Figure 3

Stimulation of articular chondrocyte expression and release of NGF by IL-1β. Human OA chondrocytes were stimulated for 24 hours with increasing concentrations of IL-1β (0, 0.1, 1 and 10 ng/mL) and NGF mRNA expression (A) and release into cell supernatant (B) were measured by quantitative RT-PCR and ELISA, respectively (n = 4). Control cells released 19.2 ± 8.7 pg/mL NGF. (C-E) Primary cultures of mouse articular chondrocytes were stimulated either with increasing concentrations of IL-1β (0, 0.1, 1 and 10 ng/mL) for 24 hours (n = 3) (C and D) or with IL-1β (10 ng/mL) for 2, 4, 6, 8 and 24 hours (n = 3) (E). As a control (ctrl), chondrocytes were incubated without IL-1β for 24 hours (E). NGF mRNA expression was determined by quantitative RT-PCR (C). The amount of NGF mRNA was normalized against the amount of HPRT mRNA measured in the same cDNA. NGF protein levels were measured in conditioned media by ELISA (D and E). *P <0.05, **P <0.01, ***P <0.001. ELISA, enzyme-linked immunosorbent assay; IL-1β, interleukin 1β; NGF, nerve growth factor; OA, osteoarthritis.