CircATRNL1 protects against osteoarthritis by targeting miR-153-3p and KLF5

Krüppel-like factors family in health and disease

Krüppel-like factors (KLFs) are a family of basic transcription factors with three conserved Cys2/His2 zinc finger domains located in their C-terminal regions. It is acknowledged that KLFs exert complicated effects on cell proliferation, differentiation, survival, and responses to stimuli. Dysregulation of KLFs is associated with a range of diseases including cardiovascular disorders, metabolic diseases, autoimmune conditions, cancer, and neurodegenerative diseases. Their multidimensional roles in modulating critical pathways underscore the significance in both physiological and pathological contexts. Recent research also emphasizes their crucial involvement and complex interplay in the skeletal system. Despite the substantial progress in understanding KLFs and their roles in various cellular processes, several research gaps remain. Here, we elucidated the multifaceted capabilities of KLFs on body health and diseases via various compliable signaling pathways. The associations between KLFs and cellular energy metabolism and epigenetic modification during bone reconstruction have also been summarized. This review helps us better understand the coupling effects and their pivotal functions in multiple systems and detailed mechanisms of bone remodeling and develop potential therapeutic strategies for the clinical treatment of pathological diseases by targeting the KLF family.

Inhibition of LINC00958 hinders the progression of osteoarthritis through regulation of the miR-214-3p/FOXM1 axis

OBJECTIVE

We investigated the impact of the long noncoding RNA LINC00958 on cellular activity and oxidative stress in osteoarthritis (OA).

METHODS

We performed bioinformatics analysis via StarBase and luciferase reporter assays to predict and validate the interactions between LINC00958 and miR-214-3p and between miR-214-3p and FOXM1. The expression levels of LINC00958, miR-214-3p, and FOXM1 were measured by qRT-PCR and western blotting. To assess effects on CHON-001 cells, we performed MTT proliferation assays, evaluated cytotoxicity with a lactate dehydrogenase (LDH) assay, and examined apoptosis through flow cytometry. Additionally, we measured the levels of apoptosis-related proteins, including BAX and BCL2, using western blotting. The secretion of inflammatory cytokines (IL-6, IL-8, and TNF-α) was measured using ELISA.

RESULTS

Our findings confirmed that LINC00958 is a direct target of miR-214-3p. LINC00958 expression was upregulated but miR-214-3p expression was downregulated in both OA cells and IL-1β-stimulated CHON-001 cells compared to the corresponding control cells. Remarkably, miR-214-3p expression was further reduced after miR-214-3p inhibitor treatment but increased following LINC00958-siRNA stimulation. Silencing LINC00958 significantly decreased its expression, and this effect was reversed by miR-214-3p inhibitor treatment. Notably, LINC00958-siRNA transfection alleviated the IL-1β-induced inflammatory response, as evidenced by the increased cell viability, reduced LDH release, suppression of apoptosis, downregulated BAX expression, and elevated BCL2 levels. Moreover, LINC00958 silencing led to reduced secretion of inflammatory factors from IL-1β-stimulated CHON-001 cells. The opposite results were observed in the miR-214-3p inhibitor-transfected groups. Furthermore, in CHON-001 cells, miR-214-3p directly targeted FOXM1 and negatively regulated its expression.

CONCLUSION

Our findings suggest that downregulating LINC00958 mitigates IL-1β-induced injury in CHON-001 cells through the miR-214-3p/FOXM1 axis. These results imply that LINC00958 plays a role in OA development and may be a valuable therapeutic target for OA.

CircRNAs in osteoarthritis: research status and prospect

Osteoarthritis (OA) is the most common joint disease globally, and its progression is irreversible. The mechanism of osteoarthritis is not fully understood. Research on the molecular biological mechanism of OA is deepening, among which epigenetics, especially noncoding RNA, is an emerging hotspot. CircRNA is a unique circular noncoding RNA not degraded by RNase R, so it is a possible clinical target and biomarker. Many studies have found that circRNAs play an essential role in the progression of OA, including extracellular matrix metabolism, autophagy, apoptosis, the proliferation of chondrocytes, inflammation, oxidative stress, cartilage development, and chondrogenic differentiation. Differential expression of circRNAs was also observed in the synovium and subchondral bone in the OA joint. In terms of mechanism, existing studies have mainly found that circRNA adsorbs miRNA through the ceRNA mechanism, and a few studies have found that circRNA can serve as a scaffold for protein reactions. In terms of clinical transformation, circRNAs are considered promising biomarkers, but no large cohort has tested their diagnostic value. Meanwhile, some studies have used circRNAs loaded in extracellular vesicles for OA precision medicine. However, there are still many problems to be solved in the research, such as the role of circRNA in different OA stages or OA subtypes, the construction of animal models of circRNA knockout, and more research on the mechanism of circRNA. In general, circRNAs have a regulatory role in OA and have particular clinical potential, but further studies are needed in the future.

LncRNA HAGLR silencing inhibits IL-1β-induced chondrocytes inflammatory injury via miR-130a-3p/JAK1 axis

BACKGROUND

Osteoarthritis (OA), the most common form of arthritis, is accompanied by destruction of articular cartilage, development of osteophyte and sclerosis of subchondral bone. This study aims to explore whether lncRNA HAGLR can play a role in OA, and further clarify the potential mechanism.

MATERIAL AND METHODS

StarBase and luciferase reporter assay were applied for predicting and confirming the interaction between lncRNA HAGLR, miR-130a-3p and JAK1. The levels of lncRNA HAGLR and miR-130a-3p were analyzed using quantitative reverse transcription PCR (qRT-PCR). The proliferation, cytotoxicity and apoptosis of CHON-001 cells were evaluated by MTT, lactate dehydrogenase assay (LDH) and Flow cytometry (FCM) analysis, respectively. Moreover, expression of cleaved Caspase3 protein were determined by Western blot assay. The release of inflammatory factors (TNF-α, IL-8, and IL-6) was detected by ELISA.

RESULTS

lncRNA HAGLR directly targets miR-130a-3p. Level of lncRNA HAGLR was substantially higher and miR-130a-3p level was memorably lower in IL-1β stimulated CHON-001 cells than that in Control group. Furthermore, lncRNA HAGLR silencing alleviated IL-1β induce chondrocyte inflammatory injury, as evidenced by increased cell viability, reduced LDH release, decreased apoptotic cells, inhibited cleaved-Caspase3 expression, and reduced secretion of secretion of inflammatory factors. However, miR-130a-3p-inhibitor reversed these findings. We also found miR-130a-3p directly targeted JAK1 and negatively regulated JAK1 expression in CHON-001 cells. In addition, JAK1-plasmid reversed the effects of miR-130a-3p mimic on IL-1β-induced chondrocytes inflammatory injury.

CONCLUSION

Silencing of lncRNA HAGLR alleviated IL-1β-stimulated CHON-001 cells injury through miR-130a-3p/JAK1 axis, revealing lncRNA HAGLR may be a valuable therapeutic target for OA therapy.

miR-124-3p sabotages lncRNA MALAT1 stability to repress chondrocyte pyroptosis and relieve cartilage injury in osteoarthritis

Background

Osteoarthritis (OA) is a prevalent inflammatory joint disorder. microRNAs (miRNAs) are increasingly involved in OA.

Aim

Our study is proposed to clarify the role of miR-124-3p in chondrocyte pyroptosis and cartilage injury in OA.

Methods

OA mouse model was established via the treatment of destabilization of the medial meniscus (DMM), and the in vitro cell model was also established as mouse chondrocytes were induced by lipopolysaccharide (LPS). Mouse cartilage injury was assessed using safranin-O-fast green staining, hematoxylin–eosin staining, and OARSI grading method. Expressions of miR-124-3p, MALAT1, KLF5, and CXCL11 were determined. Cartilage injury (MMP-13, osteocalcin), inflammation (IL-6, IL-2, TNF-, IL-1β, and IL-18)- and pyroptosis-related factors (Cleaved Caspase-1 and GSDMD-N) levels were detected. Mechanically, MALAT1 subcellular localization was confirmed. The binding relationships of miR-124-3p and MALAT1 and MALAT1 and KLF5 were verified. MALAT1 half-life period was detected. Then, miR-124-3p was overexpressed using agomiR-124-3p to perform the rescue experiments with oe-MALAT1 or oe-CXCL11.

Results

miR-124-3p was downregulated in DMM mice and LPS-induced chondrocytes where cartilage injury, and increased levels of inflammation- and pyroptosis-related factors were found. miR-124-3p overexpression relieved cartilage injury and repressed chondrocyte pyroptosis. miR-124-3p bounds to MALAT1 to downregulate its stability and expression, and MALAT1 bounds to KLF5 to enhance CXCL11 transcription. Overexpression of MALAT1 or CXCL11 annulled the repressive function of miR-124-3p in chondrocyte pyroptosis.

Conclusion

miR-124-3p reduced MALAT1 stability and inhibited the binding of MALAT1 and KLF5 to downregulate CXCL11, thereby suppressing chondrocyte pyroptosis and cartilage injury in OA.

CircCDK14 ameliorates interleukin-1β-induced chondrocyte damage by the miR-1183/KLF5 pathway in osteoarthritis

BACKGROUND

The pathogenesis of osteoarthritis (OA), an endemic and debilitating disease, remains unclear. The study aimed to reveal the role of circular RNA cyclin dependent kinase 14 (circCDK14) in OA development and the underlying mechanism.

METHODS

Human chondrocytes were stimulated by 10 ng/mL interleukin-1β (IL-1β) to mimic OA cell model. The RNA expression of circCDK14, microRNA-1183 (miR-1183) and kruppel like factor 5 (KLF5) was checked through quantitative real-time polymerase chain reaction. Western blot was employed to detect protein expression. Cell viability, proliferation and apoptosis were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine and flow cytometry analysis, respectively. Starbase online database was performed to identify the interaction between miR-1183 and circCDK14 or KLF5. Exosomes were isolated by differential centrifugation and identified by transmission electron microscopy, nanoparticle tracking analysis and western blot analysis.

RESULTS

CircCDK14 and KLF5 expression were significantly decreased, while miR-1183 was increased in OA cartilage tissues and IL-1β-treated chondrocytes in comparison with controls. CircCDK14 overexpression attenuated the inhibitory effect of IL-1β treatment on cell proliferation and the promoting effects on cell apoptosis and extracellular matrix degradation. Additionally, miR-1183 was targeted by circCDK14, and miR-1183 mimics reversed circCDK14-mediated actions in IL-1β-treated chondrocytes. The knockdown of KLF5, a target mRNA of miR-1183, also rescued the effects of miR-1183 inhibitors in IL-1β-induced chondrocytes. Moreover, circCDK14 could induce KLF5 expression by interacting with miR-1183. Further, exosomal circCDK14 had a high diagnostic value in OA.

CONCLUSION

CircCDK14 reintroduction assuaged IL-1β-caused chondrocyte damage by the miR-1183/KLF5 pathway, providing a diagnostic biomarker for OA.

CircATRNL1 and circZNF608 Inhibit Ovarian Cancer by Sequestering miR-152-5p and Encoding Protein

Background: CircRNAs have been found to be involved in the pathogenesis of various diseases. We aimed to explore the roles of circRNAs in ovarian cancer.

Methods: The expression levels of circRNAs in ovarian cancer and normal ovarian tissues were analyzed using RNA sequencing. Fluorescent in situ hybridization (FISH), proliferation assays and transwell assays were used to assess the effects of circRNAs on ovarian cancer.

Results: CircATRNL1 and circZNF608 were downregulated in 20 ovarian cancer tissues compared to normal tissues. CircATRNL1 and circZNF608 are mainly located in the cytoplasm of ovarian cancer cells, and circATRNL1 is a highly conserved circRNA. The overexpression of circATRNL1 and circZNF608 inhibits the proliferation and invasion of ovarian cancer cells. We predicted miRNA–circRNA interactions for circZNF608 and circATRNL1 and obtained 63 interactions. However, a luciferase reporter assay showed that only miR-152-5p was sequestered by circZNF608. Bioinformatics analysis and experiments indicated that circATRNL1 contains an internal ribosome entry site and an open reading frame encoding a 131 aa protein.

Conclusion: In conclusion, circATRNL1 and circZNF608 are two downregulated circRNAs in ovarian cancer and work as tumor suppressors. CircZNF608 may exert antitumor activity in ovarian cancer by binding miR-152-5p, and circATRNL1 may encode a 131 aa protein.

Krüppel-like factors in bone biology

The krüppel-like factor (KLF) family is a group of zinc finger transcription factors and contributes to different cellular processes such as differentiation, proliferation, migration, and apoptosis. While different studies show the roles of this family in skeletal development-specifically in chondrocyte and osteocyte development and bone homeostasis-there are few reviews summarizing their importance. To fill this gap, this review discusses current knowledge on different functions of the KLF family during skeletal development, including their roles in stem cell maintenance and differentiation, cell apoptosis, and cell cycle. To understand the importance of the KLF family, we also review genotype-phenotype correlations in different animal models. We also discuss how KLF proteins function through different signaling pathways and display their paramount importance in skeletal development. To highlight their roles in cartilage- or bone-related cells, we also use single-cell RNA sequencing publicly available data on mouse hindlimb. We also challenge our knowledge of how the KLF family is epigenetically regulated-e.g., using DNA methylation, histone modifications, and noncoding RNAs-during chondrocyte and osteocyte development.

Circular RNA triple functional domain promotes osteoarthritis' development by modulating the microRNA-136-5p/Nicotinamide phosphoribosyltransferase axis

Numerous studies have affirmed the participation of circular RNA (circRNA) in osteoarthritis (OA)’ development. Previous studies have exposed the elevation of the circRNA triple functional domain (TRIO) in OA, while the molecular mechanism of its effect on OA remains ambiguous. During the study, it was discovered the up-regulation of circTRIO in OA rats and interleukin-1β-treated chondrocytes. Knockdown circTRIO facilitates chondrocyte viability, but suppresses the inflammation, the apoptosis, and matrix metalloproteinases (MMP)-3 and MMP-13 expression, whereas up-regulation aggravates OA. The effect of up-regulation or under-expression of circTRIO on chondrocytes was reversed via the knockdown of Nicotinamide phosphoribosyltransferase (NAMPT) or microRNA (miR)-136-5p separately. Mechanically speaking, circTRIO competitively adsorbing miR-136-5p to target NAMPT influences OA. Briefly, the results of this study inform that the circTRIO/miR-136-5p/NAMPT axis is momentous in OA progression and is supposed to be a promising therapeutic target for some time.