T. Onodera (Sapporo, JP)
Hokkaido University Graduate School of Medicine Orthopaedic departmentPresenter Of 1 Presentation
12.2.9 - Inflamed macrophages by cartilage fragments elicits typical gene expression signature of endochondral ossification in chondrocytes
Abstract
Purpose
Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, synovial inflammation and osteophyte formation. The disability of joint is associated with a loss of the highly sulfated proteoglycans and an increase of apoptotic chondrocytes in cartilage matrix. The continued mechanical stress on the affected cartilage leads to production of cartilage fragments that are known to provoke the production of macrophages pro-inflammatory cytokines and chondrocyte catabolic factors. A better understanding of the molecular response of chondrocytes elicited by inflammatory macrophages phagocytizing cartilage fragments may provide essential clues for development of novel therapeutic agents. To this end, we examined the gene profile of chondrocytes stimulated with inflamed macrophages by cartilage fragments.
Methods and Materials
Femoral head cartilage of C57/B6 mice were separated and crushed for preparing cartilage fragments or enzymatically treated for isolation of chondrocytes. Macrophages were prepared from the same mice by culturing bone marrow-derived cells with growth factors. Thereafter, chondrocytes were co-cultured with macrophages stimulated by cartilage fragments using transwell culture system for 48 h. RNA-Seq analysis was performed for chondrocyte RNA, and data were subjected for gene ontology and pathway analyses.
Results
A total 340 transcripts were significantly upregulated in these chondrocytes (Fig. 1A) and were enriched in multiple biological processes including ossification, bone mineralization and connective tissue development (Fig. 1B). Major functional pathways involved in this response were ECM-receptor interaction, spliceosome, and protein digestion and absorption (Fig. 1C).
Conclusion
Our ongoing work is to validate results using cartilage ex vivo models. These results showed the pathological impact of inflamed macrophages on the function of chondrocytes and progression of the disease. Our results suggest that macrophages activated by cartilage fragments might be involved in the endochondral ossification signals occurred in progressive OA.