RNA-sequencing analysis of muscle biopsy samples from patients with inclusion body myositis and those with polymyositis (P3.449)

Objective: To detect the differential expressed genes (DEGs) and the difference of signaling pathways among the patients with inclusion body myositis (IBM), polymyositis (PM), and normal controls (NCs), comprehensively. Background: Both IBM and PM are characterized by endomysial infiltrates of CD8+ cytotoxic T-lymphocytes invading major histocompatibility class 1 expressing non-necrotic muscle fibers (CD8-MHC-1 complex). However patients with IBM have rimmed vacuoles or abnormal protein accumulation and they are refractory to treatments. Design/Methods: We analyzed muscle biopsy samples from 62 patients with CD8-MHC-1 complex (43 IBM, 9 PM, and 10 unclassifiable) and 9 NCs by RNA-sequencing (Illumina Hiseq 2500). We detected DEGs by edgeR and performed gene set enrichment analysis by R-subread, using KEGG pathway database. Results: There were 8588 DEGs (FDR Conclusions: The gene sets of the innate and adaptive immune systems were upregulated in the muscle biopsy samples of IBM, compared with those of PM. Although CD8-MHC-1 complex seemed to have a key role in the pathogenesis of both IBM and PM, there were some differences between patients with IBM and PM as to the innate and adaptive immune systems. Disclosure: Dr Ikenaga has nothing to disclose. Dr. Kubota has nothing to disclose. Dr. Ishiura has nothing to disclose. Dr. Date has nothing to disclose. Dr. Tsuji has nothing to disclose. Dr. Goto has nothing to disclose. Dr. Shimizu has nothing to disclose.