Single-cell sequencing of murine articular cartilage

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage loss, bone remodeling, synovial inflammation, and significant joint pain, often resulting in disability. Injury to the synovial joint such as the anterior cruciate ligament (ACL) tear is the major cause of OA in young adults. Currently, there are no approved therapies available to prevent joint degeneration or rebuild articular cartilage destroyed by OA, primarily because our understanding of the cellular and molecular changes that contribute to joint damage is very limited. The synovial joint is a complex structure composed of several tissues including articular cartilage, subchondral bone, synovium, synovial fluid, and tensile tissues including tendons and ligaments. In the present study, using single-cell RNA sequencing (scRNA-seq), we examined the cellular heterogeneity in articular cartilage from mouse knee joints and determined the knee joint injury-induced early molecular changes in the chondrocytes that could contribute to OA. Right knee joints of 10-week-old C57Bl/6J mice were injured using a tibial compression injury model. Uninjured and injured hindlimbs were collected at 3- and 7-days post-injury. Subsequently, knee joints were isolated, about ~1mm tissue was cut from the end of femur and tibia and digested to obtain single cell suspensions. After depleting CD45+ immune cells and Ter119+ erythrocytes, the remaining cells were sequenced to obtain single-cell level gene expression profiles.