Biomedical subjects

Tomohisa Okamura

Publications and source records attributed to Tomohisa Okamura.

3 recordsLinked to original sources

PubMed2026

CASTOR1 Regulates Humoral Immune Responses and Contributes to the Pathogenesis of Systemic Lupus Erythematosus.

OBJECTIVE: CASTOR1 senses arginine and regulates mammalian target of rapamycin complex 1 (mTORC1), a central metabolic signaling molecule. This study aimed to elucidate the roles of CASTOR1 in humoral immune responses. METHODS: We analyzed human B cell transcriptomes from healthy controls and patients with systemic lupus erythematosus (SLE) via correlation analysis and gene set variation analysis using our database, Immune Cell Gene Expression Atlas from the University of Tokyo. Castor1-deficient and B cell-specific Castor1-deficient mice were used for analyses of serum immunoglobulins and autoantibodies, urinary proteins, renal pathology, gene expression, and flow cytometry in spleen and bone marrow cells. The culture supernatant of splenic B cells was used for immunoglobulin (Ig) analysis. RESULTS: Transcriptomic analysis of bulk RNA sequencing data from various B cell subsets in patients with SLE (n = 136; n = 129 included in the primary analysis) revealed a correlation between CASTOR1 expression and disease activity, with CASTOR1 expression in plasmablasts inversely correlated with Systemic Lupus Erythematosus Disease Activity Index 2000 (r = -0.32, P = 0.00031). Castor1-deficient mice exhibited increased plasma cell populations in the spleen and bone marrow, elevated serum IgG levels, production of anti-double-stranded DNA antibodies, and glomerulonephritis with IgG deposits, reflecting SLE-like autoimmunity. Moreover, B cell-specific Castor1-deficient mice showed increased plasma cell counts, elevated serum IgG levels, and glomerulonephritis, indicating that Castor1 might regulate systemic humoral immunity via a B cell-intrinsic mechanism. CONCLUSION: CASTOR1 plays a regulatory role in humoral immunity and may contribute to the pathogenesis of autoimmune diseases such as SLE, representing a potential therapeutic target.

Journal Article↗

PubMed2026

Distinct periarticular muscle transcriptomes: inflammation in rheumatoid arthritis versus metabolic dysregulation in osteoarthritis.

OBJECTIVES: Periarticular skeletal muscle abnormalities are recognised in rheumatoid arthritis (RA) and osteoarthritis (OA), but their divergent molecular pathologies are poorly defined. This study aimed to elucidate and directly compare the transcriptomic profiles of periarticular muscle in patients with RA and OA. METHODS: We performed bulk RNA sequencing of periarticular skeletal muscle samples collected during total joint arthroplasty from RA (n=6) and OA (n=4) patients. Differential gene expression analysis, weighted gene co-expression network analysis (WGCNA), pathway enrichment, and gene set variation analyses were conducted to identify disease-specific molecular features and their clinical associations. RESULTS: The two conditions showed fundamentally distinct profiles. RA muscle exhibited a pronounced inflammatory signature, characterised by upregulation of cytokine-responsive genes including FOS, EGR1, and CXCL2, and enrichment of tumour necrosis factor-α and interleukin-6 (IL-6)/JAK-STAT3 signalling. In contrast, OA muscle was characterised by metabolic dysregulation, with upregulation of genes linked to adipogenesis (PCK1, SFRP4) and significant enrichment of epithelial-to-mesenchymal transition (EMT) signalling. These divergent profiles were further supported by WGCNA, which identified distinct modules reflecting heightened innate immune and complement activation in RA, and disrupted metabolic processes in OA. Notably, in RA, the IL-2-STAT5 signalling pathway was unique among those tested in showing a strong positive correlation with DAS28-ESR (r=0.94, p=0.019). CONCLUSIONS: This study reveals distinct molecular pathologies in the periarticular muscle of RA and OA. RA muscle shows an intense inflammatory profile potentially linked to cachexia, whereas OA muscle displays features of metabolic disease and pro-fibrotic remodelling.

Humans↗

PubMed2024

Muscle Tissue Transcriptome of Idiopathic Inflammatory Myopathy Reflects the Muscle Damage Process by Monocytes and Presence of Skin Lesions.

OBJECTIVE: We aim to investigate transcriptomic and immunophenotypic features of muscle specimens from patients with idiopathic inflammatory myopathy (IIM). METHODS: Bulk RNA-sequencing was performed on muscle biopsy samples from 16 patients with dermatomyositis (DM) and 9 patients with polymyositis (PM). Seven tested positive for anti-aminoacyl transfer RNA synthetase antibodies in the patients with DM (ARS-DM). We conducted weighted gene coexpression network analysis (WGCNA), differentially expressed gene (DEG) analysis, and gene set variation analysis to assess contributions of specific pathways. Cell proportions in muscle specimens were estimated using a deconvolution approach. RESULTS: WGCNA revealed significant positive correlations between serum creatine kinase (CK) levels and gene modules involved in cellular respiration, phagocytosis, and oxidative phosphorylation (OXPHOS). Significant positive correlations were also observed between CK levels and proportions of CD16-positive and negative monocytes and myeloid dendritic cells. Notably, patients with DM demonstrated enrichment of complement and interferon-α and γ pathway genes compared with those with PM. Furthermore, ARS-DM demonstrated a higher proportion of Th1 cells and DEGs related to OXPHOS. Additionally, serum Krebs von den Lungen-6 levels correlated with gene modules associated with extracellular matrix and the transforming growth factor-β signaling pathway. CONCLUSION: Our study highlights a significant involvement of monocytes in muscle damage and delineates pathologic differences among IIM subtypes. DM was characterized by complement and interferon-α and γ signaling, whereas ARS-DM was associated with OXPHOS. Distinctive gene expression variations in muscle specimens suggest that different pathologic mechanisms underlie muscle damage in each IIM phenotype.

Humans↗