Priority Research Paper Volume 12, Issue 16 pp 15882—15905

Figure 2. Downregulation of Cx43 by oleuropein decreases GJIC and improves the phenotype of OACs. (A) Oleuropein (Oleu) treatment significantly decreases GJIC evaluated by an SL/DT assay when OACs were exposed with this molecule for 2 h (top, n=6 independent experiments; Student’s t test, P<0.0001). The results were confirmed by calcein transfer by flow cytometry (n=4 independent experiments; Student’s t test, P=0.0037). (B) Graph showing the effect of oleuropein on GJIC when healthy chondrocytes (N) were exposed to 10 μM oleuropein compared with OACs (n=5 independent experiments; one-way ANOVA, P=0.0004). (C) OACs cultured for 7 days with 10 μM Oleu showed reduced expression of the mesenchymal markers CD105 and CD166, analyzed by flow cytometry. Student’s t test, P=0.0039 (CD105) and P=0.0022 (CD166), n=6 independent experiments. CD166 levels were also analyzed by western blot (n=3 independent experiments, Student’s t test, P=0.0046). (D) Downregulation of Cx43 increased Col2A1, detected by immunofluorescence in OACs treated with 10 μM oleuropein. Graphs represent the corrected total cell fluorescence (CTCF) of Cx43 and Col2a1 (n=4 independent experiments). Student’s t test, P<0.0001 (Cx43), and P=0.0007 (Col2a1). (E) mRNA levels of IL-1ß, IL-6, COX-2 and MMP-3 of OACs cultured in normal medium (UT) exposed to 10 μM oleuropein for 2 h. n=4–7 independent experiments. Student’s t test: P= 0.033 (IL-1ß), P<0.0001 (IL-6), P=0.1013 (COX-2), P=0.0466 (MMP-3). (F) IL-6 detected by ELISA when OACs were treated with oleuropein for 72 h (n=4 independent experiments, Student’s t test, P=0.0345). IL-6 (n=3 independent experiments) and COX-2 (n=4 independent experiments) protein levels detected by western-blot in OACs treated with 10 μM oleuropein for 72 h. Student’s t test, P=0.0193 (IL-6), P=0.0141 (COX-2). Data is expressed as mean±SD; *P<0.05, **P<0.01 and ***P<0.0001.