Objectives Matrix metalloproteinase (MMP) 13 is a pathogenic collagenase that causes cartilage destruction and plays a leading role in causing osteoarthritis. This study focused on 114 genes that are differentially expressed between intact and damaged osteoarthritis cartilage, in order to determine which molecules are involved in suppressing MMP-13 expression.
Methods MMP-13 concentrations were measured in the supernatant of human osteoarthritis chondrocyte cultures transfected with small interfering RNA (siRNA) against the 114 genes. MMP-13 levels changed most dramatically in response to siRNA against prostaglandin EP2 receptor. The authors performed further measurements of MMP-13 production in osteoarthritis chondrocytes stimulated by the EP2 agonist butaprost in the presence or absence of interleukin-1β (IL-1β) and/or cyclooxygenase-2 (COX-2) inhibitor. They also assessed the effect of butaprost on chondrocyte viability, and investigated the involvement of the cAMP–protein kinase A (PKA) pathway on EP2 signalling using inhibitors. Cartilage-related gene expression was examined in chondrocytes treated with butaprost. The authors also investigated which E series of prostaglandin (EP) receptors are expressed in osteoarthritis cartilage.
Results MMP-13 messenger RNA expression was significantly affected by two molecules, EP2 receptor and SLC14A1, a urea transporter. In IL-1β-treated osteoarthritis chondrocytes, butaprost suppressed MMP-13 production, which was further decreased by COX-2 inhibitor. EP2 signalling downregulated MMP-13 mRNA expression via the cAMP–PKA pathway without affecting cell viability. Although EP2 signalling enhanced IL-6 expression, the expressions of several catabolic factors (MMP-1, MMP-3, MMP-13, ADAMTS5, IL-1β and tumour necrosis factor alpha) were inhibited. EP2 receptor was the major EP receptor in osteoarthritis cartilage.
Conclusion The results suggest that EP2 signalling has ‘anti-catabolic’ effects in osteoarthritis chondrocytes.
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Funding This work was supported by Santen Pharmaceutical Co, Ltd, the National Institute of Biomedical Innovation (grant-in-aid for scientific research), the Japanese Ministry of Education, Culture, Sports, Science and Technology, the Japanese Ministry of Health, Labour and Welfare, the Kato Memorial Trust for Nanbyo Research, the Japan Medical Association, the Nagao Memorial Fund, the Kanae Foundation for Life and Socio-Medical Science, the Japan Research Foundation for Clinical Pharmacology, the Kanagawa Nanbyo Foundation, the Kanagawa Academy of Science and Technology (research grants), the Japan College of Rheumatology, the Nakajima Foundation, the Osaka Foundation for Cancer Research, the Japan Society for the Promotion of Science, the New Energy and Industrial Technology Development Organization, Mochida Pharmaceutical Company, Ltd, the Kanagawa High-Technology Foundation, the Kanto Bureau of Economy, Trade and Industry, the Mitsui Life Insurance Company, Ltd, the Uehara Memorial Foundation, the Takeda Science Foundation, the Heiwa Nakajima Foundation, the Sagawa Foundation for Promotion of Cancer Research, ITSUU Laboratory Research Foundation and the Tokyo Biochemical Research Foundation.
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the Ethics Review Committee of St Marianna University School of Medicine (no 442).
Provenance and peer review Not commissioned; externally peer reviewed.