The effect of IL-1β-stimulated synovial fibroblast (SFB)-derived exosomes on normal articular chondrocytes. (A) Articular chondrocytes were treated with fresh-DMEM, exosomes from non-stimulated SFB or exosomes from IL-1β-stimulated SFB. Exosomes from SFB were isolated by ultracentrifugation from six different donors. The expression of osteoarthritis-related genes was analyzed by real-time PCR. Matrix metalloproteinase (MMP)-13 was significantly upregulated, and ACAN significantly downregulated by exosomes from IL-1β stimulated SFB. Data are the means ± standard error of the mean (SEM). Comparison of mean values was performed by the Steel test; **P <0.01 versus Exo-IL. MD, fresh DMEM with 10% FBS; Exo -IL, exosomes from non-stimulated SFB; Exo + IL, exosomes from IL-1β stimulated SFB. (B) Exosomes were isolated from SFB-conditioned media (three separate cell preparations and experiments) using ExoQuick™ reagent. Exosomes from IL-1β-stimulated SFB significantly downregulated COL2A1 and ACAN expression and upregulated MMP-13 and ADAMTS-5 expression in articular chondrocytes. An exosome layer was isolated using ExoQuick™ reagent from fresh-DMEM and was used as control. Data are the means ± SEM. Comparison of mean values was performed by the Steel test; **P <0.01 versus Exo -IL. Cont, control.