Senescence-responsive miR-33-5p promotes chondrocyte senescence and osteoarthritis progression by targeting SIRT6.

Osteoarthritis (OA) is a prevalent disease among elderly individuals that is caused by cartilage degeneration. Chondrocyte senescence involved in the development of OA, and antisenescence therapies have been proposed for OA treatment. In our study, we identified the role of a microRNA, miR-33-5p, in promoting chondrocyte senescence and OA progression. miR-33-5p expression was upregulated under senescence conditions. miR-33-5p-mimic transfection can induce cellular senescence, while transfection of a miR-33-5p-inhibitor in chondrocytes alleviated senescence induced by IL-1β. Moreover, SIRT6 expression was downregulated under IL-1β treatment, and could be restored by miR-33-5p-inhibitor transfection. Luciferase assays revealed that miR-33-5p targeted the SIRT6 mRNA 3' UTR. In addition, SIRT6 mRNA expression showed negative correlations with senescence and OA degree in human cartilage. Bioinformatic analysis also confirmed the pro-senescence effect of miR-33-5p. Furthermore, periodic intraarticular injection of agomiR-33-5p induced cartilage loss and OA-like cartilage changes. To conclude, we revealed the pro-senescence and cartilage-destructive effect of miR-33-5p, whose expression was elevated under various senescence conditions, and showed that SIRT6 was one of its targets. Therefore, miR-33-5p is a potential therapeutic target for treating OA.