Clinicopathological correlation of Krüppel-like factor 5 and matrix metalloproteinase-9 expression and cartilage degeneration in human osteoarthritis

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.

Overcoming the Dependence on Animal Models for Osteoarthritis Therapeutics - The Promises and Prospects of In Vitro Models

Osteoarthritis (OA) is a musculoskeletal disease characterized by progressive degeneration of osteochondral tissues. Current treatment is restricted to the reduction of pain and loss of function of the joint. To better comprehend the OA pathophysiological conditions, several models are employed, however; there is no consensus on a suitable model. In this review, different in vitro models being developed for possible therapeutic intervention of OA are outlined. Herein, various in vitro OA models starting from 2D model, co-culture model, 3D models, dynamic culture model to advanced technologies-based models such as 3D bioprinting, bioassembly, organoids, and organ-on-chip-based models are discussed with their advantages and disadvantages. Besides, different growth factors, cytokines, and chemicals being utilized for induction of OA condition are reviewed in detail. Furthermore, there is focus on scrutinizing different molecular and possible therapeutic targets for better understanding the mechanisms and OA therapeutics. Finally, the underlying challenges associated with in vitro models are discussed followed by future prospective. Taken together, a comprehensive overview of in vitro OA models, factors to induce OA-like conditions, and intricate molecular targets with the potential to develop personalized osteoarthritis therapeutics in the future with clinical translation is provided.

Transcription factor Krüppel-like factor 5-regulated N-myc downstream-regulated gene 2 reduces IL-1β-induced chondrocyte inflammatory injury and extracellular matrix degradation

Previous research has identified N-myc downstream-regulated gene 2 (NDRG2) as one of the differentially expressed genes common to rat models of osteoarthritis (OA) and human OA. The purpose of this study was to investigate the role of NDRG2 in OA. In this study, an in vitro OA model was constructed by challenging ATDC5 chondrocytes with 10 ng/ml IL-1β. After transfection of pcDNA3.1(+)/NDRG2, qPCR and western blot were performed to assay NDRG2 expression. The analyses of cell viability, apoptosis and inflammatory molecule expression were employed respectively by CCK-8, TUNEL and ELISA. The protein expression related to apoptosis, inflammation or extracellular matrix (ECM) degradation was detected by western blot. The binding of Krüppel-like factor 5 (KLF5) to NDRG2 promoter was verified by means of dual-luciferase reporter assay. After overexpression of both NDRG2 and KLF5 in IL-1β-stimulated ATDC5 chondrocytes, corresponding assays were performed to examine cell viability, apoptosis, inflammatory response and ECM degradation. In ATDC5 chondrocytes challenged with IL-1β, NDRG2 expression was much lower than that in the control group, whereas it’s overexpression helped restored cell viability and reduce cell apoptosis, inflammatory response and ECM degradation. It was also observed that KLF5 expression was decreased in IL-1β-stimulated ATDC5 chondrocytes, and that KLF5 bound to the NDRG2 promoter. Importantly, overexpressing KLF5 could reverse the protective effect of NDRG2 overexpression on IL-1β-stimulated ATDC5. Overall, NDRG2 could be transcriptionally regulated by transcription factor KLF5 and may play a protective role against chondrocyte the inflammatory response and ECM degradation in OA.

Kruppel-like factor 4 upregulates matrix metalloproteinase 13 expression in chondrocytes via mRNA stabilization

Matrix metalloproteinase 13 (MMP13) is indispensable for normal skeletal development and is also a principal proteinase responsible for articular joint pathologies. MMP13 mRNA level needs to be tightly regulated in both positive and negative manners to achieve normal development and also to prevent joint destruction. We showed previously that Kruppel-like factor 4 (KLF4) strongly induces the expression of members of the MMP family of genes including that for MMP13 in cultured chondrocytes. Through expression-based screening of approximately 400 compounds, we identified several that efficiently downregulated MMP13 gene expression induced by KLF4. Compounds grouped as topoisomerase inhibitors (transcriptional inhibitors) downregulated MMP13 expression levels, which proved the validity of our screening method. In this screening, trichostatin A (TSA) was identified as one of the most potent repressors. Mechanistically, increased MMP13 mRNA levels induced by KLF4 were not mainly caused by increased rates of RNA polymerase II-mediated MMP13 transcription, but arose from escaping mRNA decay. TSA treatment almost completely blunted the effect of KLF4. Importantly, KLF4 was detected in chondrocytes at the joint destruction sites in a rodent model of osteoarthritis. Our results partially explain how KLF4 regulates numerous proteinase gene expressions simultaneously in chondrocytes. Also, these observations suggest that modulation of KLF4 activity or expression could be a novel therapeutic target for osteoarthritis.

Effects of Tribulus terrestris on monosodium iodoacetate‑induced osteoarthritis pain in rats

Tribulus terrestris L. (T. terrestris) has been used as a traditional medicine for the treatment of diuretic, lithontriptic, edema and urinary infections. Previous studies have indicated that it is effective in improving inflammation by regulating tumor necrosis factor‑α (TNF)‑α, interleukin (IL)‑6, IL‑10, nitric oxide (NO) and cyclooxygenase (COX)‑2. However, the effects and mechanism of action of T. terrestris on osteoarthritis (OA) remain unknown. Therefore, the present study aimed to evaluate the effects of the ethanolic extract of T. terrestris (ETT) in a monosodium iodoacetate (MIA)‑induced OA animal model. OA was induced in LEW/SSNHSD rats by intra‑articular injection of MIA. Morphometric changes and parameters of the tibial trabecular bone were determined using micro‑computed tomography. The molecular mechanisms of ETT in OA were investigated using reverse transcription‑polymerase chain reaction, western blotting and gelatin zymogram analysis. Treatment with ETT attenuated MIA‑induced OA, and this effect was mediated by the downregulation of NO synthase 2, COX‑2, TNF‑α and IL‑6. Furthermore, the ETT‑mediated attenuation of OA was also dependent on the expression of matrix metalloproteinases‑2 and ‑9. The results of the current study indicate that further evaluation of the mechanisms underlying the attenuation of MIA‑induced OA by ETT are required, and may support the development of ETT as a potential therapeutic agent for the treatment of inflammatory diseases such as OA.

Recent findings on the role of gelatinases (matrix metalloproteinase-2 and -9) in osteoarthritis

Several studies dealing with the pathomechanisms of OA refer to MMP-1, -3, -7, -8, and -13 whereas a smaller number of investigations have pointed out the pathogenic role of gelatinases in OA. These gelatinases are best known for their involvement in pulmonary, myocardial, and neoplastic disease but they are emerging as important proteases implicated in the OA progression. This paper highlights the role of the gelatinases as emerging factors in OA pathogenesis through the regulation of subchondral bone resorption and microvascular invasion. The most significant new findings over the last year that add to our knowledge of the activity of these proteins in OA have been reported.