Inflammation-induced brain endothelial activation leads to uptake of electrostatically stabilized iron oxide nanoparticles via sulfated glycosaminoglycans.

Based on our previous data on the presence of very small superparamagnetic iron oxide nanoparticles (VSOP) on brain endothelial structures during experimental autoimmune encephalomyelitis (EAE), we investigated the mechanisms of VSOP binding on inflamed brain endothelial cells in vivo and in vitro. After intravenous application, VSOP were detected in brain endothelial cells of EAE animals at peak disease and prior to clinical onset. In vitro, inflammatory stimuli increased VSOP uptake by brain endothelial bEnd.3 cells, which we confirmed in primary endothelial cells and in bEnd.3 cells cultured under shear stress. Transmission electron microscopy and blocking experiments revealed that during inflammation VSOP were endocytosed by bEnd.3. Modified sulfated glycosaminoglycans (GAG) on inflamed brain endothelial cells were the primary binding site for VSOP, as GAG degradation and inhibition of GAG sulfation reduced VSOP uptake. Thus, VSOP-based MRI is sensitive to visualize early neuroinflammatory processes such as GAG modifications on brain endothelial cells.

Structural Hippocampal Damage Following Anti-N-Methyl-D-Aspartate Receptor Encephalitis.

BACKGROUND: The majority of patients with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis suffer from persistent memory impairment despite unremarkable routine clinical magnetic resonance imaging. With improved acute care in these patients, neurocognitive impairment represents the major contributor to long-term morbidity and has thus become a focus of attention. METHODS: Forty patients with anti-NMDAR encephalitis after the acute disease stage and 25 healthy control subjects underwent multimodal structural imaging that combined volumetry of hippocampal subfields with analysis of hippocampal microstructural integrity. Verbal and visuospatial memory performance was assessed in all patients and correlation and mediation analyses were performed to examine associations between hippocampal structural integrity, memory performance, and disease severity. RESULTS: Hippocampal volumes were significantly reduced in patients and hippocampal subfield analysis revealed bilateral atrophy of the input and output regions of the hippocampal circuit. Microstructural integrity was impaired in both hippocampi in patients. Importantly, hippocampal volumetric and microstructural integrity measures correlated with memory performance and disease severity and duration. Mediation analysis revealed that hippocampal microstructure mediated the effect of disease severity on memory performance. CONCLUSIONS: Data from this largest cohort of anti-NMDAR encephalitis patients that underwent extensive multimodal magnetic resonance imaging demonstrate that structural hippocampal damage and associated memory deficits are important long-term sequelae of the encephalitis. Correlation with disease duration and severity highlights the need for rapid diagnosis and adequate immunotherapy to prevent persistent damage to the hippocampus. Advanced imaging protocols may allow a more detailed analysis of structural damage to assess disease progression in clinical routine examinations and for therapy evaluation in prospective trials.

Use of Advanced Magnetic Resonance Imaging Techniques in Neuromyelitis Optica Spectrum Disorder.

Brain parenchymal lesions are frequently observed on conventional magnetic resonance imaging (MRI) scans of patients with neuromyelitis optica (NMO) spectrum disorder, but the specific morphological and temporal patterns distinguishing them unequivocally from lesions caused by other disorders have not been identified. This literature review summarizes the literature on advanced quantitative imaging measures reported for patients with NMO spectrum disorder, including proton MR spectroscopy, diffusion tensor imaging, magnetization transfer imaging, quantitative MR volumetry, and ultrahigh-field strength MRI. It was undertaken to consider the advanced MRI techniques used for patients with NMO by different specialists in the field. Although quantitative measures such as proton MR spectroscopy or magnetization transfer imaging have not reproducibly revealed diffuse brain injury, preliminary data from diffusion-weighted imaging and brain tissue volumetry indicate greater white matter than gray matter degradation. These findings could be confirmed by ultrahigh-field MRI. The use of nonconventional MRI techniques may further our understanding of the pathogenic processes in NMO spectrum disorders and may help us identify the distinct radiographic features corresponding to specific phenotypic manifestations of this disease.

Iron oxide magnetic nanoparticles highlight early involvement of the choroid plexus in central nervous system inflammation.

Neuroinflammation during multiple sclerosis involves immune cell infiltration and disruption of the BBB (blood-brain barrier). Both processes can be visualized by MRI (magnetic resonance imaging), in multiple sclerosis patients and in the animal model EAE (experimental autoimmune encephalomyelitis). We previously showed that VSOPs (very small superparamagnetic iron oxide particles) reveal CNS (central nervous system) lesions in EAE which are not detectable by conventional contrast agents in MRI. We hypothesized that VSOP may help detect early, subtle inflammatory events that would otherwise remain imperceptible. To investigate the capacity of VSOP to reveal early events in CNS inflammation, we induced EAE in SJL mice using encephalitogenic T-cells, and administered VSOP prior to onset of clinical symptoms. In parallel, we administered VSOP to mice at peak disease, and to unmanipulated controls. We examined the distribution of VSOP in the CNS by MRI and histology. Prior to disease onset, in asymptomatic mice, VSOP accumulated in the choroid plexus and in spinal cord meninges in the absence of overt inflammation. However, VSOP was undetectable in the CNS of non-immunized control mice. At peak disease, VSOP was broadly distributed; we observed particles in perivascular inflammatory lesions with apparently preserved glia limitans. Moreover, at peak disease, VSOP was prominent in the choroid plexus and was seen in elongated endothelial structures, co-localized with phagocytes, and diffusely disseminated in the parenchyma, suggesting multiple entry mechanisms of VSOP into the CNS. Thus, using VSOP we were able to discriminate between inflammatory events occurring in established EAE and, importantly, we identified CNS alterations that appear to precede immune cell infiltration and clinical onset.

Optic neuritis interferes with optical coherence tomography and magnetic resonance imaging correlations.

BACKGROUND: Retinal nerve fibre layer (RNFL) thinning is associated with brain atrophy in multiple sclerosis (MS). An influence of optic neuritis is well documented but sparsely investigated. Recently, the retinal ganglion cell layer (GCL) has been shown to provide superior information regarding visual function and retinal neurodegeneration as compared with RNFL. OBJECTIVE: To investigate the association of white and grey matter brain volume with peripapillary RNFL and macular GCL in MS patients with and without a history of optic neuritis. METHODS: 63 patients with relapsing-remitting MS were included in a two-centre cross-sectional prospective study. All patients underwent retinal examination with spectral domain optical coherence tomography and 1.5 T MRI for determination of normalized brain volume (NBV), white matter volume (NWMV) and grey matter volume (NGMV). RESULTS: Both RNFL and GCL were associated with NBV, NWMV and NGMV in eyes without previous optic neuritis. This association is disrupted in the case of NGMV following optic neuritis. CONCLUSIONS: Both RNFL and GCL as parameters of neuro-axonal damage are comparably linked to whole brain as well as white and grey matter atrophy. An event of optic neuritis interferes with this relation, adding further damage to the optic nerve and disrupting especially an association with grey matter.

Association of retinal and macular damage with brain atrophy in multiple sclerosis.

Neuroaxonal degeneration in the central nervous system contributes substantially to the long term disability in multiple sclerosis (MS) patients. However, in vivo determination and monitoring of neurodegeneration remain difficult. As the widely used MRI-based approaches, including the brain parenchymal fraction (BPF) have some limitations, complementary in vivo measures for neurodegeneration are necessary. Optical coherence tomography (OCT) is a potent tool for the detection of MS-related retinal neurodegeneration. However, crucial aspects including the association between OCT- and MRI-based atrophy measures or the impact of MS-related parameters on OCT parameters are still unclear. In this large prospective cross-sectional study on 104 relapsing remitting multiple sclerosis (RRMS) patients we evaluated the associations of retinal nerve fiber layer thickness (RNFLT) and total macular volume (TMV) with BPF and addressed the impact of disease-determining parameters on RNFLT, TMV or BPF. BPF, normalized for subject head size, was estimated with SIENAX. Relations were analyzed primarily by Generalized Estimating Equation (GEE) models considering within-patient inter-eye relations. We found that both RNFLT (p = 0.019, GEE) and TMV (p = 0.004, GEE) associate with BPF. RNFLT was furthermore linked to the disease duration (p<0.001, GEE) but neither to disease severity nor patients' age. Contrarily, BPF was rather associated with severity (p<0.001, GEE) than disease duration and was confounded by age (p<0.001, GEE). TMV was not associated with any of these parameters. Thus, we conclude that in RRMS patients with relatively short disease duration and rather mild disability RNFLT and TMV reflect brain atrophy and are thus promising parameters to evaluate neurodegeneration in MS. Furthermore, our data suggest that RNFLT and BPF reflect different aspects of MS. Whereas BPF best reflects disease severity, RNFLT might be the better parameter for monitoring axonal damage longitudinally. Longitudinal studies are necessary for validation of data and to further clarify the relevance of TMV.

Metabolic changes in the visual cortex are linked to retinal nerve fiber layer thinning in multiple sclerosis.

OBJECTIVE: To investigate the damage to the retinal nerve fiber layer as part of the anterior visual pathway as well as an impairment of the neuronal and axonal integrity in the visual cortex as part of the posterior visual pathway with complementary neuroimaging techniques, and to correlate our results to patients' clinical symptoms concerning the visual pathway. DESIGN, SUBJECTS AND METHODS: Survey of 86 patients with relapsing-remitting multiple sclerosis that were subjected to retinal nerve fiber layer thickness (RNFLT) measurement by optical coherence tomography, to a routine MRI scan including the calculation of the brain parenchymal fraction (BPF), and to magnetic resonance spectroscopy at 3 tesla, quantifying N-acetyl aspartate (NAA) concentrations in the visual cortex and normal-appearing white matter. RESULTS: RNFLT correlated significantly with BPF and visual cortex NAA, but not with normal-appearing white matter NAA. This was connected with the patients' history of a previous optic neuritis. In a combined model, both BPF and visual cortex NAA were independently associated with RNFLT. CONCLUSIONS: Our data suggest the existence of functional pathway-specific damage patterns exceeding global neurodegeneration. They suggest a strong interrelationship between damage to the anterior and the posterior visual pathway.

Gadofluorine M-enhanced MRI shows involvement of circumventricular organs in neuroinflammation.

BACKGROUND: Circumventricular organs (CVO) are cerebral areas with incomplete endothelial blood-brain barrier (BBB) and therefore regarded as "gates to the brain". During inflammation, they may exert an active role in determining immune cell recruitment into the brain. METHODS: In a longitudinal study we investigated in vivo alterations of CVO during neuroinflammation, applying Gadofluorine M- (Gf) enhanced magnetic resonance imaging (MRI) in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. SJL/J mice were monitored by Gadopentate dimeglumine- (Gd-DTPA) and Gf-enhanced MRI after adoptive transfer of proteolipid-protein-specific T cells. Mean Gf intensity ratios were calculated individually for different CVO and correlated to the clinical disease course. Subsequently, the tissue distribution of fluorescence-labeled Gf as well as the extent of cellular inflammation was assessed in corresponding histological slices. RESULTS: We could show that the Gf signal intensity of the choroid plexus, the subfornicular organ and the area postrema increased significantly during experimental autoimmune encephalomyelitis, correlating with (1) disease severity and (2) the delay of disease onset after immunization. For the choroid plexus, the extent of Gf enhancement served as a diagnostic criterion to distinguish between diseased and healthy control mice with a sensitivity of 89% and a specificity of 80%. Furthermore, Gf improved the detection of lesions, being particularly sensitive to optic neuritis. In correlated histological slices, Gf initially accumulated in the extracellular matrix surrounding inflammatory foci and was subsequently incorporated by macrophages/microglia. CONCLUSION: Gf-enhanced MRI provides a novel highly sensitive technique to study cerebral BBB alterations. We demonstrate for the first time in vivo the involvement of CVO during the development of neuroinflammation.

Development of ulcerative colitis in a patient with multiple sclerosis following treatment with interferon beta 1a.

To alert clinicians to a potential novel adverse drug effect of interferon beta 1a, we herein report a patient with relapsing-remitting multiple sclerosis who developed ulcerative colitis following treatment with interferon beta 1a. Ulcerative colitis persisted despite discontinuation of interferon beta 1a treatment and switching the patient to glatiramer acetate. Tacrolimus (FK506), 6-mercaptopurine, and prednisolone were required to induce remission. Both ulcerative colitis and multiple sclerosis were eventually well controlled using this regimen. Our report underscores that caution should be exercised when prescribing immunostimulatory agents in patients with inflammatory bowel disease (IBD) and challenges current efforts to stimulate innate immunity as a novel therapeutic concept for IBD.