Axonal transection in the lesions of multiple sclerosis

Axonal damage in multiple sclerosis plaques: a combined magnetic resonance imaging and 1H-magnetic resonance spectroscopy study

The purpose of this study was to compare magnetic resonance imaging (MRI) features and proton MR spectroscopy (1H-MRS) patterns of multiple sclerosis (MS) plaques in order to define the metabolic substrate in different lesion subtypes. Combined MRI and single-voxel 1H-MRS investigation was performed in 54 MS patients (47 relapsing remitting (RR) and seven secondary progressive (SP)). Sixty-seven MS lesions were selected. Thirty-seven lesions were Gadolinium (Gd) enhancing (nine isointense and 28 hypointense on pre-contrast T(1)-weighted scans) and 30 Gd unenhancing (six isointense and 24 hypointense on pre- and post-contrast T(1)-weighted scans). Choline (Cho), creatine (Cr), N-acetyl aspartate (NAA) and lactate were evaluated in 1H spectra acquired from MS plaques and from normal white matter (NWM) of 22 neurological controls. MS lesions of RR patients were characterized by a significant increase of Cho/Cr and decrease of NAA/Cr and NAA/Cho ratios. No significant metabolite changes were found in lesions of SP patients. Gd enhancing plaques showed lactate signal with higher frequency (37.8%) than Gd unenhancing plaques (16.7%) (p=0.04). A significant increase of Cho/Cr was found in Gd enhancing lesions when compared to controls (p<0.01), and to Gd unenhancing lesions (p<0.05). In particular, there was evidence of a significant increase of Cho/Cr in pre-contrast T(1) hypointense Gd enhancing lesions (p<0.01 vs. controls). The Gd unenhancing lesions (p<0.01), in particular the T(1) hypointense group (p<0.05), showed a significant decrease of NAA/Cr only when compared to controls. These data confirm that in vivo MRS indicates key pathological features of MS plaques. The increased Cho/Cr ratio found in Gd-enhancing plaques, in particular in the T(1) hypointense lesions, may reflect increased membrane cell turnover. The T(1) hypointense Gd unenhancing plaques better reflect axonal damage, as suggested by the decrease of NAA/Cr. Nevertheless, the lack of statistical differences in NAA/Cr between plaque subgroups suggests that axonal impairment might occur even in the early stages.

Post-mortem high-resolution MRI of the spinal cord in multiple sclerosis: a correlative study with conventional MRI, histopathology and clinical phenotype

We used high-resolution MRI to study the post-mortem appearance of spinal cord multiple sclerosis in relation to histopathology and low-resolution images. Fifty-nine 3 cm long formalin-fixed spinal cord specimens from 19 multiple sclerosis patients and three controls were studied. Clinical characteristics of each patient were reviewed. High-field MRI consisted of proton-density weighted spin-echo imaging with an in-plane resolution of 80 microm. Specimens were also imaged at 1.0 T, with 1 mm pixel resolution. After MRI, the specimens were cut at 5 mm intervals and stained for myelin (Luxol fast blue/cresyl violet) and axons (Bodian method). Two observers scored the MRIs for abnormalities and divided them into (i) well-delineated areas of high signal intensity (SI) and (ii) poorly defined areas of mildly increased SI. Abnormalities were scored semiquantitatively, white matter and grey matter separately. In 81 sections the total area of abnormalities per section was measured on both histopathology sections and on matched high-field MRIs. Abnormalities ranged from just a few abnormal areas to complete involvement of the spinal cord specimen. Patients with an aggressive disease course had more abnormalities than patients with a mild or intermediate disease course. Areas of mildly increased SI were seen in all specimens, and were often found around focal high-SI lesions. However, in six patients, areas of mildly increased SI were the predominant finding on the MRIs, correlating with a primary progressive disease course. Histopathologically, high-SI areas correlated with complete demyelination, while mildly increased SI corresponded with partial demyelination. All areas scored as abnormal by the neuropathologist were also found on the MRIs, and sizes measured using both methods correlated well (r = 0.85, P<0.01). On conventional MRIs, abnormalities could be recognized fairly well. However, better differentiation could be made between high-SI and mildly increased SI abnormalities on the 4.7 T images. In conclusion, high-resolution MRI revealed a great range of abnormalities in spinal cord multiple sclerosis, which related to disease course during life. Furthermore, we found very good correlation between the extent of abnormalities shown by histopathology and the SI changes on proton-density MRIs, mainly relating to demyelination revealed histopathologically.

Aminopyridines for symptomatic treatment in multiple sclerosis

BACKGROUND

Because of their ability to increase nerve conduction in demyelinated nerve fibers, potassium channel blockers 4-aminopyridine (AP) and 3,4-diaminopyridine (DAP) have been proposed as a symptomatic therapy for people with multiple sclerosis (MS).

OBJECTIVES

To determine the efficacy and safety of aminopyridines in improving neurological deficits in people with MS.

SEARCH STRATEGY

Computerised general (MEDLINE, EMBASE) and specialised databases (Cochrane MS Group's trials register, CCTR). Hand search of bibliographic references from retrieved studies and recent MS symposia reports. Contact with principal investigators of known studies.

SELECTION CRITERIA

Trials were included if they fulfilled all following criteria: randomised controlled trials (RCTs); adults with MS, out of exacerbation; AP or DAP treatment versus placebo; clinical endpoints.

DATA COLLECTION AND ANALYSIS

We identified 26 potentially pertinent studies. Three reviewers independently extracted data and assessed trial quality from the 16 studies available as full papers.

MAIN RESULTS

Five studies (six publications) and 144 participants were considered in this review. Two more abstracts are awaiting assessment. All five studies were single-centre, double-blind, crossover trials. Four studies assessed the efficacy of AP versus placebo, one compared DAP with active placebo. The duration of treatment ranged from hours to three months. The median quality score of the studies was 3 (range 2-5). The heterogeneity of outcome assessment and the absence of information on individual study periods, allowed quantitative pooling of results for few categorical variables. Of the 144 treated patients, there were six major side effects: one acute encephalopathy, three episodes of confusion, and two seizures. Manual muscle testing was assessed in three studies (54 patients), with 29 patients (54%) improving in at least one muscular district during study treatment versus four patients (7%) during placebo (odds ratio [OR] 14.5, 95% confidence interval [CI] 4.7-43.7). Ambulation was assessed in three studies (54 patients): 9 patients (17%) improved during study treatment versus none during placebo (p<0.001). An improvement in EDSS score was found in 13 of the 144 participants during study treatment (9%) versus none during placebo (p<0.001). No improvement in neuropsychological tests was found in the two trials that evaluated cognitive function. Finally, 47 of 136 people with MS (35%) felt improved when receiving the study drug, against 7(5%) on placebo (OR 9.7, 95% CI 4.3-22.0).

REVIEWER'S CONCLUSIONS

Based on currently available information, no unbiased statement can be made about the safety or efficacy of aminopyridines for treating MS symptoms. Furthermore, we could not obtain any data on three unpublished RCTs involving more than 300 participants. We conclude that publication bias remains a pervasive problem in this area, and that until the results of these unpublished studies are available to the scientific community, no confident estimate of effectiveness of aminopyridines in the management of MS symptoms is possible.

Relationship between brain atrophy and disability: an 8-year follow-up study of multiple sclerosis patients

Brain atrophy measurement can provide an estimate of the amount of tissue destruction due to the pathologic processes in multiple sclerosis. The potential usefulness of atrophy as a marker of disease progression depends upon the concurrent and predictive relationships between atrophy and disability. A follow-up study was performed to measure atrophy and disability scores in patients from the Multiple Sclerosis Collaborative Research Group's phase III trial of IFNbeta-1a (Avonex) in relapsing- remitting multiple sclerosis. New data were obtained on 160 out of 172 eligible patients from the original trial were enrolled in the follow-up study approximately 8 years after randomization. The follow-up visit consisted of several tests and questionnaires including a clinical exam to determine Expanded Disability Status Score (EDSS) and Multiple Sclerosis Functional Composite (MSFC), and a magnetic resonance imaging exam to calculate the brain parenchymal fraction. Brain parenchymal fraction was correlated with both EDSS and MSFC at each of the four time points for which data were available (baseline 1, 2 and 8 years). Furthermore, the change in BPF was correlated with the changes in disability scores from the end of the phase III trial to the follow-up exam. These data suggest that brain atrophy may be a useful and clinically relevant marker of disease progression in relapsing--remitting MS.

Role of chemokines, neuronal projections, and the blood-brain barrier in the enhancement of cerebral EAE following focal brain damage

The role of focal brain damage as a trigger for autoimmune inflammation in multiple sclerosis (MS) is unclear. In this study we examine mechanisms by which experimental autoimmune encephalomyelitis (EAE) is enhanced by focal brain damage. EAE was produced in Lewis rats by footpad inoculation; focal brain damage, in the form of a cortical cryolesion (cryolesion-EAE), was induced 8 days post-inoculation (d.p.i.). The distribution of inflammation and chemokine production in cryolesion-EAE and EAE-only were compared. Inflammation in the brain, measured by immunocytochemistry for T lymphocytes (W3/13) and microglial activation (MHC class II -OX6), was significantly enhanced in cryolesion-EAE 11-15 d.p.i. (p < 0.01-0.05) but by 20-40 d.p.i., equated with EAE-only. Inflammation in cryolesion-EAE related to breakdown of the blood-brain barrier (BBB) at the site of the cryolesion and also to the corticospinal tracts and thalamus, reflecting the afferent and efferent neuronal connections with the cryolesioned cortex. Semiquantitative RT/PCR dot-blot hybridization assay showed a 6-fold increase in mRNA for specific chemokines in the brain in cryolesion-EAE at 9 d.p.i. (MCP-1) and 11 d.p.i. (MCP-1 and MCP-5) with no significant increase in RANTES, GRO-alpha, or MIP-1alpha. By 14 d.p.i., the levels of MCP-1 and MCP-5 mRNA equated with EAE-only animals. These results suggest that enhancement and location of autoimmune inflammation in the brain following focal cortical injury initially involve chemokines such as the macrophage chemoattractants MCP-1 and MCP-5, and the activities of afferent and efferent neuronal connections with the site of damage. By analogy, similar factors may modulate or reactivate autoimmune inflammation in MS.

The accuracy of whole brain N-acetylaspartate quantification

A non-localizing pulse sequence to quantify the total amount of N-acetylaspartate (NAA) in the whole brain (WBNAA) was introduced recently [Magn. Reson. Med. 40, 684-689 (1998)]. However, it is known that regional magnetic field inhomogeneities, deltaB0s, arising from susceptibility differences at tissue interfaces, shift and broaden local resonances to outside the integration window, leading to an underestimation of the true amount of NAA in the entire brain. To quantify the upper limit of this loss, the whole-head proton MR spectrum (1H-MRS) of the water was integrated over the same frequency width as the NAA. The ratio of this area/total-water-line was 75 +/- 5% in 5 volunteers. The procedure was repeated with the brain-only water peak, obtained by summing signals only from voxels within that organ from a three-dimensional chemical-shift-imaging (3D CSI) set. It indicated that <10% of the water signal loss occurred in the brain. Therefore, by analogy, WBNAA accounts for >90% of that metabolite.

Brain atrophy in relapsing multiple sclerosis: relationship to relapses, EDSS, and treatment with interferon beta-1a

Brain atrophy is a relevant surrogate marker of the disease process in multiple sclerosis (MS) because it represents the net effect of various pathological processes leading to brain tissue loss. There are various approaches to quantifying central nervous system atrophy in MS. We have focused on a normalized measure of whole brain atrophy, the brain parenchymal fraction (BPF). BPF is defined as the brain parenchymal volume, divided by the volume within the surface of the brain. We applied this method to an MRI data set generated during a phase III clinical trial of interferon beta-1a (AVONEX). The purpose of the current study is to further explore clinical and MRI correlates of the BPF, particularly as they relate to relapse rate and Kurtzke's Expanded Disability Status Score (EDSS); and to further explore the therapeutic effects observed in interferon beta-1a recipients. Of all demographic and disease measures in the clinical trial data base, T2 lesion volume most closely correlated with BPF in cross sectional studies, and was the baseline factor most closely correlated with progressive brain atrophy in the subsequent 2 years. We also observed that change in T2 lesion volume was the disease measure most closely correlated with change in BPF during 2 years of observation. Of interest, relapse number and EDSS change during 2 years were only weakly correlated with BPF change during the same period. Disability progression, defined as sustained worsening of at least 1.0 EDSS points from baseline, persisting at least 6 months, was associated with significantly greater brain atrophy progression. We observed a therapeutic effect of interferon beta-1a in the second year of the clinical trial, and this beneficial effect was not accounted for by change in gadolinium enhanced lesion volume, or by corticosteroid medication within 40 days of the final MRI scan. The BPF is an informative surrogate marker for destructive pathological processes in relaping MS patients, and is useful in demonstrating treatment effects in controlled clinical trials. The significance of progressive brain atrophy during relapsing MS will be assessed by measuring clinical and MRI changes in prospective follow up studies.

Relapses and progression of disability in multiple sclerosis

BACKGROUND

The influence of the patterns of onset of multiple sclerosis and relapses of the disease on the time course of irreversible disability is controversial.

METHODS

In 1844 patients with multiple sclerosis who were followed for a mean (+/- SD) of 11 +/- 10 years, we determined the time of the clinical onset of the disease, the initial course (relapsing-remitting or progressive) and the subsequent course (relapsing-remitting, secondary progressive, or primary progressive), the times of relapses, the time to the onset of irreversible disability, and the time course of progressive, irreversible disability. We used three scores on the Kurtzke Disability Status Scale (range, 0 to 10, with higher scores indicating more severe disability) as measures of the severity and progression of disability: a score of 4 (limited walking ability but able to walk for more than 500 m without aid or rest), a score of 6 (ability to walk with unilateral support no more than 100 m without rest), and a score of 7 (ability to walk no more than 10 m without rest while leaning against a wall or holding onto furniture for support). We used Kaplan-Meier analyses to determine the influence of relapses on the time to the onset of irreversible disability.

RESULTS

The median times from the onset of multiple sclerosis to the assignment of a score of 4, a score of 6, and a score of 7 on the disability scale were longer among the 1562 patients with a relapsing-remitting onset of disease (11.4, 23.1, and 33.1 years, respectively) than among the 282 patients who had progressive disease from the onset (0.0, 7.1, and 13.4 years, respectively; P<0.001 for all comparisons). In contrast, the times from the assignment of a score of 4 to a score of 6 were similar in the two groups (5.7 and 5.4 years, P=0.74). The time course of progressive, irreversible disease among patients with the primary progressive type of multiple sclerosis was not affected by the presence or absence of superimposed relapses.

CONCLUSIONS

Among patients with multiple sclerosis, relapses do not significantly influence the progression of irreversible disability.

Female sex steroids: effects upon microglial cell activation

Multiple sclerosis occurs more commonly in females than males. However, the mechanisms resulting in gender differences in multiple sclerosis are unknown. Activated microglia are believed to contribute to multiple sclerosis pathology, perhaps in part due to production of nitric oxide (NO) and TNF-alpha, molecules which can be toxic to cells including oligodendrocytes. The current study demonstrates that the female sex steroids estriol, beta-estradiol and progesterone inhibit lipopolysaccharide (LPS) induction of nitric oxide (NO) production by primary rat microglia and by the mouse N9 microglial cell line. These hormones act by inhibiting the production of inducible nitric oxide synthase (iNOS) which catalyses the synthesis of NO. Estriol likely inhibits iNOS gene expression since the hormone blocks LPS induction of iNOS RNA levels. The pro-inflammatory cytokines IFN-gamma and TNF-alpha are believed to be important modulators of multiple sclerosis. Here, we demonstrate that estrogens and progesterone also inhibit NO production by microglial cells activated in response to these cytokines. Activated microglia elicit TNF-alpha in addition to NO and we further demonstrate that estrogens and progesterone repress TNF-alpha production by these cells. Finally, estriol and progesterone, at concentrations consistent with late pregnancy, inhibit NO and TNF-alpha production by activated microglia, suggesting that hormone inhibition of microglial cell activation may contribute to the decreased severity of multiple sclerosis symptoms commonly associated with pregnancy.

Acute multiple sclerosis characterized by extensive mononuclear phagocyte infiltration

In this study, we examine the clinical, neuroradiological, and immunohistochemical findings of a 51 year old white female who died 27 months after onset of acute multiple sclerosis despite treatment with interferon-beta, azathioprine, corticosteroids, and cyclophosphamide. Immunohistochemical studies revealed extensive gliosis and mononuclear phagocyte infiltration with corresponding upregulation of proinflammatory cytokines (eg. IFN-alpha, TNF-alpha). The significance of immunohistochemical findings with respect to clinical presentation is discussed.

Evidence for adaptive functional changes in the cerebral cortex with axonal injury from multiple sclerosis

Axonal injury occurs even in the earliest stages of multiple sclerosis. Magnetic resonance spectroscopic imaging (MRSI) measurements of brain N:-acetylaspartate (NAA), a marker of axonal integrity, show that this axonal injury can occur even in the absence of clinically evident functional impairments. To test whether cortical adaptive responses contribute to the maintenance of normal motor function in patients with multiple sclerosis, we performed MRSI and functional MRI (fMRI) examinations of nine multiple sclerosis patients who had unimpaired hand function. We found that activation of the ipsilateral sensorimotor cortex with simple hand movements was increased by a mean of fivefold relative to normal controls (n = 8) and that the extent of this increase was strongly correlated (sigma = -0.93, P = 0.001) with decreases in brain NAA. These results suggest that compensatory cortical adaptive responses may help to account for the limited relationship between conventional MRI measures of lesion burden and clinical measures of disability, and that therapies directed towards promoting cortical reorganization in response to brain injury could enhance recovery from relapses of multiple sclerosis.

Sensory neuron-specific sodium channel SNS is abnormally expressed in the brains of mice with experimental allergic encephalomyelitis and humans with multiple sclerosis

Clinical abnormalities in multiple sclerosis (MS) have classically been considered to be caused by demyelination and/or axonal degeneration; the possibility of molecular changes in neurons, such as the deployment of abnormal repertoires of ion channels that would alter neuronal electrogenic properties, has not been considered. Sensory Neuron-Specific sodium channel SNS displays a depolarized voltage dependence, slower activation and inactivation kinetics, and more rapid recovery from inactivation than classical "fast" sodium channels. SNS is selectively expressed in spinal sensory and trigeminal ganglion neurons within the peripheral nervous system and is not expressed within the normal brain. Here we show that sodium channel SNS mRNA and protein, which are not present within the cerebellum of control mice, are expressed within cerebellar Purkinje cells in a mouse model of MS, chronic relapsing experimental allergic encephalomyelitis. We also demonstrate SNS mRNA and protein expression within Purkinje cells from tissue obtained postmortem from patients with MS, but not in control subjects with no neurological disease. These results demonstrate a change in sodium channel expression in neurons within the brain in an animal model of MS and in humans with MS and suggest that abnormal patterns of neuronal ion channel expression may contribute to clinical abnormalities such as ataxia in these disorders.

Human herpesvirus 6 and multiple sclerosis: systemic active infections in patients with early disease

By means of immunohistochemical staining, cells actively infected with human herpesvirus 6 (HHV-6) were found in central nervous system tissues from 8 (73%) of 11 patients with definite multiple sclerosis (MS). Interestingly, 17 (90%) of 19 tissue sections showing active demyelination were positive for HHV-6-infected cells compared with only 3 (13%) of 23 tissue sections free of active disease (P<.0001). Central nervous system tissues from 2 of 28 normal persons and patients with other inflammatory demyelinative diseases were positive for HHV-6-infected cells (P<.0001), and the 2 positive cases were diagnosed as having HHV-6 leukoencephalitis. By use of a rapid culture assay, blood samples from 22 (54%) of 41 patients with definite MS were found to contain active HHV-6 infections, compared with 0 of 61 normal controls (P<.0001). No significant difference was found between HHV-6 viremia-positive and HHV-6 viremia-negative MS patients with respect to type of disease (relapsing/remitting or progressive). In contrast, patients with active HHV-6 viremia were significantly younger and had shorter durations of disease than did HHV-6 viremia-negative patients.

Quantitative ultrastructural analysis of a single spinal cord demyelinated lesion predicts total lesion load, axonal loss, and neurological dysfunction in a murine model of multiple sclerosis

Infection of susceptible mice with Theiler's murine encephalomyelitis virus results in neurological dysfunction from progressive central nervous system demyelination that is pathologically similar to the human disease, multiple sclerosis. We hypothesized that the development of neuropathology proceeds down a final common pathway that can be accurately quantified within a single spinal cord lesion. To test this hypothesis, we conducted quantitative ultrastructural analyses of individual demyelinated spinal cord lesions from chronically infected mice to determine whether pathological variables assessed within a single lesion accurately predicted global assessments of morphological and functional disease course. Within lesions we assessed by electron microscopy the frequencies of normally myelinated, remyelinated, and demyelinated axons, as well as degenerating axons and intra-axonal mitochondria. The frequency of medium and large remyelinated fibers within a single lesion served as a powerful indicator of axonal preservation and correlated with preserved neurological function. The number of degenerating axons and increased intra-axonal mitochondria also correlated strongly with global measures of disease course, such as total lesion load, spinal cord atrophy, and neurological function. This is the first study to demonstrate that functional severity of disease course is evident within a single demyelinated lesion analyzed morphometrically at the ultrastructural level.

MR spectroscopy: a powerful tool for investigating brain function and neurological diseases

Magnetic resonance spectroscopy (MRS) has attracted much attention in recent years and has become an important tool to study in vivo particular biochemical aspects of brain disorders. Since the proton is the most sensitive stable nucleus for MRS, and since almost all metabolites contain hydrogen atoms, investigation by in vivo 1H MRS provides chemical information on tissue metabolites, thus enabling a non-invasive assessment of changes in brain metabolism underlying several brain diseases. In this review a brief description of the basic principles of MRS is given. Moreover, we provide some explanations on the techniques and technical problems related to the use of 1H MRS in vivo including water suppression, localization, editing, quantitation and interpretation of 1H spectra. Finally, we discuss the more recent advancement in three major areas of neurological diseases: brain tumors, multiple sclerosis, and inborn errors of metabolism.

Encephalitogenic potential of the myelin basic protein peptide (amino acids 83-99) in multiple sclerosis: results of a phase II clinical trial with an altered peptide ligand

Myelin-specific T lymphocytes are considered essential in the pathogenesis of multiple sclerosis. The myelin basic protein peptide (a.a. 83-99) represents one candidate antigen; therefore, it was chosen to design an altered peptide ligand, CGP77116, for specific immunotherapy of multiple sclerosis. A magnetic resonance imaging-controlled phase II clinical trial with this altered peptide ligand documented that it was poorly tolerated at the dose tested, and the trial had therefore to be halted. Improvement or worsening of clinical or magnetic resonance imaging parameters could not be demonstrated in this small group of individuals because of the short treatment duration. Three patients developed exacerbations of multiple sclerosis, and in two this could be linked to altered peptide ligand treatment by immunological studies demonstrating the encephalitogenic potential of the myelin basic protein peptide (a.a. 83-99) in a subgroup of patients. These data raise important considerations for the use of specific immunotherapies in general.

A longitudinal study of ventricular volume in early relapsing-remitting multiple sclerosis

The specific aim of this study was to determine whether progressive brain atrophy could be detected within 18 months of establishing a diagnosis of relapsing-remitting multiple sclerosis (RRMS). Fifteen patients with clinically definite RRMS (mean disease duration from first symptom=6 months, mean EDSS=1.2) completed 6 - 14 monthly quantitative MRI sessions. The volume of the lateral ventricles was determined each month using a semi-automated thresholding technique from T1-weighted axial images. The number of new monthly gadolinium-enhancing (Gd+) lesions and EDSS scores were also recorded. Lateral ventricular volumes increased significantly during this study. When individual data were examined, statistically significant changes were observed in six of 15 patients. Monthly change in ventricular volume was related to baseline EDSS and total number of new Gd(+) lesions. These observations indicate brain atrophy, a putative imaging marker of diffuse demyelination and axonal loss, can occur as early as 18 months after first symptoms of RRMS, and is related to the baseline level of disability and to the number of new Gd+ lesions. Multiple Sclerosis (2000) 6 332 - 337

NG2-positive oligodendrocyte progenitor cells in adult human brain and multiple sclerosis lesions

Multiple sclerosis (MS) is characterized by multifocal loss of myelin, oligodendrocytes, and axons. Potential MS therapies include enhancement of remyelination by transplantation or manipulation of endogenous oligodendrocyte progenitor cells. Characteristics of endogenous oligodendrocyte progenitors in normal human brain and in MS lesions have not been studied extensively. This report describes the distribution of cells in sections from normal adult human brain and MS lesions by using antibodies directed against NG2, an integral membrane chondroitin sulfate proteoglycan expressed by oligodendrocyte progenitor cells. Stellate-shaped NG2-positive cells were detected in the white and gray matter of normal adult human brain and appeared as abundant as, but distinct from, astrocytes, oligodendrocytes, and microglia. Stellate-shaped or elongated NG2-positive cells also were detected in chronic MS lesions. A subpopulation of the elongated NG2-positive cells expressed the putative apoptotic signaling molecule p75(NTR). TUNEL-positive cells in three active, nine chronic active, and four chronic inactive lesions, however, were p75(NTR)-negative. These studies identify cells with phenotypic markers of endogenous oligodendrocyte progenitors in the mature human CNS and suggest that functional subpopulations of NG2-positive cells exist in MS lesions. Endogenous oligodendrocyte progenitor cells may represent a viable target for future therapies intended to enhance remyelination in MS patients.

Resistance to glucocorticoid-induced apoptosis in PLP peptide-specific T cell clones from patients with progressive MS

Glucocorticoids (GC) are commonly used to treat inflammatory disorders such as multiple sclerosis (MS) and may exert their immunosuppressive activity by inducing apoptosis in activated lymphocytes. However, unlike relapsing-remitting MS patients, those with progressive disease respond poorly to GC treatment. The data in this communication indicate that PLP peptide-specific T cell clones from progressive, but not relapsing-remitting MS patients are resistant to GC-induced apoptosis in vitro, in a fashion associated with expression of B-7 co-stimulatory molecules. Thus, failure to respond to GC treatment may reflect defect in apoptosis that develop during the progressive stages of chronic inflammatory disease.

Variations in T1 and T2 relaxation times of normal appearing white matter and lesions in multiple sclerosis

OBJECTIVE

To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain.

BACKGROUND

The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions.

METHOD

Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times.

RESULTS

Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times.

CONCLUSION

Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection.

Gene therapy in experimental autoimmune encephalomyelitis

Gene therapy traditionally has been associated with "gene replacement." where exogenous recombinant DNA is introduced ex vivo into somatic cells that are then introduced back into the patient as a way to correct an inherited genetic defect. However, several novel gene therapy strategies for treating autoimmune diseases recently have emerged. Strategies involving the use of several types of DNA vaccines, the application of various viral vectors, and the use of diverse cellular vectors have shown promise in inhibiting autoimmune-mediated inflammation and repairing tissue damaged as a result of autoimmune attack. In the current review, we examine and discuss the development and proposed use of emerging gene therapy strategies for the treatment of autoimmune disease with specific emphasis on experimental autoimmune encephalomyelitis (EAE), an animal model widely used in multiple sclerosis (MS) research.

Xenotransplantation of transgenic pig olfactory ensheathing cells promotes axonal regeneration in rat spinal cord

Here we describe transplantation of olfactory ensheathing cells (OECs) or Schwann cells derived from transgenic pigs expressing the human complement inhibitory protein, CD59 (hCD59), into transected dorsal column lesions of the spinal cord of the immunosuppressed rat to induce axonal regeneration. Non-transplanted lesion-controlled rats exhibited no impulse conduction across the transection site, whereas in animals receiving transgenic pig OECs or Schwann cells impulse conduction was restored across and beyond the lesion site for more than a centimeter. Cell labeling indicated that the donor cells migrated into the denervated host tract. Conduction velocity measurements showed that the regenerated axons conducted impulses faster than normal axons. By morphological analysis, the axons seemed thickly myelinated with a peripheral pattern of myelin expected from the donor cell type. These results indicate that xenotranplantation of myelin-forming cells from pigs genetically altered to reduce the hyperacute response in humans are able to induce elongative axonal regeneration and remyelination and restore impulse conduction across the transected spinal cord.

Relationship between disease activity and dose-response relationships with beta interferon therapies in the treatment of multiple sclerosis

Beta-interferon (IFNbeta) therapy in patients with multiple sclerosis has proven efficacious in the treatment of multiple sclerosis (MS). Numerous studies have demonstrated a decrease in relapse rates, decreases in new gadolinium enhanced lesions, slowed accumulation of disability, and decreases in the accumulation of lesion burden on T2 weighted MRI scans. There has been a heterogeneity of responsiveness to IFNbetas in individual patients. Responsiveness to IFNbeta therapy is discussed in view of pre-existing disease activity. Disease activity can be objectively measured using the frequency and volume of new gadolinium enhancing lesions. Disability may be dependent upon lesion location, frequency, and by the intensity of inflammation within lesions. The presence of a dose-response relationship with IFNbeta therapy in MS is supported by available data. Evidence is reviewed supporting the argument that responsiveness to IFNbeta therapy depends, in part, on pre-existing disease activity.

Quantitative diffusion measurements in focal multiple sclerosis lesions: correlations with appearance on TI-weighted MR images

OBJECTIVE

Relative hypointensity on T1-weighted MR imaging has been suggested as a putative disability marker. The purpose of our study was to determine if there are quantifiable diffusion differences among focal multiple sclerosis lesions that appear differently on conventional T1-weighted MR images. We hypothesized that markedly hypointense lesions on unenhanced T1-weighted images would have significantly increased diffusion compared with other lesions, and enhancing portions of lesions would have different diffusion compared with nonenhancing lesions.

SUBJECTS AND METHODS

Average apparent diffusion coefficient (ADC) was calculated for 107 lesions identified on T2-weighted images in 16 patients with multiple sclerosis and was compared with the ADC of normal white matter in 16 age- and sex-matched control subjects. Seventy-five nonenhancing lesions (29 isointense, 46 hypointense) and 32 enhancing lesions (6 isointense, 26 hypointense) were categorized on the basis of unenhanced T1-weighted MR imaging.

RESULTS

Hypointense and isointense nonenhancing lesions both showed significantly higher ADC than normal white matter (p < 0.0001). Hypointense nonenhancing lesions showed higher ADC values than isointense nonenhancing lesions (p < 0.0001). Diffusion in enhancing portions of enhancing lesions was decreased when compared with nonenhancing portions.

CONCLUSION

Quantitative diffusion data from MR imaging differ among multiple sclerosis lesions that appear different from each other on T1-weighted images. These quantitative diffusion differences imply microstructural differences, which may prove useful in documenting irreversible disease.

Oxidative damage to mitochondrial DNA and activity of mitochondrial enzymes in chronic active lesions of multiple sclerosis

Soluble products of activated immune cells include reactive oxygen species (ROS) and nitric oxide (NO) with a high potential to induce biochemical modifications and degenerative changes in areas of inflammation in the central nervous system (CNS). Previously, we demonstrated an increased production of ROS by activated mononuclear cells (MNC) of patients with multiple sclerosis (MS) compared to those of controls, and development of oxidative damage to total DNA in association with inflammation in chronic active plaques. The current study aimed to determine whether mitochondrial (mt)DNA is affected by oxidative damage, and whether oxidative damage to mitochondrial macromolecules (including mtDNA) is associated with a decline in the activity of mitochondrial enzyme complexes. Using molecular and biochemical methods we demonstrate a trend for impaired NADH dehydrogenase (DH) activity and a possible compensatory increase in complex IV activity in association with oxidative damage to mtDNA in chronic active plaques. Immunohistochemistry confirms the increase of oxidative damage to DNA predominantly located in the cytoplasmic compartment of cells in chronic active plaques. These observations suggest that oxidative damage to macromolecules develops in association with inflammation in the CNS, and may contribute to a decline of energy metabolism in affected cells. As observed in neurodegenerative diseases of non-inflammatory origin, decreased ATP synthesis can ultimately lead to cell death or degeneration. Therefore, elucidation of this pathway in MS deserves further studies which may identify neuroprotective strategies to prevent tissue degeneration and the associated clinical disability.

Effect of midthoracic spinal cord constriction on catalytic nitric oxide synthase activity in the white matter columns of rabbit

The distribution and changes of catalytic nitric oxid synthase (cNOS) activity in the dorsal, lateral and ventral white matter columns at midthoracic level of the rabbit's spinal cord were studied in a model of surgically-induced spinal cord constriction performed at Th7 segment level and compared with the occurrence of nicotinamide adenine dinucleotide phosphate diaphorase expressing and neuronal nitric oxide synthase immunoreactive axons in the white matter of the control thoracic segments. Segmental and white-column dependent differences of cNOS activity were found in the dorsal (141.5 +/- 4.2 dpm/microm protein), lateral (87.3 +/- 11.5 dpm/microm protein) and ventral (117.1 +/- 7.6 dpm/microm protein) white matter columns in the Th5-Th6 segments and in the dorsal (103.3 +/- 15.5 dpm/microm protein), lateral (54.9 +/- 4.9 dpm/microm protein), and ventral (86.1 +/- 6.8 dpm/microm protein) white matter columns in the Th8-Th9 segments. A surgically-induced constriction of Th7 segment caused a disproportionate response of cNOS activity in the rostrally (Th5-Th6) and caudally (Th8-Th9) located segments in both lateral and ventral white matter columns. While a statistically significant decrease of cNOS activity was detected above the constriction site in the ventral columns, a considerable, statistically significant increase of cNOS activity was noted in the white lateral columns below the site of constriction. It is reasoned that the changes of cNOS activity may have adverse effects on nitric oxide (NO) production in the white matter close to the site of constriction injury, thus broadening the scope of the secondary mechanisms that play a role in neuronal trauma.

Inhibition of experimental allergic encephalomyelitis in the Lewis rat by paclitaxel

Experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), is useful for preclinical testing for agents to be considered for treatment for this human demyelinating disease. Microtubules in lymphocytes play an important role in the cascade of human T cell activation, and paclitaxel (PTX), a microtubule stabilizer, can inhibit T cell function. A new formulation of micellar PTX, free of Cremophor and ethanol, was tested for its effect on the induction of EAE in Lewis rats. Adoptive EAE was induced with an encephalitogenic T cell line activated with guinea pig myelin basic protein (GP MBP) peptide 68-88. PTX (10 mg/kg) was administered 24 and 72 h after cell transfer. The clinical signs, fulminating in controls, were completely blocked by PTX, but mild CNS inflammation remained unaltered. A similar dose of PTX, given on days 6 and 8 to animals developing active EAE after immunization with GP MBP peptide 68-88 in complete Freund's adjuvant, greatly reduced the severity of paralysis and delayed the onset of disease by 8-9 days. Marked weight loss and severe toxicity were noted with higher and more prolonged administration. In vitro micellar PTX inhibited activation of encephalitogenic T cells by both specific antigen and mitogen. Lower doses and longer treatment programs may provide effective treatment with acceptable adverse effects with this agent in the treatment of inflammatory demyelinating disease.

Extensive injury of descending neurons demonstrated by retrograde labeling in a virus-induced murine model of chronic inflammatory demyelination

Persistent Theiler's virus infection of SJL/J mice was used as a model to quantitatively assess the extent of descending neuron injury by chronic inflammatory demyelination of the spinal cord. By 9 months postinfection, inflammatory demyelinating lesions were present throughout the spinal cord, affecting up to 31% of the cross-sectional area of the ventrolateral columns. Axon dropout was evident in the lesions by electron microscopy and by quantitation of axons in normal-appearing white matter. Axon number in the ventrolateral columns at L1/L2 was reduced by 23% and total axon area was reduced by 37%, compared with uninfected mice. The most informative data on descending neuron injury, however, was a reduction in retrograde. Fluoro-Gold labeling. Labeling from T11/T12 of rubrospinal, reticulospinal/raphespinal, and vestibulospinal neurons was reduced by 60%, 70%, and 93%, respectively. Retrograde responses to axonal injury were observed, consisting of atrophied cell bodies, indented nuclei, and abundant lipofuscin, but cell body dropout was minimal. The number of cell bodies of vestibulospinal neurons was reduced by only 35%, whereas the number of cell bodies of rubrospinal neurons was unchanged. These results demonstrate that chronic inflammatory demyelination can severely injure axons and emphasize the need to design neuroprotective therapies in human multiple sclerosis.

Multiple sclerosis: magnetization transfer histogram analysis of segmented normal-appearing white matter

PURPOSE

To investigate and characterize the global distribution of magnetization transfer (MT) ratio values of normal-appearing white matter (NAWM) in patients with relapsing-remitting multiple sclerosis (MS) and test the hypothesis that the MT histogram for NAWM reflects disease progression.

MATERIALS AND METHODS

Conventional and MT magnetic resonance (MR) images were obtained in 23 patients and 25 healthy volunteers. Clinical tests for comparison with the MT histogram parameters included the Extended Disability Status Scale and the ambulation index. Lesion load calculated with T2-weighted MR images and whole-brain and white matter volumes were measured.

RESULTS

The location of the MT histogram peak and the mean MT ratio for NAWM were significantly lower in patients with MS than in control subjects. In longitudinal studies, the histogram peak location and mean MT ratio shifted in the direction of normal values as the duration of disease increased. A mean of 26.5% of the volume of new lesions identified on the later studies were demonstrated to have originated in NAWM corresponding to "lost" pixels on the histogram.

CONCLUSION

MT histogram analysis of NAWM, including longitudinal analysis, may provide new prognostic information regarding lesion formation and increase understanding of the course of the disease.

Extended observations on MS patients treated with IM interferon-beta1a (Avonex): implications for modern MS trials and therapeutics

Extended observations of the pivotal phase III clinical trial of interferon-beta1a (IFNbeta1a; Avonex, Biogen) in relapsing MS patients revealed that: (1) active treatment significantly slowed the accumulation of physical disability over time, reduced clinical exacerbations and MRI brain lesions; (2) clinical efficacy did not depend on disability endpoints; (3) active treatment benefited multiple MRI measures of brain lesions; (4) cerebral atrophy occurred over 2 years in relatively mildly disabled patients; and (5) Avonex could slow the development of atrophy after the first year of treatment. Data from this study were recently used to design a new outcome measure for MS clinical trials (the Multiple Sclerosis Functional Composite), and was also the basis for two ongoing studies of IFNbeta1a: one in patients with monosymptomatic onset of MS and the other in secondary progressive MS.

The neuroprotective effect of inflammation: implications for the therapy of multiple sclerosis

Autoreactive T cells are a component of the normal immune system. It has been proposed that some of these autoreactive T cells even have a protective function. Recent studies support this notion by demonstrating that (a) myelin basic-protein (MBP-) specific T cells show neuroprotective effects in vivo, and (b) activated antigen-specific human T cells and other immune cells produce bioactive brain-derived neurotrophic factor (BDNF) in vitro. Furthermore, BDNF is expressed in different types of inflammatory cells in brain lesions of patients with acute disseminated leukoencephalopathy or multiple sclerosis. We postulate that the neuroprotective effect of T cells and other immune cells observed in vivo is at least partially mediated by BDNF and other neurotrophic factors. The concept of neuroprotective autoimmunity has obvious implications for the therapy of multiple sclerosis and other neuroimmunological diseases.

Restricted immune responses lead to CNS demyelination and axonal damage

Although autoreactive T-cells have a pivotal role in initiating the inflammatory process in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS), recent evidence suggests a relevant role for autoantibodies specific for myelin proteins as well. To examine the role of B-cells in the cerebrospinal fluid of patients with MS, we analyzed the V(H) gene usage in ten MS patients by PCR technologies. Analysis of HCDR3 length revealed an oligoclonal accumulation of B-cells. Sequence analysis of the V(H)3 and V(H)4 gamma transcripts of two MS individuals demonstrated that this accumulation was related to the expansion and somatic diversification of a limited groups of B-cell clones. These findings are indicative of a chronic and intense antigenic stimulation occurring in the CNS. Animal models, such as EAE, are of particular importance in order to elucidate the pathogenetic effector mechanisms in autoimmune demyelination. In a non-human primate model of EAE, we describe that the immunodominant T-cell epitope is presented exclusively by a monomorphic DRB1 allele, suggesting that susceptibility to EAE may be linked to this unique restriction and, therefore, providing a possible mechanism for MHC linkage to diseases. Moreover, we report on the presence of inflammation, sharp demyelination and axonal damage in EAE induced with whole myelin as well as with recombinant myelin oligodendrocyte glycoprotein (MOG), but not with myelin basic protein alone. The presence of axonal pathology was supported by immunohistochemistry with anti-amyloid precursor protein and anti-non phosphorilated neurofilaments monoclonal antibodies within early active demyelinated plaques. These findings suggest that axonal damage may be an early event in the pathogenesis of autoimmune demyelinating diseases of the CNS and highlights the importance of animal models in which therapies targeting repair and axonal survival may be exploited.

The effect of gadolinium-enhancing lesions on whole brain atrophy in relapsing-remitting MS

OBJECTIVE

To determine the relationship between gadolinium-enhancing lesions and changes in whole brain parenchymal volume in patients with relapsing-remitting MS, and to test the hypothesis that gadolinium enhancement is a predictor of whole brain atrophy.

METHODS

Twenty-four patients with clinically definite MS were imaged over 2 years. A computer-assisted segmentation technique based on high-resolution MRI was used to quantify gadolinium-enhancing T1 lesion volume and brain parenchyma and CSF volumes. Percent brain parenchymal volume (PBV) relative to the total intracranial volume was calculated, and changes in PBV were used to represent the degree of whole brain atrophy over 2 years.

RESULTS

PBV at baseline was dependent on duration of MS, and a significant decrease in PBV was observed over the course of the study. Changes in enhanced T1 lesion load failed to correlate with changes in PBV, and multiple regression analyses determined that enhanced T1 lesion load at baseline was not a significant predictor of subsequent change in PBV.

CONCLUSIONS

MR visible inflammation as demonstrated by enhanced T1 lesions is not a significant factor in the pathogenesis of whole brain atrophy in relapsing-remitting MS, suggesting that a more global pathologic process is responsible for the loss of brain parenchymal volume.

Multiple sclerosis and chronic autoimmune encephalomyelitis: a comparative quantitative study of axonal injury in active, inactive, and remyelinated lesions

Recent magnetic resonance (MR) studies of multiple sclerosis lesions indicate that axonal injury is a major correlate of permanent clinical deficit. In the present study we systematically quantified acute axonal injury, defined by immunoreactivity for beta-amyloid-precursor-protein in dystrophic neurites, in the central nervous system of 22 multiple sclerosis patients and 18 rats with myelin-oligodendrocyte glycoprotein (MOG)-induced chronic autoimmune encephalomyelitis (EAE). The highest incidence of acute axonal injury was found during active demyelination, which was associated with axonal damage in periplaque and in the normal appearing white matter of actively demyelinating cases. In addition, low but significant axonal injury was also observed in inactive demyelinated plaques. In contrast, no significant axonal damage was found in remyelinated shadow plaques. The patterns of axonal pathology in chronic active EAE were qualitatively and quantitatively similar to those found in multiple sclerosis. Our studies confirm previous observations of axonal destruction in multiple sclerosis lesions during active demyelination, but also indicate that ongoing axonal damage in inactive lesions may significantly contribute to the clinical progression of the disease. The results further emphasize that MOG-induced EAE may serve as a suitable model for testing axon-protective therapies in inflammatory demyelinating conditions.

Pathogenesis of axonal degeneration: parallels between Wallerian degeneration and vincristine neuropathy

Peripheral neuropathies and Wallerian degeneration share a number of pathological features; the most prominent of which is axonal degeneration. We asked whether common pathophysiologic mechanisms are involved in these 2 disorders by directly comparing in vitro models of axonal degeneration after axotomy or exposure to the neurotoxin vincristine. Embryonic rat dorsal root ganglia (DRG) were allowed to extend neurites for 5 days in culture, and then were either axotomized or exposed to 0.01 microM vincristine. Neurites universally degenerated by 3 days after axotomy or after 6 days of vincristine exposure. The neuroprotective effects of a low calcium environment or pharmacologic inhibition of the cysteine protease calpain were compared in these 2 models of axonal degeneration. Addition of EGTA or growth in zero-calcium media provided significant protection against axonal degeneration after either axotomy or vincristine exposure. Treatment with the experimental calpain inhibitor AK295 was equally protective in both models. Chronic exposure to AK295 was not toxic to the cultures. These data suggest that common mechanisms involving calcium and calpains are involved in both axotomy-induced and vincristine-induced axonal degeneration. In addition, calpain inhibition may provide a strategy for preventing axonal degeneration and preserving neurologic function in a variety of PNS and CNS disorders.

Recombinant human interferon beta in relapsing-remitting multiple sclerosis: a review of the major clinical trials

The beneficial effects of interferon beta (IFN-beta) on disease activity in relapsing-remitting multiple sclerosis (RRMS) have been confirmed in several clinical trials. Three IFN-beta products are currently available and licensed for use in RRMS at different dosages and with different routes of administration. For the prescribing physician, therefore, questions remain about the effect these differences may have on the success of therapy. This paper reviews the four large placebo-controlled clinical trials that have been conducted with IFN-beta in patients with RRMS. The evidence available indicates that optimal results are likely to be achieved with the highest tolerable dosage of IFN-beta. Furthermore, as inflammatory brain lesions in MS have been shown to exhibit more extensive and early axonal damage than previously suspected, early treatment may be advisable in order to delay disease progression in RRMS.