Biologic Characteristics of Shoulder Articular Cartilage in Comparison to Knee and Ankle Articular Cartilage From Individual Donors

Objective: To describe histological and metabolic characteristics of glenohumeral joint (GHJ) articular cartilage and compare to knee and ankle joints. Design: Macroscopically healthy human humeral head, glenoid, knee, and ankle articular cartilage were obtained from tissue donors (N = 16, 9 males, 7 females; age 45-78 years), within 24 hours of death. Gross morphology of each joint was assessed using Collins grading. Cartilage explants were removed from the entire surface of each joint, cultured for 48 hours with or without interleukin-1β and processed for histology with Safranin O, proteoglycan (PG) synthesis/content, and polymerase chain reaction for collagen II, aggrecan, and SOX9. Results were compared between uncultured and cultured controls and across all 3 joints. Results: Structural differences were seen on histology between GHJ cartilage and knee and ankle cartilage of the same Collins grade, specifically, depletion of Safranin O staining in the extracellular matrix. Treatment of glenoid and humerus specimens with IL-1β demonstrated a trend toward decreased PG synthesis in each explant but this decrease did not reach significance. There was no significant difference in PG synthesis between humerus, glenoid, knee, and ankle samples at baseline, day-0 control, 48-hour control, and 48 hours after treatment with 0.1 ng or 10 ng of IL-1β. There were no significant increases in collagen II, SOX9, and aggrecan expression in glenoid and humeral head cartilage samples treated with IL-1β compared to baseline controls. Conclusions: GHJ articular cartilage did not significantly differ from ankle or knee cartilage with regard to PG synthesis and gene expression. However, it did differ in its histological appearance in normal state.