Figure 3.

Seven-day stimulation with inflammatory factors triggers ERS in chondrocytes and enhances angiogenesis

(A and B) The expression of ER stress (ERS) genes (GRP78, GRP94; (A) and unfolded protein response (UPR) pathway genes (IRE1a, XBP-1, PERK, CHOP, ATF6, ERO1B; (B) was measured in chondrocytes cultured with TNF-α, IFN-γ or IL-17 for 7 days.

(C and D) Protein levels of GRP78, GRP94, and ATF6 were measured with WB and quantified using ImageJ software.

(E) IHC analysis of GRP78 and ATF6 expression on femur heads of healthy donors (HD), ankylosing spondylitis patients (AS) and osteoarthritis patients (OA). Scale bar, 100 μm. Quantification of the proportions of GRP78- and ATF6-positive chondrocytes in femur heads (n = 10 people per group).

(F) FGF2 expression was measured by ELISA in chondrocytes cultured with 4-PBA.

(G) Transwell migration assays were performed on HUVECs cultured in chondrocyte CM. The number of migratory cells was calculated and quantified using ImageJ software. Scale bar, 100 μm. Bars show the means ± SD.

∗p < 0.05 and ∗∗p < 0.01, 2-tailed Student's t-test (A, B, D, F, and G) and one-way ANOVA followed by Dunnett's post hoc test (E).