Identification of Unique microRNA Profiles in Different Types of Idiopathic Inflammatory Myopathy

Dermatomyositis (DM), antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM) are four major types of idiopathic inflammatory myopathy (IIM). Muscle biopsies from each type of IIM have unique transcriptomic profiles. MicroRNAs (miRNAs) target messenger RNAs (mRNAs), thereby regulating their expression and modulating transcriptomic profiles. In this study, 18 DM, 12 IMNM, 6 AS, 6 IBM, and 6 histologically normal muscle biopsies underwent miRNA profiling using the NanoString nCounter system. Eleven miRNAs were exclusively differentially expressed in DM compared to controls, seven miRNAs were only differentially expressed in AS, and nine miRNAs were specifically upregulated in IBM. No differentially expressed miRNAs were identified in IMNM. We also analyzed miRNA-mRNA associations to identify putative targets of differentially expressed miRNAs. In DM and AS, these were predominantly related to inflammation and cell cycle progression. Moreover, our analysis showed an association between miR-30a-3p, miR-30e-3p, and miR-199b-5p downregulation in DM and the upregulation of target genes induced by type I interferon. In conclusion, we show that muscle biopsies from DM, AS, and IBM patients have unique miRNA signatures and that these miRNAs might play a role in regulating the expression of genes known to be involved in IIM pathogenesis.

The pattern of MHC class I expression in muscle biopsies from patients with myositis and other neuromuscular disorders

OBJECTIVE

Diagnostic muscle biopsies are routinely immunostained for major histocompatibility complex class I (MHC-I) protein. In this study we analysed the prevalence and patterns of MHC-I immunostaining in biopsies from patients with different types of myopathies and neurogenic disorders.

METHODS

All 357 diagnostic muscle biopsies processed at the Johns Hopkins Neuromuscular Pathology Laboratory from August 2013 to January 2017 were immunostained for MHC-I. The prevalence and patterns of MHC-I immunostaining were compared between patients with histologically normal muscle biopsies (n = 31), idiopathic inflammatory myopathies (IIMs; n = 170), non-inflammatory myopathies (n = 60) and neurogenic disorders (n = 96).

RESULTS

MHC-I immunostaining was abnormal in most patients with DM (98%), sporadic IBM (sIBM; 100%), immune-mediated necrotizing myopathy (IMNM; 100%) and polymyositis (77%). In contrast, MHC-I immunostaining was less frequently present in non-inflammatory myopathies (32%) or neurogenic disorders (30%). Overall, abnormal MHC-I immunostaining had a sensitivity of 0.95 and a specificity of 0.82 for diagnosing IIMs. A focal MHC-I staining pattern was associated with IMNM, whereas a global pattern was more prevalent in sIBM and a perifascicular pattern was significantly more common in dermatomyositis. Among 18 DM biopsies without perifascicular atrophy, 50% had a perifascicular MHC-I staining pattern. Sarcoplasmic upregulation staining was more common than sarcolemmal staining across all groups.

CONCLUSION

MHC-I immunostaining was useful to distinguish IIMs from non-inflammatory myopathies or neurogenic disorders. Of note, a perifascicular MHC-I staining pattern was present only in those with DM, including half of those without perifascicular atrophy; many of these biopsies may not otherwise have been diagnostic for DM.

Loss of TDP-43 function and rimmed vacuoles persist after T cell depletion in a xenograft model of sporadic inclusion body myositis

Sporadic inclusion body myositis (IBM) is the most common acquired muscle disease in adults over age 50, yet it remains unclear whether the disease is primarily driven by T cell–mediated autoimmunity. IBM muscle biopsies display nuclear clearance and cytoplasmic aggregation of TDP-43 in muscle cells, a pathologic finding observed initially in neurodegenerative diseases, where nuclear loss of TDP-43 in neurons causes aberrant RNA splicing. Here, we show that loss of TDP-43–mediated splicing repression, as determined by inclusion of cryptic exons, occurs in skeletal muscle of subjects with IBM. Of 119 muscle biopsies tested, RT-PCR–mediated detection of cryptic exon inclusion was able to diagnose IBM with 84% sensitivity and 99% specificity. To determine the role of T cells in pathogenesis, we generated a xenograft model by transplanting human IBM muscle into the hindlimb of immunodeficient mice. Xenografts from subjects with IBM displayed robust regeneration of human myofibers and recapitulated both inflammatory and degenerative features of the disease. Myofibers in IBM xenografts showed invasion by human, oligoclonal CD8+ T cells and exhibited MHC-I up-regulation, rimmed vacuoles, mitochondrial pathology, p62-positive inclusions, and nuclear clearance and cytoplasmic aggregation of TDP-43, associated with cryptic exon inclusion. Reduction of human T cells within IBM xenografts by treating mice intraperitoneally with anti-CD3 (OKT3) suppressed MHC-I up-regulation. However, rimmed vacuoles and loss of TDP-43 function persisted. These data suggest that T cell depletion does not alter muscle degenerative pathology in IBM.

Prevalence of heart disease in patients with mitochondrial abnormalities on skeletal muscle biopsy

Objective

Mitochondrial DNA mutations are associated with an increased risk of heart disease. Whether an increased prevalence of cardiovascular disease is present in patients presenting with mitochondrial abnormalities on skeletal muscle biopsy remains unknown. This study was designed to determine the prevalence of cardiac conduction disease and structural heart disease in patients presenting with mitochondrial abnormalities on skeletal muscle biopsy.

Methods

This is a retrospective cohort study of 103 patients with mitochondrial abnormalities on skeletal muscle biopsy who were referred for evaluation of muscle weakness at a single tertiary care referral center from 2012 to 2018. Of these patients, 59 (57.3%) had an electrocardiogram available and were evaluated for the presence of conduction disease. An echocardiogram was available in 43 patients (42%) who were evaluated for the presence of structural heart disease. The prevalence of cardiac disease was compared to control cohort populations (Framingham and the Atherosclerosis Risk in Communities, ARIC cohorts).

Results

Mitochondrial abnormalities associated with cardiac conduction disease (defined as QRS duration ≥ 120 msec) were present in 8.9%, versus 2.0% (p < 0.001) in the Framingham population and 2.6% (p = 0.003) in the ARIC cohort. LV systolic dysfunction (LVEF ≤ 50%) was present in 11.6%, versus 3.6% (p < 0.01) in the Framingham and 3% (p < 0.01) in the ARIC populations. Left ventricular hypertrophy was present in 28.6%, versus 13.6% (p < 0.02) in the Framingham and 10.4% (p < 0.001) in the ARIC populations.

Interpretation

Given the increased prevalence of cardiovascular disease, patients with mitochondrial abnormalities on skeletal muscle biopsy should undergo routine cardiac screening with physical exam, electrocardiography, and cardiac imaging.

Machine learning algorithms reveal unique gene expression profiles in muscle biopsies from patients with different types of myositis

OBJECTIVES

Myositis is a heterogeneous family of diseases that includes dermatomyositis (DM), antisynthetase syndrome (AS), immune-mediated necrotising myopathy (IMNM), inclusion body myositis (IBM), polymyositis and overlap myositis. Additional subtypes of myositis can be defined by the presence of myositis-specific autoantibodies (MSAs). The purpose of this study was to define unique gene expression profiles in muscle biopsies from patients with MSA-positive DM, AS and IMNM as well as IBM.

METHODS

RNA-seq was performed on muscle biopsies from 119 myositis patients with IBM or defined MSAs and 20 controls. Machine learning algorithms were trained on transcriptomic data and recursive feature elimination was used to determine which genes were most useful for classifying muscle biopsies into each type and MSA-defined subtype of myositis.

RESULTS

The support vector machine learning algorithm classified the muscle biopsies with >90% accuracy. Recursive feature elimination identified genes that are most useful to the machine learning algorithm and that are only overexpressed in one type of myositis. For example, CAMK1G (calcium/calmodulin-dependent protein kinase IG), EGR4 (early growth response protein 4) and CXCL8 (interleukin 8) are highly expressed in AS but not in DM or other types of myositis. Using the same computational approach, we also identified genes that are uniquely overexpressed in different MSA-defined subtypes. These included apolipoprotein A4 (APOA4), which is only expressed in anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) myopathy, and MADCAM1 (mucosal vascular addressin cell adhesion molecule 1), which is only expressed in anti-Mi2-positive DM.

CONCLUSIONS

Unique gene expression profiles in muscle biopsies from patients with MSA-defined subtypes of myositis and IBM suggest that different pathological mechanisms underly muscle damage in each of these diseases.

More prominent muscle involvement in patients with dermatomyositis with anti-Mi2 autoantibodies

OBJECTIVE

To define the clinical phenotype of dermatomyositis (DM) with anti-Mi2 autoantibodies.

METHODS

In this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up in patients with anti-Mi2-positive DM were compared to patients with anti-Mi2-negative DM, antisynthetase syndrome (AS), and immune-mediated necrotizing myopathy (IMNM). Longitudinal anti-Mi2 autoantibody titers were assessed.

RESULTS

A total of 58 patients with anti-Mi2-positive DM, 143 patients with anti-Mi2-negative DM, 162 patients with AS, and 170 patients with IMNM were included. Among patients with anti-Mi2-positive DM, muscle weakness was present in 60% at disease onset and occurred in 98% during longitudinal follow-up; fewer patients with anti-Mi2-negative DM developed weakness (85%; p = 0.008). Patients with anti-Mi2-positive DM were weaker and had higher creatine kinase (CK) levels than patients with anti-Mi2-negative DM or patients with AS. Muscle biopsies from patients with anti-Mi2-positive DM had prominent necrosis. Anti-Mi2 autoantibody levels correlated with CK levels and strength (p < 0.001). With treatment, most patients with anti-Mi2-positive DM had improved strength and CK levels; among 10 with multiple serum samples collected over 4 or more years, anti-Mi2 autoantibody titers declined in all and normalized in 3, 2 of whom stopped immunosuppressant treatment and never relapsed. Patients with anti-Mi2-positive DM had less calcinosis (9% vs 28%; p = 0.003), interstitial lung disease (5% vs 16%; p = 0.04), and fever (7% vs 21%; p = 0.02) than did patients with anti-Mi2-negative DM.

CONCLUSIONS

Patients with anti-Mi2-positive DM have more severe muscle disease than patients with anti-Mi2-negative DM or patients with AS. Anti-Mi2 autoantibody levels correlate with disease severity and may normalize in patients who enter remission.

Identification of distinctive interferon gene signatures in different types of myositis

OBJECTIVE

Activation of the type 1 interferon (IFN1) pathway is a prominent feature of dermatomyositis (DM) muscle and may play a role in the pathogenesis of this disease. However, the relevance of the IFN1 pathway in patients with other types of myositis such as the antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM) is largely unknown. Moreover, the activation of the type 2 interferon (IFN2) pathway has not been comprehensively explored in myositis. In this cross-sectional study, our objective was to determine whether IFN1 and IFN2 pathways are differentially activated in different types of myositis by performing RNA sequencing on muscle biopsy samples from 119 patients with DM, IMNM, AS, or IBM and on 20 normal muscle biopsies.

METHODS

The expression of IFN1- and IFN2-inducible genes was compared between the different groups.

RESULTS

The expression of IFN1-inducible genes was high in DM, moderate in AS, and low in IMNM and IBM. In contrast, the expression of IFN2-inducible genes was high in DM, IBM, and AS but low in IMNM. The expression of IFN-inducible genes correlated with the expression of genes associated with inflammation and muscle regeneration. Of note, ISG15 expression levels alone performed as well as composite scores relying on multiple genes to monitor activation of the IFN1 pathway in myositis muscle biopsies.

CONCLUSIONS

IFN1 and IFN2 pathways are differentially activated in different forms of myositis. This observation may have therapeutic implications because immunosuppressive medications may preferentially target each of these pathways.

Myositis Autoantigen Expression Correlates With Muscle Regeneration but Not Autoantibody Specificity

OBJECTIVE

Although more than a dozen myositis-specific autoantibodies (MSAs) have been identified, most patients with myositis are positive for a single MSA. The specific overexpression of a given myositis autoantigen in myositis muscle has been proposed as initiating and/or propagating autoimmunity against that particular autoantigen. The present study was undertaken to test this hypothesis.

METHODS

In order to quantify autoantigen RNA expression, RNA sequencing was performed on muscle biopsy samples from control subjects, MSA-positive patients with myositis, regenerating mouse muscles, and cultured human muscle cells.

RESULTS

Muscle biopsy samples were available from 20 control subjects and 106 patients with autoantibodies recognizing hydroxymethylglutaryl-coenzyme A reductase (n = 40), signal recognition particles (n = 9), Jo-1 (n = 18), nuclear matrix protein 2 (n = 12), Mi-2 (n = 11), transcription intermediary factor 1γ (n = 11), or melanoma differentiation-associated protein 5 (n = 5). The increased expression of a given autoantigen in myositis muscle was not associated with autoantibodies recognizing that autoantigen (all q > 0.05). In biopsy specimens from both myositis muscle and regenerating mouse muscles, autoantigen expression correlated directly with the expression of muscle regeneration markers and correlated inversely with the expression of genes encoding mature muscle proteins. Myositis autoantigens were also expressed at high levels in cultured human muscle cells.

CONCLUSION

Most myositis autoantigens are highly expressed during muscle regeneration, which may relate to the propagation of autoimmunity. However, factors other than overexpression of specific autoantigens are likely to govern the development of unique autoantibodies in individual patients with myositis.

Muscular and extramuscular features of myositis patients with anti-U1-RNP autoantibodies

OBJECTIVE

To define the clinical phenotype of patients with myositis with anti-U1-ribonucleoprotein (RNP) autoantibodies.

METHODS

In this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up in patients with anti-U1-RNP-positive myositis were compared to those with dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), and the antisynthetase syndrome (AS).

RESULTS

Twenty anti-U1-RNP-positive patients, 178 patients with DM, 135 patients with IMNM, and 132 patients with AS were included. Anti-U1-RNP-positive patients were younger (∼37 years) and more likely to be black (60%) than patients with AS, DM, or IMNM. Muscle weakness was a presenting feature in 15% of anti-U1-RNP-positive patients; 80% eventually developed weakness. Four of 7 anti-U1-RNP-positive patients had necrotizing muscle biopsies. Arthritis occurred in 60% of anti-U1-RNP-positive patients; this was increased compared to DM (18%) or IMNM (6%) (all p < 0.01). DM-specific skin features developed in 60% of anti-U1-RNP-positive patients. Interstitial lung disease (ILD) occurred in 45% of anti-U1-RNP-positive patients; fewer patients with DM (13%) and IMNM (6%) and more patients with AS (80%) developed ILD (all p < 0.01). Glomerulonephritis and pericarditis occurred in 25% and 40% of anti-U1-RNP-positive patients, respectively, but rarely in the other groups; these features occurred only in those with coexisting anti-Ro52 autoantibodies. No anti-U1-RNP patient had cancer-associated myositis or died during the study period.

CONCLUSIONS

Patients with anti-U1-RNP myositis typically present with proximal weakness and necrotizing muscle biopsies. Arthritis, dermatitis, and ILD are the most common extramuscular clinical features. Pericarditis and glomerulonephritis are uniquely found in patients with anti-U1-RNP-positive myositis.

Muscular and extramuscular clinical features of patients with anti-PM/Scl autoantibodies

OBJECTIVE

To define the clinical features of myositis patients with anti-PM/Scl-75 and/or anti-PM/Scl-100 autoantibodies at disease onset and during the course of disease and compare them to patients with other forms of myositis.

METHODS

In this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up were compared between anti-PM/Scl-positive patients and those with the antisynthetase syndrome (AS), dermatomyositis (DM), and immune-mediated necrotizing myopathy (IMNM).

RESULTS

Forty-one anti-PM/Scl-positive, 132 AS, 178 DM, and 135 IMNM patients were included. Although muscle weakness was a presenting feature in just 37% of anti-PM/Scl-positive patients, 93% eventually developed weakness. Unlike the other groups, anti-PM-Scl-positive patients had more severe weakness in arm abductors than hip flexors. Interstitial lung disease was a presenting feature in just 10% of anti-PM/Scl-positive patients, but occurred in 61% during follow-up; fewer patients with DM (13%, p < 0.001) and IMNM (6%, p < 0.001) and more patients with AS (80%, p < 0.05) developed interstitial lung disease during the course of disease. Mechanic's hands (80%), Raynaud syndrome (78%), sclerodactyly (66%), telangiectasias (66%), esophageal reflux disease (61%), subcutaneous edema (46%), puffy hands (39%), and calcinosis (39%) occurred more frequently in anti-PM/Scl-positive patients than in the other groups. Although 30% of anti-PM/Scl-positive patients met criteria for systemic sclerosis, less than 5% had renal crisis or finger ulcerations. No differences were found between patients with only anti-PM/Scl-100 or only anti-PM/Scl-75 autoantibodies.

CONCLUSIONS

Unlike patients with DM, AS, or IMNM, anti-PM/Scl-positive patients have weaker arm abductors than hip flexors. Anti-PM/Scl-positive patients also have the most extensive extramuscular features.

Association of Fibrosing Myopathy in Systemic Sclerosis and Higher Mortality

OBJECTIVE

To determine if a unique subtype of scleroderma muscle disease exists by comparing the clinical features of systemic sclerosis (SSc; scleroderma) patients with predominant fibrosis on muscle biopsy to those with inflammatory muscle histopathology.

METHODS

This retrospective, cross-sectional study included SSc patients with muscle weakness and an available muscle biopsy. Biopsies with fibrosis but without inflammation/necrosis were designated as "fibrosing myopathy," and those with inflammation and/or necrosis were assigned a category of "inflammatory myopathy." Clinical data, including features of SSc, serum creatine kinase (CK) levels, electromyography, autoantibody profile, and survival, were compared between the 2 groups.

RESULTS

The study population consisted of 37 weak SSc patients, 8 with fibrosing myopathy and 29 with inflammatory myopathy. Compared to those with inflammatory myopathy, patients with fibrosing myopathy were more likely to have diffuse SSc skin subtype (87% versus 62%; P = 0.18), African American race (62.5% versus 37.9%; P = 0.20), and a lower mean ± SD forced vital capacity (55.5 ± 31.9 versus 66.4 ± 17.6; P = 0.23). They also had lower mean ± SD CK values (516 ± 391 versus 2,477 ± 3,511 IU/liter; P = 0.007) and lower aldolase values (13.8 ± 4.7 versus 27.3 ± 4.7; P = 0.01). Patients with fibrosing myopathy had a significantly higher mortality (5 of 8 [62.5%] versus 4 of 29 [14.3%]; P = 0.005).

CONCLUSION

Fibrosing myopathy is a unique histologic subtype of muscle disease among weak patients with SSc and is associated with significantly worse mortality compared to those with inflammation and/or necrosis on muscle biopsy.

Inflammatory myopathy associated with anti-mitochondrial antibodies: A distinct phenotype with cardiac involvement

OBJECTIVE

In the context of clinical evaluations performed on our prospective myositis cohort, we noted a striking association of severe cardiac disease in myositis patients with anti-mitochondrial antibodies. We sought to review all cases of anti-mitochondrial antibody (AMA) associated myositis in our cohort to describe the clinical features of this disease subset.

METHODS

We identified 7 patients with confirmed anti-mitochondrial antibodies who presented as an inflammatory myopathy. A retrospective chart review was completed to assess their clinical presentation, laboratory, imaging, electrophysiologic, and histopathologic features.

RESULTS

One patient presented with dermatomyositis and 6 were classified as polymyositis using Bohan and Peter criteria. In all but one patient, a chronic course of muscle involvement was appreciated with an average of 6.5 years of weakness prior to presentation. Muscle atrophy was often noted, as well as atypical findings of scapular winging in 2 of the patients. Muscle biopsies were consistent with immune-mediated necrotizing myopathy in 4 patients, dermatomyositis in 1, polymyositis in 1 and nonspecific or granulomatous myositis in 1 patient. Changes pointing to mitochondrial alterations were seen in 2 of the 7 patients. Cardiac involvement (including myocarditis, atrial and ventricular arrhythmias, and cardiomyopathy), was seen in 5 out of 7 (71%) of the patients, and usually preceded the muscle involvement. Coexisting autoimmune conditions were seen in 3/7of the patients and included primary biliary cirrhosis, autoimmune hepatitis, psoriasis, and Hashimoto's thyroiditis.

CONCLUSIONS

Anti-mitochondrial antibodies identify a distinct inflammatory myopathy phenotype that is frequently associated with chronic skeletal muscle disease and severe cardiac involvement. Early recognition of this rare entity as an immune-mediated process is important due to implications for treatment. We propose that anti-mitochondrial antibody status should be determined in patients with a compatible clinical picture.

Calcium dysregulation, functional calpainopathy, and endoplasmic reticulum stress in sporadic inclusion body myositis

Sporadic inclusion body myositis (IBM) is the most common primary myopathy in the elderly, but its pathoetiology is still unclear. Perturbed myocellular calcium (Ca²⁺) homeostasis can exacerbate many of the factors proposed to mediate muscle degeneration in IBM, such as mitochondrial dysfunction, protein aggregation, and endoplasmic reticulum stress. Ca²⁺ dysregulation may plausibly be initiated in IBM by immune-mediated membrane damage and/or abnormally accumulating proteins, but no studies to date have investigated Ca²⁺ regulation in IBM patients. We first investigated protein expression via immunoblot in muscle biopsies from IBM, dermatomyositis, and non-myositis control patients, identifying several differentially expressed Ca²⁺-regulatory proteins in IBM. Next, we investigated the Ca²⁺-signaling transcriptome by RNA-seq, finding 54 of 183 (29.5%) genes from an unbiased list differentially expressed in IBM vs. controls. Using an established statistical approach to relate genes with causal transcription networks, Ca²⁺ abundance was considered a significant upstream regulator of observed whole-transcriptome changes. Post-hoc analyses of Ca²⁺-regulatory mRNA and protein data indicated a lower protein to transcript ratio in IBM vs. controls, which we hypothesized may relate to increased Ca²⁺-dependent proteolysis and decreased protein translation. Supporting this hypothesis, we observed robust (4-fold) elevation in the autolytic activation of a Ca²⁺-activated protease, calpain-1, as well as increased signaling for translational attenuation (eIF2α phosphorylation) downstream of the unfolded protein response. Finally, in IBM samples we observed mRNA and protein under-expression of calpain-3, the skeletal muscle-specific calpain, which broadly supports proper Ca²⁺ homeostasis. Together, these data provide novel insight into mechanisms by which intracellular Ca²⁺ regulation is perturbed in IBM and offer evidence of pathological downstream effects.

Spectrum of Muscle Histopathologic Findings in Forty-Two Scleroderma Patients With Weakness

OBJECTIVE

To determine if distinct muscle pathologic features exist in scleroderma subjects with weakness.

METHODS

This retrospective study included weak scleroderma subjects with muscle biopsies available for review. Biopsies were systematically assessed for individual pathologic features, including inflammation, necrosis, fibrosis, and acute neurogenic atrophy. Based on the aggregate individual features, biopsies were assigned a histopathologic category of polymyositis, dermatomyositis, necrotizing myopathy, nonspecific myositis, "acute denervation," "fibrosis only," or "other." Clinical data analyzed included autoantibody profiles, scleroderma subtype and disease duration, Medsger muscle severity scores, creatine kinase, electromyography, and muscle magnetic resonance imaging.

RESULTS

A total of 42 subjects (79% female and 64% diffuse scleroderma) were included in this study. Necrosis (67%), inflammation (48%), acute neurogenic atrophy (48%), and fibrosis (33%) were the most prevalent pathologic features. The presence of fibrosis was strongly associated with anti-PM-Scl antibodies. Histopathologic categories included nonspecific myositis (36%), necrotizing myopathy (21%), dermatomyositis (7%), "acute denervation" (7%), "fibrosis only" (7%), and polymyositis (5%). Disease duration of scleroderma at the time of muscle biopsy was shorter in polymyositis than other histopathologic categories. Patients with anti-PM-Scl and Scl-70 antibodies also had a shorter disease duration than those with other autoantibody profiles.

CONCLUSION

Nonspecific myositis and necrotizing myopathy were the most common histopathologic categories in weak scleroderma subjects. Surprisingly, nearly half of the subjects studied had histologic evidence of acute motor denervation (acute neurogenic atrophy); this has not been previously reported. Taken together, these observations suggest that a variety of pathologic mechanisms may underlie the development of myopathy in scleroderma.

The Prevalence of Individual Histopathologic Features Varies according to Autoantibody Status in Muscle Biopsies from Patients with Dermatomyositis

OBJECTIVE

Individual dermatomyositis (DM)-associated autoantibodies are associated with distinct clinical phenotypes. This study was undertaken to explore the association of these autoantibodies with specific muscle biopsy features.

METHODS

DM subjects with a muscle biopsy reviewed at Johns Hopkins had sera screened for autoantibodies recognizing Mi-2, transcriptional intermediary factor 1-γ (TIF1-γ), NXP2, MDA5, Ro52, PM-Scl, and Jo1. We also included anti-Jo1–positive patients with polymyositis (PM) who had a biopsy read at Johns Hopkins. Analyzed histological features included perifascicular atrophy, perivascular inflammation, mitochondrial dysfunction, primary inflammation, and myofiber necrosis. Duration of disease, biopsy location, and treatment at biopsy were also analyzed.

RESULTS

We studied 91 DM and 7 anti-Jo1–positive patients with PM. In univariate analyses, TIF1-γ+ patients had more mitochondrial dysfunction (47% vs 18%; p = 0.05), NXP2+ patients had less primary inflammation (0% vs 28%; p = 0.01), Mi-2+ patients had more primary inflammation (50% vs 19%; p = 0.03), and PM-Scl+ patients had more primary inflammation (67% vs 18%; p = 0.004) than those who were negative for each autoantibody. Although reliability was limited because of small sample numbers, multivariate analysis confirmed that TIF1-γ+ patients had more mitochondrial dysfunction [prevalence ratio (PR) 2.6, 95% CI 1.0–6.5, p = 0.05] and PM-Scl+ patients had more primary inflammation (PR 5.2, 95% CI 2.0–13.4; p = 0.001) independent of disease duration at biopsy, biopsy site, and treatment at biopsy. No differences in muscle biopsy features were noted between anti-Jo1–positive patients diagnosed with DM and PM.

CONCLUSION

The prevalence of different histological features varies according to autoantibody status in DM. Muscle biopsy features are similar in anti-Jo1 patients with and without a rash.

The Prevalence of Individual Histopathologic Features Varies according to Autoantibody Status in Muscle Biopsies from Patients with Dermatomyositis

Objective.

Individual dermatomyositis (DM)-associated autoantibodies are associated with distinct clinical phenotypes. This study was undertaken to explore the association of these autoantibodies with specific muscle biopsy features.

Methods.

DM subjects with a muscle biopsy reviewed at Johns Hopkins had sera screened for autoantibodies recognizing Mi-2, transcriptional intermediary factor 1-γ (TIF1-γ), NXP2, MDA5, Ro52, PM-Scl, and Jo1. We also included anti-Jo1–positive patients with polymyositis (PM) who had a biopsy read at Johns Hopkins. Analyzed histological features included perifascicular atrophy, perivascular inflammation, mitochondrial dysfunction, primary inflammation, and myofiber necrosis. Duration of disease, biopsy location, and treatment at biopsy were also analyzed.

Results.

We studied 91 DM and 7 anti-Jo1–positive patients with PM. In univariate analyses, TIF1-γ+ patients had more mitochondrial dysfunction (47% vs 18%; p = 0.05), NXP2+ patients had less primary inflammation (0% vs 28%; p = 0.01), Mi-2+ patients had more primary inflammation (50% vs 19%; p = 0.03), and PM-Scl+ patients had more primary inflammation (67% vs 18%; p = 0.004) than those who were negative for each autoantibody. Although reliability was limited because of small sample numbers, multivariate analysis confirmed that TIF1-γ+ patients had more mitochondrial dysfunction [prevalence ratio (PR) 2.6, 95% CI 1.0–6.5, p = 0.05] and PM-Scl+ patients had more primary inflammation (PR 5.2, 95% CI 2.0–13.4; p = 0.001) independent of disease duration at biopsy, biopsy site, and treatment at biopsy. No differences in muscle biopsy features were noted between anti-Jo1–positive patients diagnosed with DM and PM.

Conclusion.

The prevalence of different histological features varies according to autoantibody status in DM. Muscle biopsy features are similar in anti-Jo1 patients with and without a rash.

Sulfatide levels correlate with severity of neuropathy in metachromatic leukodystrophy

Objective

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disorder due to deficient activity of arylsulfatase A (ASA) that causes accumulation of sulfatide and lysosulfatide. The disorder is associated with demyelination and axonal loss in the central and peripheral nervous systems. The late infantile form has an early-onset, rapidly progressive course with severe sensorimotor dysfunction. The relationship between the degree of nerve damage and (lyso)sulfatide accumulation is, however, not established.

Methods

In 13 children aged 2–5 years with severe motor impairment, markedly elevated cerebrospinal fluid (CSF) and sural nerve sulfatide and lysosulfatide levels, genotype, ASA mRNA levels, residual ASA, and protein cross-reactive immunological material (CRIM) confirmed the diagnosis. We studied the relationship between (lyso)sulfatide levels and (1) the clinical deficit in gross motor function (GMFM-88), (2) median and peroneal nerve motor and median and sural nerve sensory conduction studies (NCS), (3) median and tibial nerve somatosensory evoked potentials (SSEPs), (4) sural nerve histopathology, and (5) brain MR spectroscopy.

Results

Eleven patients had a sensory-motor demyelinating neuropathy on electrophysiological testing, whereas two patients had normal studies. Sural nerve and CSF (lyso)sulfatide levels strongly correlated with abnormalities in electrophysiological parameters and large myelinated fiber loss in the sural nerve, but there were no associations between (lyso)sulfatide levels and measures of central nervous system (CNS) involvement (GMFM-88 score, SSEP, and MR spectroscopy).

Interpretation

Nerve and CSF sulfatide and lysosulfatide accumulation provides a marker of disease severity in the PNS only; it does not reflect the extent of CNS involvement by the disease process. The magnitude of the biochemical disturbance produces a continuously graded spectrum of impairments in neurophysiological function and sural nerve histopathology.

Laing distal myopathy pathologically resembling inclusion body myositis

Mutations in MYH7 cause autosomal dominant Laing distal myopathy. We present a family with a previously reported deletion (c.5186_5188delAGA, p.K1729del). Muscle pathology in one family member was characterized by an inflammatory myopathy with rimmed vacuoles, increased MHC Class I expression, and perivascular and endomysial muscle inflammation comprising CD3⁺, CD4⁺, CD8⁺, and CD68⁺ inflammatory cells. Interestingly, this biopsy specimen contained TDP-43, p62, and SMI-31-positive protein aggregates typical of inclusion body myositis. These findings should alert physicians to the possibility that patients with MYH7 mutations may have muscle biopsies showing pathologic findings similar to inclusion body myositis.

The co-existence of myasthenia gravis in patients with myositis: a case series

OBJECTIVE

Myositis and myasthenia gravis (MG) are both autoimmune disorders presenting with muscle weakness. Rarely, they occur simultaneously in the same patient. Since the management of myasthenia gravis differs from that of myositis, it is important to recognize when patients have both diseases. We reviewed the cases of 6 patients with both myositis and MG to identify clinical features that suggest the possibility of co-existing MG in myositis patients.

METHODS

We identified 6 patients with dermatomyositis or polymyositis and MG. We reviewed their medical records to assess their clinical presentations, laboratory findings, and electrophysiological features.

RESULTS

All 6 patients had definite dermatomyositis or polymyositis by the criteria of Bohan and Peter as well as electrophysiologic and/or serologic confirmation of MG. Among overlap patients, 5/6 (83%) had bulbar weakness, 2/6 (33%) had ptosis, and 1/6 (17%) had diplopia. Fatigable weakness was noted by 5/6 (83%) patients. Treatment with pyridostigmine improved symptoms in 5/6 (83%) patients. High-dose steroids were associated with worsening weakness in 2/6 (33%) patients.

CONCLUSIONS

Prominent bulbar symptoms, ptosis, diplopia, and fatigable weakness should suggest the possibility of MG in patients with myositis. A suspicion of MG may be confirmed through appropriate electrophysiologic and laboratory testing. In those with myositis-MG overlap, high-dose steroids may exacerbate symptoms and pyridostigmine may play an important therapeutic role.

Validation of a score tool for measurement of histological severity in juvenile dermatomyositis and association with clinical severity of disease

Objectives

To study muscle biopsy tissue from patients with juvenile dermatomyositis (JDM) in order to test the reliability of a score tool designed to quantify the severity of histological abnormalities when applied to biceps humeri in addition to quadriceps femoris. Additionally, to evaluate whether elements of the tool correlate with clinical measures of disease severity.

Methods

55 patients with JDM with muscle biopsy tissue and clinical data available were included. Biopsy samples (33 quadriceps, 22 biceps) were prepared and stained using standardised protocols. A Latin square design was used by the International Juvenile Dermatomyositis Biopsy Consensus Group to score cases using our previously published score tool. Reliability was assessed by intraclass correlation coefficient (ICC) and scorer agreement (α) by assessing variation in scorers’ ratings. Scores from the most reliable tool items correlated with clinical measures of disease activity at the time of biopsy.

Results

Inter- and intraobserver agreement was good or high for many tool items, including overall assessment of severity using a Visual Analogue Scale. The tool functioned equally well on biceps and quadriceps samples. A modified tool using the most reliable score items showed good correlation with measures of disease activity.

Conclusions

The JDM biopsy score tool has high inter- and intraobserver agreement and can be used on both biceps and quadriceps muscle tissue. Importantly, the modified tool correlates well with clinical measures of disease activity. We propose that standardised assessment of muscle biopsy tissue should be considered in diagnostic investigation and clinical trials in JDM.

Hemiparetic Primary Lateral Sclerosis: Revisiting Mills Syndrome

A slowly progressive hemiparesis beginning in a single limb with evolution to the ipsilateral limb was originally described in 8 patients in 1906 by Mills. We present 5 cases of progressive hemiparetic corticospinal tract degeneration, identified by the clinical presentation and the exclusion of other etiologies using serological, imaging, and electrodiagnostic studies.

Expanding the spectrum of monoclonal light chain deposition disease in muscle

INTRODUCTION

The diagnosis of amyloid myopathy is delayed when monoclonal gammopathies are not detected on initial testing and muscle biopsies are nondiagnostic, and the EMG and symptoms can mimic an inflammatory myopathy.

METHODS

Case report of a patient presenting with severe progressive muscle weakness of unclear etiology despite an extensive workup including two nondiagnostic muscle biopsies.

RESULTS

Directed by MRI, a third biopsy revealed amyloid angiopathy and noncongophilic kappa light chain deposition in scattered subsarcolemmal rings and perimysial regions. A serum free light chain (FLC) assay revealed a kappa monoclonal gammopathy, which was not detected by multiple immunofixations.

CONCLUSIONS

The spectrum of immunoglobulin deposition in muscle is similar to other organs. It comprises a continuum that includes parenchymal amyloid deposition, amyloid angiopathy, and noncongophilic Light Chain Deposition Disease (LCDD). We recommend including the FLC assay in the routine investigation for monoclonal gammopathies. This case also highlights the value of MRI-guided muscle biopsy.

Loss of sarcolemmal nNOS is common in acquired and inherited neuromuscular disorders

OBJECTIVE

Neuronal nitric oxide synthase (nNOS), normally expressed at the sarcolemmal membrane, is known to be mislocalized to the sarcoplasm in several forms of muscular dystrophy. Our objectives were to characterize further the range of patients manifesting aberrant nNOS sarcolemmal immunolocalization and to study nNOS localization in animal models of nondystrophic myopathy.

METHODS

We carried out a retrospective cross-sectional study. We performed immunofluorescent staining for nNOS on biopsy specimens from 161 patients with acquired and nondystrophin inherited neuromuscular conditions. The localization of sarcolemmal nNOS correlated with mobility and functional status. Muscle specimens from mouse models of steroid-induced and starvation-related atrophy were studied for qualitative and quantitative nNOS expression.

RESULTS

Sarcolemmal nNOS staining was abnormal in 42% of patients with inherited myopathic conditions, 25% with acquired myopathic conditions, 57% with neurogenic conditions, and 93% with hypotonia. Interestingly, we found significant associations between mobility status or muscle function and sarcolemmal nNOS expression. Furthermore, mouse models of catabolic stress also demonstrated mislocalization of sarcolemmal nNOS.

CONCLUSION

Our analyses indicate that nNOS mislocalization is observed in a broad range of nondystrophic neuromuscular conditions associated with impaired mobility status and catabolic stress. Our findings suggest that the assessment of sarcolemmal localization of nNOS represents an important tool for the evaluation of muscle biopsies of patients with a variety of inherited and acquired forms of neuromuscular disorders.

Recombinant expression of the AChR-alpha1 subunit for the detection of conformation-dependent epitopes in Myasthenia Gravis

Detection of autoantibodies associated with neurological disease typically involves immunoprecipitation of radioactively labeled native proteins. We explored whether single receptor subunits, fused to Renilla luciferase (Ruc), could detect patient autoantibodies in Luciferase Immunoprecipitation Systems. Myasthenia Gravis patient sera were tested for conformational autoantibodies to only the α1-subunit of the nicotinic acetylcholine receptor (AChR). Using a panel of 10 AChR-α1 fragments, AChR-α1-Δ5-Ruc demonstrated the highest immunoreactivity with a conformational-specific antibody and the highest sensitivity in a pilot cohort. Testing a larger cohort with AChR-α1-Δ5-Ruc demonstrated 21% sensitivity and 97% specificity. A point mutation within Ruc increased the diagnostic performance of AChR-α1-Δ5 (32% sensitivity, 97% specificity). The (125)I-α-bungarotoxin multi-subunit AChR assay demonstrated 63% sensitivity and 97% specificity. These findings highlight the difficulty in detecting Myasthenia Gravis conformational epitopes across assay formats and lay the foundation for detecting autoantibodies to defined recombinant chains of the AChR and potentially other neurotransmitter receptors.

A novel autoantibody recognizing 200-kd and 100-kd proteins is associated with an immune-mediated necrotizing myopathy

OBJECTIVE

Myofiber necrosis without prominent inflammation is a nonspecific finding in patients with dystrophies and toxic or immune-mediated myopathies. However, the etiology of a necrotizing myopathy is often obscure, and the question of which patients would benefit from immunosuppression remains unanswered. The aim of this study was to identify novel autoantibodies in patients with necrotizing myopathy.

METHODS

Muscle biopsy specimens and serum samples were available for 225 patients with myopathy. Antibody specificities were determined by performing immunoprecipitations from (35)S-methionine-labeled HeLa cell lysates. Selected biopsy specimens were stained for membrane attack complex, class I major histocompatibility complex (MHC), and endothelial cell marker CD31.

RESULTS

Muscle biopsy specimens from 38 of 225 patients showed predominantly myofiber necrosis. Twelve of these patients had a known autoantibody association with or other etiology for their myopathy. Sixteen of the remaining 26 sera immunoprecipitated 200-kd and 100-kd proteins; this specificity was observed in only 1 of 187 patients without necrotizing myopathy. Patients with the anti-200/100 autoantibody specificity had proximal weakness (100%), high creatine kinase levels (mean maximum 10,333 IU/liter), and an irritable myopathy on electromyography (88%). Sixty-three percent of these patients had been exposed to statins prior to the onset of weakness. All patients responded to immunosuppressive therapy, and many experienced a relapse of weakness when the medication was tapered. Immunohistochemical studies showed membrane attack complex on small blood vessels in 6 of 8 patients and on the surface of non-necrotic myofibers in 4 of 8 patients. Five of 8 patients had abnormal capillary morphology, and 4 of 8 patients expressed class I MHC on the surface of non-necrotic myofibers.

CONCLUSION

An anti-200/100-kd specificity defines a subgroup of patients with necrotizing myopathy who previously were considered to be autoantibody negative. We propose that these patients have an immune-mediated myopathy that is frequently associated with prior statin use and should be treated with immunosuppressive therapy.

Expression of the dermatomyositis autoantigen Mi-2 in regenerating muscle

OBJECTIVE

Autoantibodies against the chromatin remodeler Mi-2 are found in a distinct subset of patients with dermatomyositis (DM). Previous quantitative immunoblotting experiments demonstrated that Mi-2 protein levels are up-regulated in DM muscle. This study was undertaken to define the population of cells expressing high levels of Mi-2 in DM muscle and to explore the regulation and functional role of Mi-2 during muscle regeneration.

METHODS

The expression of Mi-2 was analyzed by immunofluorescence microscopy in human muscle biopsy specimens. In an experimental mouse model, cardiotoxin was used to induce muscle injury and repair, and expression of Mi-2 during muscle regeneration was studied in this model by immunofluorescence and immunoblotting analyses. In addition, a cell culture system of muscle differentiation was utilized to artificially modulate Mi-2 levels during proliferation and differentiation of myoblasts.

RESULTS

In human DM muscle tissue, increased Mi-2 expression was found preferentially in the myofibers within fascicles affected by perifascicular atrophy, particularly in the centralized nuclei of small perifascicular muscle fibers expressing markers of regeneration. In injured mouse muscle tissue, Mi-2 levels were dramatically and persistently up-regulated during muscle regeneration in vivo. Premature silencing of Mi-2 with RNA interference in vitro resulted in accelerated myoblast differentiation.

CONCLUSION

Expression of Mi-2 is markedly up-regulated during muscle regeneration in a mouse model of muscle injury and repair. It is also up-regulated in human DM myofibers expressing markers of regeneration. Results of the in vitro studies indicate that this protein may play a role in modulating the kinetics of myoblast differentiation. Our findings thus suggest that high levels of Mi-2 expression in muscle biopsy tissue from patients with DM reflect the presence of incompletely differentiated muscle cells.

International consensus on a proposed score system for muscle biopsy evaluation in patients with juvenile dermatomyositis: A tool for potential use in clinical trials

OBJECTIVE

To devise and test a system with which to evaluate abnormalities on muscle biopsy samples obtained from children diagnosed with juvenile dermatomyositis (DM).

METHODS

We established an International Consensus Group on Juvenile DM Biopsy and carried out 2 phases of consensus process and scoring workshops. Biopsy sections (n = 33) were stained by standard methods. The scoring tool was based on 4 domains of change: inflammatory, vascular, muscle fiber, and connective tissue. Using a Latin square design, biopsy samples were scored by 11 experts for items in each domain, and for a global abnormality measure using a 10-cm visual analog score (VAS 0-10). The tool's reliability was assessed using an intraclass correlation coefficient (ICC) and scorer agreement (alpha) by determining variation in scorers' ratings.

RESULTS

There was good agreement in many items of the tool, and several items refined between the meetings improved in reliability and/or agreement. The inflammatory and muscle fiber domains had the highest reliability and agreement. The overall VAS score for abnormality had high agreement and reliability, reaching an ICC of 0.863 at the second consensus meeting.

CONCLUSION

We propose a provisional scoring system to measure abnormalities on muscle biopsy samples obtained from children with juvenile DM. This system needs to be validated, and then could be used in prospective studies to test which features of muscle pathology are prognostic of disease course or outcome. We suggest that the process we used could be a template for developing similar systems in other forms of myositis.

Abnormal expression of mu-crystallin in facioscapulohumeral muscular dystrophy

To identify proteins expressed abnormally in facioscapulohumeral muscular dystrophy (FSHD), we extracted soluble proteins from deltoid muscle biopsies from unaffected control and FSHD patients and analyzed them using two-dimensional electrophoresis, mass spectrometry and immunoblotting. Muscles from patients with FSHD showed large increases over controls in a single soluble, 34 kDa protein (pI=5.08) identified by mass spectrometry and immunoblotting as mu-crystallin (CRYM). Soluble fractions of biopsies of several other myopathies and muscular dystrophies showed no appreciable increases in mu-crystallin. Mu-crystallin has thyroid hormone and NADPH binding activity and so may influence differentiation and oxidative stress responses, reported to be altered in FSHD. It is also linked to retinal and inner ear defects, common in FSHD, suggesting that its up-regulation may play a specific and important role in pathogenesis of FSHD.

Sarcolemmal reorganization in facioscapulohumeral muscular dystrophy

OBJECTIVE

We examined the sarcolemma of skeletal muscle from patients with facioscapulohumeral muscular dystrophy (FSHD1A) to learn if, as in other murine and human muscular dystrophies, its organization and relationship to nearby contractile structures are altered.

METHODS

Unfixed biopsies of control and FSHD deltoid and biceps muscles, snap-frozen at resting length, were cryosectioned, indirectly immunolabeled with fluorescent antibodies to sarcolemmal and myofibrillar markers, and examined with confocal microscopy to localize the immunolabeled proteins. Glutaraldehyde-fixed samples were stained with heavy metals, embedded, thin-sectioned, and examined with electron microscopy to determine the relationship between the sarcolemma and the underlying myofibrils.

RESULTS

Confocal microscopy showed that some of the structures at the sarcolemma in FSHD samples were misaligned with respect to the underlying contractile apparatus. Electron microscopy showed a significant increase in the distance between the sarcolemma and the nearest myofibrils, from less than 100 nm in controls to values as high as 550 nm in FSHD.

INTERPRETATION

Our results show that the pathophysiology of FSHD includes novel changes in the organization of the sarcolemma and its association with nearby contractile structures and suggest that, as in other muscular dystrophies, the integrity of the sarcolemma may be compromised in FSHD.

Wernicke's encephalopathy: beyond alcoholism

BACKGROUND

A 17-year-old pregnant woman presented to hospital at 19 weeks' gestation with an 8-week history of hyperemesis gravidarum, 16.8 kg of weight loss, and new-onset weakness, dizziness and blurred vision. Examination of the patient showed confusion, papilledema, ophthalmoparesis, nystagmus, reduced hearing and truncal ataxia.

INVESTIGATIONS

Physical examination, abdominal ultrasound, fetal ultrasound, brain MRI, magnetic resonance angiography, magnetic resonance venography and cerebrospinal-fluid analysis.

DIAGNOSIS

Wernicke's encephalopathy, hyperemesis gravidarum and fetal loss.

MANAGEMENT

Intravenous thiamine repletion and elimination of deficiency risk factors.

NAALADase inhibition protects motor neurons against chronic glutamate toxicity

Glutamate toxicity is implicated in the pathogenesis of amyotrophic lateral sclerosis. The neuropeptide N-acetyl-aspartyl glutamate (NAAG) appears to function both as a storage form for glutamate and as a neuromodulator at glutamatergic synapses. N-acetylated-alpha-linked acidic dipeptidase (NAALADase; also termed glutamate carboxypeptidase II) yields N-acetyl aspartate (NAA) and glutamate. Prior studies have demonstrated NAALADase upregulation in motor cortex and increased NAAG, NAA and glutamate in cerebrospinal fluid from amyotrophic lateral sclerosis patients. The potent NAALADase inhibitor, 2-(phosphonomethyl)-pentanedioic acid (2-PMPA), was tested in an in vitro model of chronic glutamate-mediated motor neuron degeneration. Neuroprotection was determined (1) biochemically, by measuring choline acetyltransferase activity, (2) immunohistochemically, by counting neurofilament-H-positive motor neurons and (3) morphologically, with phase contrast microscopy. 2-PMPA (10 microM) had significant neuroprotective effects on motor neurons as evidenced by increased choline acetyltransferase activity, decreased motor neuron loss and improved gross morphology. Results suggest that NAALADase inhibitors protect against chronic glutamate-mediated motor neuron degeneration and may prove therapeutic towards amyotrophic lateral sclerosis.

Pigment epithelium-derived factor is elevated in CSF of patients with amyotrophic lateral sclerosis

Pigment epithelium-derived factor (PEDF), a recently defined retinal trophic factor and anti-angiogenic factor for the eye, is also present in the CNS and is a motor neuron protectant. We asked whether PEDF levels in CSF are altered in patients with amyotrophic lateral sclerosis (ALS). Pigment epithelium-derived factor protein was detected by quantitative western blot analysis with a PEDF-specific antiserum. Levels of PEDF in CSF, expressed as a ratio to total CSF protein, were significantly elevated 3.4-fold in 15 patients with ALS compared with neurologic disease controls (p < 0.0003). This increase does not seem likely to reflect up-regulation of PEDF synthesis in muscle in response to denervation, as CSF PEDF was not elevated in severe denervating diseases other than ALS. Nor does the increase represent some non-specific release in neurodegeneration, as CSF PEDF was not elevated in other neurodegenerative diseases. While the mechanism of this presumably reactive increase is not known, the distinctive, surprisingly elevated level of PEDF in the CSF may be an autoprotective reaction in ALS.

Additivity and potentiation of IGF-I and GDNF in the complete rescue of postnatal motor neurons

BACKGROUND

Both growth and survival of motor neurons may depend on multiple neurotrophic factors. Individually, insulin-like growth factor I (IGF-I) and glial cell line-derived neurotrophic factor (GDNF) are potent neurotrophic/survival factors for postnatal motor neurons.

METHODS

We used an organotypic spinal cord model of glutamatergic degeneration in ALS to investigate whether IGF-I and GDNF interact to enhance motor neuron survival, their trophic effect on choline acetyltransferase (ChAT) activity, and their effect on neurite outgrowth.

RESULTS

We show that the combination of IGF-I and GDNF at active doses (1) is additively neuroprotective, (2) completely rescues rat motor neurons from chronic glutamate-mediated toxicity, and (3) additively upregulates motor neuron ChAT activity. Further, IGF-I, which by itself does not promote neurite outgrowth in this model, potentiates the neurite promoting action of GDNF.

CONCLUSION

The results predict that IGF-I combined with GDNF may provide a better therapy for the treatment of motor neuron disorders such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy.

Preclinical testing of neuroprotective neurotrophic factors in a model of chronic motor neuron degeneration

Many neurotrophic factors have been shown to enhance survival of embryonic motor neurons or affect their response to injury. Few studies have investigated the potential effects of neurotrophic factors on more mature motor neurons that might be relevant for neurodegenerative diseases. Using organotypic spinal cord cultures from postnatal rats, we have demonstrated that insulin-like growth factor-I (IGF-I) and glial-derived neurotrophic factor (GDNF) significantly increase choline acetyltransferase (ChAT) activity, but brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4/5), and neurotrophin-3 (NT-3) do not. Surprisingly, ciliary neurotrophic factor (CNTF) actually reduces ChAT activity compared to age-matched control cultures. Neurotrophic factors have also been shown to alter the sensitivity of some neurons to glutamate neurotoxicity, a postulated mechanism of injury in the neurodegenerative disease, amyotrophic lateral sclerosis (ALS). Incubation of organotypic spinal cord cultures in the presence of the glutamate transport inhibitor threo-hydroxyaspartate (THA) reproducibly causes death of motor neurons which is glutamate-mediated. In this model of motor neuron degeneration, IGF-I, GDNF, and NT-4/5 are potently neuroprotective, but BDNF, CNTF, and NT-3 are not. The organotypic glutamate toxicity model appears to be the best preclinical predictor to date of success in human clinical trials in ALS.

Pigment epithelium-derived factor (PEDF) protects motor neurons from chronic glutamate-mediated neurodegeneration

Although pigment epithelium-derived factor (PEDF) is a neurotrophic factor that may aid the development, differentiation, and survival of adjacent neural retinae, the wider distribution of PEDF mRNA in the central nervous system suggested to us that this factor could have pleiotropic neurotrophic and neuroprotective effects on nonretinal neurons. We examined the distribution of PEDF mRNA and its transcript in the spinal cord. By immunohistochemistry and western blot analysis using an antihuman PEDF antiserum of known specificity, we found that PEDF protein is present in spinal cord, cerebrospinal fluid, and skeletal muscle and that its mRNA appears concentrated in motor neurons of the human spinal cord. These observations indicate that PEDF could have potential autocrine and paracrine effects on motor neurons, as well as being target-derived. We analyzed the pharmacologic utility of PEDF in a postnatal organotypic culture model of motor neuron degeneration and proved it is highly neuroprotective. The effect was biologically important, significantly sparing the spinal cord's gross organotypic morphological appearance and preserving motor neuron choline acetyltransferase (ChAT). PEDF alone did not increase ChAT, indicating that the observed effect is neuroprotective, not merely an upregulation of motor neuron ChAT. Further, PEDF preserved motor neuron number, proving a survival effect. We hypothesize that PEDF may play important roles in the survival and maintenance of spinal motor neurons in their neuroprotection against acquired insults in postnatal life. It should be developed further as a therapeutic strategy for motor neuron diseases such as amyotrophic lateral sclerosis (ALS).

Autonomic and peripheral (sensorimotor) neuropathy in chronic liver disease: a clinical and electrophysiologic study

Peripheral neuropathy has been reported in association with chronic liver disease. However, the precise incidence, severity and characteristics of neuropathy, and the relationship of neuropathy to different etiologies of liver disease have not been defined. In this study, 58 patients with advanced liver disease were evaluated in detail for the presence of neuropathy. Peripheral (sensorimotor) neuropathy was found in 71% and autonomic neuropathy was found in 48% of the patients. Although the majority of patients were asymptomatic, neurological examination showed distal sensory loss to pain, or vibration or distal loss of reflexes in 17 patients (29%). Sensory neuropathy was seen more commonly than motor axonal polyneuropathy on nerve conduction studies. Quantitative sensory testing was frequently abnormal (62%) and cooling thresholds were more affected than vibration thresholds. Overall, the pattern of neuropathy in patients with liver disease conformed to the pattern expected in "dying back" or length-dependent neuropathy. The neuropathy was most severe in patients with advanced hepatic decompensation. Comparison of causes of liver disease showed no significant differences in the severity of neuropathy among the different etiologies. In conclusion, axonal sensory-motor polyneuropathy and autonomic neuropathy are commonly seen in patients with end-stage liver disease of different causes.

Neuroprotective utility and neurotrophic action of neurturin in postnatal motor neurons: comparison with GDNF and persephin

Neurturin and persephin are recently discovered homologs of glial cell line-derived neurotrophic factor (GDNF). Here, we report that neurturin, like GDNF, increases the choline acetyltransferase activity of normal postnatal motor neurons, induces neurite outgrowth in spinal cord, and potently protects motor neurons from chronic glutamate-mediated degeneration. Persephin, in contrast, does not appear to have neurotrophic or neurite-promoting effects on mature motor neurons and may instead worsen the glutamate injury of motor neurons. This pattern in the TGF-beta family suggests certain receptor specificities, requiring at least the Ret/GFRalpha-1 receptor complex. The results predict potential benefit of neurturin, but not persephin, in the treatment of motor neuron disorders and spinal cord diseases.

Sensory nerve pathology in multifocal motor neuropathy

The nosological status of multifocal motor neuropathy remains controversial. The clinical and electrodiagnostic hallmarks suggest selective motor fiber involvement. In this study, we asked to what extent sensory nerves might be involved pathologically in multifocal motor neuropathy. Examination of sensory nerve biopsy specimens from 11 patients did reveal pathological findings in all, but they were very mild. An increased number of thinly myelinated, large-caliber fibers was the unifying feature common to each specimen. By electron microscopy, each biopsy specimen had thinly myelinated fibers surrounded by minor onion bulbs. Active demyelination, though scant, was seen in 3 nerves. Myelinated fiber density was normal. Subperineurial edema and inflammation were not present. We conclude that multifocal motor neuropathy is not an exclusively motor abnormality, although it appears to be so clinically and electrophysiologically. The frequent, albeit mild, pathological abnormalities in sensory fibers suggest that the demyelinating pathophysiology also affects sensory fibers, but to a lesser degree than motor fibers. Some investigators maintain that multifocal motor neuropathy is within the spectrum of chronic inflammatory demyelinating polyneuropathy. The very mild degree of sensory fiber involvement, the absence of inflammation or edema, and the distinctive clinical features support the concept of multifocal motor neuropathy as distinct from chronic inflammatory demyelinating polyneuropathy.

Inter- and intraexaminer reliability of nerve conduction measurements in patients with diabetic neuropathy

We determined the inter- and intraexaminer reliability of nerve conduction measurements in six patients with diabetic peripheral neuropathy. Each patient was examined by six electromyographers on two separate occasions at least 1 week apart. We obtained attributes of nerve conduction at each examination and analyzed the data by analysis of variance. Intraexaminer reliability was high for 11 of 12 measurements, and interexaminer reliability was high for eight of twelve. Three of the four measurements that varied between examiners were either sensory or motor amplitudes, attributes frequently used to measure disease progression or to assess the result of therapeutic intervention. Our results suggest that longitudinal nerve conduction measurements used to assess worsening or improvement over time should optimally be performed by a single examiner to minimize the degree of variability associated with different examiners.

Multifocal motor neuropathy: electrodiagnostic features

Diagnosis of multifocal motor neuropathy (MMN), a syndrome characterized by progressive asymmetric weakness with intact sensation, is important because the disorder often responds to treatment. Multifocal partial motor conduction block (PMCB) has been emphasized as a cardinal feature in the diagnosis of this syndrome, but detailed nerve conduction studies are not available. Nine patients, ages 28-58, had chronic, progressive, asymmetric, predominantly distal limb weakness for 5-18 years. Sensation was normal and reflexes were reduced asymmetrically. Although all 9 demonstrated PMCB localized to short nerve segments, additional features of multifocal motor demyelination were present, including temporal dispersion (5 patients), segmentally reduced motor nerve conduction velocity (7 patients), prolonged distal motor latency (4 patients), and prolonged F-wave latency (9 patients). The strength of all patients improved after treatment with human immune globulin. A reduction in the degree of PMCB or an increase in the distal motor amplitude or both accompanied the clinical improvement. These studies suggest that patients with MMN demonstrate widespread evidence of motor demyelination in addition to the well-described PMCB, and that reduction of PMCB accounts for the increase in strength following therapy.

Multifocal motor neuropathy: response to human immune globulin

Multifocal motor neuropathy (MMN) is a progressive disorder producing asymmetrical weakness and muscle wasting. Case reports suggest that patients with MMN improve after cyclophosphamide therapy, but not after prednisone or plasmapheresis. Because MMN is likely to be immune mediated, we investigated the therapeutic response to human immune globulin (HIG) in an open, uncontrolled trial. Nine patients, ages 28 to 58 years, had chronic, progressive, asymmetrical, predominantly distal, limb weakness for 5 to 18 years. Sensation was normal, and reflexes were reduced asymmetrically. All had physiological evidence of multifocal motor demyelination with partial motor conduction block, and 7 had elevated serum titers of anti-GM1 IgM antibody. All patients were treated with HIG, 1.6 to 2.4 gm/kg, given intravenously over 3 to 5 days. Strength improved in all patients 3 to 10 days after treatment, with improvement peaking at 2 weeks and lasting for an average of 2 months. The range of functional improvement varied from dramatic to mild. The degree of partial motor conduction block was reduced, at least partially, in 7 of 8 patients. The serum anti-GM1 antibody titers did not change. Repeated courses of HIG resulted in similar improvements. We conclude that HIG may be an effective therapy for patients with MMN.