Background: The idiopathic inflammatory myopathies (IIM) are a heterogeneous group of rare autoimmune diseases comprising of polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). They are characterised primarily by muscle weakness, and can present with extramuscular manifestations such as skin rashes, interstitial lung disease and malignancy. Aims: This aim of this study was to identify novel genetic risk factors in IIM and to further elucidate the relationship between genotype and serotype. Methods: 2,566 IIM samples were collected from 14 countries through the Myositis Genetics Consortium (MYOGEN) and genotyped on the Immunochip, a custom array covering 186 established autoimmune susceptibility loci. SNP2HLA was used to impute classical HLA alleles and constituent amino acids. Results: In a combined IIM analysis, the HLA region and PTPN22 reached genome-wide significance (p<5x10-8). A further nine regions reached suggestive significance (p<2.25x10-5) including UBE2L3, STAT4 and CD28 that have been implicated in autoimmune disease previously. Independent effects were seen within the STAT4 region. In a PM subgroup analysis (n=931), the HLA region and PTPN22 reached genome-wide significance. A further seven regions reached suggestive significance including SLC26A1/IDUA and RGS1. In an adult and juvenile DM analysis (n=1,360), only the HLA region reached genome wide significance. Three loci reached suggestive significance including GSDMB. In the IBM analysis (n=252), only the HLA region reached genome wide significance and 3 loci reached suggestive significance, including the CCR2 locus. Identification of exonic and eQTL SNPs has localised association signals to several potential causal variants. HLA imputation on the combined dataset confirmed that alleles of the 8.1 ancestral haplotype (AH) are most strongly associated with IIM. The cohort was stratified in to clinical subgroups. In PM the strongest effect was found with HLA-DRB1*03:01 with an independent effect with HLA-B*08:01. Amino acid position 74 lies within the peptide binding groove and may explain the risk in HLA-DRB1. HLA-B*08:01 was the most associated variant in both DM and JDM, with independent effects of amino acid position 57 of HLA-DQB1 in DM and HLA-C*02:02 in JDM. In IBM, the strongest associations were with amino acids positions 26 and 11 of HLA-DRB1.HLA imputation was conducted on antibody subgroups. The most associated variant for anti-Jo-1 and anti-PM/Scl antibodies was with amino acid 74 of HLA-DRB1. Alleles of the 8.1 AH were most associated with anti-TIF1-γ, anti-SAE and anti-cN1A antibodies. Alleles independent of the 8.1 AH were replicated such as anti-Mi-2 antibodies and HLA-DRB1*07:01, and anti-HMGCR antibodies and HLA-DRB1*11. Conclusions: This represents the largest study to date in IIM and has considerably expanded our knowledge about the genetic architecture of this rare disease. This study has identified novel disease susceptibility genes for IIM and independent associations with PM and DM, IBM and antibody subgroups that show that stratifying patients in to more homogenous cohorts is important to expand our knowledge of IIM. Ongoing sample collection is required to identify additional genes and environmental risk factors that lead to the development of IIM, and to expand our limited understanding of the pathogenesis of this disease.

Introduction: Idiopathic inflammatory myopathies (myositis, IIM) are heterogeneous group of rare autoimmune systemic diseases, characterized particularly by proximal skeletal muscle weakness. Heretogeneity of myositis is based on different pathogenetic mechanisms which may be reflected by variable imunophenotypic response in individual subtypes. Objectives: The aim of this work was to explore the associations and influence of soluble factors of immune system in patient's sera on phenotypic characteristics and subtypes of IIM, to describe their expression in inflammed muscle tissue and study their eventual role in pathogenesis by analysis of effect on immune and muscle cells in vitro. Results: We have described prevalence and characteristics of joint involvement in myositis patients and its significant association with anti-Jo-1 autoantibody. Further we confirmed the relation of anti-HMGCR antibody to immune mediated necrotizing myopathy, its tight relation to statins and recent increase in incidence. We showed inverse association of IFNα serum levels with muscle activity detected on MRI. Clinical activity positively correlated with IFN type-I pathway activation in patients with dermatomyositis. We also show positive correlation of resistin levels and clinical activity and correlation of activity...

Introduction: Idiopathic inflammatory myopathies (myositis, IIM) are heterogeneous group of rare autoimmune systemic diseases, characterized particularly by proximal skeletal muscle weakness. Heretogeneity of myositis is based on different pathogenetic mechanisms which may be reflected by variable imunophenotypic response in individual subtypes. Objectives: The aim of this work was to explore the associations and influence of soluble factors of immune system in patient's sera on phenotypic characteristics and subtypes of IIM, to describe their expression in inflammed muscle tissue and study their eventual role in pathogenesis by analysis of effect on immune and muscle cells in vitro. Results: We have described prevalence and characteristics of joint involvement in myositis patients and its significant association with anti-Jo-1 autoantibody. Further we confirmed the relation of anti-HMGCR antibody to immune mediated necrotizing myopathy, its tight relation to statins and recent increase in incidence. We showed inverse association of IFNα serum levels with muscle activity detected on MRI. Clinical activity positively correlated with IFN type-I pathway activation in patients with dermatomyositis. We also show positive correlation of resistin levels and clinical activity and correlation of activity...

Introduction: Recent findings and better understanding to the pathogenesis of rheumatic diseases contributed to the development of biological therapies targeting cytokines and immune cells. Several S100 proteins exert cytokine-like effects and participate in the regulation of the inflammatory process. The aim of this work was to study the role of selected S100 proteins in the activity and in the pathogenesis of the rheumatic diseases. Results: Our data show for the first time an association of S100A4 proteinwith RA disease activity and decrease of the bioactive form, but not the total amount of S100A4, after aplication of tumour necrosis factor (TNF) blocking biologic therapy in patients with RA. We demonstrated that in vitro S100A4 acts as a potent pro-inflammatory mediator inducing production of TNFα, interleukin (IL)-1β and IL-6 in PBMCs via Toll-like receptor 4 (TLR-4), transcription factor NFκB and tyrosine kinases erk1/2 and p38. Moreover, S100A4 can play an important role in the pathogenesis of inflammatory myopathies. S100A4 is present in the inflammatory infiltrate of the affected muscles and in the regenerating muscles and may act as a cytokine-like factor indirectly promoting muscle fiber damage by stimulating mononuclear cells to increase the synthesis of pro-inflammatory cytokines. We...

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Les myopathies inflammatoires (MI) représentent un groupe hétérogène de maladies caractérisépar une faiblesse musculaire chronique et symétrique associée à une augmentation du taux sérique decréatine phosphokinase (CPK). Les MI sont actuellement subdivisées en 5 entitées : les dermatomyosites,les myopathies nécrosantes auto-immunes, la myosite à inclusion, la polymyosite et les myosites dechevauchement. A ce jour, le diagnostic des MI repose sur l’association de signes cliniques, decaractéristiques anatomopathologiques sur la biopsie musculaire et la présence d’auto-anticorps (aAc). Eneffet, la découverte d’aAc spécifiques et/ou associés aux myosites (MSA/MAA) a considérablementamélioré le diagnostic et le pronostic de la maladie. Cependant, un nombre non négligeable de patientsatteints de MI sont séronégatifs pour les MSA/MAA connus. Par ailleurs, la biopsie musculaire nécessaireau diagnostic est parfois guidée par imagerie par résonance magnétique (IRM), bien qu’il n’ait pas étéprouvé que les données d’imagerie soient corrélées aux signes histologiques. Enfin, le traitement des MIrepose sur l’utilisation d’immunosuppresseurs systémiques, une approche non spécifique de laphysiopathologie de la maladie. Les modèles animaux de MI les plus utilisés sont induits et nonspontanés : ils reposent principalement sur l’immunisation d’animaux contre des protéines telles que lamyosine, la protéine C ou l’histidyl-tRNA synthétase.Les souris NOD (non obese diabetic) sont le modèle classique d’étude du diabète de type 1.Lorsque ces souris sont invalidées pour la voie de costimulation lymphocytaire ICOS/ICOSL, les souris nedéveloppent plus de diabète mais présentent alors une atteinte musculaire. Dans ce travail, nous avonsétudié le phénotype et caractérisé l’atteinte musculaire des souris NOD Icos-/- et NOD Icosl-/-. Nous avonsainsi établi le 1er modèle murin spontané de MI, dont la physiopathologie est médiée par leslymphocytes T CD4+ et la sécrétion d’IFN-γ. Par ailleurs, ces souris présentent un déficit en lymphocytes Trégulateurs. Nous avons également identifié 4 auto-antigènes (aAg) candidats cibles d’aAc chez ces souris.La recherche des aAc correspondants aux aAg orthologues dans le sérum des patients atteints de MI apermis d’identifier, pour l’un d’entre eux, une minorité d’individus séropositifs grâce au développementd’un nouveau test ALBIA (addressable laser bead immunoassay). Il pourrait donc s’agir d’un nouveaubiomarqueur. Dans la perspective de nouvelles évaluations thérapeutiques, nous avons établi desdonnées préliminaires montrant que l’interleukine 2 à faibles doses permet de retarder l’apparition de lamaladie. Enfin, nous avons mis à profit ce modèle et démontré la corrélation entre les données généréespar IRM et par analyse histologique de l’inflammation, confortant le rôle de cette technique d’imagerie àla fois pour le diagnostic et le suivi des MI. / Inflammatory Myopathies (IM) are a heterogeneous group of diseases characterized bychronic and symmetrical muscle weakness associated to increased creatine phosphokinase (CPK)levels, according to entity concerned. Currently, IM are divided into 5 main entities:dematomyositis, immune-mediated necrotizing myopathies, inclusion body myositis, polymyositisand overlap myositis. Nowadays, IM diagnosis is based on clinical signs associated to pathologicfeatures on muscle biopsy and presence of auto-antibodies (aAb). Indeed, the discovery of myositisspecific and/or associated auto-antibodies (MSA/MAA) had considerably improve disease diagnosisand prognosis. However, substantial proportion of IM patients do not display any knownMSA/MAA. Furthermore, diagnosis requires muscle biopsy. This biopsy is sometimes guided bymagnetic resonance imaging (MRI), even though correlation between MRI findings and pathologicalfeatures is not established. Lastly, therapeutics used in IM treatment are systemicimmunosuppressive agents, i.e. not specific to IM pathophysiology. Animal models of IM are mainlybased on active immunization against different proteins as myosin, C protein orhistidyl-tRNA synthetase, while spontaneous models are required to identify pathophysiologicalmechanisms that new therapeutics should target.NOD (non obese diabetic) mice are the main model of type 1 diabetes. When invalidatedfor ICOS/ICOSL costimulation pathway, these mice do not develop diabetes but present musculardisorders. In this work, we study Icos-/- and Icosl-/- NOD mice phenotype and characterize theremuscle lesion. Thus, we have established this model as the first paradigm of IM. Pathophysiologicalstudy in these mice demonstrated that disease is CD4+ T cell dependent and associated to IFN-γproduction. Furthermore, we shown a quantitative defect in regulatory T cells. We have alsoidentified 4 candidate autoantigens (aAg) in Icos-/- and Icosl-/- NOD mice. Searching forcorresponding aAb against ortholog proteins in patients with IM, we identified for one of them, alow percentage of seropositive individuals using a new ALBIA (addressable laser beadimmunoassay). It could be identified as a new biomarker. In order to evaluate new therapies, weestablished preliminary data showing that low dose interleukin 2 therapy allow to delay diseaseonset. Lastly, we took advantage of this new model to demonstrate the correlation betweenMRI findings and histological inflammation features, confirming the valuable role of MRI for thediagnosis and monitoring of IM.

Les myopathies auto-immunes (MAI), classiquement appelées myosites ou myopathies inflammatoires idiopathiques, représentent un groupe de maladies définies par des caractéristiques cliniques, histopathologiques et biologiques. Une des caractéristiques les plus notables est la présence d’auto-anticorps (aAc) chez environ 60% des patients. Les MAI regroupent : les dermatomyosites, les polymyosites, les myosites à inclusion, les myosites de chevauchement incluant le syndrome des anti-synthétases et les myopathies nécrosantes auto-immunes (MNAI). Les MNAI ont été récemment individualisées parmi les MAI comme des maladies graves fréquemment associées à la présence d’aAc dirigés contre la Signal Recognition Particle (SRP) ou la 3-Hydroxy-3-MéthylGlutaryl-CoA Réductase (HMGCR). La localisation de SRP et HMGCR étant intracellulaire, le rôle des aAc dans la physiopathologie des MNAI reste mal compris. La pathogénicité des aAc anti-SRP et anti-HMGCR envers des cellules musculaires cultivées in vitro a récemment été mise en évidence mais leurs effets in vivo demeurent inconnus.Au cours de cette thèse, j’ai étudié le rôle physiopathologique des aAc anti-SRP et anti-HMGCR in vivo chez la souris. Le transfert passif d’IgG de patients atteints de MNAI, positifs pour les aAc anti-SRP ou anti-HMGCR, à la souris sauvage entraîne un déficit musculaire. Ce déficit était prolongé chez la souris immunodéficiente Rag2-/-, et limité chez la souris déficiente pour la fraction C3 du complément. Chez les souris recevant les IgG anti-SRP+, le déficit musculaire était important et accompagné de quelques signes de nécrose myocytaire. Les IgG anti-HMGCR+ induisaient une faiblesse musculaire moindre, et des signes histopathologiques rares ou absents. Ces résultats sont en accord avec l’observation chez l’homme d’une maladie plus grave chez les patients anti-SRP+ par rapport aux patients anti-HMGCR+. La supplémentation en complément humain des souris augmentait le déficit musculaire induit par les IgG anti-HMGCR+ et de façon moindre pour les IgG anti-SRP+. En collaboration avec l’INSERM UMRS974, nous avons montré que les cibles SRP et HMGCR peuvent être détectées à la surface des fibres musculaires in vitro, suggérant qu’elles puissent être accessibles aux aAc in vivo.Ces résultats démontrent pour la première fois le rôle pathogène des aAc anti-SRP et anti-HMGCR in vivo et l’implication du complément, contribuant à une avancée dans la compréhension de la physiopathologie des MNAI. / Autoimmune myopathies (AIM), classically called myositis or idiopathic inflammatory myopathies, represent a group of diseases characterized by clinical, histopathologic and biologic properties. One of the most notable properties is the presence of autoantibodies (aAb) in approximately 60% of patients. AIM includes five principal entities: dermatomyositis, polymyositis, inclusion body myositis, overlap myositis including the anti-synthetase syndrome and immune-mediated necrotizing myopathies (IMNM). IMNM have recently been individualized among AIM as severe diseases frequently associated with aAb directed against Signal Recognition Particle (SRP) or 3-Hydroxy-3-MethylGlutaryl-CoA Reductase (HMGCR). Since SRP and HMGCR have an intracellular localization, the role of anti-SRP and anti-HMGCR aAb in the pathophysiology of IMNM remains unclear. Anti-SRP and anti-HMGCR aAb were recently shown to be pathogenic to muscle cells in vitro but in vivo effects remain unknown.During this thesis, I studied the pathophysiological role of anti-SRP and anti-HMGCR aAb in vivo in mice. Passive transfer of IgG purified from plasma of IMNM patients positive for anti-SRP and anti-HMGCR aAb to wild-type mice elicited a muscle weakness. Immune-deficient Rag2-/- mice presented a prolonged muscle deficit, whereas complement component C3 deficient mice had limited signs. Mice injected with anti-SRP+ IgG displayed a strong muscle weakness with mild myocytic necrosis. The muscle deficit was milder and histopathologic findings were not always present in mice receiving anti-HMGCR+ IgG. This is in accordance with clinical findings in anti-SRP+ patients which present a more severe disease than anti-HMGCR+ patients. When supplemented with human complement, mice receiving anti-HMGCR+ IgG showed a more severe muscle deficit. This supplementation increased the deficit induced by anti-SRP IgG in a milder way. In collaboration with INSERM UMRS974, we showed that the targets SRP and HMGCR can be detected on the surface of myofibres in vitro, suggesting that they could be accessible to aAb in vivo.Together, these results demonstrate for the first time the pathogenic role of anti-SRP and anti-HMGCR aAb in vivo and the implication of complement, contributing to a progress in the comprehension of MNAI pathophysiology.

Title: Body composition in patients with idiopatic inflammatory myopathies Objectives: The aim of this study was to compare selected parameters of body composition in patients with idiopathic inflammatory myopathies (IIM) with age- and sex-matched healthy controls (HC). Another objective was to evaluate the effect of selected clinical parameters in patients with IIM on the detectedvariability of the parameters of body composition and on physical activity of patients. Methods: The research sample consisted of 84 individuals (54 IIM, 30 HC). In anthropometry, we measured: body height (cm), weight (kg) and BMI (kg/m2 ). Using bioelectrical impedance analysis BIA 2000-M we obtained values: total body water (TBW in%), muscle mass (LBM in kg), body fat (BF in%) cell mass of lean body mass (BCM of FFM in%), and the proportion of extracellular/intracellular matrix (ECM/BCM). Using Lunar series iDXA we obtained values: muscle mass (LBM in kg), body fat (BF in %), bone mineral density (BMD in g/cm3 ), and visceral fat (Visceral in kg). To these measured values we added a questionnaire on physical activity Human Acitvity Profile (HAP). Statistics: T-test, Mann Whitney U test, Cohen's d, and Partialeta-squared. Results: Selected values (mean ± SD): body height: IIM 164.7 ± 9.1 cm, HC 170.3 ± 7 cm; body weight:...

Introduction: This work focused on two rare rheumatic diseases systemic sclerosis (SSc) and idiopathic inflammatory myopathies (IIM). Skin and musculoskeletal involvement in patients with SSc leads to disability and loss of functional abilities of an individual. Chronic inflammation of the muscles, subsequent muscle atrophy and permanent muscle damage in patients with IIM are the cause of a decrease in muscle strength and endurance. Moreover, both diseases also affect internal organs and manifest often with impaired lung and heart function. All of these involvements in both diseases lead to a decrease in the quality of life of patients. The data on efficacy of non-pharmacological care in SSc and IIM are very limited due to the heterogeneity of the studied interventions and/or outcomes. However, due to limitations in pharmacological therapy, non-pharmacological interventions could help bring patients back into their everyday life and improve their quality of life. Objectives: The main objective of this project was to evaluate the impact of physical intervention on disease course and activity in a substantial number of SSc and IIM patients, with the aim of minimizing the limitations of available studies, thereby improving the quality and reliability of the obtained results. Methods: This is a...

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of chronic muscle diseases with frequent extramuscular organ involvement that contributes to serious prognosis. The presence of autoantibodies and composition of muscle infiltrates both support autoimmune nature of the disease and pathogenic role of B lymphocytes. Besides the traditional diagnostic subgroups, autoantibody characterised phenotype subsets have been identified with presumed similar pathogenic mechanisms. The best known is the antisynthetase syndrome which is characterised by presence of myositis, antisynthetase autoantibodies (with anti-Jo-1 being the most frequent), interstitial lung disease and other extramuscular manifestations. BAFF (B cell-Activating Factor of the TNF Family) is a key factor in B cell homeostasis modulation. In high levels, it allows survival of autoreactive B cell clones and thus participates in the pathogenesis of autoimmune diseases. Its expression is induced by type I interferons (IFN-1). The aim of the PhD thesis was to explore the role of BAFF in pathogenesis of IIMs by analysis of its serum levels, the receptors for BAFF in muscle tissue, their associations to IFN-1 and expression of BAFF gene mRNA transcription variants in peripheral blood cells. Further aspect was to study a possible...