RNA sequencing reveals the circular RNA expression profiles of osteoarthritic synovium.

The role of circular RNAs (circRNAs) in regulating cartilage homeostasis in osteoarthritis (OA) has been reported. However, the regulatory mechanisms of circRNAs in OA synovium remains basically unidentified. The current study intended to divulge the expression profile of circRNAs in OA synovium and investigate the possible molecular mechanisms of circRNAs in synovitis in OA through an integrated bioinformatics analysis. A total of 35 synovium samples were collected, including 17 from patients with knee OA and 18 from controls. circRNA sequencing was then carried out on five OA synovium samples as well as five controls to explore the expression pattern of the circRNAs. Real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was done to confirm the manifestation levels of six differentially expressed circRNAs. Gene Ontology (GO) as well as Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were done for differentially expressed circRNAs using the DAVID database to annotate the functions. The circRNA-miRNA coexpression network was then created to estimate the probable molecular regulatory mechanisms of specifically expressed circRNAs in OA synovium. Total of 122 circRNAs were found to be differentially expressed in OA synovium through RNA sequencing. The expressions of five downregulated circRNAs as well as an upregulated circRNA were confirmed through the use of qRT-PCR. The circRNA-miRNA network was created to annotate the probable molecular regulatory mechanisms of specifically expressed circRNAs. Our outcomes revealed that circRNAs might be incorporated in the initiation as well as development of OA synovitis and might have prospective importance in OA diagnosis and therapy.

Xiang S ，Li Z ，Bian Y ，Weng X ... -  《-》

Circular RNA expression profile of articular chondrocytes in an IL-1β-induced mouse model of osteoarthritis.

Osteoarthritis (OA) is a widely prevalent degenerative joint disease characterized by articular cartilage degradation and joint inflammation. The pathogenesis of OA remains unclear, leading to a lack of effective treatment. Previous studies have reported that circular RNAs (circRNAs) are involved in the development of various diseases. However, the function of circRNAs and their roles in OA is largely unknown. Therefore, we aimed to investigate changes in circRNA expression and predict their functions in OA by using bioinformatics analysis. An OA model was established in mouse articular chondrocytes (MACs) treated by interleukin-1β (IL-1β), and then the circRNA profile was screened by Next Generation Sequencing. By comparing circRNA expression in IL-1β- treated MACs and normal controls, differentially expressed circRNAs were identified during OA pathogenesis, and differential expression levels of selected circRNAs were validated by qRT-PCR. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were employed to predict the functions of these circRNAs. Because circRNAs can act as "miRNA sponges", we also constructed a circRNA-miRNA network to predict their functions. A total of 255 circRNAs were found to be differentially expressed in IL-1β-treated MACs (p≤0.05; fold-change≥2) from the expression of the normal controls. Among them, 119 circRNAs were significantly up-regulated, and the other 136 were down-regulated. Seven circRNAs were randomly selected to verify the reliability of these profiles by quantitative qRT-PCR. After obtaining the parental genes of differentially expressed circRNA, the top 30 enrichment GO entries and KEGG pathways were annotated. Then, two significantly differentially expressed circRNAs (mmu-circRNA-30365 and mmu-circRNA-36866) were identified and selected for further analysis, meanwhile a circRNA-miRNA regulation network was created and the top five most likely functional-related target miRNAs of the circRNAs were collected. Although the exact mechanisms and biological functions of these circRNAs in the development of OA need further exploration, our findings do suggest that the differentially expressed circRNAs were involved in the pathogenesis of OA. Thus, our study brings us closer to understanding the pathogenic mechanisms and finding new molecular targets for the clinical treatment of osteoarthritis.

Zhou Z ，Du D ，Chen A ，Zhu L ... -  《-》

Screening for Differentially Expressed Circular RNAs in the Cartilage of Osteoarthritis Patients for Their Diagnostic Value.

Wang Y ，Wu C ，Zhang F ，Zhang Y ，Ren Z ，Lammi MJ ，Guo X ... -  《-》

Identification of changed expression of mRNAs and lncRNAs in osteoarthritic synovium by RNA-sequencing.

Long non-coding RNAs (lncRNAs) are recently reported to regulate the homeostasis of cartilage in osteoarthritis (OA), but their regulatory roles in OA synovium remain elusive. This study aimed to identify the differentially expressed mRNAs and lncRNAs in OA synovium and further explore the function of differentially expressed lncRNAs in OA progression through bioinformatics analysis. We started with RNA-sequencing in 5 OA synovium samples and 5 healthy controls to compare the expression of mRNAs and lncRNAs. GO analysis and KEGG pathway analysis were performed to annotate the function of differentially expressed mRNAs. Then real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was admitted in 17 osteoarthritic synovium and 18 healthy controls to confirm the changes of the expression of the selected lncRNAs. LncRNA-mRNA co-expression network was constructed to predict the potential molecular regulatory mechanisms of specifically expressed lncRNAs in OA synovium. 384 mRNAs and 17 lncRNAs were detected to be differentially expressed in OA synovium. The expressions of 4 lncRNAs were confirmed by qRT-PCR. We found the differentially expression lncRNAs could potentially regulate OA progression through pathways regarding to immune response through the lncRNA-mRNA network and further annotation for co-expression mRNAs. Our results indicated that lncRNAs may play key roles in OA synovitis and may have potential value in OA diagnosis.

Xiang S ，Li Z ，Bian Y ，Weng X ... -  《-》

RNA sequencing reveals the circular RNA expression profiles of the infrapatellar fat pad/synovium unit.

The infrapatellar fat pad (IPFP) and synovium are reported to act as a functional unit, with emerging roles in the pathophysiology of knee osteoarthritis (KOA). Circular RNAs (circRNAs) are involved in the pathogenesis of KOA, especially in cartilage homeostasis regulation. Nevertheless, the regulatory mechanisms of circRNAs in the KOA IPFP/synovium unit remain to be elucidated. Therefore, the current study aimed to investigate alterations in the expression of circRNAs and predict their functions in the KOA IPFP/synovium unit using bioinformatics analysis. In brief, 6 synovium and IPFP specimens were collected, in which 3 from patients with KOA and 3 from controls. Then, circRNA sequencing was conducted on 2 KOA synovium and IPFP specimens as well as 1 control to investigate the expression profiles of circRNAs. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome signaling pathway analyses were employed to predict the functions of the differentially expressed circRNAs. Based on the miRNA sponge theory, we constructed a circRNA-miRNA network to predict the molecular regulatory mechanism of these circRNAs. Venn analysis was performed to confirm the circRNAs and miRNAs expressed in both synovium and IPFP. Real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was also used to validate the expression levels of circRNAs that were co-expressed in both synovium and IPFP. A total of 65 and 72 circRNAs were differentially expressed in KOA synovium and IPFP, respectively (fold change ≥2, P<0.05). After obtaining the parental genes of differentially expressed circRNAs, the top 10 enrichment GO entries, KEGG pathways, and Reactome pathways were annotated. Furthermore, hsa_circ_0005265 was found to be down-regulated in both synovium and IPFP, which was validated by qRT-PCR. The circRNA-miRNA network was created to annotate the probable regulatory mechanisms of the differentially expressed circRNAs, which consequently confirmed 2 target miRNAs (hsa-miR-6769b-5p and hsa-miR-1249-5p) associated with hsa_circ_0005265 in both synovium and IPFP. Our outcomes bring us closer to understanding the potential mechanism of the IPFP/synovium unit in the progression of KOA and finding new molecular targets for KOA therapy.

Jiang T ，Lu Y ，Chen Z ，Lin X ，Zhang J ，Shan J ，Lu C ，Zhao C ，Xu X ，Liu W ... -  《-》