LAUSR

Micro(mi)RNAs are small, non‐coding RNA molecules known to play a significant role in osteoarthritis (OA) initiation and development, and similar to matrix metalloproteinases (MMPs), they participate in cartilage degeneration and cleave multiple extracellular matrices. The aim of this study was to determine whether the expression of MMP‐19 in interleukin (IL)‐1β‐induced human chondrocytes is directly regulated by miR‐193b‐3p. Expression levels of miR‐193b‐3p and MMP‐19 in normal and osteoarthritis (OA) human cartilage, and interleukin‐1 β (IL‐1β)‐induced human chondrocytes were determined by real‐time polymerase chain reaction. Additionally, expression level of MMP‐19 in IL‐1β‐induced human chondrocytes was estimated by Western blotting and immunohistochemistry analyses. The effect of miR‐193b‐3p on MMP‐19 expression was evaluated using transient transfection of normal human chondrocytes with miR‐193b‐3p mimic or its antisense inhibitor (miR‐193b‐3p inhibitor), and siMMP‐19. The putative binding site of miR‐193b‐3p in the 3′‐untranslated region (UTR) of MMP‐19 mRNA was validated by luciferase reporter assay. miR‐193b‐3p expression was reduced in OA cartilage compared to that in normal chondrocytes, while the opposite was observed for MMP‐19. Upregulation of MMP‐19 expression was correlated with downregulation of miR‐193b‐3p in IL‐1β‐stimulated normal chondrocytes. Increase in miR‐193b‐3p levels was associated with silencing of MMP‐19. Overexpression of miR‐193b‐3p suppressed the activity of the reporter construct containing the 3′‐UTR of human MMP‐19 mRNA and inhibited the IL‐1β‐induced expression of MMP‐19 and iNOS in chondrocytes, while treatment with miR‐193b‐3p inhibitor enhanced MMP‐19 expression. MiR‐193b‐3p is an important regulator of MMP‐19 in human chondrocytes and may relieve the inflammatory response in OA.