Fig. 1: High cholesterol aggravates OA cartilage degeneration.

a Levels of serum total cholesterol (TC), low-density lipoprotein (LDL), and body mass index (BMI) in OA (n = 100) or meniscal injured (as control) patients (n = 91) (unpaired two-tailed Student’s t-test). b Safranin-O, toluidine blue, and type II collagen immunohistochemistry (IHC) staining in human cartilage explants treated with cholesterol (50 μg/ml) and/or TNF-α (20 ng/ml) for 14 d (n = 5). c The integrated optical density (IOD) value for proteoglycan content and type II collagen (COLII) determined by safranin O and immunohistochemistry staining (n = 5, one-way ANOVA). d Scheme of the high-cholesterol diet (HCD) feeding and ACLT surgery in mice. e The general view, body weight, serum TC, serum LDL, and pain response times of HCD mice compared with RD mice (n = 10, two-tailed Student’s t-test). f Representative images of safranin O-fast green, IHC staining of COLII, and the corresponding Osteoarthritis Research Society International (OARSI) scores from HCD mice and RD mice subjected to Sham or ACLT operation for 4 weeks (n = 9, one-way ANOVA). g Heatmap of mRNA-seq analysis in cartilage tissue of HCD and RD mice. h Quantification of mRNA levels for COL2A1, ACAN, SOX9, and MMP13 in rat chondrocytes treated with cholesterol (50 μg/ml) and/or TNF-α (20 ng/ml) for 3 d (n = 4, one-way ANOVA). i The protein levels of SOX9 and COL2A1 in rat chondrocytes treated with cholesterol (50 μg/ml) and/or TNF-α (20 ng/ml) for 5d (n = 3). Data are shown as the mean ± SD. *P < 0.05; **P < 0.01; ***P < 0.001. n indicates the number of biologically independent samples, mice per group, or human specimens.