Fig. 4

Effect of silencing UPR genes under H-UPR conditions in human osteoarthritic chondrocytes. a Silencing (si) ERN1, PERK, ATF6B, and CREB3L2 (Western blots), and the resulting expression of COL1a1, COL2a1, MMP-1, MMP-13, ADAMTS4, and ADAMTS5 (qPCR) (n = 7–10). The non-targeting or random siRNA (siNT) values were calculated for each primer as fold change over the control, which was assigned an arbitrary value of 1, and the mean ± SEM was 1.02 ± 0.03 for all the primers grouped. b Effect of IL-1β (100 pg/ml) with or without (control) siPERK, siATF6B, and siCREB3L2 on COL2a1, ADAMTS4, and ADAMTS5 levels (n = 5–7). Each control was assigned an arbitrary value of 1 and the effect of the treatment evaluated as fold change over control. Also represented are the siNTs for COL2a1, ADAMTS4, and ADAMTS5 respectively, showing values similar to those of the control. Data are expressed as mean ± SEM, and p values were assessed by the one-sample t test, comparing the treated chondrocytes to the control