Fig. 2: The exosome-like vesicles form osteoarthritic chondrocyte promote mature IL-1β production in macrophages.

a Human primary chondrocytes were treated with 10 ng/ml of IL-1β or negative control ddH₂O for 12 h and then washed with PBS twice. Subsequently, the chondrocytes were cultured in serum-free cell culture media for 36 h and the supernatant exosome-like vesicles were extracted using ultrafiltration assay for NanoSight analysis. pChC^ILpre-exos, exosome-like vesicles from IL-1β-pretreated primary chondrocytes; pChC^NCpre-exos, exosome-like vesicles from ddH₂O-pretreated primary chondrocytes; b PMA-induced THP-1 cells were treated with pChC^NCpre-exos or pChC^ILpre-exos in the presence or absence of LPS and then the indicated mRNA level of treated cells was detected using qPCR assay. c PMA-induced THP-1 cells were treated with pChC^NCpre-exos or pChC^ILpre-exos in the presence or absence of LPS. Then the supernatant TNF-α and IL-1β were measured using ELISA assay. d The cells were treated as c and then the supernatant proteins were extracted for Western blot assay. e PMA-induced THP-1 cells were treated with pChC^NCpre-exos or pChC^ILpre-exos in the presence of LPS for 12 h, followed by 3 mM ATP for 30 min. Then the supernatant IL-1β were measured using ELISA assay. f PMA-induced THP-1 cells were treated with pChC^NCpre-exos or pChC^ILpre-exos in the presence or absence of LPS. Subsequently, the fluorescence-labeled ASC protein in the treated cells by immunofluorescence were observed under fluorescence microscope and the corresponding statistical graph for the ratio of ASC-specking cells were shown in the right. ANOVA with Bonferroni’s multiple comparison test was used, ***p < 0.001; **p < 0.01; *p < 0.05; ns, no significance