Bioinformatic analysis of lncRNA-associated competing endogenous RNA regulatory networks in synovial tissue of temporomandibular joint osteoarthritis

Background: Temporomandibular joint osteoarthritis (TMJOA) is an end-stage disease that seriously affects the patients' quality of life. Molecular insights in advancing our understanding of TMJOA are the need of the hour. Methods: We performed RNA high-throughput sequencing and bioinformatics analysis of differentially expressed (DE) long non-coding RNA (lncRNAs), microRNAs (miRNAs), and messenger RNA (mRNAs) in human synovial TMJOA tissues. Firstly, synovium samples of TMJOA patients and non-TMJOA controls were collected for highthroughput sequencing of lncRNAs, miRNAs, and mRNAs. We then performed biological function analysis of the top 100 mRNAs with more than 2-fold differential expression, and their upstream regulated miRNAs and lncRNAs were predicted separately. Intersections between predicted miRNAs/lncRNAs and differentially expressed miRNAs/ lncRNAs were determined, respectively. Regulatory networks among the selected lncRNAs, miRNAs, and mRNAs were constructed. Finally, Western Blotting and reverse transcription-quantitative polymerase chain reaction (RTqPCR) were used to explore the function of selected lncRNA and mRNAs. Results: Our analysis showed that the only upregulated lncRNAxist, was involved in intracellular protein degradation, cartilage matrix degradation, and osteoclast differentiation through four regulatory axes: miR-1271-5p/ctsb, miR-365a-3p/mmp3, miR-199a-3p/fos, and miR-27b-3p/ miR-1271-5p/grb2. RT-qPCR results showed that xist expression increased in both TMJOA synovial tissue and inflammatory-stimulated synovial cells. Inhibition of xist could promote the proliferation of synovial cells upon inflammatory stimulation, and xist could positively regulate the expression of GRB2. Targeting GRB2 could inhibit the expression of matrix degrading enzymes in synovial cells, thereby attenuating the inflammatory environment. Conclusion: Given the current lack of reports of lncRNA regulation in TMJOA synovitis, our results revealed that xist was significantly differentially expressed in human synovial TMJOA and could regulate the expression of GRB2, which may play a role in the progression of TMJOA.