Survivin as potential mediator to support autoreactive cell survival in myasthenia gravis: A human and animal model study

The mechanisms that underlie the development and maintenance of autoimmunity in myasthenia gravis are poorly understood. In this investigation, we evaluate the role of survivin, a member of the inhibitor of apoptosis protein family, in humans and in two animal models. We identified survivin expression in cells with B lymphocyte and plasma cells markers, and in the thymuses of patients with myasthenia gravis. A portion of survivin-expressing cells specifically bound a peptide derived from the alpha subunit of acetylcholine receptor indicating that they recognize the peptide. Thymuses of patients with myasthenia gravis had large numbers of survivin-positive cells with fewer cells in the thymuses of corticosteroid-treated patients. Application of a survivin vaccination strategy in mouse and rat models of myasthenia gravis demonstrated improved motor assessment, a reduction in acetylcholine receptor specific autoantibodies, and a retention of acetylcholine receptor at the neuromuscular junction, associated with marked reduction of survivin-expressing circulating CD20+ cells. These data strongly suggest that survivin expression in cells with lymphocyte and plasma cell markers occurs in patients with myasthenia gravis and in two animal models of myasthenia gravis. Survivin expression may be part of a mechanism that inhibits the apoptosis of autoreactive B cells in myasthenia gravis and other autoimmune disorders

Micro-RNA and mRNA Profiles Associated with Ectopic Germinal Center Formation in Thymus Samples of Patients with Autoimmune Myas

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder caused by antibodies directed against proteins present at the post-synaptic surface of neuromuscular junction (NMJ). A characteristic pathology of patients with early onset MG is thymic hyperplasia with ectopic germinal centers (GC). However, mechanisms that trigger and maintain thymic hyperplasia are poorly characterized. Micro-RNAs (miRNA) are small, non-coding RNAs that are increasingly appreciated to be involved in the pathology of several autoimmune diseases. In order to determine the central mechanisms involved in the pathology, thymus samples from MG patients were assessed by histology and grouped based on appearance of GC compared to samples without them. MiRNA and mRNA were evaluated using GeneChip® miRNA 4.0 Array and GeneChip® Human Transcriptome Array 2.0, respectively. Partek Genomic Suite 6.6 and Transcript Analysis Console 2.0 programs were used for further analysis. Thirty-four mature miRNA and forty eight annotated mRNA transcripts were identified that were differentially expressed between the two groups with greater than 1.5 fold difference in expression (ANOVA p Our study shows that there is a distinct mRNA and miRNA expression pattern in the thymus and maintenance of autoimmunity is supported by regulatory pathways known to be involved in neoplasia

RNA expression analysis of passive transfer myasthenia support extraocular muscle as a unique immunological environment

PURPOSE. Myasthenia gravis demonstrates a distinct predilection for involvement of the extraocular muscles (EOM), and we have hypothesized that this may be due to a unique immunological environment. To assess this hypothesis, we took an unbiased approach to analyze RNA expression profiles in EOM, diaphragm, and extensor digitorum longus (EDL) in rats with experimentally acquired myasthenia gravis (EAMG). METHODS. Experimentally acquired myasthenia gravis was induced in rats by intraperitoneal injection of antibody directed against the acetylcholine receptor (AChR), whereas control rats received antibody known to bind the AChR but not induce disease. After 48 hours, animals were killed and muscles analyzed by RNA expression profiling. Profiling results were validated using qPCR and immunohistochemical analysis. RESULTS. Sixty-two genes common among all muscle groups were increased in expression. These fell into four major categories: 12.8% stress response, 10.5% immune response, 10.5% metabolism, and 9.0% transcription factors. EOM expressed 212 genes at higher levels, not shared by the other two muscles, and a preponderance of EOM gene changes fell into the immune response category. EOM had the most uniquely reduced genes (126) compared with diaphragm (26) and EDL (50). Only 18 downregulated genes were shared by the three muscles. Histological evaluation and disease load index (sum of fold changes for all genes) demonstrated that EOM had the greatest degree of pathology. CONCLUSIONS. Our studies demonstrated that consistent with human myasthenia gravis, EOM demonstrates a distinct RNA expression signature from EDL and diaphragm, which is based on differences in the degree of muscle injury and inflammatory response

SPP1 Gene Polymorphisms and Response to Glucocorticoid Treatment among Myasthenia Gravis Patients

Oral glucocorticoids (GCs) are the primary therapy for patients with myasthenia gravis (MG). However, wide inter-individual variability exists in treatment response. A cohort of 250 MG subject treated with GCs were involved, and 12 polymorphisms in secreted phosphoprotein 1 (SPP1) gene were longitudinally evaluated for the contribution of response to the initial 3 months of GCs therapy. Improvement ≥ 3 units of Quantitative MG score (QMGS) change for patients with QMGS ＞ 16, ≥ 2 units of QMGS change for patients with QMGS between 2 to 16 or QMGS after treatment becoming zero was judged as being sensitive to GC. The gene product of SPP1, osteopontin (OPN), plasma levels were assessed among MG subjects in relationship clinical parameters including SPP1 genotype. No differences were observed for the allele distribution between GC sensitive/insensitive groups but the rs11728697 C/T + T/T genotypes were more frequent in the GC insensitive group compared to the GC sensitive group (100% versus 64.6%), indicating an association of rs11728697*T allele with GC insensitivity (pdominant = 0.018; OR = 1.065). One risk haplotype (AGTACT) was identified (p = 0.003, OR = 5.81) in the GC insensitive group compared with GC sensitive group. Mean OPN levels were higher among MG subjects (68.3 ± 43.0 ng/ml) compared to healthy controls (50.2 ± 38.7 ng/ml; p = 0.013). There was no association between OPN concentrations and the GC sensitive haplotypes. The genotypes and the haplotype with rs11728697*T allele in SPP1 gene were identified to be associated with insensitivity to GCs treatment and elevations in OPN plasma levels were found in the population of MG subjects. OPN may contribute to MG pathogenesis and treatment response in a select population of MG patients