Dmem f 12

CHO (Chinese hamster ovary cells), MDA-MB-231 (human breast cancer cells), MDA-MB-435S (human breast cancer cells) and MCF-10A (human mammary gland epithelial cells) were obtained from the Chinese Academy of Sciences Shanghai Institute for Biological Sciences-Cell Resource Center, which had characterized the cell lines by short tandem repeat profiling, cell morphology and karyotyping assay. CHO and MDA-MB-231 cells were cultured in Dulbecco's modified Eagle's medium (DMED, Gibco BRL, Rockville, MD, USA), MDA-MB-435S cells were cultured in Leibovitz's L-15 and MDA-MB-231 were cultured in DMEM/F-12 supplemented with 10% fetal bovine serum (TBD Science, Tianjin, China), 100 U/ml penicillin and 100 μg/ml streptomycin (Invitrogen, San Diego, CA, USA), at 37 °C, 5% CO₂. The TSP50-stable-expression CHO cell strain was obtained previously.^{22 (link)}

Primary chondrocytes were harvested according to a previous protocol.24 The New Zealand rabbits were purchased from the Third Military Medical University (Chongqing, China). The experiment was approved by Animal Care and Use Committee of the Third Military Medical University. Articular cartilage was removed from the knee joint of rabbits (1 month old, n = 3) with a sterile blade and minced. Cartilage pieces were digested with 0.2% w/v type collagenase (Sigma, St. Louis, MO, USA) in DMEM/F12 (Gibco, Grand Island, NY, USA) supplemented with 1% v/v penicillin‐streptomycin (Gibco) at 37°C in a 5% CO₂ incubator overnight. Digested tissue was filtered with a 40‐μm‐cell strainer (BD Bioscience, Franklin Lakes, NJ, USA) followed by centrifugation at 400 g for 5 minutes and resuspended in DMEM/F12 supplemented with 10% v/v foetal bovine serum (Tbdscience, Tianjin, China) and 1% v/v penicillin‐streptomycin. Medium was changed every 3 days. Cells were passaged at 80%‐90% confluence, and the passage 2 (P2) cells were used in the following experiments. For human TGF‐β1 stimulation, chondrocytes were treated with 5 ng/mL TGF‐β1 (Peprotech, Rocky Hill, NJ, USA) for 24 hours.