12.2.4 - Transcriptional profiling of murine macrophages stimulated with cartilage fragments reveals a novel mechanism for osteoarthritis
- M. Hamasaki (Sapporo, JP)
- M. Hamasaki (Sapporo, JP)
- M. Terkawi (Sapporo, JP)
- T. Onodera (Sapporo, JP)
- K. Homan (Sapporo, JP)
- G. Matsumae (Sapporo, JP)
- Y. Tian (Sapporo, JP)
- H. Alhasan (Sapporo, JP)
- T. Ebata (Sapporo, JP)
- N. Iwasaki (Sapporo, JP)
Abstract
Purpose
Osteoarthritis (OA) is a progressive joint disease characterized by loss of articular cartilage and synovial inflammation accompanied by pain and disability. Synovial macrophages avidly engulf cartilage fragments and release inflammatory cytokines that exaggerates the osteoarthritic process and severity of disease. However, molecular mechanisms by which cartilage fragments triggers cellular responses are unclear and remain to be investigated. Therefore, the current study aims at analyzing molecular response of macrophages to cartilage fragments as step towards identifying molecular candidates for potential therapies.
Methods and Materials
Bone marrow derived macrophages and femoral head cartilages were isolated from C57/B6 mice. Cartilage fragments were prepared using optimal procedure for obtaining fragments similar to these isolated from synovial fluid of OA patients. Macrophages were co-cultured with cartilage fragments for 24h, and then harvested for RNA extraction and RNA sequencing. Data were analyzed for sequence alignment, transcript quantification, mapping and annotating. Significantly expressed genes with p-value ≤ 0.01 were subjected to gene ontology and pathway enrichment analyses.
Results
A total 153 genes were differentially upregulated, and 110 genes were down-regulated in response to cartilage fragments (Fig. 1). GO enrichment analysis revealed that the upregulated genes were mainly categorized into 11, 7, and 11 GO terms for cellular components, molecular function and biological process (p ≤ 0.001), respectively. The most significantly enriched terms included extracellular exosome, scavenger receptor activity, and innate immune response. (Fig. 2) Upregulated genes in response to cartilage fragments were enriched in 8 KEGG pathways including TNF-a signaling pathway, and toll-like receptor signaling. Moreover, ATF2, STAT3, ESR1, and NFKB1 were the most significantly enriched transcriptional factors in this response.
Conclusion
Bioinformatic analysis revealed that stimulated macrophages elicited common gene expression signature for inflammation, including activation of toll-like receptors, and TNF-α and NFKB signaling. Such data broaden our knowledge of the immunological response of macrophages to cartilage fragments and their role in osteoarthritic process.