miR‐335‐5p inhibits endochondral ossification by directly targeting SP1 in TMJ OA

Abstract Objective During the development of temporomandibular joint osteoarthritis, endochondral ossification is compromised which leads to condylar degeneration; miR‐335‐5p in endochondral ossification in osteoarthritic condylar cartilage tissue remains unclear. Methods Up‐regulated microRNA and its target gene were searched for endochondral ossification in osteoarthritis articular cartilage. The effect of increased or decreased miR‐335‐5p on endochondral ossification was evaluated by transfecting miR‐335‐5p mimics or miR‐335‐5p inhibitor in vitro in chondrocytes C28/I2. Finally, we injected the temporomandibular joint of rats intra‐articularly with agomiR‐335 in a unilateral anterior crossbite rat model to determine the in vivo regulation of miR‐335. Results After the onset of temporomandibular joint osteoarthritis, miR‐335‐5p levels were gradually up‐regulated, whereas endochondral ossification‐related genes were down‐regulated in condylar cartilage specimens. Our results showed that miR‐335 inhibited endochondral ossification after administration of a miR‐335 antagonist into the temporomandibular joint articular cavity of a unilateral anterior crossbite rat model. AgomiR‐335, a miR‐335 agonist, inhibited matrix mineralization in fibrocartilage stem cells in vitro and then miR‐335‐5p negatively regulated chondrocyte activity by directly targeting SP1 via promoting transforming growth factor‐β/Smad signalling. Conclusion miR‐335‐5p can significantly inhibit endochondral ossification; therefore, its inhibition may be beneficial for the treatment of temporomandibular joint osteoarthritis.