α mem medium

The study was designed according to the Declaration of Helsinki and was approved by Ethic Committee of the Second Affiliated Hospital of Harbin Medical University (Ref: KY 2021-256). Written informed consent was obtained for 5 patients aging from 60 to 65 years old with OA, without rheumatoid arthritis, acute trauma, tumor, or infection of knee joint. The diagnosis of OA was based on clinical and radiological evidence of degenerative changes during surgery. The discarded specimens after total knee arthroplasty (TKA) were transferred into the biosafety cabinet within half an hour and washed twice with phosphate-buffered saline (PBS) solution to remove the blood, fat, and synovial fluid. The exposed cartilage tissue was cut into the final size about 0.5 mm × 0.5 mm, and put into 0.2% type II collagenase (Biosharp, China, BS163). After 4 hours, α-MEM medium (Cytiva, USA, SH30265.01) was added, with 10% fetal bovine serum (ExCell Bio, China, FSD500), 1% penicillin, and 1% streptomycin (Beyotime, China, C0222). Primary chondrocytes could be seen climbing out after about 7 days under optical microscope (ZEISS Axio Vert.A1, Germany). The medium was changed every 2 days and digested when the chondrocytes climbed to about 60% of the bottom. Chondrocytes used in this study were from passage 2 to 3 (P2-3).