Expression of membrane-associated prostaglandin E synthase (mPGES-1) and cyclooxygenase-2 (COX-2) protein in cytokine-stimulated chondrocytes. (a) Chondrocytes from osteoarthritis patients were incubated for 48 h with interleukin-1β (IL-1β; 0.01–10 ng/ml) or tumour necrosis factor-α (TNFα; 0.01–10 ng/ml). Protein from the cells was subjected to Western blot analysis for mPGES-1 and COX-2. (b) Chondrocytes from osteoarthritis patients were incubated for 48 h with IL-1β (1 ng/ml) or TNF-α (10 ng/ml). The cells were then double-immunostained with tetramethylrhodamine β-isothiocyanate for mPGES-1 (upper row) and fluorescein isothiocyanate for COX-2 (lower row), and were examined under a Fluoview laser fluorescence microscope. Representative findings from three patients are shown here.