Inflammatory disorders of muscle: progress in polymyositis, dermatomyositis and inclusion body myositis

Autoimmune Dysphagia Related to Rheumatologic Disorders: A Focused Review on Diagnosis and Treatment

Autoimmune dysphagia is defined as dysphagia caused by autoimmune processes affecting various components of the swallowing process such as muscle, neuromuscular junction, nerves, roots, brainstem, or cortex. These autoimmune causes can be classified into gastroenterological, dermatological, rheumatologic, and neurologic. Rheumatological disorders, such as scleroderma, Sjogren's syndrome, systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis, Behcet's disease, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, or granulomatosis with polyangiitis, have been associated with dysphagia. Autoimmune dysphagia in the context of rheumatological disorders is particularly significant because it can occur as a sole manifestation or as part of a symptom complex associated with the underlying disorder and often responds to immunosuppressive therapies. However, diagnosing autoimmune dysphagia can be challenging as it requires the exclusion of structural and primary motility disorders through procedures such as endoscopy and manometry. Early diagnosis is important to improve the quality of life and prevent significant mortality and morbidity. Management focuses on treating the underlying disease activity, and a multidisciplinary approach involving various medical specialties may be necessary to achieve success. This article aims to review the autoimmune rheumatological conditions that can lead to dysphagia and discuss the associated pathophysiological mechanisms. We also outline the clinical clues and laboratory testing methods that facilitate early diagnosis, with the goal of improving patient outcomes through timely intervention and appropriate management.

The role of PD-1 signaling in health and immune-related diseases

Programmed cell death 1 receptor (PD-1) and its ligands constitute an inhibitory pathway to mediate the mechanism of immune tolerance and provide immune homeostasis. Significantly, the binding partners of PD-1 and its associated ligands are diverse, which facilitates immunosuppression in cooperation with other immune checkpoint proteins. Accumulating evidence has demonstrated the important immunosuppressive role of the PD-1 axis in the tumor microenvironment and in autoimmune diseases. In addition, PD-1 blockades have been approved to treat various cancers, including solid tumors and hematological malignancies. Here, we provide a comprehensive review of the PD-1 pathway, focusing on the structure and expression of PD-1, programmed cell death 1 ligand 1 (PD-L1), and programmed cell death 1 ligand 2 (PD-L2); the diverse biological functions of PD-1 signaling in health and immune-related diseases (including tumor immunity, autoimmunity, infectious immunity, transplantation immunity, allergy and immune privilege); and immune-related adverse events related to PD-1 and PD-L1 inhibitors.

Immune-mediated lung diseases: A narrative review

The role of immunity in the pathogenesis of various pulmonary diseases, particularly interstitial lung diseases (ILDs), is being increasingly appreciated as mechanistic discoveries advance our knowledge in the field. Immune-mediated lung diseases demonstrate clinical and immunological heterogeneity and can be etiologically categorized into connective tissue disease (CTD)-associated, exposure-related, idiopathic, and other miscellaneous lung diseases including sarcoidosis, and post-lung transplant ILD. The immunopathogenesis of many of these diseases remains poorly defined and possibly involves either immune dysregulation, abnormal healing, chronic inflammation, or a combination of these, often in a background of genetic susceptibility. The heterogeneity and complex immunopathogenesis of ILDs complicate management, and thus a collaborative treatment team should work toward an individualized approach to address the unique needs of each patient. Current management of immune-mediated lung diseases is challenging; the choice of therapy is etiology-driven and includes corticosteroids, immunomodulatory drugs such as methotrexate, cyclophosphamide and mycophenolate mofetil, rituximab, or other measures such as discontinuation or avoidance of the inciting agent in exposure-related ILDs. Antifibrotic therapy is approved for some of the ILDs (e.g., idiopathic pulmonary fibrosis) and is being investigated for many others and has shown promising preliminary results. A dire need for advances in the management of immune-mediated lung disease persists in the absence of standardized management guidelines.

Autoimmune inflammatory myopathies

The autoimmune inflammatory myopathies constitute a heterogeneous group of acquired myopathies that have in common the presence of endomysial inflammation and moderate to severe muscle weakness. Based on currently evolved distinct clinical, histologic, immunopathologic, and autoantibody features, these disorders can be best classified as dermatomyositis, necrotizing autoimmune myositis, antisynthetase syndrome-overlap myositis, and inclusion body myositis. Although polymyositis is no longer considered a distinct subset but rather an extinct entity, it is herein described because its clinicopathologic information has provided over many years fundamental information on T-cell-mediated myocytotoxicity, especially in reference to inclusion body myositis. Each inflammatory myopathy subset has distinct immunopathogenesis, prognosis, and response to immunotherapies, necessitating the need to correctly diagnose each subtype from the outset and avoid disease mimics. The paper describes the main clinical characteristics that aid in the diagnosis of each myositis subtype, highlights the distinct features on muscle morphology and immunopathology, elaborates on the potential role of autoantibodies in pathogenesis or diagnosis , and clarifies common uncertainties in reference to putative triggering factors such as statins and viruses including the 2019-coronavirus-2 pandemic. It extensively describes the main autoimmune markers related to autoinvasive myocytotoxic T-cells, activated B-cells, complement, cytokines, and the possible role of innate immunity. The concomitant myodegenerative features seen in inclusion body myositis along with their interrelationship between inflammation and degeneration are specifically emphasized. Finally, practical guidelines on the best therapeutic approaches are summarized based on up-to-date knowledge and controlled studies, highlighting the prospects of future immunotherapies and ongoing controversies.

Treatment of gastric cancer with dermatomyositis as the initial symptom: Two case reports and review of literature

BACKGROUND

Dermatomyositis (DM) is a rare autoimmune disease involving the connective tissue. The association between DM and gastric cancer remains unclear. Patients with DM have an increased risk of cancer and higher mortality. It requires immunosuppressive therapy, heightened surveillance, and immunologic response to internal malignancy.

CASE SUMMARY

Two cases of gastric cancer with DM as the first symptom in Zhongshan Hospital, Fudan University (Shanghai, China) were reported. Two patients had a typical skin rash. The rash in the first patient involved mainly bilateral upper limbs and neck, while the second patient manifested rash associated mainly with the face, neck, and back. Both manifested muscle weakness in the extremities and elevated serum creatine kinase. Radical resection of the tumor dramatically improved DM-related symptoms in the two patients. The literature review showed that gastric cancer is more commonly associated with DM in middle-aged and older male populations.

CONCLUSION

The findings suggest the need for comprehensive screening for malignant tumors in patients with DM refractory to long-term pharmacotherapy or hormone manipulation.

Implication of the NLRP3 Inflammasome in Bovine Age-Related Sarcopenia

Sarcopenia is defined as the age-related loss of skeletal muscle mass, quality, and strength. The pathophysiological mechanisms underlying sarcopenia are still not completely understood. The aim of this work was to evaluate, for the first time, the expression of NLRP3 inflammasome in bovine skeletal muscle in order to investigate the hypothesis that inflammasome activation may trigger and sustain a pro-inflammatory environment leading to sarcopenia. Samples of skeletal muscle were collected from 60 cattle belonging to three age-based groups. Morphologic, immunohistochemical and molecular analysis were performed to assess the presence of age-related pathologic changes and chronic inflammation, the expression of NLRP3 inflammasome and to determine the levels of interleukin-1β, interleukin-18 and tumor necrosis factor alpha in muscle tissue. Our results revealed the presence of morphologic sarcopenia hallmark, chronic lymphocytic inflammation and a type II fibers-selective NLRP3 expression associated to a significant decreased number of immunolabeled-fibers in aged animals. Moreover, we found a statistically significant age-related increase of pro-inflammatory cytokines such as interleukin-1β and interleukin-18 suggesting the activation of NLRP3 inflammasome. Taken together, our data suggest that NLRP3 inflammasome components may be normally expressed in skeletal muscle, but its priming and activation during aging may contribute to enhance a pro-inflammatory environment altering normal muscular anabolism and metabolism.

Myofascia-dominant involvement on whole-body MRI as a risk factor for rapidly progressive interstitial lung disease in dermatomyositis

OBJECTIVE

Rapidly progressive interstitial lung disease (RPILD) is a major cause of death in patients with DM. Although clinically amyopathic DM (CADM) represents risk for RPILD, the incidence rate of RPILD in patients with CADM varies widely. Whole-body (WB) MRI can reveal involvement of systemic muscle and myofascia. The objective of this study was to explore the risk factors for RPILD in patients with DM using WB-MRI.

METHODS

This retrospective study comprised 41 patients with DM who underwent WB-MRI before the initiation of treatment in our hospital. Muscular and myofascial signals were scored on 42 muscular groups. The myofascia/muscle ratio was calculated and used to define the relevance of myofascia-dominant involvement. RPILD was defined as worsening of dyspnoea, hypoxaemia and radiographic ILD/fibrosis within 3 months from the onset of respiratory symptoms.

RESULTS

Among the 41 patients, 17 had CADM and 30 had ILD, including 10 patients with RPILD. All patients including those with CADM showed abnormal signal intensity in both muscle and myofascia (median score: 15 and 23, respectively). Muscle signal scores positively correlated with the serum creatine kinase level (r = 0.714; P< 0.001). Patients with RPILD showed a significantly higher myofascia/muscle ratio than those without RPILD (1.929 vs 1.200; P= 0.027). Logistic regression analysis identified higher myofascia/muscle ratio as independent risk factors for developing RPILD.

CONCLUSION

Myofascia-dominant involvement was defined and appreciated in patients with DM using WB-MRI. This may be one of the risk factors for RPILD.

The PD-1/PD-L pathway in rheumatic diseases

BACKGROUND/PURPOSE

Autoimmune diseases are diseases in which the body produces an abnormal immune response to self-antigens and damages its own tissues. Programmed death-1 (PD-1) and its ligands (PD-Ls) have been discovered to be important negative regulators of the immune system, playing crucial roles in autoimmunity.

METHODS

We analyzed the existing scientific literature dealing with this issue. In this review, the PD-1/PD-L pathway in the genetic susceptibility to and pathogenesis of rheumatic diseases is discussed. The PD-1/PD-L pathway might be helpful for diagnosing, evaluating the disease activity of and treating rheumatic diseases.

RESULTS

PD-1/PD-L gene polymorphisms are associated with a genetic predisposition to rheumatic disorders, which can provide reference information for diagnosis and disease activity. The conclusion of the crucial role of the PD-1/PD-L pathway in the pathogenesis of rheumatic diseases is consistent, but the details remain controversial. In some animal models, manipulating the PD-1/PD-L pathway could decrease disease severity. PD-1/PD-Ls may enable us to develop new therapeutics for patients with rheumatic diseases in the future.

CONCLUSION

The PD-1/PD-L pathway plays crucial roles in rheumatic disease. More work is needed to provide a better mechanistic understanding of the PD-1/PD-L pathway and to facilitate the precise therapeutic manipulation of this pathway.

Gastrointestinal Manifestations of Rheumatological Diseases

Rheumatological diseases (RDs) represent a diverse group of diseases that are inherited or related to environmental factors. RDs frequently affect the gastrointestinal (GI) tract, and gastroenterologists are often asked to evaluate patients with symptoms thought to represent an underlying or coexisting RD. GI manifestations of RDs vary based on the organ involved as well as the extent and duration of involvement. Although most manifestations of RD are nonspecific and not life-threatening, the chronicity and severity of symptoms can be debilitating and may lead to serious injury. This narrative review discusses the most common RD encountered by gastroenterologists: systemic lupus erythematosus, systemic sclerosis (scleroderma), dermatomyositis/polymyositis, rheumatoid arthritis, Sjögren syndrome, overlap syndromes, mixed connective tissue disease, Ehlers-Danlos syndromes, and other vasculitides. Each section begins with a brief overview of the condition, followed by a discussion of the etiopathophysiology, physical examination findings, GI manifestations, diagnostic tools (i.e., serologic, imaging, endoscopic, and functional), and treatment options.

Myalgia with the presence of pathologic EMG correlates with perimysial inflammatory infiltrates

Objective

We aimed to define normal numbers of inflammatory cells in muscle biopsies and to identify the predictive value of isolated muscle pain and increased creatine kinase regarding the diagnosis of myositis.

Methods

We analyzed muscle biopsies of 71 patients using immunostains for CD3+, CD4+, CD8+, CD68+, major histocompatibility complex class I, perforin, and myeloid-related protein (MRP) 8. Patients were categorized as follows—group 1: myalgia without further clinical or laboratory abnormalities (n = 24); group 2: asymptomatic elevation of creatine kinase (hyperCKemia, n = 26); group 3: myalgia and pathologic EMG findings (n = 9); and group 4: otherwise healthy controls who had malignant hyperthermia susceptibility testing (n = 12).

Results

In the normal muscle biopsy specimens from group 4, mean endomysial macrophage (CD68+) density was 21.7 ± 5.6/mm2, and perimysial density was 13.0 ± 5.6/mm2. Numbers of T-lymphocytes (CD3+) were 5 ± 3.5 endomysially and 2.2 ± 3.9/mm2 perimysially. This was not different from groups 1 and 2. Only group 3 patients had increased mean numbers of perimysial macrophages (24.1 ± 6.3/mm2; p = 0.0005), CD3+ (7.6 ± 4.9/mm2; p = 0.0056), and CD8+ T-lymphocytes (5.4 ± 3.1/mm2; p = 0.0008) and displayed the activation marker MRP8 in all cases. Although inflammatory cells were increased in the perimysium in group 3, histology did not fulfill the criteria for dermatomyositis, polymyositis, or inclusion body myositis.

Conclusions

Normal muscle contains a considerable number of macrophages and T-lymphocytes. Muscle biopsy is likely to detect inflammatory changes in patients with myalgia or hyperCKemia only if pathologic EMG findings are present.

Endoplasmic Reticulum Stress Induces Myostatin High Molecular Weight Aggregates and Impairs Mature Myostatin Secretion

Sporadic inclusion body myositis (sIBM) is the most prevalent acquired muscle disorder in the elderly with no defined etiology or effective therapy. Endoplasmic reticulum stress and deposition of myostatin, a secreted negative regulator of muscle growth, have been implicated in disease pathology. The myostatin signaling pathway has emerged as a major target for symptomatic treatment of muscle atrophy. Here, we systematically analyzed the maturation and secretion of myostatin precursor MstnPP and its metabolites in a human muscle cell line. We find that increased MsntPP protein levels induce ER stress. MstnPP metabolites were predominantly retained within the endoplasmic reticulum (ER), also evident in sIBM histology. MstnPP cleavage products formed insoluble high molecular weight aggregates, a process that was aggravated by experimental ER stress. Importantly, ER stress also impaired secretion of mature myostatin. Reduced secretion and aggregation of MstnPP metabolites were not simply caused by overexpression, as both events were also observed in wildtype cells under ER stress. It is tempting to speculate that reduced circulating myostatin growth factor could be one explanation for the poor clinical efficacy of drugs targeting the myostatin pathway in sIBM.

Increased risk of venous thromboembolism associated with polymyositis and dermatomyositis: a meta-analysis

Objective

Polymyositis and dermatomyositis (PM/DM) have been implicated in the development of venous thromboembolism (VTE). Previous studies investigating the association between PM/DM and VTE risk had yielded inconsistent findings. The aim of this study was to precisely estimate this association by meta-analysis of all available publications.

Methods

Two investigators independently performed a comprehensive literature search in databases of PubMed, Embase, and the Cochrane Library for eligible studies. The strength for the association was weighed by pooled odds ratios (ORs) with 95% confidence intervals (95% CIs). Stratified analysis and sensitivity analysis were performed for further analysis.

Results

Six studies including 9,045 patients with PM/DM were analyzed. The pooled OR suggested that inflammatory myositis was associated with increased risk of VTE (OR =4.31, 95% CI: 2.55–7.29, P<0.001). Besides, significantly elevated risk of VTE was related with PM and DM, respectively (for PM: OR =6.87, 95% CI: 4.12–11.46, P<0.001; for DM: OR =11.59, 95% CI: 6.54–20.55, P<0.001). In addition, inflammatory myositis could increase the risk of DVT (OR =4.85, 95% CI: 1.38–17.12, P<0.05) and PE (OR =4.74, 95% CI: 2.18–10.30, P<0.05). Sensitivity analysis did not materially alter the pooled results.

Conclusion

Our study shows strong evidence that patients with inflammatory myositis have an increased risk of VTE.

Paraneoplastic antigens as biomarkers for early diagnosis of ovarian cancer

Paraneoplastic syndromes are a group of rare disorders that can be triggered by an abnormal immune response to proteins from tumors of the lung, ovary, lymphatics, or breast. Paraneoplastic clinical syndromes affect < 1% of patients with cancer; however, the frequency of subclinical levels of paraneoplastic autoantibodies in asymptomatic patients with cancer is unknown. Numerous studies have reported that ovarian cancer patients show signs of paraneoplastic neurological syndromes (PNSs) before or after their cancers are diagnosed. PNSs arise from a tumor-elicited immune response against onconeural antigens that are shared by tissues of nervous system, muscle, and tumor cells. Studies on the serum IgGs obtained from ovarian cancer patients have indicated the presence of onconeural antibodies in the absence of any PNS symptoms. The occurrence of PNSs is low in ovarian cancer patients and it can be accompanied by onconeural antibodies. The diagnosis of PNSs is accompanied by a suspicion of a malignant tumor such that neurologists typically refer such patients for a tumor diagnostic workup. There will be tremendous utility if subclinical levels (without paraneoplastic neurological symptoms or myositis) of these autoantibodies to paraneoplastic antigens can be exploited to screen asymptomatic high-risk patients for ovarian cancer, and used as biomarkers in immunoassays for the early detection or recurrence of ovarian cancer. Ovarian cancer overall survival is likely to be improved with early detection. Therefore, a panel of onconeural antigens that can detect paraneoplastic autoantibodies in patient sera should provide diagnostic utility for an earlier therapeutic intervention. Here we review the usefulness of PNS and other paraneoplastic syndromes and their association with paraneoplastic antigens to exploit these autoantibody biomarkers to form diagnostic multi-analyte panels for early detection of ovarian cancer.

Follistatin Gene Therapy for Sporadic Inclusion Body Myositis Improves Functional Outcomes

Sporadic inclusion body myositis, a variant of inflammatory myopathy, has features distinct from polymyositis/dermatomyositis. The disease affects men more than women, most commonly after age 50. Clinical features include weakness of the quadriceps, finger flexors, ankle dorsiflexors, and dysphagia. The distribution of weakness is similar to Becker muscular dystrophy, where we previously reported improvement following intramuscular injection of an isoform of follistatin (FS344) by AAV1. For this clinical trial, rAAV1.CMV.huFS344, 6 × 10¹¹ vg/kg, was delivered to the quadriceps muscles of both legs of six sporadic inclusion body myositis subjects. The primary outcome for this trial was distance traveled for the 6-min walk test. The protocol included an exercise regimen for each participant. Performance, annualized to a median 1-year change, improved +56.0 m/year for treated subjects compared to a decline of -25.8 m/year (p = 0.01) in untreated subjects (n = 8), matched for age, gender, and baseline measures. Four of the six treated subjects showed increases ranging from 58-153 m, whereas two were minimally improved (5-23 m). Treatment effects included decreased fibrosis and improved regeneration. These findings show promise for follistatin gene therapy for mild to moderately affected, ambulatory sporadic inclusion body myositis patients. More advanced disease with discernible muscle loss poses challenges.

Dermatomyositis as a symptom of primary lung cancer: A case report and review of the literature

Dermatomyositis (DM) is a rare autoimmune disease associated with manifestations of proximal muscle weakness and typical cutaneous skin rash. Patients with DM have a higher incidence rate of cancer, compared with the general population, since DM usually presents as a paraneoplastic syndrome. The present study reports a case of a 69-year-old male patient presenting with typical cutaneous rash and aggravating proximal muscle weakness for 3 months. When first admitted to the Department of Dermatology of Shandong Provincial Hospital Affiliated to Shandong University (Jinan, China), the patient was diagnosed with DM. Subsequently, chest computed tomography scan revealed a neoplasm located in the right upper lobe. Video-assisted thoracoscopic surgery right upper lobectomy and lymph node dissection were then performed. The patient experienced a fast recovery from the surgery. The removal of the neoplasm clearly improved the symptoms of DM. Considering that DM is usually associated with the existence of a tumor, cases of DM require a thorough diagnostic investigation in order to exclude an underlying malignancy.

Age-Related Changes in Skeletal Muscle of Cattle

Sarcopenia, the age-related loss of muscle mass and strength, is a multifactorial condition that represents a major healthcare concern for the elderly population. Although its morphologic features have been extensively studied in humans, animal models, and domestic and wild animals, only a few reports about spontaneous sarcopenia exist in other long-lived animals. In this work, muscle samples from 60 healthy Podolica-breed old cows (aged 15-23 years) were examined and compared with muscle samples from 10 young cows (3-6 years old). Frozen sections were studied through standard histologic and histoenzymatic procedures, as well as by immunohistochemistry, immunofluorescence, and Western blot analysis. The most prominent age-related myopathic features seen in the studied material included angular fiber atrophy (90% of cases), mitochondrial alterations (ragged red fibers, 70%; COX-negative fibers, 60%), presence of vacuolated fibers (75%), lymphocytic (predominantly CD8+) inflammation (40%), and type II selective fiber atrophy (40%). Immunohistochemistry revealed increased expression of major histocompatibility complex I in 36 cases (60%) and sarcoplasmic accumulations of β-amyloid precursor protein-positive material in 18 cases (30%). In aged cows, muscle atrophy was associated with accumulation of myostatin. Western blot analysis indicated increased amount of both proteins-myostatin and β-amyloid precursor protein-in muscles of aged animals compared with controls. These findings confirm the presence of age-related morphologic changes in cows similar to human sarcopenia and underline the possible role of amyloid deposition and subsequent inflammation in muscle senescence.

Medication of inclusion body myositis: a systematic review

To investigate the existing evidence on the effectiveness of approaches to treating inclusion body myositis and to assess the methodological quality of this evidence. The Cochrane Controlled Trials Register (CENTRAL), Medline, Embase, Cinahl, Physiotherapy Evidence (Pedro), McMaster and Web of Science databases were searched. The references of identified articles and reviews were also checked for relevancy. The methodological quality was assessed according to the Cochrane Collaboration's domain-based evaluation framework. Of the 331 identified records, 10 were considered relevant for a qualitative analysis. The risk of bias was considered being low for six studies and high for four. Eight studies were randomized controlled trials, and two were controlled clinical trials. In the samples, male gender predominated, and the mean age of the participants varied from 51 to 72 years. The duration of intervention varied from 3 to 17 months. One small trial on the effect of oxandrolone reported a significant positive result. The other trials observed no improvement or insignificant improvement among the participants treated with intravenous immunoglobulin, methotrexate, etanercept or interferon. Thus far, there is no evidence indicating that any specific treatment is the effective in treating inclusion body myositis.

A Neuromuscular Approach to Statin-Related Myotoxicity

Approximately 95% of statin-treated patients tolerate this form of cholesterol management without any adverse effects. However, given their efficacy in reducing low density lipoproteins and cardiovascular events large numbers of patients are selected for statin therapy. Therefore muscle complications are, in fact, quite common. Limited understanding of the underlying pathophysiology has hampered physicians' ability to identify patients at risk for developing statin myotoxicity. A growing number of published case reports/series have implicated statins in the exacerbation of both acquired and genetic myopathies. A clinical management algorithm is presented which outlines a variety of co-morbidities which can potentiate the adverse effects of statins on muscle. In addition, a rational approach to the selection of those patients most likely to benefit from skeletal muscle biopsy is discussed. Ongoing work will define the extent to which statin-intolerant patients represent carriers of recessive metabolic myopathies or pre-symptomatic acquired myopathies. The expanding importance of pharmacogenomics will undoubtedly be realized in the field of statin myopathy research within the next few years. Such critical information is needed to establish more definitive management and diagnostic strategies.

Upregulation of immunoproteasome subunits in myositis indicates active inflammation with involvement of antigen presenting cells, CD8 T-cells and IFNΓ

Objective

In idiopathic inflammatory myopathies (IIM) infiltration of immune cells into muscle and upregulation of MHC-I expression implies increased antigen presentation and involvement of the proteasome system. To decipher the role of immunoproteasomes in myositis, we investigated individual cell types and muscle tissues and focused on possible immune triggers.

Methods

Expression of constitutive (PSMB5, -6, -7) and corresponding immunoproteasomal subunits (PSMB8, -9, -10) was analyzed by real-time RT-PCR in muscle biopsies and sorted peripheral blood cells of patients with IIM, non-inflammatory myopathies (NIM) and healthy donors (HD). Protein analysis in muscle biopsies was performed by western blot. Affymetrix HG-U133 platform derived transcriptome data from biopsies of different muscle diseases and from immune cell types as well as monocyte stimulation experiments were used for validation, coregulation and coexpression analyses.

Results

Real-time RT-PCR revealed significantly increased expression of immunoproteasomal subunits (PSMB8/-9/-10) in DC, monocytes and CD8+ T-cells in IIM. In muscle biopsies, the immunosubunits were elevated in IIM compared to NIM and exceeded levels of matched blood samples. Proteins of PSMB8 and -9 were found only in IIM but not NIM muscle biopsies. Reanalysis of 78 myositis and 20 healthy muscle transcriptomes confirmed these results and revealed involvement of the antigen processing and presentation pathway. Comparison with reference profiles of sorted immune cells and healthy muscle confirmed upregulation of PSMB8 and -9 in myositis biopsies beyond infiltration related changes. This upregulation correlated highest with STAT1, IRF1 and IFNγ expression. Elevation of T-cell specific transcripts in active IIM muscles was accompanied by increased expression of DC and monocyte marker genes and thus reflects the cell type specific involvement observed in peripheral blood.

Conclusions

Immunoproteasomes seem to indicate IIM activity and suggest that dominant involvement of antigen processing and presentation may qualify these diseases exemplarily for the evolving therapeutic concepts of immunoproteasome specific inhibition.

Target specificity of an autoreactive pathogenic human γδ-T cell receptor in myositis

In polymyositis and inclusion body myositis, muscle fibers are surrounded and invaded by CD8-positive cytotoxic T cells expressing the αβ-T cell receptor (αβ-TCR) for antigen. In a rare variant of myositis, muscle fibers are similarly attacked by CD8-negative T cells expressing the γδ-TCR (γδ-T cell-mediated myositis). We investigated the antigen specificity of a human γδ-TCR previously identified in an autoimmune tissue lesion of γδ-T cell-mediated myositis. We show that this Vγ1.3Vδ2-TCR, termed M88, recognizes various proteins from different species. Several of these proteins belong to the translational apparatus, including some bacterial and human aminoacyl-tRNA synthetases (AA-RS). Specifically, M88 recognizes histidyl-tRNA synthetase, an antigen known to be also targeted by autoantibodies called anti-Jo-1. The M88 target epitope is strictly conformational, independent of post-translational modification, and exposed on the surface of the respective antigenic protein. Extensive mutagenesis of the translation initiation factor-1 from Escherichia coli (EcIF1), which served as a paradigm antigen with known structure, showed that a short α-helical loop around amino acids 39 to 42 of EcIF1 is a major part of the M88 epitope. Mutagenesis of M88 showed that the complementarity determining regions 3 of both γδ-TCR chains contribute to antigen recognition. M88 is the only known example of a molecularly characterized γδ-TCR expressed by autoaggressive T cells in tissue. The observation that AA-RS are targeted by a γδ-T cell and by autoantibodies reveals an unexpected link between T cell and antibody responses in autoimmune myositis.

Inflammatory myopathies

OPINION STATEMENT

The mainstay of treatment for the idiopathic inflammatory myopathies currently and traditionally has been therapeutics aimed at suppressing or modifying the immune system. Most therapies being used are directed towards polymyositis (PM) and dermatomyositis (DM), as there is yet to be efficacious treatment of any kind for inclusion body myositis (IBM), However, there are few randomized controlled studies supporting the use of such therapies even in PM and DM. Even in the absence of controlled studies, oral corticosteroids (in particular high-dose prednisone) continue to be the first-line medications used to manage these conditions. Second-line therapies include the addition of chronic, steroid-sparing immunosuppressive drugs such as azathioprine, methotrexate, cyclosporine, cyclophosphamide, and mycophenolate mofetil. These drugs are typically added when patients are on corticosteroids for an extended period or when the disease is refractory. Such medications often allow corticosteroid dosages to be reduced, but monitoring is required for their own side effects, such as bone marrow suppression, kidney dysfunction, and respiratory concerns. Small controlled studies also support the role of intravenous immunoglobulin therapy as an alternative therapy, particularly for DM, though the cost of this treatment is sometimes prohibitive. Rituximab, a monoclonal antibody that depletes B cells, has also shown efficacy in uncontrolled studies in DM and holds promise for the treatment of this disease. Other promising immunotherapies currently under study are inhibitors of interferon-α and tumor necrosis factor-α. Unfortunately, though a number of immunomodulatory treatments have been investigated in IBM, none has convincingly demonstrated benefit.

Therapeutic advances and future prospects in immune-mediated inflammatory myopathies

THE INFLAMMATORY MYOPATHIES INCLUDE THREE DISTINCT ENTITIES: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). A T-cell-mediated cytotoxic process in PM and IBM and a complement-mediated microangiopathy in DM are the hallmarks of the underlying autoimmune processes. The most consistent therapeutic problem remains the distinction of PM from the difficult-to-treat mimics such as s-IBM, necrotizing myopathies and inflammatory dystrophies. This review provides a step-by-step approach to the treatment of inflammatory myopathies, highlights the common pitfalls and mistakes in therapy, and identifies the emerging new therapies. In uncontrolled studies, PM and DM respond to prednisone to some degree and for some period of time, while a combination with one immu-nosuppressive drug (azathioprine, cyclosporine, mycophenolate, methotrexate) offers additional benefit or steroid-sparing effect. In contrast, IBM is resistant to most of these therapies, most of the time. Controlled studies have shown that IVIg is effective and safe for the treatment of DM, where is used as a second, and at times first, line therapy. IVIg seems to be also effective in the majority of patients with PM based on uncontrolled series, but it offers transient help to a small number of patients with IBM especially those with dysphagia. Bona fide patients with PM and DM who become resistant to the aforementioned therapies, may respond to rituximab, tacrolimus or rarely to an tumor necrosis factor alpha inhibitor. For IBM patients, experience with alemtuzumab, a T-cell-depleting monoclonal antibody, is encouraging.

Essential muscle pathology for the rheumatologist

This review introduces/refreshes some basic histopathologic methods and findings of skeletal muscle biopsies with emphasis on those diseases commonly encountered in a rheumatologist's practice. The 3 general areas of myopathology discussed are metabolic myopathies, toxic myopathies, and inflammatory myopathies. The authors, neuropathologists, hope to provide in this article what they think are some commonalities and disease-specific methods in their pathologic workup as well as a practical approach to the collaboration that pathologists undertake with their rheumatology colleagues to come to a working diagnosis.

Disseminated idiopathic myofasciitis in ferrets

First described in 2003, disseminated idiopathic myofasciitis (DIM) has emerged as a new disease in young, domestic ferrets. DIM is a severe inflammatory condition that affects primarily muscles and surrounding connective tissues. The disease is characterized by rapid onset of clinical signs, high fever, neutrophilic leukocytosis, and general lack of response to therapeutic intervention. Until recently DIM was considered fatal, but a few surviving ferrets indicate there may be an effective treatment protocol. DIM is suspected to be an immune-mediated disease, but the etiopathogenesis is not known. This article reviews clinical and pathologic findings in DIM patients, covers recommended diagnostic procedures and clinical management of ferrets with DIM, and discusses potential etiologies for this newly recognized disease in ferrets.

FOXP3+ T regulatory cells in idiopathic inflammatory myopathies

FOXP3+ T regulatory cells (Tregs) are considered key players in the maintenance of immune homeostasis. Here we studied the presence and potential role of FOXP3+ Tregs in myositis. CD3 and FOXP3 expression in dermatomyositis, polymyositis and inclusion body myositis was assessed by immunohistochemistry and real-time PCR. FOXP3+ Tregs were found in close proximity to effector cells and their numbers correlated with the degree of inflammation. Despite divergent pathogenetic concepts, we observed no differences in the frequency of FOXP3 immunoreactive cells or FOXP3 mRNA expression between different myositis entities. Functional assays using human myoblasts as targets of CD8+ cells demonstrate that Tregs are capable to inhibit the lytic activity of cytotoxic cells. Our data suggest that FOXP3 Tregs serve to counterbalance muscle destruction by cytotoxic T cells in myositis.

Myofiber stress-response in myositis: parallel investigations on patients and experimental animal models of muscle regeneration and systemic inflammation

Introduction

The endoplasmic reticulum (ER) stress-response, evoked in mice by the overexpression of class I major histocompatibility complex antigen (MHC-I), was proposed as a major mechanism responsible for skeletal muscle damage and dysfunction in autoimmune myositis. The present study was undertaken to characterize in more detail the ER stress-response occurring in myofibers of patients with inflammatory myopathies, focusing on the expression and distribution of Grp94, calreticulin and Grp75, three ER chaperones involved in immunomodulation.

Methods

Muscle biopsies were obtained from seven healthy subjects and 29 myositis patients, who were subdivided into groups based on the morphological evidence of inflammation and/or sarcolemmal immunoreactivity for MHC-I. Biopsies were analyzed by means of immunohistochemistry and western blot using anti-Grp94, anti-calreticulin and anti-Grp75 specific antibodies. Parallel analyses on these ER chaperones were conducted in rabbit and/or murine skeletal muscle after experimental induction of regeneration or systemic inflammation.

Results

Upregulation of Grp94 characterized regenerating myofibers of myositis patients (P = 0.03, compared with values detected in biopsies without signs of muscle regeneration) and developing and regenerating myofibers of mouse muscles. Conversely, levels of calreticulin and Grp75 increased about fourfold and twofold, respectively, in patient biopsies positive for sarcolemmal MHC-I immunoreactivity, compared with healthy subjects and patients negative for both inflammation and MHC-I labeling (P < 0.005). Differently from calreticulin, the Grp75 level increased significantly also in patient biopsies that displayed occasional sarcolemmal MHC-I immunoreactivity (P = 0.002), suggesting the interference of other mechanisms. Experimental systemic inflammation achieved in mice and rabbits by a single injection of bacterial lipopolysaccharide significantly increased Grp75 and calreticulin but not MHC-I expression in muscles.

Conclusions

These results indicate that, in myositis patients, muscle regeneration and inflammation, in addition to MHC-I upregulation, do evoke an ER stress-response characterized by the increased expression of Grp94 and Grp75, respectively. The increase in the muscle Grp75 level in patients showing occasional immunoreactivity for sarcolemmal MHC-I might be considered further as a broader indicator of idiopathic inflammatory myopathy.

Polymyositis, dermatomyositis and malignancy: a further intriguing link

The association between malignancy and autoimmune myositis has been largely described and confirmed by numerous epidemiological studies. The temporal relationship between the two pathologic conditions can vary: malignancy may occur before, at the same time or following the diagnosis of myositis. Beside these observations, the molecular mechanisms underlying this association are still unknown, even though it has been demonstrated a possible antigenic similarity between regenerating myoblasts and some cancer cell populations. To better identify peculiar histopathologic features common to cancer and myositis, we screened muscle biopsies from patients affected with polymyositis, dermatomyositis, myositis in association to cancer, and from patients affected with newly diagnosed cancer, but without myositis. Similarly to the histopatologic features that were observed in the muscle from myositis patients, especially in those with cancer associated myositis, in patients affected with malignancy at the clinical onset of disease we observed early sign of myopathy, characterized by internally nucleated and regenerating myofibers, most of them expressing the neural cell adhesion molecule. The hypothesis that in a particular subset of individuals genetically predisposed to autoimmunity, an initial subclinical tumor-induced myopathy may result in an autoimmune myositis, represents a further intriguing link behind the association of these two conditions.

Differential immunohistological features of inflammatory myopathies and dysferlinopathy

This study was performed in order to characterize the types of the infiltrating cells, and the expression profiles of major histocompatibility complex (MHC) class I and membrane attack complex (MAC) in patients with inflammatory myopathies and dysferlinopathy. Immunohistochemical stains were performed using monoclonal antibodies against several inflammatory cell types, MHC class I, and MAC in muscles from inflammatory myopathies and dysferlinopathy. There was significant difference in the types of infiltrating cells between polymyositis (PM), dermatomyositis (DM), and dysferlinopathy, including significantly high CD4+/CD8+ T cell ratio and B/T cell ratio in DM. In dysferlinopathy, CD4+ T cells were the most abundant and the proportions of infiltrating cell types were similar to those of DM. MHC class I was expressed in muscle fibers of PM and DM regardless of the presence of inflammatory infiltrates. MAC was expressed in necrotic fibers and vessels of PM and DM. One patient with early stage DM had a MAC deposits on endomysial capillaries. In dysferlinopathy, MAC deposit was also observed on the sarcolemma of nonnecrotic fibers. The analysis of inflammatory cells, MHC class I expressions and MAC deposits may help to differentiate dysferlinopathy from idiopathic inflammatory myopathy.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies are a group of systemic autoimmune syndromes characterized by striated muscle inflammation. Here, we discuss the clinical features of this group of conditions and review the recent developments in the understanding of the pathogenesis and immunogenetics of the idiopathic inflammatory myopathies. The role of myositis-specific autoantibodies and their clinical significance and an overview of management are also provided.

How citation distortions create unfounded authority: analysis of a citation network

OBJECTIVE

To understand belief in a specific scientific claim by studying the pattern of citations among papers stating it.

DESIGN

A complete citation network was constructed from all PubMed indexed English literature papers addressing the belief that beta amyloid, a protein accumulated in the brain in Alzheimer's disease, is produced by and injures skeletal muscle of patients with inclusion body myositis. Social network theory and graph theory were used to analyse this network.

MAIN OUTCOME MEASURES

Citation bias, amplification, and invention, and their effects on determining authority.

RESULTS

The network contained 242 papers and 675 citations addressing the belief, with 220,553 citation paths supporting it. Unfounded authority was established by citation bias against papers that refuted or weakened the belief; amplification, the marked expansion of the belief system by papers presenting no data addressing it; and forms of invention such as the conversion of hypothesis into fact through citation alone. Extension of this network into text within grants funded by the National Institutes of Health and obtained through the Freedom of Information Act showed the same phenomena present and sometimes used to justify requests for funding.

CONCLUSION

Citation is both an impartial scholarly method and a powerful form of social communication. Through distortions in its social use that include bias, amplification, and invention, citation can be used to generate information cascades resulting in unfounded authority of claims. Construction and analysis of a claim specific citation network may clarify the nature of a published belief system and expose distorted methods of social citation.

Long-term remission of severe refractory dermatopolymyositis with a weekly-scheme of immunoglobulin followed by rituximab therapy

We report on a 44-year-old woman affected by dermatopolymyositis resistant to conventional therapies who experienced long-term clinical improvement and remission after treatment with intravenous polyvalent immunoglobulin in a weekly schedule followed by rituximab therapy.

Effect of Alemtuzumab (CAMPATH 1-H) in patients with inclusion-body myositis

Sporadic inclusion-body myositis (sIBM) is the most common disabling, adult-onset, inflammatory myopathy histologically characterized by intense inflammation and vacuolar degeneration. In spite of T cell-mediated cytotoxicity and persistent, clonally expanded and antigen-driven endomysial T cells, the disease is resistant to immunotherapies. Alemtuzumab is a humanized monoclonal antibody that causes an immediate depletion or severe reduction of peripheral blood lymphocytes, lasting at least 6 months. We designed a proof-of-principle study to examine if one series of Alemtuzumab infusions in sIBM patients depletes not only peripheral blood lymphocytes but also endomysial T cells and alters the natural course of the disease. Thirteen sIBM patients with established 12-month natural history data received 0.3 mg/kg/day Alemtuzumab for 4 days. The study was powered to capture > or =10% increase strength 6 months after treatment. The primary end-point was disease stabilization compared to natural history, assessed by bi-monthly Quantitative Muscle Strength Testing and Medical Research Council strength measurements. Lymphocytes and T cell subsets were monitored concurrently in the blood and the repeated muscle biopsies. Alterations in the mRNA expression of inflammatory, stressor and degeneration-associated molecules were examined in the repeated biopsies. During a 12-month observation period, the patients' total strength had declined by a mean of 14.9% based on Quantitative Muscle Strength Testing. Six months after therapy, the overall decline was only 1.9% (P < 0.002), corresponding to a 13% differential gain. Among those patients, four improved by a mean of 10% and six reported improved performance of daily activities. The benefit was more evident by the Medical Research Council scales, which demonstrated a decline in the total scores by 13.8% during the observation period but an improvement by 11.4% (P < 0.001) after 6 months, reaching the level of strength recorded 12 months earlier. Depletion of peripheral blood lymphocytes, including the naive and memory CD8+ cells, was noted 2 weeks after treatment and persisted up to 6 months. The effector CD45RA(+)CD62L(-) cells, however, started to increase 2 months after therapy and peaked by the 4th month. Repeated muscle biopsies showed reduction of CD3 lymphocytes by a mean of 50% (P < 0.008), most prominent in the improved patients, and reduced mRNA expression of stressor molecules Fas, Mip-1a and alphaB-crystallin; the mRNA of desmin, a regeneration-associated molecule, increased. This proof-of-principle study provides insights into the pathogenesis of inclusion-body myositis and concludes that in sIBM one series of Alemtuzumab infusions can slow down disease progression up to 6 months, improve the strength of some patients, and reduce endomysial inflammation and stressor molecules. These encouraging results, the first in sIBM, warrant a future study with repeated infusions

Skeletal muscle as a paradigm for regenerative biology and medicine

Tissue development and regeneration share common features, since modules of regulatory pathways and transcription factors that are crucial for prenatal development are redeployed for tissue reconstruction after trauma. Regenerative medicine has therefore gained important insights through the study of developmental and regenerative biology. Moreover, diverse experimental models have been used to investigate the regeneration process in different tissues and organs. Paradoxically, little is known regarding the relative contribution of stem cells with respect to the supporting tissue during tissue regeneration. Particular attention will be given to mouse models using distinct injury paradigms to investigate the regenerative biology of skeletal muscle. An understanding of the response of stem and parenchymal cells is crucial for the development of clinical strategies to combat the normal decline in tissue performance during aging or its reconstitution after trauma and during disease. This review addresses these issues, focusing on muscle regeneration and how different factors, including genes, cells and the environment, impinge on this process.

Idiopathic inflammatory myopathy: treatment options

Idiopathic inflammatory myopathy (IIM) comprises a group of rare disorders in which there is an immune-mediated attack on skeletal muscle, the consequence of which is muscle damage and weakness in the patient. As in other inflammatory diseases, the general approach to therapy is use of immunosuppressive agents. Many options exist for IIM treatment, but therapeutic approaches are based mostly on empirical evidence and small studies, many of which are uncontrolled. Recently, new agents have been designed to target specific components of the immune response, and they offer hope for more effective or safer IIM therapy.