Reduction of IL-1β-induced MMP-13 mRNA expression by an EP2 agonist on rabbit normal or OA chondrocyte primary culture cells in vitro. Expression levels of MMP-13 mRNA in NRC and ORC at six hours after treatment with IL-1β (50 pg/ml), ONO-AE-259-01, selective EP2 agonist (each at a concentration of 0, 0.01, 0.1, and 1 μM), or a combination of IL-1β and ONO-AE-259-01. GAPDH was used as internal control. Using the ratio obtained for the untreated sample as a standard (1.0), the relative ratio of the treated samples was presented as the relative expression levels of the MMP-13 gene. Values are the mean ± standard deviation. NRC (n = 4) and ORC (n = 5). *P < 0.05. EP2, prostaglandin E2 receptor type 2; IL-1β, interleukin-1β; MMP-13, matrix metalloproteinase-13; NRC, non-treated rabbit chondroctes; ORC, ACLMT-operated rabbit chondrocytes.