Perivascular and endomysial macrophages expressing VEGF and CXCL12 promote angiogenesis in anti-HMGCR immune-mediated necrotizing myopathy.

OBJECTIVES: To study the phenotype of macrophage infiltrates and their role in angiogenesis in different idiopathic inflammatory myopathies (IIMs). METHODS: The density and distribution of the subpopulations of macrophages subsets (M1, inducible nitric oxide+, CD11c+; M2, arginase-1+), endomysial capillaries (CD31+, FLK1+), degenerating (C5b-9+) and regenerating (NCAM+) myofibres were investigated by immunohistochemistry in human muscle samples of diagnostic biopsies from a large cohort of untreated patients (n: 81) suffering from anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (anti-HMGCR)+ immune mediated necrotizing myopathy (IMNM), anti-signal recognition particle (anti-SRP)+ IMNM, seronegative IMNM, DM, PM, PM with mitochondrial pathology, sporadic IBM, scleromyositis, and anti-synthetase syndrome. The samples were compared with mitochondrial myopathy and control muscle samples. RESULTS: Compared with the other IIMs and controls, endomysial capillary density (CD) was higher in anti-HMGCR+ IMNM, where M1 and M2 macrophages, detected by confocal microscopy, infiltrated perivascular endomysium and expressed angiogenic molecules such as VEGF-A and CXCL12. These angiogenic macrophages were preferentially associated with CD31+ FLK1+ microvessels in anti-HMGCR+ IMNM. The VEGF-A+ M2 macrophage density was significantly correlated with CD (rS: 0.98; P: 0.0004). Western blot analyses revealed increased expression levels of VEGF-A, FLK1, HIF-1α and CXCL12 in anti-HMGCR+ IMNM. CD and expression levels of these angiogenic molecules were not increased in anti-SRP+ and seronegative IMNM, offering additional, useful information for differential diagnosis among these IIM subtypes. CONCLUSION: Our findings suggest that in IIMs, infiltrating macrophages and microvascular cells interactions play a pivotal role in coordinating myogenesis and angiogenesis. This reciprocal crosstalk seems to distinguish anti-HMGCR associated IMNM.

Long-term efficacy of adding intravenous immunoglobulins as treatment of refractory dysphagia related to myositis: a retrospective analysis.

OBJECTIVE: Dysphagia is a life-threating manifestation of idiopathic inflammatory myopathies (IIM). However, we lack a univocal protocol for its treatment. The aim of this retrospective analysis was to evaluate the effectiveness of a step-up strategy by adding a 1-day pulse of IVIGs to immunosuppressants in IIM patients with refractory dysphagia diagnosed by Eating Assessment Tool (EAT)-10 and fibreoptic endoscopic evaluation of swallowing (FEES). METHODS: Dysphagia was defined as a pharyngo-oesophageal disturbance associated with EAT-10 score ≥3 and at least one FEES abnormality among propulsion failure, solid or liquid stasis. Eighteen out of 154 IIM patients had FEES-confirmed dysphagia and underwent 1 day IVIG 2 g/kg repeated 1 month apart for 3 months, because of dysphagia refractory to high-dose glucocorticoids with methotrexate and/or azathioprine. Clinical characteristics along with myositis-specific antibodies and muscle histopathological findings were studied in FEES-dysphagia IIM and IIM control patients. RESULTS: After three monthly doses of IVIG, EAT-10 score dropped with complete recover of defective propulsion and progressive decrease in percentage of both solid and liquid stasis. At 52-weeks' follow-up, reached in 12 patients, all these parameters were stable or further improved. An improvement in manual muscle strength test and a steroid-sparing effect of IVIG were also observed. Anti-PM/Scl 75/100 antibodies were much more frequent in the FEES-dysphagia group, while anti-Jo1 antibody was rarely detected. CONCLUSION: Our treatment schedule with 2 g/kg IVIG was effective for IIM-associated refractory dysphagia assessed by the combination of EAT-10 and FEES. These findings need to be prospectively tested in a larger cohort of IIM patients.

Severe muscle damage with myofiber necrosis and macrophage infiltrates characterize anti-Mi2 positive dermatomyositis.

OBJECTIVE: The aim of our study was to investigate clinical and histopathological findings in adult DM patients positive for anti-Mi2 (anti-Mi2+) antibodies compared with DM patients negative for anti-Mi2 (anti-Mi2-). METHODS: Clinical data of adult DM patients, who fulfilled EULAR/ACR 2017 classification criteria, were gathered from electronic medical records of three tertiary Rheumatology Units. Histopathological study was carried out on 12 anti-Mi2+ and 14 anti-Mi2- muscle biopsies performed for diagnostic purpose. Nine biopsies from immune mediated necrotizing myopathy (IMNM) patients were used as control group. RESULTS: Twenty-two anti-Mi2+ DM [90.9% female, mean age 56.5 (15.7) years] were compared with 69 anti-Mi2- DM patients [71% female, mean age 52.4 (17) years]. Anti-Mi2+ patients presented higher levels of serum muscle enzymes than anti-Mi2- patients [median (IQR) creatine-kinase fold increment: 16 (7-37)vs 3.5 (1-9.9), P <0.001] before treatment initiation. Moreover, a trend towards less pulmonary involvement was detected in anti-Mi2+ DM (9.1% vs 30.4%, P =0.05), without any case of rapidly progressive interstitial lung disease. At muscle histology, anti-Mi2+ patients showed more necrotic/degenerative fibres than anti-Mi2- patients [mean 5.3% (5) vs 0.8% (1), P <0.01], but similar to IMNM [5.9% (6), P >0.05]. In addition, the endomysial macrophage score was similar between anti-Mi2+ and IMNM patients [mean 1.2 (0.9) vs 1.3 (0.5), P >0.05], whereas lower macrophage infiltration was found in anti-Mi2- DM [mean 0.4 (0.5), <0.01]. CONCLUSIONS: Anti-Mi2+ patients represent a specific DM subset with high muscle damage. Histological hallmarks were a higher prevalence of myofiber necrosis, endomysial involvement and macrophage infiltrates at muscle biopsy.

Autophagy markers LC3 and p62 accumulate in immune-mediated necrotizing myopathy.

INTRODUCTION: The molecular mechanism of immune-mediated necrotizing myopathy (IMNM) remains unknown. Autophagy impairment, described in autoimmune diseases, is a key process in myofiber protein degradation flux and muscle integrity and has not been studied in IMNM. METHODS: Muscle biopsies from patients with IMNM (n = 40), dermatomyositis (DM; 24), polymyositis (PM; 8), polymyositis with mitochondrial pathology (4), sporadic inclusion body myositis (8), and controls (6) were compared by immunohistochemistry. RESULTS: The proportions of myofibers containing autophagy markers LC3b and p62 were higher in IMNM than in DM or PM and correlated with creatine kinase levels. In IMNM, compartmentalized LC3b puncta were located in regenerating and degenerating myofibers surrounded by major histocompatibility complex type II+ inflammatory cells. Several IMNM myofibers accumulated ubiquitin and misfolded protein. DISCUSSION: The detection of LC3b+ or p62+ myofibers could be used in differentiating IMNM from PM. The identification of autophagy-modifying molecules potentially could improve patients' outcomes. Muscle Nerve, 2019.

Supramolecular aggregation of aquaporin-4 is different in muscle and brain: correlation with tissue susceptibility in neuromyelitis optica.

Neuromyelitis optica (NMO) is an autoimmune demyelinating disease of the central nervous system (CNS) caused by autoantibodies (NMO-IgG) against the water channel aquaporin-4 (AQP4). Though AQP4 is also expressed outside the CNS, for example in skeletal muscle, patients with NMO generally do not show clinical/diagnostic evidence of skeletal muscle damage. Here, we have evaluated whether AQP4 supramolecular organization is at the basis of the different tissue susceptibility. Using immunofluorescence we found that while the sera of our cohort of patients with NMO gave typical perivascular staining in the CNS, they were largely negative in the skeletal muscle. This conclusion was obtained using human, rat and mouse skeletal muscle including the AQP4-KO mouse. A biochemical analysis using a new size exclusion chromatography approach for AQP4 suprastructure fractionation revealed substantial differences in supramolecular AQP4 assemblies and isoform abundance between brain and skeletal muscle matching a lower binding affinity of NMO-IgG to muscle compared to the brain. Super-resolution microscopy analysis with g-STED revealed different AQP4 organization in native tissues, while in the brain perivascular astrocyte endfoot membrane AQP4 was mainly organized in large interconnected and raft-like clusters, in the sarcolemma of fast-twitch fibres AQP4 aggregates often appeared as small, relatively isolated linear entities. In conclusion, our results provide evidence that AQP4 supramolecular structure is different in brain and skeletal muscle, which is likely to result in different tissues susceptibility to the NMO disease.

Aquaporin-4 orthogonal arrays of particles are the target for neuromyelitis optica autoantibodies.

Neuromyelitis optica (NMO) is an inflammatory autoimmune demyelinating disease of the central nervous system (CNS) which in autoantibodies produced by patients with NMO (NMO-IgG) recognize a glial water channel protein, Aquaporin-4 (AQP4) expressed as two major isoforms, M1- and M23-AQP4, in which the plasma membrane form orthogonal arrays of particles (OAPs). AQP4-M23 is the OAP-forming isoform, whereas AQP4-M1 alone is unable to form OAPs. The function of AQP4 organization into OAPs in normal physiology is unknown; however, alteration in OAP assemblies is reported for several CNS pathological states. In this study, we demonstrate that in the CNS, NMO-IgG is able to pull down both M1- and M23-AQP4 but experiments performed using cells selectively transfected with M1- or M23-AQP4 and native tissues show NMO-IgG epitope to be intrinsic in AQP4 assemblies into OAPs. Other OAP-forming water-channel proteins, such as the lens Aquaporin-0 and the insect Aquaporin-cic, were not recognized by NMO-IgG, indicating an epitope characteristic of AQP4-OAPs. Finally, water transport measurements show that NMO-IgG treatment does not significantly affect AQP4 function. In conclusion, our results suggest for the first time that OAP assemblies are required for NMO-IgG to recognize AQP4.

Optogenetic Interneuron Stimulation and Calcium Imaging in Astrocytes.

In brain networks, neurons are constantly involved in a dynamic interaction with the other cell populations and, particularly, with astrocytes, the most abundant glial cells in the brain. Astrocytes respond to neurotransmitters with Ca2+ elevations which represent a key event in the modulation of local brain circuits played by these glial cells. Due to technical limitations, the study of Ca2+ signal dynamics in astrocytes has focused for decades almost exclusively on somatic and perisomatic regions. Accordingly, Ca2+ signal in astrocytic fine protrusions, which are in close contact with the synapse, has been poorly investigated. Over the last years, the diffusion of novel tools such as the viral vector gene delivery of genetically encoded Ca2+ indicators (GECI), the optogenetics, and multiphoton laser scanning microscopy has boosted significantly our capability to study astrocytic Ca2+ signals in the different subcellular compartments. Here we report a protocol that combines these techniques to study astrocyte Ca2+ signaling in response to somatostatin (SST)-expressing interneurons, one of the main classes of GABAergic inhibitory interneurons.

Correction to: Optogenetic Interneuron Stimulation and Calcium Imaging in Astrocytes.

Figures 1 and 2 were inadvertently switched during the production and this has been corrected so the figures appear in the proper order.

Combination treatment of Glatiramer Acetate and Minocycline affects phenotype expression of blood monocyte-derived dendritic cells in Multiple Sclerosis patients.

The effects of Glatiramer Acetate (GA) in combination with Minocycline (MIN), a second-generation tetracycline, have been investigated on the course of EAE in mice, resulting in a significant reduction in disease severity and burden with attenuation of the inflammation, axonal loss and demyelination. Here we investigate the effects of combination therapy with GA and MIN on the induction, maturation and phenotyping of blood monocyte-derived dendritic cells (DCs) in Multiple Sclerosis (MS) patients. Hence the expressions of HLA-DR, CD11c, CD83 and CD1a were studied by flow cytometric analysis on immature (iDCs) and mature DCs (mDCs) from untreated and GA treated MS patients. Thirteen relapsing-remitting MS patients and 13 healthy controls (HCs) were included in the study. Ten of the MS patient group were re-tested after a 2 month period of GA treatment. The marker expressions on DC from untreated MS and HCs were studied in vitro in the absence or presence of GA and GA+MIN; and on DCs from GA treated MS patients without and with the in vitro addition of MIN. We found that in vitro GA alone or in combination with MIN downregulated DCs antigen presentation capability (HLA-DR), whereas the combination treatment only affected also myeloid DCs activation (CD83) in both MS and HCs. Prolonged GA treatment (in vivo for 2 months) affected antigen presentation capability by DCs, whereas when treated in vitro with MIN these cells also tended to reduce activation marker expression and myeloid phenotype acquisition (CD11c). The present data demonstrate possible combination effects of GA and MIN on peripheral blood monocyte-derived DCs in MS patients.