Effects of synovial fibroblast (SFB)-derived exosomes on angiogenic activity. SFB-derived exosomes were tested on human umbilical vein endothelial cells (HUVEC) for stimulation of migration and tube formation. Exosomes were isolated by ExoQuick™ reagent. (A) Migration activity was significantly higher in HUVEC treated with the exosomes from IL-1β-stimulated SFB as compared to PBS and the exosomes from SFB without IL-1β. HUVEC migration was not induced in HUVEC by IL-1β alone. Data are the means ± standard error of the mean (SEM). Comparison of mean values was performed by the Steel test; *P <0.05 versus control. (B) Tube length was significantly greater in HUVEC incubated with the exosomes from IL-1β-stimulated SFB than in HUVEC incubated with PBS and the exosomes from non-stimulated SFB. Data are the means ± SEM. Comparison of mean values was performed by the Steel test; *P <0.05 versus control. Cont, isolated exosomes from fresh-DMEM with 10% FBS; Exo -IL-1β, exosomes from non-stimulated SFB; Exo + IL-1β, exosomes from IL-1β stimulated SFB; Cont, control.