Josa M. Frischer

The relation between inflammation and neurodegeneration in multiple sclerosis brains

Some recent studies suggest that in progressive multiple sclerosis, neurodegeneration may occur independently from inflammation. The aim of our study was to analyse the interdependence of inflammation, neurodegeneration and disease progression in various multiple sclerosis stages in relation to lesional activity and clinical course, with a particular focus on progressive multiple sclerosis. The study is based on detailed quantification of different inflammatory cells in relation to axonal injury in 67 multiple sclerosis autopsies from different disease stages and 28 controls without neurological disease or brain lesions. We found that pronounced inflammation in the brain is not only present in acute and relapsing multiple sclerosis but also in the secondary and primary progressive disease. T- and B-cell infiltrates correlated with the activity of demyelinating lesions, while plasma cell infiltrates were most pronounced in patients with secondary progressive multiple sclerosis (SPMS) and primary progressive multiple sclerosis (PPMS) and even persisted, when T- and B-cell infiltrates declined to levels seen in age matched controls. A highly significant association between inflammation and axonal injury was seen in the global multiple sclerosis population as well as in progressive multiple sclerosis alone. In older patients (median 76 years) with long-disease duration (median 372 months), inflammatory infiltrates declined to levels similar to those found in age-matched controls and the extent of axonal injury, too, was comparable with that in age-matched controls. Ongoing neurodegeneration in these patients, which exceeded the extent found in normal controls, could be attributed to confounding pathologies such as Alzheimers or vascular disease. Our study suggests a close association between inflammation and neurodegeneration in all lesions and disease stages of multiple sclerosis. It further indicates that the disease processes of multiple sclerosis may die out in aged patients with long-standing disease.

Oxidative damage in multiple sclerosis lesions

Multiple sclerosis is a chronic inflammatory disease of the central nervous system, associated with demyelination and neurodegeneration. The mechanisms of tissue injury are currently poorly understood, but recent data suggest that mitochondrial injury may play an important role in this process. Since mitochondrial injury can be triggered by reactive oxygen and nitric oxide species, we analysed by immunocytochemistry the presence and cellular location of oxidized lipids and oxidized DNA in lesions and in normal-appearing white matter of 30 patients with multiple sclerosis and 24 control patients without neurological disease or brain lesions. As reported before in biochemical studies, oxidized lipids and DNA were highly enriched in active multiple sclerosis plaques, predominantly in areas that are defined as initial or ‘prephagocytic’ lesions. Oxidized DNA was mainly seen in oligodendrocyte nuclei, which in part showed signs of apoptosis. In addition, a small number of reactive astrocytes revealed nuclear expression of 8-hydroxy-d-guanosine. Similarly, lipid peroxidation-derived structures (malondialdehyde and oxidized phospholipid epitopes) were seen in the cytoplasm of oligodendrocytes and some astrocytes. In addition, oxidized phospholipids were massively accumulated in a fraction of axonal spheroids with disturbed fast axonal transport as well as in neurons within grey matter lesions. Neurons stained for oxidized phospholipids frequently revealed signs of degeneration with fragmentation of their dendritic processes. The extent of lipid and DNA oxidation correlated significantly with inflammation, determined by the number of CD3 positive T cells and human leucocyte antigen-D expressing macrophages and microglia in the lesions. Our data suggest profound oxidative injury of oligodendrocytes and neurons to be associated with active demyelination and axonal or neuronal injury in multiple sclerosis.

NADPH oxidase expression in active multiple sclerosis lesions in relation to oxidative tissue damage and mitochondrial injury

Multiple sclerosis is a chronic inflammatory disease of the central nervous system, associated with demyelination and neurodegeneration. The mechanisms of tissue injury are poorly understood, but recent data suggest that mitochondrial injury may play an important role in this process. Mitochondrial injury can be triggered by reactive oxygen and nitric oxide species, and we recently provided evidence for oxidative damage of oligodendrocytes and dystrophic axons in early stages of active multiple sclerosis lesions. In this study, we identified potential sources of reactive oxygen and nitrogen species through gene expression in carefully staged and dissected lesion areas and by immunohistochemical analysis of protein expression. Genome-wide microarrays confirmed mitochondrial injury in active multiple sclerosis lesions, which may serve as an important source of reactive oxygen species. In addition, we found differences in the gene expression levels of various nicotinamide adenine dinucleotide phosphate oxidase subunits between initial multiple sclerosis lesions and control white matter. These results were confirmed at the protein level by means of immunohistochemistry, showing upregulation of the subunits gp91phox, p22phox, p47phox, nicotinamide adenine dinucleotide phosphate oxidase 1 and nicotinamide adenine dinucleotide phosphate oxidase organizer 1 in activated microglia in classical active as well as slowly expanding lesions. The subunits gp91phox and p22phox were constitutively expressed in microglia and were upregulated in the initial lesion. In contrast, p47phox, nicotinamide adenine dinucleotide phosphate oxidase 1 and nicotinamide adenine dinucleotide phosphate oxidase organizer 1 expression were more restricted to the zone of initial damage or to lesions from patients with acute or early relapsing/remitting multiple sclerosis. Double labelling showed co-expression of the nicotinamide adenine dinucleotide phosphate oxidase subunits in activated microglia and infiltrated macrophages, suggesting the assembly of functional complexes. Our data suggest that the inflammation-associated oxidative burst in activated microglia and macrophages plays an important role in demyelination and free radical-mediated tissue injury in the pathogenesis of multiple sclerosis.

Multiple sclerosis deep grey matter: the relation between demyelination, neurodegeneration, inflammation and iron

In multiple sclerosis (MS), diffuse degenerative processes in the deep grey matter have been associated with clinical disabilities. We performed a systematic study in MS deep grey matter with a focus on the incidence and topographical distribution of lesions in relation to white matter and cortex in a total sample of 75 MS autopsy patients and 12 controls. In addition, detailed analyses of inflammation, acute axonal injury, iron deposition and oxidative stress were performed. MS deep grey matter was affected by two different processes: the formation of focal demyelinating lesions and diffuse neurodegeneration. Deep grey matter demyelination was most prominent in the caudate nucleus and hypothalamus and could already be seen in early MS stages. Lesions developed on the background of inflammation. Deep grey matter inflammation was intermediate between low inflammatory cortical lesions and active white matter lesions. Demyelination and neurodegeneration were associated with oxidative injury. Iron was stored primarily within oligodendrocytes and myelin fibres and released upon demyelination. In addition to focal demyelinated plaques, the MS deep grey matter also showed diffuse and global neurodegeneration. This was reflected by a global reduction of neuronal density, the presence of acutely injured axons, and the accumulation of oxidised phospholipids and DNA in neurons, oligodendrocytes and axons. Neurodegeneration was associated with T cell infiltration, expression of inducible nitric oxide synthase in microglia and profound accumulation of iron. Thus, both focal lesions as well as diffuse neurodegeneration in the deep grey matter appeared to contribute to the neurological disabilities of MS patients.

Clinical and pathological insights into the dynamic nature of the white matter multiple sclerosis plaque

An extensive analysis of white matter plaques in a large sample of multiple sclerosis (MS) autopsies provides insights into the dynamic nature of MS pathology.

Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis.

Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in experimental demyelination and remyelination in vivo and in vitro are consistent with a partial amelioration of the supposed increase in energy demand of demyelinated axons by remyelination.

Multiple sclerosis and Alzheimer's disease.

Chronic inflammation with microglia activation is thought to play a major role in the formation or clearance of Alzheimers disease (AD) lesions, as well as in the induction of demyelination in multiple sclerosis (MS). In MS, the cortex is severely affected by chronic, long‐lasting inflammation, microglia activation, and demyelination. To what extent chronic inflammation in the cortex of MS patients influences the development of AD lesions is so far unresolved.

Long-term seizure control after resection of supratentorial cavernomas: a retrospective single-center study in 53 patients.

OBJECTIVEThe goal of this study was to examine the long-term outcomes of 53 epilepsy patients who were surgically treated for supratentorial cavernomas in a single-center study and to assess both the duration of epilepsy and the resection of the hemosiderin rim for their prognostic relevance during extended follow-up. METHODSFifty-three patients underwent microsurgical resection of radiologically diagnosed supratentorial cavernomas. For the outcome analysis, they were divided into 2 groups: Group A (33 patients) with a preoperative duration of epilepsy of less than 2 years, and Group B (20 patients) with a preoperative duration of epilepsy of 2 years or more. The natural history of the cavernomas, localization and size of the lesions, use of antiepileptic drugs, surgery timing, and technique (removal or not of the surrounding gliosis) were evaluated retrospectively. The outcome of epilepsy was based on Engels classification and the International League Against Epilepsy classification. RESULTSAfter a mean follow-up period of 8.1 years, 45 (84.9%) of the 53 patients were free from disabling seizures (Engel Class I), including 37 patients (69.8%) who were completely free of postoperative seizures (Engel Class IA); 43 patients (81.1%) were categorized as International League Against Epilepsy Class 1. Outcome was statistically significantly improved in the patient subgroup of our study in which patients underwent a resection of the surrounding gliosis after a preoperative duration of epilepsy of less than 2 years (Group A). There was no mortality, and only minor postoperative neurological deficits occurred in 7.5% of patients. CONCLUSIONIn a long-term follow-up period, 84.9% of the patients in the study could be evaluated as Engel Class I. The analysis of outcome showed that patients benefited significantly from early surgery and excision of the hemosiderin rim.

Pathologic Heterogeneity Persists in Early Active Multiple Sclerosis Lesions

Multiple sclerosis (MS) lesions demonstrate immunopathological heterogeneity in patterns of demyelination. Previous cross‐sectional studies reported immunopatterns of demyelination were identical among multiple active demyelinating lesions from the same individual, but differed between individuals, leading to the hypothesis of intraindividual pathological homogeneity and interindividual heterogeneity. Other groups suggested a time‐dependent heterogeneity of lesions. The objective of our present study was to analyze tissue samples collected longitudinally to determine whether patterns of demyelination persist over time within a given patient.

Cerebral cavernous malformations: congruency of histopathological features with the current clinical definition

Aim: Cerebral cavernous malformations (CCMs) are defined as a mulberry-like assembly of thin walled vascular sinusoids lined by a thin endothelium lacking smooth muscle and elastin, displaying no intervening brain parenchyma. In this study, we analyse the congruency of histopathological features with the current clinical definition on a large series of neuroradiologically verified CCMs. Methods: 87 patients who received no primary treatment prior to surgery were included. Preoperative MRIs of all patients were reviewed. 12 histopathological parameters were assessed systematically, using haematoxylin-eosin, Prussian blue, elastica van Gieson and congo red for amyloid detection. Results: 71/87 (81.6%) of the cases fulfilled the basic histological criteria of CCMs. However, the thickness of the vessel walls and the calibre of the malformed vessels were highly variable. 16/87 cases (18.4%) were histologically non-diagnostic. Non-diagnostic specimens were significantly associated with radiological signs of haemorrhage (p = 0.001). A few cases (4.6%) regionally contained capillary-like malformed vessels. Intervening brain parenchyma between malformed vessels throughout the lesion was seen in 50/71 (70.4%) diagnosable lesions. Haemosiderin deposits, gliosis, thrombosis, fibrotic changes, hyalinised vessel walls, calcification and cholesterol crystals were present in a considerable range. In addition, we found amyloid deposits in 14/87 (16.1%) specimens. Conclusion: Contrary to the current clinical definition, the absence of intervening brain parenchyma does not represent an essential histopathological criterion of CCMs in our series. Furthermore, the diameter of the vessel lumina and the thickness of vessel walls varied considerably. Based on these findings, adaptation of the current definition on the basis of interdisciplinary interaction needs to be considered.