Long noncoding RNA related to cartilage injury promotes chondrocyte extracellular matrix degradation in osteoarthritis.

Objective: Long noncoding RNAs (lncRNAs) play crucial regulatory roles in diverse biologic processes, but knowledge of lncRNAs in osteoarthritis (OA) is limited. The aim of this study was to identify lncRNA expression in articular cartilage and to explore the function of cartilage injury-related lncRNAs (lncRNA-CIR) in OA.

Methods: To identify lncRNAs specifically expressed in OA cartilage, we compared the expression of lncRNAs in OA cartilage with that in normal cartilage using microarray and quantitative polymerase chain reaction (qPCR) analyses. In OA cartilage, lncRNA-CIR was specifically, differentially, and highly expressed. The function of lncRNA-CIR was determined by silencing and overexpression in vitro. Extracellular matrix (ECM)-related molecules were detected by qPCR, Western blot, and immunofluorescence analyses.

Results: Up to 152 lncRNAs were found to be differentially expressed (>8-fold) in OA and normal cartilage (82 lncRNAs more highly expressed and 70 less highly expressed in OA cartilage than in normal cartilage). A specific differentially expressed lncRNA-CIR was selected according to the results of the higher expression in OA cartilage and OA chondrocytes. The expression of lncRNA-CIR increased in chondrocytes with in vitro treatment with interleukin-1β and tumor necrosis factor α. Silencing of lncRNA-CIR by small interfering RNA promoted the formation of collagen and aggrecan and reduced the expression of matrix-degrading enzymes, such as MMP13 and ADAMTS5. The expression of collagen and aggrecan was reduced, whereas the expression of matrix-degrading enzymes was increased, after overexpression of lncRNA-CIR.

Conclusion: The results indicate that lncRNA-CIR contributes to ECM degradation and plays a key role in the pathogenesis of OA. We propose that lncRNA-CIR could be used as a potential target in OA therapy.