Myogenic Progenitor Cells Exhibit Type I Interferon–Driven Proangiogenic Properties and Molecular Signature During Juvenile Dermatomyositis

Over Activation of IL-6/STAT3 Signaling Pathway in Juvenile Dermatomyositis

INTRODUCTION

Juvenile dermatomyositis (JDM) is characterized by persistent non-purulent inflammation in the muscle and skin. The underlying mechanisms still remain uncertain. This study aims to elucidate the mechanism of interleukin-6 (IL-6) activation of Janus kinase/signal transducer and activator of transcription 3 pathway (JAK/STAT3), contributing to the pathogenesis of JDM.

METHODS

Serum IL-6 levels were compared between 72 newly diagnosed patients with JDM and the same patient cohort in treatment remission. Single-cell RNA sequencing (scRNA-seq) was employed to identify differential signaling pathway expression in muscle biopsy samples from two patients with JDM and healthy controls. Immunohistochemistry was used to examine differences in STAT3 phosphorylation between JDM and control muscle tissues. In vitro, skeletal muscle cell lines were stimulated with IL-6, and the transcription levels of genes related to mitochondrial calcium channels were quantified via reverse transcription-polymerase chain reaction (RT-PCR). Reactive oxygen species (ROS) production was measured in both IL-6 treated and untreated groups. ROS levels were then compared between IL-6 receptor antagonist pre-treated skeletal muscle cells and untreated cells.

RESULTS

IL-6 levels in newly onset patients with JDM were significantly higher compared to the same patient cohort in remission states (p < 0.0001). Serum IL-6 was significantly increased in patients with negative myositis specific antibody (MSA), positive melanoma differentiation associated protein 5 (MDA5) and positive nuclear matrix protein 2 (NXP2), yet not for JDM with positive transcriptional intermediary factor γ (TIF1γ), based on subgroup analysis. ScRNA-seq analysis of muscle biopsies from patients with MDA5-positive JDM and patients with MSA negative JDM revealed abnormal activation of the JAK/STAT3 pathway in skeletal myocytes, macrophages, and vascular endothelial cells. The phosphorylation levels of STAT3 were elevated in active JDM cases. Transcription of the calcium channel modulation gene sarcolipin (SLN) was significantly higher in JDM primary skeletal muscle cells compared to normal cells. In vitro, IL-6 enhanced SLN transcription and induced ROS production, and blocking the IL-6 receptor resulted in decreased ROS generation in skeletal muscle cells.

CONCLUSIONS

IL-6/JAK/STAT3 signaling pathway was abnormally activated in patients with JDM. IL-6 may be involved in the pathogenesis of muscle damage by triggering the development of calcium overload and production of ROS. Blockade of the IL-6/JAK/STAT3 pathway can be a potential treatment option for JDM, especially MDA5-positive patients and those who are negative for MSA.

Understanding the Role of Type I Interferons in Cutaneous Lupus and Dermatomyositis: Toward Better Therapeutics

A 29-year-old female presented to a rheumatology-dermatology clinic with a pruritic rash that began 6 months prior, after a viral illness. She had previously been diagnosed with eczema and treated with antihistamines and topical steroids without improvement. She also noted fatigue, hair loss, and severe scalp pruritus. Physical examination was notable for violaceous periorbital edema, scaly erythematous papules on the metacarpophalangeal joints of bilateral hands, dilated capillaries of the proximal nail folds, scaly plaques on bilateral elbows, and excoriated erythematous plaques on upper chest, back and hips. The patient reported no muscle weakness, and strength testing and creatinine phosphokinase were normal. Magnetic resonance imaging of the thigh showed no evidence of inflammation or edema. Antibody testing was negative. A diagnosis of clinically amyopathic dermatomyositis was made. Computed tomography scans of the chest, abdomen and pelvis, colonoscopy, and mammogram showed no evidence of cancer. The patient was initiated on methotrexate. Her cutaneous manifestations persisted with debilitating intractable pruritus, and thus, she was transitioned to mycophenolate mofetil, again with minimal improvement. Intravenous immunoglobulin was not approved by insurance given the lack of muscle involvement in her disease. This patient's case highlights a common clinical scenario in rheumatology and dermatology and raises several important issues related to the immunologic underpinnings of cutaneous lupus erythematosus (CLE) and dermatomyositis (DM): What is the role of type I interferon (IFN) in triggering skin disease in CLE and DM? What is the role of IFN in the pathogenesis of skin inflammation in CLE and DM? Can we apply what we know about IFN-targeted therapeutics in CLE and DM to develop better treatments for skin disease?

Effect of type I interferon on engineered pediatric skeletal muscle: a promising model for juvenile dermatomyositis

OBJECTIVE

To investigate pathogenic mechanisms underlying JDM, we defined the effect of type I IFN, IFN-α and IFN-β, on pediatric skeletal muscle function and expression of myositis-related proteins using an in vitro engineered human skeletal muscle model (myobundle).

METHODS

Primary myoblasts were isolated from three healthy pediatric donors and used to create myobundles that mimic functioning skeletal muscle in structural architecture and physiologic function. Myobundles were exposed to 0, 5, 10 or 20 ng/ml IFN-α or IFN-β for 7 days and then functionally tested under electrical stimulation and analyzed immunohistochemically for structural and myositis-related proteins. Additionally, IFN-β-exposed myobundles were treated with Janus kinase inhibitors (JAKis) tofacitinib and baricitinib. These myobundles were also analyzed for contractile force and immunohistochemistry.

RESULTS

IFN-β, but not IFN-α, was associated with decreased contractile tetanus force and slowed twitch kinetics. These effects were reversed by tofacitinib and baricitinib. Type I IFN paradoxically reduced myobundle fatigue, which did not reverse after JAKi. Additionally, type I IFN correlated with MHC I upregulation, which normalized after JAKi treatment, but expression of myositis-specific autoantigens Mi-2, melanocyte differentiation-associated protein 5 and the endoplasmic reticulum stress marker GRP78 were variable and donor specific after type I IFN exposure.

CONCLUSION

IFN-α and IFN-β have distinct effects on pediatric skeletal muscle and these effects can partially be reversed by JAKi treatment. This is the first study illustrating effective use of a three-dimensional human skeletal muscle model to investigate JDM pathogenesis and test novel therapeutics.

Contribution of Complement, Microangiopathy and Inflammation in Idiopathic Inflammatory Myopathies

PURPOSE OF REVIEW

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group characterized by muscle weakness and skin symptoms and are categorized into six subtypes: dermatomyositis (DM), polymyositis (PM), anti-synthetase syndrome (ASS), immune-mediated myopathy (IMNM), inclusion body myopathy (IBM), and overlap myositis. Myositis-specific autoantibodies were detected for the diagnosis and classification of IIM. This review highlights the pathogenic contributions of the complement system, microangiopathy, and inflammation in IIM.

RECENT FINDINGS

Deposition of complement around capillaries and/or the sarcolemma was observed in muscle biopsy specimens from patients with DM, ASS, and IMNM, suggesting the pathomechanism of complement-dependent muscle and endothelial cell injury. A recent study using human muscle microvascular endothelial cells showed that Jo-1 antibodies from ASS induce complement-dependent cellular cytotoxicity in vitro. Based on both clinical and pathological observations, antibody- and complement-mediated microangiopathy may contribute to the development of DM and anti-Jo-1 ASS. Juvenile DM is characterized by the loss of capillaries, perivascular inflammation, and small-vessel angiopathies, which may be related to microinfarction and perifascicular atrophy. Several serum biomarkers that reflect the IFN1 signature and microangiopathy are elevated in patients with DM. The pathological observation of myxovirus resistance protein A (MxA), which suggests a type 1 interferon (IFN1) signature in DM, supports the diagnosis and further understanding of the pathomechanism of IIM. A recent report showed that an increase in triggering receptor expressed on myeloid cells (TREM-1) around perimysial blood vessels and muscles in patients with IIM plays a role in triggering inflammation and promoting the migration of inflammatory cells by secreting proinflammatory cytokines, such as tumor necrosis factor α.

SUMMARY

The deposition of complement in muscles and capillaries is a characteristic feature of DM, ASS, and IMNM. Microangiopathy plays a pathogenic role in DM, possibly resulting in perifascicular atrophy. Further understanding of the detailed pathomechanism regarding complement, microangiopathy, and inflammation may lead to novel therapeutic approaches for IIM.

Identification of key biomarkers associated with immune cells infiltration for myocardial injury in dermatomyositis by integrated bioinformatics analysis

BACKGROUND

Dermatomyositis (DM) is an acquired autoimmune disease that can cause damage to various organs, including the heart muscle. However, the mechanisms underlying myocardial injury in DM are not yet fully understood.

METHODS

In this study, we utilized publicly available datasets from the Gene Expression Omnibus (GEO) database to identify hub-genes that are enriched in the immune system process in DM and myocarditis. Weighted gene co-expression network analysis (WGCNA), differentially expressed genes (DEGs) analysis, protein-protein interaction (PPI), and gene ontology (GO) analysis were employed to identify these hub-genes. We then used the CIBERSORT method to analyze immune cell infiltration in skeletal muscle specimens of DM and myocardium specimens of myocarditis respectively. Correlation analysis was performed to investigate the relationship between key genes and infiltrating immune cells. Finally, we predicted regulatory miRNAs of hub-genes through miRNet and validated their expression in online datasets and clinical samples.

RESULTS

Using integrated bioinformatics analysis, we identified 10 and 5 hub-genes that were enriched in the immune system process in the database of DM and myocarditis respectively. The subsequent intersections between hub-genes were IFIT3, OAS3, ISG15, and RSAD2. We found M2 macrophages increased in DM and myocarditis compared to the healthy control, associating with the expression of IFIT3, OAS3, ISG15, and RSAD2 in DM and myocarditis positively. Gene function enrichment analysis (GSEA) showed that IFIT3, OAS3, ISG15, and RSAD2 were mainly enriched in type I interferon (IFN) signaling pathway, cellular response to type I interferon, and response to type I interferon. Finally, we verified that the expression of miR-146a-5p was significantly higher in the DM with myocardial injury than those without myocardial injury (p = 0.0009).

CONCLUSION

Our findings suggest that IFIT3, OAS3, ISG15, and RSAD2 may play crucial roles in the underlying mechanism of myocardial injury in DM. Serum miR-146a-5p could be a potential biomarker for myocardial injury in DM.

Update on Biomarkers of Vasculopathy in Juvenile and Adult Myositis

PURPOSE OF REVIEW

Although rare, idiopathic inflammatory myopathies (IIM) comprise a heterogeneous group of autoimmune conditions in adults and children. Increasingly, vasculopathy is recognised to be key in the underlying pathophysiology and plays a crucial role in some of the more challenging complications including calcinosis, gastrointestinal involvement and interstitial lung disease. The exciting prospect of development of biomarkers of vasculopathy would enable earlier detection and monitoring of these complications and possible prevention of their potentially devastating consequences. The purpose was to review the current literature on biomarkers of vasculopathy in IIM and offer insight as to the biomarkers most likely to have an impact on clinical care.

RECENT FINDINGS

Multiple candidate biomarkers have been studied including circulating endothelial cells (CEC), microparticles (MP), soluble adhesion markers (ICAM-1, ICAM-3, VCAM-1), selectin proteins (E-, L-, P-selectin), coagulation factors, angiogenic factors, cytokines (including (IL-6, IL-10, TNF-α, IL-18) and interferon (IFN)-related biomarkers (including IFNα, IFN-β, IFNγ, galectin-9, interferon signature and interferon-related chemokines (MCP-1, IP-10 and MIG). There is a growing body of evidence of the potential role of biomarkers in detecting and monitoring the vasculopathy in IIM, detecting disease activity and predicting disease flares and overall prognosis. Exciting progress has been made in the search for biomarkers of vasculopathy of IIM; however, none of the studies are validated and further research is required.

Involvement of Type-I Interferon Signaling in Muscle Stem Cell Proliferation During Dermatomyositis

Background and objective:

The idiopathic inflammatory myopathy Dermatomyositis (DM) is an acquired disease that combines muscle, lung and skin impairments. DM patients show a wide range of severity of proximal skeletal muscle weakness, associated with inflammatory infiltrates, vasculitis, and capillary dropout, perifascicular myofiber atrophy. Moreover, DM muscles show signs of muscle regeneration. Since muscle stem cells (MuSCs) are responsible for myofiber repair, we asked wether the proliferative properties of muscle stem cells (MuSCs) are altered in DM muscle. We investigated the role of type-I interferon (IFN-I) in this process since DM is associated with sustained inflammation with high IFN-I levels.

Methods:

MuSCs isolated from normal, adult and juvenile DM muscles were grown in culture and were analyzed in vitro for their proliferating properties, their myogenic capacities and their senescence. Gain and loss of function experiments were performed to assess the role of IFN-I signaling in the prolfierative capacities of MuSCs.

Results:

MuSCs derived from 8 DM adult patients (DM-MuSCs) (5 severe form and 3 mild form, established from histological evaluation), from 3 juvenile DM patients and from normal muscle were used to analyze their myogenesis in vitro. DM-MuSCs exhibited strongly reduced proliferating capacities as compared with healthy MuSCs (-31 to -43% for severe and mild DM, respectively), leading to poor myotube formation (-36 to -71%). DM-MuSCs were enriched in senescent, beta-galactosidase positive cells, explaining partly the proliferation defect. Gain and loss of function experiments were performed to assess the role of IFN-I on the proliferative capacity of MuSCs. High concentrations of IFN-I decreased the proliferation of healthy MuSCs. Similarly, conditioned-medium from DM-MuSCs decreased the proliferation of healthy MuSC (-15 to -22%), suggesting the delivery of an autocrine effector. Then, pharmacological blockade of the IFN signaling (using ruxolitinib or anti-IFN-receptor antibodies) in DM-MuSCs rescued their proliferation up to the control values.

Discussion:

These results show that autocrine IFN-I signaling prevents MuSC expansion, leading to muscle repair deficit. This process may explain the persistent muscle weakness observed in severe DM patients.

Evaluating the use of JAK inhibitors in inflammatory connective tissue diseases in pediatric patients: an update

INTRODUCTION

Connective tissue diseases (CTDs) are a category of conditions that affect tissues that support and provide structure to the body. These diseases include rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, and sclerosing diseases. CTDs can be caused by dysregulation of inflammatory pathways, specifically an upregulation of interferons and JAK/STAT pathway activation.

AREAS COVERED

While CTDs have historically been treated with broadly immunosuppressant medications such as corticosteroids and disease-modifying antirheumatic drugs (DMARDS), newer and more targeted immunomodulating medications called Janus kinase inhibitors (JAKi), have emerged as potential treatments.

EXPERT OPINION

While most studies regarding JAKi for CTDs have focused on adult populations, pediatric patients with CTDs may also benefit from JAKi therapy. Moreover, the JAK/STAT inhibitor tofacitinib has been approved by the FDA for the treatment of active polyarticular course juvenile idiopathic arthritis. In this review, we have summarized what has been published on the use of JAKi for various pediatric CTDs.

Transcriptomes of peripheral blood mononuclear cells from juvenile dermatomyositis patients show elevated inflammation even when clinically inactive

In juvenile dermatomyositis (JDM), the most common pediatric inflammatory myopathy, weakness is accompanied by a characteristic rash that often becomes chronic and is associated with vascular damage. We hoped to understand the molecular underpinnings of JDM, particularly when untreated, which would facilitate the identification of novel mechanisms and clinical targets that might disrupt disease progression. We studied the RNA-Seq data from untreated JDM peripheral blood mononuclear cells (PBMCs; n = 11), PBMCs from a subset of the same patients when clinically inactive (n = 8/11), and separate samples of untreated JDM skin and muscle (n = 4 each). All JDM samples were compared to non-inflammatory control tissues. The untreated JDM PBMCs showed a strong signature for type1 interferon response, along with IL-1, IL-10, and NF-κB. Surprisingly, PBMCs from clinically inactive JDM individuals had persistent immune activation that was enriched for IL-1 signaling. JDM skin and muscle both showed evidence for type 1 interferon activation and genes related to antigen presentation and decreased expression of cellular respiration genes. Additionally, we found that PBMC gene expression correlates with disease activity scores (DAS; skin, muscle, and total domains) and with nailfold capillary end row loop number (an indicator of microvascular damage). This included otoferlin, which was significantly increased in untreated JDM PBMCs and correlated with all 3 DAS domains. Overall, these data demonstrate that PBMC transcriptomes are informative of molecular disruptions in JDM and provide transcriptional evidence of chronic inflammation despite clinical quiescence.

Short-term effectiveness of baricitinib in children with refractory and/or severe juvenile dermatomyositis

OBJECTIVE

To determine the short-term effectiveness safety of baricitinib in children with refractory and/or severe juvenile dermatomyositis (rsJDM) in a real-world setting.

METHODS

This was a single-center retrospective study, including 20 children with rsJDM. They were all treated using baricitinib combined with steroids and other immunosuppressive agents. The childhood myositis assessment scale (CMAS) and PRINTO remission criteria were used to evaluate the disease severity and treatment outcome at 0, 4, 12, and 24 weeks after initiation of baricitinib.

RESULTS

The skin rash improved in 95% of patients (19/20) at week 24, with a significant decrease of skin-DAS at weeks 12 (6.0 vs. 2.0, p < 0.05] and week 24 [6.0 vs. 1.0, p < 0.05) by median statistics. The CMAS score increased significantly at week 12 (41.0 [29.0, 44.0] vs. 46.0 [42.0, 52.0], p < 0.05) and week 24 (41.0 [29.0, 44.0] vs. 50.0 [45.0, 52.0], p < 0.05), as did the manual muscle testing (MMT)-8 score at week 24 (73.0 [610, 76.0] vs. 79.0 [77.0, 80.0], p < 0.05). At 24 weeks, the complete response (CR) and partial response (PR) were achieved in 75% (15/20) and 15% (3/20), respectively. The dose of corticosteroids (CS) decreased by 37% from the baseline (0.53 [0.42, 1.00] mg/kg) to week 12 (0.33 [0.18, 0.40] mg/kg) (p < 0.05), and by 49% at week 24 (p < 0.05). No serious side effects were observed.

CONCLUSION

Baricitinib combined with traditional immunosuppressants treatment was efficacious in rsJDM. Add-on therapy of baricitinib was helpful for tapering CS dose. No serious side effects were observed in this study.

Inflammatory myopathies in childhood

Myositis in childhood can occur under different conditions and with various aetiologies, juvenile dermatomyositis (jDM) being by far the most frequent entity. The exact diagnostic workup and precise assessment of muscular as well as extramuscular involvement of organs in these systemic autoimmune diseases are relevant for specific and adjunct treatment of complications. Many new insights have become available with respect to the pathophysiological concepts as well as modern diagnostic measures and therapeutic approaches. Autoantibody detection in the serum of children with myositis is one of the major novelties that has become widely used and that is indeed helpful for diagnostic and prognostic measures. The pathophysiological relevance of type I interferons in jDM has been studied intensively in the past years. jDM is now seen as an acquired interferonopathy and first therapeutic consequences have been drawn from this pathogenic finding with the use of Janus-kinase inhibitors for severe and not otherwise treatable children.

Updates on Juvenile Dermatomyositis from the Last Decade: Classification to Outcomes

Juvenile dermatomyositis (JDM) is a heterogeneous disease with new classification criteria and updates in myositis-specific autoantibody and myositis-associated antibody groups. There are many validated assessment tools for assessing disease activity in JDM. Future studies will optimize these tools and improve feasibility in clinical and research contexts. Genetic and environmental risk factors, mechanisms of muscle pathology, role of interferon, vascular markers, and changes in immune cells provide insights to JDM pathogenesis. Outcomes have improved, but chronic disease, damage, and mortality highlight the need for better outcome predictors and treatments. Increased collaboration of stakeholders may help overcome research barriers and improve JDM treatment.

Updates on interferon in juvenile dermatomyositis: pathogenesis and therapy

PURPOSE OF REVIEW

This review provides updates regarding the role of interferon (IFN) in juvenile dermatomyositis (JDM), including comparison to interferonopathies and therapeutic implications.

RECENT FINDINGS

Transcriptomic and protein-based studies in different tissues and peripheral IFN-α assessment have demonstrated the importance of the dysregulated IFN pathway in JDM. Additional studies have validated IFN-regulated gene and protein expression correlation with disease activity in blood and muscle, with potential to predict flares. Type I and II IFN both are dysregulated in peripheral blood and muscle, with more type I IFN in skin. Muscle studies connects hypoxia to IFN production and IFN to vascular dysfunction and muscle atrophy. JDM overlaps with interferonopathy phenotype and IFN signature. There are multiple case reports and case series noting decreased IFN markers and clinical improvement in refractory JDM with Janus kinase (JAK) inhibitors.

SUMMARY

Studies confirm IFN, particularly type I and II IFN, is an important part of JDM pathogenesis by the level of dysregulation and correlation with disease activity, as well as IFN recapitulating key JDM muscle pathology. Smaller studies indicate there may be differences by myositis-specific autoantibody group, but validation is needed. JAK inhibitors are a promising therapy as they can inhibit IFN signaling, but further study is needed regarding which patients will benefit, dosing, and safety monitoring.

Differential levels of IFNα subtypes in autoimmunity and viral infection

Type I interferons are essential for host response to viral infections, while dysregulation of their response can result in autoinflammation or autoimmunity. Among IFNα (alpha) responses, 13 subtypes exist that signal through the same receptor, but have been reported to have different effector functions. However, the lack of available tools for discriminating these closely related subtypes, in particular at the protein level, has restricted the study of their differential roles in disease. We developed a digital ELISA with specificity and high sensitivity for the IFNα2 subtype. Application of this assay, in parallel with our previously described pan-IFNα assay, allowed us to study different IFNα protein responses following cellular stimulation and in diverse patient cohorts. We observed different ratios of IFNα protein responses between viral infection and autoimmune patients. This analysis also revealed a small percentage of autoimmune patients with high IFNα2 protein measurements but low pan-IFNα measurements. Correlation with an ISG score and functional activity showed that in this small sub group of patients, IFNα2 protein measurements did not reflect its biological activity. This unusual phenotype was partly explained by the presence of anti-IFNα auto-antibodies in a subset of autoimmune patients. This study reports ultrasensitive assays for the study of IFNα proteins in patient samples and highlights the insights that can be obtained from the use of multiple phenotypic readouts in translational and clinical studies.

Type I Interferons in the Pathogenesis and Treatment of Autoimmune Diseases

Type I interferons (IFN-Is) are a very important group of cytokines that are produced by innate immune cells but also act on adaptive immune cells. IFN-Is possess antiviral, antitumor, and anti-proliferative effects, as well are associated with the initiation and maintenance of autoimmune disorders. Studies have shown that aberrantly expressed IFN-Is and/or type I IFN-inducible gene signatures in the serum or tissues of patients with autoimmune disorders are linked to their pathogenesis, clinical manifestations, and disease activity. Type I interferonopathies with mutations in genes impacting the type I IFN signaling pathway have shown symptoms and characteristics similar to those of systemic lupus erythematosus (SLE). Furthermore, both interventions in animal models and clinical trials of therapies targeting the type I IFN signaling pathway have shown efficacy in the treatment of autoimmune diseases. Our review aims to summarize the functions and targeted therapies (as well as clinical trials) of IFN-Is in both adult and pediatric autoimmune diseases, such as SLE, pediatric SLE (pSLE), rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), juvenile dermatomyositis (JDM), Sjögren syndrome (SjS), and systemic sclerosis (SSc), discussing the potential abnormal regulation of transcription factors and epigenetic modifications and providing a potential mechanism for pathogenesis and therapeutic strategies for future clinical use.

From Diagnosis to Prognosis: Revisiting the Meaning of Muscle ISG15 Overexpression in Juvenile Inflammatory Myopathies

OBJECTIVE

Juvenile idiopathic inflammatory/immune myopathies (IIMs) constitute a highly heterogeneous group of disorders with diagnostic difficulties and prognostic uncertainties. Circulating myositis-specific autoantibodies (MSAs) have been recognized as reliable tools for patient substratification. Considering the key role of type I interferon (IFN) up-regulation in juvenile IIM, we undertook the present study to investigate whether IFN-induced 15-kd protein (ISG-15) could be a reliable biomarker for stratification and diagnosis and to better elucidate its role in juvenile IIM pathophysiology.

METHODS

The study included 56 patients: 24 with juvenile dermatomyositis (DM), 12 with juvenile overlap myositis (OM), 10 with Duchenne muscular dystrophy, and 10 with congenital myopathies. Muscle biopsy samples were assessed by immunohistochemistry, immunoblotting, and real-time quantitative polymerase chain reaction. Negative regulators of type I IFN (ISG15 and USP18) and positive regulators of type I IFN (DDX58 and IFIH1) were analyzed.

RESULTS

ISG15 expression discriminated patients with juvenile IIM from those with nonimmune myopathies and, among patients with juvenile IIM, discriminated those with DM from those with OM. Among patients with juvenile DM, up-regulation of the type I IFN positive regulators DDX58 and IFIH1 was similar regardless of MSA status. In contrast, the highest levels of the type I IFN negative regulator ISG15 were observed in patients who were positive for melanoma differentiation-associated gene 5 (MDA-5). Finally, ISG15 levels were inversely correlated with the severity of muscle histologic abnormalities and positively correlated with motor performance as evaluated by the Childhood Myositis Assessment Scale and by manual muscle strength testing.

CONCLUSION

Muscle ISG15 expression is strongly associated with juvenile DM, with patients exhibiting a different ISG-15 muscle signature according to their MSA class. Patients with juvenile DM who are positive for MDA-5 have higher expression of ISG15 in both gene form and protein form compared to the other subgroups. Moreover, our data show that negative regulation of type I IFN correlates with milder muscle involvement.

The role of interferons type I, II and III in myositis: A review

The classification of idiopathic inflammatory myopathies (IIM) is based on clinical, serological and histological criteria. The identification of myositis-specific antibodies has helped to define more homogeneous groups of myositis into four dominant subsets: dermatomyositis (DM), antisynthetase syndrome (ASyS), sporadic inclusion body myositis (sIBM) and immune-mediated necrotising myopathy (IMNM). sIBM and IMNM patients present predominantly with muscle involvement, whereas DM and ASyS patients present additionally with other extramuscular features, such as skin, lung and joints manifestations. Moreover, the pathophysiological mechanisms are distinct between each myositis subsets. Recently, interferon (IFN) pathways have been identified as key players implicated in the pathophysiology of myositis. In DM, the key role of IFN, especially type I IFN, has been supported by the identification of an IFN signature in muscle, blood and skin of DM patients. In addition, DM-specific antibodies are targeting antigens involved in the IFN signalling pathways. The pathogenicity of type I IFN has been demonstrated by the identification of mutations in the IFN pathways leading to genetic diseases, the monogenic interferonopathies. This constitutive activation of IFN signalling pathways induces systemic manifestations such as interstitial lung disease, myositis and skin rashes. Since DM patients share similar features in the context of an acquired activation of the IFN signalling pathways, we may extend underlying concepts of monogenic diseases to acquired interferonopathy such as DM. Conversely, in ASyS, available data suggest a role of type II IFN in blood, muscle and lung. Indeed, transcriptomic analyses highlighted a type II IFN gene expression in ASyS muscle tissue. In sIBM, type II IFN appears to be an important cytokine involved in muscle inflammation mechanisms and potentially linked to myodegenerative features. For IMNM, currently published data are scarce, suggesting a minor implication of type II IFN. This review highlights the involvement of different IFN subtypes and their specific molecular mechanisms in each myositis subset.

JAK inhibitors are effective in a subset of patients with juvenile dermatomyositis: a monocentric retrospective study

OBJECTIVE

To evaluate the efficacy and safety of JAK inhibitors (JAKi) in juvenile dermatomyositis (JDM).

METHODS

We conducted a single-center retrospective study of patients with JDM treated by JAKi with a follow-up of at least 6 months. Proportion of clinically inactive disease (CID) within six months of JAKi initiation was evaluated using PRINTO criteria and skin Disease Activity Score. Serum IFN-α concentration was measured by SIMOA assay.

RESULTS

Nine refractory and one new-onset patients with JDM treated with ruxolitinib (n = 7) or baricitinib (n = 3) were included. The main indications for treatment were refractory muscle involvement (n = 8) and ulcerative skin disease (n = 2). CID was achieved in 5/10 patients (2/2 anti-MDA5, 3/4 anti-NXP2, 0/3 anti-TIF1γ positive patients) within six months of JAKi introduction. All responders could withdraw plasmatic exchange, immunoadsorption and other immunosuppressive drugs. The mean daily steroid dose decreased from 1.1 mg/Kg (range 0.35-2 mg/Kg/d) to 0.1 (range, 0-0.3, p= 0.008) in patients achieving CID, and was stopped in two. Serum IFN-α concentrations were elevated in all patients at the time of treatment initiation and normalized in both responder and non-responder. A muscle biopsy repeated in one patient 26 months after the initiation of JAKi, showed a complete restoration of muscle endomysial microvascular bed. Herpes zoster and skin abscesses developed in three and two patients, respectively.

CONCLUSION

JAKis resulted in a CID in a subset of new-onset or refractory patients with JDM and may dramatically reverse severe muscle vasculopathy. Overall tolerance was good except for a high rate of herpes zoster infection.

Successful management with Janus kinase inhibitor tofacitinib in refractory juvenile dermatomyositis: a pilot study and literature review

Objectives

JDM is a rare autoimmune inflammatory muscle disease with a pronounced IFN signature. Treatment for children with JDM has improved over the years with the use of steroids and immunosuppressive agents. However, there remains a subset of children who have refractory disease. Janus kinase and type I IFN signalling production are suspected to contribute to the pathogenesis of JDM. Our pilot study investigated the use of tofacitinib, a Janus kinase inhibitor, in refractory JDM cases to provide new therapeutic options for better treatment.

Methods

Refractory JDM was defined as patients who failed two or more steroid sparing agents or high-dose steroids. Tofacitinib was given to three refractory JDM patients with a dose of 5 mg twice per day for at least 6 months. Core set measures defined by Pediatric Rheumatology International Trials Organization were evaluated at month 0, 3 and 6 along with other systemic evaluations. A literature review was conducted to identify all the cases using Janus kinase inhibitors in JDM.

Results

All three subjects tolerated and responded well to tofacitinib with significant improvement in Child Myositis Assessment Scale, manual muscle testing-8, physician global disease activity and inflammatory indices without occurrence of severe adverse events.

Conclusion

This pilot study showed improvement of muscle strength, resolution of cutaneous lesions, increased daily quality of life and successful tapering of steroids when tofacitinib used in selected cases. Tofacitinib can be considered with caution when treating refractory JDM cases. Further randomized controlled trials are warranted to assess its efficacy in JDM.

Interferon-signature in idiopathic inflammatory myopathies

PURPOSE OF REVIEW

The present review describes the interferon (IFN)-signature currently emerging as a tool for the diagnosis of idiopathic inflammatory myopathies (IIMs), and aims at presenting the interests and limitations of this recent tool for the clinics and the research.

RECENT FINDINGS

Recent in-vivo and in-vitro transcriptomic studies have evidenced the involvement of IFNs in the pathogenesis of IIMs. A correlation between the IFN-signature and the clinical severity of IIMs has been established. Moreover, studies pointed out differences in the IFN-signature regarding the IIM subgroup (dermatomyositis, polymyositis, inclusion body myositis, anti-synthetase syndrome, immuno-mediated necrotizing myopathies), raising the hypothesis of several pathogenic processes in IIMs.

SUMMARY

IIM pathogenesis remains partially understood. IFN-signature represents one of the main recent advances in the field. IFN-signature was identified thanks to transcriptomic analyses of tissues or cells from IIM patients (muscle, skin, blood cells, muscle cells) and should allow to establish new diagnosis and better monitoring of IIM patients. It also provides a tool for investigation of IIM pathogenesis. Nevertheless, IFN-signature still requires accurate definition in order to standardize its use, notably in the clinical practice.

Endothelial and Inflammation Biomarker Profiles at Diagnosis Reflecting Clinical Heterogeneity and Serving as a Prognostic Tool for Treatment Response in Two Independent Cohorts of Patients With Juvenile Dermatomyositis

Objective

Juvenile dermatomyositis (DM) is a heterogeneous systemic immune‐mediated vasculopathy. This study was undertaken to 1) identify inflammation/endothelial dysfunction–related biomarker profiles reflecting disease severity at diagnosis, and 2) establish whether such biomarker profiles could be used for predicting the response to treatment in patients with juvenile DM.

Methods

In total, 39 biomarkers related to activation of endothelial cells, endothelial dysfunction, and inflammation were measured using multiplex technology in serum samples from treatment‐naive patients with juvenile DM from 2 independent cohorts (n = 30 and n = 29). Data were analyzed by unsupervised hierarchical clustering, nonparametric tests with correction for multiple comparisons, and Kaplan‐Meier tests with Cox proportional hazards models for analysis of treatment duration. Myositis‐specific antibodies (MSAs) were measured in the patients’ serum using line blot assays.

Results

Severe vasculopathy in patients with juvenile DM was associated with low serum levels of intercellular adhesion molecule 1 (Spearman's rho [r_s] = 0.465, P = 0.0111) and high serum levels of endoglin (r_s = −0.67, P < 0.0001). In the discovery cohort, unsupervised hierarchical clustering analysis of the biomarker profiles yielded 2 distinct patient clusters, of which the smaller cluster (cluster 1; n = 8) exhibited high serum levels of CXCL13, CCL19, galectin‐9, CXCL10, tumor necrosis factor receptor type II (TNFRII), and galectin‐1 (false discovery rate <0.0001), and this cluster had greater severity of muscle disease and global disease activity (each P < 0.05 versus cluster 2). In the validation cohort, correlations between the serum levels of galectin‐9, CXCL10, TNFRII, and galectin‐1 and the severity of global disease activity were confirmed (r_s = 0.40–0.52, P < 0.05). Stratification of patients according to the 4 confirmed biomarkers identified a cluster of patients with severe symptoms (comprising 64.7% of patients) who were considered at high risk of requiring more intensive treatment in the first 3 months after diagnosis (P = 0.0437 versus other cluster). Moreover, high serum levels of galectin‐9, CXCL10, and TNFRII were predictive of a longer total treatment duration (P < 0.05). The biomarker‐based clusters were not evidently correlated with patients’ MSA serotypes.

Conclusion

Results of this study confirm the heterogeneity of new‐onset juvenile DM based on serum biomarker profiles. Patients with high serum levels of galectin‐9, CXCL10, TNFRII, and galectin‐1 may respond suboptimally to conventional treatment, and may therefore benefit from more intensive monitoring and/or treatment.

[Severe MDA5 dermatomyositis associated with cancer and controlled by JAK inhibitor]

Dermatomyositis is an idiopathic inflammatory myopathy with various clinical and serological profiles, including poor prognosis forms for which aggressive immunosuppressive treatment is warranted. We report the case of a 60-year-old woman referred to our hospital for an anti-melanoma differentiation-associated 5 gene antibody-positive dermatomyositis (MDA5 DM) with rapidly progressive interstitial pneumonia, typical cutaneous features and muscular impairment. Treatment with high-dose methylprednisolone, cyclophosphamide and gamma globulin was performed, but the patient remained corticodependant. Blood detection of positive interferon signature justified the administration of an anti-JAK1/2, leading to the clinical remission and the regression of the interferon signature. After 12 months of follow up, a small cell carcinoma was discovered, raising the question of a paraneoplastic syndrome, for which the most recent datas are quite reassuring for this kind of MDA5 DM. The presentation of this case is of twofold interest: describing one of the first report of successful treatment of intereronopathy MDA5 DM with ruxolitinib and highlighting an association with a cancer, which is not expected for this phenotype of dermatomyositis.

Endothelial Activation Markers as Disease Activity and Damage Measures in Juvenile Dermatomyositis

OBJECTIVE

Circulating endothelial cells (CEC), von Willebrand factor (vWF) antigen, P-selectin, and thrombomodulin are released from damaged endothelium, while decreases in circulating endothelial progenitor cells (CEPC) have been associated with poor vascular outcomes. We examined these markers in the peripheral blood of patients with juvenile dermatomyositis (JDM) and their correlations with disease assessments.

METHODS

Peripheral blood endothelial cells and biomarkers were assessed in 20 patients with JDM and matched healthy controls. CEC and CEPC were measured by flow cytometry, while vWF antigen and activity, factor VIII, P-selectin, and thrombomodulin were measured in plate-based assays. Disease activity and damage, nailfold capillary density, and brachial artery flow dilation were assessed. Serum cytokines/chemokines were measured by Luminex.

RESULTS

CEC, vWF antigen, factor VIII, and thrombomodulin, but not vWF activity, CEPC, or P-selectin, were elevated in the peripheral blood of patients with JDM. CEC correlated with pulmonary activity (r_s = 0.56). The vWF antigen correlated with Patient's/Parent's Global, cutaneous, and extramuscular activity (r_s = 0.47-0.54). CEPC negatively correlated with muscle activity and physical function (r_s = -0.52 to -0.53). CEPC correlated inversely with endocrine damage. The vWF antigen and activity correlated with interleukin 10 and interferon-gamma inducible protein-10 (r_s = 0.64-0.82).

CONCLUSION

Markers of endothelial injury are increased in patients with JDM and correlate with extramuscular activity. CEPC correlate inversely with muscle activity, suggesting a functional disturbance in repair mechanisms.

Distinct interferon signatures stratify inflammatory and dysimmune myopathies

Objective

The role of interferons (IFN) in the pathophysiology of primary inflammatory and dysimmune myopathies (IDM) is increasingly investigated, notably because specific neutralisation approaches may constitute promising therapeutic tracks. In present work we analysed the muscular expression of specific IFNα/β and IFNγ-stimulated genes in patients with various types of IDM.

Methods

39 patients with IDM with inclusion body myositis (IBM, n=9), dermatomyositis (DM, n=10), necrotising autoimmune myopathies (NAM, n=10) and antisynthetase myositis (ASM, n=10), and 10 controls were included. Quantification of expression levels of IFNγ, ISG15, an IFNα/β-inducible gene and of six IFNγ-inducible genes (GBP2, HLA-DOB, HLA-DPB, CIITA, HLA-DRB and HLA-DMB) was performed on muscle biopsy samples.

Results

DM usually associated with strong type I IFNα/β signature, IBM and ASM with prominent type II IFNγ signature and NAM with neither type I nor type II IFN signature. Immunofluorescence study in ASM and IBM showed myofibre expression of major histocompatibility class 2 (MHC-2) and CIITA, confirming the induction of the IFNγ pathway. Furthermore, MHC-2-positive myofibres were observed in close proximity to CD8+ T cells which produce high levels of IFNγ.

Conclusion

Distinct IFN signatures allow a more distinct segregation of IDMs and myofibre MHC-2 expression is a reliable biomarker of type II IFN signature.

Targeting Tregs in Juvenile Idiopathic Arthritis and Juvenile Dermatomyositis-Insights From Other Diseases

Regulatory T cells (Tregs) are believed to be dysfunctional in autoimmunity. Juvenile idiopathic arthritis (JIA) and juvenile dermatomyositis (JDM) result from a loss of normal immune regulation in specific tissues such as joints or muscle and skin, respectively. Here, we discuss recent findings in regard to Treg biology in oligo-/polyarticular JIA and JDM, as well as what we can learn about Treg-related disease mechanism, treatment and biomarkers in JIA/JDM from studies of other diseases. We explore the potential use of Treg immunoregulatory markers and gene signatures as biomarkers for disease course and/or treatment success. Further, we discuss how Tregs are affected by several treatment strategies already employed in the therapy of JIA and JDM and by alternative immunotherapies such as anti-cytokine or co-receptor targeting. Finally, we review recent successes in using Tregs as a treatment target with low-dose IL-2 or cellular immunotherapy. Thus, this mini review will highlight our current understanding and identify open questions in regard to Treg biology, and how recent findings may advance biomarkers and new therapies for JIA and JDM.

Systemic and Tissue Inflammation in Juvenile Dermatomyositis: From Pathogenesis to the Quest for Monitoring Tools

Juvenile Dermatomyositis (JDM) is a systemic immune-mediated disease of childhood, characterized by muscle weakness, and a typical skin rash. Other organ systems and tissues such as the lungs, heart, and intestines can be involved, but may be under-evaluated. The inflammatory process in JDM is characterized by an interferon signature and infiltration of immune cells such as T cells and plasmacytoid dendritic cells into the affected tissues. Vasculopathy due to loss and dysfunction of endothelial cells as a result of the inflammation is thought to underlie the symptoms in most organs and tissues. JDM is a heterogeneous disease, and several disease phenotypes, each with a varying combination of affected tissues and organs, are linked to the presence of myositis autoantibodies. These autoantibodies have therefore been extensively studied as biomarkers for the disease phenotype and its associated prognosis. Next to identifying the JDM phenotype, monitoring of disease activity and disease-inflicted damage not only in muscle and skin, but also in other organs and tissues, is an important part of clinical follow-up, as these are key determinants for the long-term outcomes of patients. Various monitoring tools are currently available, among which clinical assessment, histopathological investigation of muscle and skin biopsies, and laboratory testing of blood for specific biomarkers. These investigations also give novel insights into the underlying immunological processes that drive inflammation in JDM and suggest a strong link between the interferon signature and vasculopathy. New tools are being developed in the quest for minimally invasive, but sensitive and specific diagnostic methods that correlate well with clinical symptoms or reflect local, low-grade inflammation. In this review we will discuss the types of (extra)muscular tissue inflammation in JDM and their relation to vasculopathic changes, critically assess the available diagnostic methods including myositis autoantibodies and newly identified biomarkers, and reflect on the immunopathogenic implications of identified markers.

[The effect of interferon-gamma on skeletal muscle cell biology]

Dysimmune and inflammatory myopathies (DIMs) affect around 14/100,000 people worldwide. Based on immupour nopathological criteria, DIMs are divided in four groups: (1) polymyositis (PM)/inclusion body myositis (IBM), (2) dermatomyositis (DM), (3) immune-mediated necrotizing myopathies (IMNM) and (iv) overlapping myositis including anti-synthetase syndrome (ASS). ASS and PM/IBM are characterized by the activation of inflammation with lymphocytic infiltrations. Recently, we showed that an expression of the major histocompatibility complex class 2 (MHC2) was present in myofibers from ASS and IBM muscle biopsies. Interestingly, MHC2 expression is known to be stimulated by Interferon-gamma (IFNγ) in myogenic cells. LTCD8 cells, which are well-known producers of IFNγ, are commonly found in close vicinity to MHC2 positive myofibers. This inflammatory cytokine also inhibits myogenic differentiation in vitro by CIITA-myogenin interaction. The mechanisms involved in the lymphocyte-driven muscle toxicity in DIMs are unclear. The objectives of this project are to characterize IFNγ effects on the biology of human myogenic cells by morphological, molecular and cellular approaches. Then, we aim to investigate the role of IFNγ in these myopathies and its impact during muscular regeneration. In vitro preliminary studies have been performed using human and mouse myoblasts treated or not with IFNγ. Our results should lead to a better understanding of the role of IFNγ in the pathophysiology of DIMs, and would hopefully help identify new therapeutic targets.