Role of lncRNA XIST/miR-146a Axis in Matrix Degradation and Apoptosis of Osteoarthritic Chondrocytes Through Regulation of MMP-13 and BCL2.

Growing evidence demonstrates the critical roles of long non-coding RNAs (lncRNAs) in osteoarthritis (OA) pathogenesis. The lncRNA XIST is one of the most commonly studied; however, its function remains unclear. This study aimed to research the molecular mechanism of XIST in human OA chondrocytes. Cells were transfected with small interfering RNA against XIST or with a microRNA (miR)-146a inhibitor in the presence of interleukin (IL)-1β. Viability was detected using MTT; apoptosis using cytometry; and XIST, miR-146a, B-cell lymphoma (BCL)2, and metalloproteinase (MMP)-13 expression using real-time PCR. The analysis of p50 and p65 nuclear factor (NF)-κB was conducted using PCR and immunofluorescence. Our findings showed that XIST was highly expressed in OA chondrocytes when compared to T/C-28a2 lines. Furthermore, XIST silencing significantly promoted survival and limited apoptosis, with a concomitant over expression of BCL2, reduction in MMP-13 mRNA, and NF-κB activation after IL-1β stimulus. Conversely, miR-146a was significantly down-regulated in OA cells, while its levels were increased following XIST silencing; moreover, miR-146a inhibition induced opposite results to those caused by XIST. Finally, the down-regulation of XIST was correlated to the over-expression of miR-146a, with a consequent modulation of BCL2, MMP-13, and NF-κB. This study suggests an influence of the XIST/miR-146a axis on the viability, apoptosis, and matrix degradation occurring in OA.