CircGCN1L1 promotes synoviocyte proliferation and chondrocyte apoptosis by targeting miR-330-3p and TNF-α in TMJ osteoarthritis

Altered expression of circular RNAs (circRNAs) has been identified in various human diseases. In this study, we investigated whether circRNAs function as competing endogenous RNAs to regulate the pathological process of temporomandibular joint osteoarthritis (TMJOA). High-throughput sequencing of mRNA (RNA seq) was performed to detect the expression of circRNAs in TMJOA and control synovial tissues isolated from humans. The differentially upregulated circGCN1L1 (hsa_circ_0000448) in synoviocyte was validated in vitro and in vivo. Here we demonstrate the interactions between circGCN1L1 and both miR-330-3p and tumor necrosis factor-α (TNF-α) through bioinformatics predictions, luciferase report assays, and fluorescence in situ hybridization. mRNA expression profiles of TNF-α-stimulated synoviocyte showed that circGCN1L1 and p65 expressions were upregulated by TNF-α. Moreover, miR-330-3p was negatively correlated with TNF-α secretion. Further, we found that miR-330-3p directly targeted TNF and restrained the production of matrix-degrading enzymes (MMP3, MMP13, and ADAMTS4). Mechanistic studies unveiled that circGCN1L1 in TMJOA synovial tissues and cells may be associated with condylar chondrocyte apoptosis and synoviocyte hyperplasia. Moreover, intra-articular injection of shcircGCN1L1 alleviated TMJOA progression in rat models. Altogether, we elucidated the important roles of a novel circRNA, namely, circGCN1L1, which induced inflammation in TMJ synoviocytes and decreased anabolism of the extracellular matrix (ECM) through miR-330-3p and TNF-α gene. This circRNA may represent a potentially effective therapeutic strategy against TMJOA progression at an early stage.