Advances on biological functions of exosomal non-coding RNAs in osteoarthritis

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

Paeoniflorin, the Main Monomer Component of Paeonia lactiflora, Exhibits Anti-inflammatory Properties in Osteoarthritis Synovial Inflammation

OBJECTIVE

To explore the mechanism of paeoniflorin (PF) on osteoarthritis (OA) synovial inflammation from network pharmacology to experimental pharmacology.

METHODS

Targets of OA were constructed by detecting the database of network database platforms (Therapeutic Target database, DrugBank and GeneCards), and the targets of PF were constructed by PubChem and Herbal Ingredients' Targets database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of these co-targeted genes were conducted via Database for Annotation, Visualization, and Integrated Discovery (DAVID) database, and protein-protein interaction (PPI) networks were conducted via the search tool for the retrieval of interacting genes (STRING) database. Cell counting kit-8 (CCK-8) assay was performed to assess the potential toxicity of PF on human OA fibroblast-like synoviocytes (FLS), quantitative real-time polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA) and Western blot were used to verify the potential mechanism of PF in synovial inflammation.

RESULTS

Twenty-six co-targeted genes were identified. GO enrichment results showed that these co-targeted genes were most likely localized in the cytoplasm, and the biological processes mainly involved 'cellular response to hypoxia' 'lipopolysaccharide (LPS)-mediated signaling pathway' and 'positive regulation of gene expression'. KEGG pathway analysis indicated that these co-targeted genes may function through pathways associated with 'hypoxia-inducible factor-1 (HIF-1) signaling pathway' and 'tumor-necrosis factor (TNF) signaling pathway'. The PPI network showed that the top 3 hub genes were TP53, TNF, and CASP3. Molecular docking results showed that PF was well docking with TNF. CCK-8 showed no potential toxicity of 10, 20 and 50 µmol/L PF on human OA FLS. And PF significantly decreased the expression levels of interleukin-1 β, interleukin-6, TNF-α matrix metalloproteinase 13 (MMP13), and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) and TNF-α in LPS-induced OA FLS.

CONCLUSION

PF exhibited potent anti-inflammatory effect in OA synovial inflammation.

CircMIRLET7BHG, upregulated in an m6A-dependent manner, induces the nasal epithelial barrier dysfunction in allergic rhinitis pathogenesis

OBJECTIVE

Allergic rhinitis (AR) remains a frequent aspiratory allergic inflammatory disorder with a high incidence. Circular RNAs (circRNAs) have been revealed to participate in the pathogenesis of AR. This study investigated the biological function of circMIRLET7BHG (hsa_circ_0008668) in AR progression.

METHODS

Ovalbumin (OVA)-exposed human nasal epithelial cell line (HNEpC) and mice were adopted as the in vitro and in vivo models of AR. Immunofluorescence staining was used to determine epithelial tight junction protein expression. Target molecule levels were assessed by RT-qPCR and Western blotting. Localization of circMIRLET7BHG and IGF2BP1 was observed by RNA-FISH and immunofluorescence. Epithelial barrier damage was determined by transepithelial electrical resistance and fluorescein isothiocyanate-dextran (FD4) permeability. Serum concentrations of IgE, sIgE, IFN-γ, IL-4, and IL-5 were detected by ELISA. Apoptosis, pathological changes, and eosinophil infiltration in nasal mucosa tissues were evaluated by TUNEL, H&E, and Sirius red staining, respectively. Molecular mechanism was analyzed by RNA pull-down, RIP, and MeRIP assays.

RESULTS

An increased expression of circMIRLET7BHG was found in AR patients and experimental models. Down-regulation of circMIRLET7BHG attenuated OVA-induced allergic symptoms via relieving epithelial thicknesses, eosinophil infiltration, apoptosis, and inflammatory response in mice. Subsequently, circMIRLET7BHG deficiency prevented OVA-induced epithelial barrier dysfunction by reducing epithelial permeability, and inhibiting tight junction proteins. Mechanistically, methyltransferase-like 3 (METTL3) enhanced circMIRLET7BHG expression via m6A methylation, which enhanced ADAM10 mRNA stability via interaction with IGF2BP1.

CONCLUSION

METTL3-mediated m6A modification increased circMIRLET7BHG expression that consequently raised ADAM10 mRNA stability via interplay with IGF2BP1, thereby promoting AR by inducing epithelial barrier dysfunction.

A review on circular RNAs and bacterial infections

Bacterial infections and related diseases have been a major burden on social public health and economic stability around the world. However, the effective diagnostic methods and therapeutic approaches to treat bacterial infections are still limited. As a group of non-coding RNA, circular RNAs (circRNAs) that were expressed specifically in host cells and played a key regulatory role have the potential to be of diagnostic and therapeutic value. In this review, we systematically summarize the role of circRNAs in common bacterial infections and their potential roles as diagnostic markers and therapeutic targets.

Immunomodulatory potential of secretome from cartilage cells and mesenchymal stromal cells in an arthritic context: From predictive fiction toward reality

The purpose of the present study is to predict by bioinformatics the activity of the extracellular vesicle (EV)-embedded micro RNA (miRNAs) secreted by cartilage cells (CCs), adipose tissue-derived- (ASCs), and bone marrow-derived stem cells (BMSCs) and verify their immunomodulatory potential supporting our bioinformatics findings to optimize the autologous cell-based therapeutic strategies for osteoarthritis (OA) management. Cells were isolated from surgical waste tissues of three patients who underwent total hip replacement, expanded and the EVs were collected. The expression of EV-embedded miRNA was evaluated with the QuantStudio 12 K Flex OpenArray^® platform. Mientournet and ingenuity pathway analysis (IPA) were used for validated target prediction analysis and to identify miRNAs involved in OA and inflammation. Cells shared the expression of 325 miRNAs embedded in EVs and differed for the expression of a small number of them. Mienturnet revealed no results for miRNAs selectively expressed by ASCs, whereas miRNA expressed by CCs and BMSCs were putatively involved in the modulation of cell cycle, senescence, apoptosis, Wingless and Int-1 (Wnt), transforming growth factor beta (TGFβ), vascular endothelial growth factor (VEGF), Notch, Hippo, tumor necrosis factor alpha (TNFα), interleukin 1 beta (IL-1β), insulin like growth factor 1 (IGF-1), RUNX family transcription factor 2 (RUNX2), and endochondral ossification pathways. Cartilage homeostasis, macrophages and T cells activity and inflammatory mediators were identified by IPA as targets of the miRNAs found in all the cell populations. Co-culture tests on macrophages and T cells confirmed the immuno-modulatory ability of CCs, ASCs, and BMSCs. The study findings support the rationale behind the use of cell-based therapy for the treatment of OA.