Phenotypic features of chondrocytes. (a) Morphology of chondrocytes and synovial fibroblasts from patients with osteoarthritis. (b) Chondrocytes from four patients with osteoarthritis were incubated for 12 h. Total RNA from the cells was subjected to reverse transcription–polymerase chain reaction (RT–PCR) for type I collagen, type II collagen, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), as described in Materials and methods. Synovial fibroblasts and dermal fibroblasts were used as controls. (c) Chondrocytes from osteoarthritis patients were incubated with IL-1β (1 ng/ml) or tumor necrosis factor-α (TNFα; 10 ng/ml) for 12 h. Total RNA from the cells was subjected to RT–PCR for type I collagen, type II collagen, and GAPDH, as described in Materials and methods. Representative results from three patients are shown here.