Increased expression of cyclooxygenase-2 in synovium tissues and synovial fluid from patients with knee osteoarthritis is associated with downregulated microRNA-758-3p expression

Cyclooxygenase-2 (COX-2) is a common factor in inflammation, and its specific regulatory mechanism has not been fully elucidated. The present study aimed to investigate COX-2 mRNA and protein expression levels in synovium tissues and synovial fluid from patients with knee osteoarthritis (KOA), and determine the molecular mechanism by which microRNA (miRNA/miR)-758 regulates KOA via COX-2. A total of 37 patients with KOA and 29 patients with acute knee trauma (control group) were enrolled in the present study. Reverse transcription-quantitative PCR analysis was performed to detect miR-758-3p and COX-2 mRNA expression, while western blotting and ELISA were performed to detect COX-2 protein expression in synovium and synovial fluid, respectively. The dual-luciferase reporter assay was performed to verify the interaction between miR-758-3p and the 3'-untraslated region (UTR) of COX-2 mRNA. Synovial cells were transfected with agomiR-758-3p, and the MTT assay was performed to assess cell proliferation. The results demonstrated that COX-2 expression was higher in patients with KOA than those with acute knee trauma. Conversely, miR-758-3p expression was lower in patients with KOA than those with acute knee trauma. Notably, miR-758-3p interacted with the 3'-UTR of COX-2 mRNA to regulate its expression. Overexpression of miR-758-3p inhibited the expression and release of COX-2, as well as the proliferation of human KOA synovial cells. Taken together, these results suggest that COX-2 expression is upregulated in synovium tissues and synovial fluid from patients with KOA, which is associated with downregulated miR-758-3p expression. In addition, miR-758-3p affects the proliferation of synovial cells and the expression of relevant proteins in these cells, thus promoting the occurrence and development of KOA.