Ligation of the jugular veins does not result in brain inflammation or demyelination in mice

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

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

Flow volume measurement of arterial venous and cerebrospinal fluid in patients with multiple sclerosis

Background Multiple sclerosis (MS) is usually described as an autoimmune disease, although the exact mechanism of the disease remains unknown. There have been studies reporting that venous flow abnormalities may be involved in the pathogenesis of MS or many of the associated clinical manifestations.

Objective The aim of this study was to evaluate flow volumes of the middle cerebral artery (MCA), transverse sinus (TS), and cerebral aqueduct using phase contrast magnetic resonance imaging (PC-MRI) in relapsing-remitting MS patients and a control group.

Methods We included 34 patients diagnosed by the McDonald criteria, revised in 2017, as well as 15 healthy controls matched by age and sex. The MRI scans were performed using a 1.5-T superconducting scanner. Axial T1-weighted, T2-weighted, and PC-MRI sequences were performed for the quantitative investigation of flow volume measurements. Quantitative analyses of flows were performed using flow analyses program PC-MRI angiography software. A circular region of interest was placed manually into the cerebral aqueduct, bilateral MCA, and TS.

Results Flow volumes of the cerebral aqueduct and MCA were not statistically significant between the MS and control groups. The flow volumes of the TS for the patient group were lower than those of the control group, and this difference was statistically significant.

Conclusions A reduced TS flow volume in MS patients was noted in the present study when compared with the control group, suggesting a relation between venous pathologies and MS. Further studies are needed to understand whether this relation is causal or epiphenomenal.

JEV Infection Induces M-MDSC Differentiation Into CD3+ Macrophages in the Brain

Japanese encephalitis virus (JEV) is one of the most important members of the flavivirus family. It is a typical zoonotic pathogen that has caused substantial social and economic losses worldwide. The relation between JEV-induced immunosuppression and inflammatory responses has not been thoroughly investigated. In this study, cells infiltrating the brain tissue of JEV-infected mice were mainly identified as monocytic myeloid-derived suppressor cells (M-MDSCs), which subsequently differentiated into CD3⁺ macrophages. Co-culture with T cells showed that both splenic M-MDSCs and brain infiltrated M-MDSCs isolated from JEV-infected mice inhibited T cell proliferation through ARG1 and iNOS. The splenectomy model revealed that JEV-induced M-MDSCs were mainly derived from bone marrow and migrated to the spleen and central nervous system (CNS). The results of the transcriptome analysis and IRF7-deficient mice indicated that the ZBP1-IRF7 signaling pathway stimulated by JEV RNA played a central role in the induction of M-MDSCs. M-MDSCs migrated into the CNS through the chemokine CCL2/N-CCL2 derived from astrocytes and brain infiltrated M-MDSCs differentiated into CD3⁺ macrophages through a mechanism mediated by M-CSF, IL-6 and IFN-γ in the brain microenvironment. These findings provide evidence for the mechanism that JEV regulates the differentiation of M-MDSCs and thereby exacerbates pathogenicity, which represents a potential therapeutic target for Japanese encephalitis (JE).

A Novel Mouse Model for Cerebral Venous Sinus Thrombosis

Cerebral venous sinus thrombosis (CVST) is an uncommon cause of stroke resulting in parenchymal injuries associated with heterogeneous clinical symptoms and prognosis. Therefore, an experimental animal model is required to further study underlying mechanisms involved in CVST. This study is aimed at developing a novel murine model suitable and relevant for evaluating injury patterns during CVST and studying its clinical aspects. CVST was achieved in C57BL/6J mice by autologous clot injection into the superior sagittal sinus (SSS) combined with bilateral ligation of external jugular veins. Clot was prepared ex vivo using thrombin before injection. On days 1 and 7 after CVST, SSS occlusion and associated-parenchymal lesions were monitored using different modalities: in vivo real-time intravital microscopy, magnetic resonance imaging (MRI), and immuno-histology. In addition, mice were subjected to a neurological sensory-motor evaluation. Thrombin-induced clot provided fibrin- and erythrocyte-rich thrombi that lead to reproducible SSS occlusion at day 1 after CVST induction. On day 7 post-CVST, venous occlusion monitoring (MRI, intravital microscopy) showed that initial injected-thrombus size did not significantly change demonstrating no early spontaneous recanalization. Microscopic histological analysis revealed that SSS occlusion resulted in brain edema, extensive fibrin-rich venular thrombotic occlusion, and ischemic and hemorrhagic lesions. Mice with CVST showed a significant lower neurological score on post-operative days 1 and 7, compared to the sham-operated group. We established a novel clinically CVST-relevant model with a persistent and reproducible SSS occlusion responsible for symptomatic ischemic and hemorrhagic lesions. This method provides a reliable model to study CVST physiopathology and evaluation of therapeutic new regimens.

Multiple sclerosis is a systemic venous vasculopathy: A single unifying mechanism

Multiple sclerosis (MS) is a potentially debilitating disease affecting the central nervous system (CNS) clinically characterized by progressive neurological deterioration. It is the most common condition under the umbrella of demyelinating disease, thought to occur as a result of a primary autoimmune insult. Various genetic and environmental risk factors have been implicated as potential triggers and/or predisposing factors; however, the exact mechanism of disease remains elusive. Diagnosis and management are based on clinical presentation, with adjunct imaging and biochemical assessment. Since the 19th century anatomical distribution of lesions in MS have been observed to demonstrate a characteristic periventricular, perivenular distribution; spinal cord and cortical lesions also demonstrate this perivenous preponderance. Venous abnormalities have long been observed on pathology characterized by irregular narrowing and dilatation with associated venous wall and perivenous infiltrates. Active CNS lesions are characterized by perivenular inflammatory infiltrates. There is accompanying global dysfunction of the blood-brain barrier, even within normal appearing tissue, with low levels of inflammatory change and tissue injury seen at pathology. Although several CNS antigens have been identified as potential candidates, including myelin related antigens, a specific pathogenic antigen remains elusive. Evaluation of the cerebrospinal fluid reveals characteristic oligoclonal bands, indicating a broad inflammatory response against a variety of CNS antigens. Antibodies have been identified against endothelial elements in sera of patients with MS, their role is not yet clearly elucidated. Emerging evidence suggests there may be a more systemic inflammatory process, heralded by a systemic preclinical prodrome. In light of such seemingly-discrepant clinical, anatomic, immunologic and pathologic findings we propose a unifying theory; specifically we propose that MS is a primary autoimmune vasculopathy, with a predilection of CNS venous structures. Characteristic CNS lesions are a secondary manifestation resulting from an inflammatory response to the uncovering of usually privileged CNS antigens.

Blood-brain Barrier Disruption May Contribute to White Matter Lesions in the Setting of Internal Jugular Venous Stenosis

BACKGROUND AND PURPOSE

Cloudy white matter lesions are associated imaging features of internal jugular venous stenosis (IJVS). However, the mechanism of the IJVS associated cloudy white matter lesions is still unclear. This study aims to evaluate blood-brain barrier integrity of the patients with IJVS.

MATERIALS AND METHODS

A total of 45 eligible patients with IJVS confirmed by computed tomography venography (CTV) and 45 healthy controls were enrolled into this study. The levels of serum MMP-9 and the markers of tight junctions, including occludin and ZO-1 obtained from IJVS patients and control group were tested by enzyme-linked immune-sorbent assay and compared.

RESULTS

Both the levels of serum MMP-9 (0.2ng/ml) and occludin (0.05ng/ml) in IJVS group were higher than in the control group (0.01ng/ml vs. 0 ng/ml, all p<0.001). While, the levels of serum ZO-1 showed no statistical significance between the two groups (0.55ng/ml vs 0.735ng/ml, P=0.34). The levels of serum MMP-9 between the subset with or without white matter lesions in IJVS group showed a significant difference (0.22 [0.06, 0.43] vs. 0.01 [0.01, 0.06], P =0.019).

CONCLUSION

BBB disruption may participate in the formation of IJVS-associated white matter lesions; the mechanism of BBB disruption may involve MMP-9 and occludin.

Mouse models of neurodegenerative disease: preclinical imaging and neurovascular component

Neurodegenerative diseases represent great challenges for basic science and clinical medicine because of their prevalence, pathologies, lack of mechanism-based treatments, and impacts on individuals. Translational research might contribute to the study of neurodegenerative diseases. The mouse has become a key model for studying disease mechanisms that might recapitulate in part some aspects of the corresponding human diseases. Neurodegenerative disorders are very complicated and multifactorial. This has to be taken in account when testing drugs. Most of the drugs screening in mice are very difficult to be interpretated and often useless. Mouse models could be condiderated a 'pathway models', rather than as models for the whole complicated construct that makes a human disease. Non-invasive in vivo imaging in mice has gained increasing interest in preclinical research in the last years thanks to the availability of high-resolution single-photon emission computed tomography (SPECT), positron emission tomography (PET), high field Magnetic resonance, Optical Imaging scanners and of highly specific contrast agents. Behavioral test are useful tool to characterize different animal models of neurodegenerative pathology. Furthermore, many authors have observed vascular pathological features associated to the different neurodegenerative disorders. Aim of this review is to focus on the different existing animal models of neurodegenerative disorders, describe behavioral tests and preclinical imaging techniques used for diagnose and describe the vascular pathological features associated to these diseases.

Original Research: Feasibility and safety of two surgical techniques for the development of an animal model of jugular vein occlusion

To date, no studies have explored the effect of abnormal cerebral venous circulation on brain disorders, whereas many studies have investigated neurodegenerative brain anomalies associated with arterial diseases. The aim of our study was to demonstrate the feasibility of different surgical techniques to induce venous obstruction of cerebral brain drainage. Six C57/black mice underwent bilateral occlusion of the external jugular vein (group EJV), six underwent bilateral occlusion of the internal jugular vein (group IJV), and six underwent bilateral occlusion of both the EJV and the IJV (group EJV/IJV). Within each group, the interruption of blood flow was obtained via monopolar electro-coagulation (ME) in three mice and via surgical ligation (SL) in the remaining three mice. A "sham group" of two mice was used as the control. High-frequency ultrasound (HFUS) was used to detect the absence of blood flow in the examined vessel. The ME procedure led to successful results in two of nine (22%) mice, one in the EJV group, one in the EJV/IJV group, and zero in the IJV group, and 4 of 18 (22%) mice when considering individual veins (i.e., total number of EJVs and IJVs occluded). The SL procedure was successful in two of three (67%) mice in the EJV group, in three of three (100%) mice in the IJV and in three of four (75%) mice in the EJV/IJV group. Therefore, the overall success rate was 8/10 (80%) when considering mice, and 20/26 (77%) when considering individual veins. The monopolar electro-coagulation method exhibited a high mortality due to cardiorespiratory arrest, while the results of the bilateral surgical ligation of EJVs and IJVs show that it is technically feasible and safe.

Head and Neck Veins of the Mouse. A Magnetic Resonance, Micro Computed Tomography and High Frequency Color Doppler Ultrasound Study

To characterize the anatomy of the venous outflow of the mouse brain using different imaging techniques. Ten C57/black male mice (age range: 7-8 weeks) were imaged with high-frequency Ultrasound, Magnetic Resonance Angiography and ex-vivo Microcomputed tomography of the head and neck. Under general anesthesia, Ultrasound of neck veins was performed with a 20MHz transducer; head and neck Magnetic Resonance Angiography data were collected on 9.4T or 7T scanners, and ex-vivo Microcomputed tomography angiography was obtained by filling the vessels with a radiopaque inert silicone rubber compound. All procedures were approved by the local ethical committee. The dorsal intracranial venous system is quite similar in mice and humans. Instead, the mouse Internal Jugular Veins are tiny vessels receiving the sigmoid sinuses and tributaries from cerebellum, occipital lobe and midbrain, while the majority of the cerebral blood, i.e. from the olfactory bulbs and fronto-parietal lobes, is apparently drained through skull base connections into the External Jugular Vein. Three main intra-extracranial anastomoses, absent in humans, are: 1) the petrosquamous sinus, draining into the posterior facial vein, 2) the veins of the olfactory bulb, draining into the superficial temporal vein through a foramen of the frontal bone 3) the cavernous sinus, draining in the External Jugular Vein through a foramen of the sphenoid bone. The anatomical structure of the mouse cranial venous outflow as depicted by Ultrasound, Microcomputed tomography and Magnetic Resonance Angiography is different from humans, with multiple connections between intra- and extra- cranial veins.

Molecular magnetic resonance imaging of brain-immune interactions

Although the blood-brain barrier (BBB) was thought to protect the brain from the effects of the immune system, immune cells can nevertheless migrate from the blood to the brain, either as a cause or as a consequence of central nervous system (CNS) diseases, thus contributing to their evolution and outcome. Accordingly, as the interface between the CNS and the peripheral immune system, the BBB is critical during neuroinflammatory processes. In particular, endothelial cells are involved in the brain response to systemic or local inflammatory stimuli by regulating the cellular movement between the circulation and the brain parenchyma. While neuropathological conditions differ in etiology and in the way in which the inflammatory response is mounted and resolved, cellular mechanisms of neuroinflammation are probably similar. Accordingly, neuroinflammation is a hallmark and a decisive player of many CNS diseases. Thus, molecular magnetic resonance imaging (MRI) of inflammatory processes is a central theme of research in several neurological disorders focusing on a set of molecules expressed by endothelial cells, such as adhesion molecules (VCAM-1, ICAM-1, P-selectin, E-selectin, …), which emerge as therapeutic targets and biomarkers for neurological diseases. In this review, we will present the most recent advances in the field of preclinical molecular MRI. Moreover, we will discuss the possible translation of molecular MRI to the clinical setting with a particular emphasis on myeloperoxidase imaging, autologous cell tracking, and targeted iron oxide particles (USPIO, MPIO).

Potential involvement of the extracranial venous system in central nervous system disorders and aging

BACKGROUND

The role of the extracranial venous system in the pathology of central nervous system (CNS) disorders and aging is largely unknown. It is acknowledged that the development of the venous system is subject to many variations and that these variations do not necessarily represent pathological findings. The idea has been changing with regards to the extracranial venous system.

DISCUSSION

A range of extracranial venous abnormalities have recently been reported, which could be classified as structural/morphological, hemodynamic/functional and those determined only by the composite criteria and use of multimodal imaging. The presence of these abnormalities usually disrupts normal blood flow and is associated with the development of prominent collateral circulation. The etiology of these abnormalities may be related to embryologic developmental arrest, aging or other comorbidities. Several CNS disorders have been linked to the presence and severity of jugular venous reflux. Another composite criteria-based vascular condition named chronic cerebrospinal venous insufficiency (CCSVI) was recently introduced. CCSVI is characterized by abnormalities of the main extracranial cerebrospinal venous outflow routes that may interfere with normal venous outflow.

SUMMARY

Additional research is needed to better define the role of the extracranial venous system in relation to CNS disorders and aging. The use of endovascular treatment for the correction of these extracranial venous abnormalities should be discouraged, until potential benefit is demonstrated in properly-designed, blinded, randomized and controlled clinical trials.

No evidence for impairment of venous hemodynamics in children or young adults with pediatric-onset multiple sclerosis

BACKGROUND AND PURPOSE

Chronic cerebrospinal venous insufficiency is a postulated etiologic factor for multiple sclerosis, but the higher frequency with longer disease duration and progressive disability suggests that chronic cerebrospinal venous insufficiency is secondary to chronic disease. We evaluated the presence of chronic cerebrospinal venous insufficiency in pediatric-onset MS.

MATERIALS AND METHODS

Twenty-six pediatric patients with MS (18 years of age or younger), 26 age-matched healthy controls, and 13 young adults with pediatric-onset MS underwent sonography of the internal jugular, vertebral, and deep cerebral veins. Five venous hemodynamic criteria were assessed, with 2 criteria required for chronic cerebrospinal venous insufficiency. MR imaging studies, performed in the pediatric patients with MS and healthy control groups, included intracranial 2D time-of-flight MR venography and velocity-sensitive phase-contrast sequences. Contrast-enhanced brain MR images were obtained in pediatric patients with MS to further evaluate venous patency. We used paired t tests, Wilcoxon matched pairs, McNemar tests, and exact conditional logistic regression to estimate the association of chronic cerebrospinal venous insufficiency with MS.

RESULTS

Fifty participants (73.5%) had normal ultrasound findings, 15 (23.1%) met 1 venous hemodynamic criterion, and 2 pediatric patients with MS and 1 young adult with pediatric-onset MS met chronic cerebrospinal venous insufficiency criteria. Chronic cerebrospinal venous insufficiency was not associated with MS (odds ratio, 2.41; 95% CI, 0.19-infinity). Demographic and disease characteristics did not differ between the patients with MS meeting chronic cerebrospinal venous insufficiency criteria (n = 3) and those who did not (n = 36; all, P > .05). The mean (SD) MR imaging measures of intracerebral flow did not differ between the 2 pediatric patients with MS meeting chronic cerebrospinal venous insufficiency criteria (0.85 ± 0.11) and healthy controls (0.87 ± 0.16, P = .50); no child demonstrated venous obstruction.

CONCLUSIONS

Chronic cerebrospinal venous insufficiency is rarely observed in children or young adults with pediatric-onset MS. Venous anatomy and flow rates indicate that venous outflow is intact in pediatric patients with MS. Our findings argue against chronic cerebrospinal venous insufficiency as a component of MS etiology.

Chronic cerebrospinal venous insufficiency is unlikely to be a direct trigger of multiple sclerosis

BACKGROUND

Chronic cerebrospinal venous insufficiency, a vascular pathology affecting the veins draining the central nervous system can accompany multiple sclerosis and is suspected to be involved in its pathogenesis.

OBJECTIVE

This study was aimed at exploring a potential role for chronic cerebrospinal venous insufficiency in triggering multiple sclerosis. If it were venous abnormalities responsible for neurological pathology, one should expect negative correlation, i.e. more severe vascular lesions in the patients with early onset of multiple sclerosis.

METHODS

Localization and degree of venous blockages in 350 multiple sclerosis patients were assessed using catheter venography. Statistical analysis comprised evaluation of the correlations between severity of venous lesions and patients' age at onset of the disease.

RESULTS

We found weak, yet statistically significant positive correlations between patients' age at onset of multiple sclerosis and accumulated and maximal scores of venous lesions. The patients, also those with duration of multiple sclerosis not longer than 5 years, who had their first attack of the disease at younger age, presented with less severe vascular lesions.

CONCLUSION

Positive correlation suggests that venous lesions are not directly triggering multiple sclerosis. There should be another factor that initiates pathological processes in the central nervous system.

CCSVI and MS: no meaning, no fact

A condition called "chronic cerebrospinal venous insufficiency" (CCSVI) has been postulated to play a role in the pathogenesis of multiple sclerosis (MS). This hypothesis implies that a complex pattern of extracranial venous stenosis determines a venous reflux into the brain of MS patients, followed by increased intravenous pressure, blood-brain barrier breakdown and iron deposition into the brain parenchyma, thus triggering a local inflammatory response. In this review, we critically analyze the scientific basis of CCSVI, the current literature on the relationship between CCSVI and MS, as well as the ultrasound methodology that has been claimed to provide evidence of impaired cerebral venous drainage. We show that no piece of the CCSVI theory has a solid supportive scientific evidence. The CCSVI appears to be a rather alien condition and its existence should be definitely questioned. Finally, no proven (i.e., based on strict scientific methodology and on the rules of evidence-based medicine) therapeutic effect of the "liberation" procedure (unblocking the extracranial venous obstruction using angioplasty) has been shown up to date.