Osteoarthritis
Figure 2 Chondrocyte FBXW7 is reduced by mechanical overloading and decreased in OA articular cartilage. (A) IHC staining of FBXW7 in chondrocytes of mice treated with multiple loading episodes at peak loads of 13.5 N and controls, and quantitative analysis of FBXW7-positive chondrocytes as a proportion of the total chondrocytes. n=5 per group. Scale bar: 50 µm. P<0.001, 95% CI −39.30 to −20.16. (B) Representative images of safranin O/fast green staining (top) and immunofluorescence of FBXW7 (middle and bottom) in normal, moderate OA and severe OA cartilage. Scale bars: 200 µm (first row) and 100 µm (second row). (C,D) Quantitative analysis of OARSI scale and FBXW7-positive chondrocytes as a proportion of the total chondrocytes. n=5 per group. (E) Western blotting analysis of FBXW7 COL2A1, ADAMTS5, p16 INK4a and p21 in normal and severe OA cartilage. (F) Representative images of safranin O/fast green and IHC staining of FBXW7 in chondrocytes of mice aged 4 and 24 months. Scale bars: 100 µm (first row) and 50 µm (second row). (G) Quantification of the OARSI scale based on staining results in (F). n=10 per group. (H) Quantification of FBXW7-positive chondrocytes based on staining results in (F). n=10 per group. P<0.001, 95% CI −77.58 to −68.62. (I) Representative images of safranin O/fast green staining and immunofluorescence of FBXW7 in chondrocytes of controls and mice at 2, 4, 6 and 8 weeks after DMM surgery. Sale bars: 100 µm (first row) and 50 µm (second row). (J) Quantitative analysis of the OARSI scale of controls and DMM mice. n=10 per group. (K) Quantification of FBXW7-positive chondrocytes as a proportion of the total chondrocytes of control and DMM mice. n=10 per group. Data are shown as mean±SD. Statistical analyses were conducted using Student’s t-test (A,H), one-way analysis of variance followed by Tukey’s multiple comparison test (D,K), Kruskal-Wallis test followed by Dunn’s multiple comparisons test (OARSI score (C,J), or non-parametric Mann-Whitney U tests (OARSI score (G). Boxed area is enlarged in the bottom right corner. *P<0.05, **P<0.01. DMM, destabilisation of the medial meniscus; FBXW7, F-box and WD repeat domain containing 7; GAPDH, glyceraldehyde-3phosphate dehydrogenase; IHC, immunohistochemical; NC, control; OA, osteoarthritis; OARSI, Osteoarthritis Research Society International.
S4F–H). Taken together, these observations show that chon- drocyte FBXW7 is reduced by mechanical overloading and is decreased in the articular cartilage of patients with OA, aged mice and OA mice, implicating a potential role for FBXW7 in
OA mouse model, which exhibited a senescence phenotype, indicating that both mRNA and protein levels of FBXW7 were reduced with the progression of articular cartilage degeneration (figure 2I–K and online supplemental figure
Zhang H, et al . Ann Rheum Dis 2022; 81 :676–686. doi:10.1136/annrheumdis-2021-221513
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