BACKGROUND:Matrix metal oproteinase-13 is most active in the degradation of col agen type II in the extracel ular matrix of cartilage. Interleukin-1 (IL-1) is thought to be the inducer of matrix metal oproteinases, and participates in the degradation and degeneration of articular cartilage. OBJECTIVE:To study the influence of IL-1βon microRNA-27b (miR-27b) and matrix metal oproteinase-13 expression of chondrocytes in rats. METHODS:Chondrocytes isolated from seven male Wistar rats were cultured and divided into IL-1βstimulation group and control group. No stimulus was given in the control group;10μg/L of serum free medium was used to culture rat chondrocytes in the IL-1βstimulation group. Cel growth was observed at 0, 24, and 48 hours under an inverted microscope. miR-27b and matrix metal oproteinase-13 expression in the cultured chondrocytes were detected. RESULTS AND CONCLUSION:The relative expression of matrix metal oproteinase-13 in rat chondrocytes was gradual y increased when induced by IL-1βat 0, 24, and 48 hours (P<0.05). Expression of miR-27b and miR-31 in rat chondrocytes at 24 and 48 hours induced by IL-1βgradual y decreased (P<0.05);conversely, expression of MiR-26a, miR-26b, miR-23, and miR-204 gradual y increased (P<0.05). After 48 hours of IL-1βinduction, expression of miR-27b was the lowest in rat chondrocytes (P<0.05). These findings suggest that IL-1βinhibits miR-27b expression, strengthens the expression of matrix metal oproteinase-13, and damages chondrocytes, contributing to both the onset and progression of osteoarthritis.