Activity Of Chondrocytes Research Articles

Charge‐Guided Cartilage‐Penetrating Micro/Nanocarriers That Inhibit Piezo1 and Protect Cartilage to Alleviate Osteoarthritis

AbstractOsteoarthritis (OA), characterized by progressive cartilage degeneration and chronic joint pain, represents a major global health challenge. While intra‐articular drug delivery is a common therapeutic approach, its efficacy is limited by poor drug penetration through the dense cartilage matrix, particularly for hydrophobic compounds. Here, a novel charge‐guided micro/nanocarrier system designed to overcome these delivery challenges is presented. By modifying amylose with glycidyl trimethyl ammonium chloride (GTAC), it is developed positively charged carriers that demonstrate enhanced penetration into the negatively charged cartilage matrix. The hydrophobic Piezo1 inhibitor, Margaric acid (MA), is efficiently encapsulated within the helical cavity of modified amylose through DMSO‐ultrasound treatment, creating Cationic Amylose Micro/Nanocarriers@MA (CAMNC@MA). This system effectively delivers MA to chondrocytes, where Piezo1, a crucial mechanosensor implicated in OA development, can be precisely modulated. These results demonstrate that CAMNC@MA successfully inhibits abnormal mechanical force‐induced Piezo1 activation in chondrocytes, enhances cell survival, reduces matrix degradation, and effectively alleviates OA progression. This innovative drug delivery platform offers a promising strategy for clinical OA treatment by combining enhanced matrix penetration with efficient matrix penetration of hydrophobic therapeutic agents.

AM1241 inhibits chondrocyte inflammation and ECM degradation through the Nrf2/HO-1 and NF-κB pathways and alleviates osteoarthritis in mice

BackgroundThis study aimed to investigate the impact of AM1241 on lipopolysaccharide (LPS)-induced chondrocyte inflammation in mice and its potential mechanism for improving osteoarthritis (OA).MethodsThe OA mice model was established employing the refined Hulth method. The impact of different concentrations of AM1241 on mice chondrocyte activity was detected using CCK-8. Changes in the levels of LPS-induced inflammatory factors and cartilage extracellular matrix (ECM) degradation in chondrocytes were determined by western blot, RT-qPCR, ELISA, and immunofluorescence assays, respectively. The specific action modes and binding sites of AM1241 with NEMO/IκB kinases (IKKs) in the NF-κB pathway and Keap1 protein in the Nrf2 pathway were predicted via molecular docking and molecular dynamics simulation, and the NF-κB and Nrf2 pathways were detected using western blot and immunofluorescence. In vivo, the impact of AM1241 on OA mice was analyzed through safranin-fast green staining, IHC staining, Mankin score, and microCT.ResultsAM1241 inhibited the levels of LPS-induced transforming growth factor-β (TGF-β1), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), matrix metalloproteinase-13 (MMP-13), and a disintegrin and metalloproteinase with thrombospondin motif 5 (ADAMTS-5) and diminished the degradation of type II collagen and Aggrecan. For the mechanism, AM1241 regulated the NF-kB and Nrf2/HO-1 signaling pathways by binding to NEMO/IKKβ and Keap1 target proteins and suppressed the activation of the NF-κB signaling pathway by activating the Nrf2 in chondrocytes. In vivo, AM1241 inhibited bone anabolism, mitigated articular cartilage hyperplasia and wear, and reduced the Mankin score in mice, thereby hindering the development of OA.ConclusionAM1241 inhibited activation of the NF-κB signaling pathway via activating Nrf2. It suppressed the expression of inflammation factors and the degradation of ECM in vitro, and improved OA in mice in vivo, suggesting its potential as an effective drug candidate for the treatment of OA. The remarkable efficacy of AM1241 in alleviating murine OA positions it as a potential therapeutic strategy in the clinical management of OA diseases.

Evaluation of the Effects of HDAC Activity in Hydroxychloroquine Applied Human Primary Chondrocyte and Nucleus Pulposus Cultures.

To evaluate the in vitro effects of hydroxychloroquine (HCQ) on histone deacetylase (HDAC) enzyme activity and interleukin (IL)-6, IL-10, and tumor necrosis factor-alpha (TNF-α) expressions. Primary cell cultures were prepared. Samples that did not receive any medication constituted the control group, while culture samples treated with HCQ served as the study group. The surface morphology of cells and the extracellular matrix (ECM) were evaluated by Giemsa staining and inverted light microscopy. Cell viability, proliferation, and cytotoxicity were determined by 3-(4,5-dimethylthiazol2-yl)-2,5-diphenyltetrazolium-bromide (MTT) analysis. The cultures were simultaneously stained with acridine orange (AO)/propidium iodide (PI) and viewed under fluorescence microscopy. HDAC enzyme activity and IL-6, IL-10, and TNF-α expression were evaluated using commercial enzyme-linked immunosorbent assay kits. The obtained data were analyzed using statistical methods. The alpha significance level was accepted as p < 0.05. HCQ applied to cell cultures at the tested doses and durations showed cytotoxic effects on cell viability, proliferation, and cell or ECM morphology. It increased HDAC activity in chondrocytes and caused a proinflammatory response, indicated by an increase in TNF-α in the cells (p < 0.05). The results of this study emphasized that the cytotoxic effect of HCQ increased HDAC activity; therefore, this proinflammatory response should be taken into consideration in the clinical use of HCQ.

Differential modulation of inflammatory cytokines by recombinant IL-10 in IL-1β and TNF-α ̶ stimulated equine chondrocytes and synoviocytes: impact of washing and timing on cytokine responses

Osteoarthritis (OA) remains a challenging joint disorder necessitating effective anti-inflammatory interventions. In this study, our primary objective was to establish an in vitro protocol that replicates the clinical investigation of anti-inflammatory drugs intended for OA management. Focusing on recombinant IL-10 (r.IL-10) as a potential anti-inflammatory treatment, we designed and implemented two distinct protocols to evaluate the efficacy of r.IL-10 in modulating chondrocyte and synoviocyte inflammation.The experimental design involved sequential stimulation with IL-1β and TNF-α for 24 h, followed by washing (model 1) or not washing (model 2) the cells before r.IL-10 treatment. Samples were collected after 6–24 h of treatment. Cellular responses were evaluated by quantifying gene expression and synthesis of key inflammatory cytokines and proteases.The expression and synthesis of inflammatory cytokines and proteases was significantly affected by washing and treatment time. The expression of IL-1β, TNF-α, IL-8, MMP-13, and ADAMTS5 were effectively reduced in r.IL-10-treated chondrocytes and synoviocytes in model 2 after 24 h, particularly at concentrations of 10 and 20 ng/mL. r.IL-10 treatment significantly increased IL-6 gene expression in chondrocytes at all time points. However, in synoviocytes, IL-6 expression was significantly lower in model 2 after 24 h of r.IL-10 treatment. r.IL-10 treatment significantly decreased IL-1β and TNF-α content in synoviocyte supernatants, particularly in model 2 at concentrations of 10 and 20 ng/mL after 6 and 24 h. r.IL-10 treatment in chondrocytes led to a significant decrease in IL-1β supernatant concentrations in model 2 after 24 h only.This study demonstrated that r.IL-10 treatment effectively reduces key inflammatory markers and matrix metalloproteinase activity in both chondrocytes and synoviocytes, particularly in model 2 where cells were not washed prior to treatment. These findings highlight r.IL-10’s potential as a robust anti-inflammatory agent for OA management and suggest its critical role in developing effective therapeutic strategies for OA.

Cinnamaldehyde-Mediated Suppression of MMP-13, COX-2, and IL-6 Through MAPK and NF-κB Signaling Inhibition in Chondrocytes and Synoviocytes Under Inflammatory Conditions.

Inflammatory disorders encompass a range of conditions, including osteoarthritis (OA), characterized by the body's heightened immune response to diverse stimuli. OA is a prevalent degenerative joint disease characterized by the progressive deterioration of joint cartilage and subchondral bone, leading to pain, limited mobility, and physical disability. Synovitis, the inflammation of the synovial membrane, is increasingly recognized as a critical factor in OA pathogenesis and progression. This study evaluates the therapeutic potential of cinnamaldehyde (CA), a bioactive compound derived from cinnamon, on synovial and articular inflammation in OA. Given CA's established anti-inflammatory, antioxidant, and antibacterial properties, this research explores its specific impact on OA and synovitis. The cytotoxicity of CA was assessed using a CCK-8 assay in human IL-1β pretreated chondrocytes and synoviocytes, which serve as in vitro models of OA and synovitis. The study further examined the effects of CA on the expression of proinflammatory cytokines, including IL-6, COX-2, and TNF-α, utilizing multiple analytical techniques. Additionally, the production of matrix metalloproteinases (MMP-3 and MMP-13) and the activation of the NF-κB signaling pathway, particularly the phosphorylation of p65 (pp65), were investigated. The role of the NF-κB inhibitor 5HPP-33 and its downstream effects on gene expression, including COX-2 and IL-6, as well as the MAPK pathway components (p38, ERK, and JNK), were also explored. An MEK inhibitor (U0126) was employed to assess its downstream impact on COX-2 and IL-6 expressions. The results demonstrated that CA significantly inhibited the expression of proinflammatory cytokines and suppressed NF-κB activation in IL-1β pretreated chondrocytes and synoviocytes. These findings suggest that CA, in a dose-dependent manner, may serve as an effective therapeutic agent for preventing OA and synovitis, offering valuable insights into its potential role in managing synovial inflammation and OA.

Design of tunable hyaluronic acid and O′-carboxymethyl chitosan formulations for the minimally invasive delivery of multifunctional therapies targeting rheumatoid arthritis

The development of injectable, dual-component formulations based on natural-based polysaccharides is a promising strategy for the localized treatment of rheumatoid arthritis (RA). In the present study, biomimetic formulations consisting of aldehyde-functionalized hyaluronic acid (AHA) and O-carboxymethyl chitosan (OCC) were developed, presenting rapid in situ gelation rates and finely tunable physicochemical properties. These two properties allowed for the controlled delivery of anti-inflammatory, antioxidant, and pro-regenerative agents (i.e., strontium-methotrexate (SrMTX) and europium-tannic acid nanocomplexes (EuTA NCs), making them suitable for application in in vivo RA-models. Biological analyses demonstrated the system's cytocompatibility and its ability to modulate the activity of human articular chondrocytes at the secretome level and scavenge nitric oxide (NO). Moreover, the loaded cargoes not only extended the anti-inflammatory properties of the formulation but also the radiolabeling of EuTA NCs with 68Ga allowed the visualization of the gel by positron emission tomography (PET). Overall, this work presents the design and in vitro evaluation of an easily modulable polymeric system that allows the in situ release of a multifunctional therapy with promising perspectives for RA treatment.

Hydrogel composition and mechanical stiffness of 3D bioprinted cell-loaded scaffolds promote cartilage regeneration

ObjectiveTo investigate the impact of different component ratios and mechanical stiffness of the gelatin-sodium alginate composite hydrogel scaffold, fabricated through 3D bioprinting, on the viability and functionality of chondrocytes.MethodsThree different concentrations of hydrogel, designated as low, medium, and high, were prepared. The rheological properties of the hydrogel were characterized to optimize printing parameters. Subsequently, the printability and shape fidelity of the cell-loaded hydrogel scaffolds were statistically evaluated, and the chondrocyte viability was observed. Dynamic mechanical analysis was conducted to measure the modulus, thereby assessing the scaffold’s stiffness. Following a 21-day culture period, RT-PCR, histological staining, and immunostaining were employed to assess chondrocyte activity, chondrosphere aggregates formation, and cartilage matrix production.ResultsBased on rheological analysis, optimal printing temperatures for each group were determined as 27.8°C, 28.5°C, and 30°C. The optimized printing parameters could ensure the molding effect of the scaffolds on the day of printing, with the actual grid area of the scaffolds was close to the theoretical grid area. And the scaffolds exhibited good cell viability (93.24% ± 0.99%, 92.04% ± 1.49%, and 88.46% ± 1.53%). After 7 days of culture, the medium and high concentration groups showed no significant change in grid area compared to the day of printing (p &amp;gt; 0.05), indicating good morphological fidelity. As the hydrogel’s bicomponent ratio increased, both the storage modulus and loss modulus increased, while the loss factor remained relatively constant. The highest number of chondrocytes-formed chondrosphere aggregates in the medium concentration group was observed by light microscopy. RT-PCR results indicated significantly higher expression levels of chondrogenic genes SOX9, Agg, and Col-II in the low and medium concentration groups compared to the high concentration group (p &amp;lt; 0.05). Histological staining results showed that the middle concentration group formed the highest number of typical cartilage lacunae.ConclusionThe aforementioned results indicate that in 3D bioprinted cell-loaded GA-SA composite hydrogel scaffolds, the scaffolds with the composition ratio (10:3) and mechanical stiffness (∼155 kPa) exhibit sustained morphological fidelity, effectively preserve the hyaline phenotype of chondrocytes, and are more conducive to cartilage regeneration.

Insufficient Mechanical Loading Downregulates Piezo1 in Chondrocytes and Impairs Fracture Healing Through ApoE-Induced Senescence.

Insufficient mechanical loading impairs fracture healing; however, the underlying mechanisms remain unclear. Increasing evidence indicates that Piezo1 plays an important role in fracture healing, although the effect of Piezo1 on the endochondral ossification of chondrocytes has been overlooked. This study reports that mechanical unloading down-regulates the expression of Piezo1 in chondrocytes and leads to fracture nonunion. Single-cell sequencing of calluses revealed that specific deletion of Piezo1 in chondrocytes upregulated the expression of apolipoprotein E (ApoE) in hypertrophic chondrocytes, resulting in delayed cartilage-to-bone transition due to enhanced chondrocyte senescence. Based on these results, an injectable and thermosensitive hydrogel is developed, which released an ApoE antagonist in situ at the fracture site. This hydrogel effectively attenuated chondrocyte senescence and, thus, promoted cartilage-to-bone transition as well as the fracture healing process. Overall, this data provide a new perspective on the activity of chondrocytes in fracture healing and a new direction for the treatment of fracture nonunion caused by insufficient mechanical loading.

Piezo1-driven mechanotransduction as a key regulator of cartilage degradation in early osteoarthritis.

Osteoarthritis (OA) is a prevalent degenerative disease characterized by pain and cartilage damage in its later stages, while early OA is marked by the loss of cartilage's mechanical function. Recent studies suggest that Piezo1, a mechanotransducer, may contribute to cartilage degradation under abnormal physical stress. This study investigates the mechanism by which Piezo1 mediates the loss of cartilage's mechanical properties. Using rat chondrocytes cultured in a 3D in vitro model, we found that fluid flow-induced physical stress activates constitutively expressed Piezo1, leading to increased catabolic activity and apoptosis, which, in turn, disrupts the matrix structure. Ex vivo cartilage experiments further demonstrated that the mechanical stress-induced loss of cartilage's physical properties (approximately 10% reduction in relaxation modulus) is mediated by Piezo1 and depends on cell viability. Notably, Piezo1 agonists alone did not alter the mechanical behavior of cartilage tissue. In vivo, using an OA rat model induced by anterior cruciate ligament transection, we observed cartilage integrity degradation and loss of mechanical properties, which were partially mitigated by Piezo1 inhibition. RNA sequencing revealed significant modulation of the PI3K signaling and matrix regulation pathways. Collectively, this study demonstrates that Piezo1-mediated catabolic activity in chondrocytes is a key driver of the loss of cartilage's mechanical function during the relaxation phase.

2D MXene Nanosheets with ROS Scavenging Ability Effectively Delay Osteoarthritis Progression.

MXenes nanosheets with high conductivity, hydrophilicity, and excellent reactive oxygen species (ROS) scavenging ability have shown promise in treating various degenerative diseases correlated with abnormal ROS accumulation. Herein, the therapeutic potential of Ti3C2Tx nanosheets, which is the most widely investigated MXene material, in delaying osteoarthritis (OA) progression is demonstrated. In vitro experiments indicate the strong ROS scavenging capacity of Ti3C2Tx nanosheets and their acceptable biocompatibility. Ti3C2Tx nanosheets effectively protect chondrocytes from cell death induced by oxidative stress. In addition, Ti3C2Tx nanosheets demonstrate a prominent anti-inflammatory effect and the ability to restore homeostasis between anabolic activities and catabolic activities in chondrocytes. Furthermore, RNA sequencing reveals the potential mechanism underlying the Ti3C2Tx nanosheet-mediated therapeutic effect. Finally, the in vivo curative effect of Ti3C2Tx nanosheets is verified using a rat OA model. Histological staining and immunohistochemical analyses indicate that Ti3C2Tx nanosheets effectively ameliorate OA progression. Conclusively, the in vitro and in vivo experiments suggest that Ti3C2Tx nanosheets could be a promising and effective option for OA treatment.

The effect of salidroside on the bone and cartilage properties in broilers

Leg disorders frequently occur in fast-growing broiler chickens, constituting severe health and welfare problems. Although salidroside (SAL) promotes osteogenesis and inhibits apoptosis of chondrocytes in rats, it remains to be determined whether SAL can effectively improve bone growth in broilers. The present study was designed to investigate the effects of dietary SAL supplementation on bone and cartilage characteristics in broiler chickens. Ninety-six Arbor Acres broiler chickens were randomly divided into 4 groups: control, low-dose SAL, medium-dose SAL, and high-dose SAL groups. The broiler chickens were raised until 42 d of age, with samples of bone and cartilage collected for biomechanical testing and bone metabolism index detection. The results showed that SAL significantly increased the vertical external diameter, cross-sectional moment of inertia, and cross-sectional area of the femur and tibia. Additionally, SAL enhanced bone mineral density and strength, as evidenced by significant increases in stiffness, Young's modulus, ultimate load, and fracture work of the femur and tibia. Furthermore, SAL influenced the relative content of phosphate, carbonate, and amide I in cortical bone. Moreover, SAL upregulated the expression of osteogenic genes (Collagen-1, RUNX2, BMP2, and ALP) in a dose-dependent manner and maintained the homeostasis of the extracellular matrix (ECM) of chondrocytes. These results indicated that SAL promoted leg health in broilers by improving bone and cartilage quality and enhancing chondrocyte activity.

Relationship between autophagy and NLRP3 inflammasome during articular cartilage degradation in oestrogen-deficient rats with streptozotocin-induced diabetes

BackgroundEstrogen deficiency and Diabetes mellitus (DM) cause joint tissue deterioration, although the mechanisms are uncertain. This study evaluated the immunoexpression of autophagy and NLRP3-inflammasome markers, in rat articular cartilage with estrogen deficiency and DM. MethodsTwenty rats were sham-operated (SHAM) or ovariectomized (OVX) and equally allocated into four groups: SHAM and OVX groups administered with vehicle solution; SHAM and OVX groups treated with 60 mg/kg/body weight of streptozotocin, intraperitoneally, to induce DM (SHAM-DM and OVX-DM groups). After seven weeks, the rats were euthanized, and their joint knees were processed for paraffin embedding. Sections were stained with haematoxylin-eosin, toluidine blue, safranin-O/fast-green or subjected to picrosirius-red-polarisation method; immunohistochemistry to detect beclin-1 and microtubule-associated protein 1B-light chain 3 (autophagy markers), NLRP3 and interleukin-1β (IL-1β) (inflammasome activation markers), along with matrix metalloproteinase-9 (MMP-9), Nuclear factor-kappa B (NFκB), and Vascular endothelial growth factor A (VEGF-A) were performed. ResultsDeterioration of articular cartilage and subchondral bone were greater in SHAM-DM and OVX-DM groups. Higher percentages of immunolabeled chondrocytes to NLRP3, IL-1β, MMP-9, NFκB, and VEGF-A, as well as lower percentages of chondrocytes immunolabeled to autophagy markers, were noticed in estrogen-deficient and diabetic groups. These differences were greater in the OVX-DM group. Percentages of immunolabeled chondrocytes showed negative correlation between autophagy markers v.s IL-1β, NLRP-3, MMP-9, NFκB, and VEGF-A, along with positive correlation between VEGF-A vs. MMP-9, NFκB, IL-1β, and NLRP3, and MMP-9 vs. NFκB. ConclusionsIn conclusion, autophagy reduction and NLRP3 inflammasome activation in chondrocytes may be implicated in articular cartilage degradation, under estrogen-deficient and DM conditions. Moreover, the combination of estrogen deficiency and DM may potentiate those effects.

Retraction Note: Fibroblast growth factor receptor 1 is principally responsible for fibroblast growth factor 2-induced catabolic activities in human articular chondrocytes

Retraction Note: Fibroblast growth factor receptor 1 is principally responsible for fibroblast growth factor 2-induced catabolic activities in human articular chondrocytes

Bushen Huoxue decotion-containing serum prevents chondrocyte pyroptosis in a m6A-dependent manner in facet joint osteoarthritis

BackgroundFacet joint osteoarthritis (FJOA) is a common lumbar osteoarthritis characterized by degeneration of small joint cartilage. Bushen Huoxue decotion (BSHXD) has good therapeutic effects on OA. Our work aimed to further probe the pharmacological effects of BSHXD-containing serum (BSHXD-CS) on FJOA and define underlying the mechanisms invovled. MethodsTo establish a FJOA cell model, primary rat chondrocytes were treated with LPS. The mRNA and protein expressions were assessed using qRT-PCR and western blot, respectively. The secretion levels of pro-inflammatory cytokines were measured by ELISA. Cell viability was determined by CCK8 assay. The global m6A level was detected by the kit, and NLRP3 mRNA m6A level was determined by Me-RIP assay. The molecular interactions were analyzed by RIP and RNA pull-down assays. ResultsBSHXD-CS treatment relieved LPS-induced cell injury, inflammation, NLRP3 inflammasome and pyroptosis in chondrocytes (all p < 0.05). LPS-induced NLRP3 upregulation in chondrocytes was related to its high m6A modification level (p < 0.05). It was also observed that BSHXD-CS reduced LPS-induced m6A modification in chondrocytes via repressing STAT3 (all p < 0.05), suggesting BSHXD-CS could repress NLRP3 expression via m6A-dependent manner. Moreover, DAA, a m6A specific inhibitor, was proved to strengthen the protectively roles of BSHXD-CS on LPS-challenged pytoptosis (all p < 0.05). ConclusionBSHXD-CS inhibited NLRP3 inflammasome activation and pyroptosis in chondrocytes to repress OA progression by reducing RNA m6A modification.

The chondrocyte "mechanome": Activation of the mechanosensitive ion channels TRPV4 and PIEZO1 drives unique transcriptional signatures.

The mechanosensitive ion channels Transient Receptor Potential Vanilloid 4 (TRPV4) and PIEZO1 transduce physiologic and supraphysiologic magnitudes of mechanical signals in the chondrocyte, respectively. TRPV4 activation promotes chondrogenesis, while PIEZO1 activation by supraphysiologic deformations drives cell death. The mechanisms by which activation of these channels discretely drives changes in gene expression to alter cell behavior remain to be determined. To date, no studies have contrasted the transcriptomic response to activation of these channels nor has any published data attempted to correlate these transcriptomes to alterations in cellular function. This study used RNA sequencing to comprehensively investigate the transcriptomes associated with activation of TRPV4 or PIEZO1, revealing that TRPV4 and PIEZO drive distinct transcriptomes and also exhibit unique co-regulated clusters of genes. Notably, activation of PIEZO1 through supraphysiologic deformation induced a transient inflammatory profile that overlapped with the interleukin (IL)-1-responsive transcriptome and contained genes associated with cartilage degradation and osteoarthritis progression. However, both TRPV4 and PIEZO1 were also shown to elicit anabolic effects. PIEZO1 expression promoted a pro-chondrogenic transcriptome under unloaded conditions, and daily treatment with PIEZO1 agonist Yoda1 significantly increased sulfated glycosaminoglycan deposition invitro. These findings emphasize the presence of a broad "mechanome" with distinct effects of TRPV4 and PIEZO1 activation in chondrocytes, suggesting complex roles for PIEZO1 in both the physiologic and pathologic responses of chondrocytes. The identification of transcriptomic profiles unique to or shared by PIEZO1 and TRPV4 (distinct from IL-1-induced inflammation) could inform future therapeutic designs targeting these channels for the management and treatment of osteoarthritis.

CircRELL1 promotes osteoarthritis progression by regulating miR-200c-3p

BackgroundThere is a growing body of evidence indicating a potential association between circular RNA and the pathogenesis of human osteoarthritis (OA). Nevertheless, the precise extent of their involvement in OA remains largely unexplored. Hence, the objective of this investigation is to elucidate the function of Circular (Circ) RELL1 in the context of OA. Methods24 OA tissue samples and 11 normal tissue samples were collected. The inflammatory OA-like conditions were established by Destabilized Medial Meniscus (DMM) operation in mice and LPS-induced C28/I2 cells. OA severity and articular cartilage degradation were assessed by Safranin-O staining, hematoxylin-eosin (H&E) staining, and International Society for Osteoarthritis Research (OARSI) criteria. CircRELL1, miR-200c-3p, and TCF4 were measured by RT-qPCR and Immunoblot. The cell viability and apoptosis rate were measured by MTT and flow cytometry, respectively. The levels of cytokines interleukin (IL)-1β, IL-6, and TNF-α were determined by ELISA. Apoptosis-associated proteins (cleaved caspase-3, Bax, and Bcl-2) and extracellular matrix (ECM) degradation-associated proteins (MMP13, collagen II, and Aggrecan) were detected by Immunoblot. The interaction between miR-200c-3p and circRELL1 or TCF4 was verified by dual luciferase reporter assay and RIP assay. ResultsCircRELL1 expression was upregulated in OA patients, and the results were consistent in DMM mice and LPS-treated C28/I2 cells. Silencing circRELL1 improved cartilage injury caused by DMM and contributed to a lower OARSI score. Silencing CircRELL1 increased the activity of OA chondrocytes in vivo and in vitro and inhibited cellular inflammatory responses and ECM degradation. In terms of mechanism, circRELL1 functioned by targeting miR-200c-3p, leading to the suppression of inflammatory factor production, cell apoptosis, and ECM degradation, thus inhibiting the progression of OA. ConclusionCircRELL1 may promote the progression of OA by regulating the miR-200c-3p.

The protective effects of orexin-A in alleviating cell senescence against interleukin-1β (IL-1β) in chondrocytes.

Osteoarthritis (OA) is one of the most important causes of global disability, and dysfunction of chondrocytes is an important risk factor. The treatment of OA is still a challenge. Orexin-A is a hypothalamic peptide, and its effects in OA are unknown. In this study, we found that exposure to interleukin-1β (IL-1β) reduced the expression of orexin-2R, the receptor of orexin-A in TC-28a2 chondrocytes. Importantly, the senescence-associated β-galactosidase (SA-β-gal) staining assay demonstrated that orexin-A treatment ameliorates IL-1β-induced cellular senescence. Importantly, the presence of IL-1β significantly reduced the telomerase activity of TC-28a2 chondrocytes, which was rescued by orexin-A. We also found that orexin-A prevented IL-1β-induced increase in the levels of Acetyl-p53 and the expression of p21. It is shown that orexin-A mitigates IL-1β-induced reduction of sirtuin 3 (SIRT3). Silencing of SIRT3 abolished the protective effects of orexin-A against IL-1β-induced cellular senescence. These results imply that orexin-A might serve as a promising therapeutic agent for OA.

Luteolin regulating synthesis and catabolism of osteoarthritis chondrocytes via activating autophagy

Osteoarthritis (OA) is a prevalent bone and joint disease characterized by degeneration. The dysregulation between chondrocyte synthesis and breakdown is a key factor in OA development. Targeting the degenerative changes in cartilage tissue degradation could be a potential treatment approach for OA. Previous research has established a strong link between autophagy and the regulation of chondrocyte functions. Activating autophagy has shown promise in mitigating cartilage tissue degeneration. Currently, osteoarthritis treatment primarily focuses on symptom management, as there is no definitive medication to stop disease progression. Previous studies have demonstrated that luteolin, a flavonoid present in Chinese herbal medicine, can activate autophagy and reduce the expression of MMP1 and ADAMTS-5. This study utilized an in vitro osteoarthritis model with chondrocytes stimulated by IL-1β, treated with varying concentrations of luteolin. Treatment with luteolin notably increased the levels of synthesis factors Aggrecan and Collagen II, while decreasing the levels of decomposition factors MMP-1 and ADAMTS-5. Moreover, inhibition of autophagy by Chloroquine reversed the imbalances in chondrocyte activities induced by IL-1β. In an in vivo model of knee osteoarthritis induced by medial meniscal instability (DMM), luteolin was administered as a therapeutic regimen. After 12 weeks, knee cartilage tissues from mice were analyzed. Immunofluorescence and immunohistochemical staining revealed a decrease in P62 expression and an increase in Beclin-1 in the cartilage tissues. Additionally, cartilage wear in the knee joints of mice was alleviated by safranin O and fast green staining. Our study findings underscore the significant role of luteolin in effectively rebalancing chondrocyte activities disrupted by IL-1β. Our results strongly indicate that luteolin has the potential to be developed as a novel therapeutic agent for the treatment of osteoarthritis, offering promising prospects for future drug development.

Hsa_circ_0007482 Promotes Proliferation and Differentiation of Chondrocytes in Knee Osteoarthritis.

Knee osteoarthritis (KOA) is a complex degenerative joint disease and a major cause of joint dysfunction. This study aimed to explore the function of hsa_circ_0007482 on inflammation, proliferation, differentiation, and apoptosis in KOA. Real-time quantitative polymerase chain reaction (PCR) was performed to detect the expression of circ_0007482, inflammatory factors, and differentiation-related molecules in KOA chondrocytes and interleukin (IL)-1β-stimulated chondrocytes. The correlation between the circ_0007482 expression and inflammatory factors was analyzed by the Pearson method. KOA cell model was established using IL-1β for 24 hours. The proliferation activity of chondrocytes was evaluated by CCK-8 assay, and cell apoptosis rate was assessed by flow cytometry. The downstream miRNA of circ_0007482 was validated using dual-luciferase reporter assay. The circ_0007482 expression was elevated in both KOA cartilage tissues and IL-1β-treated chondrocytes and positively correlated with inflammatory factors expression. In comparison to the control group, IL-1β treatment diminished chondrocyte proliferation abilities and increased cell apoptosis and inflammatory factors IL-6, IL-8, and tumor necrosis factor (TNF)-α mRNA expression. Inhibition of circ_0007482 partially improved IL-1β-induced inflammatory reaction. Circ_0007482 could negatively regulate the expression of miR-558. Interfering of circ_0007482 might partially promote cell proliferation and differentiation, while inhibit cell apoptosis to improve joint injury by regulating miR-558 in IL-1β-treated chondrocyte cell model.

Dietary fiber may benefit chondrocyte activity maintenance.

The understanding of the link between the gut-bone axis is growing yearly, but the mechanisms involved are not yet clear. Our study analyzed the role of Sestrin2 (SESN2)pathway in the gut-bone axis. We established an osteoarthritis (OA) model in Sprague-Dawley (SD) rats using the anterior cruciate ligament transection (ACLT) procedure, followed by a dietary intervention with varying levels of dietary fiber content for 8 weeks. By 16S rRNA sequencing of the gut microbiota, we found that high dietary fiber (HDF) intake could significantly increase the Bacillota-dominant gut microbiota. Meanwhile, enzyme linked immunosorbent assay (ELISA) and histological analysis showed that intervention with HDF could reduce the degree of bone and joint lesions and inflammation. We hypothesize that HDF increased the dominant flora of Bacillota, up-regulated the expression of SESN2 in knee joint, and reduced gut permeability, thereby reducing systemic inflammatory response and the degree of bone and joint lesions. Therefore, the present study confirms that changes in gut microbiota induced by increased dietary fiber intake delayed the onset of OA by promoting up-regulation of SESN2 expression at the knee joint to maintain chondrocyte activity and reduce synovial inflammation.