of CD146 and claudin-5, alters the endothelium-pericyte interplay resulting in low pericyte coverage, and increases hemorrhagic events in the adult offspring. By showing that exposure to Poly I:C at the beginning of fetal cerebral angiogenesis results in sex-specific alterations of brain vessels, we provide a mechanistic framework for the association between intragravidic infections and anomalies of the neural vasculature, which may contribute to neuropsychiatric disorders.

Microglial debris is cleared by astrocytes via C4b-facilitated phagocytosis and degraded via RUBICON-dependent noncanonical autophagy in mice

Microglia are important immune cells in the central nervous system (CNS) that undergo turnover throughout the lifespan. If microglial debris is not removed in a timely manner, accumulated debris may influence CNS function. Clearance of microglial debris is crucial for CNS homeostasis. However, underlying mechanisms remain obscure. We here investigate how dead microglia are removed. We find that although microglia can phagocytose microglial debris in vitro, the territory-dependent competition hinders the microglia-to-microglial debris engulfment in vivo. In contrast, microglial debris is mainly phagocytosed by astrocytes in the brain, facilitated by C4b opsonization. The engulfed microglial fragments are then degraded in astrocytes via RUBICON-dependent LC3-associated phagocytosis (LAP), a form of noncanonical autophagy. Interference with C4b-mediated engulfment and subsequent LAP disrupt the removal and degradation of microglial debris, respectively. Together, we elucidate the cellular and molecular mechanisms of microglial debris removal in mice, extending the knowledge on the maintenance of CNS homeostasis.

CCAAT/Enhancer-Binding Proteins in Fibrosis: Complex Roles Beyond Conventional Understanding

CCAAT/enhancer-binding proteins (C/EBPs) are a family of at least six identified transcription factors that contain a highly conserved basic leucine zipper domain and interact selectively with duplex DNA to regulate target gene expression. C/EBPs play important roles in various physiological processes, and their abnormal function can lead to various diseases. Recently, accumulating evidence has demonstrated that aberrant C/EBP expression or activity is closely associated with the onset and progression of fibrosis in several organs and tissues. During fibrosis, various C/EBPs can exert distinct functions in the same organ, while the same C/EBP can exert distinct functions in different organs. Modulating C/EBP expression or activity could regulate various molecular processes to alleviate fibrosis in multiple organs; therefore, novel C/EBPs-based therapeutic methods for treating fibrosis have attracted considerable attention. In this review, we will explore the features of C/EBPs and their critical functions in fibrosis in order to highlight new avenues for the development of novel therapies targeting C/EBPs.

Elevated Cerebrospinal Fluid Proteins and Albumin Determine a Poor Prognosis for Spinal Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a heterogeneous disease, both in its onset phenotype and in its rate of progression. The aim of this study was to establish whether the dysfunction of the blood–brain barrier (BBB) and blood–spinal cord barrier (BSCB) measured through cerebrospinal fluid (CSF) proteins and the albumin-quotient (QAlb) are related to the speed of disease progression. An amount of 246 patients diagnosed with ALS were included. CSF and serum samples were determined biochemically for different parameters. Survival analysis based on phenotype shows higher probability of death for bulbar phenotype compared to spinal phenotype (p-value: 0.0006). For the effect of CSF proteins, data shows an increased risk of death for spinal ALS patients as the value of CSF proteins increases. The same model replicated for CSF albumin yielded similar results. Statistical models determined that the lowest cut-off value for CSF proteins able to differentiate patients with a good prognosis and worse prognosis corresponds to CSF proteins ≥ 0.5 g/L (p-value: 0.0189). For the CSF albumin, the QAlb ≥0.65 is associated with elevated probability of death (p-value: 0.0073). High levels of QAlb are a bad prognostic indicator for the spinal phenotype, in addition to high CSF proteins levels that also act as a marker of poor prognosis.

The Provenance, Providence, and Position of Endothelial Cells in Injured Spinal Cord Vascular Pathology

Endothelial cells (ECs) and pericytes are present in all blood vessels. Their position confers an important role in controlling oxygen and nutrient transportation to the different organs. ECs can adopt different morphologies based on their need and functions. Both ECs and pericytes express different surface markers that help in their identification, but heterogeneity and overlapping between markers among different cells pose a challenge for their precise identification. Spatiotemporal association of ECs and pericytes have great importance in sprout formation and vessel stabilization. Any traumatic injury in CNS may lead to vascular damage along with neuronal damage. Hence, ECs-pericyte interaction by physical contact and paracrine molecules is crucial in recovering the epicenter region by promoting angiogenesis. ECs can transform into other types of cells through endothelial-mesenchymal transition (EndMT), promoting wound healing in the epicenter region. Various signaling pathways mediate the interaction of ECs with pericytes that have an extensive role in angiogenesis. In this review, we discussed ECs and pericytes surface markers, the spatiotemporal association and interaction of ECs-pericytes, and signaling associated with the pathology of traumatic SCI. Linking the brain or spinal cord-specific pathologies and human vascular pathology will pave the way toward identifying new therapeutic targets and developing innovative preventive strategies. Endothelial-pericyte interaction strategic for formation of functional neo-vessels that are crucial for neurological recovery.

LXR agonist modifies neuronal lipid homeostasis and decreases PGD2 in the dorsal root ganglia in western diet-fed mice

The prevalence of peripheral neuropathy is high in diabetic and overweight populations. Chronic neuropathic pain, a symptom of peripheral neuropathy, is a major disabling symptom that leads to a poor quality of life. Glucose management for diabetic and prediabetic individuals often fail to reduce or improve pain symptoms, therefore, exploring other mechanisms is necessary to identify effective treatments. A large body of evidence suggest that lipid signaling may be a viable target for management of peripheral neuropathy in obese individuals. The nuclear transcription factors, Liver X Receptors (LXR), are known regulators of lipid homeostasis, phospholipid remodeling, and inflammation. Notably, the activation of LXR using the synthetic agonist GW3965, delayed western diet (WD)-induced allodynia in rodents. To further understand the neurobiology underlying the effect of LXR, we used translating ribosome affinity purification and evaluated translatomic changes in the sensory neurons of WD-fed mice treated with the LXR agonist GW3965. We also observed that GW3965 decreased prostaglandin levels and decreased free fatty acid content, while increasing lysophosphatidylcholine, phosphatidylcholine, and cholesterol ester species in the sensory neurons of the dorsal root ganglia (DRG). These data suggest novel downstream interplaying mechanisms that modifies DRG neuronal lipid following GW3965 treatment.

Serum biomarkers of neuroinflammation and blood-brain barrier leakage in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable and rapidly progressive neurological disorder. Biomarkers are critical to understanding disease causation, monitoring disease progression and assessing the efficacy of treatments. However, robust peripheral biomarkers are yet to be identified. Neuroinflammation and breakdown of the blood-brain barrier (BBB) are common to familial and sporadic ALS and may produce a unique biomarker signature in peripheral blood. Using cytometric bead array (n = 15 participants per group (ALS or control)) and proteome profiling (n = 6 participants per group (ALS or control)), we assessed a total of 106 serum cytokines, growth factors, and BBB breakdown markers in the serum of control and ALS participants. Further, primary human brain pericytes, which maintain the BBB, were used as a biosensor of inflammation following pre-treatment with ALS serum. Principal components analysis of all proteome profile data showed no clustering of control or ALS sera, and no individual serum proteins met the threshold for statistical difference between ALS and controls (adjusted P values). However, the 20 most changed proteins between control and ALS sera showed a medium effect size (Cohen’s d = 0.67) and cluster analysis of their levels together identified three sample subsets; control-only, mixed control-ALS, and ALS-only. These 20 proteins were predominantly pro-angiogenic and growth factors, including fractalkine, BDNF, EGF, PDGF, Dkk-1, MIF and angiopoietin-2. S100β, a protein highly concentrated in glial cells and therefore a marker of BBB leakage when found in blood, was unchanged in ALS serum, suggesting that serum protein profiles were reflective of peripheral rather than CNS biofluids. Finally, primary human brain pericytes remained proliferative and their secretome was unchanged by chronic exposure to ALS serum. Our exploratory study suggests that individual serum cytokine levels may not be robust biomarkers in small studies of ALS, but that larger studies using multiplexed analysis of pro-angiogenic and growth factors may identify a peripheral signature of ALS pathogenesis.

The Role of Pericytes in Ischemic Stroke: Fom Cellular Functions to Therapeutic Targets

Ischemic stroke (IS) is a cerebrovascular disease causing high rates of disability and fatality. In recent years, the concept of the neurovascular unit (NVU) has been accepted by an increasing number of researchers and is expected to become a new paradigm for exploring the pathogenesis and treatment of IS. NVUs are composed of neurons, endothelial cells, pericytes, astrocytes, microglia, and the extracellular matrix. As an important part of the NVU, pericytes provide support for other cellular components and perform a variety of functions, including participating in the maintenance of the normal physiological function of the blood–brain barrier, regulating blood flow, and playing a role in inflammation, angiogenesis, and neurogenesis. Therefore, treatment strategies targeting pericyte functions, regulating pericyte epigenetics, and transplanting pericytes warrant exploration. In this review, we describe the reactions of pericytes after IS, summarize the potential therapeutic targets and strategies targeting pericytes for IS, and provide new treatment ideas for ischemic stroke.

The consequence of endothelial remodelling on the blood spinal cord barrier and nociception

Nociception is a fundamental acute protective mechanism that prevents harm to an organism. Understanding the integral processes that control nociceptive processing are fundamental to our appreciation of which cellular and molecular features underlie this process. There is an extensive understanding of how sensory neurons interpret differing sensory modalities and intensities. However, it is widely appreciated that the sensory neurons do not act alone. These work in harmony with inflammatory and vascular systems to modulate pain perception. The spinal cord has an extensive interaction with the capillary network in the form of a blood spinal cord barrier to ensure homeostatic control of the spinal cord neuron milieu. However, there is an extensive appreciation that disturbances in the blood spinal cord barrier contribute to the onset of chronic pain. Enhanced vascular permeability and impaired blood perfusion have both been highlighted as contributors to chronic pain manifestation. Here, we discuss the evidence that demonstrates alterations in the blood spinal cord barrier influences nociceptive processing and perception of pain.

Drug delivery to the central nervous system

Despite the rising global incidence of central nervous system (CNS) disorders, CNS drug development remains challenging, with high costs, long pathways to clinical use and high failure rates. The CNS is highly protected by physiological barriers, in particular, the blood-brain barrier and the blood-cerebrospinal fluid barrier, which limit access of most drugs. Biomaterials can be designed to bypass or traverse these barriers, enabling the controlled delivery of drugs into the CNS. In this Review, we first examine the effects of normal and diseased CNS physiology on drug delivery to the brain and spinal cord. We then discuss CNS drug delivery designs and materials that are administered systemically, directly to the CNS, intranasally or peripherally through intramuscular injections. Finally, we highlight important challenges and opportunities for materials design for drug delivery to the CNS and the anticipated clinical impact of CNS drug delivery.

Trimethylamine N-Oxide (TMAO) drives insulin resistance and cognitive deficiencies in a senescence accelerated mouse model

It has been established that ageing is the major risk factor for cognitive deficiency and it is becoming increasingly evident that insulin resistance is another factor. Biological plausibility for a link between insulin resistance and dementia is relevant for understanding disease etiology, and to form bases for prevention efforts to decrease disease burden. In the present study, peripheral and central insulin resistance was found in SAMP8 mice (aging mouse model) accompanied by cognitive deficiencies. Furthermore, a marked peripheral inflammatory state was observed in SAMP8 mice, followed by neuroinflammation that could be due to a higher cytokine leaking into the brain across an aging-disrupted blood brain barrier. Moreover, aging-induced gut dysbiosis produces higher TMAO that could also contribute to the peripheral and central inflammatory tone as well as to the cognitive deficiencies observed in SAMP8 mice. All those alterations were reversed by DMB, a treatment that decreases TMAO levels. Data obtained from this project suggest that microbial dysbiosis and increased TMAO secretion could be a key link between aging, insulin resistance and dementia. Thus, pharmacological intervention that leads to decreased TMAO levels, such as DMB, could open a new avenue for the future treatment of neurodegenerative diseases.

A single-cell atlas of the normal and malformed human brain vasculature

Cerebrovascular diseases are a leading cause of death and neurologic disability. Further understanding of disease mechanisms and therapeutic strategies requires a deeper knowledge of cerebrovascular cells in humans. We profiled transcriptomes of 181,388 cells to define a cell atlas of the adult human cerebrovasculature, including endothelial cell molecular signatures with arteriovenous segmentation and expanded perivascular cell diversity. By leveraging this reference, we investigated cellular and molecular perturbations in brain arteriovenous malformations, which are a leading cause of stroke in young people, and identified pathologic endothelial transformations with abnormal vascular patterning and the ontology of vascularly derived inflammation. We illustrate the interplay between vascular and immune cells that contributes to brain hemorrhage and catalog opportunities for targeting angiogenic and inflammatory programs in vascular malformations.

Altered Blood-Brain Barrier and Blood-Spinal Cord Barrier Dynamics in Amyotrophic Lateral Sclerosis: Impact on Medication Efficacy and Safety

The access of drugs into the central nervous system (CNS) is regulated by the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB). A large body of evidence supports perturbation of these barriers in neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Modifications to the BBB and BSCB are also reported in amyotrophic lateral sclerosis (ALS), albeit these modifications have received less attention relative to those in other neurodegenerative diseases. Such alterations to the BBB and BSCB have the potential to impact on CNS exposure of drugs in ALS, modulating the effectiveness of drugs intended to reach the brain and the toxicity of drugs that are not intended to reach the brain. Given the clinical importance of these phenomena, this review will summarise reported modifications to the BBB and BSCB in ALS, discuss their impact on CNS drug exposure and suggest further research directions so as to optimise medicine use in people with ALS.

Blood-Brain Barrier Mechanisms in Stroke and Trauma

The brain microenvironment is tightly regulated. The blood-brain barrier (BBB), which is composed of cerebral endothelial cells, astrocytes, and pericytes, plays an important role in maintaining the brain homeostasis by regulating the transport of both beneficial and detrimental substances between circulating blood and brain parenchyma. After brain injury and disease, BBB tightness becomes dysregulated, thus leading to inflammation and secondary brain damage. In this chapter, we overview the fundamental mechanisms of BBB damage and repair after stroke and traumatic brain injury (TBI). Understanding these mechanisms may lead to therapeutic opportunities for brain injury.

Neurovascular dysfunction and vascular amyloid accumulation as early events in Alzheimer's disease

Alzheimer's disease (AD) is clinically characterized by a progressive loss of cognitive functions and short-term memory. AD patients present two distinctive neuropathological lesions: neuritic plaques and neurofibrillary tangles (NFTs), constituted of beta-amyloid peptide (Aβ) and phosphorylated and truncated tau proteins. Aβ deposits around cerebral blood vessels (cerebral amyloid angiopathy, CAA) is a major contributor to vascular dysfunction in AD. Vascular amyloid deposits could be early events in AD due to dysfunction in the neurovascular unit (NVU) and the blood-brain barrier (BBB), deterioration of the gliovascular unit, and/or decrease of cerebral blood flow (CBF). These pathological events can lead to decreased Aβ clearance, facilitate a neuroinflammatory environment as well as synaptic dysfunction and, finally, lead to neurodegeneration. Here, we review the histopathological AD hallmarks and discuss the two-hit vascular hypothesis of AD, emphasizing the role of neurovascular dysfunction as an early factor that favors vascular Aβ aggregation and neurodegeneration. Addtionally, we emphasize that pericyte degeneration is a key and early element in AD that can trigger amyloid vascular accumulation and NVU/BBB dysfunction. Further research is required to better understand the early pathophysiological mechanisms associated with NVU alteration and CAA to generate early biomarkers and timely treatments for AD.

The pericyte: A critical cell in the pathogenesis of CADASIL

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CADASIL is the most common hereditary small vessel disease presenting with strokes and subcortical vascular dementia caused by mutations in the NOTCH3 gene.

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CADASIL is a vasculopathy primarily involving vascular smooth-muscle cells.

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Arteriolar and capillary pericyte damage or deficiency is a key feature in disease pathogenesis.

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Pericyte-mediated cerebral venous insufficiency may explain white matter lesions and increased perivascular spaces.

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Central role of the pericyte offers novel approaches to the treatment of CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small vessel disease presenting with migraine, mood and cognitive disorders, focal neurological deficits, recurrent ischemic attacks, lacunar infarcts and brain white matter changes. As they age, CADASIL patients invariably develop cognitive impairment and subcortical dementia. CADASIL is caused by missense mutations in the NOTCH3 gene resulting in a profound cerebral vasculopathy affecting primarily arterial vascular smooth muscle cells, which target the microcirculation and perfusion. Based on a thorough review of morphological lesions in arteries, veins, and capillaries in CADASIL, we surmise that arteriolar and capillary pericyte damage or deficiency appears a key feature in the pathogenesis of the disease. This may affect critical pericyte-endothelial interactions causing stroke injury and vasomotor disturbances. Changes in microvascular permeability due to perhaps localized blood-brain barrier alterations and pericyte secretory dysfunction likely contribute to delayed neuronal as well as glial cell death. Moreover, pericyte-mediated cerebral venous insufficiency may explain white matter lesions and the dilatation of Virchow-Robin perivascular spaces typical of CADASIL. The postulated central role of the pericyte offers some novel approaches to the study and treatment of CADASIL and enable elucidation of other forms of cerebral small vessel diseases and subcortical vascular dementia.

Blood-Spinal Cord Barrier: Its Role in Spinal Disorders and Emerging Therapeutic Strategies

The blood-spinal cord barrier (BSCB) has been long thought of as a functional equivalent to the blood-brain barrier (BBB), restricting blood flow into the spinal cord. The spinal cord is supported by various disc tissues that provide agility and has different local immune responses compared to the brain. Though physiologically, structural components of the BSCB and BBB share many similarities, the clinical landscape significantly differs. Thus, it is crucial to understand the composition of BSCB and also to establish the cause–effect relationship with aberrations and spinal cord dysfunctions. Here, we provide a descriptive analysis of the anatomy, current techniques to assess the impairment of BSCB, associated risk factors and impact of spinal disorders such as spinal cord injury (SCI), amyotrophic lateral sclerosis (ALS), peripheral nerve injury (PNI), ischemia reperfusion injury (IRI), degenerative cervical myelopathy (DCM), multiple sclerosis (MS), spinal cavernous malformations (SCM) and cancer on BSCB dysfunction. Along with diagnostic and mechanistic analyses, we also provide an up-to-date account of available therapeutic options for BSCB repair. We emphasize the need to address BSCB as an individual entity and direct future research towards it.

The role of mural cells in hemorrhage of brain arteriovenous malformation

Brain arteriovenous malformation (bAVM) is the most common cause of intracranial hemorrhage (ICH), particularly in young patients. However, the exact cause of bAVM bleeding and rupture is not yet fully understood. In bAVMs, blood bypasses the entire capillary bed and directly flows from arteries to veins. The vessel walls in bAVMs have structural defects, which impair vascular integrity. Mural cells are essential structural and functional components of blood vessels and play a critical role in maintaining vascular integrity. Changes in mural cell number and coverage have been implicated in bAVMs. In this review, we discussed the roles of mural cells in bAVM pathogenesis. We focused on 1) the recent advances in human and animal studies of bAVMs; 2) the importance of mural cells in vascular integrity; 3) the regulatory signaling pathways that regulate mural cell function. More specifically, the platelet-derived growth factor-B (PDGF-B)/PDGF receptor-β (PDGFR-β), EphrinB2/EphB4, and angiopoietins/tie2 signaling pathways that regulate mural cell-recruitment during vascular remodeling were discussed in detail.

Beneficial Effects of Transplanted Human Bone Marrow Endothelial Progenitors on Functional and Cellular Components of Blood-Spinal Cord Barrier in ALS Mice

Convincing evidence of blood-spinal cord barrier (BSCB) alterations has been demonstrated in amyotrophic lateral sclerosis (ALS) and barrier repair is imperative to prevent motor neuron dysfunction. We showed benefits of human bone marrow-derived CD34+ cells (hBM34+) and endothelial progenitor cells (hBM-EPCs) intravenous transplantation into symptomatic G93A SOD1 mutant mice on barrier reparative processes. These gains likely occurred by replacement of damaged endothelial cells, prolonging motor neuron survival. However, additional investigations are needed to confirm the effects of administered cells on integrity of the microvascular endothelium. The aim of this study was to determine tight junction protein levels, capillary pericyte coverage, microvascular basement membrane, and endothelial filamentous actin (F-actin) status in spinal cord capillaries of G93A SOD1 mutant mice treated with human bone marrow-derived stem cells. Tight junction proteins were detected in the spinal cords of cell-treated versus non-treated mice via Western blotting at four weeks after transplant. Capillary pericyte, basement membrane laminin, and endothelial F-actin magnitudes were determined in cervical/lumbar spinal cord tissues in ALS mice, including controls, by immunohistochemistry and fluorescent staining. Results showed that cell-treated versus media-treated ALS mice substantially increased tight junction protein levels, capillary pericyte coverage, basement membrane laminin immunoexpressions, and endothelial cytoskeletal F-actin fluorescent expressions. The greatest benefits were detected in mice receiving hBM-EPCs versus hBM34+ cells. These study results support treatment with a specific cell type derived from human bone marrow toward BSCB repair in ALS. Thus, hBM-EPCs may be advanced for clinical applications as a cell-specific approach for ALS therapy through restored barrier integrity.

Blood-spinal cord barrier leakage is independent of motor neuron pathology in ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving progressive degeneration of upper and lower motor neurons. The pattern of lower motor neuron loss along the spinal cord follows the pattern of deposition of phosphorylated TDP-43 aggregates. The blood-spinal cord barrier (BSCB) restricts entry into the spinal cord parenchyma of blood components that can promote motor neuron degeneration, but in ALS there is evidence for barrier breakdown. Here we sought to quantify BSCB breakdown along the spinal cord axis, to determine whether BSCB breakdown displays the same patterning as motor neuron loss and TDP-43 proteinopathy. Cerebrospinal fluid hemoglobin was measured in living ALS patients (n = 87 control, n = 236 ALS) as a potential biomarker of BSCB and blood–brain barrier leakage. Cervical, thoracic, and lumbar post-mortem spinal cord tissue (n = 5 control, n = 13 ALS) were then immunolabelled and semi-automated imaging and analysis performed to quantify hemoglobin leakage, lower motor neuron loss, and phosphorylated TDP-43 inclusion load. Hemoglobin leakage was observed along the whole ALS spinal cord axis and was most severe in the dorsal gray and white matter in the thoracic spinal cord. In contrast, motor neuron loss and TDP-43 proteinopathy were seen at all three levels of the ALS spinal cord, with most abundant TDP-43 deposition in the anterior gray matter of the cervical and lumbar cord. Our data show that leakage of the BSCB occurs during life, but at end-stage disease the regions with most severe BSCB damage are not those where TDP-43 accumulation is most abundant. This suggests BSCB leakage and TDP-43 pathology are independent pathologies in ALS.