Global Transcriptomic Study of Circular-RNA Expression Profile in Osteoclasts Infected by Intracellular Staphylococcus aureus.

Osteomyelitis is difficult to cure, and the rapidly rising morbidity is a thorny problem accompanied by a large number of joint replacement applications. Staphylococcus aureus is the main pathogen of osteomyelitis. Circular RNAs (circRNAs), as emerging noncoding RNAs, play important roles in multiple physiopathological processes which could provide novel insights into osteomyelitis. However, little is known about the roles of circRNAs in the pathogenesis of osteomyelitis. Osteoclasts, considered bone sentinels, are the resident macrophages in bone and may play the immune defense roles in osteomyelitis. It has been reported that S. aureus can survive in osteoclasts, but the function of osteoclast circRNAs in response to intracellular S. aureus infection remains unclear. In this study, we investigated the profile of circRNAs in osteoclasts infected by intracellular S. aureus through high-throughput RNA sequencing. In total, 24 upregulated and 62 downregulated differentially expressed circRNAs were identified and subsequently analyzed to demonstrate their potential functions. On this basis, three circRNAs (chr4:130718154-130728164+, chr8:77409548-77413627-, and chr1:190871592-190899571-) were confirmed as potential novel biomarkers for the diagnosis of osteomyelitis through the murine model of osteomyelitis. Most importantly, we verified that the circRNA chr4:130718154-130728164+ named circPum1 could regulate the host autophagy to affect the intracellular infection of S. aureus through miR-767. In addition, circPum1 could serve as a promising serum biomarker in osteomyelitis patients caused by S. aureus infection. Taken together, this study provided the first global transcriptomic profile analysis of circRNAs in osteoclasts infected by intracellular S. aureus and first proposed a novel perspective for the pathogenesis and immunotherapy of S. aureus-induced osteomyelitis from the term of circRNAs.

Mechanisms of folate metabolism-related substances affecting Staphylococcus aureus infection.

Staphylococcus aureus (S. aureus) is one of the critical clinical pathogens which can cause multiple diseases ranging from skin infections to fatal sepsis. S. aureus is generally considered to be an extracellular pathogen. However, more and more evidence has shown that S. aureus can survive inside various cells. Folate plays an essential role in multiple life activities, including the conversion of serine and glycine, the remethylation of homocysteine to methionine, and the de novo synthesis of purine /dTMP, et al. More and more studies reported that S. aureus intracellular infection requires the involvement of folate metabolism. This review focused on the mechanisms of folate metabolism and related substances affecting S. aureus infection. Loss of tetrahydrofolic acid (THF)-dependent dTMP directly inhibits the nucleotide synthesis pathway of the S. aureus due to pabA deficiency. Besides, trimethoprim-sulfamethoxazole (TMP/SMX), a potent antibiotic that treats S. aureus infections, interferes in the process of the folate mechanism and leads to the production of thymidine-dependent small-colony variants (TD-SCVs). In addition, S. aureus is resistant to lysostaphin in the presence of serine hydroxymethyltransferase (SHMT). We provide new insights for understanding the molecular pathogenesis of S. aureus infection.

Identification of the miRNA signature and key genes in colorectal cancer lymph node metastasis.

BACKGROUND: Because its metastasis to the lymph nodes are closely related to poor prognosis, miRNAs and mRNAs can serve as biomarkers for the diagnosis, prognosis, and therapy of colorectal cancer (CRC). This study aimed to identify novel gene signatures in the lymph node metastasis of CRC. METHODS: GSE56350, GSE70574, and GSE95109 datasets were downloaded from the Gene Expression Omnibus (GEO) database, while data from 569 colorectal cancer cases were also downloaded from The Cancer Genome Atlas (TCGA) database. Differentially expressed miRNAs (DE-miRNAs) were calculated using R programming language (Version 3.6.3), while gene ontology and enrichment analysis of target mRNAs were performed using FunRich ( http://www.funrich.org ). Furthermore, the mRNA-miRNA network was constructed using Cytoscape software (Version 3.8.0). Gene expression levels were verified using the GEO datasets. Similarly, quantitative real-time PCR (qPCR) was used to examine expression profiles from 20 paired non-metastatic and metastatic lymph node tissue samples obtained from patients with CRC. RESULTS: In total, five DE-miRNAs were selected, and 34 mRNAs were identified after filtering the results. Moreover, two key miRNAs (hsa-miR-99a, hsa-miR-100) and one gene (heparan sulfate-glucosamine 3-sulfotransferase 2 [HS3ST2]) were identified. The GEO datasets analysis and qPCR results showed that the expression of key miRNA and genes were consistent with that obtained from the bioinformatic analysis. A novel miRNA-mRNA network capable of predicting the prognosis and confirmed experimentally, hsa-miR-99a-HS3ST2-hsa-miR-100, was found after expression analysis in metastasized lymph node tissue from CRC samples. CONCLUSION: In summary, miRNAs and genes with potential as biomarkers were found and a novel miRNA-mRNA network was established for CRC lymph node metastasis by systematic bioinformatic analysis and experimental validation. This network may be used as a potential biomarker in the development of lymph node metastatic CRC.