IL-6 and Akt are involved in muscular pathogenesis in myasthenia gravis

Small extracellular vesicle microRNAs in pediatric myasthenia gravis plasma and skeletal muscle

BACKGROUND

The diagnosis of myasthenia gravis (MG) in children remains difficult. Circulating small extracellular vesicle (sEV)-derived miRNAs (sEV-miRNAs) have been recognized as biomarkers of various diseases and can be excreted by different cell types. These biomarker candidates also play a vital role in autoimmune diseases via intercellular communication.

METHODS

In the present study, we used sEV isolation and purification methods to extract the plasma-derived sEV-miRNAs from children with MG and healthy controls. A small RNA sequencing analysis confirmed the miRNA expression features in plasma-derived sEVs from MG patients. The miRNA expression analysis in vitro was determined using microarray analysis. The enrichment and network analyses of altered sEV-miRNAs were performed using miRNA databases and Database for Annotation, Visualization, and Integrated Discovery website. Quantitative real-time polymerase chain reaction was performed for validation of sEV-miRNA. The diagnostic power of altered sEV-miRNAs was evaluated using receiver operating characteristic curve analyses.

RESULTS

Twenty-four sEV-miRNAs with altered expression level were identified between groups by DESeq2 method. The miRNAs were extracted from the sEVs, which were isolated from human primary skeletal muscle cell culture treated with mAb198. The target genes and enriched pathways of sEV-miRNAs partially overlapped between cell supernatant and plasma samples. The significantly downregulated miR-143-3p was validated in quantitative real-time polymerase chain reaction analysis.

CONCLUSIONS

For the first time, we report that plasma-derived sEV-miRNAs may act as novel circulating biomarkers and therapeutic targets in pediatric MG.

Anethole via increase in the gene expression of PI3K/AKT/mTOR mitigates the autistic-like behaviors induced by maternal separation stress in mice

Autism spectrum disorder (ASD) is a neurodegenerative disease with increasing incidence in the world. The maternal separation (MS) stress at early life with its own neuroendocrine and neurostructural changes can provide the basis for development of ASD. Previously it has been reported neuroprotective characteristics for anethole. The PI3K/AKT/mTOR signaling pathway has pivotal role in the function of central nervous system (CNS). This study aimed to evaluate the possible effects of anethole on the autistic-like behaviors in the maternally separated (MS) mice focusing on the potential role of the PI3K/AKT/mTOR pathway. Forty male Naval Medical Research Institute (NMRI) mice were assigned to five groups (n = 8) comprising a control group (treated with normal saline) and four groups subjected to MS and treated with normal saline and or anethole at doses of 31.25, 62.5 and 125 mg/kg, respectively. All gents were administrated via intraperitoneal (i.p.) route for 14 constant days. Behavioral tests were conducted, including the three-chamber test, shuttle box and resident-intruder test. The gene expression of the PI3K, AKT and mTOR assessed in the hippocampus by qRT-PCR. Findings indicated that MS is associated with autistic-like behaviors. Anethole increased the sociability and social preference indexes in the three-chamber test, increased duration of secondary latency in the shuttle box test and decreased aggressive behaviors in the resident-intruder test. Also, anethole increased the gene expression of PI3K, AKT and mTOR in the hippocampus of MS mice. We concluded that anethole through increase in the gene expression of PI3K/ AKT/mTOR mitigated autistic-like behaviors induced by MS in mice.

Tertiary structure and conformational dynamics of the anti-amyloidogenic chaperone DNAJB6b at atomistic resolution

DNAJB6b is a molecular chaperone of the heat shock protein network, shown to play a crucial role in preventing aggregation of several disease-related intrinsically disordered proteins. Using homology modeling and microsecond-long all-atom molecular dynamics (MD) simulations, we show that monomeric DNAJB6b is a transiently interconverting protein cycling between three states: a closed state, an open state (both abundant), and a less abundant extended state. Interestingly, the reported regulatory autoinhibitory anchor between helix V in the G/F1 region and helices II/III of the J-domain, which obstructs the access of Hsp70 to the J-domain remains present in all three states. This possibly suggests a mechanistically intriguing regulation in which DNAJB6b only becomes exposed when loaded with substrates that require Hsp70 processing. Our MD results of DNAJB6b carrying mutations in the G/F1 region that are linked to limb-girdle muscular dystrophy type D1 (LGMDD1) show that this G/F1 region becomes highly dynamic, pointing towards a spontaneous release of the autoinhibitory helix V from helices II/III. This would increase the probability of non-functional Hsp70 interactions to DNAJB6b without substrates. Our cellular data indeed confirm that non-substrate loaded LGMDD1 mutants have aberrant interactions with Hsp70.

Responsiveness to Tocilizumab in Anti-Acetylcholine Receptor-Positive Generalized Myasthenia Gravis

Tocilizumab, a humanized IL-6R monoclonal antibody, has been used in autoimmune diseases closely related to humoral immunity. This report aims to evaluate the efficacy and safety in patients with anti-acetylcholine receptor-positive (AChR+) generalized myasthenia gravis (gMG). We performed a prospective, open-label, single-arm study in patients with gMG in a 48-week follow-up. All patients were AChR+ and were given tocilizumab by intravenous infusion at a dose of 8 mg/kg at intervals of 4 weeks. The primary endpoint was mean change from baseline in quantitative MG (QMG) score at week 12. The secondary endpoints were mean changes from baseline in MG activities of daily living (MG-ADL) score, AChR-ab titers, and the dosage of oral prednisone at week 12. At week 48, QMG, MG-ADL, and the use of prednisone were also evaluated. Fourteen gMG patients were enrolled and all of them completed the study. Tocilizumab treatment started 8 (4-192) months after the onset of gMG. During tocilizumab treatment, the QMG score was significantly decreased from 15.5 (interqualile range, 9-26) at baseline to 4 (0-9) at week 12 (p < 0.001). The change of ADL was decreased from 14.5(11-19) at baseline to 4 (0-19) at week 12 (p < 0.001) and the change of AChR-ab titers from 15 (7.5-19) at baseline to 6.8 (11.6-4.3) at week 12 (p < 0.001). The dosage of prednisone decreased from baseline 60 (20-65) mg/d to 30 (30-50) mg/d at week 12 (p < 0.001). By the end of the study, the QMG score was 2 (0-7) and MG-ADL score was 1.5 (0-6). 12 (85.7%) patients achieved minimal manifestations. 4 (28.6%) patients were able to discontinue prednisone. No patients experienced exacerbation at the end of the study. No serious adverse events were observed during follow-up. Tocilizumab treatment was associated with a good clinical response and safety over a 48-week observation period, as evidenced by significant improvements in QMG and MG-ADL.

Paeoniflorin alleviated muscle atrophy in cancer cachexia through inhibiting TLR4/NF-κB signaling and activating AKT/mTOR signaling

Cancer cachexia is a progressive wasting syndrome, which is mainly characterized by systemic inflammatory response, weight loss, muscle atrophy, and fat loss. Paeoniflorin (Pae) is a natural compound extracted from the dried root of Paeonia lactiflora Pallas, which is featured in anti-inflammatory, antioxidant, and immunoregulatory pharmacological activities. While, the effects of Pae on cancer cachexia had not been reported before. In the present study, the effects of Pae on muscle atrophy in cancer cachexia were observed both in vitro and in vivo using C2C12 myotube atrophy cell model and C26 tumor-bearing cancer cachexia mice model. In the in vitro study, Pae could alleviate myotubes atrophy induced by conditioned medium of C26 colon cancer cells or LLC Lewis lung cancer cells by decreasing the expression of Atrogin-1 and inhibited the decrease of MHC and MyoD. In the in vivo study, Pae ameliorated weight loss and improved the decrease in cross-sectional area of muscle fibers and the impairment of muscle function in C26 tumor-bearing mice. The inhibition of TLR4/NF-κB pathway and the activation of AKT/mTOR pathway was observed both in C2C12 myotubes and C26 tumor-bearing mice treated by Pae, which might be the main basis of its ameliorating effects on muscle atrophy. In addition, Pae could inhibit the release of IL-6 from C26 tumor cells, which might also contribute to its ameliorating effects on muscle atrophy. Overall, Pae might be a promising candidate for the therapy of cancer cachexia.

Clinical outcome and peripheral immune profile of myasthenic crisis with omicron infections: A prospective cohort study

The impact of Omicron infections on the clinical outcome and immune responses of myasthenia gravis (MG) remained largely unknown. From a prospective multicenter MG cohort (n = 189) with 197 myasthenic crisis (MC), we finally included 41 independent MG patients to classify into two groups: the Omicron Group (n = 13) and the Control Group (n = 28). In this matched cohort study, all-cause mortality was 7.69% (1/13) in Omicron Group and 14.29% (4/28) in Control Group. A higher proportion of elevated serum IL-6 was identified in the Omicron Group (88.89% vs 52.38%, P = 0.049). In addition, the proportions of CD3+CD8+T in lymphocytes and Tregs in CD3+CD4+ T cells were significantly elevated in the Omicron Group (both P = 0.0101). After treatment, the Omicron Group exhibited a marked improvement in MG-ADL score (P = 0.026) and MG-QoL-15 (P = 0.0357). MCs with Omicron infections were associated with elevated serum IL-6 and CD3+CD8+T response. These patients tended to present a better therapeutic response after fast-acting therapies and anti-IL-6 treatment.

Dexamethasone improves thymoma-associated myasthenia gravis via the AKT-mTOR pathway

Clinically, thymoma patients are often complicated with myasthenia gravis (MG). Dexamethasone, a glucocorticoid with anti-inflammatory effects, could be used as an immunosuppressant for thymoma-associated MG, but the mechanism of action remains to be explored. In this study, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, weighted gene co-expression network analysis (WGCNA) of potential targets was performed by screening the intersection targets of dexamethasone and thymoma-associated MG from the database. Furthermore, the key targets and core active components were identified by topological analysis of the protein-protein interaction (PPI) network. Molecular docking technology was applied to screen the complexes with stable binding of dexamethasone and core targets. Patients with thymoma were divided into two groups according to whether they received dexamethasone before operation, and immunohistochemistry and western blot were used to verify the selected target of dexamethasone in treating thymoma-associated MG. The results showed that the action pathway of dexamethasone on the disease was closely enriched to phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB/AKT), mammalian target of rapamycin (mTOR) signaling pathways. The expressions of AKT1 and its downstream molecule mTOR in the thymoma microenvironment of thymoma-associated MG patients who did not receive dexamethasone before operation were higher than those in the group receiving dexamethasone before operation. This study demonstrates that dexamethasone can promote apoptosis through the AKT-mTOR pathway for the treatment of thymoma-associated MG, as validated by network pharmacology predictions and clinical specimen experiments, and can be verified by large-scale clinical trials in the future. This study also provides theoretical support and new research perspectives for this disease.

Altered serum levels of cytokines in patients with myasthenia gravis

Background

Myasthenia gravis (MG) is an autoimmune disease characterized by generalized skeletal muscle contraction weakness due to autoantibodies targeting neural-muscular junctions. Here, we investigated the relationship between key cytokines and MG type, disease course, antibodies, and comorbidities.

Method

Cytokine levels in serum samples collected from MG (n = 45) and healthy control (HC, n = 38) patients from January 2020 to June 2022 were quantified via flow cytometry.

Results

Levels of IL-6 were higher in the MG group versus healthy individuals (p = 0.026) and in patients with generalized versus ocular MG (p = 0.019). IL-6 levels were positively correlated with QMG score. In patients with MG with both AChR and Titin antibodies, serum levels of sFas and granulysin were higher than in those with AChR alone (p = 0.036, and p = 0.028, respectively). LOMG had a reduction in serum levels of IL-2 compared to EOMG (p = 0.036). LOMG patients with diabetes had lower serum levels of IL-2, IL-4, and IFN-γ (p = 0.044, p = 0.038, and p = 0.047, respectively) versus those without diabetes. sFas in the MG with Abnormal thymus were reduced compared to those in MG with Normal thymus (p = 0.008).

Conclusions

This study revealed a positive correlation between IL-6 level and MG status. Serum cytokine levels of the AChR + Titin MG group differed from those of the AChR group. LOMG had a lower IL-2 level. Comorbidities affect some cytokines in peripheral blood in MG serum.

A glance through the effects of CD4+ T cells, CD8+ T cells, and cytokines on Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. Unfortunately, despite numerous studies, an effective treatment for AD has not yet been established. There is remarkable evidence indicating that the innate immune mechanism and adaptive immune response play significant roles in the pathogenesis of AD. Several studies have reported changes in CD8+ and CD4+ T cells in AD patients. This mini-review article discusses the potential contribution of CD4+ and CD8+ T cells reactivity to amyloid β (Aβ) protein in individuals with AD. Moreover, this mini-review examines the potential associations between T cells, heme oxygenase (HO), and impaired mitochondria in the context of AD. While current mathematical models of AD have not extensively addressed the inclusion of CD4+ and CD8+ T cells, there exist models that can be extended to consider AD as an autoimmune disease involving these T cell types. Additionally, the mini-review covers recent research that has investigated the utilization of machine learning models, considering the impact of CD4+ and CD8+ T cells.

Plasma Myokine Profiles in Patients With AChR- and MuSK-Ab-Positive Myasthenia Gravis

BACKGROUND AND PURPOSE

Myokines include cytokines secreted by muscle fibers, which are the final targets of myasthenia gravis (MG). This pilot study investigated whether myokine plasma concentrations are altered in patients with MG and assessed the association between the concentration of each myokine and disease severity.

METHODS

We compared the plasma concentrations of 15 myokines in 63 patients with acetylcholine receptor antibody (Ab)-positive MG and 14 with muscle-specific tyrosine kinase Ab-positive MG (MuSK MG) with those in 15 healthy controls. Plasma myokine concentrations were measured using a Luminex multiplex assay kit with magnetic beads that contained Abs for 15 myokines. Correlations between myokine concentration and clinical scale results were analyzed.

RESULTS

The concentration of fractalkine in plasma was higher in MG (median [interquartile range]=419.6 [38.7-732.5] pg/mL) than in controls (158.5 [0.0-313.2] pg/mL, p=0.034). The leukemia inhibitory factor concentration was also found to be higher in MuSK MG (29.9 [8.7-40.1] pg/mL) than in healthy controls (7.6 [0.0-15.6] pg/mL, p=0.013). Fatty-acid-binding protein 3 (FABP3) concentrations in plasma were positively associated with clinical parameters for MG severity, including scores on the Quantitative Myasthenia Gravis score (p=0.008), Myasthenia Gravis Activities of Daily Living (p=0.003), and Myasthenia Gravis Composite (p=0.024) scales. FABP3 concentration in plasma tended to decrease after treatment in patients without additional relapse but increased in those with further relapse.

CONCLUSIONS

The plasma myokine profile was significantly altered in patients with MG. FABP3 concentration may be useful in assessing disease severity and predicting the treatment response.

Nomogram for the acute exacerbation of acetylcholine receptor antibody-positive generalized myasthenia gravis

BACKGROUND AND OBJECTIVE

An acute exacerbation of myasthenia gravis (MG) can lead to the life-threatening myasthenia crisis which can increase the in-hospital mortality. This study aimed to clarify the correlative factor of the severity and activity of MG and the predictors of its exacerbation.

METHODS

A prospective study was conducted to compare the clinical characteristics of acetylcholine receptor antibody (AChR-Ab)-positive generalized MG during acute exacerbation (AE) and in a stable state (SS). Logistic regression was used to determine risk factors, and a nomogram was developed.

RESULTS

A total of 97 AChR-Ab MG patients were enrolled, of whom 44 had AE and 53 were in SS. The concentrations of AChR-Ab were 35.24 (23.26, 42.52) nmol/L and 19.51 (8.30, 36.93) nmol/L in the AE and SS groups (P = 0.005), respectively. The receiver operating characteristic curve showed that a single AChR-Ab predicted severity and acute exacerbation, with an area under the curve (AUC) of 0.679. Logistic regression analysis showed that, in addition to AChR-Ab (P = 0.018), bulbar symptoms (P = 0.001), interleukin (IL)-6 (P = 0.025), CD4⁺/CD8⁺ T cell ratio (P = 0.031), and CD19⁺ B cell proportion (P = 0.019) were independent risk factors for acute exacerbation of MG. The developed nomogram had an AUC of 0.878. The Hosmer and Lemeshow chi-square test was 4.37 (P = 0.929).

CONCLUSION

AChR-Ab concentration was positively correlated with the severity and activity of MG. AChR-Ab concentration, alongside bulbar symptoms, IL-6 concentration, CD4⁺/CD8⁺ T cell ratio, and CD19⁺ B cell proportion can predict the acute exacerbation of MG.

Investigation of the Underlying Mechanism of Huangqi-Dangshen for Myasthenia Gravis Treatment via Molecular Docking and Network Pharmacology

The herbal pairing of Huangqi and Dangshen (HD) is traditional Chinese herbal medicine and has been widely used in China, especially to treat myasthenia gravis (MG). However, the mechanism of HD on MG is unclear. Aim of the Study. This study aims to investigate HD's possible role in MG treatment. Materials and Methods. The TCMSP database was used to identify the active chemicals and their targets. The GeneCards, DisGeNET, and OMIM databases were used to search for MG-related targets. The STRING database was employed in order to identify the common PPI network targets. We next utilised Cytoscape 3.8.2 for target identification and the DAVID database for gene ontology (GO) function analysis as well as Encyclopaedia of Genomes (KEGG) pathway enrichment analysis on the selected targets. The AutoDock Vina software was used to test the affinity of essential components with the hub gene before concluding that the primary targets were corrected through molecular docking. Results. 41 active compounds were screened from HD, and the number of putative-identified target genes screened from HD was 112. There were 21 target genes that overlapped with the targets of MG, which were postulated to be potential treatment targets. Through further analysis, the results showed that the active compounds from HD (such as 7-methoxy-2-methylisoflavone, quercetin, luteolin, Kaempferol, and isorhamnetin) may achieve the purpose of treating MG by acting on some core targets and related pathways (such as EGFR, FOS, ESR2, MYC, ESR1, CASP3, and IL-6). Molecular docking findings demonstrated that these active molecules have a near-perfect ability to attach to the primary targets. Conclusion. Through network pharmacology, the findings in this study provide light on the coordinated action of several HD formula components, targets, and pathways. It provided a theoretical basis for further study of HD pharmacological action.

Exploring the Potential Mechanism of Qi-Shen-Di-Huang Drug Formulary for Myasthenia Gravis (MG) based on UHPLC-QE-MS Network Pharmacology and Molecular Docking Techniques

Myasthenia gravis (MG) is a rare and refractory autoimmune disease, and Qi Shen Di Huang (QSDH) drug formulary is an in-hospital herbal decoction with proven clinical efficacy in treating MG. Currently, most of the research on the QSDH drug formulary has concentrated on its clinical efficacy, and there is a lack of systematic study on the material basis. The active compounds and their mechanism of action have not been entirely determined. Therefore, this study sought to identify the active compounds in the QSDH drug formulary and analyze the key targets and potential mechanisms. We used ultra-performance liquid chromatography Q Exactive-mass spectrometry (UHPLC-QE-MS) and Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) database to identify and screen 85 active ingredients corresponding to 59 potential targets (17 herbs) associated with myasthenia gravis, and further identified AKT1 as the primary core target and the PI3K/AKT signaling pathway as the most substantial enriched pathway. Molecular docking and UPLC-MS analysis identified quercetin, luteolin, wogonin, kaempferol, laccasein, and epigallocatechin gallate are the core compounds of the QSDH drug formulary. In vivo rat studies showed that the QSDH drug formulary reduced Lennon's clinical score and decreased acetylcholine receptor antibody levels in peripheral blood rats with experimental autoimmune myasthenia gravis. In addition, the QSDH drug formulary downregulated P-PI3K/PI3K and P-Akt/Akt protein expression. Collectively, these findings describe the role and potential mechanism of the QSDH drug formulary in the treatment of MG, which exerts potential value by acting on AKT targets and regulating the PI3K/AKT signaling pathway and providing a theoretical reference for QSDH drug formulary application in the clinical treatment of MG.

Study on the Potential Mechanism of Semen Strychni against Myasthenia Gravis Based on Network Pharmacology and Molecular Docking with Experimental Verification

Background

Semen Strychni (SS) is an effective Chinese medicine formula for treating myasthenia gravis (MG) in clinics. Nonetheless, its molecular mechanism is largely unknown.

Objective

Using network pharmacology, molecular docking, and experimental validation, we aim to identify the therapeutic effect of SS on MG and its underlying mechanism.

Methods

The main ingredients of SS and their targets and potential disease targets for MG were extracted from public databases. The protein-protein interaction (PPI) network was constructed using the STRING 11.0 database, and Cytoscape was used to identify the hub targets. In addition, Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to identify molecular biological processes and signaling pathways. Then, AutoDock Via conducted molecular docking. The experimental autoimmune myasthenia gravis (EAMG) model in female Lewis rats, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and enzyme-linked immunosorbent assay (ELISA) were performed to confirm the effect and mechanism of SS on MG.

Results

The following active compounds and hub targets were identified by screening and analyzing: isobrucine, vomicine, (S)-stylopine, strychnine, brucine-N-oxide, brucine and AKT1, MAPK1, MAPK14, CHRM1, ACHE, and CHRNA4. KEGG enrichment analyses indicated that the cholinergic synapse and neuroactive ligand-receptor interaction signaling pathway may be necessary. The results of molecular docking revealed that the main active ingredients bind well to the hub targets. In vivo experiments proved that SS could improve the weight loss and Lennon scores in the EAMG model. Experiments in molecular biology showed that SS could treat MG by affecting the cholinergic synapse through the respective antibody, receptor, and key enzymes in the cholinergic pathway.

Conclusion

This study provided a preliminary overview of the active constituents, primary targets, and potential pathways of SS against MG. SS ameliorated EAMG by regulating the cholinergic synaptic junction.

Expression of TRAF6 in peripheral blood B cells of patients with myasthenia gravis

Background

Tumor necrosis factor receptor-associated factor 6 (TRAF6) can regulate the activation of inflammatory signaling pathways by acting as an E3 ubiquitin ligase, which enhances B cell activation. This study aimed to evaluate the expression of TRAF6 in the peripheral blood B cells of myasthenia gravis (MG) patients and analyze the relationships between TRAF6 expression and clinical characteristics.

Method

In our study, the expression level of TRAF6 in peripheral blood B cells of 89 patients was measured by flow cytometry compared with that of healthy subjects. The effects of disease severity, MG classification and immunotherapy on TRAF6 expression level were also analyzed.

Results

In our study, TRAF6 expression was elevated in CD19⁺ B cells and CD19⁺CD27⁺ memory B cells in generalized MG (GMG) patients compared with ocular MG (OMG) patients (p = 0.03 and p = 0.03, respectively). There was a significant positive correlation between the TRAF6 expression level and disease severity in both OMG patients and GMG patients (CD19⁺ B cells: OMG: p < 0.001, r = 0.89; GMG: p = 0.001, r = 0.59; CD29⁺CD27⁺ B cells: OMG: p = 0.001, r = 0.80; GMG: p = 0.048, r = 0.38). TRAF6 expression was significantly elevated in CD19⁺ B cells and CD19⁺CD27⁺ memory B cells in GMG with acute aggravation compared with GMG in MMS (p = 0.009 and p = 0.028, respectively). In the eleven MG patients who were followed, TRAF6 expression in B cells and memory B cells was significantly decreased after treatment (p = 0.03 and p < 0.01, respectively).

Conclusion

TRAF6 is potentially a useful biomarker of inflammation in patients with MG, and might be used to evaluate the effectiveness of treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02833-9.

Histone Deacetylase Isoforms Differentially Modulate Inflammatory and Autoantibody Responses in a Mouse Model of Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disease characterized by chronic muscle fatigue and weakness caused by autoantibodies and complement-mediated damage at neuromuscular junctions. Histone deacetylases (HDACs) are crucial epigenetic regulators of proinflammatory gene expression; however, it is unclear whether HDACs modulate chronic inflammation or autoantibody production associated with MG pathogenesis. We examined expression profiles and serum levels of key inflammatory cytokines (IL-6 and IL-21) and acetylcholine receptor (AChR)-specific autoantibodies following pharmacological inhibition of key HDAC isoforms in a mouse model of MG. We found that HDAC inhibition significantly reduced the production of IL-6, but not IL-21, in AChR-stimulated PBMCs and splenocytes (n = 5 per group). Trichostatin (pan-HDAC inhibitor) treatment of MG-PBMCs (n = 2) also exhibited reduced production of induced IL-6. Although HDAC1 inhibition lowered IL-6 levels the most, HDAC2 inhibition depleted intracellular IL-6 and markedly reduced serum anti-AChR IgG2b in EAMG mice. The transcriptomic profiling and pathway mapping also revealed that autoimmunity-linked, major cell signaling pathways were differentially altered by HDAC1/2 inhibition. HDAC inhibition-mediated reduction in IL-6 and autoantibody levels also correlated with milder disease and preservation of muscle AChR in the treated mice. Overall, our findings revealed isoform-specific functional variance of HDACs in reducing inflammation and identified HDAC-regulated many genes underlying specific inflammatory and autoantibody pathways in EAMG. Thus, the study provides a rationale for further research to evaluate the HDACs or their gene targets as a potential adjunct treatment for MG.

Neuromuscular Development and Disease: Learning From in vitro and in vivo Models

The neuromuscular junction (NMJ) is a specialized cholinergic synaptic interface between a motor neuron and a skeletal muscle fiber that translates presynaptic electrical impulses into motor function. NMJ formation and maintenance require tightly regulated signaling and cellular communication among motor neurons, myogenic cells, and Schwann cells. Neuromuscular diseases (NMDs) can result in loss of NMJ function and motor input leading to paralysis or even death. Although small animal models have been instrumental in advancing our understanding of the NMJ structure and function, the complexities of studying this multi-tissue system in vivo and poor clinical outcomes of candidate therapies developed in small animal models has driven the need for in vitro models of functional human NMJ to complement animal studies. In this review, we discuss prevailing models of NMDs and highlight the current progress and ongoing challenges in developing human iPSC-derived (hiPSC) 3D cell culture models of functional NMJs. We first review in vivo development of motor neurons, skeletal muscle, Schwann cells, and the NMJ alongside current methods for directing the differentiation of relevant cell types from hiPSCs. We further compare the efficacy of modeling NMDs in animals and human cell culture systems in the context of five NMDs: amyotrophic lateral sclerosis, myasthenia gravis, Duchenne muscular dystrophy, myotonic dystrophy, and Pompe disease. Finally, we discuss further work necessary for hiPSC-derived NMJ models to function as effective personalized NMD platforms.

High levels of serum interleukin-6 are associated with disease activity in myasthenia gravis

Myasthenia gravis (MG), a neuromuscular junction disorder, is caused by pathogenic autoantibodies. Interleukin-6 (IL-6) plays important roles in T helper 17 (Th17), T follicular helper (Tfh), and B cell activations as well as in antibody production. This study aimed to evaluate the clinical significance of serum IL-6 level as a biomarker of disease activity in patients with anti-acetylcholine receptor (AChR) antibody-positive MG. In the present study, serum IL-6 levels were measured in 93 treatment-naïve patients with anti-AChR antibody-positive MG and compared with those in 101 controls. Moreover, correlations between serum IL-6 levels and clinical characteristics were analyzed. Serum IL-6 levels were significantly higher in patients with anti-AChR antibody-positive MG than in controls (median [interquartile range], 2.5 [1.5-8.3] pg/mL vs. 1.5 [1.5-3.2] pg/mL, P < 0.001). The serum levels were correlated with the MG Foundation of America clinical classification (Spearman's ρ = 0.27; P < 0.01) and decreased following immunosuppressive treatment in parallel with disease activity (P = 0.01). In conclusion, IL-6 is involved in the pathogenesis of anti-AChR antibody-positive MG and could be a therapeutic target in MG.

Risk of subsequent atrial fibrillation in patients with myasthenia gravis: A population-based cohort study

The purpose of this study was to explore the association between myasthenia gravis (MG) and the risk of atrial fibrillation (AF) in an Asian population. The risk was analyzed in a cohort of 5528 patients with history of MG and 5528 individuals without MG using a hospitalization claim dataset. Both groups were matched by age, sex, index year and baseline comorbidities as an original analysis. A Cox proportional hazard model was used to estimate the hazard ratio and 95% confidence interval of AF after adjusting for demographic and relevant clinical covariates. The adjusted hazard ratio of the MG group compared with that of the non-MG group was 1.03 (95% confidence interval, 0.76-1.38) for AF. A stratified analysis showed that compared with the propensity score matched non-MG group, there was no increased risk of developing AF based on age categories, gender, or comorbidities. Different time follow-up periods results showed no increased risk of AF compared with the non-MG group. Overall, in the Taiwanese cohort, MG is not associated with an increased risk of AF.

Gene expression profiling of orbital muscles in treatment-resistant ophthalmoplegic myasthenia gravis

Background

Unbiased in silico approaches applied to genome-wide data prioritized putative functional gene variants associating with treatment-resistant ophthalmoplegic myasthenia gravis (OP-MG). Although altered expression of genes harbouring these variants, or associated pathways, were shown in patient-derived transdifferentiated-myocyte models, gene expression in orbital-derived muscle was required to test the validity of the predictions.

Methods

We sampled orbicularis oculi muscle (OOM) and one paralysed extraocular muscle (EOM) from six individuals with OP-MG during blepharoptosis and re-alignment surgeries, respectively. For controls, the OOMs were sampled from four individuals without myasthenia undergoing surgery for non-muscle causes of ptosis, and one non-paralysed EOM. Using a qPCR array, expression of 120 genes was compared between OP-MG and control OOMs, profiling putative “OP-MG” genes, genes in related biological pathways and genes reported to be dysregulated in MG cases or experimental MG models, and in EOMs of cases with strabismus. Normalization was performed with two stable reference genes. Differential gene expression was compared between OP-MG and control samples using the ΔΔCT method. Co-expression was analysed by pairwise correlation of gene transcripts to infer expression networks.

Results

Overall, transcript levels were similar in OOMs and EOMs (p = 0.72). In OOMs, significant downregulated expression of eight genes was observed in OP-MG cases compared with controls (> twofold; p ≤ 0.016), including TFAM, a mitochondrial transcription factor, and genes related to the following pathways: atrophy signalling; muscle regeneration and contraction; glycogen synthesis; and extracellular matrix remodelling. Several microRNAs, known to be highly expressed in EOMs, are predicted to regulate some of these genes. Co-expression analyses of gene-pairs suggested high interconnectedness of gene expression networks in OP-MG muscle, but not controls (r > 0.96, p < 0.01). Significant inverse directions of gene-pair correlations were noted in OP-MG versus controls OOM networks (r ≥ 0.92, p < 0.001) involving most OP-MG genes overlapping prominently with muscle atrophy/contractility and oxidative metabolism genes.

Conclusions

The gene expression in orbital muscles derived from OP-MG individuals compared with normal controls, support the pathogenic hypothesis previously generated from whole genome sequence analyses. Repression of gene transcripts in OP-MG orbital muscle implicate tissue-specific regulatory mechanisms, which may inform future biomarker discovery approaches.

Changes in serum complements and their regulators in generalized myasthenia gravis

OBJECTIVE

To investigate changes in serum complements and their regulators in the pathogenesis of myasthenia gravis (MG).

METHODS

Forty-four patients with acetylcholine receptor antibody-positive MG, as well as 20 patients with non-inflammatory neurological disorders were enrolled. Serum complements (C3, C4 and soluble C5b-9) and complement regulators (vitronectin, clusterin and properdin) were extensively analysed by enzyme-linked immunosorbent assay and their associations with clinical profiles of MG were examined.

RESULTS

Serum C3, C4 and clusterin levels were not significantly different between patients with MG and controls. The patients with MG had higher soluble C5b-9 (P = 0.09) and vitronectin (P = 0.001) levels than the controls; moreover, vitronectin levels decreased after treatment (P = 0.09). Serum properdin (P = 0.03) levels were lower in the patients with MG than in the controls, and negatively correlated with the MG Activities of Daily Living score (rs = -0.26, P = 0.09) and with the presence of bulbar palsy (P = 0.04).

CONCLUSION

Our results show that activation of complements and an altered complement network could contribute to the inflammatory pathogenesis of MG.

IL-1β and TNF-α Modulation of Proliferated and Committed Myoblasts: IL-6 and COX-2-Derived Prostaglandins as Key Actors in the Mechanisms Involved

In this study, we investigated the effects and mechanisms of the pro-inflammatory cytokines IL-1β and TNF-α on the proliferation and commitment phases of myoblast differentiation. C2C12 mouse myoblast cells were cultured to reach a proliferated or committed status and were incubated with these cytokines for the evaluation of cell proliferation, cyclooxygenase 2 (COX-2) expression, release of prostaglandins (PGs) and myokines, and activation of myogenic regulatory factors (MRFs). We found that inhibition of the IL-6 receptor reduced IL-1β- and TNF-α-induced cell proliferation, and that the IL-1β effect also involved COX-2-derived PGs. Both cytokines modulated the release of the myokines myostatin, irisin, osteonectin, and IL-15. TNF-α and IL-6 reduced the activity of Pax7 in proliferated cells and reduced MyoD and myogenin activity at both proliferative and commitment stages. Otherwise, IL-1β increased myogenin activity only in committed cells. Our data reveal a key role of IL-6 and COX-2-derived PGs in IL-1β and TNF-α-induced myoblast proliferation and support the link between TNF-α and IL-6 and the activation of MRFs. We concluded that IL-1β and TNF-α induce similar effects at the initial stages of muscle regeneration but found critical differences between their effects with the progression of the process, bringing new insights into inflammatory signalling in skeletal muscle regeneration.

Mitochondrial DNA enhance innate immune responses in neuromyelitis optica by monocyte recruitment and activation

Although recent studies indicate the involvement of monocytes in accelerating the lesion formation of neuromyelitis optica spectrum disorder (NMOSD), the precise mechanism of the innate immune system activation remains elusive. Thus, in this study, we aimed to clarify the mechanisms of NMOSD pathogenesis from the viewpoint of innate immunity activation. We established anti-AQP4 recombinant autoantibodies (Ab) from plasmablasts in NMOSD patient's CSF. Human astrocytes treated with anti-AQP4 Ab produced a significant amount of CCL2 and contributed to the efficient recruitment of monocytes. Moreover, mitochondrial DNA (mtDNA), which activated monocytes via Toll-like receptor 9 (TLR9), was released from astrocytes treated with anti-AQP4 Ab. MtDNA further enhanced CCL2 production by monocytes, and it was demonstrated that mtDNA concentration correlated with the efficiency of monocyte recruitment in the CSF of NMOSD patients. In conclusion, these observations highlight that mtDNA which was released from astrocytes damaged by anti-AQP4 Ab has a central role in establishing the inflammatory loop of monocyte recruitment and activation via an innate immunity pathway.

AChR antibodies show a complex interaction with human skeletal muscle cells in a transcriptomic study

Acetylcholine receptor (AChR) antibodies are the most important pathogenic marker in patients with myasthenia gravis (MG). The antibodies bind to AChRs on the postsynaptic membrane, and this leads to receptor degradation, destruction, or functional blocking with impaired signal at the neuromuscular junction. In this study, we have explored the effects of AChR antibodies binding to mature human myotubes with agrin-induced AChR clusters and pathways relevant for AChR degradation using bulk RNA sequencing. Protein-coding RNAs and lncRNAs were examined by RNA sequencing analysis. AChR antibodies induced marked changes of the transcriptomic profiles, with over 400 genes differentially expressed. Cholesterol metabolic processes and extracellular matrix organization gene sets were influenced and represent AChR-trafficking related pathways. Muscle contraction and cellular homeostasis gene sets were also affected, and independently of AChR trafficking. Furthermore, we found changes in a protein-coding RNA and lncRNA network, where expression of lncRNA MEG3 correlated closely with protein-coding genes for cellular homeostasis. We conclude that AChR antibodies induce an active response in human skeletal muscle cells which affects key intra- and extracellular pathways.

The Muscle Is Not a Passive Target in Myasthenia Gravis

Myasthenia gravis (MG) is a rare autoimmune disease mediated by pathogenic antibodies (Ab) directed against components of the neuromuscular junction (NMJ), mainly the acetylcholine receptor (AChR). The etiological mechanisms are not totally elucidated, but they include a combination of genetic predisposition, triggering event(s), and hormonal components. MG disease is associated with defective immune regulation, chronic cell activation, inflammation, and the thymus is frequently abnormal. MG is characterized by muscle fatigability that is very invalidating and can be life-threatening when respiratory muscles are affected. MG is not cured, and symptomatic treatments with acetylcholinesterase inhibitors and immunosuppressors are life-long medications associated with severe side effects (especially glucocorticoids). While the muscle is the ultimate target of the autoimmune attack, its place and role are not thoroughly described, and this mini-review will focus on the cascade of pathophysiologic mechanisms taking place at the NMJ and its consequences on the muscle biology, function, and regeneration in myasthenic patients, at the histological, cellular, and molecular levels. The fine structure of the synaptic cleft is damaged by the Ab binding that is coupled to focal complement-dependent lysis in the case of MG with anti-AChR antibodies. Cellular and molecular reactions taking place in the muscle involve several cell types as well as soluble factors. Finally, the regenerative capacities of the MG muscle tissue may be altered. Altogether, the studies reported in this review demonstrate that the muscle is not a passive target in MG, but interacts dynamically with its environment in several ways, activating mechanisms of compensation that limit the pathogenic mechanisms of the autoantibodies.

Molecular profiling of thymoma with myasthenia gravis: Risk factors of developing myasthenia gravis in thymoma patients

OBJECTIVE

Thymoma is a rare epithelial tumor arising from the thymus in the anterior mediastinum. Nearly 50% of patients with thymoma develop myasthenia gravis, which is an indication of a poor long-term prognosis. Here, we identified specific and effective molecular markers for predicting in the development of myasthenia gravis patients with thymoma.

MATERIAL AND METHODS

We investigated molecular profiling based on RNA-sequencing (RNA-seq) for myasthenia gravis development in patients with thymoma. RNA was extracted from 34 patients with thymoma, 16 of whom had myasthenic and 18 of whom did not, and transcriptome profiles were analyzed through next-generation sequencing.

RESULTS

We discovered 140 differential expressed genes associated with myasthenia gravis in thymoma patients. The four genes, hypoxia-inducible factor 3 alpha (HIF3A), insulin-like growth factor-binding protein 1, pyruvate dehydrogenase kinase, and Krüppel-like factor 15 were differentially expressed in patients with thymoma who has myasthenia gravis and were validated by quantitative polymerase chain reaction. HIF3A expression was significantly higher in patients with myasthenia gravis than in those without.

CONCLUSION

HIF3A is aberrantly expressed in patient with thymoma who has myasthenia gravis and may be involved in the development of myasthenia gravis in thymoma patient.

Molecular and clinical relationship between live-attenuated Japanese encephalitis vaccination and childhood onset myasthenia gravis

Objective

The incidence of childhood onset myasthenia gravis (CMG) in China is higher than that in other countries; however, the reasons for this are unclear.

Methods

We investigated the clinical and immunological profiles of CMG, and assessed the potential precipitating factors. For the mouse studies, the possible implication of vaccination in the pathogenesis was explored.

Results

In our retrospective study, 51.22% of the 4,219 cases of myasthenia gravis (MG) were of the childhood onset type. The cohort study uncovered that the pathophysiology of CMG was mediated by immune deviation, rather than through gene mutations or virus infections. The administration of the live‐attenuated Japanese encephalitis vaccine (LA‐JEV), but not the inactivated vaccine or other vaccines, in mice induced serum acetylcholine receptor (AChR) antibody production, reduced the AChR density at the endplates, and decreased both muscle strength and response to repetitive nerve stimulation. We found a peptide (containing 7 amino acids) of LA‐JEV similar to the AChR‐α subunit, and immunization with a synthesized protein containing this peptide reproduced the MG‐like phenotype in mice.

Interpretation

Our results describe the immunological profile of CMG. Immunization with LA‐JEV induced an autoimmune reaction against the AChR through molecular mimicry. These findings might explain the higher occurrence rate of CMG in China, where children are routinely vaccinated with LA‐JEV, compared with that in countries, where this vaccination is not as common. Efforts should be made to optimize immunization strategies and reduce the risk for developing autoimmune disorders among children. Ann Neurol 2018;84:386–400

A review of the histopathological findings in myasthenia gravis: Clues to the pathogenesis of treatment-resistance in extraocular muscles

In myasthenia gravis autoantibodies target components of the neuromuscular junction causing variable degrees of weakness. In most cases, autoantibodies trigger complement-mediated endplate damage and extraocular muscles may be most susceptible. A proportion of MG cases develop treatment-resistant ophthalmoplegia. We reviewed publications spanning 65 years reporting the histopathological findings in the muscles and extraocular muscles of myasthenic patients to determine whether pathological changes in extraocular muscles differ from non-ocular muscles. As extraocular muscles represent a unique muscle allotype we also compared their histopathology in myasthenia to those in strabismus. We found that in myasthenia gravis, the non-ocular muscles frequently demonstrate neurogenic changes regardless of myasthenic serotype. Mitochondrial stress/damage was also frequent in myasthenic muscles and possibly more evident in muscle-specific kinase antibody-positive MG. Although myasthenia-associated paralysed extraocular muscles demonstrated prominent fibro-fatty replacement and mitochondrial alterations, these features appeared commonly in paralysed extraocular muscles of any cause. We postulate that extraocular muscles may be more susceptible than limb muscles to poor contractility as a consequence of myasthenia, resulting in a cascade of atrophy signaling pathways and altered mitochondrial homeostasis which contribute to the tipping point in developing treatment-resistant myasthenic ophthalmoplegia. Early strategies to improve force generation in extraocular muscles are critical.

Profiling of patient-specific myocytes identifies altered gene expression in the ophthalmoplegic subphenotype of myasthenia gravis

Background

While extraocular muscles are affected early in myasthenia gravis (MG), but respond to treatment, we observe a high incidence of treatment-resistant ophthalmoplegia (OP-MG) among MG subjects with African genetic ancestry. Previously, using whole exome sequencing, we reported potentially functional variants which associated with OP-MG. The aim of this study was to profile the expression of genes harbouring the OP-MG associated variants using patient-derived subphenotype-specific ‘myocyte’ cultures.

Methods

From well-characterised MG patients we developed the ‘myocyte’ culture models by transdifferentiating dermal fibroblasts using an adenovirus expressing MyoD. These myocyte cultures were treated with homologous acetylcholine receptor antibody-positive myasthenic sera to induce muscle transcripts in response to an MG stimulus. Gene expression in myocytes derived from OP-MG (n = 10) and control MG subjects (MG without ophthalmoplegia; n = 6) was quantified using a custom qPCR array profiling 93 potentially relevant genes which included the putative OP-MG susceptibility genes and other previously reported genes of interest in MG and experimental autoimmune myasthenia gravis (EAMG).

Results

OP-MG myocytes compared to control MG myocytes showed altered expression of four OP-MG susceptibility genes (PPP6R2, CANX, FAM136A and FAM69A) as well as several MG and EAMG genes (p < 0.05). A correlation matrix of gene pair expression levels revealed that 15% of gene pairs were strongly correlated in OP-MG samples (r > 0.78, p < 0.01), but not in control MG samples. OP-MG susceptibility genes and MG-associated genes accounted for the top three significantly correlated gene pairs (r ≥ 0.98, p < 1 × 10^− 6) reflecting crosstalk between OP-MG and myasthenia pathways, which was not evident in control MG cells. The genes with altered expression dynamics between the two subphenotypes included those with a known role in gangliosphingolipid biosynthesis, mitochondrial metabolism and the IGF1-signalling pathway.

Conclusion

Using a surrogate cell culture model our findings suggest that muscle gene expression and co-expression differ between OP-MG and control MG individuals. These findings implicate pathways not previously considered in extraocular muscle involvement in myasthenia gravis and will inform future studies.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1003-y) contains supplementary material, which is available to authorized users.

New Pathways and Therapeutic Targets in Autoimmune Myasthenia Gravis

Acquired Myasthenia Gravis (MG) is a neuromuscular disease caused by autoantibodies against components of the neuromuscular junction. It is a prototype organ-specific autoimmune disease with well-defined antigenic targets mainly the nicotinic acetylcholine receptor (AChR). Patients suffer from fluctuating, fatigable muscle weakness that worsens with activity and improves with rest.

Various therapeutic strategies have been used over the years to alleviate MG symptoms. These strategies aim at improving the transmission of the nerve impulse to muscle or at lowering the immune system with steroids or immunosuppressant drugs. Nevertheless, MG remains a chronic disease and symptoms tend to persist in many patients, some being or becoming refractory over time. In this review, based on recent experimental data on MG or based on results from clinical trials for other autoimmune diseases, we explore new potential therapeutic approaches for MG patients, going from non-specific approaches with the use of stem cells with their anti-inflammatory and immunosuppressive properties to targeted therapies using monoclonal antibodies specific for cell-surface antigens or circulating molecules.

Marathons and myasthenia gravis: a case report

Background

The cardinal symptoms of auto-immune myasthenia gravis are fatigue and weakness. Endurance events such as marathon running would seem incompatible with this chronic disease. Many patients stop sport altogether. There is limited literature of patients with auto-immune myasthenia gravis undergoing regular endurance exercise.

Case presentation

We report the case of a 36-year-old female who began long-distance running whilst experiencing initial symptoms of myasthenia gravis. She was diagnosed with auto-immune myasthenia gravis and whilst advised to stop all sport, her way of fighting and living with this chronic and unpredictable disease was to continue running to maintain a healthy body and mind. Despite suffering from ocular, bulbar and localized limb fatigability, she managed to complete multiple marathons and achieve disease stability with cholinesterase inhibitors.

Conclusions

Marathon and half-marathon running lead to distinct changes in mediators of inflammation in an exercise-dose-dependent manner. Despite symptoms of weakness and fatigue in certain muscles in myasthenia gravis, physical exertion remains possible and may not worsen symptoms as demonstrated in this case and recent studies. The immunomodulatory role of exercise could be considered in this case however this hypothesis remains to be confirmed in future studies with quantitative data.

NMO-IgG and AQP4 Peptide Can Induce Aggravation of EAMG and Immune-Mediated Muscle Weakness

Neuromyelitis optica (NMO) and myasthenia gravis (MG) are autoimmune diseases mediated by autoantibodies against either aquaporin 4 (AQP4) or acetylcholine receptor (AChR), respectively. Recently, we and others have reported an increased prevalence of NMO in patients with MG. To verify whether coexisting autoimmune disease may exacerbate experimental autoimmune MG, we tested whether active immunization with AQP4 peptides or passive transfer of NMO-Ig can affect the severity of EAMG. Injection of either AQP4 peptide or NMO-Ig to EAMG or to naive mice caused increased fatigability and aggravation of EAMG symptoms as expressed by augmented muscle weakness (but not paralysis), decremental response to repetitive nerve stimulation, increased neuromuscular jitter, and aberration of immune responses. Thus, our study shows increased disease severity in EAMG mice following immunization with the NMO autoantigen AQP4 or by NMO-Ig, mediated by augmented inflammatory response. This can explain exacerbation or increased susceptibility of patients with one autoimmune disease to develop additional autoimmune syndrome.

Electrophysiological correlates of neurodegeneration in motor and non-motor brain regions in amyotrophic lateral sclerosis-implications for brain-computer interfacing

OBJECTIVE

For patients with amyotrophic lateral sclerosis (ALS) who are suffering from severe communication or motor problems, brain-computer interfaces (BCIs) can improve the quality of life and patient autonomy. However, current BCI systems are not as widely used as their potential and patient demand would let assume. This underutilization is a result of technological as well as user-based limitations but also of the comparatively poor performance of currently existing BCIs in patients with late-stage ALS, particularly in the locked-in state.

APPROACH

Here we review a broad range of electrophysiological studies in ALS patients with the aim to identify electrophysiological correlates of ALS-related neurodegeneration in motor and non-motor brain regions in to better understand potential neurophysiological limitations of current BCI systems for ALS patients. To this end we analyze studies in ALS patients that investigated basic sensory evoked potentials, resting-state and task-based paradigms using electroencephalography or electrocorticography for basic research purposes as well as for brain-computer interfacing. Main results and significance. Our review underscores that, similarly to mounting evidence from neuroimaging and neuropathology, electrophysiological measures too indicate neurodegeneration in non-motor areas in ALS. Furthermore, we identify an unexpected gap of basic and advanced electrophysiological studies in late-stage ALS patients, particularly in the locked-in state. We propose a research strategy on how to fill this gap in order to improve the design and performance of future BCI systems for this patient group.

Muscle satellite cells are functionally impaired in myasthenia gravis: consequences on muscle regeneration

Myasthenia gravis (MG) is a neuromuscular disease caused in most cases by anti-acetyl-choline receptor (AChR) autoantibodies that impair neuromuscular signal transmission and affect skeletal muscle homeostasis. Myogenesis is carried out by muscle stem cells called satellite cells (SCs). However, myogenesis in MG had never been explored. The aim of this study was to characterise the functional properties of myasthenic SCs as well as their abilities in muscle regeneration. SCs were isolated from muscle biopsies of MG patients and age-matched controls. We first showed that the number of Pax7+ SCs was increased in muscle sections from MG and its experimental autoimmune myasthenia gravis (EAMG) mouse model. Myoblasts isolated from MG muscles proliferate and differentiate more actively than myoblasts from control muscles. MyoD and MyoG were expressed at a higher level in MG myoblasts as well as in MG muscle biopsies compared to controls. We found that treatment of control myoblasts with MG sera or monoclonal anti-AChR antibodies increased the differentiation and MyoG mRNA expression compared to control sera. To investigate the functional ability of SCs from MG muscle to regenerate, we induced muscle regeneration using acute cardiotoxin injury in the EAMG mouse model. We observed a delay in maturation evidenced by a decrease in fibre size and MyoG mRNA expression as well as an increase in fibre number and embryonic myosin heavy-chain mRNA expression. These findings demonstrate for the first time the altered function of SCs from MG compared to control muscles. These alterations could be due to the anti-AChR antibodies via the modulation of myogenic markers resulting in muscle regeneration impairment. In conclusion, the autoimmune attack in MG appears to have unsuspected pathogenic effects on SCs and muscle regeneration, with potential consequences on myogenic signalling pathways, and subsequently on clinical outcome, especially in the case of muscle stress.

Exome sequencing identifies targets in the treatment-resistant ophthalmoplegic subphenotype of myasthenia gravis

Treatment-resistant ophthalmoplegia (OP-MG) is not uncommon in individuals with African genetic ancestry and myasthenia gravis (MG). To identify OP-MG susceptibility genes, extended whole exome sequencing was performed using extreme phenotype sampling (11 OP-MG vs 4 control-MG) all with acetylcholine receptor-antibody positive MG. This approach identified 356 variants that were twice as frequent in OP-MG compared to control-MG individuals. After performing probability test estimates and filtering variants according to those 'suggestive' of association with OP-MG (p < 0.05), only three variants remained which were expressed in extraocular muscles. Validation in 25 OP-MG and 50 control-MG cases supported the association of DDX17_delG (p = 0.014) and SPTLC3_insACAC (p = 0.055) with OP-MG, but ST8SIA1_delCCC could not be verified by Sanger sequencing. A parallel approach, using a semantic model informed by current knowledge of MG-pathways, identified an African-specific interleukin-6 receptor (IL6R) variant, IL6R c.*3043 T>C, that was more frequent in OP-MG compared to control-MG cases (p = 0.069) and population controls (p = 0.043). A weighted genetic risk score, derived from the odds ratios of association of these variants with OP-MG, correlated with the OP-MG phenotype as opposed to control MG. This unbiased approach implicates several potentially functional gene variants in the gangliosphingolipid and myogenesis pathways in the development of the OP-MG subphenotype.

Autoimmune Thyroiditis and Myasthenia Gravis

Autoimmune diseases (AIDs) are the result of specific immune responses directed against structures of the self. In normal conditions, the molecules recognized as "self" are tolerated by immune system, but when the self-tolerance is lost, the immune system could react against molecules from the body, causing the loss of self-tolerance, and subsequently the onset of AID that differs for organ target and etiology. Autoimmune thyroid disease (ATD) is caused by the development of autoimmunity against thyroid antigens and comprises Hashimoto's thyroiditis and Graves disease. They are frequently associated with other organ or non-organ specific AIDs, such as myasthenia gravis (MG). In fact, ATD seems to be the most associated pathology to MG. The etiology of both diseases is multifactorial and it is due to genetic and environmental factors, and each of them has specific characteristics. The two pathologies show many commonalities, such as the organ-specificity with a clear pathogenic effect of antibodies, the pathological mechanisms, such as deregulation of the immune system and the implication of the genetic predisposition. They also show some differences, such as the mode of action of the antibodies and therapies. In this review that focuses on ATD and MG, the common features and the differences between the two diseases are discussed.

Skeletal muscle characteristics are preserved in hTERT/cdk4 human myogenic cell lines

Background

hTERT/cdk4 immortalized myogenic human cell lines represent an important tool for skeletal muscle research, being used as therapeutically pertinent models of various neuromuscular disorders and in numerous fundamental studies of muscle cell function. However, the cell cycle is linked to other cellular processes such as integrin regulation, the PI3K/Akt pathway, and microtubule stability, raising the question as to whether genetic modification related to the cell cycle results in secondary effects that could undermine the validity of these cell models.

Results

Here we subjected five healthy and disease muscle cell isolates to transcriptomic analysis, comparing immortalized lines with their parent primary populations in both differentiated and undifferentiated states, and testing their myogenic character by comparison with non-myogenic (CD56-negative) cells. Principal component analysis of global gene expression showed tight clustering of immortalized myoblasts to their parent primary populations, with clean separation from the non-myogenic reference. Comparison was made to publicly available transcriptomic data from studies of muscle human pathology, cell, and animal models, including to derive a consensus set of genes previously shown to have altered regulation during myoblast differentiation. Hierarchical clustering of samples based on gene expression of this consensus set showed that immortalized lines retained the myogenic expression patterns of their parent primary populations. Of 2784 canonical pathways and gene ontology terms tested by gene set enrichment analysis, none were significantly enriched in immortalized compared to primary cell populations. We observed, at the whole transcriptome level, a strong signature of cell cycle shutdown associated with senescence in one primary myoblast population, whereas its immortalized clone was protected.

Conclusions

Immortalization had no observed effect on the myogenic cascade or on any other cellular processes, and it was protective against the systems level effects of senescence that are observed at higher division counts of primary cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13395-016-0115-5) contains supplementary material, which is available to authorized users.

Isocitrate dehydrogenase mutations in gliomas

Over the last decade, extraordinary progress has been made in elucidating the underlying genetic causes of gliomas. In 2008, our understanding of glioma genetics was revolutionized when mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) were identified in the vast majority of progressive gliomas and secondary glioblastomas (GBMs). IDH enzymes normally catalyze the decarboxylation of isocitrate to generate α-ketoglutarate (αKG), but recurrent mutations at Arg(132) of IDH1 and Arg(172) of IDH2 confer a neomorphic enzyme activity that catalyzes reduction of αKG into the putative oncometabolite D-2-hydroxyglutate (D2HG). D2HG inhibits αKG-dependent dioxygenases and is thought to create a cellular state permissive to malignant transformation by altering cellular epigenetics and blocking normal differentiation processes. Herein, we discuss the relevant literature on mechanistic studies of IDH1/2 mutations in gliomas, and we review the potential impact of IDH1/2 mutations on molecular classification and glioma therapy.