Fig 1: Up-regulation of ATF3 reverses the effects of periodic mechanical stress on apoptosis, inflammation and extracellular matrix proteins expression in osteoarthritic chondrocytes. (A and B) Apoptotic rate of OA cells was detected by flow cytometry; (B–D) Levels of TNF-α (B), IL-6 (C) and IL-8 (D) in OA cells were detected by ELISA; (E and F) Protein expression levels of collagen II, aggrecan and MMP-13 in OA cells were detected by Western blot. Error bars are mean ± s.d. *P < 0.05 and **P < 0.01 vs IL-1β + NC group.
Fig 2: Knockdown of ATF3 alleviates symptoms and pathological knee joint damage in rats with OA. (A) Width of the knee joints of rats. (B) Knee pain was assessed by weight-bearing test; (C–E) Serum levels of TNF-α (C), IL-8 (D) and IL-6 (E) were measured by ELISA (n = 4); (F) Histopathological changes of the knee joint from rats (n = 2) were observed by safranin O staining. Scale bar = 100 μm. Error bars are mean ± s.d. *P < 0.05 and **P < 0.01 vs OA+si-NC group.
Fig 3: ATF3 regulates the Akt signaling pathway in OA rats. (A and B) Western blot was used to detect the protein levels of p-Akt, Akt and ATF3 in the articular cartilage in the Sham and OA groups, Error bars are mean ± s.d. *P < 0.05; **P < 0.01 vs Sham group; (C and D) Western blot was utilized to measure the protein levels of p-Akt, Akt and ATF3 in the articular cartilage in the OA + si-NC and OA + si-ATF3 groups, Error bars are mean ± s.d. **P < 0.01 vs OA + si-NC group, n = 4.
Fig 4: Effects of periodic mechanical stress on inflammation, extracellular matrix proteins and ATF3-Akt axis in osteoarthritic chondrocytes. IL-1β-induced chondrocytes were treated without (group 0) or with PMS under a device height of 1 cm (group 1), 2 cm (group 2), 4 cm (group 4), and 8 cm (group 8). (A–C) Levels of TNF-α (A), IL-6 (B) and IL-8 (C) in the supernatant of OA cells measured by ELISA; (D and E) Protein expression levels of extracellular matrix proteins (collagen II, aggrecan, and MMP-13) in OA cells detected by Western blot; (F and G) Protein expression levels of p-Akt, Akt, and ATF3 in OA cells detected by Western blot. Error bars are mean ± s.d.*P < 0.05; **P < 0.01 vs Group 0.
Fig 5: Effects of ATF3 knockdown on extracellular matrix proteins in the articular cartilage of rats with OA. (A–D), Expression of collagen II (A), aggrecan (B) and MMP-13 (C) in rat knee joints from rats (n=4) detected by immunohistochemistry and quantified by ImageJ software (D). Scale bar = 400 μm. Error bars are mean ± s.d. **P < 0.01 vs OA+si-NC group.
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